CN106310540A - Beam shaping body for neutron capture therapy - Google Patents
Beam shaping body for neutron capture therapy Download PDFInfo
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- CN106310540A CN106310540A CN201510222234.5A CN201510222234A CN106310540A CN 106310540 A CN106310540 A CN 106310540A CN 201510222234 A CN201510222234 A CN 201510222234A CN 106310540 A CN106310540 A CN 106310540A
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Abstract
The invention discloses a beam shaping body for neutron capture therapy, which comprises a beam entrance, a target material, a retarder adjacently connected with the target material, a reflector surrounding the retarder, a thermal neutron absorber adjacently connected with the retarder, radiation shielding arranged in the beam shaping body and a beam exit, wherein the target material and a proton beam incident from the beam entrance are subjected to a nuclear reaction to produce neutrons, the neutrons form a neutron beam defining a main shaft, the retarder retards the neutrons produced by the target material to an epithermal neutron energy region, the retarder is made of at least one material containing LiF, Li2CO3, Al2O3, AlF3, CaF2 or MgF2, powder or powder compact becomes a block through a powder sintering process via a powder sintering device, the reflector guides the neutrons deviating from the main shaft back to the main shaft to improve the strength of the epithermal neutron beam, the thermal neutron absorber is used for absorbing the thermal neutrons to avoid excessive dose with shallow normal tissues in the case of therapy; and the radiation shielding is used for shielding leaky neutrons and photons to reduce the normal issue dose in a non irradiation area.
Description
Technical field
The present invention relates to a kind of beam-shaping body, particularly relate to a kind of beam-shaping body for neutron capture treatment.
Background technology
Along with the development of atomics, one of radiation cure Main Means becoming treatment of cancer such as such as cobalt 60, linear accelerator, electron beam.But conventional photonic or electronic therapy are limited by the physical condition of lonizing radiation own, while killing tumor cell, also normal structure substantial amounts of in beam approach can be damaged；Additionally, due to the tumor cell difference to lonizing radiation sensitivity, traditional radiation therapy is for relatively having the malignant tumor of radiation resistance (such as: multirow glioblastoma multiforme (glioblastoma
Multiforme), melanocytoma (melanoma)) treatment effect the best.
In order to reduce the radiation injury of tumor surrounding normal tissue, the target therapy concept in chemotherapy (chemotherapy) is just applied in radiation cure；And for the tumor cell of radiation resistance, currently also actively development has 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 to combine above two concept, as boron neutron capture is treated, gathers at the specificity of tumor cell by boracic medicine, coordinates neutron beam regulation and control accurately, it is provided that treatment of cancer more more preferable than conventional radiation selects.
Boron neutron capture treatment (Boron Neutron Capture Therapy, BNCT) be utilize boracic (10B) medicine has the characteristic of high capture cross section to thermal neutron, by10B(n,α) 7Li neutron capture and karyokinesis reaction produce4He 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 formula, the average energy of two charged particles is about 2.33MeV, has 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 burden particle is then 175
KeV/ μm, 5 μm, the integrated range of two particle is approximately equivalent to a cell size, therefore the radiation injury caused for organism can be confined to cell level, when boracic drug selectivity be gathered in tumor cell, suitable neutron of arranging in pairs or groups penetrates source, just can cause too on the premise of major injury at not normal tissue, reach local and kill the purpose of tumor cell.
Because the effect of boron neutron capture treatment depends on tumor cell position boracic drug level and thermal neutron quantity, therefore binary lonizing radiation treatment of cancer (the binary cancer that is otherwise known as
Therapy)；It follows that except the exploitation of boracic medicine, neutron is penetrated source flux and is occupied key player with improving of quality in the research of boron neutron capture treatment.
Summary of the invention
Flux and the quality in source is penetrated in order to improve neutron, one 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 the most external reflector, the thermal neutron absorber adjacent with slow body, it is arranged on the radiation shield in beam-shaping body and beam outlet, target and the proton beam generation nuclear reaction incident from beam entrance are to produce neutron, neutron forms neutron beam, neutron beam limits a main shaft, slow body by the neutron degradation that produces from target to epithermal neutron energy district, the material of slow body is by containing LiF, Li2CO3、Al2O3、AlF3、CaF2Or MgF2In at least one material make, wherein the material of slow body is become block by powder sintering process by powder or powder compact through powder sintered equipment, reflector will deviate from the neutron of main shaft and leads back to main shaft to improve epithermal neutron intensity of beam, thermal neutron absorber is used for when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure, and radiation shield is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district.
Beam-shaping body is further used for the treatment of accelerator boron neutron capture, proton beam is accelerated by the treatment of accelerator boron neutron capture by accelerator, target is made of metal, proton beam accelerates to the energy that be enough to overcome target atom core coulomb repulsion, with target generation nuclear reaction to produce neutron, beam-shaping physical ability by neutron slowly to epithermal neutron energy district, and reduce thermal neutron and fast neutron content, epithermal neutron energy district is between 0.5eV to 40keV, hanker subzone less than 0.5eV, fast-neutron range is more than 40keV, reflector is made up of the material having neutron reflection ability strong, thermal neutron absorber is made up of the material big with thermal neutron action section.
As one preferably, reflector is made up of at least one in Pb or Ni, thermal neutron absorber by6Li makes, and is provided with air duct between thermal neutron absorber and beam outlet, and radiation shield includes the photon being made up of Pb shielding and the neutron shield being made up of PE.
In order to effectively slow down neutron beam, on the one hand, as one 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, a length of 30cm-100cm of Second bobbin diameter, 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.
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 the powder in heating furnace, the pressue device being placed in heating furnace, mould, loading mould or powder compact and for controlling the control device that hot-press sintering equipment normally works, and hot-pressing sintering technique comprises the steps: to fill mould with appropriate powder or powder compact；Open hot pressing furnace with preset pressure and temperature parameter；Powder in mould or powder compact are pressurizeed by mobile pressue device；Control device and control hot-press sintering equipment when normal work；Energising is to sinter in bulk.
As another kind preferably, discharging plasma sintering equipment includes the first electrode, the second electrode, the conductive die being placed between the first electrode and the second electrode, provides the impulse current generator of pulse current to mould, with the pressue device of the pressing means for pressurization with for controlling the control device of pulse current transmitter and pressue device, at least one in first electrode and the second electrode can move, and at least one in the first electrode and the second electrode is connected with pressue device it is thus possible to add the powder being pressed in mould；Discharge plasma sintering process comprises the steps: appropriate powder is filled mould；Powder in mould is pressurizeed by mobile second electrode；Opening impulse current generator by control device and produce plasma to be conducted electricity by conductive die, powder particle surface is activated and generates heat；Sintering in bulk.
Discharging plasma sintering equipment farther includes the displacement measurement system of the displacement for measuring pressue device, the atmosphere control system of atmosphere in controlling mould, water-cooling system for cooling, the temperature measuring equipment of the temperature in measuring discharging plasma sintering equipment, discharge plasma sintering process farther includes following steps: control device control bit shift measurement system to guarantee that displacement measurement system normally works, control device and control atmosphere control system to guarantee that atmosphere is when normal work in mould, control device and control water-cooling system to guarantee that water-cooling system normally works, control device control temperature measuring equipment with guarantee in discharging plasma sintering equipment temperature when normal work.
" cylinder " or " bar shape " described in the embodiment of the present invention refers to the structure being basically unchanged along the side of direction as shown to the overall trend of its outline of opposite side, a wherein contour line of outline can be line segment, corresponding contour line such as cylindrical shape, it can also be the circular arc close to line segment that curvature is bigger, the corresponding contour line of sphere body shape as bigger in curvature, the whole surface of outline can be rounding off, can also be non-rounding off, as a lot of projection and groove have been done in the surface of the sphere body shape bigger at cylindrical shape or curvature.
" cone " or " cone-shaped " described in the embodiment of the present invention refers to the structure tapered into along the side of direction as shown to the overall trend of its outline of opposite side, a wherein contour line of outline can be line segment, corresponding contour line such as cone shape, it can also be circular arc, corresponding contour line such as sphere body shape, the whole surface of outline can be rounding off, it is also possible to be non-rounding off, as done a lot of projection and groove on the surface of cone shape or sphere body shape.
Accompanying drawing explanation
Fig. 1 is that boron neutron capture reacts schematic diagram.
Fig. 2 is10B(n,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, and wherein, the clearance channel position that slow body is arranged in bicone, and 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, and wherein, the clearance channel position that slow body is arranged in bicone, and first embodiment is filled with reflector material.
Fig. 6 is the neutron yield rate figure of neutron energy differential double with 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 facilities schematic diagram of the slow body material in one of them embodiment of the present invention, and wherein, this preparation facilities is discharging plasma sintering equipment.
Figure 10 is the preparation facilities schematic diagram of the slow body material in one of them embodiment of the present invention, and wherein, this preparation facilities is hot-press sintering equipment.
Detailed description of the invention
Neutron capture is treated the application in recent years of the means as a kind of effective treatment cancer and is gradually increased, wherein most commonly seen with the treatment of boron neutron capture, and the neutron of supply boron neutron capture treatment can be by nuclear reactor or accelerator supply.Embodiments of the invention are as a example by accelerator boron neutron capture is treated, the basic module of accelerator boron neutron capture treatment generally includes the accelerator for being accelerated charged particle (such as proton, deuteron etc.), target and hot removal system and beam-shaping body, wherein accelerate charged particle and produce neutron with metal targets effect, selecting suitable nuclear reaction according to required neutron yield rate and energy, available acceleration charged particle energy and size of current, the characteristic such as materialization of metal targets, the nuclear reaction often come 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, the epithermal neutron that preferable neutron source is keV energy grade due to the treatment of boron neutron capture, if using energy to be only slightly taller than the proton bombardment lithium metal target of threshold values in theory, 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) and two kinds of targets of beryllium metal (Be) are the highest with the proton-effect cross section of threshold values energy, for producing sufficiently large neutron flux, the proton of higher-energy is generally selected to carry out initiated core reaction.
Preferably target should possess high neutron yield rate, the neutron energy of generation is distributed close to epithermal neutron energy district (will be described in more detail below), wears by force the characteristics such as radiation produces, safety is the most easily operated and high temperature resistant without too many, but actually and cannot find and meet required nuclear reaction, embodiments of the invention use the target that lithium metal is made.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 selected, as7Li(p,n)7Be is poor because of fusing point and the thermal conductivity coefficient of metal targets (lithium metal), to the requirement of hot removal system the most relatively9Be(p,n)9B is high.Embodiments of the invention use7Li(p,n)7The nuclear reaction of Be.
No matter the neutron source of boron neutron capture treatment is from the nuclear reaction of nuclear reactor or accelerator charged particle with target, generation be all mixed radiation field, i.e. beam contains mental retardation to the neutron of high energy, photon；Boron neutron capture for deep tumor is treated, and in addition to epithermal neutron, remaining radiation content is the most, and the ratio causing the non-selective dosage of normal structure to deposit is the biggest, and therefore these can cause the radiation of unnecessary dosage to reduce as far as possible.Except air beam quality factor, for knowing more about the dose distribution that neutron causes in human body, embodiments of the invention use human body head tissue prosthesis carry out Rapid Dose Calculation, and be 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) is for the neutron source of clinical boron neutron capture treatment, given five air beam quality factor suggestions, these five suggestions can be used for the quality of the different neutron source of comparison, and is provided with as reference frame when selecting neutron the way of production, design beam-shaping body.These five suggestions 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 district, between 0.5eV to 40keV, hankers subzone and is more than 40keV less than 0.5eV, fast-neutron range.
1, 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, the requirement for neutron beam flux just can reduce；Otherwise, if boracic drug level is low in tumor, then need high flux epithermal neutron to give the dosage that tumor is enough.IAEA is more than 10 for the epithermal neutron number that requirement is every square centimeter per second of epithermal neutron beam flux9, neutron beam under this flux can substantially control treatment time for current boracic medicine in one hour, and short treatment time is in addition to having superiority to patient location and comfort level, it is possible to compared with effectively utilizing boracic medicine in intra-tumor limited holdup time.
2, fast neutron pollutes:
Owing to fast neutron can cause unnecessary normal tissue dose, therefore regard as polluting, this dosage size and neutron energy be proportionate, and therefore should reduce the content of fast neutron in neutron beam design as far as possible.Fast neutron pollutes and is defined as the fast neutron dosage that unit epithermal neutron flux is adjoint, and the suggestion that fast neutron is polluted by IAEA is less than 2 x 10-13 Gy-cm2/n。
3, photon contamination (gamma-ray contamination):
Gamma-rays belongs to wears by force radiation, can non-selectively cause institute's organized dosage deposition on course of the beam, therefore the exclusive requirement that gamma-rays content is also neutron beam design is reduced, gamma-ray contamination is defined as the gamma-rays dosage that unit epithermal neutron flux is adjoint, and IAEA is less than 2 x 10 to the suggestion of gamma-ray contamination-13 Gy-cm2/n。
4, thermal and epithermal neutron flux ratio:
Owing to thermal neutron decay speed is fast, penetration capacity is poor, after entering human body, major part energy deposition is at 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 tumor such as cerebromas.IAEA is less than 0.05 to the suggestion of thermal and epithermal neutron flux ratio.
5, middle electron current and flux ratio:
Middle electron current and flux ratio represent the directivity of beam, and before ratio the biggest expression neutron beam, tropism is good, and the neutron beam of high front tropism can reduce because neutron dissipates the normal surrounding tissue dosage caused, and additionally also improve and can treat the degree of depth and pendulum pose gesture elasticity.IAEA centering electron current and flux ratio suggestion are for more than 0.7.
Utilize prosthese to obtain in-house 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 for carrying out the comparison of different neutron beam treatment benefit.
1, effective therapeutic depth:
Tumor dose is less than normal structure maximal dose equal to the degree of depth of normal structure maximal dose, the position after this degree of depth, the dosage that tumor cell obtains, i.e. loses the advantage of boron neutron capture.This parameter represents the penetration capacity of neutron beam, and the medicable tumor depth of the biggest expression of effective therapeutic depth is the deepest, and unit is cm.
2, effective therapeutic depth close rate:
The i.e. tumor dose rate of effective therapeutic depth, also equal to the maximum dose rate of normal structure.Being the factor that impact can give tumor accumulated dose size because normal structure receives accumulated dose, therefore parameter affects the length for the treatment of time, and the irradiation time needed for the biggest expression of effective therapeutic depth close rate gives tumor doses is the shortest, and unit is cGy/mA-min.
3, dose therapeutically effective ratio:
From brain surface to effective therapeutic depth, the mean dose ratio that tumor and normal structure receive, referred to as dose therapeutically effective ratio；The calculating of mean dose, can be obtained by dose versus depth curvilinear integral.Dose therapeutically effective ratio is the biggest, and the treatment benefit representing this neutron beam is the best.
Compare foundation to make beam-shaping body have in design, except beam quality factor and above-mentioned three parameters in the air of five IAEA suggestion, the embodiment of the present invention also utilize following for assessing the parameter that the performance of neutron beam dosage is good and bad:
1, the proton electric current that irradiation time≤30min(accelerator uses is 10mA)
2、
30.0RBE-Gy can treat the degree of depth >=7cm
3, tumor maximal dose >=60.0RBE-Gy
4, normal cerebral tissue's maximal dose≤12.5RBE-Gy
5, skin maximal dose≤11.0RBE-Gy
Note: RBE(Relative
Biological Effectiveness) it is relative biological effect, the biological effect that can cause due to photon, neutron is different, so dosage item as above is multiplied by the relative biological effect of different tissues respectively in the hope of dose,equivalent.
Penetrate flux and the quality in source to improve neutron, embodiments of the invention are the improvement proposed for the beam-shaping body treated for neutron capture, as one preferably, are the improvement for the beam-shaping body treated for accelerator boron neutron capture.nullAs 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、The adjacent slow body 13 with target 12、It is enclosed in the reflector 14 outside slow body 13、With the adjacent thermal neutron absorber 15 of slow body 13、The radiation shield 16 being arranged in beam-shaping body 10 and beam outlet 17，Target 12 and the proton beam generation nuclear reaction from beam entrance 11 incidence are to produce neutron，Neutron forms neutron beam，Neutron beam limits a major axis X，Slow body 13 by the neutron degradation that produces from target 12 to epithermal neutron energy district，Reflector 14 will deviate from the neutron of major axis X and leads back to major axis X to improve epithermal neutron intensity of beam，Slowly clearance channel 18 is set between body 13 and reflector 14 to improve epithermal neutron flux，Thermal neutron absorber 15 is used for when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure，Radiation shield 16 is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district.
Proton beam is accelerated by the treatment of accelerator boron neutron capture by accelerator, and as a kind of preferred embodiment, target 12 is made up of lithium metal, and proton beam accelerates to the energy that be enough to overcome target atom core coulomb repulsion, occurs with target 127Li(p,n)7Be nuclear reaction is to produce neutron.Beam-shaping body 10 by neutron slowly to epithermal neutron energy district, and can reduce thermal neutron and fast neutron content, and slow body 13 is made by having the material that fast neutron action section is big, epithermal neutron action section is little, and as a kind of preferred embodiment, slow body 13 is by D2O、AlF3、FluentalTM、CaF2、Li2CO3 、MgF2And Al2O3In at least one make.Reflector 14 is made up of the material having neutron reflection ability strong, and as a kind of preferred embodiment, reflector 14 is made up of at least one in Pb or Ni.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 as a kind of preferred embodiment, radiation shield 16 includes the photon being made up of lead (Pb) shielding 161 and the neutron shield 162 being made up of polyethylene (PE).
Wherein, it is cone-shaped that slow body 13 is arranged to that two rightabouts adjoin each other, direction as shown in Figure 3, and the left side of slow body 13 is taper into towards left side cone-shaped, and the right side of slow body 13 is taper into towards right side cone-shaped, and both adjoin each other.As one preferably, it is cone-shaped that the left side of slow body 13 is set to taper into towards left side, and right side can also be arranged to its allothimorph shape and cone-shaped adjoin each other, such as bar shape etc. with this.Reflector 14 is enclosed in around slow body 13 closely, it is provided with clearance channel 18 between slow body 13 and reflector 14, so-called clearance channel 18 refers to the empty region easily allowing neutron beam pass through that unused solid material covers, as this clearance channel 18 could be arranged to air duct or vacuum passage.It is close to the thermal neutron absorber 15 of slow body 13 setting by the thinnest one layer6Li material is made, and the photon being made up of the Pb shielding 161 in radiation shield 16 can be set to one with reflector 14, it is also possible to be arranged to split, and the neutron shield 162 being made up of PE in radiation shield 16 can be positioned adjacent to the position of beam outlet 17.Exporting at thermal neutron absorber 15 and beam and be provided with air duct 19 between 17, in this region, the sustainable neutron that will deviate from major axis X leads back to major axis X to improve epithermal neutron intensity of beam.Prosthese B is arranged at distance beam outlet 17 about 1cm.Well known to those skilled in the art, photon shielding 161 can be made up of other materials, as long as playing the effect of shielding photon, neutron shield 162 can also be made up of other materials, can also be arranged on other local, as long as disclosure satisfy that the condition of shielding seepage neutron.
The difference of the beam-shaping body in order to compare the beam-shaping body being provided with clearance channel and be not provided with clearance channel, as shown in Figure 4 and Figure 5, which respectively show the second embodiment using slow body to fill clearance channel and the 3rd embodiment using reflector to fill clearance channel.nullWith reference first to Fig. 4，This beam-shaping body 20 includes beam entrance 21、Target 22、The adjacent slow body 23 with target 22、It is enclosed in the reflector 24 outside slow body 23、With the adjacent thermal neutron absorber 25 of slow body 23、The radiation shield 26 being arranged in beam-shaping body 20 and beam outlet 27，Target 22 and the proton beam generation nuclear reaction from beam entrance 21 incidence are to produce neutron，Neutron forms neutron beam，Neutron beam limits a major axis X 1，Slow body 23 by the neutron degradation that produces from target 22 to epithermal neutron energy district，Reflector 24 will deviate from the neutron of major axis X 1 and leads 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 is taper into towards left side cone-shaped，The right side of slow body 23 is taper into towards right side cone-shaped，Both adjoin each other，Thermal neutron absorber 25 is used for when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure，Radiation shield 26 is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district.
As one preferably, target 22, slow body 23, reflector 24, thermal neutron absorber 25 and radiation shield 26 in second embodiment can be identical with first embodiment, and radiation shield 26 therein includes the photon being made up of lead (Pb) shielding 261 and the neutron shield 262 being made up of polyethylene (PE), this neutron shield 262 can be arranged on beam and export at 27.Export at thermal neutron absorber 25 and beam and be provided with air duct 28 between 27.Prosthese B1 is arranged at distance beam outlet 27 about 1cm.
nullRefer to Fig. 5，This beam-shaping body 30 includes beam entrance 31、Target 32、The adjacent slow body 33 with target 32、It is enclosed in the reflector 34 outside slow body 33、With the adjacent thermal neutron absorber 35 of slow body 33、The radiation shield 36 being arranged in beam-shaping body 30 and beam outlet 37，Target 32 and the proton beam generation nuclear reaction from beam entrance 31 incidence are to produce neutron，Neutron forms neutron beam，Neutron beam limits a major axis X 2，Slow body 33 by the neutron degradation that produces from target 32 to epithermal neutron energy district，Reflector 34 will deviate from the neutron of major axis X 2 and leads 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 is taper into towards left side cone-shaped，The right side of slow body 33 is taper into towards right side cone-shaped，Both adjoin each other，Thermal neutron absorber 35 is used for when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure，Radiation shield 36 is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district.
As one preferably, target 32, slow body 33, reflector 34, thermal neutron absorber 35 and radiation shield 36 in 3rd embodiment can be identical with first embodiment, and radiation shield 36 therein includes the photon being made up of lead (Pb) shielding 361 and the neutron shield 362 being made up of polyethylene (PE), this neutron shield 362 can be arranged on beam and export at 37.Export at thermal neutron absorber 35 and beam and be provided with air duct 38 between 37.Prosthese B2 is arranged at distance beam outlet 37 about 1cm.
Using MCNP software below (is by Los Alamos National Laboratories of the U.S. (LosAlamos
National Laboratory) neutron for calculating in 3 D complex geometry based on DSMC, photon, charged particle or the common software bag of coupling neutron/photon/charged particle transport problem developed) simulation of these three embodiment is calculated:
Wherein, performance in these three embodiment of beam quality factor in air (in form, each name lexeme is same as above, does not repeats them here, lower with) is shown such as following table one:
Table one: beam quality factor in air
Wherein, the performance in dose form present these three embodiment is shown such as following table two:
Table two: dosage shows
Wherein, assessment neutron beam dosage performance good and bad parameter simulation value in these three embodiment is shown such as following table three:
Table three: the parameter that assessment neutron beam dosage performance is good and bad
Note: being appreciated that from three above-mentioned tables: be provided with the beam-shaping body of clearance channel between slow body and reflector, the treatment benefit of its neutron beam is best.
Neutron owing to producing from lithium target has the characteristic that Forward averaging energy is higher, as shown in Figure 6, neutron scattering angle average neutron energy between 0 °-30 ° is about 478keV, and the average neutron energy that neutron scattering angle is between 30 °-180 ° about only has 290keV, if can be by the geometry changing beam-shaping body, forward direction neutron is made to produce more collision with slow body, and laterally neutron just can arrive beam outlet through less collision, the slow optimization of neutron, efficient raising epithermal neutron flux should be can reach the most in theory.Geometry from beam-shaping body is set about below, evaluates the geometry impact for epithermal neutron flux of different beam-shaping body.
nullAs shown in Figure 7，It illustrates the geometry of beam-shaping body in the 4th embodiment，This beam-shaping body 40 includes beam entrance 41、Target 42、The adjacent slow body 43 with target 42、It is enclosed in the reflector 44 outside slow body 43、With the adjacent thermal neutron absorber 45 of slow body 43、The radiation shield 46 being arranged in beam-shaping body 40 and beam outlet 47，Target 42 and the proton beam generation nuclear reaction from beam entrance 41 incidence are to produce neutron，Slow body 43 by the neutron degradation that produces from target 42 to epithermal neutron energy district，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 when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure，Radiation shield 46 is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district，Export at thermal neutron absorber 45 and beam and be provided with air duct 48 between 47.
nullAs shown in Figure 8，It illustrates the geometry of beam-shaping body in the 5th embodiment，This beam-shaping body 50 includes beam entrance 51、Target 52、The adjacent slow body 53 with target 52、It is enclosed in the reflector 54 outside slow body 53、With the adjacent thermal neutron absorber 55 of slow body 53、The radiation shield 56 being arranged in beam-shaping body 50 and beam outlet 57，Target 52 and the proton beam generation nuclear reaction from beam entrance 51 incidence are to produce neutron，Neutron forms neutron beam，Neutron beam limits a major axis X 3，Slow body 53 by the neutron degradation that produces from target 52 to epithermal neutron energy district，Reflector 54 will deviate from the neutron of major axis X 3 and leads 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 is taper into towards right side cone-shaped，Both adjoin each other，Thermal neutron absorber 25 is used for when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure，Radiation shield 26 is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district.
As one preferably, target 52, slow body 53, reflector 54, thermal neutron absorber 55 and radiation shield 56 in 5th embodiment can be identical with first embodiment, and radiation shield 56 therein includes the photon being made up of lead (Pb) shielding 561 and the neutron shield 562 being made up of polyethylene (PE), this neutron shield 562 can be arranged on beam and export at 57.Export at thermal neutron absorber 55 and beam and be provided with air duct 58 between 57.Prosthese B3 is arranged at distance beam outlet 57 about 1cm.
Use MCNP software that the simulation of the cylinder+cone in the slow body of the cylinder in the slow body of bicone, the 4th embodiment in the second embodiment and the 5th embodiment is calculated below:
Wherein, beam quality factor performance in these three embodiment in air is shown such as following table four:
Table four: beam quality factor in air
Wherein, the performance in dose form present these three embodiment is shown such as following table five:
Table five: dosage shows
Wherein, assessment neutron beam dosage performance good and bad parameter simulation value in these three embodiment is shown such as following table six:
Table six: the parameter that assessment neutron beam dosage performance is good and bad
Note: be appreciated that from three above-mentioned tables: slow body is arranged at least one is 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 being basically unchanged along the side of direction as shown to the overall trend of its outline of opposite side, a wherein contour line of outline can be line segment, corresponding contour line such as cylindrical shape, it can also be the circular arc close to line segment that curvature is bigger, the corresponding contour line of sphere body shape as bigger in curvature, the whole surface of outline can be rounding off, can also be non-rounding off, as a lot of projection and groove have been done in the surface of the sphere body shape bigger at cylindrical shape or curvature.
" cone " or " cone-shaped " described in the embodiment of the present invention refers to the structure tapered into along the side of direction as shown to the overall trend of its outline of opposite side, a wherein contour line of outline can be line segment, corresponding contour line such as cone shape, it can also be circular arc, corresponding contour line such as sphere body shape, the whole surface of outline can be rounding off, it is also possible to be non-rounding off, as done a lot of projection 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 the material that slow body is discussed is made, hereafter as a example by first embodiment and accompanying drawing 3, 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 has the first diameter D1, Second bobbin diameter D2 and the 3rd diameter D3.Being provided with opening at first diameter D1 to accommodate target 12, Second bobbin diameter D2 is set at the full-size of double cone structure.For BNCT, in order to reach enough slow effect, the first a length of 1cm-20cm of diameter D1, the a length of 30cm-100cm of Second bobbin diameter D2, the 3rd a length of 1cm-50cm of diameter D3, as one preferably, the first a length of 10cm of diameter D1, the a length of 70cm of Second bobbin diameter D2, the 3rd a length of 30cm of diameter D3.In order to obtain such large-sized slow body 13, and the density of its material is the 80%-100% of solid density, it is provided that the preparation of following three kinds of slow body materials.
1.
Long crystalline substance
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 the reference as long crystalline substance preparation.As the mode of long crystalline substance, generally will plant brilliant and contain MgF2Powder put into crucible, by the way of certain, grow MgF2Monocrystalline.
Needing to give special heed to, the most so-called " monocrystalline " refers to single crystal of single growth molding, and is not single crystal grain (i.e. only have a kind of crystal form and comprise only a crystal grain, in this crystal grain, molecule, courtyard are all arrangements regularly).Be best understood from is that this single crystal grain is corresponding from multiple crystal grain (size and shape of the most each crystal grain is different, and it is also in disorder for being orientated, and does not has obvious profile, does not the most show anisotropy).Below with respect to the definition of " monocrystalline " with where like.
Through investigation, AlF3、 CaF2、LiF、Li2CO3And Al2O3Can also prepare by the way of similar.
2.
Powder sintered
By MgF2Or AlF3Or CaF2Powder or powder compact further combined with getting up, in sintering process powder particle to occur mutually to flow, spread, dissolve, the physical and chemical process such as recrystallization, make powder the finest and close, eliminate part or all of hole therein.Sintering processing can have a variety of, if solid-phase sintering, i.e. sintering temperature are in body of powder below the fusing point of each constituent element；Liquid-phase sintering, if i.e. having two or more constituent elements in powder compact, sinters likely carried out above at 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. when sintering, applies pressure to body of powder, and to promote its densification process, hot pressing is the shaping powder and sinter bonded, directly obtains the technical process of goods；Discharge plasma sintering, the ON-OFF DC pulse voltage i.e. occurred by particular power source controls device is added on powder body test portion, in addition to utilizing the sintering facilitation caused by usual electro-discharge machining (discharge impact pressure and Joule heating), the sintering facilitation caused by Spark Discharges (moment produces high-temperature plasma) produced between pulsed discharge initial stage powder body is the most effectively utilized to be realized the Fast Sintering technology of densification by TRANSIENT HIGH TEMPERATURE field.The material of slow body is become block by powder sintering process by powder or powder compact through powder sintered equipment.
Well known to those skilled in the art, other sintering processing also can realize MgF2Or AlF3Or CaF2In at least one or several mixture as the preparation of the material of slow body.As one 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 are heated to be one, programming rate is fast, sintering time is short, sintering temperature is low, crystal grain is uniform, be conducive to controlling sintered body fine structure, the consistency obtaining material are high, and have simple to operate, repeatability is high, safe and reliable, save space, save the energy and low cost and other advantages.Discharge plasma sintering is added between powder particle due to high power pulse electric current, the both positive and negative polarity of electric field induction is there is between powder particle, 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, power storage in the dielectric layer of cluster of grains, dielectric layer generation batch (-type) repid discharge.Owing to there is pulse current between powder or powder compact, and pulse current is moment, interrupted, altofrequency generation, at the heat discharge that powder particle produces not in contact with position, and the Joule heat that powder particle contact site produces, the diffusion of powder particle atom is all greatly facilitated, much greater than under usual hot pressing condition of its diffusion coefficient, thus reach powder sintered rapid.Furthermore, due to the addition of pulse current, make the electric discharge position in powder and joule heat position all can quickly move, enable the sintering homogenization of powder or powder compact.During discharge plasma sintering, between granule during electric discharge, the instantaneous generation of meeting is up to the localized hyperthermia of thousand of degree to 10,000 degree, evaporation and fusing is caused at particle surface, cervical region is formed at grain contact point, being delivered to particle surface due to heat immediately from heating center and spread to surrounding, cervical region quickly cools down and makes vapour pressure be less than other positions.Gaseous substance condenses upon cervical region and forms another important feature that the evaporation higher than ordinary sinter method-solidification transmission 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 can get high-quality sintered body with relatively low temperature and comparatively short time.Discharge plasma sintering process can be regarded as granule electric discharge, conductive heater and the result of pressurization comprehensive function.
Refer to Fig. 9, there is disclosed the schematic diagram of a kind of discharging plasma sintering equipment.nullDischarging plasma sintering equipment 100 includes the first electrode 101、Second electrode 102、It is placed in the conductive die 103 between the first electrode 101 and the second electrode 102、The impulse current generator 104 of pulse current is provided to mould 103、With the pressing means 1051 for pressurization、The pressue device 105 of 1052 and for controlling the control device 106 of impulse current generator 104 and pressue device 105，At least one in first electrode 101 and the second electrode 102 can move，Pressing means 1051、At least one in 1052 can move，As one preferably，First electrode 101 and pressing means 1051 are fixed，Second electrode 102 and pressing means 1052 can move，It is thus possible to add the powder being pressed in mould 103 or powder compact 107.As one preferably, conductive die 103 is set to lead or graphite.Discharging plasma sintering equipment 100 farther includes the displacement measurement system 108 of the displacement for measuring pressue device 105, the atmosphere control system 109 of atmosphere in controlling described mould 103, for controlling the water-cooling system 111 that water-cooled vacuum room 110 cools down, for measuring the temperature measuring equipment 112 of the temperature in discharging plasma sintering equipment 100.Mould 103 and powder or powder compact 107 lead to upper pulse current, in addition to providing discharge impact pressure and Joule heat to be sintered, Fast Sintering is realized by TRANSIENT HIGH TEMPERATURE field further with the sintering facilitation caused by the Spark Discharges (moment produces high-temperature plasma) produced between pulsed discharge initial stage powder body, so that powder or powder compact 107 become block from pulverulence, so-called bulk is formed in one, without such as long brilliant mode, monocrystalline it is spliced into applicable slow body size by operations such as polishings or polishing.
This discharging plasma sintering equipment 100 utilizes DC pulse current direct-electrifying sintering and pressurization, controls heating rate and sintering temperature through controlling device 106 by the size of regulation pulsed direct current.Whole sintering process can be carried out under vacuum conditions, it is possible to carries out in protective atmosphere, such as oxygen or hydrogen.
Under oxygen atmosphere, owing to 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, make the oxygen in closed pore can be directly entered lattice simultaneously, and the same with oxygen ion vacancy be diffused along surface, spread and sinter acceleration.When sintering controlled by positive diffusions time, oxidizing atmosphere or partial pressure of oxygen is higher and beneficially cation room 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, owing to hydrogen atom radius is the least, it is easy to spread and the elimination of beneficially closed pore, the material of the type such as aluminium oxide sinters the available sintered body sample close to solid density under hydrogen atmosphere.
Sintering temperature is one of crucial parameter during plasma Fast Sintering.Determination sintered body the to be considered sample of sintering temperature phase in version, the growth rate of crystal grain, the prescription of sample and the density requirements of sample at high temperature.Generally, along with the rising of sintering temperature, sample consistency entirety is in rising trend, and this explanation sintering temperature has significantly impact to sample consistency degree, and sintering temperature is the highest, and in sintering process, mass transfer speed is the fastest, and sample is the easiest to be closely knit.
But, temperature is the highest, and the growth rate of crystal grain is the fastest, and its mechanical property is the poorest.And temperature is the lowest, the consistency of sample is the lowest, can't meet the quality requirement.Contradiction between temperature and grain size requires a suitable parameter in the selection of temperature.
Extending the temperature retention time under sintering temperature, the most all can complete by acceleration of sintering to some extent, improve the microstructure of sample, this is more obvious to the sintering of VISCOUS FLOW mechanism, and affects less on 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, prolongation along with temperature retention time, the consistency of sample increases, but excursion is not very big, although illustrating that the consistency of sample is had a certain impact by temperature retention time, but action effect is not clearly.But extending the temperature retention time under sintering temperature unreasonably, crystal grain is drastically grown up at this moment, aggravates secondary recrystallization effect, is unfavorable for the performance requirement of sample, and the densification that time the shortest meeting causes sample declines, it is therefore desirable to select suitable temperature retention time.
The quickening of time heating rate, sample is made to reach 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 of crystal grain, obtain fine grain of uniform size pottery, moreover it is possible to save the time, save the energy and improve the utilization rate of agglomerating plant.But, due to the restriction of equipment itself, heating rate is too fast can cause a devastating effect to equipment.Therefore quickening heating rate as far as possible in admissible scope.But, reflect in the experimental data of actual measurement and arrive.Different from sintering temperature and temperature retention time, heating rate demonstrates contrary result to the impact of sample consistency, i.e. along 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 shorten temperature retention time near sintering temperature, thus sample consistency can decline.In actual high-temperature sintering process, temperature-rise period is generally divided into three phases, be respectively from about room temperature to 600 DEG C, about 600 DEG C to 900 DEG C, 900 DEG C to sintering temperature: the first stage is the preparatory stage, and heating rate is the slowest；Second stage is controlled being rapidly heated the stage, and heating rate general control is 100 ~ 500 (DEG C/min)；Phase III is the buffer stage heated up, and this 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 after being substantially discharged process immediately.Sintered material occurs serious plastic deformation, applying forming pressure to be conducive to the contact strengthening between powder particle, increase sintering area, the residual gas discharged between sintered powder, raising product intensity, density and surface smoothness thereof under the common effect of resistance Joule heat and pressure.The size of forming pressure is typically based on the compressibility of sintered powder and the requirement to the performance such as density of sintered material, intensity determines, typically in the range of 15～30 MPa, there may come a time when up to 50 MPa, the highest.Generally, forming pressure is the biggest, and the density of sintered material is the highest.Density of sintered material is also had a great impact by the pressurization persistent period, and suitable pressing time is different regarding the kind of sintered material, powder size and the physical dimension of institute's 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 obtaining the most high-density sintered material.Easy to understand from sintering and solid state reaction mechanism, pressure is the biggest, and in sample, particle packing is the tightst, and it is accelerated that mutual contact point and contact area increase sintering.Sample so can be made to obtain more preferable consistency, and can effective inhibiting grain growth and reduction sintering temperature.Therefore the pressure selected 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 the most little, and the phenomenon that this explanation consistency increases with pressure is the most obvious.
Compared to conventional sintering technique, discharge plasma sintering has the advantage that sintering velocity is fast；Improve material microstructure and improve the performance of material.
Well known to those skilled in the art, mould can use other conductive material to make, and discharging plasma sintering equipment can also be arranged to two electrodes and all maintain static, 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 be fully contacted between powder particle, in order to be then able to produce uniform and sufficient plasma discharging in powder sample；Second stage: apply pulse current, under the effect of pulse current, powder particle contact point produces plasma discharging, and particle surface produces micro-exothermic phenomenon due to activation；Phase III: close the pulse power, sample is carried out resistance heating, till reaching predetermined sintering temperature and sample contraction completely；Fourth stage: release.The main technologic parameters such as conservative control initial pressure, sintering time, forming pressure, pressurization persistent period, sintering temperature, heating rate can obtain the material that combination property is good.
Due to the arch bridge effect between powder particle, they typically can not be fully contacted, therefore, for the plasma producing uniformly in sample when making electric spark sintering and being substantially discharged, farthest activated particle surface is to accelerate sintering densification process, need to apply suitable initial pressure to sintered powder, make powder particle be fully contacted.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 delay to sinter diffusion process.According to existing document, being sufficiently carried out for making electric discharge continue, this initial pressure is typically no more than 10MPa.
When with electric spark sintering electric conductivity preferable powdered sample, owing to resistance heats carrying out from sample the most simultaneously, therefore sintering time is extremely short, even moment, but sintering time length should regard powder quality, kind and performance and different, and the most several seconds to a few minutes；When sintering large-scale, refractory metal powder material, even up to dozens of minutes.Sintering time is relatively big, for making densification process fully be carried out, therefore, to assure that certain sintering time on product density impact.
It is generally acknowledged, the sintering to powder that is rapidly heated during discharge plasma sintering is highly advantageous, because it inhibits the non-densifying mechanism of material to have activated the densification Mechanism of material, therefore, improve heating rate, the densification degree of sample can be made to be improved.
As one preferably, discharge plasma sintering process comprises the steps: to fill mould 103 with appropriate powder or powder compact 107；Powder in mould 103 or powder compact 107 are pressurizeed by mobile pressue device 105；Opening impulse current generator 104 by control device 106 and produce plasma to be conducted electricity by mould 103, powder particle surface is activated and generates heat；Sintering in bulk.Discharge plasma sintering process farther includes following steps: control device 106 control bit shift measurement system 108 to guarantee that displacement measurement system 108 normally works, control device 106 control atmosphere control system 109 with guarantee in mould 103 atmosphere when normal work, control device 106 control water-cooling system 111 with guarantee its when normal work, control device 106 control temperature measuring equipment 112 with guarantee in discharging plasma sintering equipment 100 temperature when normal work.So-called normal work refers to discharging plasma sintering equipment and the alarm signals such as the vision of human perception, sense of touch or audition does not occurs, and as alarm lamp lights, alarm lamp sounds, and instruction vibration etc. of reporting to the police is like this.
2.2
Hot pressed sintering
Hot pressed sintering is to be filled in model by dry powder, then adds flanging heating from limit, single shaft direction, makes a kind of sintering method that molding and sintering complete simultaneously.Hot pressing and sintering technique production technology is the abundantest, and classification is at present without unified standard and standard.Vacuum hotpressing, atmosphere hot pressing, vibrations hot pressing, equilibrium 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 due to heating pressurization carry out simultaneously, powder is in hot plastic state, contribute to granule contact diffusion, flowing mass transport process carrying out, thus briquetting pressure only cold pressing 1/10；Can also reduce sintering temperature, shorten sintering time, thus resist crystal grain and grow up, obtain that crystal grain is tiny, consistency is high and product mechanical, that electric property is good.
In order to use hot-pressing sintering technique to prepare slow body material, refer to Figure 10, hot-press sintering equipment 200 mainly includes heating furnace 201, the pressue device 202, mould 203, the powder loaded in mould 203 or the powder compact 204 that are placed in heating furnace 201 and control device 205.Heating furnace 201 is generally using electricity as thermal source, and heating element heater is by SiC, MoSi or nickel reeling, platinum wire, molybdenum filament etc..Pressue device 202 requires that speed is mild, pressurize is constant, pressure flexible, typically has lever and fluid pressure type.According to the requirement of material character, pressure atmosphere can be air can also be reducing atmosphere or inert atmosphere.Mould 203 requires high intensity, high temperature resistant, antioxidation and does not coheres with hot-pressed material, mould 203 thermal coefficient of expansion should consistent with hot-pressed material or approximation, as one preferably, in the present embodiment use graphite jig.Controlling device 205 makes hot-press sintering equipment 200 when normal work.So-called normal work refers to discharging plasma sintering equipment and the alarm signals such as the vision of human perception, sense of touch or audition does not occurs, and as alarm lamp lights, alarm lamp sounds, and instruction vibration etc. of reporting to the police is like this.
With MgF2As a example by using hot-pressing sintering technique to prepare the slow body of target, its technological process of production generally comprises following steps, MgF2Raw mill prepared by raw material, screening processes and proceeds 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 preferably, the process step that the sintering of the powder processing step and postorder that omit preamble at this completes.Hot-pressing sintering technique comprises the steps: to fill mould 203 with appropriate powder or powder compact 204；Open hot pressing furnace 201 with preset pressure and temperature parameter；Powder in mould 203 or powder compact 204 are pressurizeed by mobile pressue device 202；Control device 205 and control hot-press sintering equipment 200 when normal work；Energising is to sinter in bulk.
Need further illustrate be, step " powder in mould 203 or powder compact 204 are pressurizeed by mobile pressue device 202 " in hot-pressing sintering technique can be as precharge, can also synchronization carry out with energising, step " powder in mould 203 or powder compact 204 are pressurizeed by mobile pressue device 202 " and step " will be energized to sinter in bulk " and unite two into one.
Some parameters listing long brilliant, discharge plasma sintering and hot pressed sintering in following table compare, material as the slow body application in the beam-shaping body of the neutron capture treatment disclosed in a kind of present invention that is more convenient for, especially need to manufacture under the precondition of the Second bobbin diameter D2 maximum size that reaches 100cm, it is recommended here that use the powder sintered slow body material made, concrete detailed description in detail please see below.
Table seven: the long brilliant and comparison of powder sintering process
Though upper table only lists MgF2、AlF3
And CaF2These three slow body material uses the parameter of as above technique to compare, but well known to those skilled in the art, other three kinds slow body material LiF, Li2CO3And Al2O3Contrast can also be made easily.
It is appreciated that from upper table, although the density using long brilliant mode to prepare slow body material can reach close to solid density, as reached the 99.99% of solid density, but owing to monocrystalline size is less, want to reach the large-sized slow body material of target to need to be spliced by an a lot of monocrystalline, during it may also be desirable to it is carried out other operations such as mirror finish, not only the longest, and cost and technology difficulty are the biggest.
The density using powder sintered mode to prepare slow body material also is able to reach the 80%-100% of solid density.As one preferably, the density of slow body material reaches the 99.99% of solid density.Solid density is the most indiscriminate compared with the solid density of the slow body material that long crystal type obtains while, it is the most with the obvious advantage in terms of size, time, cost and the technology difficulty obtained.Slow its actual size of body material using discharge plasma sintering to prepare obtains as required, a kind of mode can customize out the mould being suitable for needs, another way uses common die, mould such as diameter 70cm* thickness 2cm, then carry out splicing by several just can complete, on the premise of cost and technology difficulty are all equally matched with vacuum heating-press sintering and HIP sintering, its manufacturing time has only to the time of about 1 month.
The beam-shaping body for neutron capture treatment that the present invention discloses is not limited to the content described in above example and the structure represented by accompanying drawing.The change apparently on the basis of the present invention, material, shape and the position of wherein component made, substitute or revise, all within the scope of protection of present invention.
Claims (10)
1. the beam-shaping body for neutron capture treatment, it is characterized in that: described beam-shaping body includes beam entrance, target, it is adjacent to the slow body of described target, it is enclosed in the most external described reflector, the thermal neutron absorber adjacent with described slow body, it is arranged on the radiation shield in described beam-shaping body and beam outlet, described target and the proton beam generation nuclear reaction incident from described beam entrance are to produce neutron, described neutron forms neutron beam, described neutron beam limits a main shaft, described slow body by the neutron degradation that produces from described target to epithermal neutron energy district, the material of described slow body is by containing LiF, Li2CO3、Al2O3、AlF3、 CaF2Or MgF2In at least one material make, the material of wherein said slow body is become block by powder sintering process by powder or powder compact through powder sintered equipment, described reflector will deviate from the neutron of described main shaft and leads back to described main shaft to improve epithermal neutron intensity of beam, described thermal neutron absorber is used for when absorbing thermal neutron to avoid treating causing multiple dose with shallow-layer normal structure, and described radiation shield is used for shielding the neutron of seepage and photon to reduce the normal tissue dose in non-irradiated district.
nullBeam-shaping body for neutron capture treatment the most according to claim 1，It is characterized in that: described beam-shaping body is further used for the treatment of accelerator boron neutron capture，Proton beam is accelerated by the treatment of accelerator boron neutron capture by accelerator，Described target is made of metal，Described proton beam accelerates to the energy that be enough to overcome target atom core coulomb repulsion，With described target generation nuclear reaction to produce neutron，Described beam-shaping physical ability by neutron slowly to epithermal neutron energy district，And reduce thermal neutron and fast neutron content，Described epithermal neutron energy district is between 0.5eV to 40keV，Described hanker subzone less than 0.5eV，Described fast-neutron range is more than 40keV，Described reflector is made up of the material having neutron reflection ability strong，Described thermal neutron absorber is made up of the material big with thermal neutron action section.
The most according to claim 2 for neutron capture treatment beam-shaping body, it is characterised in that: described reflector is made up of at least one in Pb or Ni, described thermal neutron absorber by6Li makes, and is provided with air duct between described thermal neutron absorber and the outlet of described beam, and described radiation shield includes the photon being made up of Pb shielding and the neutron shield being made up of PE.
Beam-shaping body for neutron capture treatment the most according to claim 1, it is characterised in that: it is cone-shaped that described slow body is arranged to that two rightabouts adjoin each other.
Beam-shaping body for neutron capture treatment the most according to claim 4, it is characterized in that: described cone-shaped include the first diameter, Second bobbin diameter and the 3rd diameter, described first diameter length is 1cm-20cm, the a length of 30cm-100cm of described Second bobbin diameter, described 3rd diameter length is 1cm-50cm, the 80%-100% that density is solid density of the material of described slow body.
Beam-shaping body for neutron capture treatment the most according to claim 1, it is characterised in that: clearance channel is set between described slow body and described reflector to improve epithermal neutron flux.
Beam-shaping body for neutron capture treatment the most according to claim 1, it is characterized in that: described powder sintered equipment is hot-press sintering equipment or discharging plasma sintering equipment, described powder sintering process is hot-pressing sintering technique or discharge plasma sintering process.
Beam-shaping body for neutron capture treatment the most according to claim 7, it is characterized in that: described hot-press sintering equipment includes the powder in heating furnace, the pressue device being placed in described heating furnace, mould, the described mould of loading or powder compact and for controlling the control device that described hot-press sintering equipment normally works, described hot-pressing sintering technique comprises the steps: to fill described mould with appropriate powder or powder compact；Open described hot pressing furnace with preset pressure and temperature parameter；Powder in described mould or powder compact are pressurizeed by mobile described pressue device；Described control device controls described hot-press sintering equipment when normal work；Energising is to sinter in bulk.
Beam-shaping body for neutron capture treatment the most according to claim 7, it is characterized in that: described discharging plasma sintering equipment includes the first electrode, second electrode, it is placed in the conductive die between described first electrode and described second electrode, the impulse current generator of pulse current is provided to described mould, with the pressue device of the pressing means for pressurization with for controlling the control device of described pulse current transmitter and described pressue device, at least one in described first electrode and the second electrode can move, at least one in described first electrode and the second electrode is connected it is thus possible to add the powder being pressed in described mould with described pressue device；Described discharge plasma sintering process comprises the steps: appropriate powder is filled described mould；Powder in described mould is pressurizeed by mobile described second electrode；Opening impulse current generator by control device and produce plasma to be conducted electricity by conductive die, powder particle surface is activated and generates heat；Sintering in bulk.
nullBeam-shaping body for neutron capture treatment the most according to claim 9，It is characterized in that: described discharging plasma sintering equipment farther includes the displacement measurement system of the displacement for measuring pressue device，The atmosphere control system of atmosphere in controlling described mould，Water-cooling system for cooling，The temperature measuring equipment of the temperature in measuring described discharging plasma sintering equipment，Described discharge plasma sintering process farther includes following steps: described control device controls described displacement measurement system to guarantee that described displacement measurement system normally works，Described control device controls described atmosphere control system to guarantee that atmosphere is when normal work in described mould，Described control device controls described water-cooling system to guarantee that described water-cooling system normally works，Described control device control described temperature measuring equipment with guarantee in described discharging plasma sintering equipment temperature when normal work.
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| CN201510222234.5A CN106310540A (en) | 2015-05-04 | 2015-05-04 | Beam shaping body for neutron capture therapy |
| JP2017557373A JP6843766B2 (en) | 2015-05-04 | 2016-04-18 | Beam shaping assembly for neutron capture therapy |
| CN201680022431.5A CN107921273B (en) | 2015-05-04 | 2016-04-18 | Beam-shaping body for neutron capture treatment |
| EP16789264.5A EP3254729B1 (en) | 2015-05-04 | 2016-04-18 | Beam shaping body for neutron capture therapy |
| EP19184558.5A EP3570294B1 (en) | 2015-05-04 | 2016-04-18 | Beam shaping body for neutron capture therapy |
| CN201910602752.8A CN110251847A (en) | 2015-05-04 | 2016-04-18 | Beam-shaping body for neutron capture treatment |
| PCT/CN2016/079568 WO2016177270A1 (en) | 2015-05-04 | 2016-04-18 | Beam shaping body for neutron capture therapy |
| RU2017142120A RU2682972C1 (en) | 2015-05-04 | 2016-04-18 | Applied in the neutron capture therapy beam formation element |
| US15/704,495 US10328286B2 (en) | 2015-05-04 | 2017-09-14 | Beam shaping assembly for neutron capture therapy |
| US16/401,328 US10617893B2 (en) | 2015-05-04 | 2019-05-02 | Beam shaping assembly for neutron capture therapy |
| US16/727,216 US20200188695A1 (en) | 2015-05-04 | 2019-12-26 | Powder sintering device for moderator |
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Cited By (8)
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| CN109411108B (en) * | 2017-08-18 | 2020-06-12 | 南京中硼联康医疗科技有限公司 | Retarder for moderating neutrons |
| CN111494812A (en) * | 2017-08-18 | 2020-08-07 | 南京中硼联康医疗科技有限公司 | Retarder for moderating neutrons |
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| CN110536535A (en) * | 2019-07-12 | 2019-12-03 | 西安交通大学 | A kind of Shu Ping for high-energy particle accelerator |
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| CN113897526A (en) * | 2021-09-26 | 2022-01-07 | 散裂中子源科学中心 | Neutron deceleration composite material |
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