CN110018513A - A kind of neutron spectrometer of polyhedral structure - Google Patents

Abstract

The invention belongs to radiometric technique fields, a kind of neutron spectrometer of polyhedral structure is disclosed, including detector (1) and the slow body (2) in the detector (1) outside is set, the slow body (2) includes multiple sub- slow bodies (21), multiple sub- slow bodies (21) are that endpoint dissipates setting outward with the detector (1), and multiple sub- slow bodies (21) have a variety of different thickness.The present invention provides a kind of neutron spectrometer of polyhedral structure, slowing down body thickness can be converted according to demand, and structure is simple, without considering the sealing problem of liquid.

Description

A neutron spectrometer with polyhedral structure

technical field

The invention relates to the technical field of radiation measurement, in particular to a neutron spectrometer with a polyhedron structure.

Background technique

With the popularization and rapid development of neutron technology in frontier basic research, nuclear energy, nuclear weapons, medicine, industry, agriculture and other fields, the measurement and protection of neutron radiation is getting more and more attention. The neutron radiation effect in the workplace is often described by the dose equivalent around the neutron, which is closely related to the neutron fluence and energy; especially the energy, the neutrons with the same fluence and different energies have different contributions to the dose, which makes the neutron fluence and energy different. Spectroscopic measurement plays an important role in radiation protection dose measurement. The so-called "neutron spectrum" refers to the fluence of neutrons of different energies Statistical spectrum with the distribution of neutron energy E, also called "neutron fluence-energy distribution spectrum". Usually the neutron energy range of concern is 10 ^-9 ~ 20MeV, according to its energy size, it is divided into: fast neutron (>100keV), slow neutron (ie neutron neutron, 0.5eV ~ 100keV), thermal neutron (about 100keV) 0.025eV) and cold neutrons (<0.005eV).

³ He, ⁶ LiF, BF ₃ , etc., which have a large reaction cross section with thermal neutrons, can be used to make thermal neutron detectors for neutron spectroscopy measurement, and they have high detection efficiency for thermal neutrons. However, as the neutron energy increases, the reaction cross section decreases, and its detection efficiency drops sharply. The moderator is made of a material containing more light nuclei, and the moderator coats the surface of the thermal neutron detector, which can moderate high-energy neutrons into thermal neutrons, thereby improving the detection efficiency of high-energy neutrons. The main method for measuring neutron energy spectrum by using a moderator to coat a thermal neutron detector is a multi-sphere spectrometer method, which consists of a thermal neutron detector and a variety of spherical moderators with different thicknesses. The structure of conventional multi-sphere neutron spectrometer, such as patent application CN201710201494.3, describes a water pumping and filling multilayer concentric sphere device and a neutron energy spectrum detection system. The water pumping and injection multilayer concentric sphere device includes a neutron detector, multiple The shell and the water pumping device are set in sequence from the inside to the outside, the innermost shell in the shell is set on the surface of the neutron detector, and between any two adjacent shells is formed a liquid accommodating device. Gap, the shell is made of aluminum material, each shell outside the innermost shell is provided with a valve, and the water pumping device connects the valves of each shell outside the innermost shell in turn to facilitate the flow of water into the gap. Fill or drain the water in the gap. Since this kind of multi-sphere neutron spectrometer needs to inject or drain water into the multi-layer shell in sequence, the requirements for the liquid tightness of the device are too high, and the way of changing the moderator is complicated.

Based on the above situation, it is necessary to design a neutron spectrometer detection device that can solve the above problems.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a neutron spectrometer with a polyhedral structure, which can change the thickness of the moderator according to requirements, and has a simple structure without considering the problem of liquid sealing.

For this purpose, the present invention adopts the following technical solutions:

A neutron spectrometer with a polyhedron structure, comprising a detector and a moderator arranged outside the detector, the moderator includes a plurality of sub-moderators, and the plurality of sub-moderators are connected with the detection The end points of the moderators are arranged to diverge outward, and a plurality of the sub-moderators have various thicknesses.

Specifically, the sub-moderator is connected to the detector. The thickness of the sub-moderator refers to the distance from the outer end surface of the sub-moderator to the center of the detector, and the outer end of the sub-moderator is the distance from the sub-moderator to the center of the detector. The end face of one end of the neutron beam enters the sub-moderator from the outer end face of the sub-moderator.

A plurality of the sub-moderators have various thicknesses, and the thickness of each sub-moderator is different from the thickness of the other sub-moderators, that is, the number of thickness types of the sub-moderators The number of the sub-moderators is the same as the number of the sub-moderators, for example, the N sub-moderators have N thicknesses; or,

At least two of the sub-moderators have the same thickness and the sub-moderators with the same thickness have different thicknesses from other sub-moderators, that is, the number of thickness types of the sub-moderators is more than one. The number of kinds but less than the number of the sub-moderators, such as N of the sub-moderators, with M kinds of thickness, 1<M<N.

Preferably, the plurality of sub-moderators have various thicknesses, and the thickness of each sub-moderator is different from the thickness of the other sub-moderators.

As a preferred technical solution, the neutron spectrometer further includes a driving device, and the driving device drives the moderator to rotate, so that the sub-moderators with different thicknesses face the incident direction of the neutron beam.

Specifically, when the moderator rotates, the position of the detector remains unchanged, that is, the position of the detector relative to the neutron beam source remains unchanged.

As a preferred technical solution, the moderator is a multi-faceted cylindrical structure, the detector is arranged on the rotation axis of the moderator, and the outer end surface of the sub-moderator is connected to the moderator. The axes of rotation are parallel.

Specifically, the high-voltage line and the signal lead-out line of the detector pass through the upper end face or the lower end face of the moderator.

Preferably, the distances from the outer end surfaces of the plurality of sub-moderators to the rotational axis of the moderators are different, that is, the thicknesses of the plurality of sub-moderators are different.

Preferably, the included angle between any two adjacent sub-moderators is the same, that is, a plurality of the sub-moderators are arranged outside the detector at equal angles.

As a preferred technical solution, the outer end surface of the sub-moderator is a cylindrical surface.

Specifically, the central axis of the cylinder where the cylindrical surface is located is the rotation axis of the moderator.

As a preferred technical solution, the driving device is a stepping motor, and the output shaft of the stepping motor is located on the rotation axis of the moderator and is fixedly connected to the moderator.

Specifically, when the stepping motor rotates by a preset angle, the moderator rotates once, so that the sub-moderator with another thickness faces the incident direction of the neutron beam, so as to change the sub-moderator with different thicknesses toward the middle. The beamlet incident direction.

As a preferred technical solution, the moderator includes a plurality of spheres with the center of the detector as the center of the sphere, each of the sub-moderators includes one of the spheres, and a plurality of the spheres The bodies are similar in shape, with equal solid angles and unequal radii.

Specifically, the radius of the spherical body is the distance from the spherical surface of the spherical body, that is, the outer end surface, to the center of the detector. The radii of the plurality of the spherical bodies are different, that is, the thicknesses of the plurality of the sub-moderators are different.

As a preferred technical solution, the moderator further includes a polyhedron frame, the detector is located in the center of the polyhedron frame, the surface of the polyhedron frame is a polygon, and each polygon is connected to the detector. A cavity is arranged between them, and each of the spherical bodies is arranged in one of the cavities.

Preferably, the polyhedron frame includes spacers disposed between the cavities, and the spheres are separated from each other by the spacers.

As a preferred technical solution, the polyhedron frame is a regular dodecahedron frame, and the surface of the regular dodecahedron frame is twelve regular pentagons.

Preferably, one of the regular pentagons of the regular dodecahedron frame is the lead-out surface, the cavity corresponding to the lead-out surface is not provided with a sub-moderator, and the high-voltage line and the signal lead-out line of the detector are connected from The lead-out surface passes through, and the driving device is fixedly connected with the regular dodecahedron frame at the lead-out surface. The surface opposite to the lead-out surface on the regular dodecahedron frame is an idle surface, and no sub-moderator is arranged in the idle surface.

As a preferred technical solution, the driving device includes a first support rod, a second support rod, an arc-shaped rack, a first motor, a second motor, a first gear, a second gear, a third gear, and a fixed rail. a groove and a rail-fixing rod, the upper end of the first support rod is fixedly connected with the moderator, the lower end of the first support rod is rotatably connected with the second support rod, the first support rod, the second support rod The two support rods and the detector are located on the same axis, the lower end of the second support rod is fixedly connected to the rail-fixing rod, the lower end of the rail-fixing rod is rotatably connected to the first gear, and the first gear is connected to The arc-shaped racks are meshed with each other, the arc-shaped racks are arranged on the circumference with the center of the detector as the center of the circle, the track-fixing rods are slidably arranged in the track-fixing grooves, and the track-fixing grooves are arranged On another circle with the center of the detector as the center, the first motor drives the first gear to rotate, the second motor is fixed on the second support rod, and the second motor is The second gear is installed on the rotating shaft, the third gear is fixedly arranged on the first support rod, and the second gear meshes with the third gear.

The beneficial effects of the invention are as follows: a neutron spectrometer with a polyhedral structure is provided, which can change the thickness of the moderator according to requirements, and has a simple structure and does not need to consider the problem of liquid sealing.

Description of drawings

1 is a schematic structural diagram of a moderator according to Embodiment 1 of the present invention;

FIG. 2 is a schematic structural diagram of a cross-section of a moderator according to Embodiment 1 of the present invention;

3 is a schematic structural diagram of a longitudinal section of a moderator according to Embodiment 1 of the present invention;

4 is a schematic diagram of the thickness and included angle of the sub-moderator in Embodiment 1 of the present invention;

5 is a schematic diagram of the connection between the moderator and the driving device in the first embodiment of the present invention;

6 is a schematic structural diagram of Embodiment 2 of the present invention;

7 is a schematic structural diagram of a sub-moderator in Embodiment 2 of the present invention;

FIG. 8 is a schematic structural diagram of the sub-moderator in the second embodiment of the present invention from another viewing angle;

9 is a schematic structural diagram of a polyhedron frame in Embodiment 2 of the present invention;

10 is a schematic diagram of the use state of Embodiment 2 of the present invention;

FIG. 11 is a schematic diagram of another use state of the second embodiment of the present invention.

Among them, the detector 1, the moderator 2, the sub-moderator 21, the polyhedron frame 22, the polygon 221, the cavity 222, the driving device 3, the first support rod 31, the second support rod 32, the arc-shaped rack 33, The rail fixing rod 34 , the second motor 35 , the first gear 36 , the second gear 37 , the third gear 38 , and the rail fixing groove 39 .

Detailed ways

In order to have a further understanding and understanding of the structural features of the present invention and the effects achieved, the preferred embodiments and accompanying drawings are used in conjunction with detailed descriptions, and the descriptions are as follows:

Example 1

A neutron spectrometer with a polyhedral structure, as shown in Figures 1 to 3, includes a detector 1 and a moderator 2 arranged outside the detector 1. As an improvement of the present invention, the moderator 2 includes a plurality of sub-moderators. The moderator 21 , a plurality of sub-moderators 21 are arranged divergently outward with the detector 1 as an end point, and the plurality of sub-moderators 21 have various thicknesses.

In this embodiment, as shown in FIG. 5 , the neutron spectrometer further includes a driving device 3 , and the driving device 3 drives the moderator 2 to rotate, so that the sub-moderators 21 with different thicknesses face the incident direction of the neutron beam.

In this embodiment, as shown in FIGS. 1 to 3 , the moderator 2 is a multi-faceted cylindrical structure. As shown in FIG. 5 , the detector 1 is arranged on the rotation axis of the moderator 2 , and the sub-moderator 21 is The outer end face of the moderator is parallel to the axis of rotation of the moderator 2 .

In this embodiment, as shown in FIG. 2 , the outer end surface of the sub-moderator 21 is a cylindrical surface.

In this embodiment, the driving device 3 is a stepping motor. As shown in FIG. 5 , the output shaft of the stepping motor is located on the rotation axis of the moderator 2 and is fixedly connected to the moderator 2 .

In this embodiment, the moderator 2 includes six sub-moderators 21 with different thicknesses, as shown in FIG. 1 to FIG. 4 , for the convenience of description, the six sub-moderators 21 are sequentially numbered as S1, S2, and S3. , S4, S5, S6, the thicknesses of S1 to S6 increase sequentially, as shown in Figure 4, the thicknesses of the sub-moderators S1, S2, S3, S4, S5, S6 are L1, L2, L3, L4, L5 respectively , L6, L1<L2<L3<L4<L5<L6. In this embodiment, the thickness of each sub-moderator is different from the thickness of the other sub-moderators, and the six sub-moderators have six thicknesses.

In other embodiments, the plurality of sub-moderators have various thicknesses, but two or more of the sub-moderators are allowed to have the same thickness, such as six sub-moderators with five or four sub-moderators. , three or two different thicknesses.

In this embodiment, a plurality of sub-moderators 21 are evenly distributed outside the detector 1, and the angle between any two adjacent sub-moderators 21 is the same. As shown in FIG. 4 , six sub-moderators 21 They are evenly distributed outside the detector 1, and the included angle between two adjacent sub-moderators 21 is both 60°.

In this embodiment, the lower end of the moderator 2 is fixedly provided with a connecting mechanism (not shown) that can be fixedly connected with the output shaft of the stepping motor, and the stepping motor is used to connect and drive the object to be rotated (in this embodiment) The rotation of the object to be rotated is a moderator), which is a conventional technical means in the art, and will not be repeated here. When the stepping motor drives the moderator 2 to rotate, the position of the detector 1 remains unchanged, and the preset rotation angle of the stepping motor is 60° each time. When the neutron spectrometer is in the initial state, make S1 face the neutron beam to be measured. At this time, the thickness of the moderator outside detector 1 is the thickness of S1. After one measurement is completed, the stepping motor rotates 60° to make the moderator body thick. 2 Rotate 60° counterclockwise, S2 is facing the neutron beam to be measured, at this time the thickness of the moderator outside detector 1 is the thickness of S2, that is, the transformation of the thickness of the moderator outside detector 1 is completed, and the step is rotated again motor until the neutron measurement is completed.

In other embodiments, the angle between any two adjacent sub-moderators is not the same, the driving device selects a stepping motor or other motors, and each rotation angle of the motor is based on the difference between the two adjacent sub-moderators. The actual included angle is set to ensure that when the driving device drives the moderator to rotate once, just make another adjacent sub-moderator face the neutron beam.

In other embodiments, the moderator 2 can be provided with n sub-moderators 21 with different thicknesses according to requirements, and n is 4, 5, 7, 8, 9, 10, 11, 12 one or more.

Embodiment 2

A neutron spectrometer with a polyhedral structure, as shown in FIGS. 6 to 11 , includes a detector 1 and a moderator 2 arranged outside the detector 1. As an improvement of the present invention, the moderator 2 includes a plurality of sub-moderators. The moderator 21 , a plurality of sub-moderators 21 are arranged divergently outward with the detector 1 as an end point, and the plurality of sub-moderators 21 have various thicknesses.

In this embodiment, as shown in FIG. 6 , the neutron spectrometer further includes a driving device 3 , and the driving device 3 drives the moderator 2 to rotate, so that the sub-moderators 21 with different thicknesses face the incident direction of the neutron beam.

In this embodiment, as shown in FIGS. 6 to 11 , the moderator 2 includes a plurality of spheres with the center of the detector 1 as the center of the sphere, and each sub-moderator 21 includes a sphere, as shown in FIG. 7 . As shown in FIG. 8 , a plurality of spherical bodies have similar shapes, equal solid angles and unequal radii.

In this embodiment, as shown in FIG. 6 , the moderator 2 further includes a polyhedron frame 22 , and the detector 1 is located at the center of the polyhedron frame 22 . As shown in FIG. 9 , the surface of the polyhedron frame 22 is a polygon 221 , and each polygon A cavity 222 is arranged between 221 and the detector 1 , and each spherical body is arranged in one cavity 222 .

In this embodiment, as shown in FIG. 9 , the polyhedron frame 22 is a regular dodecahedron frame, and the surface of the regular dodecahedron frame is twelve regular pentagons.

In this embodiment, as shown in FIG. 6 , the driving device 3 includes a first support rod 31 , a second support rod 32 , an arc-shaped rack 33 , a first motor (not shown), a second motor 35 , a first The gear 36 , the second gear 37 , the third gear 38 , the fixed rail groove 39 and the rail fixed rod 34 , the upper end of the first support rod 31 is fixedly connected with the moderator 2 , and the lower end of the first support rod 31 is connected with the second support rod 32 Rotationally connected, the first support rod 31, the second support rod 32 and the detector 1 are located on the same axis, the lower end of the second support rod 32 is fixedly connected with the rail-fixing rod 34, and the lower end of the rail-fixing rod 34 is rotatably connected with the first gear 36, The first gear 36 meshes with the arc-shaped rack 33. The arc-shaped rack 33 is arranged on the circumference with the center of the detector 1 as the center of the circle. On another circle with the center of the detector 1 as the center, the first motor (not shown) drives the first gear 36 to rotate, the second motor 35 is fixedly arranged on the second support rod 32, and the second motor 35 is installed on the rotating shaft The second gear 37 and the third gear 38 are fixedly arranged on the first support rod 31 , and the second gear 37 meshes with the third gear 38 .

In this embodiment, the moderator 2 includes 10 sub-moderators 21 with different thicknesses, that is, including 10 spheres, and the regular dodecahedron frame has 10 cavities 222 , except for the lowermost end face and the uppermost end face. No cavity is provided, and each of the remaining cavities 222 is provided with a spherical body. The uppermost end face of the regular dodecahedron frame is the idle surface, and the lowermost end face is the lead-out surface. The lead-out surface is provided with a lead-out hole (not shown in the figure). The high-voltage lines and signal lines are led out from the lead-out holes. The upper end of the first support rod 31 is fixedly connected to the lead-out surface of the moderator 2 .

As shown in FIG. 6 , the arc-shaped rack 33 and the rail-fixing groove 39 are fixedly installed, and the first motor (not shown) can drive the first gear 36 to rotate and move along the arc-shaped rack 33 , thereby making the first support rod 31 , the second support rod 32 and the moderator 2 rotate with the detector 1 as the center of the circle. The second motor 35 can drive the first support rod 31 to rotate, so that the moderator 2 rotates with the first support rod 31 as the rotation axis. When the first gear 36 moves along the arc-shaped rack 33, the track-fixing rod 34 moves synchronously along the arc-shaped trajectory in the track-fixing groove 39. The so-called track-fixing means a fixed moving track, and its function is to enable the entire neutron spectrometer to Swing left and right with the geometric center of detector 1 as the center (swing to the left is negative, swinging to the right is positive), and the geometric center of detector 1 is always kept in the same horizontal position.

When the incident direction of the neutron beam is fixed, or when the neutron spectrometer in this embodiment is in a fixed neutron field, the mode of transforming the moderators with different thicknesses (from thin to thick) is as follows:

(1) Install the neutron spectrometer of the present embodiment, as shown in FIG. 6 , the initial state after the neutron spectrometer of the present embodiment is installed, when the neutron spectrometer is in the initial state, the regular pentagon boundary of the extraction surface One side is parallel to the neutron beam shown in FIG. 6 , and the first support rod 31 is in a vertical position. At this time, the lead-out surface faces directly downward, and the idle surface faces directly upward. The interior angle of the regular pentagon is 108°, and the dihedral angle of the regular dodecahedron frame is about 116.57°, so the moderator 2 is controlled to rotate clockwise around the first support rod 31 by 18° (18° in the initial state, clockwise The hour hand is the rotation direction of the moderator in the top view, the same below), the first support rod 31 and the second support rod 32 swing to the left by 26.57° (the first support rod 31 is at -26.57° of its initial state at this time), That is, the lower left side surface SA in the initial state shown in FIG. 6 can be rotated to a position perpendicular to the incident direction of the neutron beam, that is, the state shown in FIG. 10 . In this state, the sphere with neutrons incident perpendicularly is used as the first moderator, and the first neutron measurement can be carried out;

(2) Referring to FIG. 10 , when the first support rod 31 and the second support rod 32 are at -26.57° of their initial state (when the first support rod 31 and the second support rod 32 swing to the left by 26.57° in the initial state ), rotate the moderator 2 to 90°, 162°, -126°, -54° of the initial state of rotation in turn (the rotation angle of the moderator 2 around the first support rod 31, clockwise is positive, counterclockwise is negative ), corresponding to the second, third, fourth, and fifth moderators, respectively;

(3) Referring to FIG. 11 , when the first support rod 31 and the second support rod 32 are at 26.57° of their initial state (when the first support rod 31 and the second support rod 32 swing to the right by 26.57° in the initial state) , rotate the detector 1 to 54°, 126°, -162°, -90°, -18° in the initial state of rotation (the rotation angle of the moderator 2 around the first support rod 31, clockwise is positive and counterclockwise is negative), corresponding to the sixth, seventh, eighth, ninth and tenth moderators respectively;

(4) After ten neutron measurements corresponding to ten moderators are completed, the initial state of the neutron spectrometer can be restored.

The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art, and are not repeated here.

Finally, it should be noted that: in the description of the present invention, the technical terms "center", "upper", "lower", "left", "right", "front", "rear", "inner" and "outer" , "vertical", "horizontal", etc. indicate that the direction or positional relationship is based on the direction or positional relationship shown in the accompanying drawings, and is only for the convenience of description and understanding of the technical solutions of the present invention, rather than indicating or implying the indicated device or Elements must have a particular orientation, be constructed and operate in a particular orientation and are therefore not to be construed as limitations of the invention. Furthermore, the terms "first", "second", and "third" are used for descriptive purposes only and should not be construed to indicate or imply relative importance. In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations. The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that it can still The technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. A neutron spectrometer with a polyhedral structure, comprising a detector (1) and a moderator (2) arranged outside the detector (1), wherein the moderator (2) comprises A plurality of sub-moderators (21), a plurality of the sub-moderators (21) are arranged divergently outward with the detector (1) as an end point, and the plurality of the sub-moderators (21) have various different thickness of. 2 . The neutron spectrometer with a polyhedral structure according to claim 1 , wherein the neutron spectrometer further comprises a driving device ( 3 ), and the driving device ( 3 ) drives the moderator. 3 . (2) Rotate so that the sub-moderators (21) with different thicknesses face the incident direction of the neutron beam. 3 . The neutron spectrometer with a polyhedral structure according to claim 2 , wherein the moderator ( 2 ) is a polyhedral cylindrical structure, and the detector ( 1 ) is arranged in the moderator. 4 . On the rotation axis of the body (2), the outer end surface of the sub-moderation body (21) is parallel to the rotation axis of the moderator (2). 4 . The neutron spectrometer with a polyhedral structure according to claim 3 , wherein the outer end surface of the sub-moderator ( 21 ) is a cylindrical surface. 5 . 5. The neutron spectrometer with a polyhedral structure according to claim 3, wherein the driving device (3) is a stepping motor, and the output shaft of the stepping motor is located in the moderator (3). 2) and fixedly connected with the moderator (2). 6 . The neutron spectrometer with a polyhedral structure according to claim 2 , wherein the moderator ( 2 ) comprises a plurality of spherical bodies with the center of the detector ( 1 ) as the center of the sphere. 7 . , each of the sub-moderators (21) includes one of the spherical bodies, and a plurality of the spherical bodies have similar shapes, equal solid angles and unequal radii. 7. The neutron spectrometer with a polyhedron structure according to claim 6, wherein the moderator (2) further comprises a polyhedron frame (22), and the detector (1) is located in the polyhedron The center of the frame (22), the surface of the polyhedron frame (22) is a polygon (221), and a cavity (222) is provided between each of the polygons (221) and the detector (1). The spherical body is arranged in one of the cavities (222). The neutron spectrometer with a polyhedron structure according to claim 7, wherein the polyhedron frame (22) is a regular dodecahedron frame, and the surface of the regular dodecahedron frame is twelve Regular pentagon. 9 . The neutron spectrometer with a polyhedral structure according to claim 6 , wherein the driving device ( 3 ) comprises a first support rod ( 31 ), a second support rod ( 32 ), an arc-shaped tooth bar (33), first motor, second motor (35), first gear (36), second gear (37), third gear (38), track-fixing groove (39) and track-fixing rod (34) , the upper end of the first support rod (31) is fixedly connected to the moderator (2), the lower end of the first support rod (31) is rotatably connected to the second support rod (32), and the first support rod (31) is rotatably connected to the second support rod (32). A support rod (31), the second support rod (32) and the detector (1) are located on the same axis, and the lower end of the second support rod (32) is fixedly connected to the rail-fixing rod (34). , the lower end of the rail-fixing rod (34) is rotatably connected with the first gear (36), the first gear (36) is meshed with the arc-shaped rack (33), and the arc-shaped rack ( 33) It is arranged on the circumference with the center of the detector (1) as the center of the circle, and the track fixing rod (34) is slidably arranged in the track fixing groove (39), and the track fixing slot (39) is arranged in the On another circumference with the center of the detector (1) as the center, the first motor drives the first gear (36) to rotate, and the second motor (35) is fixedly arranged on the second support rod (32), the second gear (37) is installed on the rotating shaft of the second motor (35), the third gear (38) is fixedly arranged on the first support rod (31), and the The second gear (37) meshes with the third gear (38).