CN106512233A - Beam shaping body for neutron capture therapy - Google Patents

Abstract

The invention provides a beam shaping body for the neutron capture therapy. The beam shaping body comprises a beam inlet, a target material, a speed-retarding body adjacent to the target material, a reflector arranged to surround the outside of the speed-retarding body, a thermal neutron absorber adjacent to the speed-retarding body, a radiation shield arranged inside the beam shaping body, and a beam outlet. The nuclear reaction occurs between the target material and a proton beam that shoots into the beam inlet to generate neutrons, and the neutrons form a neutron beam which defines a main axis. The speed-retarding body slows down the neutrons generated from the target material to an epithermal neutron energy region. The speed-retarding body comprises the following materials of MgF2 and 6LiF, wherein the weight percentage of 6LiF to MgF2 is 0.1-5%. The above materials, in the form of powders or powder-pressed blanks, are subjected to powder sintering treatment by powder sintering equipment to turn into blocks. The reflector guides the neutrons deviating from the main axis back to the main axis so as to improve the intensity of an epithermal neutron beam. The thermal neutron absorber is used for absorbing thermal neutrons so as to avoid the excessive dose of the neutrons during the treatment on shallow normal tissues. The radiation shield is used for shielding leaky neutrons and photons so as to reduce the dose thereof on normal tissues in non-irradiated regions.

Description

For the beam-shaping body of neutron capture treatment

Technical field

A kind of a kind of the present invention relates to beam-shaping body, more particularly to beam-shaping body for neutron capture treatment.

Background technology

With the development of atomics, such as radiation cure such as cobalt 60, linear accelerator, electron beam has become one of Main Means for the treatment of of cancer.But conventional photonic or electronic therapy are limited by lonizing radiation physical condition itself, while tumor cell is killed, also substantial amounts of normal structure in beam approach can be damaged；Additionally, due to difference of the tumor cell to lonizing radiation sensitivity, traditional radiation therapy is for the malignant tumor for relatively having radiation resistance（Such as：Multirow glioblastoma multiforme（glioblastoma multiforme）, melanocytoma（melanoma））Treatment effect it is often not good.

In order to reduce the radiation injury of tumor surrounding normal tissue, chemotherapy（chemotherapy）In target therapy concept be just applied in radiation cure；And be directed to the tumor cell of radiation resistance, at present also actively development with high relative biological effect（relative biological effectiveness, RBE）Radiation source, such as proton therapeutic, heavy particle therapy, neutron capture treatment etc..Wherein, neutron capture treatment is the such as boron neutron capture treatment with reference to above two concept, is gathered by specificity of the boracic medicine in tumor cell, coordinates accurately neutron beam regulation and control, there is provided selected than the more preferable treatment of cancer of conventional radiation.

Boron neutron capture is treated（Boron Neutron Capture Therapy, BNCT）It is to utilize boracic（¹⁰B）Medicine has the characteristic of high capture cross section to thermal neutron, by¹⁰B(n,α) ⁷Li neutron captures and karyokinesiss reaction are produced⁴He and⁷Two heavy burden charged particle of Li.See figures.1.and.2, which respectively show boron neutron capture reaction schematic diagram and¹⁰B(n,α) ⁷Li neutron capture nuclear equation formulas, the average energy of two charged particles is about 2.33MeV, with High Linear transfer (Linear Energy Transfer, LET), short range feature, the linear energy transfer of alpha-particle and range are respectively 150 keV/ μm, 8 μm, and⁷Li heavy burdens particle is then 175 KeV/ μm, 5 μm, the integrated range of two particle is approximately equivalent to a cell size, therefore for the radiation injury that organism is caused can be confined to cell level, when boracic drug selectivity be gathered in tumor cell, the appropriate neutron of collocation penetrates source, just the purpose that tumor cell is killed in local can be reached on the premise of not normal tissue causes too major injury.

Because the effect of boron neutron capture treatment depends on tumor cell position boracic drug level and hankers quantum count, therefore the binary lonizing radiation treatment of cancer that is otherwise known as（binary cancer therapy）；It follows that except the exploitation of boracic medicine, neutron is penetrated source flux and occupies key player with the improvement of quality in the research that boron neutron capture is treated.

The content of the invention

Flux and the quality in source is penetrated to improve neutron, one aspect of the present invention provides a kind of beam-shaping body for neutron capture treatment, which includes beam entrance, target, it is adjacent to the slow body of target, it is enclosed in slow external reflector, the thermal neutron absorber adjoined with slow body, the radiation shield being arranged in beam-shaping body and beam outlet, there is nuclear reaction to produce neutron in target with the proton beam from the incidence of beam entrance, neutron forms neutron beam, neutron beam limits a main shaft, slow body is by the neutron degradation produced from target to epithermal neutron energy area, the material of slow body is by containing PbF₄、Al₂O₃、AlF₃、 CaF₂Or MgF₂In one or more mixing material and occupy containing PbF₄、Al₂O₃、AlF₃、 CaF₂Or MgF₂In the percentage by weight of one or more mixing material containing for 0.1-5%⁶The material mixing of Li elements is made, the powder sintered equipment of material Jing of wherein slow body becomes in bulk by powder sintering process by powder or powder compact, reflector will deviate from the neutron of main shaft and lead back to main shaft to improve epithermal neutron intensity of beam, thermal neutron absorber is used for absorbing thermal neutron to avoid causing multiple dose during treatment with shallow-layer normal structure, and radiation shield is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area.

Beam-shaping body is further used for the treatment of accelerator boron neutron capture, the treatment of accelerator boron neutron capture passes through accelerator by proton accelerate (beamacceleration), target is made of metal, proton beam accelerates to the energy that be enough to overcome target atom core coulomb repulsion, there is nuclear reaction to produce neutron with target, beam-shaping physical ability is by neutron slowly to epithermal neutron energy area, and reduce thermal neutron and fast neutron content, epithermal neutron energy area is between 0.5eV to 40keV, subzone is hankered less than 0.5eV, fast-neutron range is more than 40keV, reflector is by making with the strong material of neutron reflection ability, thermal neutron absorber is made up of the material big with thermal neutron action section.

Preferably reflector is made up of at least one in Pb or Ni as a kind of, thermal neutron absorber by⁶Li makes, and is provided with air duct between thermal neutron absorber and beam outlet, and radiation shield includes photon shielding and the neutron shield by made by PE by made by Pb.

In order to effectively slow down to neutron beam, on the one hand, as it is a kind of preferably, it is cone-shaped that slow body is arranged to that two rightabouts adjoin each other.

Further, cone-shaped including the first diameter, Second bobbin diameter and the 3rd diameter, the first diameter length is 1cm-20cm, and Second bobbin diameter length is 30cm-100cm, and the 3rd diameter length is 1cm-50cm, and the density of the material of slow body is the 80%-100% of solid density.

Yet further, clearance channel is set between slow body and reflector to improve epithermal neutron flux, the material of slow body is by containing MgF₂Powder and occupy MgF₂Powder weight is 0.1-5%'s⁶LiF powder is mixed.

On the other hand, powder sintered equipment is hot-press sintering equipment or discharging plasma sintering equipment, and powder sintering process is hot-pressing sintering technique or discharge plasma sintering process.

Preferably, hot-press sintering equipment includes heating furnace, the pressue device being placed in heating furnace, mould, the powder or powder compact and the control device for controlling hot-press sintering equipment normal work that load in mould, and hot-pressing sintering technique comprises the steps：With appropriate powder or powder compact filling mould；Hot pressing furnace is opened with preset pressure and temperature parameter；Mobile pressue device pressurizes to the powder in mould or powder compact；Control device controls hot-press sintering equipment in the case of normal work；It is powered to sintering in bulk.

As another kind preferably, discharging plasma sintering equipment includes first electrode, second electrode, the conductive die being placed between first electrode and second electrode, the impulse current generator for providing pulse current to mould, the pressue device with the pressing means for pressurization and the control device for controlling pulse current transmitter and pressue device, at least one of first electrode and second electrode can be moved, and at least one of first electrode and second electrode are connected with pressue device the powder being placed in mould so as to pressurize；Discharge plasma sintering process comprises the steps：By appropriate powder filling mould；Mobile second electrode is pressurizeed to the powder in mould；Impulse current generator is opened so that so as to produce plasma, powder particle surface is activated and generates heat by conductive die conduction by control device；Sintering in bulk.

Discharging plasma sintering equipment further includes the displacement measurement system for measuring the displacement of pressue device, for controlling the atmosphere control system of atmosphere in mould, for the water-cooling system of cooling, for measuring the temperature measuring equipment of the temperature in discharging plasma sintering equipment, discharge plasma sintering process further includes following steps：Control device command displacement measuring system is guaranteeing displacement measurement system normal work, control device controls atmosphere control system to guarantee that atmosphere is in the case of normal work in mould, control device controls water-cooling system to guarantee water-cooling system normal work, and control device controls temperature measuring equipment to guarantee the temperature in discharging plasma sintering equipment in the case of normal work.

" cylinder " or " bar shape " described in the embodiment of the present invention refers to the structure that side along direction as shown is basically unchanged to the overall trend of opposite side its outline, wherein one contour line of outline can be line segment, such as the corresponding contour line of cylindrical shape, it can also be the larger circular arc for being close to line segment of curvature, such as the corresponding contour line of the larger sphere body shape of curvature, the whole surface of outline can be rounding off, can also be non-rounding off, such as many raised and grooves have been done on the surface of the larger sphere body shape of cylindrical shape or curvature.

" cone " or " cone-shaped " described in the embodiment of the present invention refers to the structure that side along direction as shown is tapered into the overall trend of opposite side its outline, wherein one contour line of outline can be line segment, such as the corresponding contour line of cone shape, it can also be circular arc, such as the corresponding contour line of sphere body shape, the whole surface of outline can be rounding off, or non-rounding off, such as do many raised and grooves on the surface of cone shape or sphere body shape.

Description of the drawings

Fig. 1 is boron neutron capture reaction schematic diagram.

Fig. 2 is¹⁰B(n,α) ⁷Li neutron capture nuclear equation formulas.

Fig. 3 is the floor map of the beam-shaping body for neutron capture treatment in first embodiment of the invention, wherein, is provided with clearance channel between slow body and reflector.

Fig. 4 is the floor map of the beam-shaping body for neutron capture treatment in second embodiment of the invention, and wherein, slow body is arranged to the clearance channel position in bicone, and first embodiment and is filled with slow body material.

Fig. 5 is the floor map of the beam-shaping body for neutron capture treatment in third embodiment of the invention, and wherein, slow body is arranged to the clearance channel position in bicone, and first embodiment and is filled with reflector material.

Fig. 6 is the neutron yield rate figure of neutron energy and the double differential of neutron angle.

Fig. 7 is the floor map of the beam-shaping body for neutron capture treatment in fourth embodiment of the invention, and wherein, slow body is arranged to cylinder.

Fig. 8 is the floor map of the beam-shaping body for neutron capture treatment in fifth embodiment of the invention, and wherein, slow body is arranged to cylinder+cone.

Fig. 9 is the preparation facilitiess schematic diagram of the slow body material in one of embodiment of the invention, and wherein, the preparation facilitiess are discharging plasma sintering equipment.

Figure 10 is the preparation facilitiess schematic diagram of the slow body material in one of embodiment of the invention, and wherein, the preparation facilitiess are hot-press sintering equipment.

Specific embodiment

Neutron capture treats the application as a kind of means of effective treating cancer in recent years gradually to be increased, and wherein treats most commonly seen with boron neutron capture, and the neutron for supplying the treatment of boron neutron capture can be supplied by nuclear reactor or accelerator.By taking the treatment of accelerator boron neutron capture as an example, the basic module of accelerator boron neutron capture treatment is generally included for charged particle embodiments of the invention（Such as proton, deuteron etc.）Accelerator, target and hot removal system and the beam-shaping body for being accelerated, charged particle is wherein accelerated to produce neutron with metal targets effect, suitable nuclear reaction is selected according to the characteristic such as required neutron yield rate and energy, available acceleration charged particle energy and size of current, the materialization of metal targets, the nuclear reaction for often coming into question has⁷Li(p,n)⁷Be and⁹Be(p,n)⁹B, both reactions are all the endothermic reaction.The energy threshold of two kinds of nuclear reactions is respectively 1.881MeV and 2.055MeV, due to the epithermal neutron that the preferable neutron source of boron neutron capture treatment is keV energy grades, if being only slightly taller than the proton bombardment lithium metal target of threshold values in theory using energy, the neutron of relative mental retardation can be produced, it is not necessary to too many slow process and just can be used for clinic, but lithium metal（Li）With beryllium metal（Be）Two kinds of targets are not high with the proton-effect section of threshold values energy, are to produce sufficiently large neutron flux, generally from higher-energy proton causing nuclear reaction.

Preferably target should possess high neutron yield rate, the neutron energy distribution of generation is close to epithermal neutron energy area（Will be described in more detail below）, without wear by force too much radiation produce, the characteristic such as cheap easily operated and high temperature resistant of safety, but actually and cannot find and meet required nuclear reaction, using target made by lithium metal in embodiments of the invention.But well known to those skilled in the art, the material of target can also be made up of other metal materials in addition to the above-mentioned metal material talked about.

Requirement for hot removal system is then different according to the nuclear reaction for selecting, such as⁷Li(p,n)⁷Be is because of metal targets（Lithium metal）Fusing point and thermal conductivity coefficient it is poor, the requirement to hot removal system just compared with⁹Be(p,n)⁹B is high.Adopt in embodiments of the invention⁷Li(p,n)⁷The nuclear reaction of Be.

No matter nuclear reaction of the neutron source of boron neutron capture treatment from nuclear reactor or accelerator charged particle and target, be all mixed radiation field, the i.e. beam of generation contain the neutron of mental retardation to high energy, photon；For the boron neutron capture of deep tumor is treated, in addition to epithermal neutron, remaining radiation content is more, causes the ratio of the non-selective dosage deposition of normal structure bigger, therefore these can cause the radiation of unnecessary dosage reduce as far as possible.Except air beam quality factor, for knowing more about the dose distribution that neutron is caused in human body, used in embodiments of the invention, human body head tissue prosthesis carry out Rapid Dose Calculation, and are used as the design reference of neutron beam with prosthese beam quality factor, will be described in more detail below.

International Atomic Energy Agency（IAEA）For the neutron source of clinical boron neutron capture treatment, given five air beam quality factor suggestions, this five suggestions can be used for the quality of the different neutron sources of comparison, and be provided with as reference frame when selecting neutron the way of production, design beam-shaping body.This five suggestion difference are as follows：

Epithermal neutron beam flux Epithermal neutron flux> 1 x 10⁹ n/cm²s

Fast neutron pollutes Fast neutron contamination< 2 x 10^-13 Gy-cm²/n

Photon contamination Photon contamination< 2 x 10^-13 Gy-cm²/n

Thermal and epithermal neutron flux ratio thermal to epithermal neutron flux ratio < 0.05

Middle electron current and flux ratio epithermal neutron current to flux ratio > 0.7

Note：Epithermal neutron energy area hankers subzone less than 0.5eV between 0.5eV to 40keV, and fast-neutron range is more than 40keV.

1st, epithermal neutron beam flux：

In neutron beam flux and tumor, boracic drug level has together decided on the clinical treatment time.If the enough height of tumor boracic drug level, for the requirement of neutron beam flux just can be reduced；If conversely, boracic drug level is low in tumor, needing high flux epithermal neutron to give tumor enough dosage.IAEA is that epithermal neutron number every square centimeter per second is more than 10 for the requirement of epithermal neutron beam flux⁹, the neutron beam under this flux can substantially control treatment time for current boracic medicine in one hour, and short treatment time, also can be compared with effectively utilizes boracic medicine in the intra-tumor limited holdup time in addition to positioning to patient and comfort level is advantageous.

2nd, fast neutron pollution：

As fast neutron can cause unnecessary normal tissue dose, therefore it is regarded as polluting, this dosage size and neutron energy are proportionate, therefore should reduce the content of fast neutron in neutron beam design as far as possible.Fast neutron pollution definition is the adjoint fast neutron dosage of unit epithermal neutron flux, and IAEA is less than 2 x 10 to the suggestion that fast neutron pollutes^-13 Gy-cm²/n。

3rd, photon contamination（Gamma-ray contamination）：

Gamma-rays belong to, the organized dosage deposition of institute on course of the beam can non-selectively be caused, therefore reduce the exclusive requirement that gamma-rays content is also neutron beam design, gamma-ray contamination definition is the adjoint gamma-rays dosage of unit epithermal neutron flux, and suggestions of the IAEA to gamma-ray contamination is less than 2 x 10^-13 Gy-cm²/n。

4th, thermal and epithermal neutron flux ratio：

As thermal neutron decay speed is fast, penetration capacity is poor, into after human body, most of energy deposition is in skin histology, in addition to the neutron source that the Several Epidermal Tumors such as melanocytoma need to be treated as boron neutron capture with thermal neutron, thermal neutron content should be reduced for deep tumors such as cerebromas.IAEA is less than 0.05 to the suggestion of thermal and epithermal neutron flux ratio.

5th, middle electron current and flux ratio：

Middle electron current and flux ratio represent the directivity of beam, ratio is bigger represent neutron beam before tropism it is good, it is high before the neutron beam of tropism can reduce the normal surrounding tissue dosage caused because of neutron diverging, also improve in addition and can treat depth and pendulum pose gesture elasticity.IAEA centerings electron current is more than 0.7 with flux ratio suggestion.

Using prosthese organized in dose distribution, according to the dose versus depth curve of normal structure and tumor, push away to obtain prosthese beam quality factor.Following three parameter can be used to carry out the comparison that different neutron beams treat benefit.

1st, effective therapeutic depth：

Tumor dose is equal to the depth of normal structure maximal dose, and the position after this depth, the dosage that tumor cell is obtained are less than normal structure maximal dose, that is, lose the advantage of boron neutron capture.This parameter represents the penetration capacity of neutron beam, and effective therapeutic depth is bigger to represent that medicable tumor depth is deeper, and unit is cm.

2nd, effective therapeutic depth close rate：

That is the tumor dose rate of effective therapeutic depth, also equal to the maximum dose rate of normal structure.Because normal structure receives the factor that accumulated dose is that impact can give tumor accumulated dose size, therefore parameter affects the length for the treatment of time, and effective therapeutic depth close rate is bigger to represent that the irradiation time given needed for tumor doses is shorter, and unit is cGy/mA-min.

3rd, dose therapeutically effective ratio：

From brain surface to effective therapeutic depth, the mean dose ratio that tumor and normal structure are received, referred to as dose therapeutically effective ratio；The calculating of mean dose, can be obtained by dose versus depth curve integration.Dose therapeutically effective ratio is bigger, and the treatment benefit for representing the neutron beam is better.

In order that beam-shaping body has in design compares foundation, except beam quality factor and three above-mentioned parameters in the air of five IAEA suggestions, the following parameter good and bad for assessing the performance of neutron beam dosage in the embodiment of the present invention, is also utilized：

1st, irradiation time≤30min（The proton current that accelerator is used is 10mA）

2、 30.0RBE-Gy can treat depth >=7cm

3rd, tumor maximal dose >=60.0RBE-Gy

4th, normal cerebral tissue's maximal dose≤12.5RBE-Gy

5th, skin maximal dose≤11.0RBE-Gy

Note：RBE（Relative Biological Effectiveness）For relative biological effect, due to the biological effect that photon, neutron can be caused it is different, so dosage item as above is respectively multiplied by the relative biological effect of different tissues in the hope of dose,equivalent.

Flux and the quality in source is penetrated to improve neutron, embodiments of the invention are the improvement proposed for the beam-shaping body for neutron capture treatment, as one kind preferably, be the improvement for the beam-shaping body for the treatment of accelerator boron neutron capture.As shown in Figure 3，The beam-shaping body 10 for neutron capture treatment in first embodiment of the invention，Which includes beam entrance 11、Target 12、The adjacent slow body 13 with target 12、The reflector 14 being enclosed in outside slow body 13、The thermal neutron absorber 15 adjoined with slow body 13、The radiation shield 16 being arranged in beam-shaping body 10 and beam outlet 17，There is nuclear reaction to produce neutron in target 12 with the proton beam from 11 incidence of beam entrance，Neutron forms neutron beam，Neutron beam limits a major axis X，Slow body 13 is by the neutron degradation produced from target 12 to epithermal neutron energy area，Reflector 14 will deviate from the neutron of major axis X and lead back to major axis X to improve epithermal neutron intensity of beam，The slow clearance channel 18 that arranges between body 13 and reflector 14 is to improve epithermal neutron flux，Thermal neutron absorber 15 is used for absorbing thermal neutron to avoid causing multiple dose with shallow-layer normal structure during treatment，Radiation shield 16 is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area.

The treatment of accelerator boron neutron capture by accelerator by proton accelerate (beamacceleration), used as a kind of preferred embodiment, be made up of lithium metal, and proton beam accelerates to the energy that be enough to overcome target atom core coulomb repulsion, is occurred with target 12 by target 12⁷Li(p,n)⁷Be nuclear reactions are producing neutron.Beam-shaping body 10 by neutron slowly to epithermal neutron energy area, and can reduce thermal neutron and fast neutron content, and, by making with the material that fast neutron action section is big, epithermal neutron action section is little, used as a kind of preferred embodiment, slow body 13 is by D for slow body 13₂O、AlF₃、Fluental^TM、CaF₂、Li₂CO₃ 、MgF₂And Al₂O₃In at least one make.Reflector 14 by making with the strong material of neutron reflection ability, used as a kind of preferred embodiment, be made up of at least one in Pb or Ni by reflector 14.Thermal neutron absorber 15 is made up of the material big with thermal neutron action section, as a kind of preferred embodiment, thermal neutron absorber 15 by⁶Li makes, and is provided with air duct 19 between thermal neutron absorber 15 and beam outlet 17.Radiation shield 16 includes photon shielding 161 and neutron shield 162, and used as a kind of preferred embodiment, radiation shield 16 is included by lead（Pb）Made by photon shielding 161 and by polyethylene（PE）Made by neutron shield 162.

Wherein, slow body 13 is arranged to cone-shaped, the as shown in Figure 3 direction that two rightabouts adjoin each other, the left side of slow body 13 be towards left side taper into it is cone-shaped, the right side of slow body 13 be towards right side taper into it is cone-shaped, both adjoin each other.As it is a kind of preferably, the left side of slow body 13 be set to towards left side taper into it is cone-shaped, and right side can also be arranged to its allothimorph shape with this it is cone-shaped adjoin each other, such as bar shape etc..Reflector 14 is closely enclosed in around slow body 13, clearance channel 18 is provided between slow body 13 and reflector 14, so-called clearance channel 18 refers to the region for easily allowing neutron beam to pass through of the sky that unused solid material is covered, and the such as clearance channel 18 could be arranged to air duct or vacuum passage.Thermal neutron absorber 15 close to the setting of slow body 13 is by very thin one layer⁶Li materials are made, and the shielding of the photon by made by Pb 161 in radiation shield 16 can be arranged with reflector 14 and is integrated, it is also possible to be arranged to split, and the neutron shield 162 by made by PE can be positioned adjacent to the position of beam outlet 17 in radiation shield 16.Air duct 19 is provided between thermal neutron absorber 15 and beam outlet 17, the sustainable neutron that will deviate from major axis X leads back to major axis X to improve epithermal neutron intensity of beam in this region.Prosthese B is arranged on and exports at 17 about 1cm apart from beam.It is well known to those skilled in the art, photon shielding 161 can be made up of other materials, as long as playing a part of to shield photon, neutron shield 162 can also be made up of other materials, other places can also be arranged on, as long as disclosure satisfy that the condition of shielding seepage neutron.

For the difference for comparing the beam-shaping body for being provided with clearance channel with the beam-shaping body for being not provided with clearance channel, as shown in Figure 4 and Figure 5, which respectively show the 3rd embodiment that clearance channel is filled using reflector using the second embodiment of slow body filling and by clearance channel.With reference first to Fig. 4，The beam-shaping body 20 includes beam entrance 21、Target 22、The adjacent slow body 23 with target 22、The reflector 24 being enclosed in outside slow body 23、The thermal neutron absorber 25 adjoined with slow body 23、The radiation shield 26 being arranged in beam-shaping body 20 and beam outlet 27，There is nuclear reaction to produce neutron in target 22 with the proton beam from 21 incidence of beam entrance，Neutron forms neutron beam，Neutron beam limits a major axis X 1，Slow body 23 is by the neutron degradation produced from target 22 to epithermal neutron energy area，Reflector 24 will deviate from the neutron of major axis X 1 and lead back to major axis X 1 to improve epithermal neutron intensity of beam，It is cone-shaped that slow body 23 is arranged to that two rightabouts adjoin each other，The left side of slow body 23 be towards left side taper into it is cone-shaped，The right side of slow body 23 be towards right side taper into it is cone-shaped，Both adjoin each other，Thermal neutron absorber 25 is used for absorbing thermal neutron to avoid causing multiple dose with shallow-layer normal structure during treatment，Radiation shield 26 is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area.

As it is a kind of preferably, the target 22, slow body 23, reflector 24, thermal neutron absorber 25 and radiation shield 26 in second embodiment can with it is identical in first embodiment, and radiation shield therein 26 is included by lead（Pb）Made by photon shielding 261 and by polyethylene（PE）Made by neutron shield 262, the neutron shield 262 can be arranged on beam outlet 27 at.Air duct 28 is provided between thermal neutron absorber 25 and beam outlet 27.Prosthese B1 is arranged on and exports at 27 about 1cm apart from beam.

Refer to Fig. 5，The beam-shaping body 30 includes beam entrance 31、Target 32、The adjacent slow body 33 with target 32、The reflector 34 being enclosed in outside slow body 33、The thermal neutron absorber 35 adjoined with slow body 33、The radiation shield 36 being arranged in beam-shaping body 30 and beam outlet 37，There is nuclear reaction to produce neutron in target 32 with the proton beam from 31 incidence of beam entrance，Neutron forms neutron beam，Neutron beam limits a major axis X 2，Slow body 33 is by the neutron degradation produced from target 32 to epithermal neutron energy area，Reflector 34 will deviate from the neutron of major axis X 2 and lead back to major axis X 2 to improve epithermal neutron intensity of beam，It is cone-shaped that slow body 33 is arranged to that two rightabouts adjoin each other，The left side of slow body 33 be towards left side taper into it is cone-shaped，The right side of slow body 33 be towards right side taper into it is cone-shaped，Both adjoin each other，Thermal neutron absorber 35 is used for absorbing thermal neutron to avoid causing multiple dose with shallow-layer normal structure during treatment，Radiation shield 36 is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area.

As it is a kind of preferably, the target 32, slow body 33, reflector 34, thermal neutron absorber 35 and radiation shield 36 in 3rd embodiment can with it is identical in first embodiment, and radiation shield therein 36 is included by lead（Pb）Made by photon shielding 361 and by polyethylene（PE）Made by neutron shield 362, the neutron shield 362 can be arranged on beam outlet 37 at.Air duct 38 is provided between thermal neutron absorber 35 and beam outlet 37.Prosthese B2 is arranged on and exports at 37 about 1cm apart from beam.

MCNP softwares are adopted below（It is by Los Alamos National Laboratories of the U.S. (LosAlamos National Laboratory) develop based on DSMC for calculating the common software bag of the neutron in 3 D complex geometry, photon, charged particle or coupling neutron/photon/charged particle transport problem）Simulation to these three embodiments is calculated：

Wherein, as following table one shows performance of the beam quality factor in these three embodiments in air（In form, each name lexeme is same as above, will not be described here, similarly hereinafter）：

Table one：Beam quality factor in air

Wherein, as following table two show dosage show these three embodiments in performance：

Table two：Dosage is showed

Wherein, as following table three shows simulation value of the good and bad parameter of assessment neutron beam dosage performance in these three embodiments：

Table three：The good and bad parameter of assessment neutron beam dosage performance

Note：Can learn from three above-mentioned tables：The beam-shaping body of clearance channel is provided between slow body and reflector, and the treatment benefit of its neutron beam is best.

As the neutron produced from lithium target has the higher characteristic of Forward averaging energy, as shown in Figure 6, average neutron energy of the neutron scattering angle between 0 ° -30 ° is about 478keV, and average neutron energy of the neutron scattering angle between 30 ° -180 ° about only has 290keV, if can be by the geometry for changing beam-shaping body, more collision is produced to neutron with slow body before making, and lateral less collisions of neutron Jing just can reach beam outlet, neutron slow optimization, efficient raising epithermal neutron flux should be can reach in theory then.Geometry from beam-shaping body is set about below, evaluates the geometry of different beam-shaping bodies for the impact of epithermal neutron flux.

As shown in Figure 7，It illustrates the geometry of the beam-shaping body in fourth embodiment，The beam-shaping body 40 includes beam entrance 41、Target 42、The adjacent slow body 43 with target 42、The reflector 44 being enclosed in outside slow body 43、The thermal neutron absorber 45 adjoined with slow body 43、The radiation shield 46 being arranged in beam-shaping body 40 and beam outlet 47，There is nuclear reaction to produce neutron in target 42 with the proton beam from 41 incidence of beam entrance，Slow body 43 is by the neutron degradation produced from target 42 to epithermal neutron energy area，The neutron that reflector 44 will deviate from leads back to improve epithermal neutron intensity of beam，Slow body 43 is arranged to bar shape，Preferably，It is arranged to cylindrical shape，Thermal neutron absorber 45 is used for absorbing thermal neutron to avoid causing multiple dose with shallow-layer normal structure during treatment，Radiation shield 46 is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area，Air duct 48 is provided between thermal neutron absorber 45 and beam outlet 47.

As shown in Figure 8，It illustrates the geometry of the beam-shaping body in the 5th embodiment，The beam-shaping body 50 includes beam entrance 51、Target 52、The adjacent slow body 53 with target 52、The reflector 54 being enclosed in outside slow body 53、The thermal neutron absorber 55 adjoined with slow body 53、The radiation shield 56 being arranged in beam-shaping body 50 and beam outlet 57，There is nuclear reaction to produce neutron in target 52 with the proton beam from 51 incidence of beam entrance，Neutron forms neutron beam，Neutron beam limits a major axis X 3，Slow body 53 is by the neutron degradation produced from target 52 to epithermal neutron energy area，Reflector 54 will deviate from the neutron of major axis X 3 and lead back to major axis X 3 to improve epithermal neutron intensity of beam，It is cone-shaped that slow body 53 is arranged to that two rightabouts adjoin each other，The left side of slow body 53 is bar shape，The right side of slow body 53 be towards right side taper into it is cone-shaped，Both adjoin each other，Thermal neutron absorber 25 is used for absorbing thermal neutron to avoid causing multiple dose with shallow-layer normal structure during treatment，Radiation shield 26 is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area.

As it is a kind of preferably, the target 52, slow body 53, reflector 54, thermal neutron absorber 55 and radiation shield 56 in the 5th embodiment can with it is identical in first embodiment, and radiation shield therein 56 is included by lead（Pb）Made by photon shielding 561 and by polyethylene（PE）Made by neutron shield 562, the neutron shield 562 can be arranged on beam outlet 57 at.Air duct 58 is provided between thermal neutron absorber 55 and beam outlet 57.Prosthese B3 is arranged on and exports at 57 about 1cm apart from beam.

Simulation using MCNP softwares to the cylinder+cone in the slow body of the cylinder in the slow body of bicone, fourth embodiment in second embodiment and the 5th embodiment is calculated below：

Wherein, as following table four shows performance of the beam quality factor in these three embodiments in air：

Table four：Beam quality factor in air

Wherein, as following table five show dosage show these three embodiments in performance：

Table five：Dosage is showed

Wherein, as following table six shows simulation value of the good and bad parameter of assessment neutron beam dosage performance in these three embodiments：

Table six：The good and bad parameter of assessment neutron beam dosage performance

Note：Can learn from three above-mentioned tables：Slow body is arranged at least one cone-shaped, the treatment benefit of its neutron beam is preferable.

" cylinder " or " bar shape " described in the embodiment of the present invention refers to the structure that side along direction as shown is basically unchanged to the overall trend of opposite side its outline, wherein one contour line of outline can be line segment, such as the corresponding contour line of cylindrical shape, it can also be the larger circular arc for being close to line segment of curvature, such as the corresponding contour line of the larger sphere body shape of curvature, the whole surface of outline can be rounding off, can also be non-rounding off, such as many raised and grooves have been done on the surface of the larger sphere body shape of cylindrical shape or curvature.

" cone " or " cone-shaped " described in the embodiment of the present invention refers to the structure that side along direction as shown is tapered into the overall trend of opposite side its outline, wherein one contour line of outline can be line segment, such as the corresponding contour line of cone shape, it can also be circular arc, such as the corresponding contour line of sphere body shape, the whole surface of outline can be rounding off, or non-rounding off, such as do many raised and grooves on the surface of cone shape or sphere body shape.

In terms of source flux is penetrated in an important improvement, it is necessary to discuss that the material of slow body is made, hereafter by taking first embodiment and accompanying drawing 3 as an example, slow body 13 is further described.

Slow body 13 presents antipodal pair of two cone directions cone structure, and the material of slow body 13 is by containing AlF₃Or CaF₂Or MgF₂In at least one material make, slow body 13 have the first diameter D1, Second bobbin diameter D2 and the 3rd diameter D3.Opening is provided with first diameter D1 to accommodate target 12, and Second bobbin diameter D2 is set at the full-size of double cone structures.For BNCT, in order to reach enough slow effects, first diameter D1 length is 1cm-20cm, Second bobbin diameter D2 length is 30cm-100cm, 3rd diameter D3 length is 1cm-50cm, and as one kind preferably, the first diameter D1 length is 10cm, Second bobbin diameter D2 length is 70cm, and the 3rd diameter D3 length is 30cm.In order to obtain such large-sized slow body 13, and the density of its material for the 80%-100% of solid density, there is provided the preparation of following three kinds slow body materials.

1. It is long brilliant

First with MgF₂As a example by, with further reference to application for a patent for invention Publication No. CN102925963A, it is incorporated herein in its entirety as the long brilliant reference for preparing.As long brilliant mode, generally by kind of crystalline substance and contain MgF₂Powder be put in crucible, MgF is grown by certain mode₂Monocrystalline.

Needs give special heed to, and so-called here " monocrystalline " refers to single crystal of single growth molding, and is not single crystal grain（There was only a kind of crystal form and comprise only a crystal grain, molecule, courtyard are all to arrange regularly in the crystal grain）.What is be best understood from is this single crystal grain and multiple crystal grain（It is the size and shape difference of each crystal grain, and orientation is also in disorder, no obvious profile, does not also show anisotropy）It is corresponding.Below with respect to " monocrystalline " definition with it is where like.

Through investigation, PbF₄、AlF₃、 CaF₂And Al₂O₃Can also be prepared by similar mode.

2. It is powder sintered

With MgF₂Powder or MgF₂Addition accounts for MgF₂The 0.1-5%'s of powder weight⁶As a example by the mixed-powder of LiF, powder sintered introduction is carried out, it is preferable that below with MgF₂Addition accounts for MgF₂The 0.1-5%'s of powder weight⁶Powder sintered introduction is carried out as a example by the mixed-powder of LiF.

Slow body plays particularly important role in beam-shaping body, which is responsible for the slow heavy responsibility of neutron and appoints greatly, needs to lower fast neutron intensity as much as possible, can not excessively be slowly thermal neutron by neutron again, on the other hand, it is also necessary to the gamma-rays derived in lowering moderating process.Jing is studied and is shown, equably inserts a small amount of containing in slow body⁶The material of Li, can effectively lower gamma-ray intensity, though neutron intensity will be made slightly to subtract, but still possess the quality of original beam.After further study, by MgF₂Powder doping accounts for MgF₂The 0.1-5%'s of powder weight⁶The powder mixing of LiF, compared to being individually not added with⁶The MgF of LiF powder₂Powder, the mixed-powder can be more efficiently absorbed thermal neutron and effectively suppress gamma-rays.

By MgF₂Powder doping accounts for MgF₂The 0.1-5%'s of powder weight contains⁶Used as a kind of slow body material, well known to those skilled in the art, this contains the material mixing of Li⁶The material of Li can be any being easy to and MgF₂Powder doping any physical form together, such as this contains⁶The material of Li can be liquid, can also be powder.This contains⁶The material of Li can be any being easy to and MgF₂Powder doping any compound together, this contains⁶The material of Li can be⁶LiF or⁶Li₂CO₃.As one kind preferably, by MgF₂Powder with account for MgF₂The 0.1-5%'s of powder weight⁶Further combined with getting up, in sintering process, powder particle the physical and chemical processes such as mutually flowing, diffusion, dissolving, recrystallization to the powder or powder compact of LiF will occur, make powder further fine and close, eliminate part or all of hole therein.Sintering processing can have many kinds, and such as solid-phase sintering, i.e. sintering temperature is in body of powder below the fusing point of each constituent element；If two or more constituent elements in liquid-phase sintering, i.e. powder compact, sintering is possible to carry out more than the fusing point of certain constituent element, thus a small amount of liquid phase occurs in powder compact during sintering；Hot pressed sintering, i.e., in sintering, apply pressure to body of powder, and to promote its densification process, hot pressing is shaping and the sinter bonded powder, directly obtains the technical process of product；Discharge plasma sintering, i.e., by the ON-OFF DC pulse voltages that particular power source control device occurs are added on powder body test portion, except utilizing the sintering facilitation caused by usual electro-discharge machining（Discharge impact pressure and Joule heating）Outward, the Spark Discharges for also producing between effectively utilizes pulsed discharge initial stage powder body（Moment produces high-temperature plasma）Caused sintering facilitation realizes the Fast Sintering technology of densification by TRANSIENT HIGH TEMPERATURE field.The powder sintered equipment of material Jing of slow body becomes in bulk by powder sintering process by powder or powder compact.

Well known to those skilled in the art, other sintering processings are also capable of achieving MgF₂Or AlF₃Or CaF₂Or PbF₄In at least one or several mixture add again⁶Preparation of the powder of LiF as the material of slow body.As one kind preferably, hereafter using hot pressed sintering and discharge plasma sintering as powder sintered embodiment.

2.1 Discharge plasma sintering

Discharge plasma sintering melts plasma activation, hot pressing, resistance heating and is integrated, the consistency that programming rate is fast, sintering time is short, sintering temperature is low, crystal grain is uniform, is conducive to controlling the fine structure of sintered body, obtains material is high, and has high, safe and reliable simple to operate, repeatability, save space, save energy and low cost and other advantages.Discharge plasma sintering is added between powder particle due to Impulsive Current, there is the both positive and negative polarity of electric field induction between powder particle, there is electric discharge between granule under pulse current effect, excite plasma, the intergranular contact portion of energetic particle hits produced by electric discharge, make material produce evaporation and play purification and activation, in the dielectric layer of cluster of grains, dielectric layer batch (-type) repid discharge to power storage occurs.Due to there is pulse current between powder or powder compact, and pulse current is moment, the generation of interrupted, altofrequency, in the heat discharge that powder particle is produced not in contact with position, and the Joule heat that powder particle contact site is produced, the diffusion of powder particle atom is greatly facilitated all, its diffusion coefficient than usual hot pressing condition under it is much greater, it is powder sintered rapid so as to reach.Furthermore, due to the addition of pulse current, electric discharge position and joule heat position in powder all quickly can be moved, enable the sintering homogenization of powder or powder compact.During discharge plasma sintering, when discharging between granule, up to thousand of spending to 10,000 degree of localized hyperthermia can instantaneously be produced, cause evaporation in particle surface and melt, cervical region is formed in grain contact point, as heat is delivered to particle surface from heating center immediately and spreads to surrounding, cervical region is quickly cooled down and makes vapour pressure be less than other positions.Gaseous substance condenses upon another important feature that evaporation-solidification transmission that cervical region formation is higher than ordinary sinter method is discharge plasma sintering process.Crystal grain is acted on by Current Heating and vertical uniaxial pressure, and bulk diffusion, grain boundary decision is all strengthened, and accelerates sintering densification process, therefore high-quality sintered body is obtained with the relatively low temperature and comparison short time.Discharge plasma sintering process can be regarded as the result of granule electric discharge, conductive heater and pressurization comprehensive function.

Fig. 9 is refer to, a kind of schematic diagram of discharging plasma sintering equipment is there is disclosed.Discharging plasma sintering equipment 100 includes first electrode 101、Second electrode 102、The conductive die 103 being placed between first electrode 101 and second electrode 102、The impulse current generator 104 of pulse current is provided to mould 103、With the pressing means 1051 for pressurization、1052 pressue device 105 and the control device 106 for controlling impulse current generator 104 and pressue device 105，At least one of first electrode 101 and second electrode 102 can be moved，Pressing means 1051、At least one of 1052 can move，As one kind preferably，First electrode 101 and pressing means 1051 are fixed，Second electrode 102 and pressing means 1052 can be moved，The powder being placed in so as to pressurize in mould 103 or powder compact 107.As one kind preferably, conductive die 103 is set to lead or graphite.Discharging plasma sintering equipment 100 further includes the displacement measurement system 108 for measuring the displacement of pressue device 105, for controlling the atmosphere control system 109 of atmosphere in the mould 103, the water-cooling system 111 cooled down for controlling water-cooled vacuum room 110, for measuring the temperature measuring equipment 112 of the temperature in discharging plasma sintering equipment 100.Mould 103 and powder or the logical upper pulse current of powder compact 107, in addition to offer discharge impact pressure and Joule heat are sintered, further with the Spark Discharges produced between pulsed discharge initial stage powder body（Moment produces high-temperature plasma）Caused sintering facilitation realizes Fast Sintering by TRANSIENT HIGH TEMPERATURE field, so that powder or powder compact 107 become block from pulverulence, so-called bulk is formed in one, without such as long brilliant mode, suitable slow body size is spliced into by the operation such as polishing or polishing by monocrystalline.

The discharging plasma sintering equipment 100 is sintered using DC pulse current direct-electrifying and is pressurizeed, and Jing control devices 106 control heating rate and sintering temperature by the size for adjusting pulsed direct current.Whole sintering process can be carried out under vacuum conditions, also can be carried out in protective atmosphere, such as oxygen or hydrogen.

Under oxygen atmosphere, as oxygen is sintered thing surface adsorption or chemical reaction effect occurs, plane of crystal is made to form the non-stoichiometric compound of cation omission type, cation room increases, while the oxygen in making closed pore can be directly entered lattice, and be diffused along surface as oxygen ion vacancy, spread and sinter acceleration.When sintering is controlled by positive diffusions, oxidizing atmosphere or partial pressure of oxygen are higher and be conducive to cation room to be formed, acceleration of sintering；When being controlled by anion diffusion, reducing atmosphere or relatively low partial pressure of oxygen will cause oxygen ion vacancy to produce and acceleration of sintering.

In a hydrogen atmosphere during sintered sample, due to hydrogen atom radius very little, it is easy to spread and be conducive to the material of the types such as the elimination of closed pore, aluminium oxide to sinter the available sintered body sample close to solid density under hydrogen atmosphere.

Sintering temperature is one of crucial parameter during plasma Fast Sintering.The determination of sintering temperature will consider the density requirements of sintered body sample phase in version at high temperature, the growth rate of crystal grain, the prescription of sample and sample.Generally, with the rising of sintering temperature, sample consistency is integrally in rising trend, and this explanation sintering temperature has significantly impact to sample consistency degree, and sintering temperature is higher, and in sintering process, mass transfer speed is faster, and sample is more easy to be closely knit.

But, temperature is higher, and the growth rate of crystal grain is faster, and its mechanical property is poorer.And temperature is too low, the consistency of sample is just very low, can't meet the quality requirement.Contradiction between temperature and grain size requires a suitable parameter in the selection of temperature.

The temperature retention time extended under sintering temperature, typically all acceleration of sintering can complete to some extent, improve the microstructure of sample, and this sintering to VISCOUS FLOW mechanism is more obvious, and affect less to the sintering of bulk diffusion and surface diffusion mechanism.In sintering process, when being typically incubated only 1 minute, the density of sample just reaches more than the 96.5% of solid density, with the prolongation of temperature retention time, the consistency increase of sample, but excursion is not very big, illustrates that although temperature retention time has a certain impact to the consistency of sample, but action effect is not apparent.But the temperature retention time for unreasonably extending under sintering temperature, crystal grain in this time, grow up by play of having to go to the toilet, aggravation secondary recrystallization effect, is unfavorable for the performance requirement of sample, and the time too short densification that can cause sample declines, it is therefore desirable to select suitable temperature retention time.

The quickening of time heating rate, so that sample reaches required temperature in a short period of time, the growth time of crystal grain can greatly reduce, this not only contributes to suppress growing up for crystal grain, obtain fine grain ceramics of uniform size, moreover it is possible to save time, energy saving and improve the utilization rate of agglomerating plant.But, due to the restriction of equipment itself, heating rate is too fast to cause a devastating effect to equipment.Therefore the quickening heating rate in the admissible scope as far as possible.But, reflect in the experimental data of actual measurement and arrive.It is different from sintering temperature and temperature retention time, impact of the heating rate to sample consistency shows contrary result, i.e. with the increase of heating rate, the trend that the performance roughening of sample consistency is gradually reduced, have scholar to propose this is because near the sintering temperature raising of heating rate equivalent to shortening temperature retention time, thus sample consistency can decline.In actual high-temperature sintering process, temperature-rise period is generally divided into three phases, respectively from room temperature to 600 DEG C or so, 600 DEG C to 900 DEG C or so, 900 DEG C to sintering temperature：First stage is the preparatory stage, and heating rate is relatively slow；Second stage be it is controllable be rapidly heated the stage, heating rate general control is 100 ~ 500 (DEG C/min)；Phase III is the buffer stage for heating up, and the phase temperature is slowly increased to sintering temperature, and temperature retention time is usually 1 ~ 7 minute, furnace cooling after insulation, and cooldown rate is up to 300 DEG C/min.

Powder carries out compressing and sintering immediately Jing after being substantially discharged and process.There is serious plastic deformation in sintered material under the collective effect of resistance Joule heat and pressure, apply forming pressure and be conducive to strengthening the contact between powder particle, the residual gas between increase sintering area, discharge sintered powder, improve product intensity, density and its surface smoothness.The size of forming pressure is typically based on the compressibility of sintered powder and the requirement to performances such as density of sintered material, intensity is determined, typically in the range of 15～30 MPa, there may come a time when up to 50 MPa, even more high.Generally, forming pressure is bigger, and the density of sintered material is higher.The pressurization persistent period also has a great impact to density of sintered material, and suitable pressing time is different regarding species, the physical dimension of powder size and institute's sintered material of sintered material, needs to be determined by experiment.It is demonstrated experimentally that the pressurization persistent period is equal to or slightly greater than discharge time, this is the essential condition for obtaining most high-density sintered material.Easy to understand from sintering and solid state reaction mechanism, pressure is bigger, and in sample, particle packing is tightr, and mutual contact point and contact area increase sintering are accelerated.Sample can be so made to obtain more preferable consistency, and can effective inhibiting grain growth and reduction sintering temperature.Therefore the pressure for selecting is generally 30 ~ 50Mpa.But there are some researches show, when when sintering, external pressure is 30Mpa and 50Mpa, the consistency difference of sample is simultaneously little, and this explanation consistency is more obvious only within a certain range with the phenomenon that pressure increases.

Discharge plasma sintering is had the advantage that compared to conventional sintering technique：Sintering velocity is fast；Improve material microstructure and improve the performance of material.

Well known to those skilled in the art, mould can be made using other conductive materials, and discharging plasma sintering equipment can also be arranged to two electrodes and maintain static, and only at least one pressing means can be moved.

The technical process of discharge plasma sintering is divided into four-stage.First stage：Apply initial pressure to powder sample, make to be fully contacted between powder particle, to be then able to produce uniform and sufficient plasma discharging in powder sample；Second stage：Apply pulse current, in the presence of pulse current, powder particle contact point produces plasma discharging, and particle surface produces micro- exothermic phenomenon due to activation；Phase III：The pulse power is closed, resistance heating is carried out to sample, till predetermined sintering temperature and sample contraction completely is reached；Fourth stage：Release.Rationally the main technologic parameters such as control initial pressure, sintering time, forming pressure, pressurization persistent period, sintering temperature, heating rate can obtain the good material of combination property.

Due to the arch bridge effect between powder particle, they can not typically be fully contacted, therefore, in order that the plasma in sample producing uniformly and being substantially discharged during electric spark sintering, farthest activated particle surface is accelerating sintering densification process, need to apply appropriate initial pressure to sintered powder, be fully contacted powder particle.The big I of initial pressure is different with sintered powder kind, sintered part size and performance.First pressing is too small, and electric discharge phenomena are confined in amount of powder, causes powder local melting；Pressure is excessive, will suppress electric discharge, and then delays to sinter diffusion process.According to existing document, it is sufficiently carried out for continuing electric discharge, this initial pressure is typically no more than 10MPa.

When powdered sample preferable with electric spark sintering electric conductivity, due to resistance heating outwardly and inwardly carrying out from sample simultaneously, therefore sintering time is extremely short, even moment, but sintering time length should be different regarding powder quality, kind and performance, and generally several seconds to a few minutes；When large-scale, refractory metal powder material is sintered, even up to dozens of minutes.Sintering time affects larger to product density, for making densification process fully be carried out, therefore, to assure that certain sintering time.

It is generally acknowledged that, the sintering to powder that is rapidly heated during discharge plasma sintering is highly advantageous, have activated the densification Mechanism of material because it inhibits the non-densifying mechanism of material, therefore, heating rate is improved, is improved can the densification degree of sample.

As one kind preferably, discharge plasma sintering process comprises the steps：With appropriate powder or the filling mould 103 of powder compact 107；Mobile pressue device 105 pressurizes to the powder in mould 103 or powder compact 107；Impulse current generator 104 is opened so that so as to produce plasma, powder particle surface is activated and generates heat by 103 conduction of mould by control device 106；Sintering in bulk.Discharge plasma sintering process further includes following steps：106 command displacement measuring system 108 of control device is guaranteeing 108 normal work of displacement measurement system, control device 106 controls atmosphere control system 109 to guarantee the atmosphere in mould 103 in the case of normal work, control device 106 controls water-cooling system 111 to guarantee which in the case of normal work, and control device 106 controls temperature measuring equipment 112 to guarantee the temperature in discharging plasma sintering equipment 100 in the case of normal work.So-called normal work refers to discharging plasma sintering equipment and the alarm signals such as vision, tactile or the audition of human perception does not occur, and such as alarm lamp is lighted, and alarm lamp sounds, and police instruction vibration etc. is such.

2.2 Hot pressed sintering

Hot pressed sintering is that dry powder is filled in model, then is heated from single shaft direction in pressurization, makes molding and sintering while a kind of sintering method for completing.Hot pressing and sintering technique production technology very abundant, classifies at present without unified standard and standard.Vacuum hotpressing, atmosphere hot pressing, vibrations hot pressing, balanced hot pressing, high temperature insostatic pressing (HIP), reaction hot-pressing and ultra-high pressure sintering can be divided into according to present situation.Hot pressed sintering is carried out simultaneously due to heating pressurization, and powder is in hot plastic state, contributes to contact diffusion, the carrying out of flowing mass transport process of granule, thus briquetting pressure is only 1/10 for colding pressing；Sintering temperature can also be reduced, is shortened sintering time, is grown up so as to resist crystal grain, obtain the product that crystal grain is tiny, consistency is high and mechanical, electric property is good.

In order to prepare slow body material using hot-pressing sintering technique, Figure 10 is refer to, hot-press sintering equipment 200 is main to include heating furnace 201, the pressue device 202 being placed in heating furnace 201, mould 203, the powder or powder compact 204 and control device 205 that load in mould 203., generally using electricity as thermal source, heating element heater is by SiC, MoSi or nickel reeling, platinum wire, molybdenum filament etc. for heating furnace 201.Pressue device 202 requires that speed is gentle, pressurize is constant, pressure flexible, typically has lever and fluid pressure type.According to the requirement of material character, it can also be reducing atmosphere or inert atmosphere that pressure atmosphere can be air.Mould 203 requires high intensity, high temperature resistant, antioxidation and does not cohere with hot-pressed material that 203 thermal coefficient of expansion of mould should be consistent or approximate with hot-pressed material, as one kind preferably, adopts graphite jig in the present embodiment.Control device 205 causes hot-press sintering equipment 200 in the case of normal work.So-called normal work refers to discharging plasma sintering equipment and the alarm signals such as vision, tactile or the audition of human perception does not occur, and such as alarm lamp is lighted, and alarm lamp sounds, and police instruction vibration etc. is such.

With MgF₂As a example by the slow body of target is prepared using hot-pressing sintering technique, its technological process of production generally comprises following steps, MgF₂The grinding of raw material preparing raw material, screening process proceed to mould high temperature sintering high temperature hot pressing sintering cooling high temperature insostatic pressing (HIP) high temperature sintering cooling of coming out of the stove and come out of the stove grinding, polishing, bonding finished product.

As one kind preferably, here omits the process step that the sintering of the powder processing step and postorder of preamble is completed.Hot-pressing sintering technique comprises the steps：With appropriate powder or the filling mould 203 of powder compact 204；Hot pressing furnace 201 is opened with preset pressure and temperature parameter；Mobile pressue device 202 pressurizes to the powder in mould 203 or powder compact 204；Control device 205 controls hot-press sintering equipment 200 in the case of normal work；It is powered to sintering in bulk.

Needs further illustrate be, step " mobile pressue device 202 pressurizes to the powder in mould 203 or powder compact 204 " in hot-pressing sintering technique can be used as precharge, can also be powered it is synchronous carry out, will step " mobile pressue device 202 pressurizes to the powder in mould 203 or powder compact 204 " and step " energization is to sinter in bulk " unite two into one.

Some parameters for listing long brilliant, discharge plasma sintering and hot pressed sintering in following table compare, as the material of the slow body application in a kind of beam-shaping body of the neutron capture treatment disclosed in present invention that is more convenient for, especially need to manufacture under the maximum preconditions up to the size of 100cm of Second bobbin diameter D2, it is recommended here that using slow body material made by powder sintered, concrete detailed description in detail please see below.

Table seven：The comparison of long brilliant and powder sintering process

Note：Upper table eliminates the 0.1-5%'s of respective addition as powder main material⁶LiF powder, though MgF is only listed in upper table₂+LiF、AlF₃+ LiF and CaF₂+ LiF these three slow body materials are compared using the parameter of as above technique, but well known to those skilled in the art, other slow body material such as Al₂O₃+ LiF can also easily make contrast.

Can learn from upper table, although the density for preparing slow body material by the way of long crystalline substance can reach is close to solid density, the 99.99% of solid density is reached such as, but due to monocrystalline size it is less, wanting to reach the large-sized slow body material of target needs to be spliced by many individual monocrystalline, during it may also be desirable to carry out which other operations such as mirror finish, not only take very long, and cost and technology difficulty are all very big.

The density for preparing slow body material by the way of powder sintered can also reach the 80%-100% of solid density.As one kind preferably, the density of slow body material reaches the 99.99% of solid density.Solid density compared with the solid density of the slow body material that long crystal type is obtained substantially it is indiscriminate simultaneously, which is with the obvious advantage in terms of the size, time, cost and technology difficulty for obtaining.Obtained using slow its actual size of body material that discharge plasma sintering is prepared as required, a kind of mode can customize out the mould for being adapted to needs, another way adopts common die, such as the mould of diameter 70cm* thickness 2cm, then spliced by several and can just be completed, on the premise of cost and technology difficulty are equally matched with vacuum heating-press sintering and HIP sintering, the time of 1 month or so on its manufacturing time, is only needed to.

Structure represented by the content being not limited to described in above example for the beam-shaping body of neutron capture treatment of present invention announcement and accompanying drawing.Apparently change, replacement or modification that material, shape and position on the basis of the present invention to wherein component is made, all within the scope of protection of present invention.

Claims (10)

1. it is a kind of for neutron capture treatment beam-shaping body, it is characterised in that：The beam-shaping body includes beam entrance, target, the slow body for being adjacent to the target, is enclosed in the slow external reflector and the slow body thermal neutron absorber for adjoining, the radiation shield being arranged in the beam-shaping body and beam outlet, there is nuclear reaction to produce neutron in the target with the proton beam from beam entrance incidence, the neutron forms neutron beam, the neutron beam limits a main shaft, by the neutron degradation produced from the target to epithermal neutron energy area, the material of the slow body is by containing PbF for the slow body₄、Al₂O₃、AlF₃、 CaF₂Or MgF₂In one or more mixing material and occupy and described contain PbF₄、Al₂O₃、AlF₃、 CaF₂Or MgF₂In the percentage by weight of one or more mixing material containing for 0.1-5%⁶The material mixing of Li elements is made, the powder sintered equipment of material Jing of wherein described slow body becomes in bulk by powder sintering process by powder or powder compact, the reflector will deviate from the neutron of the main shaft and lead back to the main shaft to improve epithermal neutron intensity of beam, the thermal neutron absorber is used for absorbing thermal neutron to avoid causing multiple dose during treatment with shallow-layer normal structure, and the radiation shield is used for shielding the neutron and photon of seepage to reduce the normal tissue dose in non-irradiated area.

2. it is according to claim 1 for neutron capture treatment beam-shaping body, it is characterised in that：The beam-shaping body is further used for the treatment of accelerator boron neutron capture, the treatment of accelerator boron neutron capture passes through accelerator by proton accelerate (beamacceleration), the target is made of metal, the proton beam accelerates to the energy that be enough to overcome target atom core coulomb repulsion, there is nuclear reaction to produce neutron with the target, the beam-shaping physical ability is by neutron slowly to epithermal neutron energy area, and reduce thermal neutron and fast neutron content, the epithermal neutron energy area is between 0.5eV to 40keV, it is described to hanker subzone less than 0.5eV, the fast-neutron range is more than 40keV, the reflector is by making with the strong material of neutron reflection ability, the thermal neutron absorber is made up of the material big with thermal neutron action section.

3. it is according to claim 2 for neutron capture treatment beam-shaping body, it is characterised in that：The reflector is made up of at least one in Pb or Ni, the thermal neutron absorber by⁶Li makes, and is provided with air duct between the thermal neutron absorber and beam outlet, and the radiation shield includes photon shielding and the neutron shield by made by PE by made by Pb.

4. it is according to claim 1 for neutron capture treatment beam-shaping body, it is characterised in that：It is cone-shaped that the slow body is arranged to that two rightabouts adjoin each other.

5. it is according to claim 4 for neutron capture treatment beam-shaping body, it is characterised in that：It is described cone-shaped including the first diameter, Second bobbin diameter and the 3rd diameter, first diameter length is 1cm-20cm, the Second bobbin diameter length is 30cm-100cm, and the 3rd diameter length is 1cm-50cm, and the density of the material of the slow body is the 80%-100% of solid density.

6. it is according to claim 1 for neutron capture treatment beam-shaping body, it is characterised in that：Clearance channel is set between the slow body and the reflector to improve epithermal neutron flux, the material of the slow body is by containing MgF₂Powder and occupy MgF₂Powder weight is 0.1-5%'s⁶LiF powder is mixed.

7. it is according to claim 1 for neutron capture treatment beam-shaping body, it is characterised in that：The powder sintered equipment is hot-press sintering equipment or discharging plasma sintering equipment, and the powder sintering process is hot-pressing sintering technique or discharge plasma sintering process.

8. it is according to claim 7 for neutron capture treatment beam-shaping body, it is characterised in that：The hot-press sintering equipment includes heating furnace, the pressue device being placed in the heating furnace, mould, the powder or powder compact and the control device for controlling the hot-press sintering equipment normal work that load in the mould, and the hot-pressing sintering technique comprises the steps：The mould is filled with appropriate powder or powder compact；The hot pressing furnace is opened with preset pressure and temperature parameter；The movement pressue device pressurizes to the powder in the mould or powder compact；The control device controls the hot-press sintering equipment in the case of normal work；It is powered to sintering in bulk.

9. it is according to claim 7 for neutron capture treatment beam-shaping body, it is characterised in that：The discharging plasma sintering equipment includes first electrode, second electrode, the conductive die being placed between the first electrode and the second electrode, the impulse current generator for providing pulse current to the mould, the pressue device with the pressing means for pressurization and the control device for controlling the pulse current transmitter and the pressue device, at least one of the first electrode and second electrode can be moved, and at least one of the first electrode and second electrode are connected with the pressue device powder being placed in the mould so as to pressurize；The discharge plasma sintering process comprises the steps：Appropriate powder is filled into the mould；The movement second electrode is pressurizeed to the powder in the mould；Impulse current generator is opened so that so as to produce plasma, powder particle surface is activated and generates heat by conductive die conduction by control device；Sintering in bulk.

10. it is according to claim 9 for neutron capture treatment beam-shaping body, it is characterised in that：The discharging plasma sintering equipment further includes the displacement measurement system for measuring the displacement of pressue device, for controlling the atmosphere control system of atmosphere in the mould, for the water-cooling system of cooling, for measuring the temperature measuring equipment of the temperature in the discharging plasma sintering equipment, the discharge plasma sintering process further includes following steps：The control device controls the displacement measurement system to guarantee the displacement measurement system normal work, the control device controls the atmosphere control system to guarantee that atmosphere is in the case of normal work in the mould, the control device controls the water-cooling system to guarantee the water-cooling system normal work, and the control device controls the temperature measuring equipment to guarantee the temperature in the discharging plasma sintering equipment in the case of normal work.