CN210051901U - Neutron spectrometer with polyhedral structure - Google Patents

Abstract

The utility model belongs to the technical field of the radiometric measurement, a polyhedral structure's neutron spectrometer is disclosed, be in including detector (1) and setting detector (1) outer slowing down body (2), slowing down body (2) including a plurality of son slowing down body (21), a plurality of son slowing down body (21) with detector (1) outwards disperses the setting, a plurality of for the extreme point son slows down body (21) and has the thickness of multiple difference. The utility model provides a polyhedral structure's neutron spectrometer can alternate according to the demand and slow down body thickness, and simple structure, need not to consider the sealed problem of liquid.

Description

Neutron spectrometer with polyhedral structure

Technical Field

The utility model relates to a radiometric measurement technical field especially relates to a polyhedral structure's neutron spectrometer.

Background

With the popularization and rapid development of neutron technology in the fields of advanced basic research, nuclear energy, nuclear weapons, medicine, industry, agriculture and the like,neutron radiation measurement and protection are increasingly receiving attention. The neutron radiation effect of a working site is usually described by neutron ambient dose equivalent, which is closely related to the fluence and energy of neutrons; especially, the energy, neutrons with the same fluence and different energies have different contributions to the dose, so that neutron energy spectrum measurement plays an important role in radiation protection dose measurement and calculation. By "neutron spectrum", it is meant the fluence of neutrons of different energies

The statistical spectrogram, also called "neutron fluence-energy distribution spectrum", is calculated along with the distribution of neutron energy E. The neutron energy range of general interest is 10 ^-920MeV, divided by its energy size: fast neutrons (> 100keV), slow neutrons (i.e., intermediate energy neutrons, 0.5eV to 100keV), thermal neutrons (approximately 0.025eV), and cold neutrons (< 0.005 eV).

Can use a material having a large reaction cross section with thermal neutrons ³He、 ⁶LiF、BF ₃The method is used for manufacturing thermal neutron detectors for neutron spectrum measurement, and the thermal neutron detectors have high detection efficiency on thermal neutrons. However, as the neutron energy increases, the reaction cross section decreases, and the detection efficiency thereof decreases sharply. The moderating body is made of a material containing more light nuclei, and is coated on the surface of the thermal neutron detector, so that high-energy neutrons can be moderated into thermal neutrons, and the detection efficiency of the high-energy neutrons is improved. The main method for performing neutron energy spectrum measurement by using the moderating body to cover the thermal neutron detector is a multi-sphere spectrometer method, which consists of the thermal neutron detector and a plurality of spherical moderating bodies with different thicknesses. Conventional multisphere neutron spectrometer structure is like patent application CN201710201494.3, record a take out and annotate water multilayer concentric sphere device and neutron energy spectrum detection system, this take out and annotate water multilayer concentric sphere device includes neutron detector, a plurality of casings and take out and annotate water installation that establish from inside to outside cover in proper order, the casing cover of inlayer is established on neutron detector's surface in the casing, be formed with the clearance that is used for holding liquid between arbitrary two adjacent casings, the casing adopts aluminium material to make and forms, every casing outside the casing of inlayer all is provided with the valve, take out and annotate water installation and connect gradually the casing of inlayerA valve is provided in each housing outside the body to facilitate filling or draining of the gap. The multi-sphere neutron spectrometer needs to be sequentially injected or drained into a multi-layer shell, the requirement on the liquid tightness of the device is high, and the mode of changing a slowing body is complex.

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

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a: the utility model provides a polyhedral structure's neutron spectrometer, can alternate according to the demand and slow down body thickness, and simple structure need not to consider the sealed problem of liquid.

To achieve the purpose, the utility model adopts the following technical proposal:

the utility model provides a polyhedral structure's neutron spectrometer, includes the detector and sets up the outer slowing down body of detector, the slowing down body includes a plurality of sub slowing down bodies, and is a plurality of sub slowing down body with the detector outwards diverges the setting for the extreme point, and is a plurality of sub slowing down body has the thickness of multiple difference.

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

The plurality of sub-moderators have a plurality of different thicknesses, and the thickness of each sub-moderator is different from the thicknesses of the other sub-moderators, that is, the number of the sub-moderator thickness types is the same as the number of the sub-moderators, for example, N sub-moderators have N thicknesses; alternatively, the first and second electrodes may be,

at least two of the sub-moderators have the same thickness, and the sub-moderators having the same thickness are different from the other sub-moderators in thickness, that is, the number of the thickness types of the sub-moderators is more than one but less than the number of the sub-moderators, for example, N sub-moderators have M thicknesses, 1< M < N.

Preferably, a plurality of the sub-moderators have a plurality of different thicknesses, and each of the sub-moderators has a thickness different from that of the other sub-moderators.

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

Specifically, when the slowing-down body rotates, the position of the detector is kept unchanged, namely the position of the detector relative to a neutron beam source is kept unchanged.

As a preferable mode, the moderator has a polygonal cylindrical structure, the detector is disposed on the rotational axis of the moderator, and the outer end surface of the sub moderator is parallel to the rotational axis of the moderator.

Specifically, the high-voltage wire and the signal outgoing wire of the detector penetrate out of the upper end face or the lower end face of the slowing-down body.

Preferably, the outer end surfaces of the plurality of sub-moderators are different in distance from the axis of rotation of the moderator, that is, the thickness of the plurality of sub-moderators is different.

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

As a preferable mode, 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 preferable technical solution, the driving device is a stepping motor, and an output shaft of the stepping motor is located on a rotation axis of the slowing-down body and is fixedly connected to the slowing-down body.

Specifically, when the stepping motor rotates by a preset angle, the moderating body rotates once to make the sub-moderating bodies with the other thickness face the incident direction of the neutron beam, so as to change the sub-moderating bodies with different thicknesses to face the incident direction of the neutron beam.

In a preferred embodiment, the moderator includes a plurality of spherical bodies centered on the center of the probe, each of the sub-moderators includes one of the spherical bodies, and the plurality of spherical bodies are similar in shape, equal in solid angle, and unequal in radius.

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

As a preferable technical solution, the moderator further includes a polyhedral frame, the detector is located at the center of the polyhedral frame, the surface of the polyhedral frame is a polygon, a cavity is provided between each polygon and the detector, and each spherical body is disposed in one of the cavities.

Preferably, the polyhedral frame comprises spacers arranged between the cavities, the spherical surfaces being separated from each other by the spacers.

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

Preferably, one of the regular pentagon surfaces of the regular dodecahedron frame is a leading-out surface, a sub-moderator is not arranged in a cavity corresponding to the leading-out surface, a high-voltage wire and a signal leading-out wire of the detector penetrate out of the leading-out surface, and the driving device is fixedly connected with the regular dodecahedron frame at the leading-out surface. The surface of the regular dodecahedron frame, which is opposite to the leading-out surface, is an idle surface, and a sub-slowing body is not arranged in the idle surface.

As a preferred technical solution, the driving device includes a first supporting rod, a second supporting rod, an arc-shaped rack, a first motor, a second motor, a first gear, a second gear, a third gear, a fixed rail groove and a fixed rail rod, the upper end of the first supporting rod is fixedly connected to the moderating body, the lower end of the first supporting rod is rotatably connected to the second supporting rod, the first supporting rod, the second supporting rod and the detector are located on the same axis, the lower end of the second supporting rod is fixedly connected to the fixed rail rod, the lower end of the fixed rail rod is rotatably connected to the first gear, the first gear is engaged with the arc-shaped rack, the arc-shaped rack is disposed on a circumference with the center of the detector as a center, the fixed rail rod is slidably disposed in the fixed rail groove, the fixed rail groove is disposed on another circumference with the center of the detector as a center, the first motor drives the first gear to rotate, the second motor is fixedly arranged on the second supporting rod, the second gear is installed on a rotating shaft of the second motor, the third gear is fixedly arranged on the first supporting rod, and the second gear is meshed with the third gear.

The utility model has the advantages that: the utility model provides a polyhedral structure's neutron spectrometer, can alternate according to the demand and slow down body thickness, and simple structure need not to consider the sealed problem of liquid.

Drawings

FIG. 1 is a schematic diagram of a moderator according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a moderator according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a longitudinal section of a moderator according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of the thickness and the included angle of the sub-moderator according to the first embodiment of the present invention;

FIG. 5 is a schematic view of the connection between the moderator and the drive apparatus according to the first embodiment of the present invention;

fig. 6 is a schematic structural diagram of a second embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a sub-moderator according to a second embodiment of the present invention;

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

fig. 9 is a schematic structural diagram of a polyhedral frame in a second embodiment of the present invention;

fig. 10 is a schematic view of a second embodiment of the present invention in use;

fig. 11 is another schematic view of an application state of the second embodiment of the present invention.

The detector 1, the moderator 2, the sub moderator 21, the polyhedral frame 22, the polygon 221, the cavity 222, the driving device 3, the first support rod 31, the second support rod 32, the arc rack 33, the orbit determination rod 34, the second motor 35, the first gear 36, the second gear 37, the third gear 38 and the orbit determination groove 39.

Detailed Description

In order to further understand and appreciate the structural features and advantages of the present invention, preferred embodiments and the accompanying drawings are described in detail as follows:

example one

The utility model provides a neutron spectrometer of polyhedral structure, as shown in fig. 1 to 3, including detector 1 and the slowing down body 2 of setting outside detector 1, as the utility model discloses an improvement, slowing down body 2 includes a plurality of sub slowing down bodies 21, and a plurality of sub slowing down bodies 21 use detector 1 to outwards disperse the setting as the extreme point, and a plurality of sub slowing down bodies 21 have the thickness of multiple difference.

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

In the present embodiment, as shown in fig. 1 to 3, the moderator 2 is a polygonal columnar structure, and as shown in fig. 5, the probe 1 is disposed on the rotational axis of the moderator 2, and the outer end face of the sub-moderator 21 is parallel to the rotational axis of the moderator 2.

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

In the present embodiment, the driving device 3 is a stepping motor, and as shown in fig. 5, an 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 the present embodiment, the moderator 2 includes six sub moderators 21 having different thicknesses, as shown in fig. 1 to 4, for convenience of description, the six sub moderators 21 are numbered as S1, S2, S3, S4, S5, S6, and the thicknesses of S1 to S6 are sequentially increased, as shown in fig. 4, the thicknesses of the sub moderators S1, S2, S3, S4, S5, and S6 are L1, L2, L3, L4, L5, and L6, respectively, and L1< L2< L3< L4< L5< L6. In the present embodiment, the thickness of each sub-moderator is different from the thicknesses of the other sub-moderators, and six sub-moderators have six thicknesses.

In other embodiments, the sub-moderators have different thicknesses, but two or more of the sub-moderators are allowed to have the same thickness, for example, six sub-moderators have five, four, three, or two different thicknesses.

In the present embodiment, a plurality of sub-moderators 21 are uniformly distributed outside the probe 1, and the included angle between any two adjacent sub-moderators 21 is the same, as shown in fig. 4, six sub-moderators 21 are uniformly distributed outside the probe 1, and the included angle between two adjacent sub-moderators 21 is 60 °.

In this embodiment, a connection mechanism (not shown) fixedly connected to an output shaft of the stepping motor is fixedly disposed at an end portion of a lower end of the slowing-down body 2, and the stepping motor is used to connect and drive the object to be rotated (in this embodiment, the object to be rotated is the slowing-down body) to rotate. When the stepping motor drives the slowing-down body 2 to rotate, the position of the detector 1 is kept unchanged, and the preset rotation angle of the stepping motor is 60 degrees at a time. When the neutron spectrometer is in an initial state, the S1 is enabled to face a neutron beam to be measured, the thickness of a moderator outside the detector 1 is S1, after one measurement is completed, the stepping motor rotates 60 degrees, the moderator 2 rotates 60 degrees anticlockwise, the S2 faces the neutron beam to be measured, the thickness of the moderator outside the detector 1 is S2, the thickness of the moderator outside the detector 1 is changed, and the stepping motor rotates again until the neutron measurement is completed.

In other embodiments, the included angle between any two adjacent sub-moderators is different, the driving device selects a stepping motor or other motors, the rotation angle of the motor is set according to the actual included angle between the two adjacent sub-moderators each time, and it is ensured that when the driving device drives the moderators to rotate once, just another adjacent sub-moderators just faces the neutron beam.

In other embodiments, the moderator 2 may have n sub moderator 21 with different thicknesses, where n is 4, 5, 7, 8, 9, 10, 11, 12, or more, as needed.

Example two

The utility model provides a neutron spectrometer of polyhedral structure, as shown in fig. 6 to 11, including detector 1 and the slowing down body 2 of setting outside detector 1, as the utility model discloses an improvement, slowing down body 2 includes a plurality of sub slowing down bodies 21, and a plurality of sub slowing down bodies 21 use detector 1 to outwards disperse the setting as the extreme point, and a plurality of sub slowing down bodies 21 have the thickness of multiple difference.

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

In the present embodiment, as shown in fig. 6 to 11, the slowing-down body 2 includes a plurality of spherical bodies centered on the center of the probe 1, and each sub-slowing-down body 21 includes a spherical body, as shown in fig. 7 to 8, the plurality of spherical bodies are similar in shape, equal in solid angle, and unequal in radius.

In the present embodiment, as shown in fig. 6, the moderator 2 further includes a polyhedral frame 22, the detector 1 is located at the center of the polyhedral frame 22, as shown in fig. 9, the surface of the polyhedral frame 22 is a polygon 221, a cavity 222 is disposed between each polygon 221 and the detector 1, and each spherical body is disposed in one cavity 222.

In the present embodiment, as shown in fig. 9, the polyhedral 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 supporting rod 31, a second supporting rod 32, an arc-shaped rack 33, a first motor (not shown), a second motor 35, a first gear 36, a second gear 37, a third gear 38, a track-fixing groove 39 and a track-fixing rod 34, the upper end of the first supporting rod 31 is fixedly connected with the moderating body 2, the lower end of the first supporting rod 31 is rotatably connected with the second supporting rod 32, the first supporting rod 31, the second supporting rod 32 and the detector 1 are located on the same axis, the lower end of the second supporting rod 32 is fixedly connected with the track-fixing rod 34, the lower end of the track-fixing rod 34 is rotatably connected with the first gear 36, the first gear 36 is engaged with the arc-shaped rack 33, the arc-shaped rack 33 is disposed on a circumference with the center of the detector 1 as a center, the track-fixing rod 34 is slidably disposed in the track-fixing groove 39, the track-fixing groove 39 is disposed on another circumference with the center of the detector 1, a first motor (not shown) drives the first gear 36 to rotate, the second motor 35 is fixedly arranged on the second support rod 32, a second gear 37 is arranged on a rotating shaft of the second motor 35, a third gear 38 is fixedly arranged on the first support rod 31, and the second gear 37 is meshed with the third gear 38.

In this embodiment, the moderator 2 includes 10 sub moderator 21 with different thicknesses, that is, 10 spherical bodies, the regular dodecahedron frame has 10 cavities 222, except that the lowest end surface and the uppermost end surface are not provided with cavities, the remaining cavities 222 are respectively provided with a spherical body, the uppermost end surface of the regular dodecahedron frame is an idle surface, the lowest end surface is a leading-out surface, the leading-out surface is provided with a leading-out hole (not shown), and the high-voltage wire and the signal wire of the detector 1 are led out from the leading-out hole. The upper end of the first support rod 31 is fixedly connected with the leading-out surface of the slowing-down body 2.

As shown in fig. 6, the arc-shaped rack 33 and the track-fixing groove 39 are fixedly installed, and a first motor (not shown) can drive the first gear 36 to rotate and move along the arc-shaped rack 33, so that the first support rod 31, the second support rod 32 and the moderator 2 rotate around the detector 1. The second motor 35 can rotate the first support rod 31, thereby rotating the moderator 2 about the first support rod 31. When the first gear 36 moves along the arc-shaped rack 33, the orbit determination rod 34 moves synchronously along an arc-shaped track in the orbit determination groove 39, namely a fixed moving track, and the function of the orbit determination rod is to enable the whole neutron spectrometer to swing left and right (swing left is negative and swing right is positive) by taking the geometric center of the detector 1 as the center, and the geometric center of the detector 1 is always kept at 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 moderators of different thicknesses (from thin to thick) are transformed as follows:

(1) the neutron spectrometer of the present embodiment is installed, as shown in fig. 6, in an initial state after the neutron spectrometer of the present embodiment is installed, when the neutron spectrometer is in the initial state, one side of a regular pentagonal boundary of the lead-out surface is parallel to the neutron beam shown in fig. 6, and the first support rod 31 is in a state when it is in a vertical position, at this time, the lead-out surface faces directly below, and the idle surface faces directly above. Since the internal angle of the regular pentagon is 108 ° and the dihedral angle of the regular dodecahedron frame is about 116.57 °, the moderator 2 is controlled to rotate clockwise about the first support rod 31 by 18 ° (18 ° in the initial state, clockwise is the rotation direction of the moderator in the top view state, and the same applies hereinafter), and the first support rod 31 and the second support rod 32 swing leftward by 26.57 ° (at this time, the first support rod 31 is at-26.57 ° in the initial state), so that the lower left side 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, to the state shown in fig. 10. A spherical surface body on which neutrons vertically enter in the state is taken as a first moderating body, 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 states (when the first support rod 31 and the second support rod 32 swing 26.57 ° to the left in their initial states), the moderators 2 are sequentially rotated to 90 °, 162 °, -126 °, -54 ° (the rotation angle of the moderators 2 around the first support rod 31 is positive clockwise and negative counterclockwise) of their initial states, 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 states (when the first support rod 31 and the second support rod 32 swing 26.57 ° to the right in their initial states), the detector 1 sequentially rotates to 54 °, 126 °, -162 °, -90 °, -18 ° (the slowing body 2 rotates around the rotation angle of the first support rod 31, clockwise is positive and counterclockwise is negative) of its initial state, corresponding to the sixth, seventh, eighth, ninth and tenth slowing bodies, respectively;

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

The parts not related to in the present invention are all the same as or can be realized by adopting the prior art, and are not repeated herein.

Finally, it should be noted that: in the description of the present invention, the terms "center", "upper", "lower", "left", "right", "front", "rear", "inner", "outer", "vertical", "horizontal", etc. indicate that the directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for convenience of description and understanding of the technical solutions of the present invention, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art. The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.

Claims (9)

1. The utility model provides a polyhedral structure's neutron spectrometer, includes detector (1) and sets up moderator (2) outside detector (1), its characterized in that, moderator (2) include a plurality of son moderator (21), and is a plurality of son moderator (21) use detector (1) outwards disperses the setting for the extreme point, and is a plurality of son moderator (21) has the thickness of multiple difference.

2. A polyhedral structure neutron spectrometer according to claim 1, characterised in that it further comprises driving means (3), said driving means (3) driving the rotation of the moderators (2) so as to orient the sub-moderators (21) of different thickness towards the direction of incidence of the neutron beam.

3. A polyhedral structure neutron spectrometer according to claim 2, characterised in that the moderator (2) is a polyhedral cylindrical structure, the detector (1) is arranged on the axis of rotation of the moderator (2), and the outer end face of the sub-moderator (21) is parallel to the axis of rotation of the moderator (2).

4. A polyhedral structure neutron spectrometer according to claim 3, wherein the outer end face of the sub-moderator (21) is a cylindrical surface.

5. A polyhedral structure neutron spectrometer according to claim 3, characterised in that the driving means (3) is a stepper motor, the output shaft of which is located on the axis of rotation of the moderator body (2) and is fixedly connected to the moderator body (2).

6. A polyhedral structure neutron spectrometer according to claim 2, characterised in that the moderator (2) comprises a plurality of spherical bodies centred on the centre of the detector (1), each of the sub-moderators (21) comprising one of said spherical bodies, said spherical bodies being of similar shape, having equal solid angles and unequal radii.

7. A neutron spectrometer of polyhedral structure according to claim 6, characterised in that said moderator body (2) further comprises a polyhedral frame (22), said detector (1) is located at the centre of said polyhedral frame (22), the faces of said polyhedral frame (22) are polygons (221), a cavity (222) is arranged from each polygon (221) to said detector (1), and each said spherical body is arranged in one said cavity (222).

8. Polyhedral structure neutron spectrometer according to claim 7, characterised in that the polyhedral frame (22) is a regular dodecahedron frame, the surface of which is twelve regular pentagons.

9. The neutron spectrometer with the polyhedral structure according to claim 6, wherein the driving device (3) comprises a first supporting rod (31), a second supporting rod (32), an arc-shaped rack (33), a first motor, a second motor (35), a first gear (36), a second gear (37), a third gear (38), a track fixing groove (39) and a track fixing rod (34), the upper end of the first supporting rod (31) is fixedly connected with the moderating body (2), the lower end of the first supporting rod (31) is rotatably connected with the second supporting rod (32), the first supporting rod (31), the second supporting rod (32) and the detector (1) are positioned on the same axis, the lower end of the second supporting rod (32) is fixedly connected with the track fixing rod (34), and the lower end of the track fixing rod (34) is rotatably connected with the first gear (36), first gear (36) with arc rack (33) meshes mutually, arc rack (33) set up with detector (1) center is on the circumference of centre of a circle, fixed rail stick (34) slide and set up in fixed rail groove (39), fixed rail groove (39) set up with detector (1) center is on another circumference of centre of a circle, first motor drive first gear (36) rotate, second motor (35) are fixed to be set up on second bracing piece (32), install in the pivot of second motor (35) second gear (37), third gear (38) are fixed to be set up on first bracing piece (31), second gear (37) with third gear (38) meshing.

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