阅读说明：本技术 一种高性能缪子自旋探测器 (High-performance muon spin detector ) 是由 潘子文 董靖宇 倪晓杰 叶邦角 于 2020-05-26 设计创作，主要内容包括：本发明公开了一种高性能缪子自旋探测器,包括小尺寸方形塑料闪烁体(1)、长的弯曲形光导(2)、带有方形孔的台阶形圆柱光导固定座(3)、管套(5)、光电倍增管(10)及光电倍增管偏压电路(14)。本发明使用带有方形孔的台阶形圆柱光导固定座耦合长的弯曲形光导和光电倍增管,相比传统的将光导尾部加工成圆台形结构的方法,极大降低了加工难度,而且降低了对信号输出幅度的影响,以及进一步提高了蔽光性能；使用特殊的磁屏蔽设计,可以屏蔽至少60Gs的外加磁场,降低了外部磁场的影响,可以使缪子自旋探测器应用于需要外加磁场的场景；光电倍增管与管套之间使用支撑座和弹簧连接的方式,能使光电倍增管端面和长的弯曲形光导尾部耦合紧密,使光电倍增管在管套内固定良好,同时底盖的螺纹铆合设计能保证蔽光良好。(The invention discloses a high-performance muon spin detector which comprises a small-size square plastic scintillator (1), a long bent light guide (2), a step-shaped cylindrical light guide fixing seat (3) with a square hole, a pipe sleeve (5), a photomultiplier (10) and a photomultiplier biasing circuit (14). Compared with the traditional method for processing the tail part of the light guide into a round table-shaped structure, the method has the advantages that the step-shaped cylindrical light guide fixing seat with the square hole is used for coupling the long bent light guide and the photomultiplier, so that the processing difficulty is greatly reduced, the influence on the signal output amplitude is reduced, and the light-shielding performance is further improved; by using a special magnetic shielding design, an external magnetic field of at least 60Gs can be shielded, the influence of the external magnetic field is reduced, and the muon spin detector can be applied to a scene needing the external magnetic field; the photomultiplier and the pipe sleeve are connected by using the support seat and the spring, so that the end face of the photomultiplier and the tail part of the long curved light guide are tightly coupled, the photomultiplier is well fixed in the pipe sleeve, and meanwhile, the good light shielding performance can be ensured by the threaded riveting design of the bottom cover.)

1. A high performance muon spin detector, characterized by: the device comprises a small-size square plastic scintillator (1), a long bent light guide (2) and a step-shaped cylindrical light guide fixing seat (3) with a square hole, wherein the tail part of the long bent light guide extends into the step-shaped cylindrical light guide fixing seat (3) with the square hole from the square hole and is adhered by opaque glue to fix the long bent light guide and completely shield light; meanwhile, the device also comprises a pipe sleeve (5), a photomultiplier (10), a photomultiplier biasing circuit (14), a permalloy cylinder (16), a step-shaped insulating cylinder (15), a photomultiplier biasing circuit supporting seat (11), a connector fixing seat (12) and a bottom cover (6); the step-shaped insulating cylinder (15) is sleeved outside the photomultiplier (10) and fixed by screws, the permalloy cylinder (16) is sleeved on the step-shaped insulating cylinder (15), the permalloy cylinder (16) extends out of one third of the length of the photomultiplier (10) to shield an external magnetic field as far as possible, and the step-shaped insulating cylinder (15) plays a role in supporting and insulating between the permalloy cylinder (16) and the photomultiplier (10); the photomultiplier tube bias circuit supporting seat (11) is of a cup-shaped hollow structure, and not only can support the photomultiplier tube bias circuit (14), but also can lead wires on the photomultiplier tube bias circuit (14) to extend out of the hollow part; the SHV joint (8) and the BNC joint (7) are fixed on a joint fixing seat (12), and the joint fixing seat (12) is directly connected with a photomultiplier biasing circuit supporting seat (11) by a long screw and a spring (13); the head of the pipe sleeve (5) is turned with an internal thread (9), and when the step-shaped cylindrical light guide fixing seat (3) with the square hole extends into the pipe sleeve (5) to couple the tail part of the long bent light guide (2) with the end surface of the photomultiplier (10), namely the position of the photocathode, the external thread (4) of the step-shaped cylindrical light guide fixing seat (3) with the square hole is in threaded connection with the internal thread (9) at the head of the pipe sleeve (5), so that the connection can be tight, and the light can be completely shielded.

Technical Field

The invention is mainly applied to the field of muon spin spectroscopy application, also relates to the field of particle detection or nuclear detection using a plastic scintillator, and particularly relates to a high-performance muon spin detector.

Background

Muon spin rotation/relaxation/resonance spectroscopy (abbreviated as μ SR spectroscopy) is an important discipline related to magnetism and molecular dynamics in the fields of research of superconduction, magnetic materials, semiconductor materials, lithium batteries, chemical reactions, and the like. The discipline takes highly spin-polarized muon as a magnetic probe to interact with a local magnetic field of a material, and detects the asymmetric distribution of positron generated by the decay of the muon through a detector array so as to realize the characterization of the local magnetism of the material or the attribute related to the local magnetism.

The μ SR spectroscopy relies on an accelerator muir source, which needs to be generated using proton beam targeting, and thus the μ SR experimental platform is typically built on a spallation neutron source with a high energy proton beam. The international formally operated muir source has four positions, wherein ISIS neutrons and muir sources in rutherford alpriton laboratories in the uk build arrayed μ SR spectrometers using a muir spin detector structure of "plastic scintillator + long light guide + photomultiplier". The relevant published documents only report the sizes of different types of muon spin detectors, and do not report the influence of the packaging, the light shielding treatment and the magnetic shielding treatment of the photomultiplier tube on the signal-to-noise ratio of output signals.

At present, a domestic first spallation neutron source, namely a Chinese Spallation Neutron Source (CSNS), is initially built, and a Chinese first experimental muir source (EMuS) based on the CSNS is still in a conceptual design stage and is built in a CSNS II stage upgrading project. Therefore, the construction and operation aspects of the μ SR spectroscopy and muon spin detectors associated therewith are currently blank in the country.

Aiming at the practical requirement of EMuS for mu SR spectroscopy application, an optimal scintillator and light guide packaging, light shielding and photomultiplier tube magnetic shielding scheme is developed around the structure of a muon spinning detector, and the amplitude of the output signal of the detector is increased as much as possible so as to improve the signal-to-noise ratio and the high-low energy positron signal distinguishing capability, thereby ensuring the high-performance operation of a mu SR spectrometer.

Disclosure of Invention

The invention aims at the research blank in the aspect of building a national mu SR spectrometer and provides a high-performance muon spin detector which has high output signal amplitude, high signal-to-noise ratio, good positron high-low energy distinguishing capability and good light shielding property.

The technical scheme adopted by the invention is as follows: a high-performance muon spin detector comprises a small-size square plastic scintillator 1, a long curved light guide 2 and a step-shaped cylindrical light guide fixing seat 3 with a square hole, wherein the tail part of the long curved light guide extends into the step-shaped cylindrical light guide fixing seat 3 with the square hole and is bonded by opaque glue to fix the long curved light guide and completely shield light; meanwhile, the device also comprises a pipe sleeve 5, a photomultiplier tube 10, a photomultiplier tube bias circuit 14, a permalloy cylinder 16, a step-shaped insulating cylinder 15, a photomultiplier tube bias circuit supporting seat 11, a connector fixing seat 12 and a bottom cover 6; a step-shaped insulating cylinder 15 is sleeved outside the photomultiplier tube 10 and fixed by screws, a permalloy cylinder 16 is sleeved on the step-shaped insulating cylinder 15, the permalloy cylinder 16 extends out of one third of the length of the photomultiplier tube 10 to shield an external magnetic field as far as possible, and the step-shaped insulating cylinder 15 plays a role in supporting and insulating between the permalloy cylinder 16 and the photomultiplier tube 10; the photomultiplier tube bias circuit supporting seat 11 is a cup-shaped hollow structure, which can support the photomultiplier tube bias circuit 14 and can enable a lead on the photomultiplier tube bias circuit 14 to extend out of the hollow part; the SHV joint 8 and the BNC joint 7 are fixed on a joint fixing seat 12, and the joint fixing seat 12 is directly connected with a photomultiplier biasing circuit supporting seat 11 by a long screw and a spring 13; the head of the pipe sleeve 5 is turned with an internal thread 9, and when the step-shaped cylindrical light guide fixing seat 3 with a square hole extends into the pipe sleeve 5 to couple the tail part of the long bent light guide 2 with the end surface of the photomultiplier 10, namely the position of the photocathode, the external thread 4 of the step-shaped cylindrical light guide fixing seat 3 with the square hole is in threaded connection with the internal thread 9 at the head of the pipe sleeve 5, so that the connection is tight, and the light can be completely shielded.

The principle of the invention is as follows: the step-shaped cylindrical light guide fixing seat with the square hole is bonded with the long bent light guide by using opaque glue, so that the long bent light guide can be fixed, and the light can be shielded. The stepped cylindrical light guide fixing seat end face with the square hole is a smooth circular face, the end face can be in full contact and stressed uniformly when the stepped cylindrical light guide fixing seat end face is coupled with the photomultiplier, the photomultiplier is not damaged, and the collection efficiency of fluorescence photons can be improved. The detector can normally work under the environment of an external magnetic field by special magnetic shielding design. The bottom cover is provided with threads which can be connected with the tail part of the pipe sleeve in a threaded manner, so that the effects of fixing the connector fixing seat and completely shielding light are achieved. Meanwhile, as the spring is sleeved on the screw connected between the connector fixing seat and the photomultiplier tube biasing circuit supporting seat, when the bottom cover is screwed on the tail part of the tube sleeve, the spring can contract to a certain degree due to pressure, and the design can ensure that the end face of the photomultiplier tube is tightly connected with the long bent light guide tail part so as to improve the collection efficiency of fluorescence photons.

The beneficial effects of the invention are mainly and intensively reflected in the following aspects:

(1) because of the mixed packaging mode of wrapping the small-size square plastic scintillator and wrapping the long bent light guide by the aluminum foil by using the Teflon (PTFE) adhesive tape, the signal output amplitude is improved by about 200 percent compared with the traditional full wrapping mode by using the Teflon adhesive tape;

(2) compared with the traditional method of processing the tail part of the light guide into a round table-shaped structure, the method has the advantages that the long curved light guide and the photomultiplier are coupled by using the stepped cylindrical light guide fixing seat with the square hole, so that the processing difficulty is greatly reduced, the influence on the signal output amplitude is reduced, and the light-shielding performance is further improved;

(3) by using a special magnetic shielding design, an external magnetic field of at least 60Gs can be shielded, the influence of the external magnetic field is reduced, and the muon spin detector can be applied to a scene needing the external magnetic field;

(4) the photomultiplier and the pipe sleeve are connected by using a support seat and a spring, so that the end face of the photomultiplier and the tail part of the long curved light guide are tightly coupled, the photomultiplier is well fixed in the pipe sleeve, and meanwhile, the good light shielding performance can be ensured by the threaded connection design of the bottom cover;

(5) compared with the traditional complete set of mode customized from abroad, the scintillator and light guide use mode of ordering from foreign bulk, cutting and processing in batches at home, the production cost is greatly reduced, and the control, design modification and optimization of the product quality are facilitated.

Drawings

Figure 1 is a schematic diagram of the overall structure of a high-performance muon spin detector of the present invention

FIG. 2 is a cross-sectional view showing the internal structure of a photomultiplier tube sleeve

In the figure: 1. a small-sized square plastic scintillator; 2. a long curved light guide; 3. a step-shaped cylindrical light guide fixing seat with a square hole; 4. an external thread; 5. pipe sleeve; 6. a bottom cover; 7. a BNC joint; 8. an SHV joint; 9. an internal thread; 10. a photomultiplier tube; 11. a photomultiplier tube bias circuit supporting seat; 12. a connector fixing seat; 13. long screws and springs; 14. a photomultiplier tube bias circuit; 15. a stepped insulating cylinder; 16. a permalloy cylinder.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described in detail. Approximating language, as used herein in the following examples, may be applied to identify quantitative representations that could permissibly vary in number without resulting in a change in basic function.

As shown in fig. 1 and 2, a high-performance muon spin detector mainly comprises a small-sized square plastic scintillator 1, a long curved light guide 2, a stepped cylindrical light guide holder 3 with a square hole, a photomultiplier 10, a photomultiplier bias circuit 14, and a sleeve 5.

The small-sized square plastic scintillator 1 and the long curved light guide 2 are bonded using an optical glue. The small-sized square plastic scintillator 1 was wrapped with a teflon (PTFE) tape, and the long curved light guide 2 was wrapped with a thin aluminum foil, and then the whole was encapsulated with a black tape to shield light. The angle of the curved portion of the long curved light guide 2 may be 90 degrees or more than 90 degrees, adjusted according to experimental needs. The tail part of the long bent light guide 2 extends into the square hole of the step-shaped cylindrical light guide fixing seat 3 with the square hole and is flush with the end face of the step-shaped cylindrical light guide fixing seat, and then black or other opaque glue is poured into the gap of the square hole and is firmly adhered to the square hole to shield light. The stepped cylindrical light guide fixing seat 3 with the square hole extends into the pipe sleeve 5 from the head part thereof to be tightly attached to the end surface (the position of the photocathode) of the photomultiplier 10, the surface area of the end part of the stepped cylindrical light guide fixing seat 3 with the square hole is slightly larger than that of the photomultiplier 10, so that the end surface of the photomultiplier 10 is uniformly stressed, and the end surface with the thickness of about 1.5mm of the photomultiplier 10 is effectively protected. The external thread 4 of the stepped cylindrical light guide holder 3 with a square hole can be screwed with the internal thread 9 of the head of the pipe sleeve 5 to fix the long curved light guide to the pipe sleeve 5 and completely shield light. The sizes of the scintillator, the light guide and the square hole of the light guide fixing seat can be modified according to actual needs.

The photomultiplier tube 10 and photomultiplier tube bias circuit 14 are 1 inch R6427 and E2624-14 from hamamatsu which are integrally formed and inseparable during manufacture, with two apertured tab structures extending from the junction to facilitate attachment to other mechanical structures. The stepped insulating cylinder 15 is fitted over the photomultiplier tube 10 and fixed thereto by screws through the photomultiplier tube ear-shaped structure. The permalloy cylinder 16 is sleeved on the step-shaped insulating cylinder 15, and the length of the permalloy cylinder is one third longer than that of the photomultiplier tube 10, so that the holding stage of the photomultiplier tube 10 is completely covered by the permalloy cylinder 16, and an external magnetic field is shielded outside the permalloy cylinder 16 to the maximum extent. The permalloy cylinder 16 is 1mm thick and can shield at least 60Gs external magnetic fields, and the thickness can be increased as required to shield stronger external magnetic fields.

The photomultiplier tube biasing circuit support 11 and the connector holder 12 are connected by three sets of long screws and springs 13. The power line and the signal line on the photomultiplier tube bias circuit 14 extend from the hollow part of the photomultiplier tube bias circuit supporting seat 11 to the connector fixing seat 12 and are respectively welded with the SHV connector 8 and the BNC connector 7 which are riveted on the connector fixing seat 12. The photomultiplier tube bias circuit holder 11 is used for holding the photomultiplier tube 10 and the photomultiplier tube bias circuit 14.

After the wires are welded, optical silicone grease is coated on the end face of the photomultiplier tube 10 to ensure that the end face is tightly coupled with the tail of the long curved light guide, and an air gap is eliminated. A photomultiplier tube 10, a photomultiplier tube bias circuit 14, a photomultiplier tube bias circuit support base 11 and a connector holder 12 are extended into the pipe sleeve 5 from the tail of the pipe sleeve 5. The light pressing connector fixing seat 12 feels the compression of the spring, and the end face of the photomultiplier tube 10 is tightly attached to the end face of the stepped cylindrical light guide fixing seat with the square hole. The bottom cap 6 was screwed to the end of the sleeve 5, and the spring was slightly compressed, indicating that the photomultiplier tube 10 was well coupled to the long curved light guide 2. The threaded design of the bottom cover 6 makes it possible to provide a good screening of the pipe sleeve 5.

In this example, EJ200 manufactured by Eljen corporation was used AS the small-sized square plastic scintillator, P L EXIG L AS brand was used AS the long curved light guide, EJ500 manufactured by Eljen corporation was used AS the optical cement, BC600 manufactured by saint gobain corporation was used AS the optical cement, and EJ550 manufactured by Eljen corporation was used AS the optical silicone grease.

The working principle of the device is as follows: the positron generated by the muon decay deposits energy and generates fluorescence photons when passing through the small-sized square plastic scintillator 1, the fluorescence photons are transmitted on the small-sized square plastic scintillator 1 and the long curved light guide 2, the photons are reflected when passing through the interface of the wrapping material and reenter the long curved light guide 2 for transmission, and finally the photons are transmitted to the photocathode of the photomultiplier 10 to generate photoelectrons through the photoelectric effect. The photoelectrons are multiplied in a plurality of dozen stages of the photomultiplier 10, and an electrical signal is output at the anode thereof and led out from the BNC connector 7 through a signal line of a photomultiplier biasing circuit 14.

The embodiments of the present invention have been described in detail. Any modification, equivalent replacement, and improvement made within the scope of the application of the present invention should be included in the protection scope of the present invention.