CN107921273A - Beam-shaping body for neutron capture treatment - Google Patents

Abstract

A kind of beam-shaping body for neutron capture treatment, exported including beam entrance, target, the slow body for being adjacent to target, the thermal neutron absorber for being enclosed in slow external reflector, being abutted with slow body, the radiation shield being arranged in beam-shaping body and beam, with the proton beam from the incidence of beam entrance nuclear reaction occurs for target to produce neutron, neutron forms the neutron beam for limiting a main shaft, slow body is by from the neutron degradation that target produces to epithermal neutron energy area, and the material of slow body is by MgF₂It is made or contains MgF₂With occupy MgF₂Percentage by weight be 0.1 5% to contain⁶LiF is mixed, it becomes blocking by powder sintering process through powder sintered equipment by powder or powder compact, the neutron that reflector will deviate from main shaft leads back to main shaft to improve epithermal neutron intensity of beam, for absorbing thermal neutron to avoid multiple dose was caused during treatment with shallow-layer normal structure, radiation shield is used to shield the neutron leaked and photon to reduce the normal tissue dose in non-irradiated area thermal neutron absorber.

Description

Beam-shaping body for neutron capture treatment

Beam-shaping body technique field for neutron capture treatment

The present invention relates to a kind of beam-shaping body more particularly to a kind of beam-shaping bodies for neutron capture treatment.

Background technique

As the radiation cures such as the development of atomics, such as cobalt 60, linear accelerator, electron beam have become one of main means for the treatment of of cancer.However conventional photonic or electronic therapy are limited by radioactive ray physical condition itself, while killing tumour cell, can also be damaged to normal tissue a large amount of in beam approach；Additionally, due to tumour cell to the difference of radioactive ray sensitivity, traditional radiation therapy is for relatively having the malignant tumour of radiation resistance (such as: multirow glioblastoma

(gl ioblastoma multiforme), melanocytoma (melanoma)) treatment effect it is often bad.

In order to reduce the radiation injury of tumour surrounding normal tissue, the target therapy concept in chemotherapy (chemotherapy) is just applied in radiation cure；And it is directed to the tumour cell of radiation resistance, also actively develop the radiation source with high relative biological effect (relative biological effectiveness, RBE), such as the treatment of proton therapeutic, heavy particle therapy, neutron capture at present.Wherein, neutron capture treatment is to combine above two concept, and if boron neutron capture is treated, the specificity by boracic drug in tumour cell is gathered, and accurately neutron beam regulates and controls for cooperation, provides treatment of cancer selection more better than conventional radiation.

Boron neutron capture treatment (Boron Neutron Capture Therapy, BNCT) be using boracic (^WB) drug has the characteristic of high capture cross section to thermal neutron, by a)⁷Li neutron capture and nuclear fission reaction generate⁴He and⁷Two heavy burden charged particle of Li.Referring to Figures 1 and 2, which respectively show boron neutron capture reaction schematic diagram and (!!, a)⁷Li neutron capture nuclear equation formula, the average energy of two charged particles is about 2. 33MeV, (Linear Energy Transfer is shifted with High Linear, LET), short range feature, the linear energy transfer and range of α particle are respectively 150 keV/ μ π κ, 8 μ π ι, and⁷Li heavy burden particle is then 175 keV/ y m, 5 μ π ι, the integrated range of two particle is approximately equivalent to a cell size, therefore the radiation injury for caused by organism can be confined to cell level, it is gathered in tumour cell when boracic drug selectivity, neutron appropriate of arranging in pairs or groups penetrates source, just it can achieve the purpose that tumour cell is killed in part under the premise of normal tissue does not cause too major injury.Because the effect of boron neutron capture treatment depends on tumour cell position boracic drug concentration and thermal neutron quantity, therefore the binary radioactive ray treatment of cancer that is otherwise known as (binary cancer therapy);It follows that neutron penetrates source flux and the improvement of quality occupies key player in the research that boron neutron capture is treated in addition to the exploitation of boracic drug.Summary of the invention

In order to improve the flux and quality that neutron penetrates source, one aspect of the present invention provides a kind of beam-shaping body for neutron capture treatment comprising beam entrance, target, the slow body for being adjacent to target, be enclosed in slow external reflector, with it is slow The adjacent thermal neutron absorber of body, setting are exported in the intracorporal radiation shield of beam-shaping and beam, nuclear reaction occurs for target to generate neutron with the proton beam from beam entrance incidence, neutron forms neutron beam, neutron beam limits a main shaft, slow body is by from the neutron degradation that target generates to epithermal neutron energy area, and the material of slow body is by containing PbF₄、 A1₂0₃、 A1F₃、 0^₂Or MgF₂One of or multiple mixed materials and occupy containing PbF₄、 A1₂0₃、 A1F₃, (or MgF₂One of or the weight percent of multiple mixed materials be that 0. 1-5% containing⁶The material of Li element is mixed, wherein the material of slow body becomes block by powder or powder compact by powder sintering process through powder sintered equipment, the neutron that reflector will deviate from main shaft leads back to main shaft to improve epithermal neutron intensity of beam, thermal neutron absorber caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, radiation shield is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

Another aspect of the present invention provides a kind of beam-shaping body for neutron capture treatment, it includes beam entrance, target, it is adjacent to the slow body of target, it is enclosed in slow external reflector, the adjacent thermal neutron absorber with slow body, setting is exported in the intracorporal radiation shield of beam-shaping and beam, nuclear reaction occurs for target to generate neutron with the proton beam from beam entrance incidence, neutron forms neutron beam, neutron beam limits a main shaft, slow body will be from the neutron degradation that target generates to epithermal neutron energy area, the material of slow body is by containing LiF, Li₂C0₃、 A1₂0₃、 A1F₃、 CaF₂Or MgF₂At least one of material be made, wherein the material of slow body becomes block by powder or powder compact by powder sintering process through powder sintered equipment, the neutron that reflector will deviate from main shaft leads back to main shaft to improve epithermal neutron intensity of beam, thermal neutron absorber caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, radiation shield is used to shield neutron and the photon of leakage 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 for proton beam acceleration, target is made of metal, proton beam accelerates to the energy for being enough to overcome target atom core coulomb repulsion, nuclear reaction occurs to generate neutron with target, beam-shaping physical efficiency 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 greater than 40keV, reflector with the strong material of neutron reflection ability by being made, thermal neutron absorber is made of the material big with thermal neutron action section.

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

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

Further, cone-shaped includes first diameter, second diameter and third diameter, and first diameter length is lcm-20cm, and second diameter length is 30cm-100cm, third diameter length is lcm-50cm, and the density of the material of slow body is the 80%- 100% of theoretical density.

Still further, clearance channel is arranged 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, is placed in the pressurizing device in heating furnace, mold, the powder being packed into mold End or powder compact and the control device worked normally for controlling hot-press sintering equipment, hot-pressing sintering technique include the following steps: with suitable powder or powder compact filling mold；Hot pressing furnace is opened with preset pressure and temperature parameter；Mobile pressurizing device in mold powder or powder compact pressurize；Control device controls hot-press sintering equipment in the case of normal work；It is powered blocking to be sintered.

Preferably as another kind, discharging plasma sintering equipment include first electrode, second electrode, the conductive die being placed between first electrode and second electrode, to mold provide pulse current impulse current generator, the pressurizing device with the pressing means for pressurization and the control device for controlling pulse current transmitter and pressurizing device, at least one of first electrode and second electrode can move, and at least one of first electrode and second electrode are connected so as to the powder being placed in mold that pressurizes with pressurizing device；Discharge plasma sintering process includes the following steps: suitable powder filling mold；Mobile second electrode pressurizes to the powder in mold；Impulse current generator is opened so that conductive die conduction is generated plasma by control device, and powder particle surface is activated and generates heat；It is sintered blocking.

Discharging plasma sintering equipment further comprises the displacement measurement system for measuring the displacement of pressurizing device, for controlling the atmosphere control system of atmosphere in mold, for cooling water-cooling system, for measuring the temperature measuring device of the temperature in discharging plasma sintering equipment, discharge plasma sintering process further comprises following steps: control device command displacement measuring system is to ensure that displacement measurement system works normally, control device controls atmosphere control system to ensure that atmosphere is in the case of normal work in mold, control device controls water-cooling system to ensure that water-cooling system works normally, control device controls temperature measuring device to ensure the temperature in discharging plasma sintering equipment in the case of normal work.

" cylinder " described in the embodiment of the present invention or " bar shape " refer to the structure being basically unchanged along the overall trend of side to its outer profile of the other side in diagram direction, a wherein contour line for outer profile can be line segment, such as the corresponding contour line of cylindrical shape, it is also possible to the biggish circular arc close to line segment of curvature, such as the corresponding contour line of the biggish sphere body shape of curvature, the whole surface of outer profile can be rounding off, it is also possible to non-rounding off, such as many protrusions and groove have been done on the surface of cylindrical shape or the biggish sphere body shape of curvature." cone " described in the embodiment of the present invention or " cone-shaped " refer to the gradually smaller structure of overall trend of side to its outer profile of the other side along diagram direction, a wherein contour line for outer profile can be line segment, such as the corresponding contour line of cone shape, it is also possible to circular arc, such as the corresponding contour line of sphere body shape, the whole surface of outer profile can be rounding off, it is also possible to non-rounding off, has such as done many protrusions and groove on the surface of cone shape or sphere body shape.

Detailed description of the invention

To describe the technical solutions in the embodiments of the present invention more clearly, attached drawing needed in the embodiment of the present invention will be briefly described below, apparently, drawings in the following description are only some embodiments of the invention, for those of ordinary skill in the art, without creative efforts, it is also possible to obtain other drawings based on these drawings.

Fig. 1 is boron neutron capture reaction schematic diagram.

Fig. 2 is (11, α)⁷Li neutron capture nuclear equation formula. 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, wherein slow body is arranged to bicone, and the clearance channel position in first embodiment 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, wherein slow body is arranged to bicone, and the clearance channel position in first embodiment 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, 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, wherein slow body is arranged to cylinder+cone.

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

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

Specific embodiment

Neutron capture treatment as a kind of effective treating cancer means in recent years application gradually increase, wherein with boron neutron capture treat it is most commonly seen, supply boron neutron capture treatment neutron can by nuclear reactor or accelerator supply.The embodiment of the present invention is by taking the treatment of accelerator boron neutron capture as an example, the basic module of accelerator boron neutron capture treatment generally includes accelerator for being accelerated to charged particle (such as proton, deuteron), target and hot removal system and beam-shaping body, charged particle and metal targets effect is wherein accelerated to generate neutron, suitable nuclear reaction is selected according to the characteristics such as required neutron yield rate and the materialization of energy, available acceleration charged particle energy and size of current, metal targets, the nuclear reaction being often discussed has⁷Li (p, n) e and 6, 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 ideal neutron source of boron neutron capture treatment is keV energy grade, if being theoretically only slightly taller than the proton bombardment lithium metal target of threshold values using energy, it can produce the neutron of opposite low energy, clinic can be used for by being not necessary to too many slow processing, however two kinds of targets of lithium metal (Li) and beryllium metal (Be) and the proton-effect section of threshold values energy be not high, to generate sufficiently large neutron flux, the proton of higher-energy is usually selected to cause nuclear reaction.Preferably target should have high neutron yield rate, the neutron energy distribution of generation wears by force the characteristics such as radiation generation, the cheap easily operated and high temperature resistant of safety close to epithermal neutron energy area (will be described in more detail below), without too many, but actually and it can not find and meet required nuclear reaction, using target made of lithium metal in the embodiment of the present invention.But it is well known to those skilled in the art, the material of target can also be made of other metal materials other than the above-mentioned metal material talked about.

Requirement for hot removal system is then different according to the nuclear reaction of selection, such as⁷Li (p, n) e is because of metal targets (lithium metal) Fusing point and thermal conductivity coefficient it is poor, requirement to hot removal system just compared with⁹Be (p, n) is high.It is used in the embodiment of the present invention⁷The nuclear reaction of Li (p, n) e.

No matter boron neutron capture treatment nuclear reaction of the neutron source from nuclear reactor or accelerator charged particle and target, generation is all mixed radiation field, i.e., beam contains neutron, photon of the low energy to high energy；Boron neutron capture treatment for deep tumor, other than epithermal neutron, remaining radiation content is more, causes the ratio of the non-selective dosage deposition of normal tissue bigger, therefore these radiation that will cause unnecessary dosage should reduce as far as possible.In addition to air beam quality factor, the distribution of dosage caused by know more about neutron in human body, Rapid Dose Calculation is carried out using human body head tissue prosthese in the embodiment of the present invention, and will be described in more detail below with prosthese beam quality factor as the design reference of neutron beam.

International Atomic Energy Agency (IAEA) is directed to the neutron source of clinical boron neutron capture treatment, given five air beam quality factor suggestions, this five suggestions can be used for the superiority and inferiority 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 pollution] st 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<electron current and flux ratio epithermal neutron current to flux ratio>0. 7 in 0. 05

Note: subzone is hankered less than 0. 5eV, fast-neutron range is greater than 40keV between 0. 5eV to 40keV in epithermal neutron energy area.

1, epithermal neutron beam flux:

Boracic drug concentration has codetermined the clinical treatment time in neutron beam flux and tumour.If the enough height of tumour boracic drug concentration, the requirement for neutron beam flux can reduce；Conversely, needing high-throughput epithermal neutron if boracic drug concentration is low in tumour to give tumour enough dosage.Requirement of the IAEA for epithermal neutron beam flux is that epithermal neutron number every square centimeter per second is greater than 10⁹, the neutron beam under this flux can substantially control treatment time in one hour for current boracic drug, and short treatment time in addition to advantageous outer to patient's positioning and comfort level, can also relatively efficiently use boracic drug limited residence time in tumour.

2, fast neutron pollutes:

Since fast neutron will cause unnecessary normal tissue dose, regard as pollution, this dosage size and neutron energy be positively correlated, therefore should reduce the content of fast neutron to the greatest extent in neutron beam design.Fast neutron pollution definition is the adjoint fast neutron dosage of unit epithermal neutron flux, and the suggestion that IAEA pollute fast neutron is less than 2 X 10-¹³ Gy-cm²/n o

3, photon contamination (gamma-ray contamination): Gamma-rays, which belongs to, wears by force radiation, the organized dosage deposition of institute on course of the beam can non-selectively be caused, therefore the exclusive requirement that gamma-rays content is also neutron beam design is reduced, gamma-ray contamination defines the gamma-rays dosage adjoint for unit epithermal neutron flux, and IAEA is less than 2 χ 10-to the suggestion of gamma-ray contamination¹³ Gy-cm²/n。

4, thermal and epithermal neutron flux ratio:

Since thermal neutron decay speed is fast, penetration capacity is poor, most of energy is deposited on skin histology after into human body, in addition to the neutron source that the Several Epidermal Tumors such as melanocytoma need to use thermal neutron to treat as boron neutron capture, thermal neutron content should be reduced for deep tumors such as brain tumors.IAEA is less than 0. 05 to thermal and epithermal neutron flux ratio suggestion.

5, middle electron current and flux ratio:

Middle electron current and flux ratio represent the directionality of beam, tropism is good before the bigger expression neutron beam of ratio, normal surrounding tissue dosage caused by the neutron beam of tropism can be reduced because of neutron diverging before height, depth and pendulum pose gesture elasticity can be treated by addition also improving.IAEA centering electron current and flux ratio suggestion are greater than 0. 7.

The dosage in tissue is obtained using prosthese to be distributed, and according to the dose versus depth curve of normal tissue and tumour, pushes away to obtain prosthese beam quality factor.Following three parameter can be used for carrying out the comparison of different neutron beam treatment benefits.

1, effective therapeutic depth:

Tumor dose is equal to the depth of normal tissue maximum dose, the position after this depth, and the dosage that tumour cell obtains is less than normal tissue maximum dose, that is, loses the advantage of boron neutron capture.This parameter represents the penetration capacity of neutron beam, and effective therapeutic depth is bigger to indicate that medicable tumor depth is deeper, unit cm.

2, effective therapeutic depth dosage rate:

That is the tumor dose rate of effective therapeutic depth is also equal to the maximum dose rate of normal tissue.It is the factor for influencing to give tumour accumulated dose size because normal tissue receives accumulated dose, therefore parameter influences the length for the treatment of time, irradiation time needed for tumour doses are given in the bigger expression of effective therapeutic depth dosage rate is shorter, unit cGy/mA-min.

3, dose therapeutically effective ratio:

From brain surface to effective therapeutic depth, tumour and the received mean dose ratio of normal tissue, referred to as dose therapeutically effective ratio；The calculating of mean dose can be integrated to obtain by dose versus depth curve.Dose therapeutically effective ratio is bigger, and the treatment benefit for representing the neutron beam is better.

Compare foundation to there is beam-shaping body in design, in addition to beam quality factor and three above-mentioned parameters in the air of five IAEA suggestion, also utilize the following parameter for showing superiority and inferiority for assessing neutron beam dosage in the embodiment of the present invention:

1, irradiation time 30min (proton current that accelerator uses is 10mA)

2,30. ORBE-Gy can treat depth 7cm 3,60. ORBE-Gy of tumour maximum dose

4,12. 5RBE-Gy of normal cerebral tissue's maximum dose

5,11. 0RBE-Gy of skin maximum dose

Note: RBE (Relative Biological Effectiveness) is relative biological effect, since the biological effect that photon, neutron will cause is different, so dosage item as above is multiplied by the relative biological effect of different tissues respectively in the hope of equivalent dose.

In order to improve the flux and quality that neutron penetrates source, it is the improvement for the beam-shaping body for the treatment of accelerator boron neutron capture preferably as one kind that the embodiment of the present invention, which is the improvement proposed for the beam-shaping body for neutron capture treatment,.As shown in Figure 3, the beam-shaping body 10 for neutron capture treatment in first embodiment of the invention, it includes beam entrance 11, target 12, it is adjacent to the slow body 13 of target 12, the reflector 14 being enclosed in outside slow body 13, the adjacent thermal neutron absorber 15 with slow body 13, radiation shield 16 in beam-shaping body 10 and beam outlet 17 are set, nuclear reaction occurs for target 12 to generate neutron with from the incident proton beam of beam entrance 11, neutron forms neutron beam, neutron beam limits a major axis X, slow body 13 will be from the neutron degradation that target 12 generates to epithermal neutron energy area, the neutron that reflector 14 will deviate from major axis X leads back to major axis X and is penetrated with improving epithermal neutron Beam intensity, clearance channel 18 is set between slow body 13 and reflector 14 to improve epithermal neutron flux, thermal neutron absorber 15 caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, radiation shield 16 is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

The treatment of accelerator boron neutron capture is by accelerator by proton beam acceleration, and as a kind of preferred embodiment, target 12 is made of lithium metal, and proton beam accelerates to the energy for being enough to overcome target atom core coulomb repulsion, occurs with target 12⁷Li (p, n)⁷Be nuclear reaction is to generate neutron.Beam-shaping body 10 can be by neutron slowly to epithermal neutron energy area, and reduce thermal neutron and fast neutron content, slow body 13 is made of the material big with fast neutron action section, epithermal neutron action section is small, and as a kind of preferred embodiment, slow body 13 is by D₂0、 A1F₃、 Fluental™, CaF₂、 Li₂C0₃ 、 MgF₂And A1₂0₃At least one of be made.Reflector 14 with the strong material of neutron reflection ability by being made, and as a kind of preferred embodiment, reflector 14 is made of at least one of Pb or Ni.Thermal neutron absorber 15 is made of the material big with thermal neutron action section, as a kind of preferred embodiment, thermal neutron absorber 15 by⁶Li is made, and is equipped 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 as a kind of preferred embodiment, radiation shield 16 includes the shielding of the photon made of lead (Pb) 161 and the neutron shield 162 made of polyethylene (PE).

Wherein, slow body 13 is arranged to two opposite directions and adjoins each other cone-shaped, as shown in Figure 3 direction, and the left side of slow body 13 is gradually smaller cone-shaped towards left side, to be gradually smaller cone-shaped towards right side, the two adjoins each other on the right side of slow body 13.Preferably the left side of slow body 13 is set as gradually smaller cone-shaped towards left side as a kind of, and right side also can be set into its allothimorph shape with this it is cone-shaped adjoin each other, such as bar shape.Reflector 14 is closely enclosed in slow Around body 13, clearance channel 18 is provided between slow body 13 and reflector 14, so-called clearance channel 18 refers to the empty easy region for allowing neutron beam to pass through of unused solid material covering, as the clearance channel 18 can be set to air duct or vacuum passage.The thermal neutron absorber 15 being arranged close to slow body 13 is by very thin one layer⁶Li material is made, the shielding of the photon made of Pb 161 in radiation shield 16 can be arranged with reflector 14 to be integrated, also fission can be set into, and the neutron shield 162 made of PE can be set in the position of neighbouring beam outlet 17 in radiation shield 16.It is provided with air duct 19 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 setting exports at 17 about lcm apart from beam.It is well known to those skilled in the art, photon shielding 161 can be made of other materials, as long as playing the role of shielding photon, neutron shield 162 can also be made of other materials, also it can be set elsewhere, as long as can satisfy the condition of shielding leakage neutron.

In order to compare the difference of the beam-shaping body and the beam-shaping body of not set clearance channel that are provided with clearance channel, as shown in Fig. 4 and Fig. 5, which respectively show the 3rd embodiments that reflector filling is used by clearance channel 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, it is adjacent to the slow body 23 of target 22, the reflector 24 being enclosed in outside slow body 23, the adjacent thermal neutron absorber 25 with slow body 23, radiation shield 26 in beam-shaping body 20 and beam outlet 27 are set, nuclear reaction occurs for target 22 to generate neutron with from the incident proton beam of beam entrance 21, neutron forms neutron beam, neutron beam limits a major axis X I, slow body 23 will be from the neutron degradation that target 22 generates to epithermal neutron energy area, the neutron that reflector 24 will deviate from major axis X I leads back to major axis X I to improve epithermal neutron intensity of beam, slow body 23 is arranged It adjoins each other at two opposite directions cone-shaped, the left side of slow body 23 is gradually smaller cone-shaped towards left side, the right side of slow body 23 is gradually smaller cone-shaped towards right side, the two adjoins each other, thermal neutron absorber 25 caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, radiation shield 26 is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

Preferably as one kind, target 22, slow body 23, reflector 24, thermal neutron absorber 25 and radiation shield 26 in second embodiment can be identical as in first embodiment, and radiation shield 26 therein includes the shielding of the photon made of lead (Pb) 261 and the neutron shield 262 made of polyethylene (PE), which can be set at beam outlet 27.Air duct 28 is provided between thermal neutron absorber 25 and beam outlet 27.Prosthese B1 setting exports at 27 about lcm apart from beam.

Referring to figure 5., the beam-shaping body 30 includes beam entrance 31, target 32, it is adjacent to the slow body 33 of target 32, the reflector 34 being enclosed in outside slow body 33, the adjacent thermal neutron absorber 35 with slow body 33, radiation shield 36 in beam-shaping body 30 and beam outlet 37 are set, nuclear reaction occurs for target 32 to generate neutron with from the incident proton beam of beam entrance 31, neutron forms neutron beam, neutron beam limits a major axis X 2, slow body 33 will be from the neutron degradation that target 32 generates to epithermal neutron energy area, the neutron that reflector 34 will deviate from major axis X 2 leads back to major axis X 2 to improve epithermal neutron intensity of beam, slow body 33 is arranged to two A opposite direction adjoins each other cone-shaped, and the left side of slow body 33 is gradually smaller towards left side It is cone-shaped, the right side of slow body 33 is gradually smaller cone-shaped towards right side, the two adjoins each other, thermal neutron absorber 35 caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, radiation shield 36 is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

Preferably as one kind, target 32, slow body 33, reflector 34, thermal neutron absorber 35 and radiation shield 36 in 3rd embodiment can be identical as in first embodiment, and radiation shield 36 therein includes the shielding of the photon made of lead (Pb) 361 and the neutron shield 362 made of polyethylene (PE), which can be set at beam outlet 37.Air duct 38 is provided between thermal neutron absorber 35 and beam outlet 37.Prosthese B2 setting exports at 37 about 1cm apart from beam.

The simulation of these three embodiments is calculated using MCNP software (being the neutron being used to calculate in 3 D complex geometry based on Monte Carlo method, photon, charged particle or the coupling neutron/photon/charged particle transport problem common software packet by Los Alamos National Laboratories, the U.S. (LosAlamos National Laboratory) exploitation) below:

Wherein, as following table one shows performance (in table each name lexeme same as above, details are not described herein, similarly hereinafter) of the beam quality factor in these three embodiments in air:

Table one: beam quality factor in air

Wherein, performance in these three embodiments is shown as following table two shows dosage:

Table two: dosage performance

Dosage shows slow body filling clearance channel reflector and fills 10. 9 10. 9 11. 0 effective therapeutic depth dosage rate 4. 47 4. 60 4. 78 of clearance channel clearance channel effective therapeutic depth

Dose therapeutically effective is than 5. 66 5. 69 5. 68 Wherein, as following table three shows simulation value of the parameter of assessment neutron beam dosage performance superiority and inferiority in these three embodiments: table three: the parameter of assessment neutron beam dosage performance superiority and inferiority

Note: it can be learnt from three above-mentioned tables: be provided with the beam-shaping body of clearance channel between slow body and reflector, the treatment benefit of neutron beam is best.

Since the neutron generated 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 generated to neutron and slow body before making, and lateral neutron can reach beam outlet through less collision, it then should theoretically can reach neutron slowly to optimize, efficient raising epithermal neutron flux.Set about below from the geometry of beam-shaping body, to evaluate influence of the geometry of different beam-shaping bodies for epithermal neutron flux.

As shown in Figure 7, it illustrates the geometries of the beam-shaping body in fourth embodiment, the beam-shaping body 40 includes beam entrance 41, target 42, it is adjacent to the slow body 43 of target 42, the reflector 44 being enclosed in outside slow body 43, the adjacent thermal neutron absorber 45 with slow body 43, radiation shield 46 in beam-shaping body 40 and beam outlet 47 are set, nuclear reaction occurs for target 42 to generate neutron with from the incident proton beam of beam entrance 41, slow body 43 will be from the neutron degradation that target 42 generates to epithermal neutron energy area, the neutron that reflector 44 will deviate from is led back to improve epithermal neutron intensity of beam, slow body 43 is arranged to bar shape, preferably, It is arranged to cylindrical shape, multi-dose was caused with shallow-layer normal tissue when thermal neutron absorber 45 is for absorbing thermal neutron to avoid treatment, radiation shield 46 is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area, is provided with air duct 48 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 include beam entrance 51, target 52, the slow body 53 for being adjacent to target 52, the reflector 54 being enclosed in outside slow body 53, with it is slow The adjacent thermal neutron absorber 55 of body 53, radiation shield 56 in beam-shaping body 50 and beam outlet 57 are set, nuclear reaction occurs for target 52 to generate neutron with from the incident proton beam of beam entrance 51, neutron forms neutron beam, neutron beam limits a major axis X 3, slow body 53 will be from the neutron degradation that target 52 generates to epithermal neutron energy area, the neutron that reflector 54 will deviate from major axis X 3 leads back to major axis X 3 to improve epithermal neutron intensity of beam, slow body 53 be arranged to two opposite directions adjoin each other it is cone-shaped, the left side of slow body 53 is bar shape, the right side of slow body 53 is gradually smaller cone-shaped towards right side, the two adjoins each other, thermal neutron absorber 25 is for inhaling Thermal neutron is received to avoid multi-dose was caused when treatment with shallow-layer normal tissue, radiation shield 26 is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

Preferably as one kind, target 52, slow body 53, reflector 54, thermal neutron absorber 55 and radiation shield 56 in 5th embodiment can be identical as in first embodiment, and radiation shield 56 therein includes the shielding of the photon made of lead (Pb) 561 and the neutron shield 562 made of polyethylene (PE), which can be set at beam outlet 57.Air duct 58 is provided between thermal neutron absorber 55 and beam outlet 57.Prosthese B3 setting exports at 57 about 1cm apart from beam.

Cylinder+cone simulation in the slow body of the cylinder in the slow body of bicone in second embodiment, fourth embodiment and the 5th embodiment is calculated using MCNP software 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, performance in these three embodiments is shown as following table five shows dosage:

Table five: dosage performance

Dosage shows cylinder cylinder+cone bicone

Effective therapeutic depth 11. 8 10. 9 10. 9 2. 95 4. 28 4. 47 dose therapeutically effective of effective therapeutic depth dosage rate is than 5. 52 5. 66 5. 66

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

Note: it can be learnt from three above-mentioned tables: slow body is arranged to at least one is cone-shaped, and the treatment benefit of neutron beam is preferable.

" cylinder " described in the embodiment of the present invention or " bar shape " refer to the structure being basically unchanged along the overall trend of side to its outer profile of the other side in diagram direction, a wherein contour line for outer profile can be line segment, such as the corresponding contour line of cylindrical shape, it is also possible to the biggish circular arc close to line segment of curvature, such as the corresponding contour line of the biggish sphere body shape of curvature, the whole surface of outer profile can be rounding off, it is also possible to non-rounding off, such as many protrusions and groove have been done on the surface of cylindrical shape or the biggish sphere body shape of curvature.

" cone " described in the embodiment of the present invention or " cone-shaped " refer to the gradually smaller structure of overall trend of side to its outer profile of the other side along diagram direction, a wherein contour line for outer profile can be line segment, such as the corresponding contour line of cone shape, it is also possible to circular arc, such as the corresponding contour line of sphere body shape, the whole surface of outer profile can be rounding off, it is also possible to non-rounding off, has such as done many protrusions and groove 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 attached drawing 3 as an example, be further described to slow body 13.

Slow body 13 shows the antipodal double cone structures in two cone directions, and the material of slow body 13 is by containing 41 or CaF₂Or MgF₂At least one of material be made, slow body 13 have first diameter D1, second diameter D2 and third diameter D3.Opening is provided at first diameter D1 to accommodate target 12, second diameter D2 is set as at the full-size of double cone structures.For BNCT, in order to reach enough slow speed effect, first diameter D1 length is lcm-20cm, second diameter D2 length is 30cm-100cm, and third diameter D3 length is lcm-50cm, preferably as one kind, first diameter D1 length is 10cm Second diameter D2 length is 70cm, and third diameter D3 length is 30cm.Such large-sized slow body 13 in order to obtain, and the density of its material is the 80%-100% of theoretical density, provides the preparation of following three kinds slow body materials.

1 is long brilliant

First with MgF₂For, with further reference to application for a patent for invention Publication No. CN102925963A, it is incorporated herein in its entirety the reference as long brilliant preparation.As long brilliant mode, usually by kind of crystalline substance and contain MgF₂Powder be put into crucible, MgF is grown by certain mode₂Monocrystalline.

It needs to give special heed to, so-called " monocrystalline " refers to the molding single crystal of single growth here, and is not single crystal grain (there was only a kind of crystalline form and contain only a crystal grain, molecule, courtyard are all to arrange regularly in the crystal grain).Be best understood from be this single crystal grain from multiple crystal grain (size and shape of i.e. each crystal grain is different, and be orientated be also it is in disorder, without apparent shape, also do not show anisotropy) it is corresponding.Below with respect to " monocrystalline " definition with it is where like.

By investigation, PbF₄、 A1F₃、 CaF n Al₂0₃It can also be prepared by similar mode.

2. powder sintered

By ^^ or 1 or CaF₂Powder or powder compact further combined with getting up, during the sintering process powder particle to occur mutually to flow, diffusion, dissolution, the physical and chemical processes such as recrystallization, keep powder further fine and close, eliminate some or all of holes.Sintering processing can there are many kinds of, such as solid-phase sintering, i.e., sintering temperature is in body of powder below the fusing point of each constituent element；Liquid-phase sintering, i.e., if there is two or more constituent elements in 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 when sintering；Hot pressed sintering applies pressure to body of powder, to promote its densification process, hot pressing is the forming and sinter bonded powder, directly obtains the technical process of product that is, in sintering；Discharge plasma sintering, it is added on powder sample by the ON-OFF DC pulse voltage that particular power source control device occurs, other than can be using sintering facilitation (discharge impact pressure and Joule heating) caused by usual electro-discharge machining, the Fast Sintering technology that sintering facilitation caused by the Spark Discharges (moment generates high-temperature plasma) generated between pulsed discharge initial stage powder realizes densification by TRANSIENT HIGH TEMPERATURE field be also efficiently used.The material of slow body becomes block by powder or powder compact by powder sintering process through powder sintered equipment.

Well known to those skilled in the art, other sintering processings can also realize 1^ or 41 or CaF₂At least one of or preparation of several mixtures as the material of slow body.As it is a kind of preferably, hereafter using hot pressed sintering and discharge plasma sintering as powder sintered embodiment.

Again with 1^ powder or MgF₂Addition accounts for MgF₂0. 1-5%'s of powder weight⁶For the mixed-powder of LiF, to carry out powder sintered introduction, it is preferable that below with MgF₂Addition accounts for MgF₂0. 1-5%'s of powder weight⁶Powder sintered introduction is carried out for the mixed-powder of LiF.

Slow body plays particularly important role in beam-shaping body, is responsible for the slow heavy responsibility of neutron and appoints greatly, needs to the greatest extent Fast neutron intensity is possibly lowered, and excessively slowly cannot be thermal neutron by neutron, on the other hand, it is also necessary to lower the gamma-rays derived in moderating process.Research has shown that equably inserting a small amount of contain 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 MgF₂0. 1-5%'s of powder weight⁶The powder of LiF mixes, compared to being individually not added with⁶The MgF of LiF powder₂Powder, the mixed-powder can be more efficiently absorbed thermal neutron and effectively inhibit gamma-rays.By MgF₂Powder doping accounts for MgF₂0. 1-5%'s of powder weight contains⁶The material mixing of Li is used as a kind of slow body material, and well known to those skilled in the art, this contains⁶The material of Li can be any be easy to and MgF₂Any physical form of powder doping together, as this contains⁶The material of Li can be liquid, be also possible to powder.This contains⁶The material of Li can be any be easy to and MgF₂Any compound of powder doping together, this contains⁶The material of Li can be⁶LiF or⁶Li₂C0₃.Preferably as one kind, by MgF₂Powder and account for MgF₂0. 1-5%'s of powder weight⁶The powder or powder compact of LiF further combined with getting up, during the sintering process powder particle to occur mutually to flow, diffusion, dissolution, the physical and chemical processes such as recrystallization, keep powder further fine and close, eliminate some or all of holes.Sintering processing can there are many kinds of, such as solid-phase sintering, i.e., sintering temperature is in body of powder below the fusing point of each constituent element；Liquid-phase sintering, i.e., if there is two or more constituent elements in 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 when sintering；Hot pressed sintering applies pressure to body of powder, to promote its densification process, hot pressing is the forming and sinter bonded powder, directly obtains the technical process of product that is, in sintering；Discharge plasma sintering, it is added on powder sample by the ON-OFF DC pulse voltage that particular power source control device occurs, other than can be using sintering facilitation (discharge impact pressure and Joule heating) caused by usual electro-discharge machining, the Fast Sintering technology that sintering facilitation caused by the Spark Discharges (moment generates high-temperature plasma) generated between pulsed discharge initial stage powder realizes densification by TRANSIENT HIGH TEMPERATURE field be also efficiently used.The material of slow body becomes block by powder or powder compact by powder sintering process through powder sintered equipment.

Well known to those skilled in the art, other sintering processings can also realize 1^ or 41 or or PbF₄At least one of or several mixtures add again⁶Preparation of the powder of LiF as the material of slow body.As it is a kind of 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 are integrated, the consistency that heating rate is fast, sintering time is short, sintering temperature is low, crystal grain is uniform, is conducive to control the fine structure of sintered body, obtains material is high, and have the advantages that easy to operate, reproducibility is high, it is safe and reliable, save space, save the energy and at low cost.Discharge plasma sintering is added between powder particle due to Impulsive Current, there are the positive and negative anodes of electric field induction between powder particle, it discharges between particle under pulse current effect, excite plasma, the intergranular contact portion of energetic particle hits generated by electric discharge, substance is set to generate evaporation and play purification and activation, in the dielectric layer of cluster of grains, intermittent repid discharge occurs power storage for dielectric layer.Since there are pulse currents between powder or powder compact, and pulse current is moment, interrupted, high-frequency generation, in powder particle not in contact with the position heat discharge generated and the Joule heat of powder particle contact site generation, powder particle is all greatly facilitated The diffusion of atom, diffusion coefficient is than much greater under usual hot pressing condition, to reach powder sintered rapid.Furthermore due to the addition of pulse current, it fast move electric discharge position and joule heat position in powder all can, the sintering of powder or powder compact enable to homogenize.During discharge plasma sintering, when discharging between particle, the localized hyperthermia of up to thousands of degree to 10,000 degree can instantaneously be generated, cause to evaporate and melt in particle surface, neck is formed in grain contact point, since heat is transmitted to particle surface from fever center immediately and spreads around, neck is quickly cooled down and makes vapour pressure lower than other positions.Gaseous substance condenses upon neck and forms another important feature that the evaporation higher than ordinary sinter method-solidification transmitting is discharge plasma sintering process.Crystal grain is by the effect of Current Heating and vertical uniaxial pressure, and body is spread, grain boundary decision is all strengthened, and accelerates sintering densification process, therefore the sintered body of high quality can be obtained with lower temperature and shorter time.Discharge plasma sintering process can be regarded as the result of particle electric discharge, conductive heater and comprehensive function of pressurizeing.

Fig. 9 is please referred to, there is disclosed a kind of schematic diagrames of discharging plasma sintering equipment.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 mold 103, with the pressing means 1051 for pressurization, 1052 pressurizing device 105 and control device 106 for controlling impulse current generator 104 and pressurizing device 105, at least one of first electrode 101 and second electrode 102 can move, pressing means 1051, at least one of 1052 can move, preferably as one kind, first electrode 101 and pressing means 1051 are fixed, second electrode 1 02 and pressing means 1052 can move, so as to the powder being placed in mold 103 or the powder compact 107 of pressurizeing.Preferably as one kind, conductive die 103 is set as lead or graphite.Discharging plasma sintering equipment 100 further comprises the displacement measurement system 108 for measuring the displacement of pressurizing device 105, for controlling the atmosphere control system 109 of atmosphere in the mold 103, the water-cooling system 111 cooled down for controlling water-cooled vacuum room 110, for measuring the temperature measuring device 112 of the temperature in discharging plasma sintering equipment 100.Mold 103 and the logical upper pulse current of powder or powder compact 107, other than offer discharge impact pressure and Joule heat are sintered, Fast Sintering is further realized by TRANSIENT HIGH TEMPERATURE field using sintering facilitation caused by the Spark Discharges (moment generates high-temperature plasma) generated between pulsed discharge initial stage powder, so that powder or powder compact 107 become blocky from pulverulence, so-called bulk is integrally formed, without such as long brilliant mode, it is spliced by monocrystalline by the processes such as polishing or polishing and is suitble to slow body size.

The discharging plasma sintering equipment 100 is sintered and pressurizes using DC pulse current direct-electrifying, controls heating rate and sintering temperature by adjusting the size of pulsed direct current through control device 106.Entire sintering process can carry out under vacuum conditions, can also carry out in protective atmosphere, such as oxygen or hydrogen.

Under oxygen atmosphere, since oxygen is sintered object adsorption or chemical reaction effect occurs, plane of crystal is set to form the non-stoichiometric compound of cation omission type, cation vacancy increases, make the oxygen in closed pore that can be directly entered lattice simultaneously, and be diffused as oxygen ion vacancy along surface, spread and be sintered acceleration.When sintering is controlled by positive diffusions, oxidizing atmosphere or partial pressure of oxygen are higher and be conducive to cation vacancy and formed, acceleration of sintering；When spreading control by anion, reducing atmosphere or lower partial pressure of oxygen will lead to oxygen ion vacancy and generate simultaneously acceleration of sintering.

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

Sintering temperature is crucial an one of parameter during plasma Fast Sintering.The determination of sintering temperature will consider sintered body Sample phase transition at high temperature, the growth rate of crystal grain, the quality requirement of sample and sample density requirements.Under normal circumstances, with the raising of sintering temperature, sample consistency is integrally in rising trend, this illustrates that sintering temperature has apparent influence to sample consistency degree, sintering temperature is higher, and mass transfer speed is faster in sintering process, and the sample the easy to be closely knit.

But temperature is higher, the growth rate of crystal grain is faster, and 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.

Extend the soaking time under sintering temperature, generally can all complete acceleration of sintering to some extent, improve the microstructure of sample, this is more obvious to the sintering of VISCOUS FLOW mechanism, and influences on the sintering of bulk diffusion and surface diffusion mechanism smaller.During the sintering process, general heat preservation only 1 minute when, the density of sample just reaches 96.5% or more of theoretical density, with the extension of soaking time, the consistency of sample increases, but variation range is not very greatly, to illustrate although soaking time has a certain impact to the consistency of sample, but function and effect are not apparent.But unreasonably extend the soaking time under sintering temperature, crystal grain in this time, grow up by play of having to go to the toilet, and 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 soaking 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 inhibit growing up for crystal grain, obtain fine grain ceramics of uniform size, moreover it is possible to save time, utilization rate that is energy saving and improving agglomerating plant.But due to the limitation of equipment itself, heating rate is too fast to will cause damaging influence to equipment.Therefore the quickening heating rate in permissible range as far as possible.But reflects in the experimental data of actual measurement and arrive.It is different from sintering temperature and soaking time, influence of the heating rate to sample consistency shows opposite result, i.e. with the increase of heating rate, the trend that the performance roughening of sample consistency is gradually reduced, there is scholar to propose this is because the raising of heating rate is equivalent to and shortens soaking time near sintering temperature, thus sample consistency can be declined.In actual high-temperature sintering process, temperature-rise period is generally divided into three phases, and respectively from room temperature to 600 °C or so, 600 °C to 900 °C or so, 900 to sintering temperature: the first stage is the preparation 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 (°C/min)_;Phase III is the buffer stage of heating, which is slowly increased to sintering temperature, and soaking time is usually 1 ~ 7 minute, and furnace cooling after heat preservation, cooling rate is up to 300 °C/min.

Powder carries out compression moulding and sintering immediately after being substantially discharged processing.Serious plastic deformation occurs under the collective effect of resistance Joule heat and pressure for agglomerated material, and application forming pressure is conducive to enhance residual gas, raising product intensity, density and its surface smoothness that contact, increase sintering area, discharge between powder particle are sintered between powder.The size of forming pressure is generally determined according to the compressibility of sintering powder and the requirement to performances such as density of sintered material, intensity, generally within the scope of 15 30 MPa, there may come a time when up to 50 MPa, even higher.In general, forming pressure is bigger, the density of agglomerated material is higher.The pressurization duration also has a great impact to density of sintered material, type, the geometric dimension of powder size and institute's agglomerated material of suitable pressing time view agglomerated material and it is different, need to be determined by experiment.It is demonstrated experimentally that the pressurization duration is equal to or slightly greater than discharge time, this is the necessary condition for obtaining most high-density agglomerated material.It is readily appreciated that pressure is bigger from sintering and solid phase reaction mechanism, particle packing is closer in sample, and mutual contact point and contact area increase sintering are accelerated.Sample can be made to obtain better consistency in this way, and crystal grain can effectively be inhibited to grow up and reduce sintering temperature.Therefore the pressure of selection is generally 30 ~ 50Mpa.But with studies have shown that the consistency difference of sample is simultaneously little when being sintered, external pressure is 30Mpa and 50Mpa, this illustrates that the phenomenon that consistency increases with pressure is more obvious only within a certain range. Discharge plasma sintering has the advantage that sintering velocity is fast compared to conventional sintering technique；It improves material microstructure and improves the performance of material.

Well known to those skilled in the art, mold can be used other conductive materials and be made, and it is fixed that two electrodes also can be set into discharging plasma sintering equipment, and only at least one pressing means can move.

The technical process of discharge plasma sintering is divided into four-stage.First stage: apply initial pressure to powder sample, make to come into full contact between powder particle, to be then able to generate uniform and sufficient plasma discharging in powder sample；Second stage: applying pulse current, and under the action of pulse current, powder particle contact point generates plasma discharging, and particle surface generates micro- exothermic phenomenon due to activation；Phase III: closing the pulse power, carries out resistance heating to sample, until reaching scheduled sintering temperature and sample contraction completely；Fourth stage: release.Rationally the main technologic parameters such as control initial pressure, sintering time, forming pressure, pressurization duration, sintering temperature, heating rate can get the good material of comprehensive performance.

Due to the arch bridge effect between powder particle, they cannot generally come into full contact with, therefore, the plasma uniformly and being substantially discharged is generated when in order to make electric spark sintering in sample, farthest activated particle surface is to accelerate sintering densification process, it needs to apply initial pressure appropriate to sintering powder, comes into full contact with powder particle.The size of initial pressure can with sintering powder kind, sintered part size and performance difference.First pressing is too small, and electric discharge phenomena are confined in amount of powder, leads to powder local melting；Pressure is excessive, it will inhibits electric discharge, and then delays to be sintered diffusion process.According to existing literature, it is sufficiently carried out to continue electric discharge, this initial pressure is generally no more than 10MPa.

When powdered sample preferable with electric spark sintering electric conductivity, due to resistance heating outwardly and inwardly carrying out simultaneously from sample, sintering time is extremely short, even moment, but sintering time length should regard powder quality, kind and performance and difference, generally several seconds to a few minutes；When sintering is large-scale, refractory metal powder material when, even up to dozens of minutes.Sintering time is affected to product density, to enable densification process sufficiently to carry out, therefore, to assure that certain sintering time.

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

Preferably as one kind, discharge plasma sintering process includes the following steps: to fill mold 103 with suitable powder or powder compact 107;Mobile pressurizing device 105 in mold 103 powder or powder compact 107 pressurize；Impulse current generator 104 is opened so that mold 103 is conductive to generate plasma by control device 106, and powder particle surface is activated and generates heat；It is sintered blocking.Discharge plasma sintering process further comprises following steps: 106 command displacement measuring system 108 of control device is to ensure that displacement measurement system 108 works normally, control device 106 controls atmosphere control system 109 to ensure the atmosphere in mold 103 in the case of normal work, control device 106 controls water-cooling system 111 to ensure it in the case of normal work, and control device 106 controls temperature measuring device 112 to ensure the temperature in discharging plasma sintering equipment 100 in the case of normal work.So-called normal work refers to that the alarm signals such as the vision, tactile or the sense of hearing of human perception do not occur for discharging plasma sintering equipment, and if alarm lamp lights, alarm lamp sounds, and police instruction vibration etc. is such.

2. 2 hot pressed sinterings

Hot pressed sintering is that dry powder is filled into model, then heats from uniaxial direction in pressurization, makes to form and be sintered simultaneously A kind of sintering method completed.Hot pressing and sintering technique production technology very abundant is classified at present without unified standard and standard.Vacuum hotpressing, atmosphere hot pressing, vibration hot pressing, balanced hot pressing, hot isostatic pressing, reaction hot-pressing and ultra-high pressure sintering can be divided into according to status.Hot pressed sintering is due to heating pressurization while carrying out, and powder is in hot plastic state, facilitates the contact diffusion of particle, flows the progress of mass transport process, thus briquetting pressure is only 1/10 be cold-pressed;It can also reduce sintering temperature, shorten sintering time, grow up to resist crystal grain, obtain that crystal grain is tiny, consistency is high and mechanical, the good product of electric property.

In order to prepare slow body material using hot-pressing sintering technique, Figure 10 is please referred to, hot-press sintering equipment 200 is mainly including heating furnace 201, the pressurizing device 202 being placed in heating furnace 201, mold 203, the powder being packed into mold 203 or powder compact 204 and control device 205.Heating furnace 201 is usually using electricity as heat source, and heating element is by SiC, MoSi or nickel reeling, platinum wire, molybdenum filament etc..Pressurizing device 202 requires that speed is gentle, pressure maintaining is constant, pressure flexible modulation, generally there is lever and fluid pressure type.According to the requirement of material properties, pressure atmosphere can be air and be also possible to reducing atmosphere or inert atmosphere.Mold 203 requires high intensity, high temperature resistant, anti-oxidant and do not cohere with hot-pressed material, and 203 thermal expansion coefficient of mold should be consistent or approximate with hot-pressed material, as it is a kind of preferably, using graphite jig in the present embodiment.Control device 205 makes hot-press sintering equipment 200 in the case of normal work.So-called normal work refers to that the alarm signals such as the vision, tactile or the sense of hearing of human perception do not occur for discharging plasma sintering equipment, and if alarm lamp lights, alarm lamp sounds, and police instruction vibration etc. is such.

With MgF₂For preparing the slow body of target using hot-pressing sintering technique, the technological process of production generally comprises following steps, MgF₂Raw material prepares raw material grinding, screening process is transferred to the cooling grinding of coming out of the stove of the cooling hot isostatic pressing high temperature sintering of coming out of the stove of mold high temperature sintering high temperature hot pressing sintering, polishing, bonding finished product.

As a kind of processing step that the powder processing step and postorder sintering for preferably, omitting preamble herein are completed.Hot-pressing sintering technique includes the following steps: to fill mold 203 with suitable powder or powder compact 204;Hot pressing furnace 201 is opened with preset pressure and temperature parameter；Mobile pressurizing device 202 in mold 203 powder or powder compact 204 pressurize；Control device 205 controls hot-press sintering equipment 200 in the case of normal work；It is powered blocking to be sintered.

It should be further noted that, in hot-pressing sintering technique step " mobile pressurizing device 202 in mold 203 powder or powder compact 204 pressurize " can be used as precharge, synchronous with energization can also carry out, i.e., by step " mobile pressurizing device 202 in mold 203 powder or powder compact 204 pressurize " and step " being powered blocking to be sintered " be combined into one.

Some parameters that long brilliant, discharge plasma sintering and hot pressed sintering are listed in following table compare, material as the slow body application in a kind of beam-shaping body of the neutron capture disclosed in the present invention treatment of being more convenient for, under the precondition for especially needing to manufacture the size that second diameter D2 maximum reaches 100cm, it is recommended here that using powder sintered manufactured slow body material, it is specific to be described in detail see hereafter.

Table seven: long brilliant and powder sintering process comparison

Process materials scale time cost process difficulty

MgF₂5,000,000 yuan or so of or so monocrystalline 10- 20cm (maximum gauge) half a year is more difficult to be said

Say A1F₃5,000,000 yuan or so of or so monocrystalline 10- 20cm (maximum gauge) half a year is more difficult

CaF₂5,000,000 yuan or so more difficult plasma discharging MgF of or so monocrystalline 10- 20cm (maximum gauge) half a year₂Need be easier to or so January 500,000 or so by actual size It is sintered A1F₃Need be easier to or so January 500,000 or so by actual size

CaF₂Need be easier to or so January 500,000 or so by actual size

MgF₂Need be easier to vacuum heating-press sintering A1F within 2 months or so 1,000,000 or so by actual size₃Need be easier within 2 months or so 1,000,000 or so by actual size

CaF₂Need be easier within 2 months or so 1,000,000 or so by actual size

MgF₂Need 2-2. May 500,000 or so by actual size and be easier to HIP sintering AIF3 to need be easier to 2-2. May 500,000 or so by actual size

CaF₂Need be easier to note 2-2. May 500,000 or so by actual size: the 6LiF powder of 0. 1-5% respectively added is omitted as powder main material for upper table, though MgF is only listed in upper table₂+LiF、 AlF₃+ LiF and CaF₂These three slow body materials of+LiF are compared using the parameter of technique as above, but well known to those skilled in the art, other slow body material such as Al₂0₃+ LiF can also easily make comparison.

It can be learnt from upper table, although the density for preparing slow body material by the way of long crystalline substance can reach close to theoretical density, such as reach the 99. 99% of theoretical density, but since single crystal size is smaller, it needs to be spliced by many monocrystalline to reach the large-sized slow body material of target, it it may also be desirable to that it is carried out the other processes such as to mirror-finish in the process, it is not only time-consuming very long, and also cost and technology difficulty are all very big.

The density that slow body material is prepared by the way of powder sintered can also reach the 80%-100% of theoretical density.Preferably as one kind, the density of slow body material reaches the 99. 99% of theoretical density.Theoretical density compared with the theoretical density for the slow body material that long crystal type obtains substantially it is indiscriminate simultaneously, it is with the obvious advantage in terms of the size of acquisition, time, cost and technology difficulty.It is obtained as required using slow its actual size of body material that discharge plasma sintering is prepared, a kind of mode can customize out the mold of suitable needs, another way uses common die, such as the mold of diameter 70cm* thickness 2cm, then splice and can complete by several, cost and technology difficulty with vacuum heating-press sintering and equally matched HIP sintering under the premise of, 1 month or so time is only needed on manufacturing time.

The above description is merely a specific embodiment, and the beam-shaping body for neutron capture treatment that the present invention discloses is not limited to structure represented by content described in above embodiments and attached drawing.The anyone skilled in the art material and shape to wherein component and position are made on the basis of the present invention apparently change, substitution or modification, all within the scope of protection of present invention.Therefore, protection scope of the present invention should be subject to the protection scope in claims.

Claims (1)

1. Claims

   , a kind of beam-shaping body for neutron capture treatment, it is characterized by: the beam-shaping body includes beam entrance, target, it is adjacent to the slow body of the target, it is enclosed in the slow external reflector, the adjacent thermal neutron absorber with the slow body, setting is exported in the intracorporal radiation shield of the beam-shaping and beam, nuclear reaction occurs for the target to generate neutron with the proton beam from the beam entrance incidence, the neutron forms neutron beam, the neutron beam limits a main shaft, the slow body will be from the neutron degradation that the target generates to epithermal neutron energy area, the material of the slow body is by containing PbF₄、 A1₂0₃、 A1F₃, & or MgF₂One of or multiple mixed materials and occupy and described contain PbF₄、 A1₂0₃、 A1F₃、 CaF₂Or MgF₂One of or the weight percent of multiple mixed materials be that 0. 1-5% containing⁶The material of Li element is mixed, wherein the material of the slow body becomes block by powder or powder compact by powder sintering process through powder sintered equipment, the neutron that the reflector will deviate from the main shaft leads back to the main shaft to improve epithermal neutron intensity of beam, the thermal neutron absorber caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, the radiation shield is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

   , a kind of beam-shaping body for neutron capture treatment, it is characterized by: the beam-shaping body includes beam entrance, target, it is adjacent to the slow body of the target, it is enclosed in the slow external reflector, the adjacent thermal neutron absorber with the slow body, setting is exported in the intracorporal radiation shield of the beam-shaping and beam, nuclear reaction occurs for the target to generate neutron with the proton beam from the beam entrance incidence, the neutron forms neutron beam, the neutron beam limits a main shaft, the slow body will be from the neutron degradation that the target generates to epithermal neutron energy area, the material of the slow body is by containing LiF, Li₂C0₃、 A1₂0₃、 A1F₃, (or at least one of ^^ material is made, wherein the material of the slow body becomes block by powder or powder compact by powder sintering process through powder sintered equipment, the neutron that the reflector will deviate from the main shaft leads back to the main shaft to improve epithermal neutron intensity of beam, the thermal neutron absorber caused multi-dose for absorbing thermal neutron with shallow-layer normal tissue when treatment, the radiation shield is used to shield neutron and the photon of leakage to reduce the normal tissue dose in non-irradiated area.

   , beam-shaping body according to claim 1 or 2 for neutron capture treatment, it is characterized by: 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 for proton beam acceleration, the target is made of metal, the proton beam accelerates to the energy for being enough to overcome target atom core coulomb repulsion, nuclear reaction occurs to generate neutron with the target, the beam-shaping physical efficiency 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, it is described to hanker subzone less than 0. 5eV, the fast-neutron range is greater than 40keV, the reflector is by strong with neutron reflection ability Material be made, the thermal neutron absorber is made of the material big with thermal neutron action section.

   , it is according to claim 3 for neutron capture treatment beam-shaping body, it is characterised in that: the reflector is made of at least one of Pb or Ni, the thermal neutron absorber by⁶Li is made, and air duct is equipped between the thermal neutron absorber and beam outlet, and the radiation shield includes the shielding of the photon made of Pb and the neutron shield made of PE., it is according to claim 1 or 2 for neutron capture treatment beam-shaping body, it is characterised in that: the slow body be arranged to two opposite directions adjoin each other it is cone-shaped.

   , the beam-shaping body according to claim 5 for neutron capture treatment, it is characterised in that: it is described it is cone-shaped include first diameter, second diameter and third diameter, the first diameter length is lcm-20cm, and the second diameter length is 30cm-100cm, the third diameter length are lcm-50cm, and the density of the material of the slow body is the 80%- 100% of theoretical density.

   , it is according to claim 1 or 2 for neutron capture treatment beam-shaping body, it is characterised in that: between the slow body and the reflector be arranged clearance channel to improve epithermal neutron flux.

   , it is according to claim 1 or 2 for neutron capture treatment beam-shaping body, it is characterized by: the powder sintered equipment is hot-press sintering equipment or discharging plasma sintering equipment, the powder sintering process is hot-pressing sintering technique or discharge plasma sintering process.

   , it is according to claim 8 for neutron capture treatment beam-shaping body, it is characterized by: the control device that the hot-press sintering equipment includes heating furnace, the pressurizing device being placed in the heating furnace, mold, the powder being packed into the mold or powder compact and works normally for controlling the hot-press sintering equipment, the hot-pressing sintering technique includes the following steps: to fill the mold with suitable powder or powder compact；The hot pressing furnace is opened with preset pressure and temperature parameter；The mobile pressurizing device in the mold powder or powder compact pressurize；The control device controls the hot-press sintering equipment in the case of normal work；It is powered blocking to be sintered.

   0, beam-shaping body according to claim 8 for neutron capture treatment, it is characterized by: 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 of pulse current is provided to the mold, pressurizing device with the pressing means for pressurization and the control device for controlling the pulse current transmitter and the pressurizing device, at least one of the first electrode and second electrode can move, at least one of the first electrode and second electrode are connected so as to the powder being placed in the mold that pressurizes with the pressurizing device；The discharge plasma sintering process includes the following steps: suitable powder filling the mold；The mobile second electrode pressurizes to the powder in the mold；Impulse current generator is opened so that conductive die conduction is generated plasma by control device, and powder particle surface is activated and generates heat；It is sintered blocking.

   1, beam-shaping body according to claim 10 for neutron capture treatment, it is characterized by: the discharging plasma sintering equipment further comprises the displacement measurement system for measuring the displacement of pressurizing device, for controlling the atmosphere control system of atmosphere in the mold, for cooling water-cooling system, for measuring the temperature measuring device of the temperature in the discharging plasma sintering equipment, the discharge plasma sintering process further comprises following steps: the control device controls the displacement measurement system to ensure that the displacement measurement system works normally, the control device controls the atmosphere control system to ensure that atmosphere is in the case of normal work in the mold, the control device controls the water-cooling system to ensure that the water-cooling system works normally, The control device controls the temperature measuring device to ensure the temperature in the discharging plasma sintering equipment in the case of normal work.