DE102004006998B4 - ion detector - Google Patents

Abstract

Inner detector for use in a mass spectrometer, comprising:
a microchannel plate (8) wherein, in use, ions (12) are received on an entrance surface of the microchannel plate (8) and electrons (16) are emitted from an exit surface of the microchannel plate (8), the exit surface having a first surface, and a detection device (9) formed with a zigzag pair of microchannel plates (10, 11) and having a detection surface on which at least some of the electrons (16) emitted by the microchannel plate (8) impinge, the detection surface having a second surface is larger than the first surface and between the microchannel plate (8) and the detection device (9) electrodes (17) are provided, by means of which an electric field is generated, so that the microchannel plate (8) emitted electrons are diverged to the detection surface ,

Description

The The present invention relates to interior detectors for use in a mass spectrometer, mass spectrometer, and method of Detecting particles, in particular ions.

From the date of the first priority date of the present application (February 13, 2000) US 2003/0111597 A1 is a multi-anode detector with an increased dynamic range for time-of-flight mass spectrometers with counting data acquisition known.

Under This document describes a microchannel plate which spaced apart from a detector, wherein the detector greater than the microchannel plate is formed.

The DE 692 00 648 T2 concerns, inter alia, a method of limiting feedback in a wafer tube image intensifier having an input window with a photocathode, an output window with a light screen, and a microchannel plate between the input window and the output window. In this case, electrons are generated at the photocathode in response to an image impinging on the input window. A generation of photons based on electrons is not the subject of this document.

The US 5,693,946 A describes a photon imaging.

Especially is here on the size of detectors in terms of MCP's received.

The DE 693 28 818 T2 describes a hybrid photomultiplier tube with high sensitivity. In particular, the photomultiplier tube described therein comprises one or more electrodes for focusing the electrons on the detector.

The DE 43 22 104 A1 finally describes a detector for a time-of-flight mass spectrometer with low flight time errors. If ions traverse inhomogeneous fields in the detector of a time-of-flight mass spectrometer, it may be the case that different trajectories require different times from the entrance window to ion-electron conversion. The document describes a reduction of these flight time errors by suitable deformation of the conversion surface.

None This document relates to increasing the temporal resolving power of a Particle or inner detector by defocusing measures or effects.

One known interior detector for a mass spectrometer is a microchannel plate detector ("MCP detector"). A microchannel plate consists of a two-dimensional periodic arrangement of glass capillaries (Channels) with a very small diameter, which fused together are and become a thin one Plate are cut. The microchannel plate detector can have several Millions of channels each channel being an independent electron multiplier acts. An ion entering a channel interacts with the channel Wall of the channel and causes secondary electrons be submitted by this. The secondary electrons are then through an electric field created by applying a voltage difference across the Microchannel plate over her entire length is maintained accelerated to an exit surface of the microchannel plate.

The Secondary electrons generated by an incident ion are parabolic Trajectories along a canal until it hits the wall of the canal meet and cause more Generated secondary electrons or delivered.

This Process of Generation of secondary electrons is repeated along the channel, so that a cascade of several a thousand secondary electrons may result from the invasion of a single ion. The secondary electrons then emerge from the exit surface the microchannel plate and are detected.

It is known to provide two microchannel plates which are sandwiched together and operated in series. The two microchannel plates are maintained at a high gain so that a single ion arriving at the first microchannel plate can cause a pulse of, for example, 10 ⁷ or more electrons to be emitted from the exit surface of the rearmost of the two microchannel plates. The two microchannel plates can be arranged in a zigzag shape, wherein the microchannel plates are arranged opposite one another, so that the channels in a microchannel plate under a Angles are arranged to the channels of the other microchannel plate. This arrangement helps to suppress internal feedback that may otherwise result in damage.

The Requirements for an electron multiplier in a time-of-flight mass spectrometer are particularly strict. The electron multiplier should have a minimum Generate broadening of spectral peaks and a linear response provide both at low and at high ion arrival rates, while allows becomes that single ion events be clearly distinguished from electronic noise.

To meet these criteria, the output of an electron multiplier due to a single ion arrival event should have a minimal time spread and the pulse height distribution of the electrons should be as narrow as possible. In addition, the gain of the electron multiplier should preferably be on the order of 10 ⁶ or greater, to allow single ion events to be easily distinguished from electronic noise.

For ion counting applications microchannel plate ion detectors have so far been the most satisfactory Characteristics provided with respect to these criteria. Under optimal operating conditions, the dynamic range of However, microchannel plate ion detectors may be limited.

Under the condition of a high gain of, for example, 10 ⁶ -10 ⁷ , the output current of a single channel of a microchannel plate is space charge saturated, resulting in narrow pulse height distributions approaching Gaussian distributions. Narrow pulse height distributions are advantageous for ion counting devices which use time-to-digital converters ("TDC") because they allow the majority of single ion events to be distinguished from electronic noise. Narrow pulse height distributions are also advantageous for use with analog-to-digital converters ("ADC") because they allow accurate quantization at low count rates and improved dynamic range.

Of the maximum output current of a microchannel plate detector is by the recovery time the individual channels after irradiation and the total number of irradiated per unit time channels limited. Ions pointing to a microchannel plate detector in one Lateral acceleration Time of Flight mass fall, irradiate a discrete area of the microchannel plate detector. Accordingly, ions fall regardless of the area of the Microchannel plate, only a part of the total number of available microchannels. If therefore great interior currents fall on the microchannel plate ion detector or at certain output currents in equilibrium a considerable part of the channels after irradiation is not complete recovered, the overall gain becomes of the microchannel plate ion detector reduced. In particular, the last 20% of the length of the channels in the last amplification stage of the microchannel plate ion detector first through this saturation point limited. this leads to to that one nonlinearity caused the response of the inner detector, resulting in a quantitative analysis to inaccurate isotope ratio determinations and inaccurate Mass measurements leads.

Around to increase the maximum input event rate at which the interior detector can cope before the saturation could occur the reinforcement The microchannel plate can be theoretically reduced. Reducing the reinforcement would, however a broadening of the pulse height distribution cause and the pulse height distribution to a lower intensity shift, resulting in a deterioration of the ability of the interior detector, all single ion arrivals above the electronic To detect noise threshold results.

wobei D der Durchmesser der Mikrokanalplatte ist und p der Kanalabstand von Mitte zu Mitte (die Kanalteilung) ist.The limitations of a conventional microchannel plate ion detector will be considered in more detail below. In particular, two zigzag paired microchannel plates are considered. After an electron cloud has emerged from a single channel in a microchannel plate, the charge within the channel walls must be restored. For a circular microchannel plate, the number N of channels is given by:

where D is the diameter of the microchannel plate and p is the channel spacing from center to center (the channel split).

For a 25 mm diameter circular microchannel plate having 10 μm diameter channels and a 12 μm channel pitch, the total number N of channels is 3.9 × 10 ⁶ . Typically, the total resistance of such a single microchannel plate 10 is ⁸ Ω. Therefore, the resistance R _{c of} a single channel of the microchannel plate is about 3.9 × 10 ¹⁴ Ω.

genähert werden, wobei C die Kapazität in Farad ist, ε die Dielektrizitätskonstante von Glas ist (in etwa 8,3 F/m), ε₀ die Permittivität des Vakuums ist (8,854 × 10^-12), S die Fläche der Mikrokanalplatte ist und d die Dicke der Mikrokanalplatte ist.The total capacity of a single microchannel plate can be approximated by considering it as a pair of parallel metal plates separated by a relatively thin glass plate. The total capacity C can through

where C is the capacitance in farads, ε is the dielectric constant of glass (about 8.3 F / m), ε _{0 is} the permittivity of the vacuum (8.854 x 10 ^-12 ), S is the area of the microchannel plate, and d is the thickness of the microchannel plate.

Therefore, if the thickness d of the microchannel plate is assumed to be 0.46 mm, the total capacitance C of a single microchannel plate 78 is pF and the capacitance C _c for each channel of the microchannel plate is 2 × 10 ^-17 F.

The time constant τ for the recovery of a single channel in the microchannel plate after an internal event is through C c R c = τ given.

In this example, the time constant τ for a single channel is 7.8 ms. For a pair of microchannel plates in a zigzag pair, a primary ion event at the entrance surface of the first microchannel plate typically causes secondary electrons to irradiate about ten channels at the entrance surface of the second microchannel plate. Assuming that the first and second microchannel plates are identical, the maximum ion entry event rate E at the first microchannel plate is given by:

Accordingly, the maximum ion entrance event rate E _max at the first microchannel plate, which is allowable without a significant overall gain loss of the entire interior detector, is approximately: e Max = e 10

In the example given above, the maximum entry event rate is E _max 5 × 10 ⁶ event. At a mean amplification of 5 × 10 ⁶ , this corresponds to a maximum output current I _max of 4 × 10 ^-6 A.

Transverse acceleration Time of Flight mass spectrometers usually have very large internal currents at sample repetition rates of tens of kHz. Under these conditions, the internal current entering the microchannel plate approaches a steady DC current. The gain of the microchannel plate is constant until the output current of the microchannel plate exceeds about 10% of the available current flowing through the microchannel plate, ie, the strip current. In the example given above, the maximum output current I _{max is} 10 ^-6 A when 1000 V is maintained across the microchannel plate.

Several methods have been developed to overcome this limitation of the maximum output current of a microchannel plate. For example, by reducing the resistance of the microchannel plate, the channel recovery time constant τ is reduced and the available stripping current is increased, thereby increasing the maximum output current of the microchannel plate. However, there are also practical limitations. The negative temperature coefficient of resistance of the channel walls in the microchannel plate eventually leads to thermal instability as the resistance of the microchannel plate is reduced. This causes heating of the microchannel plate, which can lead to an internal feedback, resulting in a thermal runaway, which can lead to a local melting of the glass of the microchannel plate. The mechanism by which heat is removed from a microchannel plate is predominantly by radiation from the surface of the microchannel plate, and the heat dissipation is therefore directly proportional to the exposed the surface of the microchannel plate.

It has been experimentally found that it is not practical to drive microchannel plates at heat generation levels above 0.01 W / cm ² . For a circular microchannel plate with a diameter of 33 mm, which is held at a bias voltage of 1000 V, this heat generation rate corresponds to a microchannel plate with a total resistance of about 10 ⁷ Ω. It should be noted that due to this limitation of the total resistance of the microchannel plate, the maximum output current of the microchannel plate can not be increased simply by reducing the diameter of the channels in the microchannel plate to increase the number of channels available per unit area. For example, a circular microchannel plate having a diameter of 33 mm corresponding to an active diameter of 25 mm, the channels having a diameter of 10 microns and a channel pitch of 12 microns, a total of 3.9 × 10 ⁶ channels. If the microchannel plate has a total resistance of 10 ⁷ Ω, the resistance of each channel is 3.9 × 10 ¹³ Ω. For a circular microchannel plate of the same diameter, same total resistance, a reduced channel diameter of 5 μm, and a reduced channel pitch of 6 μm, the total number of channels is 1.6 × 10 ⁷ . Accordingly, each channel now has an increased resistance of 1.6 × 10 ¹⁴ Ω. In this example, it is shown that by reducing the diameter and the pitch of the channels in the microchannel plate, the total number of channels is increased by a factor of about 4 times. However, the resistance per channel and thus the time constant for the recovery of a single channel τ is also increased by the same factor. Therefore, no overall gain of the maximum output current of the microchannel plate is obtained.

One direct cooling allows the microchannel plate Theoretically, the use of microchannel plates with a very low resistance. However, such direct cooling is in most Situations not practicable executable.

One another method to increase the maximum output current of the microchannel plate is the incoming inner beam over a relatively large microchannel plate or over the entrance area to disperse multiple microchannel plates. By this dispersion of the inner beam, the number of available channels is increased, without the characteristics of the individual channels changed in the microchannel plate become. The total resistance of the microchannel plate ion detector is therefore reduced, resulting in a higher available strip current and thus to a higher one Insertion level of channel saturation leads.

at this arrangement, the microchannel plate or can Micro channel plates under relatively stable Conditions are operated because of the radiation cooling of the Microchannel plate or microchannel plates available surface too is enlarged. The intentional divergence of the inner beam as it approaches the inner detector running, However, in many situations, depending on the geometry and the Size of one individual mass spectrometer, impractical. Furthermore, have to Divergence of the inner beam electric fields in the range of the mass spectrometer upstream be provided of the indoor detector. This is particularly disadvantageous in a time-of-flight mass spectrometer where the range upstream of the Interior detector is a drift area, because the insertion of an electric Felds in the drift area the resolution and the mass measurement accuracy of the ion detection system. In addition, the changed electric field conditions when negative and positive ions are detected. Therefore Divergence of the inner beam is not practical for this problem applicable solution.

It is therefore desirable an improved detector for to provide a mass spectrometer.

To For this purpose, the present invention provides an interior detector for use in a mass spectrometer with the features of Patent claim 1, an interior detector for use in a mass spectrometer with the features of claim 23, an interior detector for use in a mass spectrometer having the features of claim 24, a mass spectrometer with a correspondingly formed inner detector according to claim 25, a method for detecting ions with the steps of Patent claim 29, a method for detecting particles with the steps of claim 30 and a method of detecting of particles with the steps of claim 31 available.

According to a first aspect of the present invention, an interior detector for use in a mass spectrometer is proposed. The detector includes a microchannel plate, wherein in use particles are received on an entrance surface of the microchannel plate and electrons are emitted from an exit surface of the microchannel plate, the exit surface defining a first surface th range. The detector further comprises a detection device having a detection surface adapted to receive, in use, at least some of the electrons emitted by the microchannel plate, the detection surface having a second area. The second area is considerably larger than the first area.

According to one another preferred embodiment is the second area by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45 %, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% larger than the first area. Preferably, the second surface is by at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than the first area.

According to one Another aspect of the present invention is a detector for use provided in a mass spectrometer, the detector having a Microchannel plate, wherein in use particles an entrance area the microchannel plate are received and electrons from an exit surface of the Microchannel plate are emitted, with an average of x electrons per unit area from the exit surface be delivered. The detector further comprises a detection device with a detection surface on which is set up to use at least some to receive the electrons generated by the microchannel plate, where on average y receive electrons per unit area on the detection surface and where x> y is.

Preferably average x electrons per unit area and per unit time from the exit surface given and average y electrons per unit area and per unit of time received by the detection surface.

According to one preferred embodiment x is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 % or 100% greater than y. Preferably, x is at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than the first area.

Preferably are the particles received by the detector ions, photons or Electrons.

According to one preferred embodiment be the of the exit surface the microchannel plate emitted electrons in an area with delivered an electric field. The detector can be one or more Having electrodes which are arranged so that between the microchannel plate and providing the detection device with an electric field is. The one or more electrodes may include one or more annular electrodes, one or more single-lens arrangements with three or more electrodes, one or more segmented rod sets, one or more tubular electrodes and / or one or more quadrupole, hexapole, octapole rod sets or sets of higher Have order. The one or more electrodes may alternatively or additionally several electrodes with openings, which have substantially the same area and of which Electrons are transmitted in use, and / or more Electrodes with openings, which become progressively smaller or larger towards the detection device and from which electrons are transmitted in use, lock in.

According to the preferred embodiment becomes the exit surface the microchannel plate held at a first potential and the detection area the detection device held at a second potential. The second potential is preferably more positive than the first potential. The potential difference between the surface of the detection device and the exit surface the microchannel plate can be selected from the following group: 0-50V, 50-100V, 100-150V, 150-200V, 200-250V, 250-300V, 300-350V, 350-400 V, 400-450V, 450-500V, 500-550V, 550-600V, 600-650V, 650-700 V, 700-750 V, 750-800 V, 800-850 V, 850-900 V, 900-950 V, 950-1000 V, 1.0-1.5 kV, 1.5-2.0 kV, 2.0-2.5 kV,> 2.5 kV and <10 kV.

According to one another embodiment can the one or more electrodes between the microchannel plate and the detection surface are arranged on a third and / or a fourth and / or a fifth Potential to be kept. The third and / or the fourth and / or the fifth Potential can essentially the same as the first and / or the second potential, be more positive than the first and / or the second potential and / or be more negative than the first and / or the second potential. Preferably becomes the potential difference between the third and / or the fourth and / or the fifth Potential and the first and / or the second potential from the following group selected: 0-50V, 50-100V, 100-150V, 150-200 V, 200-250V, 250-300V, 300-350V, 350-400V, 400-450V, 450-500 V, 500-550 V, 550-600 V, 600-650 V, 650-700 V, 700-750 V, 750-800 V, 800-850 V, 850-900 V, 900-950 V, 950-1000 V, 1.0-1.5 kV, 1.5-2.0 kV, 2.0-2.5 kV,> 2.5 kV and <10 kV.

According to one embodiment are the third and / or the fourth and / or the fifth potential between the first and / or the second potential.

Preferably the detector further comprises a grid electrode interposed between the microchannel plate and the detection device is arranged. The grid electrode may be substantially hemispherical or on other way nonplanar.

According to one embodiment the detection device has a single detection area on. The single detection area may be an electron multiplier, a scintillator, a photomultiplier tube or have one or more microchannel plates. According to one preferred embodiment the detection device has one or more microchannel plates on when using over a first number of channels at least some of the second number of channels of the upstream delivered the detection device arranged microchannel plate Receive electrons, with the first number of channels significantly is larger as the second number of channels.

According to one another preferred embodiment the detection device has a first detection area and at least a second separate detection area. The second Detection area can be spaced from the first detection area be. The first and the second detection area can be in essentially the same detection areas or, alternatively, considerably have different detection surfaces.

According to one embodiment is the area of the first detection range by a percentage p greater than the area of the second detection area, where p is from the following group selected is: <10%, 10-20 %, 20-30%, 30-40 %, 40-50%, 50-60%, 60-70%, 70-80 %, 80-90% and> 90 %.

Preferably In use, the number of electrons received by the first detection surface is by a percentage q greater than the number of electrons received by the second detection surface, where q is selected from the following group: <10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70 %, 70-80%, 80-90 % and> 90%.

A preferred embodiment has at least one electrode, which is arranged so that in the Use at least some emitted from the microchannel plate Electrons are guided to the first detection area and / or at least some of the electrons emitted by the microchannel plate to the second Detection area out become. The first and / or the second detection area may include one or more microchannel plates, an electron multiplier, a scintillator or a photomultiplier tube. Preferably, the detection device has at least one zigzag-shaped Pair of microchannel plates on.

Of the Detector may further comprise at least one collector plate, which is set up to use at least some of the generated or emitted electrons to the detection device receive. The at least one collector plate may be shaped that one temporal broadening of the time of flight of the detection device incident electrons is at least partially compensated. Alternatively or additionally the detection device can be shaped so that a temporal Widening of the time of flight of the incident on the detection device At least partially compensated electrons. Preferably one or more electrodes also arranged so that a temporal Widening of the time of flight of the incident on the detection device At least partially compensated electrons. The one or the multiple electrodes can be set up so that from different electrons emitted by different sections of the microchannel plate accelerated or delayed or the electrons are accelerated by different amounts be to the temporal broadening of the time of flight of the electrons to compensate. For example, those from the center of the microchannel plate emitted electrons with respect to those of the other sections the microchannel plate emitted electrons are accelerated.

In another aspect, the invention provides a detector for use in a mass spectrometer, wherein the detector comprises a microchannel plate, wherein in use particles are received at an entrance surface of the microchannel plate and electrons are emitted from an exit surface of the microchannel plate, the exit surface being a first Has surface. The detector further comprises a detection device having a detection surface with a second surface and a first device disposed between the micro-channel plate and the detection device. The first device is arranged to receive at least some of the electrons emitted from the exit surface of the microchannel plate and to generate photons. A second device is between the first before direction and the detection device arranged. The second device is arranged to receive at least some of the photons generated by the first device and to emit electrons. The detection surface is adapted to receive at least some of the electrons generated by the second device, the second surface being substantially larger than the first surface.

According to one preferred embodiment is the second area by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45 %, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% larger than the first area. Preferably, the second surface is by at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than the first area.

According to one Another aspect of the present invention is a detector for Use provided in a mass spectrometer, wherein the detector a microchannel plate, wherein in use particles at an entrance area the microchannel plate are received and electrons from an exit surface of the Microchannel plate are emitted, with an average of x electrons per unit area from the exit surface be delivered. The detector further comprises a detection device with a detection area, the one second surface and a first device located between the microchannel plate and the detection device is arranged on. The first device is for that arranged, at least some of the discharged from the exit surface Receive electrons and generate photons. A second device is between the first device and the detection device arranged and for that arranged, at least some of the generated by the first device To receive photons and release electrons. The detection surface is set up for at least some of the electrons generated by the second device to receive, and she receives average y electrons per unit area, where x> y.

According to the preferred embodiment x is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 % or 100% greater than y. Preferably, x is at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than y.

According to one In another aspect, the present invention provides a detector for Use in a mass spectrometer, wherein the detector has a Microchannel plate, wherein in use particles an entrance area the microchannel plate are received and electrons from an exit surface of the Micro channel plate are discharged, the exit surface a first surface having. The detector further includes a detection device a detection surface, the one second surface and a first device located between the microchannel plate and the detection device is arranged on. The first device is for that arranged, at least some of the exit surface of the Microchannel plate emitted electrons to receive and photons to create. The detection area is for that arranged, at least some of the generated by the first device To receive photons. The second area is considerably larger than the first area.

The second surface is preferably at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% greater than the first area and can be at least 150%, 200%, 250%, 300%, 350%, 400%, 450 % or 500% larger than the first area be.

According to one In another aspect, the present invention provides a detector for Use in a mass spectrometer, which is a microchannel plate wherein, in use, particles at an entrance surface of the Microchannel plate are received and electrons from an exit surface of the Microchannel plate are emitted, with an average of x electrons per unit area from the exit surface be delivered. The detector further comprises a detection device and a first device disposed between the microchannel plate and the detection device is arranged. The first device is set up at least some of the output from the exit surface of the microchannel plate Receive electrons and generate photons. The detection device is for that arranged, at least some of the generated by the first device Receiving and receiving photons an average of z photons per unit area, where x> z.

According to one preferred embodiment x is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 % or 100% greater than z. Preferably, x is at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than z.

According to one preferred embodiment the photons are UV photons.

According to one In another aspect, the present invention provides a mass spectrometer with a detector as described above.

Preferably the detector forms part of a time-of-flight mass analyzer. According to one embodiment the mass spectrometer further has one connected to the detector Analog-to-digital converter ("ADC") and / or a associated with the detector time-to-digital converter ("TDC").

The Mass spectrometer may further have an internal source, which selected from the group is, which consists of the following: an electrospray ionization ion source ("ESI ion source"), an atmospheric pressure ionization ion source ("API ion source"), an atmospheric pressure ion source with chemical ionization ("APCI ion source"), an atmospheric pressure photoionization ion source ("APPI ion source"), a laser desorption ionization ion source ("LDI ion source"), one inductive coupled plasma ion source ("ICP ion source"), an internal source with fast atom bombardment ("FAB ion source"), a liquid secondary ion mass spectrometry ion source ("LSIMS ion source"), a field ionization ion source ("FI ion source"), a field desorption ion source ("FD ion source"), an electron impact ion source ("EI ion source"), an internal source with chemical ionization ("CI ion source") and a matrix assisted laser desorption ionization ion source ("MALDI ion source"). The inner source can be continuous or pulsed.

One Another aspect of the present invention provides a method for Detecting particles with the following steps: Receive of particles at an entrance surface of a microchannel plate and discharging electrons from an exit surface of the microchannel plate, wherein the exit surface a first surface having. The method further includes the step of receiving of at least some of the electrons on a detection surface of a Detection device, with a second surface, wherein the second surface considerably greater than the first area is.

Preferably is the second area by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45 %, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% larger than the first area. The second surface can be at least 150%, 200%, 250%, 300%, 350%, 400%, 450 % or 500% larger as the first surface.

According to one In another aspect, the present invention provides a method for Detecting particles with the following steps: Receive of particles at an entrance surface of a microchannel plate, Delivering an average of x electrons per unit area from an exit surface of the Microchannel plate and receiving at least some of the electrons on a detection surface a detection device, wherein the detection area average y electrons per unit area receives and where x> y.

Preferably x is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 % or 100% greater than y. According to one another embodiment x can be at least 150%, 200%, 250%, 300%, 350%, 400%, 450 % or 500% larger than y be.

According to one In another aspect, the present invention provides a method for Detecting particles with the following steps: Receive of particles at an entrance surface of a microchannel plate and discharging electrons from an exit surface of the microchannel plate, wherein the exit surface a first surface having. The method further comprises the following steps: receiving at least some of the electrons on a first device, wherein the first device generates photons in response thereto Receiving at least some of the photons at a second device, wherein the second device generates electrons in response thereto and delivering, and receiving at least some of the second Device generated electrons on a detection device. The detection device has a detection surface a second surface on, with the second surface greater than the first area is.

According to one embodiment is the second area by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45 %, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% bigger than that first surface. According to one another embodiment is the second area by at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than the first area.

In another aspect, the present invention provides a method of detecting particles comprising the steps of: receiving particles at an entrance surface of a microchannel plate and delivering an average of x electrons per unit area from an exit surface of the microchannel plate. The method further comprises the steps of: receiving at least some of the electrons at a first device, the first device generating photons in response thereto, receiving at least some of the photons at a second device, the second device generating and emitting electrons in response thereto; and receiving at least some of the electrons generated by the second device at a detection surface of a detection device, the detection surface receiving an average of y electrons per unit area, where x> y.

According to one embodiment x is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 % or 100% greater than y. According to another embodiment x is at least 150%, 200%, 250%, 300%, 350%, 400%, 450 % or 500% larger than y.

According to one In another aspect, the present invention provides a method for Detecting particles with the following steps: Receive of particles at an entrance surface of a microchannel plate, Discharging electrons from an exit surface of the microchannel plate, wherein the exit surface a first surface receiving at least some of the electrons on a device, wherein the device generates photons in response thereto and receiving at least some of the photons generated by the device a detection surface a detection device having a second surface, the second surface substantially greater than the first area is.

According to one preferred embodiment is the second area by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45 %, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% larger than the first area. According to one another embodiment is the second area by at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than the first area.

According to one In another aspect, the present invention provides a method for Detecting particles with the following steps: Receive of particles at an entrance surface of a microchannel plate, Delivering an average of x electrons per unit area from an exit surface of the Microchannel plate, receiving at least some of the electrons a device, wherein the device in response to photons and receiving at least some of the device generated photons on a detection surface of a detection device, the detection surface receives on average z photons per unit area, where x> z is.

Preferably average x electrons per unit area and per unit time from the exit surface and on average z photons per unit area and per unit of time from the detection area receive.

According to one preferred embodiment x is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 % or 100% greater than z. According to one another embodiment x is at least 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% larger than z.

According to one In another aspect, the present invention provides a method for Mass spectrometry, which is a method for detecting particles, as described above.

In another aspect, the present invention provides a detector for use in a mass spectrometer, the detector comprising a microchannel plate, wherein in use, particles are received at an entrance surface of the microchannel plate and electrons are emitted from an exit surface of the microchannel plate, the exit surface being one has first surface. The detector further comprises a detection device having a detection surface adapted to receive, in use, at least some of the electrons released from the microchannel plate, the detection surface having a second surface. At a first time t ₁ , electrons emitted from the microchannel plate are received at a first portion or area of the detection area, and at a second later time t ₂ , electrons emitted from the microchannel plate are received at a second different portion or area of the detection area.

According to a preferred embodiment, at a third time t ₃ , which is later than the second time t ₂ , electrons emitted by the microchannel plate are received at the first portion or area of the detection surface. At a fourth time t ₄ , which is later than the third time t ₃ , electrons emitted from the microchannel plate may be received at the second portion or area of the detection surface.

Preferably is the second area considerably larger than the first area. The second area may be at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500 % to be taller as the first surface.

According to the preferred embodiment become on average x electrons per unit area from the exit surface given and average y electrons per unit area at the first section or area and / or the second section or area of the detection area receive. According to one embodiment is x> y, and x can by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45 %, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100 %, 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500% greater than y. According to one another embodiment x is substantially equal to y. According to one another embodiment is x <y, and x can be at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40 %, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95 %, 100%, 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500 % less than y.

Preferably they are at the entrance area received particles ions, photons or electrons.

In a preferred embodiment, in use, electrons are emitted from the exit surface of the microchannel plate into an electric field region. Preferably, at the first time t _1, the electric field is in a first direction and at the second later time t _{2 is} in a second different direction. At a third time t ₃ , which is later than the second time t ₂ , the electric field can run in the first direction. At a fourth time t ₄ , which is later than the third time t ₃ , the electric field can run in the second direction.

According to one preferred embodiment can the first and / or the second direction of the electric field below be inclined at an angle to the normal of the microchannel plate. Preferably the direction of the electric field becomes substantially in time continuously changed, from the exit surface the microchannel plate emitted electrons substantially continuously around or over the detection area to move, to lead or to turn. Alternatively, the direction of the electric field be changed substantially in a stepwise manner, from the exit surface of the Microchannel plate emitted electrons substantially stepwise around or over the detection area to move, to lead or to turn.

At the first time t ₁ , the electric field may have a first magnitude and may have a second magnitude at the second later time t ₂ . The first electric field strength may be substantially equal to the second electric field strength. The first electric field strength may be significantly different from the second electric field strength. At a third time t ₃ , which is later than the second time t ₂ , the electric field may have the first field strength, and at a fourth time t ₄ , which is later than the third time t ₃ , the electric field may be the second have electric field strength.

According to one embodiment becomes the electric field strength In time, essentially continuously changed to from the exit surface of the Microchannel plate emitted electrons substantially continuously around or over the detection area to move, to lead or to turn. According to one another embodiment becomes the electric field strength time essentially changed step by step from the exit surface of the Microchannel plate to move emitted electrons around or over the detection surface, to lead or to turn.

The preferred detector may further include at least one reflective electrode for reflecting electrons to the detection device. The at least one reflective electrode may be disposed in a plane substantially parallel to the microchannel plate, and is preferably arranged to guide electrons emitted from the microchannel plate at the first time t ₁ to the first portion or region of the detection surface the electrons emitted to the microchannel plate are guided to the second portion or area of the detection surface at the second later time t ₂ .

The preferred embodiment has one or more electrodes disposed between the microchannel plate and the detection device such that an electric field is provided between the microchannel plate and the detection device. The one or more electrodes may include one or more annular electrodes, one or more single lens arrays having three or more electrodes, one or more segmented rod sets, one or more tubular electrodes, one or more quadrupole, hexapole, octapole rod sets or sets of rods Order, several electrodes with openings, which have substantially the same area, of which electrons in use by and / or a plurality of electrodes having openings progressively smaller or larger toward the detection device, from which electrons are transmitted in use.

Preferably becomes the exit surface the microchannel plate held at a first potential and the detection surface of the Detection device held at a second potential. The second potential is preferably more positive than the first potential. The potential difference between the surface of the detection device and the exit surface the microchannel plate can be selected from the following group: 0-50 V, 50-100 V, 100-150 V, 150-200V, 200-250V, 250-300V, 300-350V, 350-400V, 400-450 V, 450-500 V, 500-550 V, 550-600 V, 600-650 V, 650-700 V, 700-750 V, 750-800 V, 800-850 V, 850-900 V, 900-950 V, 950-1000 V, 1.0-1.5 kV, 1.5-2.0 kV, 2.0-2.5 kV,> 2.5 kV and <10 kV.

at A preferred detector is the exit surface of the microchannel plate held a first potential, the detection surface of the Detection device held at a second potential and become a or more electrodes between the microchannel plate and the detection area are arranged, held at a third potential. Preferably be one or more electrodes between the microchannel plate and the detection surface are held at a fourth potential, and one or a plurality of electrodes disposed between the microchannel plate and the detection surface are, can on a fifth Potential to be kept. The third and / or the fourth and / or the fifth Potential can substantially equal to the first and / or the second potential be more positive than the first and / or the second potential and / or be more negative than the first and / or the second potential.

Preferably becomes the potential difference between the third and / or the fourth and / or the fifth Potential and the first and / or the second potential from the following group selected: 0-50 V, 50-100 V, 100-150 V, 150-200V, 200-250V, 250-300V, 300-350V, 350-400V, 400-450 V, 450-500 V, 500-550 V, 550-600 V, 600-650 V, 650-700 V, 700-750 V, 750-800 V, 800-850 V, 850-900 V, 900-950 V, 950-1000 V, 1.0-1.5 kV, 1.5-2.0 kV, 2.0-2.5 kV,> 2.5 kV and <10 kV.

The third and / or fourth and / or fifth potential may additionally or alternatively lie between the first and / or the second potential.

According to one preferred embodiment be electrons from the exit surface of the microchannel plate in given off an area with a magnetic field. The detector points preferably one or more magnets and / or one or more Electromagnets, which are arranged so that the magnetic field between the Micro channel plate and the detection device is provided.

At the first time t ₁ , the magnetic field may be in a first direction and may run in a second different direction at the second later time t ₂ . At a third time t ₃ , which is later than the second time t ₂ , the magnetic field can run in the first direction. At a fourth time t ₄ , which is later than the third time t ₃ , the magnetic field can run in the second direction. Preferably, the first magnetic field direction and / or the second magnetic field direction are substantially parallel to the microchannel plate.

According to one preferred embodiment the direction of the magnetic money becomes substantially continuous in time changed, from the exit surface the microchannel plate emitted electrons substantially continuously around or over the detection area to move, to lead or to turn. According to one other embodiment changes the magnetic field is substantially gradual in time from the exit surface of the Microchannel plate emitted electrons substantially stepwise around or over the detection area to move, to lead or to turn.

According to one embodiment, the magnetic field has a first magnetic field strength at the first time t ₁ and a second magnetic field strength at the second time t ₂ . The first magnetic field strength may be substantially equal to the second magnetic field strength, or the first magnetic field strength may be significantly different from the second magnetic field strength. At a third time t ₃ , which is later than the second time t ₂ , the magnetic field may have the first strength, and at a fourth time t ₄ , which is later than the third time t ₃ , the magnetic field may have the second strength ,

According to a preferred embodiment, the magnetic field strength is changed substantially continuously over time in order to move, guide or rotate electrons emitted from the exit surface of the microchannel plate essentially continuously around or over the detection surface. According to another embodiment, the magnetic field strength is changed substantially stepwise in time to move electrons emitted from the exit surface of the microchannel plate about or over the detection surface lead or turn.

Of the Detector may further comprise a grid electrode between the microchannel plate and the detection device is arranged. The grid electrode may be substantially hemispherical or otherwise nonplanar.

Of the Detector may be a detection device with a single detection area exhibit. The single detection area may be an electron multiplier, a scintillator or a photomultiplier tube. Preferably, the single detection area has one or more Microchannel plates and can the one or more microchannel plates over a first number of channels at least some of the second number of channels upstream Detection device disposed microchannel plate delivered Receive electrons, with the first number of channels significantly to be taller can be considered the second number of channels, this essentially same or may be considerably smaller than this.

According to one another embodiment the detector has a detection device with a first detection area and at least a second separate detection area. Of the second detection area is preferably of the first detection area spaced. The first and the second detection area can be in have substantially the same or significantly different detection surfaces. Preferably, the surface is of the first detection range by a percentage p greater than the area of the second detection area, where p is from the following group selected can be: <10 %, 10-20%, 20-30%, 30-40 %, 40-50%, 50-60%, 60-70%, 70-80%, 80-90% and> 90%. Preferably is the number of electrons received by the first detection surface by a percentage q is greater as the number of electrons received by the second detection surface, where q is selected from the following group: <10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70 %, 70-80%, 80-90 % and> 90%.

Of the the first and / or the second detection area may include one or more microchannel plates, an electron multiplier, a scintillator or a photomultiplier tube. Preferably, the detection device has at least one zigzag-shaped Pair of microchannel plates on.

Of the Detector may further comprise at least one collector plate, which is set up to use at least some of the generated or emitted electrons to the detection device receive. The at least one collector plate may be shaped that one temporal broadening of the time of flight of the detection device incident electrons is at least partially compensated. Alternatively or additionally the detection device can be shaped so that a temporal Widening of the time of flight of the incident on the detection device At least partially compensated electrons. Preferably the detector has one or more electrodes set up are to a temporal broadening of the time of flight on the detection device at least partially compensate for incident electrons.

According to one preferred embodiment There are one or more electrodes set up between the Micro-channel plate and the detection device an electric Provide field. A time-varying potential can at least one of the one or more electrodes are applied. The amplitude of the temporally variable Potential is preferably changed substantially sinusoidally in time. The Amplitude of the time-varying Potential can change with a frequency selected from the following group: 10-50 Hz, 50-100 Hz, 100-150 Hz, 150-200 Hz, 200-250 Hz, 250-300 Hz, 300-350 Hz, 350-400 Hz, 400-450 Hz, 450-500 Hz, 500-550 Hz, 550-600 Hz, 600-650 Hz, 650-700 Hz, 700-750 Hz, 750-800 Hz, 800-850 Hz, 850-900 Hz, 900-950 Hz, 950-1000 Hz, 1.0-1.5 kHz, 1.5-2.0 kHz, 2.0-2.5 kHz, 2.5-3.5 kHz, 3.5-4.5 kHz, 4.5-5.5 kHz, 5.5-7 , 5 kHz, 7.5-9.5 kHz, 9.5-12.5 kHz, 12.5-15 kHz, 15.0-20.0 kHz and> 20 kHz. According to the preferred Embodiment changes the amplitude of the potential with a frequency between about 50 Hz and about 10 kHz.

Additionally or alternatively, the time-varying Potential intermittent to at least one of the one or more Electrodes are created. The frequency with which the potential can be applied to the one or more electrodes can selected from the above group become.

According to one preferred embodiment At least some of the votes are from separate channels of the microchannel plate Electrons on essentially separated, non-overlapping Areas on the detection area receive.

The detection area may be in the circumferential direction and contiguous to the exit surface of the microchannel plate extend. The detection device can essentially in the same level as the microchannel plate.

According to one Another aspect of the invention provides a mass spectrometer with a previously described detector.

Preferably the detector forms part of a time-of-flight mass analyzer. The detector can continue an analog-to-digital converter ("ADC") and / or one Time-to-digital converters ("TDC"), the connected to the detector.

The Mass spectrometer may have an internal source, which from the Group selected is, which consists of the following: an electrospray ionization ion source ("ESI ion source"), an atmospheric pressure ionization ion source ("API ion source"), an atmospheric pressure ion source with chemical ionization ("APCI ion source"), an atmospheric pressure photoionization ion source ("APPI ion source"), a laser desorption ionization ion source ("LDI ion source"), one inductive coupled plasma ion source ("ICP ion source"), an internal source with fast atom bombardment ("FAB ion source"), a liquid secondary ion mass spectrometry ion source ("LSIMS ion source"), a field ionization ion source ("FI ion source"), a field desorption ion source ("FD ion source"), an electron impact ion source ("EI ion source"), an internal source with chemical ionization ("CI ion source") and a matrix-assisted laser desorption ionization ion source ( "MALDI") ion source. The inner source can be continuous or pulsed.

In a further aspect, the invention provides a method of detecting particles comprising the steps of: receiving particles at an entrance surface of a microchannel plate, discharging electrons from an exit surface of the microchannel plate, the exit surface having a first surface, and receiving at least some the electrons on a detection surface of a detector having a second surface. At a first time t ₁ , electrons emitted from the microchannel plate are received at a first portion or area of the detection area, and at a second later time t ₂ , electrons emitted from the microchannel plate are received at a second different portion or area of the detection area.

According to one In another aspect, the present invention provides a method for Mass spectrometry, which is a method described above for detecting particles.

According to one first preferred main embodiment fall primary ions on a first microchannel plate, which in response secondary electrons generated. The secondary electrons are subsequently on one or more secondary Directed to microchannel plates or other detection devices, which are set up so that theirs total area preferably considerably larger as that of the first microchannel plate and that they are spaced therefrom. In this way, those generated by the first microchannel plate Secondary electrons over one larger second Electron multiplication surface dispersed.

The Dispersing the secondary electrons over a is relatively large electron multiplication surface compared with the dispersion of the inner jet over a relatively large ion detection area advantageous, because it is not required that an electric field in the area upstream of the Interior detector is introduced. This is particularly advantageous if the area is upstream of the inner detector, the drift region of a time-of-flight mass spectrometer is.

According to one preferred embodiment becomes the of the exit surface generated the second microchannel plate and then emitted secondary electron current over the Detection device dispersed. Accordingly, the Electrons over a relatively large number of channels either in a single larger microchannel plate or dispersed in multiple microchannel plates with a higher total number of channels become. This is preferably achieved by that of the first microchannel plate emitted secondary electrons are deflected or the secondary electrons over the surface the one or more microchannel plates of the detection device be steered.

According to a second preferred main embodiment, secondary electrons emitted by the first microchannel plate are scanned over one or more microchannel plates of a detection device over a time scale relating to the recovery time of the individual channels of the one or more microchannel plates. By distributing the secondary electrons from the first microchannel plate via the microchannel plates of the detection device, the detector is capable of delivering a relatively high output current for a given overall gain with minimal distortion of the pulse height distributions.

According to one preferred embodiment can the secondary electrons emitted by the first microchannel plate evenly or unevenly between two or more separate secondary Microchannel plate assemblies, electron multiplier tubes ("EMT") or photomultiplier tubes ("PMT"). The output current of such electron multipliers can then with a suitable processor, for example an analog-to-digital converter ("ADC") or a time-to-digital converter, be coupled. Alternatively, a combination of analog and Time-to-digital converters coupled with the electron multipliers become. By coupling a combination of analog and time-to-digital converters with the electron multipliers, the dynamic range of the ion detection system be increased overall.

at a preferred embodiment it becomes primary ions allows on an entrance area a first microchannel plate arrangement, so that secondary electrons generated and discharged from the exit surface become. The first microchannel plate may preferably be at a relatively low reinforcement operated, and that of the first microchannel plate assembly emitted secondary electrons can preferably substantially uniformly on a second larger microchannel plate or more microchannel plates having a total area, the greater than that of the first microchannel plate is to be defocused. This will cause an increase the number of for provided the electron multiplication channels available without the properties the individual channels, For example, the time constant for the channel recovery or the Channel resistance, changed become. This embodiment leads therefore to that a higher maximum Output current from the secondary electron multipliers can be generated without the Interior detector saturates. It can Various methods are used to control the secondary electron beam from the first microchannel plate assembly to the second microchannel plate assembly to distract, focus, judge or guide the insertion electrostatic and / or magnetic fields.

According to one preferred embodiment the detector detects particles, for example ions, at one first microchannel plate containing a single circular microchannel plate with an active cross-sectional diameter D has on. One behind the first microchannel plate arranged detection device may be arranged in a zigzag Pair of circular Have microchannel plates with an active diameter of 2D. According to this embodiment is the maximum output current of the indoor detector in about four times greater than the maximum output of a single arrangement of a zigzag pair with a diameter D at the same gain.

In a preferred embodiment, the first microchannel plate may be a single circular microchannel plate having an active diameter of 25 mm. The first microchannel plate preferably has a channel diameter of 10 microns and may have a channel pitch of 12 microns, so that a total of 3.9 × 10 ⁶ channels can be provided. The zigzag pair of microchannel plates may preferably have a larger active diameter of 50 mm. The channels in the zigzag pair of microchannel plates may also preferably have a diameter of 10 μm and a channel pitch of 12 μm, resulting in a total of 1.6 × 10 ⁷ channels. The resistance in each channel in the microchannel plates can be 1.2 × 10 ¹⁴ Ω. Accordingly, the total resistance of the first microchannel plate is 3 × 10 ⁷ Ω, and the total resistance of each microchannel plate in the zigzag pair of microchannel plates is 7.5 × 10 ⁶ Ω. The channels of each of the microchannel plates preferably have a length to diameter ratio of 46: 1, although other ratios may be used.

According to the above mentioned preferred embodiment leads that Apply a 380 V bias to the first microchannel plate to a medium gain from about × 10 over the first microchannel plate. The arrival of a single ion at the entrance of the first microchannel plate leads therefore, on average, that ten Electrons from a single channel at the exit surface of the first microchannel plate are delivered.

A bias voltage of 1700V may preferably be applied to the zigzag pair of microchannel plates, resulting in an average gain of about 5x10 ⁵ over the zigzag pair located downstream of the first microchannel plate disposed microchannel plates. Accordingly, the overall gain of the first microchannel plate and the zigzag is Assigned pair of microchannel plates in the inner detector in about 5 × 10 ^6th

In order to ensure that the secondary electrons emitted from each channel of the first microchannel plate are distributed over the maximum area of the zigzag pair of microchannel plates, the diameter D _{e of} the plume of each channel is equal to secondary electrons as they fall on the zigzag pair of microchannel plates , preferably the diameter D _{2 of} the zigzag pair, which is smaller than the diameter D _{1 of} the first microchannel plate. According to the above embodiment, D ₂ -D _{1 is} 25 mm. The maximum exit angle φ at which the secondary electrons exit the exit face of the first microchannel plate with respect to the plane of the first microchannel plate is determined by the channel diameter d _c and the depth P to which the non-emissive coating applied to the exit surface of the Micro channel plates is applied, penetrates into the channels (final impairment). Typically, the end impact of the channels is one channel diameter. The maximum exit angle φ of the secondary electrons emitted by the first microchannel plate can be calculated as indicated below:

According to the above specified embodiment is the maximum exit angle φ 45 °.

For the channel diameter, the relationship between the channel length and the channel diameter (1 / d _c) and the Endbeeinträchtigung which have been indicated above, the average energy of the emerging from the first micro channel plate secondary electron can be calculated on the basis of the voltage applied to the first micro channel plate bias , When a bias voltage of 380 V is applied to the first microchannel plate, the average energy E of the secondary electrons emerging from the first microchannel plate is 5 eV.

wobei S der Abstand zwischen der Austrittsfläche der ersten Mikrokanalplatte und der Eintrittsfläche des zickzackförmig angeordneten Paars von Mikrokanalplatten ist. Dementsprechend sollten die Abstände zwischen der ersten Mikrokanalplatte und dem zickzackförmig angeordneten Paar von Mikrokanalplatten vorzugsweise 12,5 mm betragen, um einen Durchmesser D_e der Wolke der von einem einzigen Austrittskanal der ersten Mikrokanalplatte abgegebenen Sekundärelektronen von 25 mm zu erreichen. Der Durchmesser D_e der Wolke von Sekundärelektronen an der Eintrittsfläche des zickzackförmig angeordneten Paars von Mikrokanalplatten kann geändert werden, indem ein Potential V_b zwischen der Austrittsfläche der ersten Mikrokanalplatte und der Eintrittsfläche des zickzackförmig angeordneten Paars von Mikrokanalplatten gelegt wird. Bei einer solchen Ausführungsform kann der Durchmesser D_e der Wolke von Sekundärelektronen folgendermaßen berechnet werden:

When there is no potential difference between the exit surface of the first microchannel plate and the entrance surface of the zigzag pair of microchannel plates, the diameter D _{e of} the cloud of secondary electrons emitted from a single channel of the first microchannel plate may be calculated according to the following equation:

where S is the distance between the exit surface of the first microchannel plate and the entrance surface of the zigzag pair of microchannel plates. Accordingly, the distances between the first microchannel plate and the zigzag pair of microchannel plates should preferably be 12.5 mm to reach a diameter D _{e of} the cloud of 25 mm emitted from a single exit channel of the first microchannel plate. The diameter D _{e of} the cloud of secondary electrons at the entrance surface of the zigzag pair of microchannel plates can be changed by placing a potential V _b between the exit surface of the first microchannel plate and the entrance surface of the zigzag pair of microchannel plates. In such an embodiment, the diameter D _{e of} the cloud of secondary electrons may be calculated as follows:

For example, for a distance of 50 mm and a potential difference of 120 V between the exit surface of the first microchannel plate and the entrance surface of the zigzag pair of microchannel plates, the diameter D _{e of} the cloud of secondary electrons at the entrance surface of the zigzag pair of microchannel plates is 25 mm.

According to another embodiment, the secondary electrons emitted by the first microchannel plate may be allowed to strike an organic or inorganic scintillator. An organic scintillator or plastic scintillator is preferred because the rise and fall times of such scintillators are on the order of 0.5-2 ns. Photons emitted by the scintillator may then be directed by an optical fiber to a photocathode window having a larger area than the first microchannel plate. Alternatively, the photons emitted by the scintillator may become a plurality of photoca be steered whose total area is greater than the area of the first microchannel plate assembly. For example, gallium arsenide can be used as the photocathode material. The emitted from the photocathode electrons can then be passed to a detection device with one or more other microchannel plates. The further microchannel plates preferably also have a larger total area than the first microchannel plate. Preferably, most of the electron multiplication is performed on the second microchannel plate stage.

The Dispersing the secondary electrons emitted by the first microchannel plate via one or more several more second microchannel plates with a larger total area makes it possible that the Input ion current around the ratio between the area the first microchannel plate and the surface of the second microchannel plate is enlarged, without that reinforcement affected by the detection system is, where the pulse height distribution only minimally affected becomes. additionally allows this embodiment a beneficial electrical decoupling of the output of the detector from other components of the mass spectrometer. Accordingly, the Output of a detector according to a nominal embodiment are at ground potential and conditions for conditioning of the output signal can therefore be simplified.

at an embodiment The present invention will be secondary electrons from the first Microchannel plate over the surface a second larger detection device dispersed or guided. The detection device preferably has one or more microchannel plates with a larger total area. According to this embodiment can the secondary electrons by one or more electrical and / or magnetic fields over the detection area dispersed or guided become. According to this embodiment can the secondary electrons emitted by the first microchannel plate not necessarily focused on the detection surface, but you can preferably over a relatively large area of detection area be diverged. This ensures that substantially all channels in the one or more microchannel plates of the detection device be used.

According to one another embodiment become the secondary electrons emitted by the first microchannel plate at a certain time to a discrete area of the detection surface of the Detection device focused or guided. The detection device may have one or more microchannel plates whose total area is larger than that the first microchannel plate is. According to this embodiment become the secondary electrons preferably focused so that they preferably on the one or more microchannel plates the detection device minimum possible number of channels fall. The emitted from the first microchannel plate secondary electrons can preferably by a time-varying electrical and / or magnetic deflection field between different areas of the second Micro channel plate assembly continuously deflected, guided or rotated or periodically switched, guided or rotated. The average number of secondary electrons by one area the one or more microchannel plates of the detection device are received per unit time, is preferably smaller than that average number of secondary electrons per unit of time from a corresponding area the first microchannel plate are delivered. According to this embodiment Advantageously, a minimal broadening of the pulse height distribution occurs because of the total number of through a at the first microchannel plate incoming single ion generated secondary electrons over relatively few channels the one or more microchannel plates in the detection device is distributed. Therefore, it is more likely that the output of each Channels in the one or more microchannel plates of the detection device space charge is limited, resulting in a relatively narrow pulse height distribution leads.

One particular advantage of the preferred embodiment of the present invention Invention is that the maximum average output current of the indoor detector, the possible is before the gain of the Interior detector impaired will, opposite a conventional one Ion detection system increased is.

Various embodiments of the present invention will now be described together with other arrangements, the only explanation serve as an example with reference to the attached drawing described. Show it:

1A a schematic representation of a partial view of a conventional microchannel plate and 1B Secondary electrons generated within a channel of a microchannel plate detector,

2 a schematic representation of a first main embodiment of the present invention, wherein an electrostatic lens is used to secondary emitted from a first microchannel plate secondary electron to diverge on a second larger microchannel plate,

3 a SIMION model of the trajectories of secondary electrons when they emerge from the first microchannel plate according to the first main embodiment of the present invention and are diverged to the second larger microchannel plate,

4 a SIMION model of the trajectories of the secondary electrons according to an embodiment, wherein a grid electrode is used for diverging the secondary electrons,

5 5 is a schematic representation of an embodiment wherein the secondary electrons emitted by the first microchannel plate are incident on a scintillator, and photon scattering on the scintillator is diverged to a larger photocathode disposed in front of a second microchannel plate;

6 a SIMION model of trajectories of secondary electrons according to another embodiment, wherein an electrode is provided to divide secondary electrons into two separate electron streams,

7 a SIMION model of the trajectories of the secondary electrons according to an embodiment similar to in 6 in which, instead of a microchannel plate, a photomultiplier tube is used to detect one of the secondary electron currents,

8th a SIMION model of the trajectories of secondary electrons according to an embodiment, wherein the secondary electrons are divided into two unequal secondary electron currents,

9A a SIMION model of the trajectories of secondary electrons according to a second main embodiment of the present invention, wherein the emitted from a first microchannel plate secondary electrons are guided at a first time to only a portion of the relatively large microchannel plate, and 9B the secondary electrons, which are led to a second different portion of the microchannel plate at a second later time,

10A a schematic representation of an embodiment, wherein emitted from a first microchannel plate secondary electrons are rotated by a quadrupole lens assembly over the entrance surface of a relatively large microchannel plate, and 10B the deflection movement of the secondary electron beam across the surface of the microchannel plate detector,

11A an embodiment wherein secondary electrons emitted from different channels of a first microchannel plate are made to vary in time from an electrostatic lens or electrode assembly to substantially non-overlapping regions of a relatively large microchannel plate, and 11B an exemplary AC voltage that may be applied to the electrostatic lens or electrode assembly to move the secondary electrons across the surface of the microchannel plate detector;

12 an embodiment wherein a multipole rod lens assembly is used to move the secondary electrons over the surface of a microchannel plate detector in a time-varying manner,

13A a SIMION model of the trajectories of secondary electrons according to an embodiment, wherein the secondary electrons are guided at a first time by the combination of an electric and a magnetic field to a first region of a coplanar microchannel plate detector, and 13B the trajectories of the secondary electrons at a second later time when the electric field is reduced, and

14A a SIMION model of the trajectories of secondary electrons, wherein the electrons are guided at a first time by a magnetic field in a first direction to a coplanar zigzag arranged pair of microchannel plates, and 14B the secondary electrons, which are guided at a second later time by a magnetic field in a second direction opposite to the first direction to another coplanar pair of microchannel plates.

A conventional microchannel plate is in 1A shown. The microchannel plate 1 has a periodic arrangement of glass capillaries or channels 2 with a very small diameter through that Melt were joined together and cut into a thin plate. The microchannel plates 1 typically have several million channels 2 on, and every channel 2 acts as an independent electron multiplier.

1B shows how a single channel works 2 a microchannel plate 1 , A single incident particle 3 For example, an ion (or less preferably an electron or a photon) enters the channel 2 and causes secondary electrons 4 from the canal wall 5 be emitted. A potential difference V _D is across the microchannel plate 1 sustains, and it generates an electric field that the secondary electrons 4 to the exit surface of the microchannel plate 1 accelerated. The secondary electrons 4 run along parabolic flight tracks through the canal 2 until they reach the canal wall 5 meet, whereupon they have more secondary electrons 4 produce. This process is repeated several times along the channel 2 repeatedly, resulting in a cascade of secondary electrons 4 from the exit of the irradiated canal 2 the microchannel plate 1 delivered or emitted. The microchannel plate 1 can be arranged so that at the exit surface in response to a single incident particle (for example, an ion) several thousand secondary electrons 4 be generated.

A first main embodiment of the present invention will now be described with reference to FIG 2 described. 2 shows a detector 7 for a mass spectrometer, preferably an interior detector, comprising a first microchannel plate 8th has, from the ions 12 (or less preferably other particles) are received or the ions are incident. The first microchannel plate 8th preferably generates secondary electrons 16 then from the first microchannel plate 8th are emitted and preferably to a detection device 9 be transferred behind the first microchannel plate 8th arranged and spaced therefrom. An electrostatic lens assembly 17 or an array of one or more electrodes (or less preferably one or more magnetic lenses) is preferably between the first microchannel plate 8th and the detection device 9 arranged. The detection device 9 preferably has a pair of zigzag microchannel plates 10 . 11 on, so that the channels within the two microchannel plates 10 . 11 at an angle to the interface between the two microchannel plates 10 . 11 stand. A collector plate 15 is preferably behind the farthest of the two the detection device 9 forming microchannel plates 11 arranged.

The first microchannel plate 8th is preferably a single microchannel plate operated at a relatively low gain of, for example, x 5 and x 20 and the zigzag microchannel plates 10 . 11 are preferably operated with a relatively high gain of × 10 ⁶ . The interior detector 7 therefore preferably has an overall gain between 5 × 10 ⁶ and 2 × 10 ⁷ .

According to a preferred embodiment, at least one, preferably at least two, three, four, five, six, seven, eight, nine or ten electrostatic lenses or electrodes 17a . 17b . 17c between the first microchannel plate 8th and the zigzag pair of microchannel plates 10 . 11 arranged. According to one embodiment, the electrostatic lenses may comprise cylindrically symmetrical electrodes. Other electrode arrangements are also contemplated. The electrostatic lenses are preferably for use by the first microchannel plate 8th to the desired portion or the desired area of the detection surface of the detection device 9 emitted secondary electrons 16 to focus, diverge or lead. According to the first main embodiment, secondary electrons are used 16 preferably on and over substantially the entire detection surface of the detection device 9 (ie the microchannel plates 10 . 11 ) diverges.

During operation, the ions emerging, for example, from the drift or flight range of a time-of-flight mass analyzer fall 12 preferably on an entrance surface of the first microchannel plate 8th , The first microchannel plate 8th generates secondary electrons in response to the arrival of an ion (or less preferably the arrival of a photon or electron) 16 , The number of the first microchannel plate 8th generated secondary electrons 16 each interior incidence preferably approaches a Poisson distribution. The one from the first microchannel plate 8th generated secondary electrons 16 are then preferably from an exit surface of the first microchannel plate 8th delivered and preferably by a between the exit surface of the first microchannel plate 8th and the entrance surface of the detection device 9 maintained potential difference to the detection device 9 (For example, a zigzag arranged pair of microchannel plates 10 . 11 ) speeds up.

The secondary electrons 16 come out of the first microchannel plate 8th with an angular distribution that focuses on the bias across the first microchannel plate 8th and the field gradient between the exit surface of the first microchannel plate 8th and the entrance surface of the second microchannel plate 10 which the front end of the detection device 9 forms, relates. The secondary electrons 16 are preferably not on the second microchannel plate 10 but they preferably become substantially uniform across the entrance or detection surface of the second microchannel plate 10 distributed and diverged. This ensures that repeating primary ion events at the first microchannel plate 8th secondary electron 16 generate over a relatively moderately large area of the second microchannel plate 10 are distributed.

At least some, preferably substantially all secondary electrons 16 are preferably from the entrance surface of the second microchannel plate 10 receive, and tertiary electrons 14 are preferably in response thereto of the zigzag arranged pair of microchannel plates 10 . 11 generated. The tertiary electrons 14 are preferably from the exit surface of the third microchannel plate 11 emitted and can from a collector plate 15 behind the third microchannel plate 11 is arranged, received and detected.

The dispersion of the first microchannel plate 8th emitted secondary electrons 16 over a second larger microchannel plate 10 advantageously allows the input ion current to be the ratio between the area of the second microchannel plate 10 and the area of the first microchannel plate 8th is increased without the gain of the inner detector 7 is impaired.

3 shows a two-dimensional SIMION simulation in which the trajectories of the first microchannel plate 8th emitted secondary electrons 16 are shown when they are to the second microchannel plate 10 of the interior detector 7 be accelerated. An electrostatic lens or electrode assembly 17 is as shown between the first microchannel plate 8th and the second microchannel plate 10 arranged to the secondary electrons 16 over the detection area of the second microchannel plate 10 to distribute. The SIMION simulation represents electron trajectories 16 for secondary electrons, which under one to the surface of the first microchannel plate 8th emerge perpendicular angle and have an initial energy of 20 eV. In this simulation, the entrance surface of the second microchannel plate became 10 held at a potential which was +105 V higher than that of the exit surface of the first microchannel plate 8th , The exit surface of the first microchannel plate 8th For example, it can be held at 0 V and secondary electrons 16 emit from a substantially circular exit surface with a diameter of 25 mm. The second microchannel plate 10 preferably receives at least some, preferably all, of the secondary electrons 16 over a substantially circular detection surface with a larger diameter of for example 50 mm. The first microchannel plate 8th and the second microchannel plate 10 may be spaced 20 mm apart according to one embodiment. In another embodiment, another distance may be between the first microchannel plate 8th and the second microchannel plate 10 be used.

The first electrode 17a , the second electrode 17b and the third electrode 17c the one between the first microchannel plate 8th and the second microchannel plate 10 arranged electrostatic lens 17 were in the in 3 simulated at potentials which were +100 V, +500 V and +0 V higher than the potential of the exit surface of the first microchannel plate 8th ,

The electrodes 17a . 17b . 17c the electrostatic lens 17 are preferably ring electrodes, and they have circular rings whose diameter is preferably in the direction of the second microchannel plate 10 increase. The secondary electrons preferably pass through each of the ring electrodes 17a . 17b . 17c the electrostatic lens 17 and preferably over the larger entrance surface of the second microchannel plate 10 dispersed.

The electrostatic lens 17 or the electrode arrangement preferably provide a point-to-point imaging for secondary electrons 16 ready, which at an angle from the first microchannel plate 8th emerge, which is perpendicular to its exit surface, and which have the same initial energy. The electrostatic lens 17 however, does not provide a point-to-point mapping for secondary electrons 16 at angles that are not perpendicular to the exit surface of the microchannel plate 8th are, from the first microchannel plate 8th escape, or for secondary electrons 16 ready with a range of energies.

It is at each of the electron trajectories 16 in 3 (and in subsequent simulations) marks representing the position of the secondary electrons 16 at successive time intervals of 0.25 ns. How out 3 can be seen, reach secondary electrons 16 with trajectories that are closer to the electrodes 17a . 17b . 17c the electrostatic lens 17 lie, the second microchannel plate 10 in front of secondary electrons, which are farther away from the electrodes 17a . 17b . 17c move (ie within the central area between the first and second microchannel plate 8th . 10 move). Therefore, as in 3 It can be seen, a small temporal broadening in the arrival times of the secondary select ronen 16 at the second microchannel plate 10 for from the first microchannel plate 8th induced electrons in response to simultaneous ion arrivals. It can be seen in this simulation that in the arrival times of the secondary electrons 16 caused temporal broadening in the order of a mark, that is in the order of 0.25 ns. This temporal broadening can, if desired, be corrected by the collector plate 15 is preferably suitably shaped and / or by a further electrostatic element between the first and the second microchannel plate 8th . 10 provided.

Although only shown in two dimensions, the in 3 illustrated SIMION simulation electron trajectories 16 for a three-dimensional arrangement with a cylindrical symmetry. According to a preferred embodiment, a collector plate 15 downstream of the last electron multiplier element 11 (ie the third microchannel plate 11 ) and may be shaped to compensate for the temporal broadening of the arrival times of secondary electrons. It will be understood that the shape, size, number and potentials for the electrodes 17a . 17b . 17c the electrostatic lens 17 may be varied, and are not limited to the above-described exemplary and illustrated in the drawings.

4 shows a SIMION simulation of trajectories of secondary electrons 16 according to an embodiment, wherein a grid electrode 18 between the exit surface of the first microchannel plate 8th and an entrance or detection surface of the second microchannel plate 10 is arranged to the secondary electrons 16 over the entrance surface of the second microchannel plate 10 to disperse. The grid electrode 18 may preferably be substantially non-planner and preferably curved or dome-shaped.

A potential difference may be between the exit surface of the first microchannel plate 8th and the grid electrode 18 be maintained so that secondary electrons 16 to the grid electrode 18 be accelerated. In this simulation, the entrance surface of the second microchannel plate became 10 held at a potential that was +1000 V higher than that of the exit surface of the first microchannel plate 8th , The exit surface of the first microchannel plate 8th can be kept at 0 V and secondary electrons 16 from a substantially circular exit surface with a diameter of 25 mm. The second microchannel plate 10 may preferably be a distance of 30 mm from the first microchannel plate 8th spaced and preferably receives secondary electrons 16 over a substantially circular area with a diameter of 40 mm.

According to other embodiments, those of the first microchannel plate 8th emitted secondary electrons 16 distributed over two or more detectors. The two or more detectors preferably have microchannel plates. Distributing the secondary electrons 16 using two or more detectors results in an increased number of channels being available for electron multiplication, and hence the dynamic range of the inner detector 7 is enlarged. In such embodiments, the outputs of the last multiplication stages may be directed to the same recording device or to separate recording devices. The outputs of the two or more detectors may preferably be directed to a combination of analog-to-digital and time-to-digital recording devices such that the dynamic range of the interior detector 7 is enlarged.

According to one embodiment, those of the first microchannel plate 8th emitted secondary electrons 16 evenly or nonuniformly divided into two or more portions or streams of electrons and directed to the entrance surfaces of the two or more detectors. The two or more detectors may include microchannel plates, electron multiplier tubes, photomultiplier tubes, or a combination of detectors. The distribution of the secondary electron current between two or more detectors allows for a higher overall ion arrival rate at the first microchannel plate without a gain loss due to detector saturation.

5 shows a further embodiment, which is arranged to ensure that at least some, preferably all of the first microchannel plate 8th emitted secondary electrons 16 on an organic or inorganic scintillator 19 hit that between the first microchannel plate 8th and the second microchannel plate 10 is arranged. The arrival of secondary electrons 16 at the scintillator 19 causes photons 20 from the scintillator 19 be generated. The scintillator 19 emitted photons 20 are preferably through a non-focusing light guide (not shown) to a photocathode window 21 directed, which preferably has a larger area than the emission surface of the scintillator 19 , from the photons 20 be emitted. The photocathode 21 preferably has a larger area than the first microchannel plate 8th ,

The scintillator 19 is preferably an organic scintillator or a plastic scintillator because the rise and fall times are typically on the order of 0.5-2 ns. The photocathode 21 preferably receives at least some of the scintillator 19 emitted photons 20 and generates electrons 22 in response to photon arrivals. The photocathode 21 preferably includes a gallium arsenide photocathode.

The from the photocathode 21 generated or emitted electrons 22 are then preferably on the entrance surface of the second microchannel plate 10 directed. The second microchannel plate 10 preferably has an entrance area which is larger than the exit area of the first microchannel plate 8th and / or the scintillator 19 , It is also considered (although this is in 5 not shown) that the entrance surface of the second microchannel plate 10 could be larger than the exit area of the photocathode 21 so that from the photocathode 21 emitted electrons also on the second microchannel plate 10 could be diverged. The second microchannel plate 10 preferably forms one of a zigzag pair of microchannel plates 10 . 11 which acts as an electron multiplier and emits electrons attached to a collector plate 15 to receive and detect.

According to another preferred embodiment, the scintillator 19 emitted photons 20 be directed to a plurality of photocathodes having a combined entrance or receiving surface, which is preferably larger than that of the scintillator 19 and / or the first microchannel plate 8th ,

According to another embodiment, the photocathode 21 not be provided, and the photons from the scintillator 19 can directly on the second microchannel plate 10 of the detector 9 be received. According to this embodiment, those of the scintillator 19 emitted photons, preferably UV photons.

An advantage of this embodiment is that the output of the inner detector 7 electrically from other components of the mass spectrometer upstream of the detector 9 can be decoupled. This is particularly advantageous in embodiments where the component located upstream of the detector is the drift or flight range of a time-of-flight mass spectrometer. According to a preferred embodiment, the collector plate 15 of the interior detector 7 For example, be held at a virtual ground potential, whereby the output signal of power supply noise and switching voltages is isolated. This configuration not only reduces the electronic noise but also greatly simplifies the output signal amplification requirements.

6 shows a two-dimensional SIMION simulation in which the trajectories of secondary electrons 16 for an embodiment in which a splitting electrode 26 is provided to that of the first microchannel plate 8th emitted secondary electrons 16 divide so that a portion or a stream of secondary electrons 16a from a first detector 23 is received and another portion or another stream of secondary electrons 16b from a second detector 24 Will be received.

At the in 6 The simulation shows the secondary electrons 16 below one to the level of the first microchannel plate 8th vertical angle with an initial energy of 20 eV from the first microchannel plate 8th out. In this simulation, the splitting electrode became 26 held at a potential of +300 V and became the entry surfaces of the two detectors 23 . 24 at a potential of +1000 V with respect to the exit surface of the first microchannel plate 8th held. The distance between the first microchannel plate 8th and the plane in which the detectors 23 . 24 are arranged, was 31 mm. The first microchannel plate 8th gives secondary electrons 16 from a preferably substantially circular area having a diameter of preferably 25 mm. The marks on each electron trajectory 16a . 16b correspond to the position of the secondary electrons at successive time intervals of 0.5 ns.

According to this embodiment, the secondary electrons become two substantially equal portions or streams 16a . 16b split, which is then on the entrance surfaces of the two detectors 23 . 24 be directed. The detectors 23 . 24 are preferably arranged in the same plane and preferably spaced apart from one another by at least some of the first microchannel plate 8th to receive emitted secondary electrons.

The combined area of the entrance surfaces of the two detectors 23 . 24 is preferably larger than the area of the first microchannel plate 8th which emits the secondary electrons, that of the two detectors 23 . 24 be received. The detectors 23 . 24 preferably each have a zigzag arranged pair of microchannel plates 10 . 11 on. The splitting electrode 26 is preferably between the two De detectors 23 . 24 arranged or located therebetween and preferably extends to the center of the exit surface of the first microchannel plate 8th , One or more additional electrodes 25a . 25b can be in the same plane as the first microchannel plate 8th to be provided. The one or more electrodes 25a . 25b may be a ring electrode or ring electrodes, which are the microchannel plate 8th surrounded, or the one or more electrodes 25a . 25b may include separate discrete electrodes. The one or more further electrodes 25a . 25b are preferably at a lower voltage with respect to the detectors 23 . 24 held and preferably at the same voltage as the first microchannel plate 8th held.

7 shows a two-dimensional SIMION simulation, in the trajectories of secondary electrons 16a . 16b for an embodiment similar to that in FIG 6 however, although one of the detectors 24 a zigzag pair of microchannel plates 10 . 11 has, the other detector 23 a scintillator and a photomultiplier tube.

8th shows a two-dimensional SIMION simulation in which the trajectories of secondary electrons 16a . 16b for an embodiment similar to that in FIG 6 However, in this embodiment, the secondary electrons from the splitter electrode 26 uneven between the two detectors 23 . 24 be split. In this simulation, the splitting electrode is located 26 outside the center of the first microchannel plate 8th , The partitioning electrode is preferably maintained at a potential which is +200 V higher than that of the exit surface of the first microchannel plate 8th which can be kept at 0V. According to this embodiment, the electrode is 26 outside the center of the exit surface of the first microchannel plate 8th arranged so that in about 75% of the first microchannel plate 8th emitted secondary electrons on the entrance surface of the first detector 23 be directed and 25% of the first microchannel plate 8th emitted secondary electrons on the entrance surface of the second detector 24 be directed. This embodiment allows two different types of detection electronics to be used with the two preferably separate detectors 23 . 24 be used. The splitting electrode 26 may be more or less outside the center of the exit surface of the first microchannel plate 8th be arranged so that the secondary electrons in a desired ratio to the two detectors 23 . 24 be directed.

A second main embodiment of the present invention will now be described in which ions 12 (or other particles) using a first microchannel plate 8th , which operates at a low gain, in secondary electrons 16 being transformed. The one from the first microchannel plate 8th emitted secondary electrons 16 are then applied to a specific portion, area or area of a detection device 9 directed, deflected or otherwise guided with an entrance surface, which is preferably larger than the exit surface of the first microchannel plate 8th , The portion, area or area of the detection device 9 , whereupon the secondary electrons 16 are conducted at a certain time, is preferably smaller than the entire detection surface of the detection device 9 (ie only a fraction of it) and can be smaller than the total area of the first microchannel plate 8th be.

The secondary electrons 16 can continuously over the surface of the detection device 9 or entrained, moved or rotated around them (or alternatively periodically switched, entrained, moved or rotated in a preferably stepwise manner) such that the average number of secondary electrons 16 , which per unit time on a surface, a section or an area of the detector 9 is less than the average number of areas of a size corresponding to the first microchannel plate 8th emitted secondary electrons 16 ,

According to a preferred embodiment, the relatively large detection device 9 a second microchannel plate 10 and optionally a third microchannel plate, preferably zigzag with the second microchannel plate 10 is arranged. According to this embodiment, those of the first microchannel plate 8th secondary electrons generated for a single ion arrival 16 on the second microchannel plate 10 focused or directed so that the secondary electrons 16 on as few channels as possible 2 the second microchannel plate 10 fall. This focusing of the secondary electrons 16 allows maintaining a narrow pulse height distribution.

According to the second main embodiment, the preferred interior detector 7 a first microchannel plate 8th with an area A ₁ and a second microchannel plate 10 having a larger area A ₂ , both microchannel plates 8th . 10 preferably have identical channel diameter and lengths. An electrostatic lens system or an electrode arrangement is preferably between the first micro channel plate 8th and the second microchannel plate 10 arranged and preferably arranged so that the secondary electrons 16 on discrete areas of the entrance surface of the second microchannel plate 10 be focused, directed or guided. According to this embodiment, the maximum average output current of the inner detector 7 before the onset of saturation, compared with the maximum average output current of a single internal detector with an area A ₁ increased by the ratio A ₂ / A ₁ . Preferably, the time taken is the secondary electron beam over the entire area A _{2 of} the second microchannel plate 10 to take along, guide or judge, less than or equal to the time constant for individual channel recovery 2 after the irradiation.

The 9A and 9B show two-dimensional SIMION simulations in which the trajectories of a first microchannel plate 8th emitted secondary electrons 16 which are at a first time t ₁ ( 9A ) and a second later time t ₂ ( 98 ) to a second microchannel plate located further back 10 be accelerated. According to this embodiment, between the first microchannel plate 8th and the second microchannel plate 10 an electrostatic lens or electrode assembly 27 . 28 provided to the secondary electrons 16 on specific sections, areas or discrete areas of the second microchannel plate 10 to judge. The electrostatic lens 27 . 28 preferably has two or more electrodes 27 . 28 on that between the first microchannel plate 8th and the second microchannel plate 10 are arranged. The two or more electrodes 27 . 28 are preferably on opposite sides between the two microchannel plates 8th . 10 arranged. The distance between the electrodes 27 . 28 preferably takes from the first microchannel plate 8th to the second microchannel plate 10 to. If secondary electrons 16 on a portion, area or area of the second microchannel plate 10 are one or more sections, areas or areas of the second microchannel plate 10 preferably substantially free of incident secondary electrons 16 thereby allowing that portion, area or area of the microchannel plate 10 recovered and the individual channels 2 be replenished with electrons.

9A shows a SIMION simulation of the trajectories from the first microchannel plate 8th at a first time t ₁ emitted secondary electrons 16 , At the first time t ₁ becomes a first electrode 27 held at a potential which is preferably higher than that of the exit surface of the first microchannel plate 8th and which is preferably also lower than that of the entrance surface of the second microchannel plate 10 , At the same first time t ₁ becomes a second electrode 28 preferably maintained at a potential which is preferably lower than that of the first electrode 27 , and which is preferably also lower than the potential of the exit surface of the first microchannel plate 8th ,

The first microchannel plate 8th , the second microchannel plate 10 and the two intermediate electrodes 27 . 28 voltages applied to the first time t ₁ are preferably such that those from the first microchannel plate 8th emitted secondary electrons on a first portion, a first region or a first surface of the second microchannel plate 10 be directed or guided. Preferably, one or more further electrodes 25a . 25b which are preferably substantially coplanar with the first microchannel plate 8th are. These one or more additional electrodes 25a . 25b may preferably be at substantially the same potential as the exit surface of the first microchannel plate 8th held, although this one or more other electrodes 25a . 25b less preferably can be kept at a different potential. Similarly, one or more additional electrodes 29a . 29b which are preferably substantially coplanar with the second microchannel plate 10 are. These one or more additional electrodes 29a . 29b may preferably be at substantially the same potential as the entrance surface of the second microchannel plate 10 held, although this one or more other electrodes 29a . 29b less preferably can be kept at a different potential.

According to a particularly preferred embodiment, the to the electrodes of the electrostatic lens 27 . 28 applied potentials preferably changed over time, so that between the first microchannel plate 8th and the second microchannel plate 10 placed electric field from the first microchannel plate 8th emitted secondary electrons 16 at different times on different sections, areas or areas of the second microchannel plate 10 directs or leads. For example, that of the first microchannel plate 8th emitted electricity from secondary electrons 16 regularly and / or repeatedly between two, three, four, five, six, seven, eight, nine, ten or more than ten different sections, areas or areas of the second microchannel plate 10 be switched. The stream of secondary electrons 16 Alternatively, it may be analogously continuous over the second microchannel plate 10 be distracted or stepped over these, moved or rotated.

In the in the 9A and 9B particularly illustrated or illustrative simulations is the second microchannel plate 10 from the first microchannel plate 8th 32 mm apart and is maintained at a potential which is +1000 V higher than that of the exit surface of the first microchannel plate 8th , The first microchannel plate 8th can be held at 0 V and emits secondary electrons 16 of a preferably substantially circular area having a diameter of preferably 25 mm. The second microchannel plate 10 preferably has a detection surface for receiving the secondary electrons 16 which is preferably substantially circular and which preferably has a diameter of 50 mm.

At the first time t ₁ , the lens electrodes become 27 . 28 preferably at potentials of 900 V and -100 V with respect to the output surface of the first microchannel plate 8th held. In this simulation, the secondary electron trajectories are 16 for secondary electrons 16 shown from the first microchannel plate 8th exit and under one to the level of the first microchannel plate 8th vertical angle stand. The secondary electrons 16 have an initial energy of 20 eV. The marks on each electron trajectory 16 correspond to the positions of the secondary electrons 16 at successive time intervals of 1 ns.

9B shows the secondary electron trajectories 16 at a second later time t ₂ . At this second later time t ₂ , the to the lens electrodes 27 . 28 applied potentials vice versa, so that the secondary electrons 16 on a second different area, a second different area or a second different portion of the entrance surface of the second microchannel plate 10 be directed. As a result, it is possible that the area of the second microchannel plate 10 , which at first time t ₁ by the secondary electrons 16 was irradiated, recovered, so that the saturation of the detection system, the gain of the inner detector 7 not impaired.

10A shows a further embodiment, wherein a quadrupole rod set 31 is used to from the first microchannel plate 8th emitted secondary electrons 16 on discrete areas of the entrance surface of the second microchannel plate 10 to focus or guide, which preferably has a substantially circular receiving surface. A bias voltage V _B is preferably between the exit surface of the first microchannel plate 8th (which is preferably also circular) and the entrance surface of the second microchannel plate 10 uphold the secondary electrons 16 to the second microchannel plate 10 to accelerate. DC voltages V1, V2, V3, V4 can be applied to each rod of the quadrupole rod set 31 be created. The to the rods of the quadrupole rod set 31 applied voltages are preferably changed over time, so that the secondary electrons 16 over the entrance surface of the second microchannel plate 10 be distracted or turned over or around this. According to this embodiment, the secondary electrons 16 preferably in a substantially circular motion over substantially the entire surface of the second microchannel plate 10 to get distracted. Other embodiments are contemplated herein, where the electrons 16 for example, in a substantially stepwise, regular or erratic manner across the surface of the second microchannel plate 10 can be moved.

10B is a view along the axis of the quadrupole rod set 31 , According to this embodiment, the secondary electrons 16 on a discrete area of the second microchannel plate 10 directed, which then preferably over time around the entrance surface of the second microchannel plate 10 is scanned clockwise or counterclockwise. It is contemplated that other multipole lenses, such as hexapole or octapole rod sets or higher order rod sets, may be used in accordance with this embodiment.

11A shows a further embodiment, wherein the lens electrodes 27 ' . 28 ' between the first microchannel plate 8th and the second microchannel plate 10 are arranged. The first microchannel plate 8th and the second microchannel plate 10 are preferably circular, and the lens electrodes 27 ' . 28 ' are preferably arranged opposite to each other. The lens electrodes 27 ' . 28 ' direct those from separate channels or areas of the first microchannel plate 8th emitted secondary electrons 16 preferably on preferably substantially separate, preferably non-overlapping areas, areas or portions of the second microchannel plate 10 (or more generally, the detection device 9 ). The secondary electrons 16 in this way only irradiate a relatively small number or a relatively small part of the total number of channels on the second larger microchannel plate 10 , A dynamically varying, preferably relatively small electric field is preferably between the first microchannel plate 8th and the second microchannel plate 10 maintained by a time-changeable voltage (for example, AC voltage) to the lens electrodes 27 ' . 28 ' is created. The electric field causes the deflection or movement of the secondary electrons 16 so that the of the different channels or areas of the first microchannel plate 8th emitted secondary electrons 16 preferably at a first time t ₁ of a number of substantially non-overlapping regions on the second microchannel plate 10 and from a second different number of substantially non-overlapping areas to a second one later time t ₂ on the second microchannel plate 10 be received. This cycle is then repeated. This embodiment ensures that secondary electrons 16 resulting from successive ion arrivals at the first microchannel plate 8th within the recovery time of a single channel, to different areas of the second microchannel plate 10 be directed. As a result, in turn, the maximum output current of the inner detector 7 before it is limited by saturation, increases.

According to another embodiment, at least one of the lens electrodes 27 ' . 28 ' an annular electrode. The one or more annular electrodes may be supplied with a time varying voltage so that the electrons are diverged by a time varying amount or onto the detector 9 be focused.

11B shows an exemplary exemplary deflection voltage applied to the lens electrodes 27 ' . 28 ' can be applied to generate the dynamically changing electric field. The voltage is represented as a sine wave having a frequency of ≥ 1 / T, where T is less than or equal to the recovery time τ of a single channel of the microchannel plate 8th is.

According to another embodiment, the deflection voltage applied to the lens electrodes 27 ' . 28 ' can be applied to generate the dynamically changing electric field, applied intermittently. The rate or frequency with which the voltage is applied to the lens electrodes is preferably selected to ensure that secondary electrons 16 resulting from successive ion arrivals at the first microchannel plate 8th within the recovery time of a single channel, to different areas of the second microchannel plate 10 be directed.

12 shows a further embodiment similar to that in FIG 11A illustrated embodiment, but with a quadrupole rod set 31 ' is used to secondary electrons 16 from the exit surface of the first microchannel plate 8th on the entrance of the second microchannel plate 10 to focus and lead. According to this embodiment, small, dynamically changing voltages can be applied to the rods of a quadrupole rod set 31 ' be created between the first microchannel plate 8th and the second microchannel plate 10 is arranged. This embodiment ensures that secondary electrons 16 resulting from successive ion arrivals at the first microchannel plate 8th Do not cause secondary electrons 16 within the recovery time of a single channel to the same channels or areas of the second microchannel plate 10 be directed.

Although from the exit surface of the first microchannel plate 8th emitted secondary electrons 16 may have a relatively low sensitivity for magnetic fields, yet other embodiments are contemplated in which magnetic fields or combinations of magnetic and electrostatic fields are used to from the exit surface of the first microchannel plate 8th emitted secondary electrons 16 on the entrance surface of the second microchannel plate 10 or to focus, guide, or direct multiple microchannel plates with a combined larger surface area.

The 13A and 13B show a SIMION simulation of trajectories of secondary electrons 16 according to an embodiment in which both electrostatic fields and magnetic fields are used to generate secondary electrons 16 from the exit surface of the first microchannel plate 8th to the entrance surface of the second larger microchannel plate 10 respectively. According to this embodiment, the first microchannel plate 8th and the second microchannel plate 10 preferably arranged substantially coplanar. An accelerating plate or reflective electrode 30 is preferably at a distance from both the exit surface of the first microchannel plate 8th as well as from the entrance surface of the second microchannel plate 10 spaced provided. A uniform magnetic field with a direction substantially parallel to the surfaces of the first microchannel plate 8th and the second microchannel plate 10 runs, is preferably provided. The magnetic field causes that from the first microchannel plate 8th emitted secondary electrons 16 in a substantially circular direction from the exit surface of the first microchannel plate 8th to the entrance surface of the second microchannel plate 10 be accelerated.

According to an embodiment, the magnitude and direction of the magnetic field may be kept constant over time. That of the accelerating plate or the reflective electrode 30 however, voltage applied may preferably be changed over time. 13A shows the trajectories of secondary electrons 16 at a first time t ₁ when the potential difference between the first microchannel plate 8th and the second microchannel plate 10 and the acceleration plate 30 is held at such a value that the secondary electrons to a first surface, a first region or a first portion of the entrance surface of the second microchannel plate 10 be guided.

As in 13B is shown, the potential difference between the first microchannel plate 8th and the second microchannel plate 10 and the acceleration plate 30 at a second later time t _{2 is} preferably reduced so that the secondary electrons 16 to a second different area, a second different area, or a second different portion of the second microchannel plate 10 be guided. The cycle is then preferably repeated.

The potential difference between the accelerating plate or the reflective electrode 20 and the first microchannel plate 8th and the second microchannel plate 10 According to one embodiment, it can be changed continuously to the secondary electrons 16 over the entrance surface of the second microchannel plate 10 to take along or to move. Alternatively, the potential difference may be changed periodically or in other ways stepwise to the secondary electrons 16 between different areas, areas or portions of the entrance surface of the second microchannel plate 10 to switch, move or distract.

According to a preferred embodiment, the acceleration plate or electrode 30 held at a potential that is more positive than that of the exit surface of the first microchannel plate 8th and more positive than that of the entrance surface of the second microchannel plate 10 , The in relation to the 13A and 13B illustrated and described embodiment is particularly advantageous because the temporal broadening of the secondary electrons 16 at the entrance surface of the second microchannel plate 10 is minimized. This results in a minimal distortion of the final resolution of the interior detector 7 ,

According to another embodiment, this is applied to the accelerating plate or electrode 30 applied potential, preferably with respect to the exit surface of the first microchannel plate 8th and the second microchannel plate 10 kept constant, and the amount of the magnetic field is changed either continuously or periodically. According to this embodiment, the magnetic field can be changed to the secondary electrons 16 over the entrance surface of the second microchannel plate 10 or, less preferably, the secondary electrons 16 between different areas, areas or portions of the entrance surface of the second microchannel plate 10 to switch.

The 14A and 14B show a SIMION simulation of trajectories of secondary electrons 16 according to a further embodiment, wherein two detectors 23 . 24 preferably substantially symmetrical about the first microchannel plate 8th are arranged. The secondary electrons 16 coming from the output of the first microchannel plate 8th are emitted are preferably using a grid electrode 32 accelerated, which is arranged downstream of the first microchannel plate and which preferably at a constant positive potential with respect to the exit surface of the first microchannel plate 8th is held.

A magnetic field, preferably having a substantially constant amount, is preferably arranged to be substantially parallel to the exit face of the first microchannel plate 8th and to the entry surfaces of the detectors 23 . 24 runs. 14A shows the trajectories of the secondary electrons 16 at a first time t ₁ , wherein the magnetic field is arranged in a first direction to the secondary electrons 16 to the first detector 23 respectively. 14B shows the trajectories of the secondary electrons 16 at a second later time t ₂ , wherein the direction of the magnetic field has been reversed so that the secondary electrons 16 to the other detector 24 be guided. The cycle is then preferably repeated.

According to a further embodiment, a detection surface, which has more than two detectors, around the first microchannel plate 8th be arranged around. The detection surface may further preferably be substantially continuous. The direction of the magnetic field can preference, substantially continuously or alternatively be changed stepwise periodically to the secondary electrons 16 to divert, switch or rotate to different areas of the contiguous detector or to separate detectors.

It is also contemplated that in all the embodiments described above, the first microchannel plate 8th could be replaced by another type of device. For example, it could be ensured that ions 12 fall on any material, the secondary electrons 16 produced, such as boron-doped, by chemical vapor deposition ("CVD") generated diamond films. It can be ensured that these films ions 12 receive and generate secondary electrons in response thereto.

Although in the embodiments described above, the area of the detector 9 . 23 . 24 to which the secondary electrons 16 In fact, as described with respect to a microchannel plate, it may actually include any type of electron multiplier (eg, a photomultiplier tube or an electron multiplier tube).

Of the Interior detector according to the preferred embodiment can be used in conjunction with mass spectrometers at those pseudo-continuous internal sources or pulsed internal sources, such as Internal sources with a matrix-assisted laser desorption ionization ("MALDI") are used. The preferred embodiment is also applicable to mass spectrometers other than time-of-flight mass spectrometers for example, quadrupole, inside trapping and magnetic sector mass spectrometers, applicable.

Although the present invention with reference to preferred embodiments will be understood by those skilled in the art that various changes can be made on the form and the details, without from that in the appended claims to depart from the scope of the invention.

Claims (31)

An interior detector for use in a mass spectrometer, comprising: a microchannel plate ( 8th ), whereby in use ions ( 12 ) on an entry surface of the microchannel plate ( 8th ) and electrons ( 16 ) from an exit face of the microchannel plate ( 8th ), wherein the exit surface has a first surface, and one with a zigzag pair of microchannel plates ( 10 . 11 ) formed detection device ( 9 ) with a detection surface on which at least some of the microchannel plate ( 8th ) emitted electrons ( 16 ), wherein the detection surface has a second area that is larger than the first area and between the microchannel plate ( 8th ) and the detection device ( 9 ) Electrodes ( 17 ) are provided, by means of which an electric field is generated, so that from the microchannel plate ( 8th ) emitted electrons are diverged on the detection surface. An interior detector according to claim 1, wherein the one or the plurality of electrodes comprise one or more annular electrodes. An interior detector according to claim 1 or 2, wherein said one or the plurality of electrodes, one or more single lens arrays having three or more electrodes. An interior detector according to claim 1, 2 or 3, wherein said one or more electrodes segmented one or more sets of exhibit. Inner detector according to one of claims 1 to 4, wherein the one or more electrodes one or more tubular Include electrodes. Inner detector according to one of claims 1 to 5, wherein the one or more electrodes one or more Quadrupole, hexapole, octapole rod sets or higher order rod sets exhibit. Inner detector according to one of claims 1 to 6, wherein the one or more electrodes comprise a number of electrodes with openings include, of which electrons leaked in use be, with the openings essentially the same area exhibit. An interior detector according to any one of claims 1 to 7, wherein the one or more electrodes comprise a number of apertured electrodes from which electrons are transmitted in use, the apertures being to the detection device (10). 9 ) become progressively smaller or larger. Inner detector according to one of the preceding claims, wherein means for holding the exit surface of the microchannel plate ( 8th ) at a first potential and the detection surface of the detection device ( 9 ) are provided at a second potential. Inner detector according to one of claims 1 to 8, wherein means for retaining the exit surface of the microchannel plate on a first potential, the detection surface of the detection device at a second potential and one or more electrodes, disposed between the microchannel plate and the detection surface are provided at a third potential. Inner detector according to one of the preceding claims, which further one between the microchannel plate and the detection device having arranged grid electrode. An interior detector according to claim 11, wherein the grid electrode is hemispherical or otherwise is not planar. Inner detector according to one of the preceding claims, wherein the detection device ( 9 ): (i) an electron multiplier, (ii) a scintillator, (iii) a photomultiplier tube, or (iv) a plurality of microchannel plates ( 10 . 11 ). Inner detector according to one of the preceding claims, wherein the detection device ( 9 ) has a single detection area. Inner detector according to one of claims 1 to 13, wherein the detection device ( 9 ) has a first detection area and at least a second separate detection area. The interior detector of claim 15, wherein the second Detection area is spaced from the first detection area. An interior detector according to claim 15, wherein the first and the second detection area have the same detection areas. An interior detector according to claim 15, wherein the first and the second detection area has different detection areas. Inner detector according to one of the preceding claims, which further comprises at least one collector plate ( 15 ), which at least some of the detection device ( 9 ) receives emitted electrons. Inner detector according to claim 19, wherein the at least one collector plate ( 15 ) is shaped so that a temporal broadening of the time of flight of the incident on the detection device or incident electrons is at least partially compensated. Inner detector according to one of the preceding claims, wherein the detection device ( 9 ) is shaped so that a temporal broadening of the time of flight of the incident on the detection device electrons is at least partially compensated. Inner detector according to one of the preceding claims, which further comprises one or more electrodes, and a device, with which the electrodes are driven such that a temporal Widening of the time of flight of the incident on the detection device At least partially compensated electrons. An interior detector for use in a mass spectrometer, comprising: a microchannel plate ( 8th In use, particles are received on an entrance surface of the microchannel plate and electrons are received from an exit surface of the microchannel plate (FIG. 8th ), wherein the exit surface has a first surface, and a detection device ( 9 ) having a detection area having a second area larger than the first area, a first device ( 19 ) located between the microchannel plate ( 8th ) and the detection device ( 9 ), the first device ( 19 ) at least some of the exit surface of the microchannel plate ( 8th ) receives emitted electrons and generates photons, and a second device ( 21 ) between the first device ( 19 ) and the detection device ( 9 ), the second device ( 21 ) at least some of the first device ( 19 ) and emits electrons emitted by the detection surface of the detection device ( 9 ) are received. An interior detector for use in a mass spectrometer, comprising: a microchannel plate ( 8th ), wherein in use particles on an entrance surface of the microchannel plate ( 8th ) and electrons from an exit face of the microchannel plate ( 8th ), wherein the exit surface has a first surface, and a detection device ( 9 ) having a detection area having a second area larger than the first area, a first device ( 19 ) located between the microchannel plate ( 8th ) and the detection device ( 9 ), wherein the first device at least some of the exit surface of the microchannel plate ( 8th ) receives emitted electrons and generates photons, wherein the detection surface is at least some of that of the first device ( 19 ) received photoneu receives. Mass spectrometer with an interior detector, the a structure according to any one of the preceding claims. The mass spectrometer of claim 25, wherein the interior detector forms part of a time-of-flight mass analyzer. A mass spectrometer according to claim 25 or 26, which further comprising an analog-to-digital converter ("ADC") connected to the inner detector. Mass spectrometer according to claim 25, 26 or 27 which further has a time-to-digital converter connected to the inner detector ("TDC"). A method of detecting ions comprising the steps of: receiving ions at an entrance surface of a microchannel plate ( 8th ), Discharging electrons from an exit surface of the microchannel plate ( 8th ), wherein the exit surface has a first surface, diverging that of the microchannel plate ( 8th ) emitted electrons by means of an electric field which between the microchannel plate ( 8th ) and a detection device formed with a zigzag pair or chevron pair of microchannel plates ( 9 ), receiving at least some of the electrons on a detection surface of the detection device ( 9 ), wherein the detection surface has a second surface, wherein the second surface is larger than the first surface. A method of detecting particles comprising the steps of: receiving particles at an entrance surface of a microchannel plate ( 8th ), Discharging electrons from an exit surface of the microchannel plate ( 8th ), wherein the exit surface has a first surface, receiving at least some of the electrons on a first device ( 19 ), the first device ( 19 ) responsively generates photons, diverging those from the first device ( 19 ) emitting photons, receiving at least some of the photons on a second device ( 21 ), wherein the second device emits electrons in response thereto, and receiving at least some of the second device (s). 21 ) generated electrons on a detection device ( 9 ) having a detection surface with a second surface, wherein the second surface is larger than the first surface. A method of detecting particles comprising the steps of: receiving particles at an entrance surface of a microchannel plate ( 8th ), Discharging electrons from an exit surface of the microchannel plate ( 8th ), wherein the exit surface has a first surface, receiving at least some of the electrons on a device ( 19 ), the device ( 19 ) responsively generates photons, diverging those from the first device ( 19 ) emitting photons, receiving at least some of the device ( 19 ) generated photons on a detection surface of a detection device ( 9 ) having a second surface, wherein the second surface is larger than the first surface.