EP3035366A1 - Ft-icr mass spectrometer with icr measuring cell with a duplexer - Google Patents

Abstract

An ICR measuring cell (01) with a duplexer (08) with one or more semiconductor components (05, 06, 07) for use in an apparatus for FT-ICR mass spectrometry with a superconducting magnet for generating a magnetic field in the direction of a z-axis in which the duplexer is part of a transmitting and receiving device (09) of an FT-ICR mass spectrometry apparatus, which transmits the voltage of the transmitter (03) to at least one electrode (11) of the ICR measuring cell during an ion excitation phase Protects preamplifier (04) from overvoltage and on the other hand, during an ion detection phase, an ion receiving signal, namely the following from the influenzierten charge voltage of the same electrode via a receive path (12) transmits to the preamplifier, characterized in that in the receive path at least one active serial Switch (07) is used with two switchable states, each with different series impedances. Thus, a duplexer for the ICR measuring cell of an FT-ICR mass spectrometer is provided in which at least one electrode can be used both for ion excitation and then for ion detection, the duplexer used for this ensures the protection of the preamplifier from the excitation voltage and the signal-to-noise ratio is not significantly affected.

Description

The invention relates to an ICR measuring cell with a duplexer with one or more semiconductor components for use in an apparatus for FT-ICR - (= Fourier Transform - Ion Cyclotron Resonance) mass spectrometry with a, preferably superconducting, magnet for generating a magnetic field in the direction of a z Axis, wherein the duplexer is part of a transmitting and receiving device of a FT-ICR mass spectrometry apparatus, which transmits on the one hand during an ion excitation phase, the voltage of the transmitter via the transmitter path of the duplexer to at least one electrode of the ICR measuring cell, a preamplifier Protects anti-parallel connected diodes and a series impedance for current limitation against overvoltage and on the other hand during an ion detection phase, an ion receiving signal, namely the following from the influenzierten charge voltage of the same electrode transmits via a receiving path to the preamplifier.

Such an arrangement is known from Chen, T .; Kaiser, NK; Beu, SC; Hendrickson, CL and Marshall, Inc., Excitation and Detection with the Same Electrodes for Improved FT-ICR MS Performance, Proc. 60th ASMS Conf. on Mass Spectrometry & Allied Topics, Vancouver, Canada, May 20-24, 2012 (= Reference [2])
or off
Chen, T .; Kaiser, NK; Beu, S. C, Blakney GT, Quinn JP, Mclntosh, DG, Hendrickson, CL and Marshall, AG, Improving Radial and Axial Uniformity of the Excitation Electric Field in a Closed Dynamically Harmonized FT-ICR Cell, 61st Amer. Soc. Mass Spectrometry Conf., Minneapolis, MN, June 9-13, 2013 (= Reference [3])

introduction

Fourier transform ion cyclotron resonance (FT-ICR) is a high-resolution mass spectrometry technique.

Common cells for FT-ICR mass spectrometry are divided into cubic and cylindrical sections: a few opposing electrodes for ion excitation and another pair offset by 90 degrees for detection, as exemplified in FIG Fig. 2 (or Fig. 3a ). A further development attempts to improve this previous arrangement in that all electrodes are used for ion detection, specifically in that the electrode pair previously used only for the excitation is also used for the detection.

By adding the signals of all four electrodes, each with alternating phase (0 degrees, 180 degrees), a higher frequency resolution is achieved (actually a higher frequency is achieved with the FT-ICR Mass spectrometry corresponds to a higher mass resolution). This type of detection is known by the term harmonic detection method ( Fig. 3b ) (see reference [9]).

With such an arrangement, however, a better sensitivity (higher signal to noise ratio) can be achieved by in-phase addition of the signals, because during the entire circular path (cyclotron), an ion-receiving signal can be detected. In each case, the signals of two adjacent electrodes are added and the signals of the other two electrodes are subtracted ( Fig. 3c ) (see reference [8]).

A basic scheme of this known arrangement of electrode pairs is in Fig. 4a shown. A spatially opposed electrode pair (20 and 21) of an ICR measuring cell (01), with associated preamplifiers (04b and 04d), is used only for detection, while the second electrode pair (40 and 41), via the duplexer (08a and 08b ), either with the preamplifiers (04a and 04c) or the transmitters (03a and 03b, here shown as two individual transmitters, but in practice a single transmitter with a 0/180 degree splitter is often used) for ion excitation , From this arrangement, four freely combinable receive paths and two transmitter paths result for different applications.

A single path, with a common for excitation and detection electrode (11) is in the Figures 4b and 4c mapped for the excitation and detection case. A single duplexer off Fig. 4a (08a or 08b) consists essentially of two switching paths S1 and S2 ( Figures 4b and 4c , 42 and 43). During the ion excitation phase, S1 (42) is closed or conductive and S2 (43) is open or blocking, and vice versa during the ion detection phase.

In the closed state, S1 transmits the ion excitation voltage to the common electrode and, in the blocking state, ensures that the detected ion received signal is not attenuated. S2 protects in the blocking state, the subsequent preamplifier before the high ion excitation voltage and transmits in the conductive state, the ion received signal.

application requirements

1. 1. Um eine größere Frequenzauflösung zu erreichen (Harmonisches-Detektionsverfahren, Fig. 3b), muss mindestens ein Elektrodenpaar für Senden und Empfang ausgelegt sein und die Ionen-Empfangssignale müssen geeignet kombiniert werden.
2. 2. Um das Signal- zu Rauschverhältnis während der lonen-Detektionsphase zu maximieren, muss S2 (43, Vorverstärkerschutz während der Ionen-Anregungsphase, Figuren 4b und 4c), ein möglichst ideales Leitverhalten haben.
   Zusätzlich muss eine eventuell vorhandene elektrische Kapazität vom Empfangspfad (12) gegen die Schaltungsmasse (13) minimiert und ein eventuell vorhandener Parallelwiderstand gegen die Schaltungsmasse maximiert werden.
3. 3. Um den Schutz des Vorverstärkers während der Ionen-Anregungsphase sicherzustellen, muss S2 eine genügend große Sperrdämpfung und Spannungsfestigkeit haben.
4. 4. Um das Signal- zu Rauschverhältnis während der lonen-Detektionsphase zu maximieren, muss S1 (42, Übertragung der lonen-Anregungsspannung auf die gemeinsame Elektrode (11), (Figuren 4b und 4c), eine möglichst ideale Sperrdämpfung haben.
5. 5. Der Widerstand von S1 (Figuren 4b und 4c) bildet im leitenden Zustand mit der ICR-Zellenkapazität (Fig. 5, Detail 51) einen Tiefpass und muss demzufolge niederohmig sein um den Frequenzgang der lonen-Anregungsspannung nicht zu beeinflussen.
6. 6. Der Duplexer mit seinen Schaltpfaden S1 und S2 muss genügend schnell zwischen seinen beiden Grundzuständen wechseln können, damit die Funktionalität eines Umschalters zwischen Anregung und Detektion gewährleistet ist.

The aim of such an arrangement is to achieve the greatest possible signal-to-noise ratio, and / or the largest possible frequency resolution, if possible without affecting or restricting any other system properties. Here are the key points that need to be met by the application:

1. 1. In order to achieve a greater frequency resolution (harmonic detection method, Fig. 3b ), at least one electrode pair must be designed for transmission and reception, and the ion reception signals must be suitably combined.
2. 2. In order to maximize the signal-to-noise ratio during the ion detection phase, S2 (43, preamp protection during the ion excitation phase, Figures 4b and 4c ), have the best possible lead behavior.
   In addition, a possibly existing electrical capacitance from the receiving path (12) must be minimized against the circuit ground (13) and a possibly existing parallel resistance to the circuit ground can be maximized.
3. 3. In order to ensure the protection of the preamplifier during the ion excitation phase, S2 must have a sufficiently large stopband attenuation and dielectric strength.
4. 4. In order to maximize the signal-to-noise ratio during the ion detection phase, S1 (42, transfer of the ion excitation voltage to the common electrode (11), ( Figures 4b and 4c ), have the best possible stop attenuation.
5. 5. The resistance of S1 ( Figures 4b and 4c ) forms in the conducting state with the ICR cell capacity ( Fig. 5 , Detail 51) has a low-pass filter and must therefore be low-impedance in order not to influence the frequency response of the ion excitation voltage.
6. 6. The duplexer with its switching paths S1 and S2 must be able to change sufficiently fast between its two basic states, so that the functionality of a switch between excitation and detection is ensured.

Requirements for the realization

1. 1. Das Hauptproblem der Realisierung liegt in der hochohmigen Quellenimpedanz der ICR-Zelle, welche nach einem Vorverstärker mit minimaler äquivalenter Rauschstromquelle verlangt. Der Duplexer darf dieses hochohmige System nicht störend belasten (Fig. 5).
2. 2. Wenn der Vorverstärkerschutz durch einen geschalteten Pfad S2 (Figuren 4b und 4c) realisiert wird, muss unter allen Umständen die Betätigung des Schalters sichergestellt werden um den Vorverstärker vor der Ionen-Anregungsspannung zu schützen.
3. 3. Um die verbesserten Eigenschaften einer ICR-Messzelle mit einem gemeinsamen Elektrodenpaar für Ionen-Anregung und Detektion nutzen zu können, ist es vorteilhaft, dass der nachgeschaltete Vorverstärker ein an die Quellenimpedanz der Zelle angepasstes, möglichst rauscharmes Verhalten hat. Für dieses Verhalten wird in der Literatur oft der Begriff "Rauschanpassung" verwendet.

Here are the key points to be met in a concrete implementation:

1. 1. The main problem of implementation resides in the high impedance source impedance of the ICR cell, which requires a preamplifier with a minimum equivalent noise current source. The duplexer must not disturb this high-impedance system ( Fig. 5 ).
2. 2. If the preamp protection by a switched path S2 ( Figures 4b and 4c ), the actuation of the switch must be ensured under all circumstances to protect the preamplifier from the ion excitation voltage.
3. 3. In order to be able to use the improved properties of an ICR measuring cell with a common electrode pair for ion excitation and detection, it is advantageous for the downstream preamplifier to have as low-noise a behavior as possible adapted to the source impedance of the cell. For this behavior, the term "noise fit" is often used in the literature.

State of the art overall arrangement

The published in reference [1] electronic circuit describes in great detail the current state of the preamplifier technique for FT-ICR mass spectrometry as it is often used today, but without a duplexer. From this work it is clear which parameters are essential for a preamp design. It is inferred in detail that for maximum signal-to-noise ratio, the total input capacitance (51), consisting of the electrode capacitance, the supply capacitance to the preamplifier, the input capacitance of the preamplifier and other parasitic capacitances, must be minimized, the entire parallel resistor (52), which in turn consists of the input resistance of the preamplifier, the leakage resistance for electrodes DC potentials and other parallel losses, but must be maximized.

With such an arrangement, it is undoubtedly possible to achieve from a single electrode pair the best possible signal-to-noise ratio with today's technologies (apart from a conceivable cryogenic preamplifier, with which the noise could be further reduced). However, this system can only be used for ion detection, since the other pair of electrodes is required for ion excitation, which consequently precludes certain applications, such as, for example, the harmonic detection method and / or further sensitivity increase by means of in-phase combination of the received signals ( see reference [8]).

Fig. 2 shows this prior art according to reference [4]. This general construction of a conventional ICR cell, as used in majority in commercially available FT-ICR mass spectrometry apparatus, includes two electrodes (22 and 23) for ion excitation and two electrodes (20 and 21) for ion detection. The ion excitation voltage comes from two transmitters (03a and 03b, here shown as two individual transmitters, but in practice a single transmitter with a 0/180 degree splitter is often used) and the detected ion receive signal is received from two preamplifiers (04a and 04b, shown here as two preamplifiers, usually implemented as a single preamplifier with differential input) amplified as low noise as possible.

1. a) S1: Allen bekannten Umsetzungen des beschriebenen Prinzips in den Figuren 4b und 4c ist gemeinsam, dass für S1 (42) ein antiparalleies Diodenpaar (Fig. 6, Detail 05) eingesetzt wird.
   Die Ionen-Anregungsspannung ist um ein mehrfaches größer als die Dioden-Flussspannung und jede Halbwelle kann die Dioden nahezu ohne Verluste passieren.
   Dem gegenüber ist das detektierte Ionen-Empfangssignal um ein mehrfaches kleiner als die Dioden-Flussspannung und die Dioden wirken wie ein sperrender Schalter auf das Signal.
2. b) S2: Um den Vorverstärker vor der Ionen-Anregungsspannung zu schützen, wird ein Spannungsteiler eingesetzt, bestehend aus einem Blindwiderstand in Serie zum Vorverstärkereingang (in der publizierten Variante ist das eine Seriekapazität, siehe Fig. 6, Detail 60) und mehreren antiparallelen Diodenpaare (Fig. 6, Detail 06 aus Referenz [2]) parallel zum Vorverstärkereingang. Die Diodenpaare begrenzen dabei die maximal am Vorverstärkereingang anliegende Wechselspannung während der Phase der Ionen-Anregung. Der Strom in der Anordnung wird dabei von der Dimensionierung der Seriekapazität bestimmt (Zahlenbeispiel mit folgenden Annahmen: 200m/z Masse-zu-Ladung-Verhältnis, 21 Tesla Magnet, Frequenz der Ionen-Anregungsspannung ungefähr 1.6 MHz mit einer Spitzenspannung von 200 V. Bei einer Seriekapazität von 1 nF fließt ein Spitzenstrom von nahezu 2 A in der Seriekapazität, beziehungsweise ungefähr 1 A pro Diode). Die Strombegrenzung durch eine Kapazität hat den Vorteil, dass der Blindwiderstand einer Kapazität, im Vergleich zu einem gleich großen realen Widerstand, nicht rauscht. Je nach Wahl dieser Kapazität hat diese Anordnung folgende Eigenschaften:
   1. a. Das maximal erzielbare Signal- zu Rauschverhältnis während der Ionen-Detektionsphase ist stark beeinflusst durch einen weiteren Spannungsteiler, bestehend aus der Seriekapazität (60), den parasitären Kapazitäten der Diodenpaare (Zahlenbeispiel: 4x C_D@0V von ungefähr 1.5 pF ergibt 6 pF) und der parasitären Eingangskapazität (Zahlenbeispiel: C_i ungefähr 10 pF) des Vorverstärkers (zusammengefasst Cp in 61).
      Ein kleiner Wert der Seriekapazität bedeutet einen hohen Blindwiderstand und reduziert somit die notwendige Stromtragfähigkeit der Dioden parallel zum Vorverstärkereingang (Ionen-Anregungsphase), teilt aber das detektierte Ionen-Signal stark hinunter und verschlechtert damit das mit der Anordnung erzielbare Signal- zu Rauschverhältnis (Ionen-Detektionsphase).
   2. b. Bei einem großen Wert der Seriekapazität (60) hat der entstehende Spannungsteiler praktisch keinen Einfluss auf das maximal erzielbare Signal- zu Rauschverhältnis. Dafür fließt während der Ionen-Anregungsphase ein viel größerer Strom durch die Diodenpaare (06). Für einen sicheren Betrieb müssen Dioden gewählt werden, welche für einen höheren Strom ausgelegt sind oder der höhere Strom muss auf noch mehr Diodenpaare verteilt werden. Dioden mit einer größeren Stromtragfähigkeit besitzen eine größere Chip-Fläche und damit eine größere parasitäre Kapazität (Niederfrequenz Dioden Kleinsignalmodell in Fig. 7, Detail 73). Gleichzeitig wird auch der parasitäre Dioden Parallelwiderstand (70) kleiner. Beides hat zur Folge, dass das maximal erzielbare Signal- zu Rauschverhältnis reduziert wird.
      Eine Verteilung des höheren Stromes auf mehr Diodenpaare (siehe Referenz [2]) hat den gleichen Effekt, da die gesamte Chip-Fläche aller Dioden größer wird.

In an ICR measuring cell with a common pair of electrodes for ion excitation and detection, to minimize the total input capacitance and maximize the entire parallel resistor, even the preamp protection is added. There are hardly any published articles in which this topic is taken up. The following are the features of reference [2] and [3] ( Fig. 6 ) Published circuit. A distinction is made between the conversion for the switching paths S1 and S2 ( Figures 4b and 4c , 42 and 43).

1. a) S1: all known reactions of the described principle in the Figures 4b and 4c is common that for S1 (42) an antiparaleies Diode pair ( Fig. 6 , Detail 05) is used.
   The ion excitation voltage is several times greater than the diode forward voltage, and each half wave can pass the diodes with virtually no loss.
   On the other hand, the detected ion received signal is several times smaller than the diode forward voltage and the diodes act as a blocking switch on the signal.
2. b) S2: In order to protect the preamplifier from the ion excitation voltage, a voltage divider is used, consisting of a reactance in series with the preamplifier input (in the published version this is a series capacitance, see Fig. 6 , Detail 60) and a plurality of antiparallel diode pairs ( Fig. 6 , Detail 06 from reference [2]) parallel to the preamplifier input. The diode pairs limit the maximum voltage applied to the preamplifier input during the phase of ion excitation. The current in the array is determined by the sizing of the series capacitance (numerical example with the following assumptions: 200m / z mass-to-charge ratio, 21 Tesla magnet, frequency of ion excitation voltage about 1.6 MHz with a peak voltage of 200V a series capacitance of 1 nF flows a peak current of nearly 2 A in the series capacitance, or approximately 1 A per diode). The current limitation by a capacity has the advantage that the reactance of a capacitance, compared to an equal-sized real resistance, does not rustle. Depending on the choice of this capacity, this arrangement has the following properties:
   1. a. The maximum achievable signal-to-noise ratio during the ion detection phase is strongly influenced by another voltage divider, consisting of the series capacitance (60), the parasitic capacitances of the diode pairs (numerical example: 4x C _{D @ 0V} of approximately 1.5 pF gives 6 pF) and the parasitic input capacitance (numerical example: C _i approximately 10 pF) of the preamplifier (summarized Cp in FIG. 61).
      A small value of the series capacitance means a high reactance and thus reduces the necessary current carrying capacity of the diodes in parallel to the preamplifier input (ion excitation phase), but greatly divides the detected ion signal and thus deteriorates the achievable with the arrangement signal to noise ratio (ion detection phase).
   2. b. With a large value of the series capacitance (60), the resulting voltage divider has practically no influence on the maximum achievable signal-to-noise ratio. For this, a much larger current flows through the pairs of diodes (06) during the ion excitation phase. For safe operation, diodes must be chosen which are designed for a higher current or the higher current must be distributed over even more pairs of diodes. Diodes with a larger current carrying capacity have a larger chip area and thus a larger parasitic capacitance (low frequency diodes small signal model in Fig. 7 , Detail 73). At the same time, the parasitic diode parallel resistor (70) becomes smaller. Both have the consequence that the maximum achievable signal-to-noise ratio is reduced.
      Distributing the higher current to more pairs of diodes (see reference [2]) has the same effect as the total chip area of all diodes increases.

Another feature of the circuit published in references [2] and [3] is the leakage resistance ( Fig. 6 , Detail 10) of the excitation and detection common electrode (11) against circuit ground (13). The leakage resistor derives possible electrical charges from the electrode and generates the DC reference potential for the ICR measuring cell and is advantageously chosen to be as high-impedance as possible for the signal-to-noise ratio.

Object of the invention

The object of the present invention is to provide a duplexer for the ICR measuring cell of an FT-ICR mass spectrometer, in which at least one electrode can be used both for ion excitation and then for ion detection, the duplexer used for this purpose providing protection of the preamplifier before the excitation voltage and does not significantly affect the signal-to-noise ratio.

Brief description of the invention

This object is achieved in an equally simple and effective manner in that at least one active serial switch is used in the receiving path as part of the duplexer, which is in series with the input of the preamplifier, can be activated by a control electronics, two activatable states, each with different series. Has impedances, and which the ion received signal in the case of reception by its low-impedance series impedance over the receiving path lossless as possible on the preamplifier and protects the preamplifier in the transmitter case by its high impedance series impedance and the anti-parallel diodes.

The duplexer used may be equipped with one or more semiconductor components and is intended for use in an apparatus for FT-ICR mass spectrometry. This preferably has a superconducting magnet for generating a magnetic field in the direction of a z-axis.

The duplexer is to be regarded as part of a transmitting and receiving device of an FT-ICR mass spectrometry apparatus, which transmits, on the one hand during the ion excitation phase, the voltage of the transmitter to at least one electrode of the ICR measuring cell, the preamplifier by antiparallel connected diodes and a series Protects impedance for current limiting against overvoltage and on the other hand, during the ion detection phase, the ion receiving signal, namely the following from the influenzierten charge voltage of the same electrode transmits via the receiving path of the duplexer to the preamplifier.
The duplexer according to the invention is characterized in that in the receiving path at least one active serial switch with two switchable states, each with different series impedances is used.

In preferred embodiments of the invention, the series impedance of the active serial switch has a low-impedance real part of less than 30 ohms during the ion-detection phase and a high-impedance of more than 1 kilo-ohms during the ion excitation phase.

Further embodiments are characterized in that during the ion detection phase of the active serial switch has a capacity of less than 1.5 pF from the receiving path against circuit ground and against the control electronics and / or an impedance of more than 1 giga-ohms from the receiving path against circuit ground and against having the control electronics.

Also advantageous are embodiments in which an optically controllable switch is used as the active serial switch in the reception path.

Alternatively or additionally, in further embodiments of the invention, the active serial switch without activation can have a high-impedance impedance.

Particularly preferred embodiments of the ICR measuring cell according to the invention, in which the protection of the preamplifier in the receiving path, an active serial switch in combination with subsequently one or more diode pairs and / or diode pairs with less than 0.2 pF per diode and / or diode pairs, which shunt resistors in the range of more than 4 giga-ohms per diode are used.

Also advantageous are embodiments in which diode pairs are used for transmitting the ion excitation voltage to the ICR measuring cell, which have less than 0.2 pF per diode and / or shunt resistors in the range of more than 4 giga-ohms per diode.

The duplexer preferably consists of a low-capacitance and high-resistance circuit (C _iso typical 0.8 pF and R _iso greater than 1 giga-ohm), in particular optical active serial switch, for example, carried out by a PhotoMOS relay (embodiment of a solid-state relay, see Reference [5]). Also conceivable is a design as MEMS (see reference [6]) or MOEMS (see reference [7]), with a subsequent antiparallel diode pair at the preamplifier input and with an antiparallel diode pair for transmitting the ion excitation voltage.

During the ion excitation phase, the active serial switch disables and may approximate as an electrical impedance consisting of an electrical resistance (approximately 100 megohms) and a resistance parallel capacity (approximately 35 pF). Since the preamplifier input impedance also has a high-impedance character, the antiparallel diode pair at the input is necessary to limit the voltage generated at the preamplifier input to the diode forward voltage. However, due to the blocking or high-resistance active serial switch, the current through the diodes is massively limited

A numerical example with the following assumptions: 200m / z mass-to-charge ratio, 21 Tesla magnet, frequency of ion excitation voltage about 1.6MHz with a peak voltage of 200V. Through a single diode flows a peak current of about 70mA.

During the ion detection phase, the active serial switch will conduct and the signal will pass unimpeded to the preamplifier input. In the on state, the series resistance should be small (below 30 ohms) so that its thermal noise does not interfere with overall performance and is thus somewhat below the noise of the preamplifier.

The active serial switch is self-blocking during the ion excitation phase and must be actively actuated for ion detection. The active serial switch is characterized in this particular embodiment in that its activation takes place by means of an optical transmission of the control signal. Thus, the influences of the signal-to-noise ratio harmful parasitic capacitance (C _iso typically 0.8 pF), and the parasitic resistance (R _iso greater than 1 Giga-Ohm), from the receive path to the control electronics and circuit ground, as otherwise for each semiconductor switch with more as two goals, reduced to a minimum.

Only the advantage of an active serial switch with two different resistance states for ion excitation and ion detection, also allows the use of diode pairs with a very small (less than 0.2 pF per diode) parasitic parallel capacitance ( Fig. 7 , 73, single diode) and a parasitic shunt resistor (70, single diode) in the range of more than 4 giga-ohms per diode. Typically, GaAs PIN diodes are suitable.

1. a) Speziell für ICR-Zellen mit vier Elektroden und mehr ist diese erfindungsgemäße Lösung vorteilhaft um mit zwei Elektrodenpaaren durch eine geeignete Addition der Ionen-Signale aller Elektroden das Signal- zu Rauschverhältnis weiter zu verbessern. Zusätzlich ist bei ICR-Zellen mit zwei Elektrodenpaaren eine Quadraturdetektion möglich, mit welcher die Spektren von positiven und negativen Ionen separiert werden können (siehe Referenz [8]).
2. b) Weiter bringt diese erfindungsgemäße Lösung Vorteile beim Harmonischen-Detektionsverfahren zur Steigerung der Frequenzauflösung je nach Art der Kombination der Ionen-Signale kann entweder die das Signal- zu Rauschverhältnis oder die Frequenzauflösung gesteigert werden (siehe Referenzen [8] und [9]).
3. c) Diese erfindungsgemäße Lösung ist, zusammen mit dem Vorverstärker, außerhalb und auch innerhalb des Vakuums, in unmittelbarer Nähe einer ICR-Zellen Elektrode, einsetzbar. Der Einsatz innerhalb des Vakuums ist besonders interessant, weil auf diese Weise die parasitäre Kapazität der Vakuum-Signaldurchführung (ungefähr 6 pF), durch Weglassung derselben, weiter optimiert und damit das Signal- zu Rauschverhältnis gesteigert werden kann.
4. d) Diese erfindungsgemäße Lösung ist bei Raumtemperatur und auch bei kryogenen Bedingungen unterhalb von 100K einsetzbar.

The inventive solution described above opens up new possibilities to realize systems with better performance for FT-ICR mass spectrometry equipment.

1. a) Especially for ICR cells with four electrodes and more, this solution according to the invention is advantageous for further improving the signal-to-noise ratio with two electrode pairs by a suitable addition of the ion signals of all the electrodes. In addition, quadrature detection is possible with ICR cells with two pairs of electrodes, with which the spectra of positive and negative ions can be separated (see reference [8]).
2. b) Furthermore, this solution according to the invention offers advantages in the harmonic detection method for increasing the frequency resolution, depending on the type of combination of the ion signals, either the signal-to-noise ratio or the frequency resolution can be increased (see references [8] and [9]).
3. c) This solution according to the invention, together with the preamplifier, can be used outside and also within the vacuum, in the immediate vicinity of an ICR cell electrode. The use within the vacuum is particularly interesting because in this way the parasitic capacity of the vacuum signal feedthrough (approximately 6 pF), by omission of the same, further optimized and thus the signal-to-noise ratio can be increased.
4. d) This solution according to the invention can be used at room temperature and also under cryogenic conditions below 100K.

Of course, other variations not described are possible, which can be realized by the skilled person.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, according to the invention, the above-mentioned features and those which are further developed can each be used individually for themselves or for a plurality of combinations of any kind. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Detailed description of the invention and drawing

Fig. 1

eine Ausführungsform der erfindungsgemäßen Vorrichtung;

Fig. 2

eine prinzipielle schematische Übersicht einer FT-ICR-Massenspektrometrie Apparatur mit für Anregung und Detektion getrennten Elektroden nach dem Stand der Technik;

Fign. 3a-c

eine vergleichende Prinzip Darstellung des konventionellen Detektionsverfahren mit dem Harmonischen-Detektionsverfahren nach dem Stand der Technik;

Fign. 4a-c

eine prinzipielle schematische Übersicht einer FT-ICR-Massenspektrometrie Apparatur mit für Anregung und Detektion gemeinsamen Elektroden nach dem Stand der Technik;

Fig. 5

ein vereinfachtes elektrisches Ersatzschaltbild eines Elektrodenpaares einer ICR-Zelle nach dem Stand der Technik;

Fig. 6

eine schematische Übersicht einer FT-ICR-Massenspektrometrie Apparatur mit für Anregung und Detektion gemeinsamen Elektroden, wie sie in [2] und [3] publiziert wurde nach dem Stand der Technik; und

Fig. 7

ein Niederfrequenz Kleinsignalmodell einer einzelnen Diode nach dem Stand der Technik.

The invention is illustrated in the drawing and will be explained in more detail with reference to embodiments. Show it:

Fig. 1

an embodiment of the device according to the invention;

Fig. 2

a schematic schematic overview of a FT-ICR mass spectrometry apparatus with separated for excitation and detection electrodes according to the prior art;

FIGS. 3a-c

a comparative principle diagram of the conventional detection method with the harmonic detection method according to the prior art;

FIGS. 4a-c

a schematic schematic overview of a FT-ICR mass spectrometry apparatus with electrodes common for excitation and detection according to the prior art;

Fig. 5

a simplified electrical equivalent circuit diagram of an electrode pair of an ICR cell according to the prior art;

Fig. 6

a schematic overview of a FT-ICR mass spectrometry apparatus with common for excitation and detection electrodes, as published in [2] and [3] according to the prior art; and

Fig. 7

a low-frequency small-signal model of a single diode according to the prior art.

FIG. 1 1 illustrates an embodiment of the inventive duplexer 08 with the ICR measuring cell 01 for an FT-ICR mass spectrometry apparatus, wherein the duplexer is to be viewed as part of a transmitting and receiving device 09. This embodiment of the duplexer is further characterized by the use of a PhotoMOS relay as an active serial switch 07 in series with the preamplifier, which protects the preamplifier, together with the anti-parallel diode pair 06 from the ion excitation voltage and its activation by means of a Steuerelektonik 02 takes place. <B> LIST OF REFERENCES: </ b> ICR measuring cell 01 control electronics 02 Amplifier for the ion excitation voltage 03 Preamplifier for the detected ion received signal 04 Antiparallel diode pair for the transmission of the ion excitation voltage 05 Antiparallel diode pair for voltage limitation 06 Active serial switch 07 duplexer 08 Transceiver 09 Bleeder resistance for electrodes DC potential 10 Single electrode of an ICR cell 11 receive path 12 circuit ground 13 transmitter path 14 Z-axis, axial to the ICR measuring cell 15 Ion detection electrode 90 degrees 20 Ion detection electrode 270 degrees 21 Ion excitation electrode 0 degrees 22 Ion excitation electrode 180 degrees 23 Ion excitation source 30 differential amplifier 31 summing 32 ion excitation / detection electrode 0 degrees 40 Ion excitation / detection electrode 180 degrees 41 S1: switching path for ion excitation voltage 42 S2: switching path for the detected ion received signal 43 Power source in the ICR cell equivalent circuit diagram 50 Parallel connection of the ICR cell capacity, preamplifier input capacitance and parasitic capacitances on the receive path 51 Parallel connection of bleeder resistor for electrodes DC potential, preamplifier input resistance (eg due to supply lead) and parasitic resistances on the receive path 52 series capacitance 60 Parasitic parallel capacitance consisting of the diode capacitance and the preamplifier input capacitance 61 Parallel resistance of a single diode caused by leakage currents 70 Track resistance of a single diode 71 Differential resistance of a single diode 72 Parallel capacity of a single diode 73

References

1. [1] Mathur, R .; Knepper, RW; O'Connor, PB, A Low Noise, Wideband Preamplifier for a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer, Journal of the American Society for Mass Spectrometry, December 2007, Volume 18, Issue 12, pp 2233-2241 ,
2. [2] Chen, T .; Kaiser, NK; Beu, SC; Hendrickson, CL and Marshall, Inc., Excitation and Detection for the Same Electrodes for Improved FT-ICR MS Performance, Proc. 60th ASMS Conf. on Mass Spectrometry & Allied Topics, Vancouver, Canada, May 20-24, 2012 ,
3. [3] Chen, T .; Kaiser, NK; Beu, S. C., Blakney GT, Quinn JP, McIntosh, DG, Hendrickson, CL and Marshall, AG, Improving Radial and Axial Uniformity of the Excitation Electric Field in a Closed Dynamically Harmonized FT-ICR Cell, 61st Amer. Soc. Mass Spectrometry Conf., Minneapolis, MN, June 9-13, 2013 ,
4. [4] Dunnivant, FM, Fourier Transform Ion Cyclotron - Mass Spectrometry, URL http://people.whitman.edu/~dunnivfm/C_MS_Ebook/CH5/5_5_6.html, accessed June 24, 2014 ,
5. [5] Wikipedia, Relaytypes, section Solid-state relay, URL http://en.wikipedia.org/wiki/Relay, accessed July 7, 2014 ,
6. [6] Wikipedia, Microelectromechanical Systems, URL http://en.wikipedia.org/wiki/Microelectromechanical_systems, accessed 17 July 2014 ,
7. [7] Wikipedia, Micro-Opto-Electro-Mechanical Systems, URL http://en.wikipedia.org/wiki/Micro-Opto-Electro-Mechanical_Systems, accessed on 17 July 2014 ,
8. [8th] Schweikhard, L .; Drader, JJ; Shi, SD-H .; Hendrickson, CL and Marshall, Inc., Quadrature Detection for the Separation of Positive and Negative Ions in Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, AIP Conf. Proc. 606, 647-651, 2002
9. [9] Marshall, AG; Hendrickson, CL, Fourier transform ion cyclotron resonance detection: principles and experimental configurations, International Journal of Mass Spectrometry 215, 59-75, 2002

Claims (14)

FT-ICR (= Fourier Transform - Ion Cyclotron Resonance) mass spectrometer comprising a cylindrically symmetric ICR measuring cell (01) and a transceiver device (09) comprising a duplexer (08) with one or more semiconductor components (05, 06, 07) comprises, with a, preferably superconducting, magnets for generating an ion on cyclotron trajectories magnetic field in the direction of a cylindrically symmetric ICR measuring cell (01) axial z-axis (15), wherein the duplexer (08) during an ion excitation phase the Voltage of the transmitter (03) via the transmitter path (14) of the duplexer (08) to at least one electrode (11) of the ICR measuring cell (01) transmits, protects a preamplifier (04) by anti-parallel connected diodes (06) from overvoltage and on the other hand during an ion-detection phase, an ion-receiving signal, namely the voltage of the same electrode (11) following from the induced charge, via the receiving path (12) of the duplexer (08) to the preamplifier he (04) transmits,
characterized,
in that in the receiving path (12) at least one active serial switch (07) is inserted as part of the duplexer (08), which is in series with the input of the preamplifier (04), can be activated by an electronic control unit (02),
has two activatable states, each with different series impedances, one of which is a high-impedance, the other low-impedance, and which the ion received signal in the case of reception by its low-impedance series impedance via the receiving path (12) loss or loss as possible on the preamplifier ( 04) and in the transmission case by its high-impedance series impedance and by the anti-parallel diodes (06) protects the preamplifier (04). Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, characterized in that by appropriate design of the active serial switch (07), the series impedance a low-impedance real part of less than 30 ohms during the Ion detection phase and a high impedance of more than 1 kilo-ohm during the ion excitation phase has. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claim 2, characterized in that by appropriate design of the active serial switch (07) during the ion detection phase of Active serial switch (07) has a capacity of less than 1.5 pF from the receiving path (12) against circuit ground (13) and against the control electronics (02) and / or an impedance of more than 1 giga-ohms from the receiving path (12) against circuit ground ( 13) and against the control electronics (02). Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 and / or 3, characterized in that as an active serial switch (07) in the receiving path (12) optically controllable switch is used. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 to 4, characterized in that by appropriate design of the active serial switch (07) and its implementation in the duplexer (08) the active serial switch (07) without control has a high impedance. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 to 5, characterized in that for the protection of the preamplifier (04)
in the receive path (12) the active serial switch (07) in combination with one or more of the input voltage of the preamplifier (04) limiting diode pairs (06) or diode pairs (06) with less than 0.2 pF per diode and / or diode pairs (06) which have shunt resistances in the range of more than 4 giga-ohms per diode,
is used. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 to 6, characterized in that as a switch for the transmission of the ion excitation voltage to the ICR measuring cell ( 01), via the transmitter path (14), diode pairs (05) are used as part of the duplexer (08), the
less than 0.2 pF per diode.
and / or shunt resistors in the range of more than 4 giga-ohms per diode
exhibit. Duplexer (08) according to claim 6, characterized in that are used as diode pair (06) directly at the input of the preamplifier (04) GaAs PIN diodes for preamplifier protection. Duplexer (08) according to claim 7, characterized in that are used as diode pair (05) for the transmission of the ion excitation voltage to the ICR measuring cell electrodes GaAs PIN diodes. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 to 9, characterized in that two or more electrodes of an ICR measuring cell (01) each having a duplexer (08) with an active serial switch (07) are equipped. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 to 10, characterized in that the duplexer (08) in the immediate vicinity of an electrode within a vacuum of the ICR measuring cell (01) is located. Duplexer (08) for the ICR measuring cell (01) of an FT-ICR mass spectrometer according to claim 1, optionally with features of claims 2 to 11, characterized in that as an active serial switch (07)
in the reception path (12) a MEMS switch (= microelectromechanical systems)
or a MOEMS switch (= microoptoelectromechanical systems) is used. Method for operating a duplexer (08) according to one of Claims 2 to 12, characterized in that the duplexer (08) together with the preamplifier (04)
with appropriate configuration of the semiconductor components in the duplexer (08) and in the preamplifier (04)
at room temperature
or operated at cryogenic temperatures below 100K. Method for operating a duplexer (08) according to one of Claims 2 to 12, optionally with features of Claim 13, characterized in that the duplexer (08)
for increasing the signal-to-noise ratio by suitable combination of all ion received signals amplified by the preamplifiers (04)
and / or for increasing the frequency resolution with the harmonic detection method by a combination of all of the preamplifier (04) amplified ion-receiving signals and / or for the detection of positive and negative ions with the quadrature detection method
is used.

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