WO2006083011A1

WO2006083011A1 - System for discriminating direction of high-energy ray source direction

Info

Publication number: WO2006083011A1
Application number: PCT/JP2006/302211
Authority: WO
Inventors: Toru Aoki; Yoshinori Hatanaka
Original assignee: National University Corporation Shizuoka University
Priority date: 2005-02-04
Filing date: 2006-02-02
Publication date: 2006-08-10

Abstract

A system for discriminating the direction of a high-energy ray source, wherein a collimator (2) is formed of double rings, and a space of Da is secured between the inner ring (2a) and the outer ring (2b) and also a space Db is secured between the inner ring (2a) and a sensor (1). A distribution function for signals can be adjusted by adjusting these spaces. When the collimation of the collimator is at such a degree that allows an incidence to sensors on both sides of unit sensors positioned apart 180° from each other, an insensible incidence angle by a space between the unit sensors can be eliminated. Also, when a plurality of ring-like two-dimensional sensors are stacked and formed to be extended in the closed state of the opening part (3) of the collimator formed in the outer periphery thereof, the flying direction of energy ray from a vertical direction to the flat surfaces of the rings can also be discriminated.

Description

High energy source direction discrimination system

Technical field

The present invention relates to a technique for identifying the direction of radiation of soot energy radiation and specifying the direction of the radiation source.

Light

Thread ^ _ I

Technical background

In the past, the ionization chamber was used to monitor radiation and the radiation was monitored. However, there were many problems in identifying the direction of flight, such as those in which the direction of flight was indistinguishable, or the discharge persisted or became indistinguishable for many flights.

Instead of the ionization chamber, a collimator has been placed in front of the sensor to identify the direction of flight from the direction of the collimator, but the collimator has to be directed toward the source, etc. It was difficult to use to specify the direction of the radiation source.

In addition, there is one that detects the incident direction of radiation by calculating the mutual positional relationship of the signal output of radiation incidence by superimposing two or more two-dimensional sensors (see Patent Document 1). However, this can be calculated because a single radiation outputs a signal at a position corresponding to a specific pixel in each layer. As the number of incident radiation increases, it becomes difficult to distinguish. When a lot of radiation comes from a certain direction within a certain time, the integral value of each pixel of each layer is averaged, and the direction cannot be determined.

[Patent Document 1] Japanese Patent Publication No. 6-1 0 5 3 0 3 Disclosure of the invention

Traditionally collimators are designed to allow radiation in only one direction as much as possible, and are designed to avoid incidence at tilt angles.

The present invention is based on a new idea of specifying the radiation direction of radiation using the shadow of a collimator with respect to incidence at an inclination angle.

According to the present invention, the shadow of the collimator is formed according to the radiation direction of radiation, and the direction of flight can be determined by calculating the distribution relation of the output signal based on the positional relationship of the shadow. Brief Description of Drawings

Fig. 1 is a side view of the arrangement of sensors and collimators.

FIG. 2 shows the sensor output for each radiation source.

FIG. 3 is a front view showing the arrangement of the two-dimensional sensor and the shadow of the collimator. FIG. 4 is a diagram showing a case where a plurality of radiation rays are incident. Fig. 4 (a) shows an example where radiation E 1 is incident from the front and radiation E 2 is incident slightly from the right. Fig 4

(b) shows an example where radiation E 1 is incident from the front and radiation E 3 is incident slightly from the left. Figure 4 (c) shows the case with three radiation sources.

Fig. 5 shows an example in which there is one source on the left and two sources on the right.

Fig. 6 shows the signal intensity when radiation is incident on the ring-shaped one-dimensional sensor.

FIG. 7 is a diagram showing a configuration example in which a collimator is attached to a ring-shaped one-dimensional sensor and signal intensity.

FIG. 8 is an enlarged view showing the positional relationship between the sensor and the collimator.

FIG. 9 is a diagram showing a configuration in which ring-shaped one-dimensional sensors are stacked. FIG. Lo is a diagram showing signal intensity in the laminated state. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, by making a one-dimensional sensor into a ring shape or a polygonal shape, an attempt is made to specify the direction of radiation radiation from the output distribution, and high-energy radiation penetrates the sensor on the incident side and is emitted. A signal output is also obtained from the sensor on the side, and the source direction can be specified as the direction connecting the straight line from one incident side to the output side, so high accuracy is obtained.

Since the one-dimensional sensor is formed in a ring shape, the circuit configuration of the one-dimensional sensor can be used as it is, and the production method can be used to reduce the production cost.

[Example 1]

An example in which two one-dimensional sensors A and B are spatially separated will be described. The collimator is placed so that the sensor is sandwiched by a distance D1, which is a half of the length M of the sensor sensitivity surface. The material of the collimator shall have a shielding function against high-energy rays (such as lead), and the collimator aperture shall be the same as the sensitivity surface of the sensor. Further, D 1 = D 2 is assumed.

As shown in Fig. 1, sensor A (l) and sensor B (2) are placed at a distance of D2. In addition, collimator S (3) is placed on the upper surface of sensor A (1) with a distance of D 1 and collimator T (4) is placed on the lower surface of sensor B (2) with a distance of D 1 . The photosensitive surface of the sensor and the aperture of the collimator have the same dimensions. The dimensions here are only examples, and can be arbitrarily set while paying attention to the receiving angle.

The top row in Fig. 2 shows the signal distribution of sensor A (l) and sensor B (2) when radiation enters from the direction E1 in Fig. 1, that is, from the vertical direction of the sensor. The second row in Fig. 2 shows the signal distribution when radiation enters from the direction of E 2 in Fig. 1. The third row in Fig. 2 shows E 3 in Fig. 1, and the lower row in Fig. 2 shows each sensor A (l) and sensor B when radiation enters from the direction of E 4 in Fig. 1. The signal distribution of (2) is shown.

When the radiation source is in the far direction of E 1 and incident with a vector of E 1, that is, when coming from the vertical (θ 1 = 0) direction, the outputs of sensors A and B are obtained from the entire sensor. It is done. In other words, there is no lack of signal. If the source is far away from E 2 and radiation comes from the E 2 vector, a collimator shadow will appear on sensors A and B. In this case, the direction of the radiation source can be obtained from the following simple relationship. However, the length of the sensitivity surface of sensor A is M, and the length of the missing signal is m.

If the incident angle of radiation to the sensor is Θ 1 from the vertical line

D 1 · Τ ηθ 1 = m… (:!)

Because

Tan Θ 1 = m / D 1 = 2 m / M (2)

At this time, if the sensor Β is separated from the sensor Α by a distance of D 2 and arranged almost in parallel, and the incident angle of radiation to the sensor is 0 2 from the vertical line, (D 1 + D 2) Tan02 η '· (3)

Because

Tan0 2 = n / (D l + D 2) = η / Ν (4)

However, the length of the sensitivity surface of 感度 sensor is Ν (2 Μ), and the length of the missing signal is η. Incidentally, also _c sensors and collimators thickness was negligible, but in this example has a radiation source arrives from the direction of the upper, If coming from the direction of the bottom, by comparing the m and n, small Judging from the side. Or, it is assumed that M-m and N-n come from the larger one. Even in the vertical case, the signal amount is judged because the signal amount of the sensor on the radiation direction side is large. Is easily obtained.

If both sensor A and sensor B can detect radiation,

D 2 · Tan03 = | n | — | m | '· (5)

However, when I η I> l m |, 45 ° ≤ Θ3≤45 °

n | <| m | 1 35 ° ≤ Θ3≤ 225 °

Can also be obtained. If the sensor 1 and the sensor 1 are not the same sensor but have different frequency and single sensitivity characteristics, it is possible to have a wide band.

Furthermore, if the third and fourth sensors and collimator are installed at different angles, the direction in the vertical direction can be determined regardless of the difference in the signal level.

[Example 2]

Figure 3 shows how the collimator shadows are produced when two two-dimensional sensors A and B are placed apart. Figure 3 shows the case where sensor A (l) and sensor B (2) are two-dimensional sensors. In this case, the one-dimensional case is expanded to two dimensions, and the idea is the same. The horizontal cross section is the same as in Fig. 1, so it is omitted. Fig. 3 (a) is a view from above of sensor A (l). There is a collimator S (3) in the foreground, and sensor A (l) is visible through the opening. Sensor B (2) is invisible behind sensor A (l). Similarly, the collimator T (4) cannot be seen behind the collimator S (3). Note that the area around the collimator S (3) is omitted. This is an example when radiation from outside is incident with directionality E5.

Fig. 3 (b) and Fig. 3 (c) show the signal detection area of sensor A (l) and sensor B (2), but the shaded area shows the area without signal due to the shadow of the collimator. . In sensor A (l), there are two areas where no radiation can be detected: an area without a signal (5) and an area with a signal that can detect radiation (6). Zensa Similarly, in B (2), an area where no radiation can be detected is distinguished as an area (7) where there is no signal and an area (8) where there is a signal where radiation can be detected.

In this case as well, as in the case of the above one-dimensional case, the angle in the arrival direction is obtained for each of the vertical and horizontal directions, so the angle on the two-dimensional plane is obtained.

By arranging multiple detectors that can detect the above one-dimensional or two-dimensional directions, the direction of the radiation source in all directions can be specified. The system can be tailored to the purpose by adjusting the length of the one-dimensional sensor as needed or by modifying the symmetry of the two-dimensional length.

As an example of deformation, it is conceivable that the sensor is arranged in a spherical shape to enable detection of radiation from all directions. This means that a two-dimensional sensor is used as the sensor and is arranged in a substantially spherical shape. A sphere is formed of a material having a radiation shielding effect as the outer shell of the sensor assembly. A hole as a collimator is drilled at a position corresponding to the center of each 2D sensor, and the shadow of the incoming radiation is projected onto each 2D sensor. Here, it is assumed that the two-dimensional sensors are discretely arranged, and a hole is made at a position corresponding to the approximate center of each two-dimensional sensor. However, when two-dimensional sensors are continuously arranged in a spherical shape, The hole shall be drilled at any place on the outer shell. Preferably, holes should be drilled at several points equally divided on the spherical surface. In addition, although the two-dimensional sensor is arranged in a substantially spherical shape, it should be considered to be a polyhedral solid from the viewpoint of manufacturing. For example, it would be easy to manufacture a regular 12-sided body with 12 two-dimensional sensors affixed to each surface and 12 holes in the outer shell. Also, it is up to the force to make the outer shell a sphere, whether to make a multi-dimensional solid.

, ¾ C'fc.

As another modification, it is conceivable that a unit formed by integrating a two-dimensional sensor and a collimator made of a material having a radiation shielding effect is arranged in a substantially spherical shape. Figure 4 shows the case of multiple incident radiation. Figure 4 (a) shows radiation E 1 from the front. In this example, radiation E 2 is incident from the right. Radiation E 2 is simplified and shown by a single arrow, but it is incident with a width similar to radiation E 1. Difference between the falling position of sensor A's output (A) and the falling position of sensor B's output (B) Force ^ The incident direction of radiation E 2 can be determined.

Figure 4 (b) shows an example in which the radiation E 1 is incident from the front and the radiation E 3 is incident slightly from the left. In this case, the incident direction of the radiation E 3 can be determined from the difference between the rising position of the output (A) of the sensor A and the rising position of the output (B) of the sensor B. In Fig. 4 (c), there are three radiation sources, but the same judgment can be made.

Figure 5 shows an example in which there is no front source, one source is on the left, and two sources are on the right. Even in this case, the incident direction of the radiation E 2 can be determined from the distance m 2 from the fall of the signal A to the right end due to the radiation E 2 and the distance n 2 from the fall of the signal B to the right end. Thereby, the azimuth | direction of a radiation source is calculated | required.

Similarly, the incident direction of radiation E 3 can be determined from the distance m 3 from the rising edge of signal A to the left edge and the distance n 3 from the rising edge of signal B to the left edge.

Further, the incident direction of the radiation E 4 can be determined from the distance m 4 and the distance n 4. In this case, the falling positions of the signals due to radiation E 2 and radiation E 4 do not change the order in each sensor, and distance n 2 is easy for distance m 2 and distance n 4 is easy for distance m 4. Can be associated.

In the explanation here, the increase and decrease of the sensor output is expressed as the rise and fall of the signal. This is an implication for time-series signal readout, and it should be understood that the horizontal axis in the figure indicates the position and the time axis.

[Example 3]

Fig. 6 (a) shows that radiation is incident from the direction of R on the one-dimensional sensor (1 1) in a ring shape. Figure 6 (b) shows the output signal intensity distribution from the sensor at that time. When the sensor (1 1) unit is arranged in a ring shape or polygonal shape, the effective area incident on the photosensitive surface varies depending on the incident angle. As shown in Fig. 6, when the angle is taken with the incident line R as the base point, the effective area is a function of Cose, and becomes a maximum at 0 degrees and 180 degrees. Therefore, the direction of incidence is the one with the highest peak signal intensity on the straight line connecting the maximum 0 ° and 1880 ° points.

In the vicinity of 0 degrees and 1800 degrees of C os 0, the change of the function with respect to the angle is small and the resolution cannot be taken high. Therefore, by placing a collimator in front of the sensor and saying the restriction on the tilted incidence on the sensor, it is possible to obtain a function with sharp peaks at the points of 0 ° and 180 °, and the resolution can be increased. At this time, the collimator is a collimation that allows a slight incident on the unit sensor on both sides of the unit sensor at 180 degrees. Fig. 7 (a) shows that the radiation is incident from the direction of R on the one-dimensional sensor (1 1) in the ring shape and the collimator (1 2) placed on the outer periphery. Figure 7 (b) shows the output signal intensity distribution from the sensor at that time. The signal intensity distribution at this time is sharp. The collimator is made of a heavy metal such as lead or tin and is made of a material with a high radiation blocking effect. Figure 8 shows an enlarged view.

FIG. 8 shows the structural details of the sensor (1 1) and the collimator (1 2). By adjusting the distance Da between the inner and outer collimators, the distance Db between the inner collimator and the sensor, the signal distribution function can be adjusted, and the dead angle due to the element spacing can be eliminated. Note that the opening (1 3) exists all around, but is partially omitted in FIG.

As shown in FIG. 8, the aperture of the collimator is the same as the photosensitive area of the unit sensor. The light may be received by a plurality of unit sensors. The collimator (1 2) consists of double rings, the inner ring (1 2 a) and the outer ring (1 2 b) are connected by a space Da, and the inner ring (1 2 a) and sensor ( 1 1) and space Db There is. By adjusting this interval, the strength of the collimation can be adjusted.

When the collimation is sufficient to allow the incident to the sensor adjacent to the unit sensor located at 1800 degrees, the insensitive incident angle due to the unit sensor interval can be eliminated. The unit sensor here refers to the smallest unit that generates a signal upon receiving radiation, that is, the detection element, and determines the resolution.

The collimator here is a double ring, but even with a single ring, the signal intensity distribution is sufficiently sharp, and this does not exclude the embodiment of the single ring. In addition, if the number of collimator openings (1 3) is an odd number, the front-rear sensitivity ratio becomes large, and the front and rear identification of the radiation source position becomes easy. The unit sensor is provided over the entire circumference of the ring, but it may be provided only at a location facing the opening (13).

[Example 4]

An embodiment will be described in which a ring-shaped one-dimensional sensor is stacked to change the sensitivity with respect to an angle in the vertical direction with respect to a virtual plane in which the sensors are arranged in a ring shape. As shown in Fig. 9, the ring-shaped one-dimensional sensor (l la, l lb, l lc, l ld) from above, the first sensor (l la), the second sensor (l lb), and the third sensor (11c) Stack the 4th sensor (l id). There may be a gap between these sensors, or they may be in close contact with each other. At this time, the detection range in the vertical direction can be set by changing the space Dc between the stacked rings and the space Dd above and below the collimator and sensor.

In FIG. 9, the inner collimator (1 2 a) and the outer collimator (1 2 b) are both cylindrical and extend in the vertical direction in FIG. When radiation R 1 comes from the right in Fig. 9, it is detected in all of the first to fourth of each ring sensor, and the intensity of the sensor located at 0 degree with respect to radiation R 1 is the strongest. It is. Next, the output of the sensor located at 180 degrees is the largest (the upper part of FIG. 10). Similarly, an example of the signal output of the sensor 1 when the radiation R 2 comes from the right or slightly below in FIG. 9 is shown in the middle of FIG. In this case, the sensor at the 0 degree position of the fourth sensor (lid) has no signal output because the radiation R 2 is blocked by the collimators (12a, 12b). In addition, radiation R 2 is blocked by the collimators (12a, 12b) of the third and fourth sensors (l lc, l ld) at the 180 ° position, and there is no signal output. In addition, the signal output when the radiation R 3 comes from the right direction in FIG. 9 appears slightly as shown in the lower part of FIG. In both figures, the radiation direction is 0 degrees, the deviation from the direction is Θ, and the position of each sensor on the ring is plotted on the horizontal axis.

According to this configuration, it is possible to measure the inclination angle of the radiation source with respect to a virtual plane where the ring-shaped (or polygonal) one-dimensional sensor is arranged.

In this embodiment, the collimator is also a double ring, but even with a single ring, the signal intensity distribution is sufficiently sharp, and this does not exclude the single ring embodiment. . Industrial applicability

According to the present invention, a large number of incoming radiation is measured as an integrated intensity distribution, and the amount of incident radiation and the incoming direction can be determined at appropriate time intervals, and the calculation method is also simple. Yes, and the circuit configuration can be greatly simplified.

In particular, monitoring of nuclear facilities and monitoring of nuclear waste will function extremely effectively in identifying the source direction.

Claims

The scope of the claims

1. A one-dimensional or two-dimensional sensor is placed in a space, and a hole made in a plate of lead or the like having a shielding function against radiation is provided at a certain distance from the sensor as a collimator in front of the sensor. The high energy radiation source is characterized by estimating the arrival direction of the radiation source by forming the shadow of the collimator hole at different positions on the sensor surface according to the radiation arrival direction. Direction discrimination system

2. The sensor consists of two or more one-dimensional sensors arranged in parallel and spatially separated from each other. From the signal output distribution from there, the direction of arrival of highly transmissive radiation sources such as radiation and X-rays can be determined. The high energy radiation source direction discriminating system according to claim 1, characterized in that it is estimated.

3. The sensor consists of two or more two-dimensional sensors that are spatially separated and arranged in parallel. From the signal output distribution from there, the arrival direction of a highly transmissive radiation source such as radiation and X-rays can be determined. 2. The high energy radiation source direction discriminating system according to claim 1, wherein the direction is determined.

4. A one-dimensional sensor or a two-dimensional sensor is arranged in a ring shape or a polygonal shape, and a collimator is arranged on the outer periphery of the sensor. Estimate the direction of the radiation source from the output signal distribution of the sensor with the collimation that can irradiate the unit sensor on both sides of the unit sensor located 180 ° opposite to the center of the ring or polygonal shape. High energy radiation source direction discrimination system.

5. A one-dimensional sensor or a two-dimensional sensor is arranged in a ring shape or a polygonal shape, a collimator is arranged on the outer periphery of the sensor, and a plurality of sensors arranged in the ring shape or the polygonal shape are stacked at an appropriate interval. And estimating the inclination angle of the radiation source with respect to the ring-shaped or polygonal arrangement plane from the output signal distribution of the sensor, and estimating the direction of the radiation source from the output signal distribution of the sensor. High energy source direction discrimination system.