JPH07320681A - High sensitivity hybrid photomultiplier tube - Google Patents

Abstract

PURPOSE: To provide a high-sensitivity hybrid photomultiplier tube which improves an electron focusing property of a focused electron-bombarded(FEB) ion detector and brings its stable operation. CONSTITUTION: A focused electron-bombarded(FEB) ion detector comprises a MCP, a focusing means, and a collection anode in a detector body and the collector anode includes a diode for receiving a focused output electron beam from the MCP. The gain between the input ion current to the MCP and the detector output signal from the diode is of the order of 10<6> -10<8> , depending on the device configuration and applied voltages. The hybrid photomultiplier tube comprises a photocathode 130, a photodiode 132 which collects electrons emitted from the photocathode 130 and multiplies these to provide an output signal, and focusing electrodes 134 and 136. Conductors 152 and 154 which are arranged on a side wall 116 or in a vicinity of a vacuum envelope lessen the effect of charged particles on an inside wall upon electron path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomultiplier tube and, more narrowly, in order to reduce the influence of charges on the wall of the vacuum envelope on electron trajectories inside the tube, a vacuum envelope. It relates to a hybrid photomultiplier tube having a conductor on or near it.

[0002]

BACKGROUND OF THE INVENTION Conventional photomultiplier tubes have a vacuum envelope containing a photocathode, several dynodes and an electron collector. When light enters the tube through the window and enters the photocathode, electrons are emitted from it. The electrons strike the continuous dynodes, doubling the secondary electrons. After striking the last dynode, the electrons are collected and sent on the output lead of the tube to give an output signal representative of the incident light.

A hybrid photomultiplier tube has a photocathode, an electron focusing electrode and an electron bombarded photodiode anode. The electrons emitted by the photocathode are focused on the photodiode. The electrons penetrate inside the photodiode material and create pairs of electrode holes, which at the same time have a doubling effect. Gain is produced by the photodiode rather than the dynode, as in conventional photomultiplier tubes.

The hybrid photomultiplier is
LK van Geest et al., “Hybrid Phototube With
Si Target ", SPIE, Vol. 1449, Electron Image Tubes
andImage Intensifiers , II, 1991, pp.121 ■ 134. A photomultiplier tube that uses both a dynode and an impact ionization diode for electron multiplication is disclosed in US Pat. No. 3,885,178.

[0005]

A bias voltage on the order of 10 kV is typically applied between the anode and cathode of the hybrid photomultiplier tube. The electrons are accelerated by the electric field and strike the photodiode anode, resulting in a doubling gain. However, depending on the photodiode material,
30% backscatter from the diode surface at various angles. Some electrons strike the inner wall surface of the tube and ionize the tube wall. These charges distort the potential inside the tube, thus impeding the focusing and stable operation of the electron beam. Furthermore, for sufficiently large accelerating voltages, X-rays are generated by electronic braking on the diode surface. X-rays strike the tube wall surface and cause surface ionization or positive charge. As a result, electron defocusing and unstable operation occur again. To determine the effect of capacitance on various parameters, a curved channel electronic multiplier where a portion of the outer surface was covered with a silver film was described by KC Schmidt et al. In “Continu
ous Channel Electron Multiplier Operated in the Pu
lse SaturatedMode ", IEEE Trans. Nucl. Sci. , June 1
966, p. 100 ■ 111.

One prior art approach to the problem of wall ionization in photomultiplier tubes is to partially coat the inner surface of the tube wall with a conductor such as green or black chromium oxide. is there. But,
Since the paint has high resistance, it prevents a short circuit of the tube electrode. Therefore, the paint is to reduce the wall ionization effect,
Not particularly effective. In addition, the life of the tubes is shortened by venting the paint to a vacuum envelope.

[0007]

A photomultiplier tube according to the present invention includes a photocathode for emitting electrons in response to incident photons, and a collection and doubling of the electrons emitted from the photocathode. A detector for providing an output signal representative of photons, an electro-optical means for controlling the trajectory of the electrons between the photocathode and the detector, and a means for accelerating the electrons between the photocathode and the detector. A vacuum envelope for enclosing the vacuum region between the photocathode and the detector, and at least a portion of the vacuum envelope to reduce the effect of the charge on the vacuum envelope on the electron trajectories. Or a conductive wire arranged in the vicinity thereof. The electro-optical means typically comprises first and second focusing electrodes.

Preferably, the conductor is arranged as a conductor paint or conductor paint on the outer surface of the vacuum envelope. In a preferred embodiment, the conductor is a first conductive coating formed on the vacuum envelope and electrically coupled to the photocathode, and an electrical conductor formed on the vacuum envelope and electrically connected to the first focusing electrode. And a second conductive paint bonded together. The first and second conductive paints are
They are spatially separated by a gap.

Typically, the photocathode is located on the interior surface of the window within the vacuum envelope. Suitably, the photocathode is a gallium arsenide compound, a gallium arsenide phosphorus compound,
It comprises a compound of Group 3 and Group 5 semiconductor atoms such as an indium phosphide compound or an indium phosphide / indium gallium arsenide compound.

Preferably, the vacuum envelope includes a coaxial feedthrough for coupling the output signal to the outside. Preferably, the photodiode comprises an avalanche photodiode mounted on the central conductor of the coaxial feedthrough.

According to another aspect of the invention, a vacuum envelope, a charged particle source within the vacuum envelope for emitting charged particles, and an optical for controlling the trajectory of the charged particles within the vacuum envelope. An improved vacuum tube of the type including the means is provided. The modifying means comprises a conductor disposed on or near at least a portion of the vacuum envelope to reduce the effect of charged particles on the vacuum envelope on electron trajectories.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A FEB ion detector is shown in FIGS. Standard Micro Channel Plate (MCP) 2
Is mounted on one end of the cylindrical detector body 4. In the embodiment shown in FIG. 1, the detector body 4 consists of serial ceramic rings stacked to give the proper size. In addition, the detector body is
It can be formed into a specially designed cylinder or other application shaped shape. The MCP 2 is held in place by the retainer 6. Leads 8 and 10 extend from the MCP input electrode 7 and MCP output electrode 9, respectively, for connecting the ion detector to a suitable power supply (not shown).

Two electron focusing rings 12 and 14 are arranged in the detector body 4. In the embodiment shown in FIG. 1, rings 12 and 14 are mounted between a pair of ceramic rings that make up detector body 4. Other means for attaching the focusing ring can be used within the scope of the invention. Rings 12 and 14 connect to an external power source (not shown), respectively, through suitable conductors 16 and 18. The purpose of the focusing rings 12 and 14 is to concentrate and direct the output of the MCP onto the collecting anode, as shown schematically in FIG.

The collecting anode 20 is arranged at the end of the detector body 4. The anode 20 comprises a broadband microwave connector 30, a stepped funnel-shaped coaxial transmission line section 32, and a solid-state diode 34 that terminates the transmission line.
In the preferred embodiment, diode 34 is an AlGaAs / GaAs pin diode optimized for electron impact current gain.
It is a diode. As shown in more detail in FIG. 2, the preferred embodiment of diode 34 comprises three independent layers 40, 42 and 44 formed on an n ⁺ GaAs substrate 46. The top layer 40 is a P with a thickness of about 250Å
Doped to be a type Al ₃₀ Ga ₇₀ As layer. Layer 40 provides a potential barrier near the diode surface so that the minority carriers of the generated electrons do not recombine at the surface. The components of layer 40 are also selected to resist stiffness and oxidation by in-air processing. The layer 42 is a P-type GaA layer having a thickness of about 0.25 μm.
Doped to be s.

Layer 44 is undoped GaAs and is about 6 μm thick. The thickness of layer 44 is selected to optimize the diode response time based on the following principles.

The _transit time T _transit of an electron across a non-dope layer of thickness w is represented by T _transit = w / V _sat , where V _sat is 1 × 10 ⁷ cm / sec.
The RC time constant T _RC of the load diode is expressed as T _RC = Eπr ² _RL / w, where r is the radius of the diode and R _L is the diode load (eg, 50Ω). The load diode response time is minimized when T _transit = T _RC or w / V _sat = Eπr ² _RL / w.

Therefore, the optimum value w or the undoped thickness is represented by w = √ (Eπr ² V _{sat RL} ). Therefore, the optimum time response is expressed as T _opt = √ (Eπr ² _RL / V _sat ). Since T _opt is proportional to the diode radius, the time response of FEB detectors using that diode is much improved over unfocused detectors.

The following is an example of the design and operating parameters of a FEB ion detector according to the preferred embodiment. M in this example
The CP has a plate diameter of 19 mm and a channel diameter of 10 μm. The external power supply applies a potential of about 1000 V across the input and output electrodes 7 and 9 of the MCP. Further, the power source applies a potential of about 30 V between the MCP output electrode 9 and the first focusing ring 12,
About 400 between the CP output electrode 9 and the second focusing ring 14.
A potential of V is applied. The collector anode 20 is grounded, and there is about 1 between the diode 34 and the MCP output.
A potential difference of 10,000 V occurs.

In operation, charged particles (like positive ions)
Hit the MCP channel wall, producing electrons. The electrons are accelerated across the MCP by the voltage, striking the channel walls to produce additional electrons. This multiplication of the electrons, together with the net gain of electrons per incident charged particle, leads to M
Electron flux is obtained at the CP output end. Thereafter, the generated electrons are accelerated and focused by the focusing rings 12 and 14. As schematically shown in FIG. 3, the focusing ring of the FEB ion detector reduces the diameter of the MCP output from 18 mm at the output electrode to a beam diameter of 0.25 mm at the collector anode 20 and applied to the MCP. The bias and focusing ring raises the average energy of the electrons striking the diode 34 to 10,000 eV. The gain of the FEB ion detector is by changing the bias voltage of the MCP (ie by changing the voltage between the MCP input and output electrodes) and by changing the total voltage between the focusing ring of the MCP and the collector anode. Can be adjusted. For an MCP bias voltage of 1000V, and for the total bias voltage of 10,000V exemplified herein,
The gain of the FEB ion detector is on the order of 9 × 10 ⁷ .

FIG. 4A shows a measured amplification characteristic curve (diode output current vs. input current), and FIG. 4B shows a differential gain of the prototype FEB ion detector. Here, the detector is used to detect the input electron current. The gain is 1
An input current of nA approaches 10 ⁶ .

The FEB detector relates to the pin diode's ability to handle relatively high instantaneous currents while delivering a linear response, improving the bandwidth and dynamic range of the device to improve the performance of the channeltron and MCP stack. Such current ion detector is improved. FEB detectors also have low capacitance and therefore faster recovery times than conventional detectors.

The FEB detector is a current channeltron or M
Longer life than CP stack ion detector. The high gain where required for operation of the channeltron and MCP stack increases the electron impact ratio at the output of the device. A high impact ratio deteriorates the internal surface of the channel, making it difficult to radiate. However, since the MCP operates at a low gain, such deterioration is avoided in the FEB ion detector of the present invention.

FEB detectors are not subject to the same stringent vacuum requirements that MCP stacks and channeltrons have. The high gain of current MCP stacks and channeltrons creates high electron density in the channel. Collision of electrons with gas molecules present in the channel creates positive ions. Under the influence of the bias voltage, when positive ions move towards the input end of the channel, they strike the channel wall, creating "noise" electrons. Higher bias voltage creates more ions, increasing the noise effect. Since the FEB ion detector of the present invention operates at a lower bias voltage than current channeltrons and MCP stacks,
Very few ions are created in the channel at a given gas molecule concentration. Therefore, the FEB detector is
Used with minimal ion noise effects under vacuum conditions lower than current detectors.

The above example is one of many possible forms, and other forms of FEB detectors are within the scope of the invention. For example, in another embodiment, a silicon or GaAs avalanche photodiode is replaced with the solid state diode described above to provide additional gain. Further, the detector may have one or more MCPs in series (stacked) for improved gain.

In another embodiment, the focusing ring is modified and additional focusing rings are added to optimize focusing for the application. Also, the single diode 34 is replaced with an array of diodes to provide position information.

The size and characteristics of the FEB detector should be chosen to match the application. For example, MCP
Is designed with a larger diameter to increase the detector input area. The connection between the diode and the device monitor is optimized by matching the impedance of the diode and the coaxial transmission line in a known manner. Impedance matching helps keep the detector response flat over the entire dynamic range.

The FEB ion detector, which has been described for the detection of ions, of various particles, such as neutral particles with x-rays, photons or energies, which produce electrons by striking the channel walls of the MCP. Also used for detection. Furthermore, although FEB detectors have been described for conventional MCPs, the walls can be doped or coated during use of the present invention to enhance the electron production effect by known methods. A preferred embodiment of the hybrid photomultiplier tube is shown in FIG. The equipotential lines and electron trajectories of the hybrid photomultiplier tube are shown schematically in FIG. The vacuum envelope 110 or housing is typically 10 ^-10 t
It encloses a vacuum region 112 having a pressure on the order of orr. The vacuum envelope 110 includes a window 114, sidewalls 116, electrodes 118 and a connector assembly 120. The side wall 11
6 typically consists of several ceramic rings.
Typically, vacuum envelope 110 is circularly symmetric with respect to central axis 122 such that sidewall 116 is cylindrical. However, the vacuum envelope 110 can have other physical shapes.

The photocathode 130 is disposed on the inner surface of the window 114. Preferably, the photocathode 130
Is a compound of Group 3 and Group 5 semiconductor atoms such as a gallium arsenide compound, a gallium arsenide phosphide compound, an indium phosphide compound or an indium phosphide / indium gallium arsenide compound. A suitable photocathode of gallium arsenide phosphorus compound is "A GaAsP Photo
cathode With 40% QE at515 nm ", SPIE Vol. 1655, Ele
ctron Tubes and Image Intensifiers , February 1992
Is disclosed in. A suitable gallium arsenide compound photocathode is used in "Imaging GaAs Va
cuum Photodiode with 40% Quantum Efficiency at 530
nm ", SPIE Vol. 1243, Electron Image Tubes and Ima
ge Intensifiers , 1990. Other suitable photocathodes are described in "Transferred by K. Costello et al.
Electron Photocathode with Greater Than 5% Quantu
m Efficiency Beyond One Micron ", SPIE Vol. 1449, E
lectron Tubes and Image Intensifiers II , 1991. Typically, as a wafer with an epitaxially grown layer, the appropriate photocathode constituent elements are deposited in the window 114 and, in the case of a GaAs or GaAsP photocathode, the wafer substrate is etched. In the case of a transfer electron photocathode, the substrate is either left in place or removed. The photocathode 1
30 emits electrons in response to incident light received through window 114.

Electrons emitted by the photocathode 130 are sealed inside the vacuum envelope 110 by an electrode 134.
And 136 to focus on the photodiode 132. Electrodes 134 and 136 have central apertures 138 and 140, respectively, which provide a path for electrons to photodiode 132. The location and size of electrodes 134 and 136 are selected to focus the electrons emitted by the photocathode onto photodiode 132. Further focusing electrodes can be used if desired.

Typically, the photocathode 130 is about -1.
Biased to 0 kV. In this photocathode, electrode 134 is typically at -9878V and electrode 13 is at
6 is biased at -9700V. The electrode 118 is electrically connected to the photodiode 132 and grounded. The bias voltage is applied by a suitable external power supply (not shown).

Preferably, the photo diode 132 is an avalanche photo diode and is mounted on the axis 122. When bombarded by energetic electrons from the photocathode 130, the photodiode 132 is selected to produce electron doubling. In the preferred embodiment, photodiode 132 is a GaAs / AlGaAs avalanche photodiode. Other suitable photodiodes include pinned photodiodes as shown in FIG. 2 and described in connection with the FEB ion detector.

As pointed out above, the charge is transferred to the sidewall 116.
Accumulate on the inner surface 142 of the. For example, the sidewalls 116 are a ceramic material having a thickness on the order of about 0.065 inches. As shown in FIG. 6, the electrons emitted from the photocathode 130 are focused by the electrodes 134 and 136 along trajectories 144, 146, etc.,
It is incident on the photo diode 132. Equipotential line 148,
150 etc. is established by the shape of the electrodes. When the charge is accumulated on the inner surface 142, the electric field shape and the electron orbit 14
4, 146 are affected and electrons are no longer focused on the photodiode 132.

To overcome this problem, conductors are placed on or near the sidewalls 116 of the vacuum envelope 110. Figure 5
In one embodiment, the conductors include conductors 152 and 154 on the outer surface of sidewall 116. The conductor 152 is electrically connected to the photocathode 130, and the conductor 154 is electrically connected to the electrode 130. In the example above,
The potential difference between the electrode 134 and the photocathode 130 is 1
Since it is on the order of 00V, the gap 156 is relatively small.

The effects of the conductors 152 and 154 are as follows. The charge on the inner surface 142 of the positively charged sidewall 116 is passivated by the charge of the same magnitude and opposite polarity on the conductors 152 and 154. Thereby, the inner surface 1
The electric field generated by the charge on 42 is trapped between the inner and outer surfaces of sidewall 116. The charges on the inner and outer surfaces of the sidewalls 116 effectively form a capacitor, and only the minimum edge field is from these charges to the photocathode 13.
Extends to the vacuum region between 0 and photodiode 132.
As a result, the charge on the inner surface 142 has no noticeable effect on the electron trajectories 144, 146, etc., followed by the electrons between the photocathode 130 and the photodiode 132.

The conductors 152 and 154 are realized by conventional methods such as metal foil or metal paint on the outer surface of the sidewall 116. It has been found that the metal foil and conductor paint on the outer surface of the photomultiplier tube results in stable operation of the tube. The advantage of paint on the outer surface is that the air regions between the sidewalls 116 and the conductors are removed. Such areas include photomultipliers
It causes anisotropy in electron optics in the tube. Used in the preferred embodiment is a metallic paint, such as silver paint, which covers the outer surface of sidewall 116. Conductors 152 and 15
The gap 156 between 4 is wide enough to be isolated from the voltage applied to each electrode. As best shown in FIG. 6, the gap 15 between conductors 152 and 154
6 is shielded or shaded from the line-of-sight axis to the photodiode 132 by the electrode 134, thereby minimizing the potential for charge stored on the sidewall 156 in the region of the gap 156.

It can be seen that the conductor is not applied to the outer surface of the sidewall 116 of the region 158 between the electrodes 136 and 118. Preferably, this portion of sidewall 116 is unpainted for some reason. A voltage of approximately 10 kV applied to the photomultiplier tube appears between electrodes 136 and 118. Therefore, a relatively large insulation gap is required. Furthermore, the photodiode 13
It was found that the electrons scattered from 2 follow a trajectory towards the photocathode 130 towards the opposite end of the tube. Finally, in the area near the photodiode 132,
The electrons are accelerated to a relatively large velocity, and the charged particles on the side wall 116 are less likely to affect the electron trajectories.

As another example, conductors 152 and 1
A conductor corresponding to 54 is disposed on the interior surface 142 of the sidewall 116. This is because good focusing of electron trajectories 144, 146, etc. to the photodiode 132 has been found to be possible and slightly improved by using conductors 152 and 154. In this case, the charged particles that have accumulated on the insulating surface 42 will be conducted by the conductor above it. This method is effective in preventing accumulation because the conductor inside the vacuum envelope 110 outgases and shortens the life of the photomultiplier tube, but conductors 152 and 154 are provided on the outer surface of the sidewall 116. It is less effective than installing it.

The connector assembly 120 includes a central conductor 160 mounted within a ceramic insulator 162. The ceramic insulator 162 is the outer conductor 16
Supported by 4. Ceramic insulator 1
62 is brazed to the central conductor 160 and the outer conductor 164. The outer conductor 164 is welded to the electrode 118 to form a solid vacuum assembly. The photodiode 132 is mounted on one end of the central conductor 160 extending into the vacuum region 112 so as to substantially cover the central conductor 160. As shown in FIG. 6, the ceramic insulator 162 includes a metal coating 166 that is electrically coupled to the electrode 118 and surrounds the center conductor 160 without contact. The thin conductive wire 168 is used for the metal coating 166 and the photodiode 13.
It is connected between the tops of the two contact pads. Further, the connector assembly 120 is fixed to the central conductor 160 and the outer conductor 164 by the lock nut 172,
It includes a conventional SMA-type coaxial connector 170.

The connector assembly 120 is a hybrid
It has several advantages in the operation of photomultiplier tubes. The connector is a vacuum envelope 110.
Functioning as a part of, thus affecting the shape of the electric field in the tube. Since the inner surface of the connector is exposed to the volume of the tube, it is rubbed by electrons during the tube process to clean the tube. The connector supports the photodiode 132 on a central conductor that is completely covered by the photodiode 132. Therefore, the bias voltage applied to the photodiode 132 does not affect the electric field that focuses the electrons on the photodiode. The preferred photodiode 132 has a relatively low operating voltage and can also use standard SMA output connectors. The connector is impedance matched to 50Ω to allow a flat frequency response above 1 GHz.

In the preferred embodiment, the photocathode 13
The 0 has a diameter of 24.5 mm and the window 114 is made of Corning type 7056 glass. The vacuum envelope 110 has a diameter of 1.6 inches and a length of 2.0 inches. The quantum effects and response sensitivities of gallium arsenide phosphide photocathodes described in JP Edgecumbe et al., Supra, are plotted in FIG. 7 as a function of wavelength. The quantum effects and response sensitivities of gallium arsenide photocathodes described in the above-mentioned KA Costello et al. Article are graphed in FIG. 8 as a function of wavelength. In both cases, a gain of 20,000 or more and a rise time of 0.5 ns or less are expected. Electron impact gain is graphed in FIG. 9 as a function of photocathode bias relative to the anode.

The use of conductors on or near the vacuum envelope to limit the effect of charged particles on the envelope walls on electron trajectories has been described in connection with hybrid photomultiplier tubes. It was This method of passivating charge storage by conductors on the outer surface of the vacuum envelope can be used for other photomultiplier tubes, and more generally, vacuum envelopes, charged particle sources and vacuum envelopes. Any vacuum tube containing optics to control the trajectories of charged particles inside the enclosure can be used. Furthermore, the conductor is
It can be used in the FEB ion detector described above. By limiting the electric field generated by the charge to the region within the wall of the vacuum envelope, the effect of charge on the trajectory of charged particles is minimized. As mentioned above, the conductors are placed on or near the vacuum envelope in any area where it is desired to limit the effect of charges on the interior surface of the vacuum envelope.

While the present contemplation and embodiments of the invention have been described, it should be understood that various changes and modifications can be made without departing from the spirit and aspects of the claimed invention. That's what the vendors admit.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an FEB ion detector.

FIG. 2 is a detailed view of the diode element of the FEB ion detector.

FIG. 3 is a schematic diagram showing the operation of the FEB ion detector.

FIG. 4A shows a measured amplification characteristic curve of output current vs. input current of the FEB ion detector, and FIG. 4B shows differential gain vs. input current curve calculated from A.

FIG. 5 is a cross-sectional view of the hybrid photomultiplier tube of the present invention.

6 is a schematic diagram of the photomultiplier tube of FIG. 5, showing the conductor portion of the tube and the equipotential lines and electron trajectories due to the electric field generated.

FIG. 7 is a graph of quantum efficiency and sensitivity of gallium arsenide phosphide compounds to photocathodes as a function of wavelength.

FIG. 8 is a graph of quantum efficiency and sensitivity of a gallium arsenide compound to a photocathode as a function of wavelength.

FIG. 9 is a graph of electron impact gain as a function of photocathode bias for anode.

[Explanation of symbols]

 110 Vacuum Envelope 112 Vacuum Region 114 Window 116 Sidewall 118 Electrode 120 Connector Assembly 122 Axis 130 Photocathode 132 Photodiode 134 Electrode 136 Electrode 142 Inner Surface 152 Conductor 154 Conductor 156 Gap 160 Central Conductor 162 Ceramic Insulator 164 Outer Conductor 168 Fine wire 170 Coaxial connector 172 Lock nut

 ─────────────────────────────────────────────────── ───Continued from the front page (72) Inventor Bur W. Ahrabi Laurel Saint 220, Menlo Park, CA, USA

Claims (26)

[Claims] 1. A photocathode for emitting electrons in response to incident photons, for assembling and multiplying the electrons emitted by the photocathode, and for providing an output signal representative of the input photons. Detector, one or more electrodes for focusing the electrons on the detector, means for accelerating the electrons towards the detector, the photocathode and the detector. A vacuum envelope defining a vacuum region between the photocathode and the detector, the vacuum envelope including a sidewall proximate to the electron path, and charged particles on the sidewall affect the electron trajectory. A photomultiplier tube comprising a conductor disposed on or near the sidewall to reduce effects. 2. The photomultiplier tube as defined in claim 1, wherein the conductor is disposed on an outer surface of the sidewall. 3. A photomultiplier tube as defined in claim 2, wherein the conductor comprises a conductive coating on the outer surface. 4. A photomultiplier tube as defined in claim 3, wherein the conductive paint comprises silver. 5. A photomultiplier tube as defined in claim 2, wherein the conductor is electrically coupled to a first portion electrically coupled to the photocathode and one of the electrodes. A second portion, the first and second
A photomultiplier tube where the parts are separated by a gap. 6. A photomultiplier tube as defined in claim 1, wherein the vacuum envelope includes a window.
A photomultiplier tube, wherein the photocathode is disposed on the inner surface of the window. 7. The photomultiplier tube as defined in claim 6, wherein the photocathode comprises a Group 3 and Group 5 semiconductor element. 8. A photomultiplier tube as defined in claim 6, wherein the photocathode is GaA.
A photomultiplier tube selected from the group consisting of s, GaAsP, InP and InP / InGaAs. 9. A photomultiplier tube as defined in claim 1, wherein the electrodes are spaced apart first and second having apertures for passage of the electrons.
Photomultiplier tube where the electrodes are included. 10. A photomultiplier tube as defined in claim 1, wherein the detector comprises an avalanche photodiode. 11. A photomultiplier tube as defined in claim 10, wherein the vacuum envelope includes a coaxial feedthrough coupled to the photodiode.
A photomultiplier tube in which the coaxial feedthrough connects the output signal to the outside of the vacuum envelope. 12. A photomultiplier tube as defined in claim 11, wherein the coaxial feedthrough includes a center conductor and the photodiode is mounted on the center conductor. tube. 13. The photomultiplier tube as defined in claim 12, wherein the photodiode covers one end of the central conductor. 14. A type including a vacuum envelope, a charged particle source in the vacuum envelope for emitting charged particles, and optics for controlling the trajectory of the charged particles in the vacuum envelope. In the vacuum tube according to claim 1, the improvement is a vacuum tube comprising a conductor arranged on or near the vacuum envelope for reducing the influence of the charged particles on the vacuum envelope on the trajectory of the charged particles. 15. An improved vacuum tube as defined in claim 14, wherein the charged particle source comprises an electron source. 16. An improved vacuum tube as defined in claim 15, wherein the conductor is disposed on an outer surface of the vacuum envelope. 17. An improved vacuum tube as defined in claim 16, wherein the conductor comprises paint on the outer surface. 18. An improved vacuum tube as defined in claim 14, wherein the vacuum tube comprises a photomultiplier tube. 19. A photocathode for emitting electrons in response to incident photons; a photodiode for collecting and multiplying the electrons and for providing an output signal representative of the incident photons; and the photocathode. Electron-optical means for controlling the trajectories of the electrons between the photodiodes, and an electric field for accelerating the electrons between the photocathodes and the photodiodes between the photocathodes and the photodiodes. A vacuum envelope that defines a vacuum region between the photocathode and the photodiode, and a means for reducing the effect of charges on the vacuum envelope on the electrons. A conductor disposed on at least a portion of the outer surface of the vacuum envelope. 20. A photomultiplier tube as defined in claim 19, wherein said electro-optic means comprises first and second focusing electrodes. 21. A photomultiplier tube as defined in claim 20, wherein the conductor comprises a first conductor coating formed on the vacuum envelope and electrically connected to the photocathode. A second conductor paint formed on the vacuum envelope and electrically connected to the first focusing electrode, wherein the first and second conductor paints are separated by a gap. Photomultiplier tube. 22. A photomultiplier tube as defined in claim 21, wherein the gap between the first and second conductive coatings is located on a portion of the vacuum envelope, and A photomultiplier tube, which is blocked by the electro-optic means from a straight line of sight to the photodiode. 23. The photomultiplier tube as defined in claim 19, wherein the vacuum envelope includes a window and the photocathode is disposed on an inner surface of the window. ·tube. 24. A photomultiplier tube as defined in claim 23, wherein the photocathode is 3
A photomultiplier tube that is made of semiconductor elements of Groups 5 and 5. 25. The photomultiplier tube as defined in claim 19, wherein the vacuum envelope includes a coaxial feedthrough for coupling the output signal to the outside of the vacuum envelope. , And the photodiode is mounted on the central conductor of the coaxial feedthrough. 26. A photocathode for emitting electrons in response to an incident photon, for assembling and multiplying the electrons emitted by the photocathode, and for providing an output signal representative of the input photon. Detector, electro-optical means for controlling the trajectory of the electrons between the photocathode and the detector, means for accelerating the electrons toward the detector, and the photocathode A vacuum envelope defining a vacuum region between the detector and an inner surface of the vacuum envelope for reducing the effect of charged particles on the vacuum envelope on the orbits of the electrons. A photomultiplier tube comprising a conductor disposed at least in part.