A mev-level gamma-sensitive electron multiplier and a method for manufacturing the same

Abstract

The application discloses a MeV-level gamma-sensitive electron multiplier and a preparation method thereof, relates to the technical field of gamma detectors, and gamma rays enter a tubular shell through a collimator, secondary electrons are generated through the interaction of a metal cathode and the incident gamma rays, a substrate is fixed on the inner surface of the metal cathode, and the surface of the substrate is composed of negative electron affinity material in the micron scale range, so that the secondary electrons with low energy and multiplied number are generated under the excitation of the secondary electrons penetrating the substrate; the secondary electrons emitted from the surface of the negative electron affinity material are cascade multiplied through a microchannel plate, and finally the secondary electrons multiplied through the microchannel plate are collected through a metal anode to form an output signal, so that the count rate and the action time information of the gamma rays to be measured collimated through the collimator are detected; the MeV-level gamma-sensitive electron multiplier has the detection characteristics of high gain and fast response to MeV gamma rays.

Description

Technical Field

[0001] The present application relates to the technical field of gamma detectors, and in particular to a MeV-level gamma-sensitive electron multiplier and a preparation method thereof. Background Art

[0002] Among existing gamma-ray detectors, only scintillation detectors possess both the excellent detection properties of fast response (nanoseconds) and high gain. However, due to the limitations of the scintillation luminescence mechanism, the fastest scintillation detectors have a response time of approximately nanoseconds (0.6ns, BaF scintillation detectors), making it currently impossible to develop and design gamma-ray detectors with even lower response times.

[0003] The electron multiplier is a high-gain, fast-response device based on the physical mechanism of secondary electron emission. It is mainly used to monitor low-energy rays, charged ions or electrons in a vacuum system. The working principle of the electron multiplier is that first, a dynode made of a material with a large secondary electron multiplication coefficient (such as Cu-Be-O alloy, lead glass, etc.) converts the incident charged particles or low-energy rays into low-energy electrons, and then, under the control of the electric field, sequentially arranged dynodes or sequentially connected multiplication materials are used to achieve cascade multiplication of the number of low-energy electrons. Finally, the anode receives the multiplied electrons to form a high-gain output signal. The gain of the electron multiplier can be as high as 1E7. It has two main types, dynode type and microchannel plate type, see Figure 1 As shown in Figure 2, combining photocathode technology with electron multiplier technology has also led to the development of photomultiplier tubes for measuring weak optical signals. The physical mechanism of secondary electron emission has a fast intrinsic time response. With good electron focusing design, electron multipliers can achieve both high gain and fast response, providing an excellent foundation for the development and design of high-gain, fast-response gamma detectors.

[0004] However, because the effective thickness of conventional dynode materials for secondary electron emission is only tens of nanometers, electron multipliers are only sensitive to heavy charged particles, low-energy radiation, and electrons below the keV level within a range of tens of nanometers. When MeV-level radiation is incident, the energy deposited within the effective thickness is too low to produce effective secondary electron emission. Consequently, the subsequent multiplication process loses input and fails to generate a valid output signal. Consequently, conventional electron multipliers are insensitive to MeV-level gamma rays and cannot be directly used for MeV-level gamma-ray detection. Summary of the Invention

[0005] The purpose of this application is to provide a MeV-level gamma-sensitive electron multiplier and a preparation method thereof, which can achieve high-gain and fast-response detection of MeV-level gamma rays.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the application provides a MeV-level gamma-sensitive electron multiplier, comprising: a tubular shell, a metal anode, a metal cathode, a substrate, a microchannel plate, and a spring set; the spring set comprises a first spring, a second spring, and a third spring.

[0008] The tube wall direction of the tubular shell is parallel to the incident direction of the gamma rays, and the gamma rays enter the tubular shell through the collimator; the metal anode is arranged on the side of the tubular shell away from the collimator, and the metal cathode is arranged on the side of the tubular shell close to the collimator, and the space formed by the tubular shell, the metal cathode, and the metal anode is kept in a high vacuum environment; the metal cathode is used for interacting with the incident gamma rays to generate secondary electrons.

[0009] The substrate is clamped on the inner surface of the metal cathode by the third spring, and the outer surface of the metal cathode is arranged corresponding to the collimator; the negative electron affinity material is formed in the micron scale range on the surface of the substrate, and the negative electron affinity material is used for generating secondary electrons with low energy and multiplied number under the excitation of the secondary electrons penetrating the substrate.

[0010] The microchannel plate is clamped between the substrate and the metal anode by the first spring and the second spring, and the microchannel plate is used for cascade multiplication of the secondary electrons emitted from the surface of the negative electron affinity material.

[0011] The metal anode is used for collecting the secondary electrons after cascade multiplication by the microchannel plate to form an output signal.

[0012] Optionally, it further comprises: a high-voltage pin, an incident window voltage division pin, an emission window voltage division pin, and a signal lead-out pin; the high-voltage pin is connected to the negative electron affinity material and an external negative high-voltage power supply, the incident window voltage division pin is connected to the second spring, the emission window voltage division pin is connected to the first spring, and the signal lead-out pin is connected to the metal anode.

[0013] A first voltage division resistor is connected in series between the incident window voltage division pin and the high-voltage pin, so as to form an electric field between the surface of the negative electron affinity material and the incident window of the microchannel plate; a second voltage division resistor is connected in series between the emission window voltage division pin and the incident window voltage division pin, so as to form an electric field for normal operation of the microchannel plate; and a third voltage division resistor is connected in series between the emission window voltage division pin and the ground potential, so as to form an electric field between the emission window of the microchannel plate and the metal anode.

[0014] Optionally, the substrate is composed of GaAs intrinsic semiconductor material; the negative electron affinity material is formed in the micron scale range on the surface of the substrate after a series of process treatments such as high-temperature thermal cleaning, high p+ doping, and Cs—O activation.

[0015] Optionally, the collimator is provided with shielding bodies made of heavy metal materials on both sides.

[0016] In a second aspect, the application provides a preparation method of the MeV gamma sensitive electron multiplier as described above, comprising the following steps:

[0017] The microchannel plate is fixed in the tubular shell by using the first and second clamps to obtain a tube assembly; the tube wall of the tubular shell is parallel to the incident direction of the gamma rays, and the gamma rays enter the tubular shell through the collimator.

[0018] The metal anode is sealed and welded on the side of the tube assembly away from the collimator to obtain an anode assembly.

[0019] The substrate is fixed on the surface of the metal cathode by using the third clamp, and a negative electron affinity material is formed on the surface of the substrate in the micrometer scale range to obtain a cathode assembly.

[0020] The anode assembly and the cathode assembly are welded in a high vacuum environment to obtain the MeV gamma sensitive electron multiplier.

[0021] Optionally, the input window electrode of the microchannel plate is in communication with the input window voltage dividing pin, the output window electrode of the microchannel plate is in communication with the output window voltage dividing pin; the metal anode is in communication with the signal lead-out pin; the negative electron affinity material is in communication with an external negative high-voltage power supply through the high-voltage pin; a first voltage dividing resistor is connected in series between the incident window voltage dividing pin and the high-voltage pin, a second voltage dividing resistor is connected in series between the output window voltage dividing pin and the incident window voltage dividing pin, and a third voltage dividing resistor is connected in series between the output window voltage dividing pin and the ground potential.

[0022] Optionally, the substrate is composed of GaAs intrinsic semiconductor material; the substrate is fixed on the surface of the metal cathode by using the third clamp, and a negative electron affinity material is formed on the surface of the substrate in the micrometer scale range to obtain the cathode assembly, specifically comprising the following steps:

[0023] The substrate is fixed on the surface of the metal cathode by using the third clamp to obtain a cathode assembly to be processed.

[0024] The surface of the substrate of the cathode assembly to be processed is sequentially subjected to a high-temperature thermal cleaning, a high-p+ doping, and a Cs-O activation series of process treatments to form a negative electron affinity material on the surface of the substrate in the micrometer scale range to obtain the cathode assembly.

[0025] Optionally, the collimator is provided with shielding bodies made of heavy metal materials on both sides.

[0026] According to the specific embodiments provided by the application, the following technical effects are disclosed:

[0027] The application provides a MeV-level gamma-sensitive electron multiplier and a preparation method thereof, wherein a metal anode is arranged on a tubular shell away from a collimator, a metal cathode is arranged on the tubular shell close to the collimator, and a space formed by the three is kept in a high vacuum environment; gamma rays enter the tubular shell through the collimator, and the metal cathode and the incident gamma rays interact to generate secondary electrons; a substrate on the inner surface of the metal cathode is composed of a negative electron affinity material in the micron scale range of the surface of the substrate, so as to generate secondary electrons with low energy and multiplied number under the excitation of the secondary electrons penetrating the substrate; a microchannel plate is clamped between the substrate and the metal anode, and is used for carrying out cascade multiplication of the secondary electrons emitted from the surface of the negative electron affinity material; finally, the secondary electrons multiplied by the microchannel plate are collected by the metal anode to form an output signal, so that the count rate and the action time information of the gamma rays to be measured collimated by the collimator are detected; the MeV-level gamma-sensitive electron multiplier designed in the application has the detection characteristics of high gain and fast response to MeV gamma rays, the sealed space formed by the tubular shell, the metal cathode and the metal anode keeps a good high vacuum, and the whole device works in an atmospheric environment, without the need of providing an additional high vacuum working environment. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] Figure 1 It is a structural schematic diagram of the traditional two kinds of electron multipliers.

[0030] Figure 2 It is a structural schematic diagram of a MeV-level gamma-sensitive electron multiplier provided by an embodiment of the present application.

[0031] Figure 3 It is an application schematic diagram of a MeV-level gamma-sensitive electron multiplier provided by an embodiment of the present application.

[0032] Figure 4 It is a flowchart of a preparation method of the MeV-level gamma-sensitive electron multiplier mentioned in the above embodiment provided by an embodiment of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0034] The above purposes, features and advantages of the present application will be more apparent and understandable, and the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0035] In an exemplary embodiment, as shown in the structure, Figures 2-3 The MeV gamma sensitive electron multiplier includes a metal anode 1, a metal cathode 2, a tubular shell 3, a substrate 4, a microchannel plate 5 and a spring set; the spring set includes a first spring 6, a second spring 7 and a third spring 8.

[0036] The tube wall direction of the tubular shell 3 is parallel to the incident direction of the gamma rays, the gamma rays enter the tubular shell 3 through a collimator, and shielding bodies made of heavy metal materials are arranged on both sides of the collimator; the metal anode 1 is arranged on the side of the tubular shell 3 away from the collimator, and the metal cathode 2 is arranged on the side of the tubular shell 3 close to the collimator, and the space formed by the tubular shell 3, the metal cathode 2 and the metal anode 1 is kept in a high vacuum environment (less than 1E-8 Pa); the metal cathode 2 is used for interacting with the incident gamma rays to generate secondary electrons. In an alternative embodiment, the tubular shell 3 is a closed ceramic metal tube body material, the diameter of the tubular shell 3 is 30 mm, the height is 20 mm, and the side wall thickness is 3 mm.

[0037] The substrate 4 is clamped on the inner surface of the metal cathode 2 by the third spring 8, and the outer surface of the metal cathode 2 is arranged corresponding to the collimator; a negative electron affinity material 9 is formed in the micron scale range on the surface of the substrate 4, which is used to generate low-energy and multiplied secondary electrons under the excitation of the secondary electrons penetrating the substrate 4. In this embodiment, the substrate 4 is composed of GaAs intrinsic semiconductor material, the diameter of the substrate 4 is 20 mm, and the thickness is 0.35 mm. After high-temperature thermal cleaning, high p+ doping (doping concentration greater than 1E18 cm-2) and Cs—O activation series of process treatment, the negative electron affinity material 9 is formed in the micron scale range on the surface of the substrate 4.

[0038] The microchannel plate 5 is clamped between the substrate 4 and the metal anode 1 by the first spring 6 and the second spring 7, and the microchannel plate 5 is used for cascade multiplication of the secondary electrons emitted from the surface of the negative electron affinity material 9. The first spring 6, the second spring 7 and the third spring 8 are all made of annular stainless steel material with a thickness of 0.5 mm, an inner diameter of 24 mm and a width of 5 mm.

[0039] a metal anode 1 for collecting the secondary electrons after the cascade multiplication of the microchannel plate 5 to form an output signal.

[0040] Further comprising: a high-voltage pin 12, an incident window voltage division pin 13, an emission window voltage division pin 14, and a signal lead-out pin 15; the high-voltage pin 12 is connected to the negative electron affinity material 9 and an external negative high-voltage power supply, the incident window voltage division pin 13 is connected to the second clasp 7, the emission window voltage division pin 14 is connected to the first clasp 6, and the signal lead-out pin 15 is connected to the metal anode 1. In an optional embodiment, the metal cathode 2 and the metal anode 1 are both made of a stainless steel sheet with a diameter of 36 mm and a thickness of 1 mm, and the part of the stainless steel sheet larger than the tubular shell 3 is used as the high-voltage pin 12 and the signal lead-out pin 15, respectively.

[0041] The first voltage division resistor R1 is connected in series between the incident window voltage division pin 13 and the high-voltage pin 12 to form an electric field between the surface of the negative electron affinity material 9 and the incident window electrode 10 of the microchannel plate; the second voltage division resistor R2 is connected in series between the emission window voltage division pin 14 and the incident window voltage division pin 13 to form an electric field for normal operation of the microchannel plate 5; and the third voltage division resistor R3 is connected in series between the emission window voltage division pin 14 and the ground potential to form an electric field between the emission window electrode 11 of the microchannel plate and the metal anode 1. The incident window voltage division pin 13 and the emission window voltage division pin 14 are made of stainless steel material with a thickness of 0.5 mm and a width of 3 mm, and penetrate the wall of the tubular shell 3 without affecting the vacuum performance.

[0042] The MeV gamma sensitive electron multiplier designed in the above embodiments of the application is sensitive to MeV gamma rays, and the typical detection efficiency for 1.25 MeV gamma rays can reach 5 ‰. The MeV gamma sensitive electron multiplier has high gain and fast response for MeV gamma rays, and the output single particle signal is greater than 10 mA, and has intrinsic single particle event response capability. In addition, the MeV gamma sensitive electron multiplier can be used in atmospheric environment conditions by using the integrated vacuum integral sealing technology, and does not need to provide an additional high vacuum working environment.

[0043] Based on the same inventive concept, the embodiments of the application also provide a preparation method for preparing the MeV gamma sensitive electron multiplier described above, as shown in Figure 4 The preparation method comprises the following steps S1 to S4:

[0044] S1, fixing the microchannel plate in the tubular shell by using the first clasp and the second clasp to obtain a tubular assembly; the wall direction of the tubular shell is parallel to the incident direction of the gamma rays, and the gamma rays enter the tubular shell through the collimator. Shielding bodies made of heavy metal material are arranged on both sides of the collimator.

[0045] S2, sealing welding the metal anode on the side of the tube assembly body away from the collimator, to obtain an anode assembly body.

[0046] S3, fixing the substrate on the surface of the metal cathode by the third clamping spring, and forming the negative electron affinity material in the micron scale range of the surface of the substrate, to obtain a cathode assembly body. In an embodiment, the substrate is composed of GaAs intrinsic semiconductor material; and step S3 specifically includes the following steps:

[0047] S31, fixing the substrate on the surface of the metal cathode by the third clamping spring, to obtain a cathode assembly body to be processed.

[0048] S32, sequentially performing high-temperature thermal cleaning, high p+ doping, and Cs—O activation series of process treatments on the surface of the substrate of the cathode assembly body to be processed, to form the negative electron affinity material in the micron scale range of the surface of the substrate, to obtain a cathode assembly body.

[0049] S4, welding the anode assembly body and the cathode assembly body in a high-vacuum environment, to obtain a MeV-level gamma-sensitive electron multiplier.

[0050] In the preparation method, the input window electrode of the microchannel plate is in communication with the input window voltage dividing pin, the output window electrode of the microchannel plate is in communication with the output window voltage dividing pin; the metal anode is in communication with the signal leading-out pin; the negative electron affinity material is in communication with an external negative high-voltage power supply through the high-voltage pin; a first voltage dividing resistor is connected in series between the incident window voltage dividing pin and the high-voltage pin, a second voltage dividing resistor is connected in series between the exit window voltage dividing pin and the incident window voltage dividing pin, and a third voltage dividing resistor is connected in series between the exit window voltage dividing pin and the ground potential.

[0051] In a specific embodiment, the MeV-level gamma-sensitive electron multiplier prepared in the above embodiment is assembled in a step-by-step manner, including the following steps: in the first step, the microchannel plate is fixed between the first and second clamping springs and electrical communication is achieved between the microchannel plate input window electrode and the input window voltage dividing pin and between the output window electrode and the output window voltage dividing pin; in the second step, the sealing welding of the metal anode and the tubular shell is completed to form an anode assembly and the anode assembly is placed in a high-vacuum environment for waiting for overall sealing assembly; in the third step, the GaAs substrate sheet is fixed on the inner surface of the metal cathode by using the third clamping spring to form a cathode assembly to be processed; in the fourth step, the cathode assembly to be processed is placed in a high-vacuum environment and the GaAs substrate sheet surface of the cathode assembly to be processed is subjected to high-temperature thermal cleaning, heavy p+ doping (doping concentration greater than 1E18 cm-2), and Cs—O activation process to form a negative electron affinity material in the surface range of several microns in electrical communication with the third clamping spring; in the fifth step, the processed cathode assembly and the anode assembly are subjected to overall welding sealing in a high-vacuum environment; in the sixth step, the sealed device is removed from the high-vacuum environment, and in the atmospheric environment, a 12MΩ voltage dividing resistor is connected in series between the high-voltage pin and the input window voltage dividing pin, a 24MΩ voltage dividing resistor is connected in series between the input window voltage dividing pin and the output window voltage dividing pin, and a 6MΩ voltage dividing resistor is connected in series between the output window voltage dividing pin and the ground potential; in the seventh step, the metal anode pin is connected to the signal feedthrough and the signal lead-out pin is connected to the high-voltage feedthrough, and an external -5000V high-voltage power supply is required. The electron multiplier outputs one pulse corresponding to one gamma photon interacting with the multiplier; and the starting time of the pulse corresponds to the time information of the gamma photon interacting with the multiplier.

[0052] In the description of the present application, it should be noted that the terms "first", "second" are only for the purpose of description and cannot be understood as indicating or implying relative importance. The above materials, sizes, processes, steps are only preferred embodiments of the present application, and other materials, sizes, processes and steps with similar performance can also be selected as long as the material function, index requirement, and vacuum sealing process requirement are met.

[0053] The technical features of the above embodiments can be combined in any manner, and to make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0054] The principles and implementation modes of the present application are described by using specific examples herein, and the above embodiments are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation modes and application ranges can be changed according to the idea of the present application. In conclusion, the content of the present application should not be understood as a limitation.

Claims

1. A MeV-level gamma-sensitive electron multiplier, characterized in that: The MeV-level gamma-sensitive electron multiplier comprises: a tubular housing, a metal anode, a metal cathode, a substrate, a microchannel plate, and a spring assembly; the spring assembly comprises a first spring, a second spring, and a third spring; The wall of the tubular housing is parallel to the incident direction of the gamma ray, and the gamma ray enters the tubular housing through the collimator. The metal anode is arranged on a side of the tubular housing away from the collimator, and the metal cathode is arranged on a side of the tubular housing close to the collimator. The space formed by the tubular housing, the metal cathode, and the metal anode maintains a high vacuum environment. The metal cathode is used to interact with the incident gamma ray to generate and emit secondary electrons. The substrate is clamped on the inner surface of the metal cathode by the third clamping spring, and the outer surface of the metal cathode is arranged corresponding to the collimator; a negative electron affinity material is formed within the micrometer scale range on the surface of the substrate, and the negative electron affinity material is used to generate secondary electrons with low energy and multiplied number under the stimulation of secondary electrons penetrating the substrate; The microchannel plate is clamped between the substrate and the metal anode by the first clamping spring and the second clamping spring, and the microchannel plate is used to cascade multiply the secondary electrons emitted from the surface of the negative electron affinity material; The metal anode is used to collect secondary electrons after cascade multiplication by the microchannel plate to form an output signal.

2. The MeV-level gamma-sensitive electron multiplier according to claim 1, characterized in that The device further comprises: a high-voltage pin, an incident window voltage-dividing pin, an exit window voltage-dividing pin, and a signal lead-out pin; the high-voltage pin is connected to the negative electron affinity material and an external negative high-voltage power supply, the incident window voltage-dividing pin is connected to the second clip spring, the exit window voltage-dividing pin is connected to the first clip spring, and the signal lead-out pin is connected to the metal anode; A first voltage-dividing resistor is connected in series between the incident window voltage-dividing pin and the high-voltage pin to form an electric field between the surface of the negative electron affinity material and the incident window of the microchannel plate; a second voltage-dividing resistor is connected in series between the exit window voltage-dividing pin and the incident window voltage-dividing pin to form an electric field for normal operation of the microchannel plate; a third voltage-dividing resistor is connected in series between the exit window voltage-dividing pin and the ground potential to form an electric field between the exit window of the microchannel plate and the metal anode.

3. The MeV-level gamma-sensitive electron multiplier according to claim 1, characterized in that The substrate is made of GaAs intrinsic semiconductor material; after being processed through a series of processes including high-temperature thermal cleaning, high p+ doping, and Cs-O activation, a negative electron affinity material is formed within a micrometer scale range on the surface of the substrate.

4. The MeV-level gamma-sensitive electron multiplier according to claim 1, characterized in that Shielding bodies made of heavy metal materials are provided on both sides of the collimator.

5. A method for preparing a MeV-level gamma-sensitive electron multiplier according to any one of claims 1 to 4, characterized in that: The preparation method of the MeV-level gamma-sensitive electron multiplier comprises: The microchannel plate is fixed in a tubular housing by using a first clamping spring and a second clamping spring to obtain a tubular body assembly; the wall direction of the tubular housing is parallel to the incident direction of the gamma ray, and the gamma ray enters the tubular housing through the collimator; Sealing and welding a metal anode on a side of the tube assembly away from the collimator to obtain an anode assembly; The substrate is fixed to the surface of the metal cathode by using a third clamping spring, and a negative electron affinity material is formed within a micrometer scale range on the surface of the substrate to obtain a cathode assembly; The anode assembly and the cathode assembly are welded in a high vacuum environment to obtain a MeV-level gamma-sensitive electron multiplier.

6. The method for preparing a MeV-level gamma-sensitive electron multiplier according to claim 5, characterized in that: The input window electrode of the microchannel plate is connected to the input window voltage divider pin, and the output window electrode of the microchannel plate is connected to the output window voltage divider pin; the metal anode is connected to the signal lead-out pin; the negative electron affinity material is connected to the external negative high-voltage power supply through the high-voltage pin; a first voltage divider resistor is connected in series between the incident window voltage divider pin and the high-voltage pin, a second voltage divider resistor is connected in series between the exit window voltage divider pin and the incident window voltage divider pin, and a third voltage divider resistor is connected in series between the exit window voltage divider pin and the ground potential.

7. The method for preparing a MeV-level gamma-sensitive electron multiplier according to claim 5, characterized in that: The substrate is made of GaAs intrinsic semiconductor material; the substrate is fixed to the surface of the metal cathode by a third clamping spring, and a negative electron affinity material is formed within the micrometer scale range on the surface of the substrate to obtain a cathode assembly, which specifically includes: The substrate is fixed to the surface of the metal cathode by using a third clamping spring to obtain a cathode assembly to be processed; The substrate surface of the cathode assembly to be processed is sequentially subjected to high-temperature thermal cleaning, high p+ doping, and Cs-O activation process series, forming a negative electron affinity material within the micrometer scale range on the surface of the substrate to obtain a cathode assembly.

8. The method for preparing a MeV-level gamma-sensitive electron multiplier according to claim 5, characterized in that: Shielding bodies made of heavy metal materials are provided on both sides of the collimator.

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