阅读说明：本技术 一种热中子束流整形装置 (Thermal neutron beam shaping device ) 是由 梁天骄 陈俊阳 胡志良 童剑飞 周斌 傅世年 张锐强 赵崇光 徐俊 于 2021-08-11 设计创作，主要内容包括：本发明公开的一种热中子束流整形装置,其包括质子通道和装置主体,所述的装置主体设置在质子通道的后端,所述质子通道是具有直线内腔通道的,且所述质子通道内设置有靶体；所述的装置主体包括反射体和慢化体,所述慢化体设置在质子通道的末端,所述质子通道和慢化体的外周设置有反射体；所述慢化体包括中部慢化体和后部慢化体,所述中部慢化体设置在质子通道的后端,且所述中部慢化体的后表面与后部慢化体的前表面相抵连接。本发明通过采用中部慢化体,使中子进入到后部慢化体部分的时候,大部分中子的能量都是处于10keV附近或者低于10keV,从而减少高于10keV的高能中子含量。(The invention discloses a thermal neutron beam shaping device, which comprises a proton channel and a device main body, wherein the device main body is arranged at the rear end of the proton channel, the proton channel is provided with a linear inner cavity channel, and a target body is arranged in the proton channel; the device main body comprises a reflector and a moderator, the moderator is arranged at the tail end of the proton channel, and the reflectors are arranged on the peripheries of the proton channel and the moderator; the moderating body comprises a middle moderating body and a rear moderating body, the middle moderating body is arranged at the rear end of the proton channel, and the rear surface of the middle moderating body is connected with the front surface of the rear moderating body in an abutting mode. By adopting the middle moderator, when neutrons enter the rear moderator, most of the neutrons have energy near 10keV or lower than 10keV, so that the content of high-energy neutrons higher than 10keV is reduced.)

1. The utility model provides a thermal neutron beam current shaping device, includes proton channel and device main part, its characterized in that: the device main body is arranged at the rear end of a proton channel, the proton channel is provided with a linear inner cavity channel, and a target body is arranged in the proton channel;

the device main body comprises a reflector and a moderator, the moderator is arranged at the tail end of the proton channel, and the reflectors are arranged on the peripheries of the proton channel and the moderator;

an annular groove is formed in the moderating body, a cone is arranged in the annular groove, and the annular groove and the cone form a conical groove.

2. The utility model provides a thermal neutron beam current shaping device, includes proton channel and device main part, its characterized in that: the device main body is arranged at the rear end of a proton channel, the proton channel is provided with a linear inner cavity channel, and a target body is arranged in the proton channel;

the device main body comprises a reflector and a moderator, the moderator is arranged at the tail end of the proton channel, and the reflector is arranged on the peripheries of the proton channel and the moderator.

3. The thermal neutron beam shaping device according to claim 2, wherein: the moderating body comprises a middle moderating body and a rear moderating body, the middle moderating body is arranged at the rear end of the proton channel, and the rear surface of the middle moderating body is connected with the front surface of the rear moderating body in an abutting mode.

4. The thermal neutron beam shaping device according to claim 3, wherein: the moderator also includes a front moderator disposed at an end of the proton channel, and the front moderator is disposed at a front surface of the middle moderator and between the middle moderator and the target.

5. The thermal neutron beam shaping device according to claim 3, wherein: an annular groove is formed in the rear portion moderating body, a cone is arranged in the annular groove, and the annular groove and the cone in the rear portion moderating body form a conical groove.

6. The thermal neutron beam shaping device according to claim 5, wherein: the thickness range of the two side walls of the tapered groove is 30-50 mm.

7. The thermal neutron beam shaping device according to claim 5, wherein: the conical vertex angle range of the axial section of the cone is 70-90 degrees.

8. The thermal neutron beam shaping device according to claim 5, wherein: the axial length range of the cone is 100-120 mm.

9. The thermal neutron beam current shaping device according to any one of claims 3, 4 or 5, wherein: the rear surface of the rear portion moderator is provided with a shielding body, and the thickness range of the shielding body is 130-150 mm.

10. The thermal neutron beam shaping device according to claim 9, wherein: an alkali metal halide thin layer is arranged on the rear surface of the shielding body, and the thickness range of the alkali metal halide thin layer is 1-3 mm.

11. The thermal neutron beam shaping device according to claim 1 or 2, wherein: the reflector is polyethylene and is disposed outside the proton channel and moderator.

12. The thermal neutron beam shaping device according to claim 1, wherein: the moderator is polyethylene and is disposed at the end of the proton channel.

13. The thermal neutron beam shaping device according to claim 1 or 2, wherein: the reflector comprises an outer reflector and an inner reflector, the inner reflector is arranged on the outer side of the proton channel, and the outer reflector is arranged on the outer sides of the inner reflector and the moderator.

14. The thermal neutron beam shaping device according to claim 13, wherein: the inner reflector is polyethylene and the outer reflector is carbon.

15. The thermal neutron beam shaping device according to claim 4, wherein: the front moderator is polyethylene and has a thickness of 20-40 mm.

16. The thermal neutron beam shaping device according to claim 3 or 4, wherein: the middle moderator is aluminum fluoride, the thickness range of the middle moderator is 80-100 mm, and the width range of the middle moderator is 120-140 mm.

17. The thermal neutron beam shaping device according to claim 3, wherein: the rear moderator is polyethylene and has a thickness of 100-120 mm.

18. The thermal neutron beam shaping device according to claim 1, wherein: the reflector and the moderator are integrally formed.

19. The thermal neutron beam shaping device according to claim 14 or 17, wherein: the internal reflector and the rear moderator are integrally formed.

20. The thermal neutron beam shaping device according to claim 1 or 2, wherein: the target body is disposed inside the device body.

Technical Field

The invention relates to the technical field of BNCT boron neutron capture treatment, in particular to a thermal neutron beam shaping device for treating superficial tumors.

Background

The neutron beam energy coverage range of the BNCT device for treatment is less than 0.5eV-10keV, and after the neutron beam enters a human body, neutrons are captured by boron-10 atoms with high enrichment degree in tumor cells, charged particles are released, and the tumor cells are killed. BNCT can be classified into superficial tumor and deep tumor, and the tumors are located at different depths, and the energy of neutron beam is different. Wherein, the deep tumor needs a high-energy super-thermal neutron beam (0.5eV-10keV) for treatment, and the superficial tumor needs a low-energy thermal neutron (< 0.5eV) for treatment.

Based on the energy of a thermal neutron beam for treating superficial tumors, in a thermal neutron beam shaping device adopted by the conventional BNCT device, a large number of thermal neutron beam shaping devices adopt a moderating material containing tritium or beryllium, and tritium or beryllium has excellent neutron performance, a lower absorption section and relatively higher moderating efficiency, but the materials such as tritium or beryllium are extremely expensive and are not suitable for serving as the moderating body material of a medium-small neutron source. Secondly, hydrogen containing moderators are also a more widely adopted technical route, because the atomic number of hydrogen is the smallest, the energy lost by neutrons is the largest when the hydrogen collides with a single elastic scattering of neutrons, and moreover, the elastic scattering cross section of hydrogen is larger, so that the volume of the overall moderators can be more compact, and the more compact volume of the moderators can reduce the geometric attenuation to the lowest.

The elastic scattering cross-section of hydrogen elements has a certain specificity, being lower for high energy neutrons with energies above 10keV, but larger for neutrons below 10keV, which makes the elastic scattering cross-section at 10keV need to be 4 times that of 1MeV, larger for high energy neutrons with moderation above 10keV and smaller for neutrons below 10keV if a massive hydrogen-containing moderator is used. In summary, high-energy neutrons are not moderated at all, and a large amount of thermal neutrons react with hydrogen in a moderator to generate collision, absorption and the like, but because the absorption cross section of a hydrogen material is large, the high-energy neutrons need a large hydrogen-containing moderator if the high-energy neutrons are to be completely moderated, and the large hydrogen-containing moderator easily absorbs a large amount of thermal neutrons, so that the technical problem is solved; in addition, lead is mostly adopted as a gamma shielding material in the radiation protection design of the outlet end of the conventional beam shaping device, but the lead has large elastic scattering on neutrons, and although the lead can effectively shield gamma rays, the neutron flux at the outlet end is greatly reduced.

Disclosure of Invention

The invention provides a thermal neutron beam shaping device aiming at one or more problems in the prior art and aims to solve the technical problems in the background technology.

In one aspect of the present invention, a thermal neutron beam shaping device is provided, which includes a proton channel and a device body, wherein the device body is disposed at a rear end of the proton channel, the proton channel has a linear inner cavity channel, and a target body is disposed in the proton channel;

the device main body comprises a reflector and a moderator, the moderator is arranged at the tail end of the proton channel, and the reflectors are arranged on the peripheries of the proton channel and the moderator;

an annular groove is formed in the moderating body, a cone is arranged in the annular groove, and the annular groove and the cone form a conical groove.

In another aspect of the present invention, a thermal neutron beam shaping device is provided, which includes a proton channel and a device body, wherein the device body is disposed at a rear end of the proton channel, the proton channel has a linear inner cavity channel, and a target body is disposed in the proton channel;

the device main body comprises a reflector and a moderator, the moderator is arranged at the tail end of the proton channel, and the reflector is arranged on the peripheries of the proton channel and the moderator.

In some embodiments, the moderators include a central moderator and a posterior moderator, the central moderator being disposed at the posterior end of the proton channel, and the posterior surface of the central moderator being connected against the anterior surface of the posterior moderator.

In some embodiments, the moderator further includes an anterior moderator disposed at an end of the proton channel, and the anterior moderator is disposed at an anterior surface of the central moderator and disposed between the central moderator and the target.

In some embodiments, an annular groove is formed in the rear moderator body, a cone is arranged in the annular groove, and the annular groove and the cone in the rear moderator body form a conical groove.

In some embodiments, the two sidewalls of the tapered groove have a thickness ranging from 30 to 50 mm.

In some embodiments, the cone apex angle of the cone axial cross-section ranges from 70 ° to 90 °.

In some embodiments, the cone has an axial length in the range of 100 to 120 mm.

In some embodiments, the rear moderator rear surface is provided with a shield having a thickness in the range of 130-150 mm.

In some embodiments, the shield has a thin layer of an alkali metal halide disposed on a rear surface thereof, the thin layer of an alkali metal halide having a thickness in a range of 1 to 3 mm.

In some embodiments, the reflector is polyethylene and is disposed outside of the proton channels and moderator.

In some embodiments, the moderator is polyethylene and is disposed at the end of the proton channel.

In some embodiments, the reflectors include an outer reflector and an inner reflector, the inner reflector being disposed outside the proton channels, the outer reflector being disposed outside the inner reflector and the moderator.

In some embodiments, the inner reflector is polyethylene and the outer reflector is carbon.

In some embodiments, the anterior moderator is polyethylene having a thickness in the range of 20 to 40 mm.

In some embodiments, the central moderator is aluminum fluoride having a thickness in the range of 80 to 100mm and a width in the range of 120 to 140 mm.

In some embodiments, the posterior moderator is polyethylene and has a thickness in the range of 100 to 120 mm.

In some embodiments, the reflector and moderator are integrally formed.

In some embodiments, the internal reflector is integrally formed with the posterior moderator.

In some embodiments, the target body is disposed within the interior of the device body.

The thermal neutron beam shaping device provided by the invention has the following beneficial effects:

1. the invention adopts AlF₃To let neutrons enterBy the time the polyethylene moderating body portion is reached, most of the neutrons have energies near or below 10keV, thereby reducing the high energy neutron content above 10 keV;

2. the present invention enhances AlF by employing a frontal polyethylene moderator₃Moderating ability to moderate high energy neutrons to near 10keV without the need for a large volume of AlF₃The material reduces the volume of the whole moderating body, so that the volume of the moderating body occupying the space of the device main body is reduced, and the more compact device volume is beneficial to improving neutron flux;

3. by adopting the conical groove structure, the thermal neutrons which are absorbed or scattered by the moderator to the area outside the outlet can be led out to the outlet end from the groove, meanwhile, the conical structure rather than the vertical structure can prevent the neutrons emitted by the target from escaping from the conical groove without collision or with less collision, and the neutrons escaping from the conical groove can be thermal neutrons after multiple collisions due to the proper cone angle;

4. the neutron flux gain obtained by the conical groove is thermal neutron gain instead of high-energy neutron gain, so that high-energy neutrons are prevented from escaping from the conical groove to the outlet end of the device main body, and the intensity and purity of the thermal neutrons emitted from the outlet end are improved;

5. according to the invention, bismuth is used as a gamma shielding material, so that the high transparency of neutrons can be realized by using bismuth as a shielding body, and gamma rays can be greatly and effectively shielded;

6. according to the invention, carbon is used as a main material of the reflector and is arranged around the moderator, and the carbon is used as a material of the reflector to generate less gamma rays and can effectively reflect neutrons to the moderator area;

7. the invention is achieved by using a valve with a central opening⁶The LiF thin layer can effectively absorb thermal neutrons without releasing gamma rays, so that the finally emitted thermal neutron beams are concentrated in a tumor focus area at the outlet end, and organs at risk around the tumor are protected.

Drawings

For a better understanding of the invention, embodiments thereof will be described with reference to the following drawings:

fig. 1 is a schematic cross-sectional view of a first embodiment of the thermal neutron beam shaping device of the present invention;

FIG. 2 is a schematic cross-sectional view of a second embodiment of the thermal neutron beam shaper of the invention;

FIG. 3 is a schematic cross-sectional view of a third embodiment of the thermal neutron beam shaper of the invention;

FIG. 4 is a schematic cross-sectional view of a fourth embodiment of the thermal neutron beam shaper of the invention;

fig. 5 is a schematic cross-sectional view of a fifth embodiment of the thermal neutron beam shaper of the invention;

FIG. 6 is a schematic cross-sectional view of a sixth embodiment of the thermal neutron beam shaper of the invention;

wherein, in the figures, the respective reference numerals:

1-proton channel, 11-target;

2-device body, 21-reflector, 211-inner reflector, 212-outer reflector, 22-front moderator, 23-middle moderator, 24-back moderator, 241-annular groove, 242-cone, 243-cone groove, 25-shield, 26-thin layer of alkali halide, 27-opening.

Detailed Description

Specific embodiments of the present invention will be described in detail below, and it should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known circuits, materials, or methods have not been described in detail in order to avoid obscuring the present invention.

Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale. It will be understood that when an element is referred to as being "coupled" or "connected" to another element, it can be directly coupled or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements present. Like reference numerals refer to like elements. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention provides a thermal neutron beam shaping device, which comprises a device main body and a proton channel with a linear inner cavity channel, wherein the direction of proton incidence is taken as the positive direction, and the proton incidence position of the proton channel is taken as the front end, so that the device main body is arranged at the rear end of the proton channel, a target body is arranged in the proton channel, and the technical personnel in the field can easily understand that: the rear end of the proton channel extends into the device main body, and the target body is arranged in the device main body; and the main body of the device comprises a reflector and a moderator, the moderator is arranged at the tail end of the proton channel, and the reflector is arranged on the periphery of the proton channel and the moderator.

Meanwhile, in the process of all the embodiments of the present invention, it is required to be explained that: the high-energy neutrons mentioned in the invention are fast neutrons above 10keV, the intermediate-energy neutrons mentioned in the invention are epithermal neutrons between 0.5eV and 10keV, and the low-energy neutrons mentioned in the invention are thermal neutrons below 0.5 eV.

And, what needs to be explained in the course of all embodiments of the present invention are: the outlet end mentioned in the invention is a terminal of neutrons emitted by the thermal neutron beam shaping device.

In the first embodiment shown in fig. 1: thermal neutron beam shaping device comprising middle moderator and rear moderator

In view of the problems in the prior art, in one aspect of the present invention, a first embodiment is proposed, which is mainly due to the fact that the absorption cross section of the hydrogen-containing moderator (polyethylene) is large, the high-energy neutrons require a large hydrogen-containing moderator (polyethylene) if the high-energy neutrons are to be completely moderated, and the conventional moderator uses a massive hydrogen-containing moderator (polyethylene is generally used), but when the high-energy neutrons are not completely moderated into thermal neutrons by using the massive hydrogen-containing moderator, a large amount of intermediate/thermal neutrons already react with hydrogen in the hydrogen-containing moderator (polyethylene) to generate collision, absorption and the like, so that the intermediate or thermal neutrons are absorbed in large quantities, and the massive hydrogen-containing moderator occupies a large volume and space of the apparatus main body, so that AlF is added to the moderator in this embodiment₃(aluminum fluoride) so that when neutrons enter the polyethylene moderator section, most of the neutrons have energies near or below 10keV (i.e., high or intermediate energy neutrons), thereby reducing the high energy neutron content above 10keV, and in particular: the moderators include a central moderator and a posterior moderator, the central moderator being AlF₃(aluminum fluoride), the rear moderator being PE (polyethylene), AlF₃Disposed at the end of the proton channel, and AlF₃Is connected with the front surface of the rear moderator (PE), and when the proton beam strikes the target body from the proton channel to generate high-energy neutrons, the high-energy neutrons are scattered around, so that the high-energy neutrons firstly enter the AlF with the incident direction of the protons as the positive direction₃Above, because AlF₃Has the characteristic of moderating high-energy neutrons to the energy of 10keV, so that the neutrons pass through AlF₃The energy of the later neutrons is mostly near 10keV or below 10keV (i.e. high energy neutrons or intermediate energy neutrons), so that the incidence of the high energy neutron content above 10keV on the rear moderator is reduced, then the neutrons near 10keV or below 10keV are incident on the rear moderator, the rear polyethylene moderator can rapidly moderate the neutrons near 10keV or below 10keV, so that the thermal neutrons are emitted from the outlet end, the absorption to the thermal neutrons is small, and the problem of the existing massive neutron containing materials is solvedThe hydrogen moderator occupies the volume and space of the device main body, thereby greatly inhibiting the absorption of polyethylene to thermal neutrons. To optimize this embodiment, a middle moderator (AlF) was simulated₃) Is 90mm, and preferably 130mm in width, and the rear moderator (PE) is 110mm in thickness.

In addition, the reflector in the process of this embodiment may also be made of PE (polyethylene), and the reflector (PE) and the rear moderator (PE) may be integrally formed.

Although the first embodiment employs AlF₃When neutrons enter the polyethylene moderator section, most of the neutrons have energies near or below 10keV, thereby reducing the high energy neutron content above 10keV, but AlF₃Has a low mean free path and adopts AlF alone₃Larger volumes of AlF are required to moderate high energy neutrons to near 10keV₃The material, and thus the volume of the overall moderator, is still too large, resulting in a large geometric attenuation of neutrons exiting the exit end.

Example two as shown in fig. 2: the thermal neutron beam shaping device also comprises a front moderator

For AlF in the above embodiment₃Has a low mean free path and adopts AlF alone₃Larger volumes of AlF are required to moderate high energy neutrons to near 10keV₃The material, and thus the volume of the unitary moderator, is still too large, resulting in a problem of a large geometric attenuation of neutrons exiting the exit end, so in another aspect of the invention, a second embodiment is proposed, different from the first embodiment: the moderator in the second embodiment further includes: an anterior moderator disposed in the middle moderator (AlF)₃) And is disposed on the front surface of AlF₃Between the target and the front moderator, Polyethylene (PE) is used as the front moderator, and in order to optimize the present embodiment, the thickness of the PE thin layer is preferably 30mm by simulation to enhance AlF₃Moderating high-energy neutrons to the 10keV boundaryNear moderating power without the need to use a larger volume of AlF₃The material reduces the volume of the overall moderator, and further reduces the volume of the moderator occupying the space of the device main body. As will be readily understood by those skilled in the art, the moderator in the course of this example ultimately forms PE + AlF₃+ PE configuration.

Although the second embodiment is in AlF₃The anterior surface is augmented with an anterior polyethylene moderator (PE) to enhance AlF₃Ability to slow high-energy neutrons to near 10keV, however, in this PE + AlF₃In the moderator with + PE configuration, the neutron flux emitted from the outlet end can not satisfy 10⁹n/cm²The requirement of/s ensures that the neutron flux emitted by the thermal neutron beam shaping device can not meet the beam requirement required by BNCT.

Example three as shown in fig. 3: thermal neutron beam shaping device with conical groove

The method for adopting PE + AlF in the above embodiment₃The thermal neutron flux emitted from the outlet end of the moderator with the + PE configuration can not satisfy 10⁹n/cm²In another aspect of the invention, therefore, a third embodiment is provided for increasing the thermal neutron flux exiting the exit end by employing a tapered slot configuration. Specifically, the third embodiment is different from the second embodiment in that: the annular groove is formed in the rear moderating body in the third embodiment, that is, the annular groove is formed in the rear polyethylene moderating body, a polyethylene cone is arranged in the annular groove, the bottom surface of the cone is located in the neutron incidence direction (the positive proton incidence direction), the vertex angle of the cone is located in the neutron emergence direction, and meanwhile, the axis of the cone and the AlF are arranged₃Is perpendicular to the rear surface of the cone, and the bottom surface of the cone is in contact with AlF₃Preferably the thickness of the rear moderator is 110mm in this first embodiment, and the axis of the cone is preferably 110mm in this third embodiment, the apex angle (axis apex) of the cone, which is preferably at the apex angle of the axial cross-section of the cone, is on the rear surface of the rear moderator, as will be readily understood by those skilled in the artThe selection was 80 °, from which it can be seen that the radius of the base of the cone was 110 tan40 ° mm. Because the cone is disposed in the annular groove, the annular groove and the cone form a tapered groove, and the thickness of the two side walls of the tapered groove ranges from 30mm to 50mm, preferably 40mm, it should be noted that the thickness of the two side walls of the tapered groove is the distance between the side surface of the cone (the curved surface formed by the rotation of the side not perpendicular to the axis is called the side surface of the cone) and the inner wall surface of the annular groove, and thus, the two side walls of the tapered groove are parallel to each other, that is, the side surface of the cone and the inner wall surface of the annular groove are parallel. This third embodiment is through adopting the taper groove structure, as long as the cone angle of taper groove is suitable, namely as long as the apex angle of the axial cross section of cone is suitable, and then avoid the neutron of target outgoing not collide or just escape from the taper groove through less collision, that is to say, the cone angle is great can make the neutron that escapes from the taper groove all be the thermal neutron after collision many times, and then, the neutron flux gain that the taper groove obtained is the thermal neutron gain, rather than high energy neutron gain, thereby avoid high energy neutron to escape to the exit end of device main part from the taper groove, improved the intensity and the purity of exit end ejection thermal neutron.

The tapered groove structure (i.e. the tapered groove formed by the annular groove and the cone) adopted in the process of the third embodiment is not limited to one, two or more tapered grooves can be arranged, and a better groove size can be obtained only through simulation calculation of monte carlo software, so that the thermal neutron flux and purity at the outlet end reach better levels.

Example four as shown in fig. 4: thermal neutron beam shaping device provided with shielding body

Aiming at all the above embodiments, the outlet end of the device main body can be mixed with a large amount of gamma rays which are harmful to the treatment of tumor, and the induced radioactivity brought by the device main body after irradiation causes the pollution of rays of a workplace and influences the health of personnel, so in order to solve the technical problem, the rear surface of the rear moderator (polyethylene) in the first embodiment is provided with a shielding body for shielding gamma rays, lead (Pb) is mostly adopted as a shielding material of gamma in the general radiation protection design, but the elastic scattering of Pb to neutrons is large, so the invention adopts bismuth (Bi) as the shielding material of gamma, so that the shielding body adopts Bi to realize high transparency to neutrons and greatly and effectively shield gamma rays, and simultaneously, in order to enable the embodiment to achieve the best effect, through simulation, the preferred thickness of the shield is 140 mm.

Example five as shown in fig. 5: thermal neutron beam shaping device adopting carbon as main material of reflector

In order to solve the above technical problem, in the second embodiment, the reflector includes an outer reflector and an inner reflector, the inner reflector is disposed outside the proton channel, the outer reflector is disposed outside the inner reflector and the moderator, the inner reflector is PE, the outer reflector is carbon, carbon is used as a main material of the reflector, and the inner reflector and the moderator are disposed around the inner PE reflector and the moderator.

In addition, since the inner PE reflector is polyethylene and the rear moderator is also polyethylene, the inner reflector and the rear moderator may be provided to be integrally molded.

Example six as shown in fig. 6: is provided with⁶Thermal neutron beam shaping device with LiF thin layer

In all the embodiments and embodiments described above, in order to achieve the best tumor treatment effect, the thermal neutron beam can be aligned with the tumor region, and the thermal neutron beam can only be emitted from the middle beam exit, so a third embodiment is proposed, which is different from the first embodiment in that: the rear surface of the shield is also provided with a thin layer of an alkali metal halide⁶LiF，⁶The thin LiF layer is preferably 2mm thick, the process being described⁶An opening is arranged in the middle of the LiF thin layer and is used for leading out heatThe sub-beam has small collimation influence due to the fact that when the epidermal tumor is treated, only the tumor region is aligned with the outlet of the thermal neutron beam, a collimator does not need to be arranged in the device main body, neutrons need to be collimated when the deep tumor is treated, and the neutrons can penetrate through the epidermis and reach the tumor part without being dispersed on the epidermis layer⁶An opening for leading out thermal neutron beam is arranged in the middle of the LiF thin layer,⁶the LiF thin layer can effectively absorb thermal neutrons without releasing gamma rays, and the LiF thin layer with the middle opening is adopted through simulation⁶The LiF thin layer absorbs the quantity of thermal neutrons, the resulting thermal neutron flux is reduced by less than 5%, and the thermal neutron flux emitted from the outlet end can still meet the requirement of 10⁹n/cm²The requirements are satisfied in terms of/s. Of course, the thin alkali metal halide layer is not limited to use⁶LiF, other alkali metal halides can also be used.

The invention has the beneficial effects that:

1. the invention adopts AlF₃Reducing the high energy neutron content above 10keV by having a majority of the neutrons at energies near or below 10keV when entering the polyethylene moderator section;

2. the present invention enhances AlF by employing a frontal polyethylene moderator₃Moderating ability to moderate high energy neutrons to near 10keV without the need for a large volume of AlF₃The material reduces the volume of the whole moderating body, so that the volume of the moderating body occupying the space of the device main body is reduced, and the more compact device volume is beneficial to improving neutron flux;

3. by adopting the conical groove structure, the thermal neutrons which are absorbed or scattered by the moderator to the area outside the outlet can be led out to the outlet end from the groove, meanwhile, the conical structure rather than the vertical structure can prevent the neutrons emitted by the target from escaping from the conical groove without collision or with less collision, and the neutrons escaping from the conical groove can be thermal neutrons after multiple collisions due to the proper cone angle;

4. the neutron flux gain obtained by the conical groove is thermal neutron gain instead of high-energy neutron gain, so that high-energy neutrons are prevented from escaping from the conical groove to the outlet end of the device main body, and the intensity and purity of the thermal neutrons emitted from the outlet end are improved;

5. according to the invention, bismuth is used as a gamma shielding material, so that the high transparency of neutrons can be realized by using bismuth as a shielding body, and gamma rays can be greatly and effectively shielded;

6. according to the invention, carbon is used as a main material of the reflector and is arranged around the moderator, and the carbon is used as a material of the reflector to generate less gamma rays and can effectively reflect neutrons to the moderator area;

7. the invention is achieved by using a valve with a central opening⁶The LiF thin layer can effectively absorb thermal neutrons without releasing gamma rays, so that the finally emitted thermal neutron beams are concentrated in a tumor focus area at the outlet end, and organs at risk around the tumor are protected.

The above embodiments are only specific embodiments of the present invention, and the description thereof is specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications are possible without departing from the inventive concept, and such obvious alternatives fall within the scope of the invention.