CN205751548U - Superlaser gamma-ray source based on micro-dimension near critical density plasma - Google Patents
Superlaser gamma-ray source based on micro-dimension near critical density plasma Download PDFInfo
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- CN205751548U CN205751548U CN201620703248.9U CN201620703248U CN205751548U CN 205751548 U CN205751548 U CN 205751548U CN 201620703248 U CN201620703248 U CN 201620703248U CN 205751548 U CN205751548 U CN 205751548U
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Abstract
The utility model discloses a kind of superlaser gamma-ray source based on micro-dimension near critical density plasma, including vacuum target chamber system and the composite construction target that is arranged on described vacuum target chamber system memory, described composite construction target includes target frame and is arranged on the metal tantalum post of target frame side, it is coated with the hydrocarbon layer of low-density away from described metal tantalum post one end at described target frame, it is provided with closed cavity between described metal tantalum post and described target frame, the hydrocarbon layer thickness of described low-density is 10 μm, and average density is 5mg/cm3, described target frame is nonmetal making.This utility model other laser gamma-ray sources compared to existing technology are compared, and have that Source size is little, source brightness high, low cost and other advantages.
Description
Technical field
This utility model relates to a kind of superlaser gamma-ray source based on micro-dimension near critical density plasma, it
The fields such as high-energy-density physics, materials behavior detection and treatment of cancer can be applied to as high-performance gamma-ray source.
Background technology
Tightly focused short pulse rushes high-power electron beam can produce pulsed gamma-ray source with the interaction of high Z metal material,
This source has bulk little (about some tens of pm), divergence little (milliradian magnitude), energy height (photon energy is up to MeV)
Etc. advantage, thus have the hugest application prospect in the following areas: 1) positron generation；2) high Z elemental metallic material photograph,
Detection low Z materials bulk properties.The research of this novel ultrafast tightly focused pulsed gamma-ray source causes countries in the world science
The great interest of family.
It is generally believed that ultra-intense laser and near critical density plasma interact can produce the high energy electricity of large charge amount
Son bundle.Electron beam produced by laser and near critical density plasma is injected in high Z metal conversion body, thus produces height
The gamma-ray source of brightness.
In first technology [1]: use the small size supersonic nozzle jet through particular design can produce near critical density
Plasma.Such as, for the nozzle of diameter 0.5 millimeter, when the back pressure of gas is 300-400bar, the helium density of ejection
It is 1021/cm3 , after full ionization, corresponding plasma density is 2 × 1020/cm3.Small size supersonic nozzle ejection helium is complete
Plasma density after ionization is close to critical density.This nozzle can be operated under high vacuum environment safely, will not give whirlpool
The load that wheel molecular pump is the highest is in order to avoid damaging turbomolecular pump.The density of the critical density plasma that nozzle produces is more equal
Even, but also there are the gas distribution structures such as several distinct disadvantage, mainly nozzle complicated, and system is huge, is unfavorable for answering of some occasion
With.Even additionally, small size nozzle, the size of the near critical density plasma of formation is the biggest, for several millimeters.France
Scientist Y. Glinec et al. is by pulse width 30fs, and energy is that the laser light incident of 1.3J is to (complete on 3mm supersonic speed jet target
Plasma density after ionization is 7.5 × 1018/cm3), focal spot size is 18 μm, it is thus achieved that the quantity of electric charge is that 1.6nC(energy is big
In 2MeV) high-power electron beam, be injected in the tantalum post that thickness is 2.5mm, tantalum post is placed on after nozzle at 3mm.Finally
The maximum photon energy obtained can be more than 140MeV.
In first technology [2]: be controlled plasma certainly by the parameter of regulation prepulsing or spontaneous amplification radiation
The mode that body expands can also produce the near critical density plasma with certain density level bands scale length.Yogo et al. proves to adopt
With the mode adjusting Pockers cell adjust spontaneous amplification irradiation duration scope 0.5-5ns can produce near critical density etc. from
Daughter.Such as, laser power density is 1.5 × 1019W/cm2, spontaneous amplification radiant intensity contrast at 10ps before main pulse
It is 2 × 105Time, spontaneous amplification incident to the Kapton of 7.5 μ m-thick can produce high density 2 × 1022/cm3
Plasma.The Chen Hui of U.S.'s lawrence livermore laboratory, using power density is 1012- 1014W/cm2Prepulsing is straight
Connect and act on the thick golden dish target of 1mm, experiment creates the Pre-plasma of length of the scale 20-50 μm.Laser main pulse and
After high energy electron after its interaction enters gold dish target inside, final generation energy is the gammaphoton of tens of MeV.But,
Plasma density produced by this technology is the most higher, and density is about 10 times of critical density, is unfavorable for producing space
The high-power electron beam that the angle of divergence is little, is the most just unfavorable for controlling the bulk of gamma-ray source.
In first technology [3]: use ns long pulse ablation block foam.It is generally adopted by 2 frequencys multiplication or 3 frequency multiplication ns neodymium glass
Glass laser carrys out ablation block foam material to produce near critical plasma.Restraint even cunning for example with multi beam through KPP three times
Frequency laser incidence C15H20O6In foam, a diameter of 2.5mm of foam target, a length of 500 μm.Average often bundle laser energy is at 200-
400J, pulse length is 3ns, and the plasma electron temperature obtained according to local thermal balance model (LTE) is at about 1.3keV.
For the mode of ns long pulse ablation block foam, the bore of light beam is relatively big, thus required ns laser energy is the biggest.
Above-mentioned three kinds of near critical density plasmas formed in first technology are not oversize, it is simply that density is too high,
It is unfavorable for laser stable transmission wherein, and then causes being unfavorable for that producing high brightness tightly focused short pulse rushes gamma-ray source.
Utility model content
The purpose of this utility model is to provide a kind of superlaser gal based on micro-dimension near critical density plasma
Horse radiographic source.
This utility model is achieved through the following technical solutions:
Superlaser gamma-ray source based on micro-dimension near critical density plasma, including vacuum target chamber system and set
Putting the composite construction target at described vacuum target chamber system memory, described composite construction target includes target frame and is arranged on target frame one
The metal tantalum post of side, is coated with the hydrocarbon layer of low-density, at described gold at described target frame away from described metal tantalum post one end
Belong to and be provided with closed cavity between tantalum post and described target frame.In this utility model, the hydrocarbon layer thickness of described low-density is preferential
Being 10 μm, average density is preferably 5mg/cm3, described target frame is nonmetal making.
In this utility model, before laser main pulse arrives, laser pre-pulse is by deep for the skin that becomes at the hydrocarbon layer of low-density
Absorbed in a large number, by mode ablation ionization materials such as impact absorption and parameter absorptions in Du.This utility model use ultra-thin
The hydrocarbon layer of low-density, owing to the average density of foam is relatively low, therefore ablation velocity is high.Before main pulse arrives, the persistent period is
Ablation wave produced by the laser pre-pulse of nanosecond order, by the ultra-thin abundant ionization of hydrocarbon layer, forms plasma.Whole hydrocarbon
Layer material, under the effect of ablation wave, is nearly all heated to the temperature of KeV.Plasma at such high temperatures, will be to low close
Spend the vacuum expansion before and after hydrocarbon layer.Plasma density after expansion is close to critical density and enters target frame and metal tantalum post institute
The confined space formed.Therefore one section of small size near critical density plasma can be formed before metal tantalum post.
Laser main pulse arrive after, by with expand after near critical density plasma interact.Due to laser master pulse
Rush power density more than the Theory of Relativity self-induced transparency threshold value.Laser beam will occur relativistic self focusing and pondermotive force self-focusing.Gauss
When laser beam transmits in the plasma, electronics is radially arranged by the pondermotive force of laser from zone line, forms plasma
Passage.In plasma channel, owing to electronics is pushed open by pondermotive force, form quasi-static radial direction separation of charge field, electric field side
To for radially.Backflow electronics along conduit wall will produce quasi-stationary poloidal magnetic field.Relativistic Electron is by quasi-static electomagnetic field
Being strapped in also front motion vertically together with laser in plasma channel, electronics is laterally circling round with frequencies omega p/2 simultaneously
Vibration.Resonantly positive energy exchange between laser and electronics, electronics is surfing in laser field, and the electronics with appropriate phase will constantly
Mean oscillatory energy is extracted from laser field.After experiencing many subresonances, electronics will obtain the highest energy gain, forms collimation
The high-power electron beam of large charge amount, the mean temperature of electron beam is up to several MeV.
This collimation high-power electron beam subsequently enters in the metal tantalum post after target frame, is converted to gamma ray by bremsstrahlung
Photon.Photon energy is main in MeV magnitude.In view of quasi-static electomagnetic field constraint effect, the space divergence of incident beam
Angle is the least, such that it is able to produce the gamma-ray source of tightly focused.
Owing to the image spatial resolution of point source projection photograph depends greatly on the size in source, this utility model
The generation of gamma ray comes from the bremsstrahlung of high energy electron.In view of laser in the instability of Plasma Transport process
Property, it is necessary to obtain undersized near critical density plasma.Comparing with in first technology [1], plasma dimension subtracts significantly
Little, it is suppressed that Laser Transmission unstability, be conducive to controlling the size of electron beam thus control the size of gamma-ray source.This
Outward, the constraint effect of quasi-static electomagnetic field further reduces the angle of divergence of high energy electron and the space chi of gamma-ray source
Very little.
Plasma density too high or too low, all can have influence on electron beam mean temperature, and then affect gamma ray
Energy.According to light laser and near critical density plasma interaction theory, plasma density ne=0.1-1 ×
1021/cm3Time, during laser transmits in the plasma, it is contemplated that the group velocity of laser and the speed phase of electron motion
Closely, therefore, electronics can be accelerated to the highest energy, produced high energy electricity by the way of Betatron resonates by laser
Sub-electricity is up to tens of nC.It is contemplated that electronics is certain to the conversion ratio of photon, compared with in first technology [1], gamma light
The quantity of son is significantly increased, i.e. source brightness is higher.
Compare with in first technology [1-3], this utility model due to need not bulky complex ultrasonic gas nozzle and
Air distributing device, it is not required that individually ns laser beam, significantly reduces construction cost and the operating cost of gamma-ray source.
Further, for this utility model is better achieved, a diameter of 0.5mm of described metal tantalum post, thickness is
0.5mm。
Further, for this utility model is better achieved, described target frame thickness is 100-200 μm.
Further, for this utility model is better achieved, described vacuum target chamber system includes lead screen layer and setting
Laser beam focusing arrangement inside described lead screen layer, described composite construction target is positioned at inside described lead screen layer.
Further, for this utility model is better achieved, below described composite construction target, it is provided with electron beam inclined
Turn magnet ring, below described deflection of a beam of electrons magnet ring, be provided with sample stage.
Further, for this utility model is better achieved, outside described lead screen layer, it is provided with ray source point throws
Shadow record by imaging equipment, described composite construction target, sample stage, radiographic source spot projection record by imaging equipment center line is contour.
Further, for this utility model is better achieved, it is provided with aiming system of looking in the distance in described lead screen layer side
System.
The production method of superlaser gamma-ray source based on micro-dimension near critical density plasma, including following step
Rapid:
S1: composite construction target is arranged on vacuum target chamber internal system, make thickness be 10 μm, average density be 5mg/cm3
The hydrocarbon layer of low-density by target frame cover before metal tantalum post formed composite construction target, make to deposit between metal tantalum post and target frame
At closed cavity；
S2: laser beam focusing arrangement is set for being focused laser beam at vacuum target chamber system memory；
S3: using power density is 1014W/cm2Laser pre-pulse, utilize laser beam focusing arrangement to be arrived by laser focusing
On the hydrocarbon layer of low-density, make laser pre-pulse be absorbed in a large number at critical surface, burnt by impact absorption and parameter absorption pattern
Erosion ionization material, is more than the place of critical surface for density, and the ablation wave that prepulsing is formed will by the way of Electron Heat Conduction
Hydrocarbon leafingization forms plasma；
S4: using power density is 1019-1020W/cm2Laser main pulse, utilize laser beam focusing arrangement by laser master
Pulse concentration, on the hydrocarbon layer of low-density, forms plasma channel in plasma internal transmission, finally produces gamma ray
Source.
In described step S3, the laser pre-pulse persistent period is 1ns.
Described step S3 intermediate ion body density is ne= 0.1-1×1021/cm3。
This utility model compared with prior art, has the advantages that
This utility model other laser gamma-ray sources compared to existing technology are compared, have that Source size is little, source brightness high,
Low cost and other advantages.
Accompanying drawing explanation
Accompanying drawing 1 is laser tightly focused gamma ray source apparatus schematic layout pattern；
Accompanying drawing 2 is composite construction target front view；
Accompanying drawing 3 is composite construction target top view；
Accompanying drawing 4 is that accompanying drawing 3A-A is to sectional view.
Reference: 101. vacuum target chamber systems, 102. lead screen layers, 103. laser beam focusing arrangements, 104. composite junctions
Structure target, 105. look in the distance sighting system, 106. deflection of a beam of electrons magnet rings, 107. sample stages, 108. radiographic source spot projection record by imaging
Equipment, the 201. hydrocarbon layers of low-density, 202. target frames, 203. metal tantalum posts.
Detailed description of the invention
Below in conjunction with specific embodiment, this utility model is described in further detail, but embodiment party of the present utility model
Formula is not limited to this.
Embodiment:
As Figure 1-4, this utility model radiographic source includes by vacuum target chamber system 101, lead screen layer 102, laser beam
Focusing arrangement 103, target control system and composite construction target 104, sighting system 105 of looking in the distance, deflection of a beam of electrons magnet ring 106, sample
Sample platform 107.Laser beam and focusing arrangement 103 thereof, composite construction target 104, sample stage 107, radiographic source spot projection record by imaging sets
Standby 107 centrages are contour.Composite construction target 104, record by imaging equipment 108 is coaxial.Composite construction target is hydrocarbon by ultra-thin low-density
The parts such as layer 201, target frame 202, metal tantalum post 203 are constituted.The hydrocarbon layer thickness of ultra-thin low-density is 10 μm, and average density is 5mg/
cm3.The whole hydrocarbon layer of ultra-thin low-density was covered before metal tantalum post by target frame, and the material of target frame is nonmetal.Metal tantalum
A diameter of 0.5mm of post, thickness is also all 0.5mm.
The power density 10 of laser main pulse19-1020W/cm2, contrast between laser pre-pulse and laser main pulse
105, corresponding laser pre-pulse power density is 1014W/cm2.Laser focuses on composite junction by the off axis paraboloidal mirror in target chamber
On the hydrocarbon layer of structure target.
Laser pre-pulse will be absorbed at critical surface in a large number, by mode ablation ionizations such as impact absorption and parameter absorptions
Material.
For density more than the place of critical surface, the ablation wave that prepulsing is formed by the way of Electron Heat Conduction by hydrocarbon
Leafingization forms plasma.
Owing to using the hydrocarbon layer of ultra-thin low-density, hydrocarbon layer average density is relatively low, only 5mg/cm3, in plasma
Temperature declines the slowest, it is ensured that before main pulse arrives, the persistent period is that the laser pre-pulse of nanosecond order is by ultra-thin carbon
The abundant ionization of hydrogen layer.
Whole hydrocarbon layer material is all heated to the temperature of KeV under the effect of ablation wave, forms plasma.Plasma
Body at such high temperatures, by the vacuum expansion before and after hydrocarbon layer.For hydrocarbon froth bed, prepulsing continues 1ns, plasma
Respectively expanding about 100 μm before and after can, (final plasma density be about close to critical density for the plasma density after expansion
For ne= 0.1-1×1021/cm3).Plasma entrance target frame (thickness takes 200 μm) after expansion and metal tantalum post are formed
Confined space.
After laser main pulse arrives, in plasma internal transmission, form plasma channel.
In plasma channel, owing to electronics is pushed open by pondermotive force, form quasi-static radial direction separation of charge field, electric field
Direction is radially.Backflow electronics along conduit wall will produce quasi-stationary poloidal magnetic field.Relativistic Electron is by quasistatic electromagnetism
Field containment is in also front motion vertically together with laser in plasma channel, and electronics is laterally returning with frequencies omega p/2 simultaneously
Rotation vibration.Resonantly positive energy exchange between laser and electronics, electronics is surfing in laser field, and the electronics with appropriate phase will be constantly
Ground extracts mean oscillatory energy from laser field.After experiencing repeatedly Betatron resonance resonance, electronics will obtain the highest energy
Gain, the mean temperature of electron beam is up to 10MeV, and the quantity of electric charge is 15nC.
Additionally, the size in quasi-steady state magnetic field is tens of megagausses present in plasma, it is sufficient to the electron beam that will produce
It is collimated to the angle of divergence in several years.The spot size of final produced gamma-ray source is less than 100 μm.
Claims (7)
1. superlaser gamma-ray source based on micro-dimension near critical density plasma, it is characterised in that: include vacuum target
Chamber system (101) and be arranged on the composite construction target (104) of described vacuum target chamber system (101) inner side, described composite junction
Structure target (104) includes target frame (202) and is arranged on the metal tantalum post (203) of target frame (202) side, at described target frame (202)
It is coated with the hydrocarbon layer of low-density (201), in described metal tantalum post (203) and institute away from described metal tantalum post (203) one end
It is provided with closed cavity between the target frame (202) stated.
Superlaser gamma-ray source based on micro-dimension near critical density plasma the most according to claim 1, its
Being characterised by: a diameter of 0.5mm of described metal tantalum post (203), thickness is 0.5mm.
Superlaser gamma-ray source based on micro-dimension near critical density plasma the most according to claim 1 and 2,
It is characterized in that: described target frame (202) thickness is 100-200 μm.
Superlaser gamma-ray source based on micro-dimension near critical density plasma the most according to claim 1 and 2,
It is characterized in that: described vacuum target chamber system (101) includes lead screen layer (102) and is arranged on described lead screen layer
(102) laser beam focusing arrangement (103) of inner side, described composite construction target (104) is positioned at described lead screen layer (102)
Side.
Superlaser gamma-ray source based on micro-dimension near critical density plasma the most according to claim 4, its
It is characterised by: be provided with deflection of a beam of electrons magnet ring (106), at described electron beam in described composite construction target (104) lower section
Deflection magnet ring (106) lower section is provided with sample stage (107).
Superlaser gamma-ray source based on micro-dimension near critical density plasma the most according to claim 5, its
It is characterised by: described lead screen layer (102) outside is provided with radiographic source spot projection record by imaging equipment (108), described
Composite construction target (104), sample stage (107), radiographic source spot projection record by imaging equipment (108) centrage is contour.
Superlaser gamma-ray source based on micro-dimension near critical density plasma the most according to claim 4, its
It is characterised by: described lead screen layer (102) side is provided with sighting system of looking in the distance (105).
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| Application Number | Priority Date | Filing Date | Title |
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| CN201620703248.9U CN205751548U (en) | 2016-07-05 | 2016-07-05 | Superlaser gamma-ray source based on micro-dimension near critical density plasma |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112290372A (en) * | 2020-11-18 | 2021-01-29 | 中国人民解放军国防科技大学 | System and method for generating monoenergetic attosecond positive electric string |
| CN114302552A (en) * | 2021-12-09 | 2022-04-08 | 清华大学 | Composite conversion target |
-
2016
- 2016-07-05 CN CN201620703248.9U patent/CN205751548U/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112290372A (en) * | 2020-11-18 | 2021-01-29 | 中国人民解放军国防科技大学 | System and method for generating monoenergetic attosecond positive electric string |
| CN114302552A (en) * | 2021-12-09 | 2022-04-08 | 清华大学 | Composite conversion target |
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Granted publication date: 20161130 Termination date: 20210705 |
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