CN103745760B - Gamma ray projector based on full ray laser plasma accelerator - Google Patents
Gamma ray projector based on full ray laser plasma accelerator Download PDFInfo
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- CN103745760B CN103745760B CN201410020590.4A CN201410020590A CN103745760B CN 103745760 B CN103745760 B CN 103745760B CN 201410020590 A CN201410020590 A CN 201410020590A CN 103745760 B CN103745760 B CN 103745760B
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Abstract
The invention provides a kind of small-sized gamma ray projector based on full ray laser plasma accelerator.The radiographic source includes synchronous dual output high power laser system (200), double compressed delay systems (12), laser plasma accelerator (18), particle beam system (24), scattering light focus lamp (27) and particle beams piece-rate system.Wherein, a branch of primary laser pulse is separated and amplified by the laser system (200) so as to produce two beam synchronization high energy laser pulses (10, 11), laser pulse after the amplification of two beams is compressed by double compressed delay systems (12) in time domain and to carry out appropriate delay right to form driving pulse (13) scattering pulse (14), driving pulse (13) produces relativistic electron beam (21) by laser plasma accelerator (18), particle beam system (24) is used to transmit electron beam (21), scattering light focus lamp (27) is used to focus on scattering pulse (14) on electron beam (21) to produce gamma-rays (31), piece-rate system is used to separate above-mentioned electron beam (21) and gamma-rays (31).
Description
Technical field
The present invention relates to a kind of new gamma ray projector implementation.Present invention simultaneously relates to this gamma ray projector in core thing
Manage detection, nuclear battery, gamma ray laser and the medical same position of research, nuclear astrophysics research, nuclear material or radioactive waste
Application in the new manufacture of element.
Background technology
The gamma-ray mode of people's generation at present mainly has following several.
Radio isotope gamma ray projector：Tellurian natural Gamma ray source comes from radioisotopic decay process,
Such as40K（Launch 1.46MeV gamma-rays by capturing electronics）With60Co（Decayed by β to launch 1.17 and 1.33MeV
Gamma-rays）.These gamma ray projectors are widely used in medical treatment（Such as γ knife surgical operations）, non-contact type industrial detection, packaging
Case safety inspection facility etc..But due to the limitation of radio isotope species, gamma-rays photon energy and intensity all can not be effective
Control.
Bremsstrahlung gamma ray projector：Because high energy electron is by another charged particle（Such as atomic nucleus）Slow down and send
Radiation is called bremsstrahlung.This radiation has continuous spectrum, and spectrum peak energy increases as electron energy increases.It is hundreds of
MeV electron beam and solid target（Such as included a tantalum target）Phase separation can produce tens of MeV gamma-rays photon.This radiographic source by
Detected applied to internal structure, and show very high spatial resolution（Some tens of pm magnitude）.But wider power spectrum limitation
The brightness in this source, to there is wider application, also needs to improve the source.
Inverse Compton scattering gamma ray projector：Just as the X ray that high energy electron can be launched in oscillator or rocker, when
For high energy electron with that can produce gamma-rays during laser oscillator phase separation, this process is called inverse Compton process.This γ is penetrated
Line source can be that single energy can also be wide power spectrum according to the difference of electron beam energy spectrum width.The brightness of this gamma ray projector can
With the high several magnitudes of specific activity isotope gamma ray projector.The electronics of current this gamma ray projector accelerates from conditional electronic
Device.Involving great expense for conditional electronic accelerator, it is bulky, limit the application of this gamma ray projector.Using based on sharp
The electron accelerator of light tail field can turn into a revolution of inverse Compton scattering gamma ray projector.
Electronic induction radiates gamma ray projector：This is another synchrotron radiation source.In laser wakefield accelerator, electronics is in quilt
Also by swaying while longitudinal direction accelerates.When electron energy is close to GeV magnitudes, the transverse focusing field of laser tail field is led
The electronics swaying of cause can produce gamma-rays.Because longitudinally being accelerated during electron synchrotron, the source typically has wider power spectrum.
10 can be produced in nearest laser wakefield accelerator experiment7Individual energy is 1 to 7MeV photon.This introduces a collection can after improvement
Have been widely used.
Subject invention
It is an object of the present invention to overcome the limitation of prior art.
More specifically, an object of the invention is to provide a kind of new embodiment of gamma ray projector, the embodiment is relative
Compacter, effective in the gamma ray projector of prior art, cost is relatively low, and operation is easier and has better performance.
It is also an object of the present invention to provide a kind of desktop yardstick of excellent performance, convenient gamma ray projector, for
Basis, medical treatment and commercial Application and research are carried out in small-scale experiment room.
The content of the invention
In order to achieve the above object, gamma ray projector provided by the invention includes：
High power laser system with two cascade amplifiers, the laser system can the beam energy of synchronism output two put
Big laser pulse, laser system are followed by two optical pulse compression devices, for producing the electricity of pulsewidth and energy with optimization
Beamlet driving pulse and gamma ray scattering pulse；
Laser plasma accelerator, driving pulse can produce relativistic electricity in the laser plasma accelerator
Beamlet；
Particle beam system, the particle beam system are used to transmit and focus in laser plasma accelerator to produce
Electron beam；
Light focus lamp is scattered, the scattering light focus lamp is used for the electron beam that scattering pulse is focused on to backpropagation, dissipated
Penetrate pulse and the gamma-rays of collimation is produced due to inverse Compton scattering effect with electron beam interaction；
Particle beams piece-rate system, electron beam in the particle beams piece-rate system be deflected, so as to caused gamma-rays phase
Separation.Compacter compared to gamma ray projector of the prior art, efficient according to the gamma ray projector of the present invention, cost is relatively low, behaviour
Work is easier, and performance is more preferable.
It is preferred that above-mentioned high power laser system includes：
Fore device, the fore device include being used for the oscillator for producing femto-second laser pulse, and for prolonging in time domain
The pulse stretcher according to chirped pulse Optical Amplification Technology (CPA) of primary laser pulse is stretched, fore device is followed by beam splitter will
Pulse after broadening is divided into two beams；
Two parallel be used to amplify two pulses after beam splitting energy cascade amplifier；
Two according to chirped pulse Optical Amplification Technology (CPA) by the pulse shortener of the pulse compression after amplification.
Using chirped pulse Optical Amplification Technology (CPA), laser can produce the pulse of very high energies.
It is preferred that the laser plasma accelerator includes：
The first air chamber filled with mixed gas；
The second air chamber filled with pure helium；
Gas feed channel；And
Gas regulating system.
Due to the high accelerating gradient of laser plasma accelerator, the laser plasma accelerator can be with highly effective
Ground produces high-quality relativistic electron beam.
It is preferred that the laser plasma accelerator includes being used for the device of the second air chamber length of adjustment to adjust electron beam
Energy, occur inverse Compton scattering and caused gamma-ray photon energy so as to adjust electron beam and scattering pulse.
It is preferred that particle beams piece-rate system includes being used for the dipole magnets and particle beams collector for deflecting electron beam.
Advantageously, the gamma-rays is to dissipate the quasi- monoenergetic gamma rays for being about 1% relatively.
The nuclear physics and celestial body thing being applied to according to the gamma ray projector device of the present invention in numerous areas, such as basic science
Reason, medicine, and commercial Application etc..The radiographic source is compacter compared to gamma ray projector of the prior art, efficient, cost compared with
Low, operation is easier, and performance is more preferable.
According to a preferred embodiment, the gamma-rays photon energy range can cover 1MeV to 20MeV sections.
Brief description of the drawings
Fig. 1 is the schematic diagram of gamma ray projector according to embodiments of the present invention；
Fig. 2 is that the gamma ray projector device in Fig. 1 is used for the synchronous double compression-delays for producing driving pulse-scattering pulse pair
The detail view of optical system；
Fig. 3 is the schematic diagram of the two-stage air chamber of the laser plasma accelerator of gamma ray projector device in Fig. 1；
Fig. 4 is the schematic diagram of the laser plasma accelerator of gamma ray projector device in Fig. 1, and the laser plasma accelerates
Device includes the two-stage air chamber in Fig. 3；
Fig. 5 is the schematic diagram that laser tail field accelerates electronics；
Fig. 6 is the schematic diagram of Miniature permanent magnet magnetic quadrapole (PMQ)；
Fig. 7 is the schematic diagram for the particle beam system for including four permanent magnetism magnetic quadrapoles as shown in Figure 6；
Fig. 8 is the schematic diagram of the scattering light focus lamp in Fig. 1 gamma ray projector device；
Fig. 9 A, 9B and 9C show the particle beams piece-rate system of integration, and the particle beams piece-rate system is collected including electron beam
Device and the permanent magnet magnetic dipole for gamma-rays and electron beam to be separated.
Figure 10 is the schematic diagram for producing gamma-rays part in Fig. 1 in gamma ray projector device, and this is based partially on according to the present invention
Laser plasma accelerator obtained by relativistic electron beam inverse Compton scattering and produce gamma-rays.
Embodiment
Gamma ray projector general introduction according to embodiments of the present invention
Fig. 1 is the schematic diagram of gamma ray projector according to embodiments of the present invention.As shown in figure 1, the gamma ray projector device includes
High power laser system 200 is used to produce two synchronous beam high energy laser pulses 13 and 14, and this two pulses passes through compression chamber
15 are compressed and are entered the laser plasma accelerator 18 being arranged in reaction chamber 36 and scattering light focus lamp 27, will hereafter be entered
One step is described in detail.
Because the gamma ray projector device of the present invention employs the structure of optimization, its size can significantly subtract relative to prior art
It is small, thus basis, medical treatment and commercial Application and research can be carried out in the limited laboratory in space.For example, according to the present invention's
It is about 3m × 6m that the gamma-ray gamma ray projector device that energy is 1 to 20MeV, which can be produced, and can be fabricated to overall dimensions, wherein swashing
The size of photosystem 200 is about 3m × 5m, and the overall size for removing remaining device of laser system is about 3m × 1m.On it should be understood that
State size to be not intended to limit the scope of the invention, it is suitably sized that the size of gamma ray projector device is alternatively other.
The high power laser system of synchronous dual output：
In Fig. 1, the oscillator 1 in laser system 200 produces a branch of low-energy laser pulse 2.Put according to chirped pulse optical
Big technology (CPA), this laser pulse 2 broadening in time domain by laser stretcher 3.Stretcher 3 is by a pair of diffraction grating to group
Into this can compensate grating the dispersion of low-energy laser pulse 2 in time domain.Laser pulse 4 and laser arteries and veins after being broadened
Punching 2, which is compared, has wider pulsewidth and relatively low peak power.
Laser pulse 4 is pulse 6 and pulse 7 by the beam splitting of beam splitter 5, and pulse 6 and pulse 7 respectively enter two parallel levels
Join amplifier 8 and 9.Pulse 6 and 7 is exaggerated device 8 and 9 and amplified respectively, becomes high energy pulse 10 and 11.Arteries and veins after the amplification of two beams
Punching 10 and 11 is compressed in double compressor reducers and delay system 12 in time domain.Double compressor reducers and delay system 12 are arranged on compression chamber
In 15, compression chamber 15 is evacuated by vacuum pump system 16 to keep 10-3To 10-4The internal pressure of pa.
As shown in Fig. 2 double compressor reducers 51 and 52 53 and 54 are made up of diffraction grating respectively with compensate laser pulse when
Dispersion on domain.Output pulse 13 and 14 after compressor reducer 51 and 52 have high energy and extremely short pulsewidth so that
Accelerated electron beam 21 can be optimized for respectively in their energy and pulsewidth or produces γ for scattered electron bundle
Ray 31.Delay system 55 and/or 56 is arranged on straight line regulating platform to adjust the delay between pulse 13 and 14, ultrafast light
Electric diode 23 and 29 is to monitor the synchronism of two beam laser, and electronic current inductor 25 is measuring electron beam, and γ
Ray probe 32 is measuring caused gamma-rays.
The two-stage air chamber plasma accelerator of induced ionization injection：
As shown in figure 1, ultrashort, super strong laser pulse 13 is focused on the entrance of two-stage air chamber 18 by off axis paraboloidal mirror 17.Two
First air chamber of level air chamber（Referred to as inject level）It is filled with mixed gas（Such as helium and nitrogen）, the second air chamber（Referred to as accelerate
Level）It is filled with clean gas（Such as hydrogen or helium）.Gas can be fed respectively by gas flow control system 19 with different pressure
Into two-stage air chamber 18.
As described below, in the injection level of air chamber 18, laser pulse 13 excites the Plasma Wake Wave of high intensity, due to
Induced ionization injects mechanism, and the coda wave can capture and accelerate the inner-shell electron of gas.In air chamber 18, laser arteries and veins is driven
Plasma wake field caused by punching has the accelerating field of 1GV/cm magnitudes, a branch of electron beam 21 after level preaceleration is injected
It is further accelerated in air chamber accelerating stage to the energy with 1GeV magnitudes.The driving laser of transmission is porose by one side center
Speculum 20 is led into recycling box 22, and the recycling box 22 includes photodiode 23 and laser absorption device.
When high power laser system of the plasma accelerator with the dual output according to the present invention, particle beam system
When system, scattering light focus lamp and particle beams piece-rate system are combined, it will have excellent performance.It is but this including equipped with mixed
The plasma accelerator for closing the first air chamber of gas and the second air chamber equipped with pure helium also can be with other kinds of laser
It is combined for producing high energy electron beam.
Particle beam system, scatter light focus lamp and particle beam separator：
The electron beam 21 that plasma accelerator 18 exports is transferred to scattering light focus lamp by particle beam system 24
At 27, these devices are all arranged in reaction chamber 36.As described below, electron beam 21 is by the magnetic quadrupole of particle beam system 24
Son is clashed after focusing on the laser pulse 14 focused on by scattering light focus lamp 27, and gamma-rays is produced due to inverse Compton scattering
31。
After the central small hole by scattering light focus lamp 27, electron beam 21 is by the deflection magnetic of a generation magnetic dipole
Iron 33 deflects and separates with gamma-rays 31 and collected by particle beams collector 34, and gamma-rays 31 projects from reaction chamber 36, into
For adaptable gamma-rays.
Laser plasma accelerator is described in detail：
Two-stage air chamber：
Fig. 3 is the schematic diagram of two-stage air chamber 18.The two-stage air chamber is used for effective electronics capture in laser coronal region and added
Speed, including injection level 61 and accelerating stage 62.As shown in figure 4, this two-stage air chamber is placed on the middle of reaction chamber 36.In pulse
Laser beam 13 after being compressed in compression chamber 15 is focused on the porch of injection level by off axis paraboloidal mirror 17.
Mixed gas 65 is filled with injection level 61, such as 98% helium and 2% nitrogen, gas are filled by gas feed-in
Put 63 and be fed to injection level from gas flow control system 19.Accelerating stage 62 is filled with clean gas 66, such as hydrogen or helium, gas
Accelerating stage is fed to from gas flow control system 19 by gas feeding equipment 64.Length-adjustable accelerating stage is driven by electric machine structure 68
Dynamic bellows structure 67 is formed.Reaction chamber 36 is evacuated by vacuum pump system 37 to keep air pressure inside as 10-3To 10-4
Pa.
Physical process description：
Fig. 5 describes electronics capture and the physical process 100 accelerated in coda wave field excitation and coda Q values, and coda Q values are by height
Strength laser is transmitted and formed in the neutral gas of injection level 61.In Fig. 5, above 101 show that plasma electron is close
The evolution of degree, below 102 show laser excitation coda wave indulge field.
As shown in the center section 100 in Fig. 5, the outer-shell electron of helium and nitrogen（At most+5 valencys are arrived in ionization）In laser arteries and veins
The forward position of punching（Light intensity 1.5 × 1016W/cm2）Ionized completely, plasma electron, its side are formed in the periphery of laser pulse
Boundary is represented by choice refreshments line 103.Due to two electronics of innermost layer of nitrogen（K shells）It is higher than 1 × 10 in laser intensity19W/cm2
It can be ionized, inner-shell electron can be only ionized near the peak value of laser pulse 13, for normalizing laser field a0≈
0.855×10-9I1/2[W/cm2]λL[μm]=2, wherein I [W/cm2] it is light intensity, λL[μm] is optical maser wavelength, laser pulse it is strong
Degree distribution is represented by thick dotted line 108.In Figure 5, in 101 above, heavy line 109 represents nitrogen degree of ionization（Axially each nitrogen
The electron number of gas atom ionization）Evolution.The zone boundary of two electron ionizations of nitrogen hypostracum is represented by choice refreshments line 104.
The plasma electron included in border 103 is by with the theory of relativity intensity a0The radiation of ＞ ＞ 1 laser pulse 13
Pressure（Pondermotive force）Push open and form one layer thin of ball shape electric shell.What the shell was wrapped in behind laser pulse usual is claimed
For the spherical ions region of vacuole 105.It is 10 in electron density18cm-3Plasma in, this separation of charge field forms
The strong longitudinal electric field 110 of 100GV/m magnitudes, this electric field are more three orders of magnitude greater than the acceleration fields in conventional radio frequency accelerator.
In vacuole 105, electronics also undergoes extremely strong focousing field accelerated while.Therefore, once electronics 21 is captured by vacuole, they
With regard to efficiently can persistently be accelerated to the energy with 1GeV magnitudes, accelerating length is controlled by dephasing length.
Close to vacuole center when above-mentioned nitrogen inner-shell electron is ionized, tail field potential is maximum herein, and repel
Laser pondermotive force is minimum value.Unlike the free electron of preionization, close to the axial direction of vacuole after inner electron ionization
It is moved to vacuole afterbody.Vacuole afterbody has the tail field potential of minimum, and electronics can be captured here, as shown in electron trajectory 106.
And the electronics shown in electron beam trace 107 is because the time being ionized is more early, and deviate axially, so having skidded off the gesture of tail field
Well.The mechanism of this electronics capture injection is referred to as induced ionization injection.Due to when capture occurs electronics close to vacuole axis,
The swaying of electronics is weaker.The theoretical calculation injected according to induced ionization, being capable of injected electrons quilt at laser field peak value
Ionization, minimum laser intensity is by formulaProvide, whereinIt is the phase of coda Q values phase velocity
To by the factor, βpIt is the phase velocity of plasma wave.For parameter γpFor=33, the laser intensity for producing electron injection is necessary
For a0≥1.7.One-dimensional PIC simulative displays, because beam loading effect and phase space injection line of demarcation initially inject electrical losses
Effect, when mixed gas length is Lmix≈1000λ0, plasma density ne=0.001nc（I.e. 1.7 × 1018cm-3）, nitrogen
Gas concentration αN=1%, laser intensity a0=2, pulsewidth c τ0≈15λ0When maximum injection number of electrons（I.e. saturation when electron number
Mesh）Probably it is Nemax~5 × 106μm-2, wherein λ0It is optical maser wavelength, ncIt is plasma critical density（It can be expressed as）.Work as αNkpLmixWhen≤2, injection number of electrons is Ne[μm-2]~8 × 107αNkpLmix(ne/nc)1/2.It can dissipate all directly proportional with mixed gas length and nitrogen gas concn.According to a0=2 two dimension
PIC is simulated, and injection electron beam can be dissipated for δ E/E=0.02 [%] (Lmix/λL)(ne/1017cm-3)-1/2, horizontal normalized emittance
It can be estimated as
For a0>=2 vacuole（Or emptying）For domain, the cavity shape that is arranged completely due to electronics can by from
The Lorentz force of bulbec and the pondermotive force of laser pulse balance each other to determine, the radius R of vacuoleBCan substantially by
Provide, wherein kp=(4 π rene)1/2It is plasma-wave number, kpBy plasma density n of the axial direction without disturbanceeDetermine, re=
e2/mec2=2.818 × 10-13Cm is classical electron radius, and e is single electron electricity, meIt is single electron quality, c is light in vacuum
Speed.Acceleration fields EzBy formula Ez/E0=(1/2) α kpRBProvide, wherein E0=mc ωp/e≈96[GV/m](ne/1018[cm-3]
)1/2, α is the coefficient for considering beam loading effect and its gap of simulation and theoretical calculation and adding.Due to dephasing effect, electronics can
The ceiling capacity of acquisition is by formula Δ γmax=Wmax/mec2≈(2/3)ακselfa0(nc/ne) provide, whereinIt is due to relativistic laser pulse bootstrap group velocity
And the modifying factor introduced.The group velocity β of laser nondimensionalizationg=vg/ c relativistic factor isWherein γg0=ωL/ωpIt is to work asWhen linear group velocity
Relativistic factor.The dephasing length L in bootstrap vacuole domaindpByProvide.If
The electron energy for wanting laser plasma accelerator to accelerate will reach prescribed energy Eb, important parameter below must is fulfilled for：
Plasma train operation density：
Accelerating length is consistent with dephasing length：
Pulse depletion length caused by being corroded due to laser pulse forward position：
Laser pulse has the pulsewidth for causing dephasing length to be more than pulse depletion length：
The laser facula radius of matching：
Wherein
Correspondingly, the laser power of matching is：
Required pulsed laser energy is UL=PLτL。
Assuming that beam loading efficiency is（It is σ that plasma wave energy, which is defined as, by root mean square radiibElectricity
The ratio that beamlet absorbs）, then the acceleration fields for having loaded electron beam areWherein EMIt is when not having beam loading
Acceleration fields.Therefore load power expression formula is
By plasma density neExpression formula is brought into, and load power can be calculated as
Acceleration electricity is QbElectron cloud to energy be EbField discount factor α by formula α2+Cα3/2- 1=0 is obtained, wherein
The detailed description of particle beam system, reaction optical system and particle beam separator
Particle beam system：
The caused particle beams needs to transmit and focus on scattering light focus lamp 27 from laser plasma accelerator 18
In focus, the focusing of the particle beams is provided by the particle beam system 24 of short focus.Two-dimentional Haier's becker type shown in Fig. 6
(Halbach-type) field gradient of permanent magnetism magnetic quadrapole (PMQ), the field gradient can be expressed asWherein
BrIt is sophisticated field intensity, riIt is radius of bore, r0It is PMQ outer radius.For ri=2.5mm, permanent magnet rank are N50 Nd-
Rare earth element magnet (the Nd of Fe-B types2Fe14B), Br=1.45T, it is B '=1160 [T/m] (1-2.5 that can obtain field gradient
[mm]/ro).Fig. 6 illustrates the magnetic quadrapole being made up of 12 pieces of Halbach type (Halbach-type) permanent magnets 71 and 72
(PMQ) 76, magnetic quadrapole includes being used for the outer cover 73 and 74 and support 75 for supporting positioning.The magnetic quadrapole includes four wedge-shaped footpaths
To permanent magnet 71（Material is Nd2Fe14B or SmCO etc. has the material of high remanent magnetization）, arrow in the direction of magnetization such as figure
It is shown.The connection of the peripheral magnetic line of force is completed by eight wedge-shaped permanent magnets 72.This four wedge-shaped magnets the last 71 to play a major role
Strongly to the central suction of quadrapole, its mechanical precision and field accuracy can be by inserting permanent magnetism magnetic quadrapole（PMQ）Center
Non magnetic drum 73 and the shells 74 of PMQ peripheries realize.
As shown in fig. 7, particle beam system 24 includes two to four permanent magnetism magnetic quadrapoles being arranged in chamber shell 86
(PMQ), such as a pair（Referred to as FD）, three（Referred to as FDF）, or four (FFDD) 76-79.Each permanent magnetism magnetic quadrapole (PMQ)
The mobile system 80-83 controlled along the lengthwise position of electron beam axis by computer come adjust optimization, the mobile system include by
Stepper motor driven vacuum linear kinematics manipulator.The collimation of magnetic quadrapole (PMQ) can accurately be ensured by guide track system 85.
React optical system：
Fig. 8 shows second half structure of reaction chamber 36.The scattering passed out from above-mentioned compression-delay optics cavity 15
Laser pulse 14 reflexes to the scattering light focus lamp 27 with central small hole by the injection speculum 26 with beam hole（Such as ball
Face mirror or off axis paraboloidal mirror）On, then the focal point for focusing on scattering light focus lamp is reflected by scattering light focus lamp 27, and herein
Focal point bumps against with the electron beam 21 that particle beam system 24 is sent and inverse Compton scattering effect occurs and produces gamma-rays.
After being reacted with electron beam 21, scattering pulse 14 exports reaction chamber 36 by another speculum 28 for having central small hole, enters
Recycling box 30, recycling box 30 include photodiode 29 and for absorbing the absorber of the laser pulse of transmission.
Particle beam separator：
As shown in Fig. 9 A, 9B and 9C, the path of the electron beam 21 after the scattering permanent magnet made of material NdFeB（Grain
Beamlet separator 33）Dipole field bending, and collected by the copper particle beams collector 34 with water cooling element 94.Permanent magnetism
Magnetic dipole (PMD) 33, such as Halbach type (Halbach-type) permanent magnetism magnetic dipole, including 8 blocks of NdFeB materials
Wedge-shaped magnets, the direction of magnetization of wedge-shaped magnets is as shown in the arrow in Fig. 9 B.Halbach type (Halbach-type) permanent magnetism
The dipole field B of magnetic dipoleDBy BD=Brln(ro/ri) provide, wherein BrIt is sophisticated magnetic field intensity, riIt is PMD bore hole half
Footpath, r0It is PMD outer radius.For ri=5mm, ro=100mm, permanent magnet rank be N50 NdFeB materials, Br=1.45T,
It is B that dipole field, which can be obtained,D=4.34T.The mechanical precision and field accuracy of permanent magnetism magnetic dipole 33 can be by being inserted in
The shell 92 of non magnetic drum 91 and the PMD periphery at PMD centers is realized.The path of electron beam 21 is by permanent magnetism dipole field 33
Collected after bending by copper particle beams collector 34, and gamma-rays 31 is projected by a narrow gamma-rays perforation hole 93.Gamma-rays
Perforation hole 93 processes the edge of the permanent magnetism magnetic dipole bore hole in particle beams collector 34.For BD=4.34T（ro/ri=
20）Magnetic dipole so that deflection distance is d ≈ 2riThe permanent magnetism magnetic dipole length of [mm] is by LPMD[(the r of [cm]=10i/
3.26mm)(Eb/1GeV)]1/2Provide.In copper particle beams collector, because electron beam in radiation length is X0=1.44cm
Place is by the ratio of electromagnetism cascading off-energyThe electronics that energy is 1GeV is 10X in length0（About
15cm）, a diameter of 7X0（About 10cm）Copper billet in can lose almost all of kinetic energy.Permanent magnetism magnetic dipole and the particle beams
Collector is cooled down by water cooling element 94.
Gamma-rays device：
As shown in Figure 10, above-mentioned gamma-rays device include being installed on laser plasma accelerator 18 in reaction chamber 36,
Particle beam system 24 and reaction Optical devices, reaction chamber 36 keep its intracavitary pressure by the vacuum pumping of vacuum pump system 37
For 10-4The magnitude of pa.Particle beam separator 33 and collector 34 are connected to the electron beam 21 of reaction chamber 36 and going out for gamma-rays 31
At mouthful.In the embodiment of the gamma ray projector according to the present invention, all parts of gamma-rays device are all assembled in track structure 35
On, track structure 35 includes both ends disk 40 and 41, four supports 42 and four guide rails 43 for support member, part
Horizontal and vertical collimation can easily be adjusted and accurately be limited.As shown in Figure 4 and Figure 8, guide rail structure 35 both ends
Disk 40 and 41 is supported by vacuum bar 39 by lathe 38, can so prevent guide rail structure 35 in 36 rarefied mistake of reaction chamber
Deformed upon in journey.
The design of inverse Compton scattering gamma ray projector
The quantrm electrodynamics result that design based on inverse Compton scattering gamma ray projector is interacted by photon-electron
To realize, for example, the Klein-Nishina of the photon provided in quantrm electrodynamics and single electron lowest-order differential scattering
Equation.It is in an energy（For given laser wavelength lambdaL[μm],）Laser photon with
In the Compton scattering of an electronics in electron beam, maximum scattering photon energy byProvide, wherein γe=
Eb/mec2It is that energy is EbElectron beam relativistic factor, mec2≈ 0.511MeV are the static mass-energy of electronics, the factorUnder laboratory reference system, the differential scattering of Compton scattering is
Wherein κ=Eγ/EγmaxBe by the scattered photon energy after maximum photon energy normalized, reIt is classical electron radius.Under laboratory reference system, the scatteringangleθ of photon by
Provide.Differential scattering is integrated in the range of 0≤κ≤1, the total scatter cross-section for obtaining Compton scattering is
This total scatter cross-section is in beam energy limit EbThomson cross section is converted into when → 0
As Δ κ=Δ Eγ/EγmaxDuring ＜ ＜ 1, photon energy range Eγmax-ΔEγ≤Eγ≤EγmaxFraction scattering section be
Photon in this energy area is all by forescatering a to semi-cone angleIn the range of.It is right
In with laser pulse in horizontal plane（X-plane）Interior is in αintFor the electron beam of angle phase separation, brightness（For representing that unit scatters
Electron beam and the probability of laser beam collision in the cross-sectional unit time）It is represented by L [mb-1s-1]=NeNLfL/ 2 π Σ, wherein NeIt is
Number of electrons in electron beam, NLIt is the photon number of single beam laser, fLIt is the repetition rate of laser pulse, Σ（I.e. laser beam and
The overlapping area of electron beam）It is given by
Wherein σexAnd σeyIt is root mean square (r.m.s.) size in electron beam horizontally and vertically direction respectively, σezIt is longitudinal electricity
The r.m.s. Shu Changdu, σ of beamletLxAnd σLyIt is r.m.s. spot size of the laser beam in horizontally and vertically direction, σLzIt is laser beam
R.m.s. pulse length in longitudinal direction.Gamma-rays is efficiently produced by the way of head-on collision, so electron beam and laser interfascicular angle
Elect α asint=0.Adjust particle beam system 24 and scattering light focus lamp 27 causes σex≈σey≈σLx≈σLy, then illuminometer reach
Formula turns toWherein wintIt is the laser facula radius at reflecting point.Take Ne=1.6022 × 1010(Qe/
1nC),Wherein QeIt is electron beam electricity, ULS=PLSτLSIt is that peak power is
PLS, pulsewidth τLSScattering pulse energy, then brightness can be calculated as
Wherein IintIt is the scattering pulse light intensity after focusing at reflecting point.Therefore can dissipate for Δ κ=Δ Eγ/Eγmaxγ penetrate
Line photon flux can be estimated as
ΔNγ[s-1]=L Δ σ ≈ 1 × 10-14Δσ[mb]fL[s-1]Qe[nC]IL[Wcm-2]τ[fs]λL[μm]。
The embodiment of the gamma ray projector accelerated based on full ray laser plasma
It is 1MeV to 20MeV described above is the photon energy studied for nuclear physics（Regulation electron energy is 200MeV
To 930MeV）The gamma ray projector based on full ray laser plasma accelerator.In this gamma ray projector, driving pulse and dissipate
Pulse is penetrated all from running on 800nm wavelength（That is photon energy）High power laser system in obtain.This γ
It is 2.5MeV that all parameters of radiographic source, which are provided to obtain photon energy,（Example A）, 5MeV（Example B）, 10MeV（Example C）,
15MeV（Example D）And 20MeV（Example E）And design, the beam energy needed for it is respectively Eb[MeV]=326,
461,654,802,928。
It is Q that this laser plasma accelerator, which can provide electricity,b=0.5nC, the long σ of beamezFor the electronics of 10 μm of magnitudes
Beam.A branch of driving pulse pulse 13 is focused at chamber inlet after the injection of compressor reducer 51.Corresponding to laser intensity I=5.5
×1018Wcm-2, the normalized laser field strength of driving pulse is a0=2.Bootstrap of this laser pulse in air chamber is propagated
It is required that group velocity modifying factor κself=1.19, and with the spot radius R of matchingm≡kprm=3.2.For electron beam half
Footpath is kpσb=1 situation, load power QbCaused tail field discount factor α can be by formula α2+Cα3/2- 1=0 is calculated.For reality
Example A to E, parameter is respectively C=9.7, and 8.2,6.9,6.2,5.8, α=0.213,0.237,0.264,0.281,0.293.
Therefore laser plasma accelerator major parameter is as described below：
(1) beam energy Eb[MeV]=326,461,654,802,928
(2) plasma density n is rune[1017cm-3]=9.2,7.3,5.7,4.9,4.5
(3) accelerating length Lacc[mm]=24,34,50,61,72
(4) laser pulse pulsewidth τ needed forL[fs]=43,49,55,59,62
(5) the laser facula radius r of matchingm[μm]=18,20,23,24,26
(6) the laser peak power P of matchingL[TW]=41,52,66,77,85
(7) driving pulse energy UL[J]=1.78,2.56,3.68,4.55,5.31
In example A to E, for inverse Compton scattering, the factorRespectively a=
0.9923,0.9892,0.9847,0.9813,0.9784.Adjustment focusing system 24 causes electron beam to reach scattering laser 14 and focus on
Horizontal root mean square (r.m.s.) size at point is set as σb=25 μm.It is w that scattering light pulse, which is focused onto spot radius,int=
25 μm, so as to the electron beam of backpropagation with angle [alpha]int=0 is overlapping.In order to suppress Relativistic Nonlinear（Such as laser with
Video stretching and higher hamonic wave caused by non-linear Compton scattering when electron beam interacts）, the scattering laser of focusing
Pulse strength must be set below Iint~1018Wcm-2（It is P to control scattering light pulse peak powerLS≈10TW）.Tune can be passed through
Another whole compressor reducer 52, so as to adjust scattering light pulse to control photon flux.Gamma-ray important parameter is as described below：
(1) total scatter cross-section σtotal[mb]=660,658,655,653,651
The fraction scattering section of (2) 1% power spectrum bandwidth
Δ σ [mb]=9.80,9.77,9.73,9.69,9.66
The scattering cone angle of (3) 1% power spectrum bandwidth
θ [μ rad]=313,222,157,128,111
(4) scattering pulse peak power PL[TW]=10
(5 scattering pulse pulsewidth τLS[fs]=250
(6) scattering pulse energy ULS[J]=2.5
(7) spot radius w after scattering pulse focuses onint[μm]≈25
(8) light intensity I after scattering pulse focuses onint[Wcm-2]≈1×1018
(9) brightness L [mb-1s-1]≈106fL
(10) maximum photon ENERGY Eγmax[MeV]=2.5,5,10,15,20
(11) power spectrum bandwidth deltaf κ=Δ Eγ/Eγmax=0.01
(12) total photon flux Nγ[109fL]≈0.660,0.658,0.655,0.653,0.651
The fraction photon flux Δ N of (13) 1% power spectrum bandwidthγ[107fLs-1]≈0.980,0.977,0.973,0.969,
0.966
Generally speaking, under Desktop Dimensions（Such as, the reaction chamber of about 3m length）, synchronously provide 5.3J driving pulse arrive
Laser plasma accelerator and 2.5J scattering pulse is provided to reacting Optical devices to carry out the lose-lose of inverse Compton scattering
Go out high power laser system provide can produce energy be 1 to 20MeV, the flux of 1% bandwidth be~107fLs-1Photon
Gamma ray projector.The gamma-rays every 1% that the standard high power laser system that one output is 100TW levels, repetition rate is 10Hz provides
Bandwidth has 108s-1The flux of magnitude.More preferably, such as being exported with several joules of levels for coherent optical-fiber laser system weighs with 1kHz
Every 1% bandwidth of gamma-rays that high repetition frequency, the high power laser system of complex frequency provide has 1010s-1The flux of magnitude.
Table 1 summarizes example A to E laser plasma accelerator and the major parameter of Compton scattering.
Gamma ray projector example of the table 1 based on full ray laser plasma accelerator
Claims (9)
1. a kind of gamma ray projector, including：
Dual output high power laser system (200), the laser system (200) includes twin-stage connection laser amplifier (8,9), described
Laser system (200) be used for primary laser pulse is separated and amplified be generated synchronously with two beam high energy laser pulses (10,
11)；
Double compression-delay systems (12), double compression-delay systems (12) include diffraction grating to (51,52) and delay light
Learn lens set (55,56), wherein, the exaggerated laser pulse (10,11) of two beam by diffraction grating to (51,52) when
Compressed on domain and carry out appropriate delay by postponing optical mirror slip group (55,56) to be formed respectively with suitable its peak work
Rate, pulsewidth and the driving of delay laser pulse (13) and scattering pulse (14)；
Laser plasma accelerator (18), the driving laser pulse (13) is in the laser plasma accelerator (18)
Produce the relativistic electron beam (21) with appropriate light beam parameters；
Particle beam system (24), the particle beam system (24) are used to transmit the laser plasma accelerator
(18) caused electron beam (21) in, and the electron beam (21) is focused on so that the electron beam (21) reaches suitable beam chi
It is very little；
Light focus lamp (27) is scattered, the scattering pulse (14) reflection is focused on the scattering by the scattering light focus lamp (27)
The focal point of light focus lamp (27), and bump against in the focal point of the scattering light focus lamp (27) with the electron beam (21) to produce
Raw gamma-rays (31), wherein the gamma-rays photon energy range can cover 5MeV to 20MeV sections；And
Particle beams piece-rate system, the particle beams piece-rate system are used for the electron beam (21) and the gamma-rays (31) point
From；Wherein
The laser plasma accelerator (18), particle beam system (24) and scattering light focus lamp (27) are assembled in track
With the mini-system of formation entirety in structure (35).
2. gamma ray projector according to claim 1, it is characterised in that the laser plasma accelerator (18) includes：
The first air chamber (61) filled with mixed gas；
The second air chamber (62) filled with clean gas；
Gas feed channel；And
Gas regulating system.
3. gamma ray projector according to claim 2, it is characterised in that the laser plasma accelerator (18) includes using
In the device for the length for adjusting second air chamber (62).
4. gamma ray projector according to any one of claim 1 to 3, it is characterised in that the particle beams piece-rate system bag
Include the dipole magnets (33) and particle beams collector (34) for deflecting electron beam (21).
5. gamma ray projector according to any one of claim 1 to 3, it is characterised in that the gamma-rays is that energy is
1MeV to 20MeV photon beam.
6. gamma ray projector according to claim 2, it is characterised in that helium and nitrogen are housed in first air chamber (61)
Mixed gas, pure helium is housed in second air chamber (62).
7. gamma ray projector according to claim 1, it is characterised in that be provided with the gamma ray projector two recycling boxes (22,
30), it is respectively provided with described two recycling boxes and absorbs the driving laser pulse (13) and the scattering pulse (14)
Laser absorption device.
8. gamma ray projector according to claim 7, it is characterised in that be provided with photoelectricity in described two recycling boxes (22,30)
Diode (23,29), the photodiode (23,29) are used to monitor the driving laser pulse (13) and scattering pulse (14)
Synchronism.
9. gamma ray projector according to claim 1, it is characterised in that the particle beam system (24) includes 2~4
Permanent magnetism magnetic quadrapole (PMQ), the permanent magnetism magnetic quadrapole (PMQ) include wedge-shaped permanent magnet (71,72) and for supporting
The drum (73) and shell (74) of positioning.
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| CN104001270B (en) * | 2014-05-07 | 2016-07-06 | 上海交通大学 | Extrahigh energy electron beam or photon beam radiation treatment robot system |
| CN104283106A (en) * | 2014-10-23 | 2015-01-14 | 中国工程物理研究院激光聚变研究中心 | Radiation source generation system based on stacked chirp pulse sequence |
| CN104283107B (en) * | 2014-10-23 | 2017-03-08 | 中国工程物理研究院激光聚变研究中心 | Radiation source generation system based on pulse period property phase-modulation |
| CN104394642B (en) * | 2014-12-07 | 2017-03-08 | 湖南科技大学 | Laser plasma resonance body X source |
| NL2016110A (en) * | 2015-03-03 | 2016-09-30 | Asml Netherlands Bv | Radioisotope Production. |
| EP3371814B1 (en) | 2015-11-06 | 2019-09-18 | ASML Netherlands B.V. | Radioisotope production |
| WO2020089454A1 (en) * | 2018-11-02 | 2020-05-07 | Technische Universiteit Eindhoven | Tunable source of intense, narrowband, fully coherent, soft x-rays |
| CN111326947B (en) * | 2020-03-04 | 2021-05-25 | 上海交通大学 | Laser plasma optical device and method for generating ultrashort and ultrahigh mid-infrared pulse |
| CN112689370B (en) * | 2020-12-29 | 2023-03-24 | 清华大学 | Gamma ray source device based on electron linear acceleration |
| CN113514462B (en) * | 2021-04-26 | 2023-05-23 | 浙江师范大学 | Device and method for capturing fine structure of differential scattering cross section of product |
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| US5789876A (en) * | 1995-09-14 | 1998-08-04 | The Regents Of The Univeristy Of Michigan | Method and apparatus for generating and accelerating ultrashort electron pulses |
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