JPS6020441A - Detector for radioactive rays - Google Patents

Abstract

PURPOSE:To make a photoelectron multiplier tube carrying a single photoelectric emission surface do a function commensurate to more than two photoelectron multiplier tubes, by installing a mesh electrode, while controlling the action of a photoelectron in a specified part of the photoelectron emission surface. CONSTITUTION:A mesh electrode 26 for gate use enters in space between a photoelectric emission surface 21 and a focusing electrode 22. An energy discriminator 41 generates a signal from that point of judgment that output of an amplifier 40 is cuased by an optical signal pulse. Usually a gate voltage generating circuit 43 feeds the mesh electrode 26 with voltage of a +5V but feeds a -12V instead by a signal out of a delay circuit 42 in this case. A quantity of electricity to be detected by a quantity detector 44 becomes reduced to some extent when the optical pulse is made to be incident on the specified photoelectric emission surface. A discriminator 45 discriminates that the incident optical pulse falls upon which part of the photoelectric emission surface.

Description

Detailed Description of the Invention (Technical Field) The present invention involves the generation of photoelectrons on the photocathode by making weak radiation enter the photocathode through a scintillator or the like, or by making the weak radiation enter the photocathode directly, The present invention relates to a radiation detection device that detects radiation by multiplying it by a secondary electron multiplier.

(Prior Art) A photomultiplier tube has excellent characteristics as a device for detecting extremely weak radiation.

Note that in the present invention, radiation is used in a broad sense including at least electromagnetic radiation.

In such a photomultiplier tube, there is a desire to know which region of the photocathode the pulsed light incident on the single photocathode is incident on, and to improve the accuracy of resolving the incident position.

It is also conceivable to arrange a large number of photomultiplier tubes with small light-receiving surfaces in a dense manner in order to improve the accuracy of resolving the incident position. However, there is a limit to making the photomultiplier tube smaller while maintaining a predetermined performance. Furthermore, the ratio of the outer shape of the tube to the photocathode becomes large, and the amount of light that cannot reach the photocathode cannot be ignored.

The above problem could be solved if the position of the light incident on a single photocathode could be known. A photomultiplier tube as shown in FIGS. 1 and 2 is known as a device capable of determining the position of light incident on a single photocathode.

A photocathode 3 is formed on the inner wall surface of an entrance window 2 of a cylindrical vacuum-tight container 1 .

Further, within the inner wall surface of the entrance window 2, there are metal wires 8,9°10
is embedded. By applying an appropriate voltage, which will be described later, to this metal wire, it is possible to divide the photocathode 3 into three virtual regions and find out which region the light is incident on.

The focus electrode 4 is an electrode for forming an electric field that guides photoelectrons emitted from the photocathode 3 to the dynode. A dynode group 5 for multiplying photoelectrons is provided adjacent to the focus electrode 4.

The electrons multiplied by the dynode group 5 are collected by an anode 6 made of a metal net.

A photocathode 3 is installed on the wall surface of the airtight container 1 facing the entrance window 2.
．． Focus electrode 4. A lead wire 7 for applying an appropriate voltage to the dynode group 5 and extracting a signal from the anode F6.
is provided.

Light 1 is applied to the photocathode 3. ．． When a photoelectron is incident, photoelectrons are emitted from the point of incidence. These photoelectrons are guided by the claw electrode 4 and collide with the first stage dynode.

Secondary electrons are emitted from the first stage dynode due to the collision, and these secondary electrons collide with the second stage dynode, which is at a higher potential. Similarly, they collide with each stage dynode in sequence up to the final stage dynode. Repeat and multiply the number,
It is captured by the anode 6.

In the figure, E indicates the trajectory of the photoelectrons and secondary electrons.

Such a photomultiplier tube can be used as a γ-ray detector in combination with a scintillator.

The configuration and operation when used in a γ-ray detector will be explained with reference to FIGS. 3 and 4.

Three scintillators 11°12 that convert gamma rays into visible light
．． 13 are arranged corresponding to the three virtual regions (three regions formed around the metal lines 8, 9, and 10) of the photocathode 3 described above. Furthermore, a shielding plate 18.18 is arranged between adjacent scintillators.

Consider the case where the central scintillator 12 emits light as shown in FIGS. 3 and 4.

When no voltage is applied to the metal wire 9, the electric field distribution is expressed as 14 in FIG.
All of them pass through the road and converge to the first dynode of dynode group 5.

Next, when a positive voltage (approximately 80V) is applied to the metal wire 9,
The electric field distribution 14 formed by the photocathode 3 and the focus electrode 4 is greatly disturbed as shown at 16 in FIG.
Most of the photoelectrons collide with the focus electrode 4 through the trajectory shown in 17. Therefore, the output decreases rapidly.

Using this characteristic, when one of the three scintillators emits light, control pulses are sequentially applied to the metal wires 11, 12, and 13 at appropriate intervals, and the sudden drop in output occurs when the control pulse is applied to which metal wire. By determining this, it is possible to detect which scintillator among the three scintillators has emitted light.

Although the device divides the photocathode 3 into a plurality of regions, some problems remain in manufacturing and operation.

First, there is a problem in that the manufacturing process is extremely complex because the metal wires 11, 12, and 13 are melted into the glass.

In order to determine the incident position, the voltage applied to the metal wire 11 etc. needs to be synchronized with the incident light.

To detect the position of an incident light pulse with a short width,
Although it is necessary to apply a high-speed pulse voltage for the duration, it is not easy to generate the high-speed pulse of about 80V.

Furthermore, since there is capacitance between the metal wires 11, 12, 13 and the photocathode 3, coupling occurs via this capacitance, producing a pulse-like induced voltage in the output circuit, which interferes with signal processing. There is a possibility that

The high-speed pulse voltage needs to be lowered further when the resistance of the photocathode 3 is low.

(Object of the Invention) An object of the present invention is to provide a radiation detection device that solves the above problems.

(Structure and operation of the invention) In order to achieve the above object, the radiation detection device according to the present invention provides a radiation detecting device that includes a photoelectron path from a photocathode of a photomultiplier tube and a specific portion of the photocathode in a space of a first die note. A mesoche electrode is provided at the mesoche electrode, and a voltage is supplied to the mesoche electrode by a gate voltage generation circuit to form an electric field distribution that prevents photoelectrons from reaching the first dynode from a specific portion of the photocathode, and the incident position is A discriminating device determines from the gate voltage and the output of the photomultiplier tube whether the light is incident on the specific portion of the photocathode of the photomultiplier tube or on another portion. It is configured.

In order to detect radiation that cannot cause photoelectrons to be generated by the photocathode, the photocathode can emit photoelectrons from radiation that cannot cause the photocathode to emit photoelectrons in front of a specific part of the photocathode. A first scintillator that converts into radiation is disposed on the front surface of a portion other than a specific portion of the photocathode, and converts radiation that cannot cause the photocathode to emit photoelectrons into radiation that can cause the photocathode to emit photoelectrons. A second scintillator is arranged, and a voltage is supplied to the mesh electrode by a gate voltage generation circuit to form an electric field distribution that prevents photoelectrons from reaching the first die note from a specific part of the photocathode. A position determination device determines from the gate voltage and the output of the photomultiplier tube whether light is incident on the specific portion of the photocathode of the photomultiplier tube or on another portion. The system is configured to determine which scintillator the radiation is incident on.

It is extremely easy to provide the mesoche electrode at the position, and it is possible to easily detect which region of the photocathode the light has entered from the relationship between the voltage applied to the mesoche electrode and the output.

(Description of Examples) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 5 is a sectional view including the tube axis showing an embodiment of the photomultiplier tube used in the radiation detection apparatus according to the present invention, and FIG. 6 is a sectional view taken along a plane perpendicular to the tube axis.

A photocathode 21 is formed on the inner wall surface of the entrance window surface 20 of the vacuum glass airtight container 190.

The photocathode 21 is formed into a rectangular shape with the intention of arranging photomultiplier tubes of the same type closely together. Furthermore, in order to reduce the gap between the phototubes of adjacent photomultiplier tubes when viewed from the incident direction, the shape of the vacuum glass airtight container 19 surrounding at least the photocathode 21 is also square. The focus electrode 22 is a focus electrode for forming an electric field that guides photoelectrons emitted from the photocathode 21 to the dynode.

The dynode group 23 multiplies the photoelectrons, and the multiplied electrons are complemented by the anode 1'' 244 of the metallic mesh.

A lead wire 25 is provided on the surface facing the entrance window surface 20, and the photocathode 21.
Focus electrode 22. A suitable voltage is applied to the dynode 23 and a signal is extracted from the anode 24.

The gate mesh electrode 26 faces the space between the photocathode 21 and the focus electrode 22.

FIG. 7 shows an enlarged view of this mesh electrode 2G.

This electrode 26 is made by etching a thin stainless steel plate, and has a plurality of regular hexagonal holes closely spaced in the portion disposed on the photocathode 21 side.

The mesh electrode part of the gate mesh electrode 26 (the width W of the part shown enlarged in FIG. 7 is approximately 5.8 m,
m, length ■ (is approximately 3.5 mm in size.

The mesh electrode portion of the gate mesh electrode 2G is placed in a vacuum glass airtight container 19 as shown in FIGS. 5 and 6.
(approximately 1 mm) from the side wall of the photocathode 21 to the photocathode 2.
1 and the first dynode of the dynode group 23, approximately l/
They are located at a distance of 10.

Note that the mesh electrode part of the gate mesh electrode 26 is the sixth mesh electrode part.
As shown in the figure, when this photomultiplier tube is in operation, the photocathode 2
1 and the focus electrode 22 as much as possible along the equipotential surface formed by the focus electrode 22.

Next, the operating characteristics of the photomultiplier tube having the above configuration will be explained with reference to FIGS. 8 and 9.

FIG. 8(A) is a circuit showing a connection example for measuring gate characteristics.

The photocathode 21 is grounded, 100 OV is applied to the anode 24, and the voltage therebetween is divided into 150 Ω using a series circuit of many fixed resistors R to supply voltage to the focus electrode 22 and each electrode of the die note group 23. do. The mesh electrode 26 can be selectively supplied with -12V and +5V.

Since the mesh electrode part of the mesh electrode 26 is arranged along the +5 square equipotential plane formed by the photocathode 21 and the focus electrode 22, the mesh electrode part of the mesh electrode 26 is
The shape of the electric field between the photocathode 21 and the focus electrode 22 when is applied is the same as when the mesoche electrode 26 is not present.

When -12V is applied to the mesh electrode 26, the normal electric field distribution is disturbed, and the Ot path of photoelectrons from the photocathode on the mesh electrode side is greatly deviated, and the photoelectrons are not focused on the first dynode. Since the electric field distribution on the side where the mesh electrode 26 is not present is not disturbed, photoelectrons from the photocathode on the side where the mesh electrode 26 is not present are focused on the first stage dynode.

L with peak wavelength 480 nano tn as light source 27
The IED emits light with a pulse width of 80 μsec and a period of 2 KHz, and the photocathode is irradiated through an aperture 27a having an aperture of about lrnmφ.

The light source 27 is moved through the aperture of the aperture plate 27a so as to irradiate the area from the end of the photocathode opposite to the gate mensch electrode 26 to the other end, as indicated by the arrow in the upper right corner of FIG.

The signal multiplied by the dynote group 19 and taken out from the anode 24 is connected to an amplifier 29 via a capacitor 28 and amplified. The output of the amplifier 29 is detected by a detection circuit 30, and the detected output is recorded by an X/Y recorder 31.

FIG. 9 shows a comparison of the characteristics when -12V is applied to the mesh electrode 26 and the characteristics when +5V is applied. In FIG. 9, the X axis represents the direction of movement of the light source 27.
The axis indicates the detection output of the detection circuit 30.

0 on the X-axis indicates the center of the photocathode, and the left side is the mesh electrode 2.
On the photocathode on the side that does not correspond to 6, the right side is the mesh electrode 26
The position on the photocathode on the side corresponding to is shown. A curve 32 shows the characteristics when +5V is applied to the mesh electrode 26, and a curve 33 shows the characteristics when -12V is applied to the mesh electrode 26.

As can be seen from this figure, when -12V is applied to the mesoche electrode 26, the photoelectrons emitted from the photocathode on the right side corresponding to the mesoche electrode 26 are suppressed and hardly contribute to the output. Further, when +5V is applied to the mesoche electrode 26, no influence of the mesoche electrode 26 appears.

The region of the photocathode that emits photoelectrons that are prevented from reaching the first stage dynode when a certain voltage is applied to the mesoche electrode 26 as described above will hereinafter be referred to as a specific portion of the photocathode.

FIG. 10 is a block diagram showing a first embodiment of the radiation detection device according to the invention. The object of detection in this embodiment of the apparatus is the incidence of an optical signal pulse that lasts for a relatively short fixed period of time and its incidence position.

The output of the phototube is amplified by an amplifier 40. The output of the amplifier 40 is connected to an energy discriminator 41 and a current detection circuit 44.

Energy discriminator 41 generates a signal from the time it determines that the output of amplifier 40 is caused by an optical signal pulse.

The delay circuit 42 is connected to the energy discriminator 41
The signal is delayed by a certain period of time sufficiently shorter than the duration of the optical signal pulse, and is then supplied to the gate voltage generation circuit 43.

The gate voltage generation circuit 43 is currently supplying a voltage of +5 volts to the mesoche electrode 26, but the delay circuit 42
A voltage of 112 volts is supplied to the mesh electrode 26 by a signal from the .

As mentioned above, if the photoelectrons from the photocathode are from a specific part of the photocathode, the photoelectrons cannot reach the first stage dynode after that, so the output of the photomultiplier tube sharply decreases.

When the photoelectrons from the photocathode are not from the mesh electrode 26 side, that is, when they are not from a specific photocathode, the photoelectrons are not affected by the voltage change of the mesh electrode 26.
The output of the photomultiplier tube is not reduced.

The output of the amplifier 40 and the output of the electric quantity detector 44 are connected to the discriminator 45 .

The quantity of electricity detected by the quantity of electricity detector 44 is smaller when the optical pulse is incident on a specific photocathode than when the optical pulse is incident on a photocathode other than the specific photocathode.

The discriminator 45 discriminates from the signal from the energy discriminator 41 and the output of the electric quantity detector 44 which part of the photocathode 21 the optical pulse is incident on.

Next, a second embodiment for gamma ray detection will be described.

FIG. 11 is a diagram showing the positional relationship between the photomultiplier tube and the scintillator in the second embodiment, FIG. 13 is a block diagram showing the second embodiment of the radiation detection device according to the present invention, and FIG.
The figure is a waveform diagram for explaining the operation of the second embodiment device.

In front of the photomultiplier tube 19, two bismuth germanate lentilators (hereinafter referred to as BGO) 3 are installed as gamma ray detectors.
4.35 and a shielding plate 36 are arranged.

The BGO 34 is made to correspond to the photocathode on the side that does not correspond to the mesoche electrode 26, that is, to the photocathode that is not a specific part of the photocathode.

The BGO 35 is located on the side of the photocathode corresponding to the mesh electrode 26, that is, in front of a specific portion of the photocathode 12.

FIG. 12 shows the light emission waveform of BGO.

The time constant (time to reach 1/e of the peak, e is the base of the natural logarithm) of the BGO emission waveform is 300 nano sec.

This second embodiment is configured to apply -12V to the mesh electrode after a sufficient period of time to determine that the pulse waveform is due to light emission from BGO, that is, approximately 150 nano seconds after the pulse reaches its peak. There is.

The basic configuration of the circuit portion in the block diagram shown in FIG. 13 is the same as that described above with reference to FIG. 10.

The output of the phototube is amplified by an amplifier 40. The output waveform of this amplifier 40 is shown in FIG. 14 (40). The output of this amplifier 40 is an energy discriminator 41-
and a current detection circuit 44. The energy discriminator 41 determines whether the output of the amplifier 40 is caused by the BGO light emission or is noise, and when it is determined that the output is caused by the BGO light emission, it outputs a signal near the peak of the BGO light emission. will occur.

The output of the energy discriminator 41 is shown in (41) in FIG.

The delay circuit 42 is connected to the energy discriminator 41
The signal is delayed by 150 nano 5 ec (=τ), which is sufficiently shorter than the duration of the pulse caused by the light emission of the BGO, and is supplied to the gate voltage generation circuit 43. The output of the delay circuit 42 is routed to (42) in FIG.

As shown in (43) in FIG. 14, the gate voltage generation circuit 43 supplies a voltage of →-5polI- to the me-noche electrode 2G during lightning, but due to the signal from the delay circuit 42, , a voltage of -12 pol l· is supplied to the mesh electrode 26.

At time tl in FIG. 14, gamma rays enter the BGO 34, and a specific portion of the photocathode 21 emits photoelectrons.

Since the mesoche electrode 26 is initially maintained at +5 volts, it does not prevent the photoelectrons from proceeding to the first stage dynode, so a wave wave corresponding to the light emission of the BGO shown in FIG. 12 appears from the amplifier 40. .

The energy discriminator 41 determines that the output of the amplifier 40 is the cause of the light emission of the BGO, and as shown in FIG.
150 nano s after outputting the waveform shown in 41)
When a voltage of 112 volts is applied to the mesh electrode 26 after a delay of ec, photoelectrons from a specific portion of the photocathode 21 cannot reach the first stage dynode.

As a result, the output of the photomultiplier tube decreases rapidly, and the output of the amplifier 40 also decreases, as shown in FIG. 4 (40).

The output of the electric quantity detector 44 is less than the electric quantity corresponding to one light emission.

The discriminator 45 receives information from the energy discriminator 41 that there is a signal that causes the BGO to emit light, and
Based on the information that the output of the electric quantity detector 44 is less than the electric quantity corresponding to one light emission, it is determined that light was incident on a specific part of the photocathode 21, that is, that γ rays were incident on the BGO 34. output.

Assuming that γ rays are incident on the BGO 35 at time tl in FIG. 14, photoelectrons are emitted from a portion of the photocathode 21 other than a specific portion. As mentioned above, the energy discriminator 41 determines that the output of the amplifier 40 is caused by the light emission of BGo, and outputs the waveform shown in FIG. 4 (41) for 150 nan.

After a sec delay, a voltage of 112 volts is applied to the mesh electrode 26.

Photoelectrons from areas other than a specific portion of the photocathode 21 are not affected by the mesoche electrode 26 and all reach the first stage Geuinault.

As a result, a sudden drop G and L in the output of the photomultiplier tube does not occur, so the quantity of electricity detector 44 can detect the quantity of electricity corresponding to one emitted light.

The discriminator 45 receives information from the energy discriminator 41 indicating that there is a belief that the emission of BGO is caused, and
From the information that the electric quantity detector 44 detected the electric quantity corresponding to one light emission G, it is determined that light was incident on a part other than the specific part of the photocathode 21, that is, that γ rays were incident on the BQO 35. Generate the determined output.

The embodiments above have been described in detail in which one mesh electrode is placed in the center of the vacuum vessel to divide the photocathode into a specific part and other parts. can be modified.

It is also possible to provide 21[1i1 or more mesoche electrodes, thereby making the specific portion of the photocathode 2 or more.

In this case, by arranging three or more scintillators in corresponding portions, one photomultiplier tube can distinguish the light emissions of three or more scintillators.

Although an example of gamma ray detection was shown in the second embodiment,
By using an appropriate scintillator, the incident position of radiation other than electromagnetic waves can be divided into multiple regions and detected using a single photomultiplier tube.

(Effects of the Invention) As explained above, in the radiation detection device according to the present invention, by providing a mesh electrode and controlling the behavior of photoelectrons in a specific part of the photocathode, photoelectron multiplication with a single photocathode is possible. The tube can essentially function as two or more photomultiplier tubes.

Providing the mesoche electrode between the photocathode and the first stage dynode is extremely simple and controllable.

This gate mesh electrode 26 is assembled using the photomultiplier tube shown as the prior art described above, and the metal wire 11,
Compared to the process of melting 12.13 into the bottom of a vacuum-tight container, it is non-electrically simple.

The voltage applied to the mesoche electrode is an extremely low voltage as shown in the embodiment, and is suitable for high-speed operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a conventional photomultiplier tube, and is a sectional view taken along a plane including the tube axis. FIG. 2 is a cross-sectional view of the entrance window of the photomultiplier tube taken along a plane perpendicular to the tube axis. FIGS. 3 and 4 are schematic diagrams for explaining the operation when the photomultiplier tube and scintillator are used in combination. FIG. 5 is a diagram showing an embodiment of a photomultiplier tube used in a radiation detection apparatus according to the present invention, and is a sectional view taken along a plane including the tube axis. FIG. 6 is a cross-sectional view of the photomultiplier tube taken along a plane perpendicular to the tube axis. FIG. 7 is an enlarged plan view of a part of the mesoche electrode of the photomultiplier tube. FIG. 8 is a circuit diagram showing an example of a circuit for measuring the operating characteristics of the photomultiplier tube. FIG. 9 is a graph showing the measurement results. FIG. 10 is a block diagram showing a first embodiment of the radiation detection apparatus according to the present invention. FIG. 11 is a schematic diagram showing the relationship between the scintillator and the photomultiplier tube in the first embodiment of the radiation detection device according to the present invention. The %12 diagram is a graph showing the response characteristics of a bismuth germanate scintillator. FIG. 13 is a block diagram showing a second embodiment of the radiation detection apparatus according to the present invention. FIG. 14 is a waveform diagram for explaining the operation of the second embodiment device. 1... Vacuum glass airtight container 2... Inlet window of vacuum glass airtight container 3... Photocathode 4... Focus electrode 5... Dynode group 6... Anode 7... Lead wire 8, 9. 10...Metal wire for gate 11.12.1
3... Scintillator 14... Electric field distribution when no gate is applied to a conventional photomultiplier tube 15... Electron trajectory when the electric field distribution of 14 is applied 16... To a conventional photomultiplier tube Electric field distribution when the gate is applied 17...Electron trajectory 18 when the electric field distribution is 16...Shielding plate 19...Vacuum glass airtight container 20...Incidence window surface 21 of the vacuum glass airtight container... - Photocathode 22... Focus electrode 23... Dynode group 24... Anode 25... Lead wire 26... Mesoche electrode for gate 27... Light source for measurement 28... Capacitor 29... Amplifier 30...Detection circuit 31...X-Y recorder 34.35...Scintillator 36...Shielding plate 39...Photomultiplier tube 40...Amplifier 41...Energy discriminator 42 ...Delay circuit 43...Pulse generator 44...Electrical quantity detector 45...Discriminator Patent applicant 1) Sakae Naka - Representative of Hamamatsu Botonics Co., Ltd. Patent attorney Hisashi Inoro Figure 1 Figure 2 Figure 11 Figure 12

Claims (6)

[Claims] (1) A mesoche electrode is provided on the path of photoelectrons from a specific part of the photocathode in the space between the photocathode of the photomultiplier tube and the first dynode, and a gate voltage generation circuit is used to connect the mesoche electrode to a specific part of the photocathode. A voltage is supplied to form an electric field distribution that prevents photoelectrons from reaching the first dynode, and a discriminating device determines whether the photoelectrons on the photocathode of the photomultiplier tube are A radiation detection device configured to determine whether light is incident on a specific part or another part. (2) The mesh portion of the mesh electrode is arranged along an equipotential surface in the path of photoelectrons from a specific portion of the photocathode in the space between the photocathode of the photomultiplier tube and the first guinaut. A radiation detection device according to claim 1. (3) The gate voltage generation circuit normally applies a voltage equal to the voltage of the space where the mesh electrode is arranged, and when necessary, applies a voltage lower than the voltage of the space where the mesh electrode is arranged. The radiation detection device according to claim 2, which applies a voltage. (4) The discrimination device detects the incidence of an optical signal from the output of the photomultiplier tube, and when the optical signal is incident, the gate voltage generation circuit causes the me-noche electrode to detect a specific portion of the photocathode. A patent claim that determines that light is incident on a specific portion of the photocathode when there is a decrease in output when a voltage is supplied to form an electric field distribution that prevents photoelectrons from reaching the first dynode. The radiation detection device according to item 1. (5) A mesoche electrode is provided in the path of photoelectrons from a specific part of the photocathode in the space between the photocathode of the photomultiplier tube and the first guinaut, and a mesoche electrode is provided on the path of photoelectrons from a specific part of the photocathode in front of the specific part of the photocathode. disposing a first scintillator that converts radiation that cannot be caused to emit into radiation that allows the photocathode to emit photoelectrons, and causing the photocathode to emit photoelectrons in front of a portion other than a specific portion of the photocathode; A second scintillator is disposed that converts radiation that cannot be emitted by the photocathode into radiation that allows the photocathode to emit photoelectrons, and a gate voltage generation circuit causes the mesoche electrode to transfer photoelectrons from a specific portion of the photocathode to the first scintillator. A determination device determines whether light is incident on the specific portion of the photocathode of the photomultiplier tube from the gate voltage and the output of the photomultiplier tube. By determining whether the
A radiation detection device configured to determine which scintillator has received radiation. (6) The radiation detection device according to claim 5, wherein each of the scintillators is a bismuth germanate scintillator that converts gamma rays into visible light.