JP2001013251A - METHOD AND DEVICE FOR DETERMINING INCIDENCE DIRECTION OF gamma RAY FROM TRACE IMAGE OF BOUNCING ELECTRON BY MSGC - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and device for determining the incidence direction of γ rays from the trace image of recoil electrons by an MSGC for rapidly and securely determining the incidence direction of γ rays without using any collimators. SOLUTION: The device is provided with a drift electrode 11 that becomes a window, a gas package 12, a long drift region 15 with a plurality of field wires 13, a capillary plate 14, an MSGC 16, and a data collection system 20. Gas in a detection region is ionized by bouncing electrons in the gas package 12, and the electrons drift along a drift electric field being adjusted so that they are vertical to a detection surface, reach the capillary plate 14 that is an intermediate amplifier, and are subjected to gas amplification. Further, the amplified electrons drift to the MSGC 16 and generate a signal by a two-dimensional electrode, and a position is recorded at each high-speed time by the data collection system 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for determining a gamma ray incident direction from a trajectory image of recoil electrons by an MSGC (microstrip gas chamber).

[0002]

2. Description of the Related Art γ-rays (here, γ-rays
Is about 1 MeV), which is the most energetic electromagnetic wave, has very high rectilinearity like light, and has excellent permeability of a substance more than X-rays. The use of isotope nuclei that generate X-rays allows chemicals,
It is used in many fields, including biology, medicine, and pharmacy.

[0003] In particular, for use in the medical field, gamma-ray image diagnosis is currently used for many diagnoses such as cancer and tumor. The applicable organs are brain, heart, lung, liver,
It is widely used in most fields such as cardiovascular and bone.
Most use radioisotopes that emit gamma rays around 140 keV, and capture those gamma rays with a gamma ray detector that limits the direction in which the collimator can detect the gamma rays to obtain an image.

[0004] Investigations using γ-rays have also been attempted for biological and industrial uses.

On the other hand, in nuclear power utilizing nuclear reactions, gamma rays must be shielded because they are dangerous.
The contamination can be investigated by looking for the line.

As described above, γ-rays in the energy range are indispensable to the current state-of-the-art technology, and it can be said that improvement and improvement of the detection method have a great effect not only on science but also on industry.

[0007] In a field that requires the detection of γ-rays, the energy of the γ-rays is determined according to the purpose of the detection, and the spectrum analysis for determining the substance that has emitted the γ-rays,
Further, it is necessary to detect an image by γ-rays. For the former, various scintillation crystals and the like have been developed and many devices have been used.

On the other hand, since γ-rays do not have reflection and refraction phenomena like light and X-rays and cannot be applied to an optical method, it is almost impossible to take an image.

[0009]

However, in the above-mentioned use of γ-rays in the conventional medical field, the positional resolution is determined by the size of the collimator, and the collimator itself generates gamma rays in the background to increase noise. Would. For this reason, the detection is such that a shadow is seen rather than an image, and it is almost impossible to obtain a three-dimensional image. Also, as a practical matter, only a small part of the gamma rays entering the collimator can be used for diagnosis, so a strong dose was absolutely necessary to take the whole image, resulting in an increase in patient exposure. .

[0010] Recently, PET (Pos) has been considered as a decisive factor in the early detection of very early cancers that cannot be detected by other tests.
itron Emission Tomography
A method using is now available. PET is an excellent detector that can obtain a high positional resolution of several millimeters and a three-dimensional image by capturing 2γ rays generated simultaneously from positron / electron annihilation. However, the equipment is very expensive, and an accelerator for producing a special isotope is also required, and there are only about 20 nationwide.

[0011] Apart from this, there is also a method of determining the gamma ray incident direction using the double Compton effect, but the efficiency is still very poor. This is not described here.

As described above, without using a collimator, γ
If the direction of arrival of a line can be detected, a highly efficient and highly accurate gamma-ray direction detector can be produced, which is incomparable to conventional methods. Here, the target γ of about 100 keV to 1 MeV
The interactions that lines cause with ordinary substances are mainly the photoelectric effect and the Compton effect. In each case, recoil electrons are generated in the substance as a result of this action. The direction of this recoil electron has a certain probability distribution with respect to the direction of the incident γ-ray, and its energy is constant in the photoelectric effect and has the energy corresponding to the recoil angle in the Compton effect.

Table 1 summarizes the scattering angle and energy of recoil electrons in each effect.

[0014]

[Table 1]

According to this table, if the direction and energy of recoil electrons generated by incident gamma rays in a substance can be measured,
It can be seen that the incident direction can be determined only by gamma rays of several events.

In view of the above circumstances, the present invention provides a method of determining a gamma ray incident direction from a recoil electron trajectory image by MSGC, which can quickly and reliably determine a gamma ray incident direction without using a collimator. And an apparatus therefor.

[0017]

According to the present invention, there is provided a method for determining a gamma ray incident direction from a trajectory image of recoil electrons by MSGC. The elementary process is identified, the candidate of the incident direction of the incident γ-ray is estimated by the photoelectric effect, the candidate of the incident direction of the incident γ-ray is estimated by the Compton effect, and the γ-ray is estimated by the recoil electron observation of multiple events. The incident direction is determined.

[2] In the apparatus for determining the γ-ray incident direction from the trajectory image of recoil electrons by MSGC, a drift electrode serving as a window, a gas package, a long drift region having a plurality of field wires, a capillary plate, MSGC and a data collection system, wherein the recoil electrons in the gas package ionize the gas in the detection area, wherein the electrons drift along a drift electric field adjusted to be perpendicular to the detection surface; Reaching the capillary plate, which is an intermediate amplifier, gas-amplified, and further drifts the amplified electrons to the MSGC and generates a signal at a two-dimensional electrode, which is recorded at a high-speed time by the data collection system. It is made to be done.

[3] In the apparatus for determining the γ-ray incident direction from the trajectory image of recoil electrons by MSGC, a drift electrode serving as a window, a gas package, a long drift region having a plurality of field wires, and the long drift region A photodetector and a capillary plate placed beside
MSGC and a data collection system, wherein the recoil electrons in the gas package ionize the gas in the detection area,
In order to determine the instantaneous time at which the gamma ray caused the photoelectric / Compton effect in the gas, the photodetector captured the light generated by the ionized gas and the electrons were adjusted to be perpendicular to the detection surface. Drift along the drift electric field,
Reaching the capillary plate, which is an intermediate amplifier, gas-amplified, and further drifts the amplified electrons to the MSGC, and generates a signal at a two-dimensional electrode, which is recorded at a high-speed time by the data acquisition system. That's what I did.

[4] MSG according to the above [2] or [3]
In the apparatus for determining the γ-ray incident direction from the image of the trajectory of recoil electrons by C, the gas package is filled with a gas based on Xe.

[5] In the apparatus for determining a γ-ray incident direction from a trajectory image of recoil electrons by MSGC described in [4], the gas package is capable of adjusting the pressure of Xe.

[0022]

Embodiments of the present invention will be described below in detail.

With a conventional detector, it has been impossible to determine the direction and energy of a recoil electron with energy of about several tens keV to several hundred keV generated by γ-rays in a substance. However, it is thought that this can be achieved by using a two-dimensional microstrip gas chamber (MSGC) and a pipeline data processing circuit for MSGC, which have recently been put to practical use by the group of the present inventors. Here, description of the MSGC is omitted. If necessary, refer to
See 300856, Patent Publication No. 2843319, and the like.

FIG. 1 is a diagram showing the principle of two-dimensional reading of a charged particle trajectory using time information according to the present invention.

In this figure, 1 is an MSGC, 2 is a drift electrode, 3 is a drift electric field (E electric field), 4 is a gas atmosphere, 5 is a detector, 6 is a detection signal by the detector, and 7 is an electron cloud.

As shown in this figure, the MSGC 1 performs position detection by drifting an electron cloud 7 generated in a gas atmosphere 4 in a detection area to an electrode by a drift electric field 3 and further performing gas amplification. . Here, the electron cloud 7
Is a linear one generated by fast charged particles, the electron cloud 7 drifts to the electrode while maintaining its shape, and the signal 6 appears one after another at a position corresponding to the shape of the electron cloud 7. Become.

That is, in the conventional MSGC and the high-speed data acquisition system, the three-dimensional trajectory of the first high-speed charged particle can be obtained by continuously recording the signal position and the detection time.

A method of capturing the three-dimensional trajectory of a charged particle by a similar method is used in the field of high energy physics to observe particles of several MeV or more (Time).
Projection Chamber: TPC)
In MSGC, even a low energy electron (several tens keV) whose track is about several mm can be observed with high accuracy.

Further, the energy of the recoil electrons can be determined from the length of the trajectory (or the deposit energy that can be detected by MSGC). The following steps need to be performed to obtain the original incident direction of γ-rays from these information.

(1) Identification of Physical Elementary Process that Generated Recoil Electrons As described above, there are two processes of generating recoil electrons caused by γ rays of 1 MeV or less, the photoelectric effect and the Compton effect. In the photoelectric effect, in order to absorb all the energy E _in the γ rays entering, the kinetic energy E _out of recoil electrons will be limited to a constant value E _in -W regardless of the electron motion direction. Here, W is the binding energy of electrons generated by the photoelectric effect.

On the other hand, the Compton effect is considered to be quasi-elastic scattering of photons and electrons, and the kinetic energy of recoil electrons depends on the scattering direction, but this energy is smaller than that due to the photoelectric effect.

Therefore, it can be said that the energy of recoil electrons should be used for discriminating the two elementary processes. Assuming that the gamma rays to be detected come from a certain nuclide,
Since the energy is known, the electron energy due to the photoelectric effect always has a constant value. In other words, if anything lower than this energy is observed, it is Compton effect.

(2) Estimation of Candidates of Incident Gamma-Ray Incident Direction (In the Case of Photoelectric Effect) The differential cross section of the scattering angle of electrons generated by the photoelectric effect is given by dφ, where θ is the angle between the incident γ-ray and the scattered electrons. It is known that ∝ ｛sin ² θ / (1−β cos θ) ⁴ ｝ d θ (1) Here, β is the ratio between the initial speed and the light speed of the recoil electrons. When the energy of the incident γ-ray is sufficiently small with respect to the electron mass (511 keV), photoelectrons are emitted in a direction substantially perpendicular to the incident γ-ray. However, as the incident energy becomes higher, the emission direction of the electron becomes larger due to the relativistic effect. It is biased forward.

FIG. 2 shows the direction of electron generation at several energies from 50 keV to 800 keV.

The azimuthal distribution of the scattered electrons depends on the degree of polarization of the incident γ-ray, but assuming that there is no polarization, the distribution in the azimuthal direction is exactly the same.

Therefore, as shown in FIG. 3, the direction on the cone corresponding to FIG. 2 (accurately, a certain probability distribution centered on the cone) corresponding to FIG. It becomes a candidate for the incident direction. In FIG. 3, 8 is an electron track, and 9 is an incident γ-ray candidate cone.

(3) Estimation of Candidates of Incident γ-ray Incident Direction (Compton Effect) When the trajectory of the recoil electron is due to the Compton effect, the incident direction of the γ-ray having energy E _in and the recoil electron The relational expression between the formed angle θ and the electron energy E _out is as follows.

{(1 / E _in -E _out )-(1 / E _in )} = (1 / mc ² ) (1-cos θ) (2) where mc ² is the rest mass of the electron. . That is,
If the energy of the incident γ-ray and the recoil electron is known, this equation can be solved for θ, and the cone of the trajectory of the recoil electron in the direction of the angle θ (see FIG. 3) indicates the incident direction of the γ-ray. Candidate.

(4) Determining the incident direction of γ-rays by observing recoil electrons of a plurality of events According to the above method, the observation direction of a single recoil electron greatly restricts the arrival direction of the original γ-ray in space. , A plurality of γs coming from the same direction
By observing recoil electrons caused by the line incidence, the direction of incidence can be determined from the overlap of candidates for the γ-ray incidence direction obtained from each. When the incident direction is uniquely determined by the overlap of the cones, at least three events of γ-ray incidence are required. Also, in the case where γ-rays arrive from a plurality of directions, it is possible to determine the incident direction by processing the superposition of cones calculated from the observed recoil electrons on a computer. (See FIG. 4). In FIG. 4, A is a γ-ray incident direction obtained from a plurality of events, and B is a γ-ray incident direction candidate obtained from one recoil electron.

According to this method, a collimator for capturing γ-rays is not required, and a detector having a large detection area can be used. It is considered that a line direction detector can be realized.

Next, a specific embodiment will be described.

As the γ-ray direction detector, there are a case where a source relatively far from the detector is checked and a case where a source close to the detector is checked.

The former examines only the direction of incident γ-rays with respect to the detector, and is considered to be very useful in the field of radiation safety management (detection of radiation leakage and investigation of radioactive waste activation sites). .

In the latter, since the solid angle of the detector with respect to the radiation source becomes large, it can be expected that the spatial position of a low-capacity radioactive substance can be specified, and the latter should be used in combination with a radioactive tracer for medical use. Thus, it is considered that medical treatment that is much easier to handle and less dangerous than before can be performed with high accuracy.

The embodiments of the γ-ray direction detector for the long distance and the short distance are slightly different from each other.

FIG. 5 shows an MSGC showing a first embodiment of the present invention.
FIG. 2 is a schematic diagram of a device for determining a direction of incidence of γ-rays from a trajectory image of recoil electrons according to FIG.

In this figure, 10 is a gamma ray arrival direction detecting device, 11 is a drift electrode (window), 12 is a gas package, 12A is a gas package side wall, 13 is a field wire (electric field structure line), 14 is a capillary plate, 1
5 is a long drift region, 16 is an MSGC, and 20 is a data acquisition system.

Here, a long drift region 15 is provided in the MSGC with an intermediate amplifier (capillary plate). Since the long drift region 15 emphasizes the linearity of the electric field, a field wire (electrode for adjusting electric field) 13 for correcting the drift electric field is provided around the long drift region 15. The inside of the γ-ray arrival direction detecting device 10 is filled with a gas based on Xe to increase the detection efficiency for γ-rays. The field wire 13 is connected to the gas package side wall 12A.
It is stretched around. That is, the inside of the gas package becomes hollow, and accepts γ-rays.

The portion in which the gas is sealed is a pressure vessel, and the internal gas pressure can be increased according to the necessity of the energy and efficiency of the γ-ray to be detected. I have. The recoil electrons ionize the gas in the detection region, and the electrons drift along a drift electric field adjusted to be perpendicular to the detection surface, reach the capillary plate 14 as an intermediate amplifier, and are gas-amplified. .

Further, the amplified electrons drift to the MSGC 16 and generate signals at two-dimensional electrodes arranged at 200 μ intervals.
The position is recorded every 0 to 100 nsec. The drift speed of electrons at 1 atmosphere and room temperature in xenon gas is about 2 cm / μsec when the electric field is 300 V / cm. In this case, the depth of the detector is determined by collecting data every 50 nsec. Of the recoil electron trajectory at 1 mm intervals in the direction
Data corresponding to the dimensional structure is obtained.

Here, it should be noted that, in the case of the MSGC having such a long drift region 15, positive ions generated by avalanches of electrons generated near the electrodes flow into the drift layer, and the gas package side walls 12A made of an insulator. This has the property of adhering to the surface and causing charge-up and distorting the electric field. Therefore, the capillary plate 14 placed on the MSGC 16 absorbs all the positive ions formed in the lower part by the electrodes of the capillary plate 14, thereby reducing this effect. Can be eliminated. Therefore, the device of the present invention does not distort the electric field even in a strong radiation environment for a long time, and can accurately measure the γ-ray incident direction.

FIG. 6 shows an MSGC according to a second embodiment of the present invention.
FIG. 4 is a schematic diagram of a device for determining a direction of incidence of γ-rays from a trajectory image of recoil electrons according to FIG.

In the γ-ray direction detector for the short distance, when obtaining a three-dimensional image of the recoil electrons, it is necessary information that the position (depth) in the detector at which the three-dimensional image occurred. This information is obtained from the time when the drift electrons are generated, that is, the difference between the arrival time of the γ-rays and the time when the drift electrons reach the MSGC 16.

Therefore, the structure of the detector for the short distance, in addition to the detector for the long distance, determines the instant when the γ-ray causes the photoelectric / Compton effect in the gas. A high-speed photodetector 17 (a detector capable of capturing one photon with an accuracy of several nanoseconds, such as a photomultiplier tube) for capturing light (scintillation) is arranged beside the drift region. The trigger signal generated from the photodetector 17 is also sent to the data collection system 20. The other configuration is the same as that of the first embodiment, and the description is omitted here.

Further, 1M is commonly used for long distance and short distance.
In order to measure the energy when observing a γ-ray near eV, the structure may be such that a magnetic field can be applied to the detection region as needed.

FIG. 7 is a block diagram of an MSGC data collection system according to an embodiment of the present invention.

In this figure, an MSGC data collection system 20 includes an encoder system 21, a memory module 22, a clock 23, and a counter (time stamp).
24, a computer system 25. Note that 16
Is an MSGC, 17 is a photodetector, and 26 is a trigger signal.

As shown in FIG. 7, the structure is basically the same as that of the conventional high-speed data acquisition system for imaging. However, it is possible to improve the accuracy of time recording for capturing the three-dimensional structure of the trajectory. I have. In other words, when two-dimensional coordinates are obtained with a conventional two-dimensional strip-type detector, a track created by such a particle having a speed close to the speed of light is one event. It was not possible to capture the position of the strip by recording it. A solution to this problem is to attach a circuit to each pixel as a row of pixels called a strip in the direction of position, and record the hit pad, the hit of the strip in the remaining direction, and the time of this track. For the first time, it was possible to capture the three-dimensional position of the particle track in each strip and capture the entire track. This is TPC (Time Project)
ion Chamber). Read analog signals from both ends of the strip in one direction without using other pads,
JE to get the position of a particle track on its strip
There is a method called T-Chamber. In the case of TPC, the circuit increases in proportion to the area. Also, JE
In the case of T-Chamber, the position resolution is poor and an ADC circuit for converting many analog signals is required.

The high-speed data acquisition system 20 for imaging of the present invention synchronizes signals from each strip with a high-speed clock 23. That is, a hit of each strip in one clock 23 becomes one event. An electron drifting from a normal particle track has a variation of about microsecond, so that a clock 23 of about 10 MHz is used.
When the data is obtained by using, the track is easily recorded as data of about 10 continuous points in one track. The system measures the perimeter rather than the detector area,
That is, since it increases only by the square root of the area and does not require any analog processing, it is possible to process a large number of events in a small size. That is, in the conventional data collection system, data collection is performed with a 10 MHz clock and time recording is performed at a maximum of every 10 clocks (1 μsec resolution), whereas the high-speed data collection system 20 for imaging of the present invention is used. Then, the time for each clock 23 is recorded. Further, the timing of the trigger signal 26 from the photodetector 17 can be recorded as data in the short distance system.

The data captured by the data collection system 20 can be directly captured by the computer system 25, from which the direction of the incident gamma ray is calculated. The direction of emission from the locus of the recoil electrons in space and the energy from the length can be measured. Regarding the energy, in the case of high energy γ-ray incidence near 1 MeV, there is a possibility that many recoil electron trajectories may not fit in the detector. In this case, a magnetic field is applied to the detection area, and electron trajectories are applied. By observing the curvature at which the is bent, the energy of the recoil electrons can be obtained. Once these values are obtained, the direction of the incident γ-ray can be determined from the trajectories of several events as described above.

In the case of a short-distance object, the distance to the radiation source can be specified by a method similar to triangulation using the difference in the position of the locus in the detector. Even when observing a long-distance source, the spatial position of the source can be similarly detected by triangulation using a plurality of detectors. It is considered that these calculations can be performed almost instantly using a current computer, and it is also possible to record and display the incident direction of γ-rays in real time.

Next, the results of the operation test will be described.

Since the structure is often common with the conventional MSGC, a basic phenomenon has been observed using the conventional MSGC.

FIG. 8 shows an image obtained when the apparatus is operated for 10 seconds without incident on the MSGC.

Generally, on the ground, 1 cm ²
About 0 ^-2 μ particles are pouring down.
What can be seen as its trajectory is clearly observed. The current data collection system cannot accurately record the time sequence of the obtained point sequence, but here, since the data collection is performed with a 10 MHz clock, each point is obtained every 100 nsec. (C in FIG. 8)
See).

Here, since the electron density at which recoil electrons generated by γ-rays are much higher than the density of ionized electrons generated by the passage of μ-particles originating from cosmic rays, at least the trajectory of the μ-particles can be seen. This indicates that recoil electrons of γ-rays will be easily observable as well.

This MSGC has a drift region thickness of 5
mm, and the electric field applied here is about 200 V /
cm, data collection 100 ns, gas composition xenon 7
0%: Ethane was 30%, so that the trajectory of the μ-particles penetrating this drift region appears as a sequence of 5 to 6 points. This is evidence that the MSGC is operating as a TPC, and the trajectory of the charged particle is 1 mm in the depth direction.
This indicates that the three-dimensional particle trajectory is recorded in units.

As described above, the apparatus according to the present invention uses the P
A three-dimensional position resolution higher than ET can be obtained for a single γ-ray source in this energy region, and has a large solid angle of 2π steradian (2π str: a substantially hemispherical region). Also, since no collimator is required, the background is greatly reduced. Therefore, for example, when used in the medical field, a single gamma ray source can obtain a position resolution and a time resolution higher than PET while reducing the exposure of the patient to 1/100 or less of that of the conventional art.

Also, for the detection of 2 gamma ray decay, this device can capture recoil electrons (mostly 200 keV or less, which are completely captured by this device) generated by Compton scattering from 500 keV. The position can be detected with the same accuracy. In the case of medical use, since the energy of the gamma ray is known, the direction of the gamma ray is obtained only from the direction and the energy of the electron as described above. That is, detection of only one gamma ray is sufficient. In addition, the detection efficiency is also improved several hundred times because of the large solid angle. If you want to increase the sensitivity, place a scintillator plate detector (not necessary to be a pixel) on the opposite side of the detector to reduce noise, and call 2 gamma ray events in simultaneous measurement and energy measurement. Can be identified.

As described above, the concept of the conventional gamma ray diagnosis is renewed, and a capability close to X-ray CT is obtained.

Next, biological and industrial use will be described.

In this field of use, it is possible to examine the flow of an isotope-based tracer in real time, as in medical use, and in real time the movement in a remote object much larger than the detector. For example, a substance whose amount of a substance can transmit a certain amount of gamma rays, such as the location of a reaction in a reactor, the degree of progress, the degree of diffusion, etc., can usually capture the movement of the tracer.

This detector obtains the angle of a gamma ray, and the closer the detector is, the higher the position resolution. Therefore, in a small animal used in biology, pharmacy, and medicine, the distance between the radiation source and the detector can be reduced, so that the positional resolution is increased, and the position of a part can be determined for the small animal.

Furthermore, in the nuclear power field, there is no method other than checking the entire area using a conventional surveyor, such as checking the state of contamination over a wide area before work and checking the exposure of the entire human body after work, and it is time-consuming and has low reliability. Is greatly improved in both quality and time.

The present invention is also applicable to a two-dimensional gas proportional coefficient device in which the distance between the electrodes is 1 mm or less.

The present invention is not limited to the above-described embodiment, but various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0077]

As described above, according to the present invention, the following effects can be obtained.

(1) The γ-ray incident direction can be quickly and reliably determined without using a collimator.

(2) It is also possible to record and display the incident direction of the γ-ray in real time.

(3) By filling the gas with xenon gas, the detection efficiency for γ-rays can be increased.

(4) By adjusting the pressure of the xenon gas, the detection efficiency for γ-rays can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of two-dimensional reading of a charged particle trajectory using time information according to the present invention.

FIG. 2 is a diagram showing a direction in which recoil electrons are generated by the photoelectric effect of the present invention.

FIG. 3 is a diagram showing candidates for the incident γ-ray direction obtained from the recoil electron trajectory of the present invention.

FIG. 4 is a diagram in which a direction in space represented by a cone of the present invention is replaced with a plane.

FIG. 5 is a schematic diagram of a long-distance γ-ray direction detecting MSGC showing the first embodiment of the present invention.

FIG. 6 is a schematic diagram of a short-range γ-ray direction detecting MSGC showing a second embodiment of the present invention.

FIG. 7 is a block diagram of a data collection system for MSGC showing an embodiment of the present invention.

FIG. 8 is a diagram showing a trajectory of muons captured by the MSGC for gamma ray direction detection of the present invention.

[Explanation of symbols]

1,16 MSGC 2,11 Drift electrode (window) 3 Drift electric field (E electric field) 4 Gas atmosphere 5 Detector 6 Detected signal by detector 7 Electron cloud 8 Electron track 9 Incident gamma ray candidate cone A Obtained from multiple events γ-ray incident direction B Candidate of γ-ray incident direction obtained from one recoil electron 10 γ-ray arrival direction detector 12 Gas package 13 Field wire (electric field structure line stretched on side wall of gas package) 14 Capillary plate 15 Long Drift area 17 Photodetector 20 Data acquisition system 21 Encoder system 22 Memory module 23 Clock 24 Counter (time stamp) 25 Computer system 26 Trigger signal

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Claims (5)

[Claims] 1. A method of determining a gamma ray incident direction from a trajectory image of recoil electrons by MSGC, (a) identifying a physical elementary process that caused recoil electrons, and (b) incident gamma rays by a photoelectric effect. (C) Estimate the candidate of the incident direction of the incident γ-ray by the Compton effect, and (d) Determine the incident direction of the γ-ray by the recoil electron observation of a plurality of events. A method of determining a gamma ray incident direction from a trajectory image of recoil electrons by MSGC. 2. An apparatus for determining a gamma ray incident direction from a locus image of recoil electrons by MSGC, wherein (a) a drift electrode serving as a window, (b) a gas package, and (c) a long electrode having a plurality of field wires. A drift region, (d) a capillary plate, (e) MSGC, and (f) a data collection system, and (g) ionizing the gas in the detection region by recoil electrons in the gas package. The electrons drift along a drift electric field adjusted to be perpendicular to the detection surface, reach the capillary plate, which is an intermediate amplifier, are gas-amplified, and further drift the amplified electrons to the MSGC, and have a two-dimensional structure. A signal is generated at the electrode, and the position is recorded at every high-speed time by the data collection system. γ-ray incident direction determining device from the image. 3. An apparatus for determining a direction of incidence of γ-rays from a trajectory image of recoil electrons by MSGC, wherein (a) a drift electrode serving as a window, (b) a gas package, and (c) a long electrode having a plurality of field wires. A drift region; (d) a photodetector located beside the long drift region; and (e)
A capillary plate, (f) MSGC, and (g) a data collection system, (h) the recoil electrons in the gas package ionize the gas in the detection area, and γ-rays generate photoelectric / Compton in the gas. In order to determine the instantaneous time at which the effect occurred, the photodetector captures light generated by the ionized gas, and the electrons drift along a drift electric field adjusted to be perpendicular to the detection surface. The gas reaches the capillary plate, which is an amplifier, and is gas-amplified.
A device for determining a direction of incidence of γ-rays from a trajectory image of recoiled electrons by MSGC, wherein a signal is generated by a two-dimensional electrode, and the position is recorded at every high-speed time by the data acquisition system. 4. The apparatus according to claim 2, wherein the gas package is filled with a gas based on Xe, wherein the gas package is filled with a gas based on Xe. A gamma ray incident direction determination device from the image of the trajectory of the jumping electrons. 5. The apparatus for determining a direction of incidence of γ-rays from a locus image of recoil electrons by MSGC according to claim 4, wherein the gas package is capable of adjusting the pressure of Xe. Γ-ray incident direction determination device from trajectory images