The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with th...The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%.Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.展开更多
By using three-dimensional particle-in-cell simulations, externally injected electron beam acceleration and radiation in donut-like wake fields driven by a Laguerre-Gaussian pulse are investigated. Studies show that i...By using three-dimensional particle-in-cell simulations, externally injected electron beam acceleration and radiation in donut-like wake fields driven by a Laguerre-Gaussian pulse are investigated. Studies show that in the acceleration process the total charge and azimuthal momenta of electrons can be stably maintained at a distance of a few hundreds of micrometers. Electrons experience low-frequency spiral rotation and high-frequency betatron oscillation, which leads to a synchrotron-like radiation. The radiation spectrum is mainly determined by the betatron motion of electrons. The far field distribution of radiation intensity shows axial symmetry due to the uniform transverse injection and spiral rotation of electrons. Our studies suggest a new way to simultaneously generate hollow electron beam and radiation source from a compact laser plasma accelerator.展开更多
X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast scien...X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.展开更多
The rapid degradation of organic pollutants,process monitoring and online controlling to obtain advanced products and decreased by-products are great and challenging tasks in environmental treatments.Herein,an acceler...The rapid degradation of organic pollutants,process monitoring and online controlling to obtain advanced products and decreased by-products are great and challenging tasks in environmental treatments.Herein,an accelerated plasma degradation in milliseconds was achieved by combining electrospray-based acceleration and plasma-based degradation.Taking the degradation of chloroaniline as an example,97%of the degradation can be achieved in milliseconds.The velocity distribution of droplets was determined to be 40-50 m/s after being degraded for 0.30 ms,which exhibited different degradation behaviors in different milliseconds.Simultaneously,by virtue of the real-time and on-line detection ability of ambient mass spectrometry,intermediates,by-products and advanced products were monitored.Therefore,degradation mechanisms for different degradation times were proposed,which would provide theoretical guidance on obtaining efficient and green degradation.The fabrication,examining and understanding of accelerated plasma degradation not only enlarged application of accelerated reactions,but also promoted green and efficient degradation for environmental treatments.展开更多
A compact laser plasma accelerator that is a novel accelerator based on the interaction of ultra-intense laser and plasmas is being built now at Peking University. According to the results of experiments and numerical...A compact laser plasma accelerator that is a novel accelerator based on the interaction of ultra-intense laser and plasmas is being built now at Peking University. According to the results of experiments and numerical simulations, a beam line combining the advantages of quadrupole and analyzing magnets is designed to deliver proton beams with energy ranging from 1 to 44MeV, energy spread within ±5% and 10^6-8 protons per pulse. It turns out that the existence of space charge force of protons can be ignored for the increase of transverse and longitudinal envelopes even in the case of 10^9 protons in one pulse. To cope with the challenge to obtain a uniform distribution of protons at the final experiment target in laser acceleration, we manipulate the envelope beam waist in the Y direction to a proper position and obtain a relatively good distribution uniformity of protons with an energy spread of 0-±5%0.展开更多
Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generat...Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and cavity electrostatic potential.展开更多
Due to the growing interest in studying the compression and disruption of the plasma filament in magnetic fusion devices and Z-pinches, this work may be important for new developments in the field of controlled thermo...Due to the growing interest in studying the compression and disruption of the plasma filament in magnetic fusion devices and Z-pinches, this work may be important for new developments in the field of controlled thermonuclear fusion. Recently, on a coaxial plasma accelerator, we managed to obtain the relatively long-lived(~300 μs) plasma filaments with its self-magnetic field. This was achieved after modification of the experimental setup by using high-capacitive and lowinductive energy storage capacitor banks, as well as electrical cables with low reactive impedance. Furthermore, we were able to avoid the reverse reflection of the plasma flux from the end of the plasma accelerator by installing a special plasma-absorbing target. Thus, these constructive changes of the experimental setup allowed us to investigate the physical properties of the plasma filament by using the comprehensive diagnostics including Rogowski coil,magnetic probes, and Faraday cup. As a result, such important plasma parameters as density of ions and temperature of electrons in plasma flux, time dependent plasma filament’s azimuthal magnetic field were measured in discharge gap and at a distance of 23.5 cm from the tip of the cathode. In addition, the current oscillograms and Ⅰ–Ⅴ characteristics of the plasma accelerator were obtained. In the experiments, we also observed the charge separation during the acceleration of plasma flow via oscillograms of electron and ion beam currents.展开更多
In addition to the matured ＂Laser Inertial Fusion Energy （LIFE）＂ with spherical compression of deuterium-tritium （DI） for a pure fusion engine or for fusion-fission-hybrid operation, a very new scheme may have n...In addition to the matured ＂Laser Inertial Fusion Energy （LIFE）＂ with spherical compression of deuterium-tritium （DI） for a pure fusion engine or for fusion-fission-hybrid operation, a very new scheme may have now been opened by igniting the neutron-free reaction of proton-boron-11 （p-^11B） using side-on block ignition. Laser pulses of several petawatt power and ps duration led to thc discovery of an anomaly of interaction, if the prepulses are cut off by a factor 108 （contrast ratio） to avoid relativistic self focusing. In this case the Bobin-Chu conditions of side-on ignition of solid fusion fuel can be applied after several improvements leading to energy gains of 10,000 similar to the Nuckolls-Wood ignition with extremely intense 5 MeV electron beams. In contrast to the impossible laser-ignition of p-^11B by the usual spherical compression, the side-on ignition is less than ten times only more difficult of DT ignition. This p-^11B fusion produces less radioactivity per gained energy than burning coal. After encouraging success with computations based on the different nuclear cross sections, next steps are focusing on stability and transport problems.展开更多
This paper presents separation results of a mixture of nitrogen, argon and krypton ions in the process of plasma-optical mass separation on the POMS-E-3 separator model. We determined the behavior of the separation wi...This paper presents separation results of a mixture of nitrogen, argon and krypton ions in the process of plasma-optical mass separation on the POMS-E-3 separator model. We determined the behavior of the separation with a change in the value of magnetic field induction in the azimuthator and in the degree of compensation of the spatial charge in ion flows. An analysis is performed for experimental data by correlation with the results of a theoretical study and numerical experiments. The objectives of future experiments are outlined.展开更多
X-ray sources with tunable energy spectra have a wide range of applications in different scenarios due to their different penetration depths.However,existing x-ray sources face difficulties in terms of energy regulati...X-ray sources with tunable energy spectra have a wide range of applications in different scenarios due to their different penetration depths.However,existing x-ray sources face difficulties in terms of energy regulation.In this paper,we present a scheme for tuning the energy spectrum of a betatron x-ray generated from a relativistic electron bunch oscillating in a plasma wakefield.The center energy of the x-ray source can be tuned from several keV to several hundred keV by changing the plasma density,thereby extending the control range by an order of magnitude.At different central energies,the brightness of the betatron radiation is in the range of 3.7×10^(22)to 5.5×10^(22)photons/(0.1%BW·s·mm^(2)·mrad^(2))and the photon divergence angle is about 2 mrad.This high-brightness,energy-controlled betatron source could pave the way to a wide range of applications requiring photons of specific energy,such as phase-contrast imaging in medicine,non-destructive testing and material analysis in industry,and imaging in nuclear physics.展开更多
A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse pow...A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse power supply system including the charging circuit, start switch and current transfer system along with some of the key techniques for this kind of accelerator. Using this accelerator configuration, ceramic beads of 100 μm in diameter were accelerated to a speed as high as 18 km/sec. The facility can be used in a laboratory setting to study impact phenomena on solar array materials, potential structural materials for use in space.展开更多
Recent experimental data for anomalous magnetic moments strongly indicates the existence of new physics beyond the Standard Model.Energetic μ^(+) bunches are relevant to μ^(+) rare decay,spin rotation,resonance and ...Recent experimental data for anomalous magnetic moments strongly indicates the existence of new physics beyond the Standard Model.Energetic μ^(+) bunches are relevant to μ^(+) rare decay,spin rotation,resonance and relaxation(μSR)technology,future muon colliders,and neutrino factories.In this paper,we propose prompt μ^(+) acceleration in a nonlinear toroidal wakefield driven by a shaped steep-rising-front Laguerre–Gaussian(LG)laser pulse.An analytical model is described,which shows that a μ^(+) beam can be focused by an electron cylinder at the centerline of a toroidal bubble and accelerated by the front part of the longitudinal wakefield.A shaped LG laser with a short rise time can push plasma electrons,generating a higher-density electron sheath at the front of the bubble,which can enhance the acceleration field.The acceleration field driven by the shaped steep-rising-front LG laser pulse is about four times greater than that driven by a normal LG laser pulse.Our simulation results show that a 300 MeV μ^(+) bunch can be accelerated to 2 GeV and its transverse size is focused from an initial value of w_(0)=5μm to w=2μm in the toroidal bubble driven by the shaped steep-rising-front LG laser pulse with a normalized amplitude of a=22.展开更多
Theoretical analysis of the electromagnetically accelerated plasma spraying(EMAPS)by self-developed is carried out.Governing equation of the plasma under dynamic loading conditions is derived.The plasma velocity as a ...Theoretical analysis of the electromagnetically accelerated plasma spraying(EMAPS)by self-developed is carried out.Governing equation of the plasma under dynamic loading conditions is derived.The plasma velocity as a function of time and the length of electrode are also obtained.NiCrAl coating is prepared on medium carbon steel substrate by EMAPS device.Microstructure and hardness of the coating are analyzed with scanning electron microscope(SEM)and hardness tester respectively.展开更多
The thorough exploration of the transverse quality represented by divergence angle has been lacking yet in the energy spread measurement of the relativistic electron beam for laser wakefield acceleration(LWFA). In thi...The thorough exploration of the transverse quality represented by divergence angle has been lacking yet in the energy spread measurement of the relativistic electron beam for laser wakefield acceleration(LWFA). In this work, we fill this gap by numerical simulations based on the experimental data, which indicate that in a C-shape magnet, magnetic field possesses the beam focusing effect, considering that the divergence angle will result in an increase in the full width at half maxima(FWHM) of the electron density distribution in a uniformly isotropic manner, while the length-to-width ratio decreases. This indicates that the energy spread obtained from the electron deflection distance is smaller than the actual value, regardless of the divergence angle. A promising and efficient way to accurately correct the value is presented by considering the divergence angle(for instance, for an electron beam with a length-to-width ratio of 1.12, the energy spread correct from 1.2% to 1.5%), providing a reference for developing the high-quality electron beam source.展开更多
Heating and acceleration of electrons in solar impulsive hard X-ray （HXR） flares are studied according to the two-stage acceleration model developed by Zhang for solar ^3Herich events. It is shown that electrostatic...Heating and acceleration of electrons in solar impulsive hard X-ray （HXR） flares are studied according to the two-stage acceleration model developed by Zhang for solar ^3Herich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons （up to 40 MK） through landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flareproduced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager （RHESSI） HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements.展开更多
The bulk kinetic energy of jets can be dissipated via generating tur- bulen plasma waves. We examine stochastic particle acceleration in blazar jets to explain the emissions of all blazars. We show that acceleration o...The bulk kinetic energy of jets can be dissipated via generating tur- bulen plasma waves. We examine stochastic particle acceleration in blazar jets to explain the emissions of all blazars. We show that acceleration of electrons by plasma turbulence wavs with a spectrum W(k) ~ k^(-4/3) produces a nonthermal population of relativistic electrons whose peak frequency of synchrotron emission can fit the observational trends in the spectral energy distribution of all blazars. The plasma nonlinear processes responsible for the formation of turbulent spectrum are investigated. Increases in the ioteraction time of turbulent waves can produce a fiatter spectrum leading to efficient particle acceleration.展开更多
The effect of drive laser wavelength on the growth of ablative Rayleigh–Taylor instability(ARTI)in inertial confinemen fusion(ICF)is studied with two-dimensional numerical simulations.The results show that in the pla...The effect of drive laser wavelength on the growth of ablative Rayleigh–Taylor instability(ARTI)in inertial confinemen fusion(ICF)is studied with two-dimensional numerical simulations.The results show that in the plasma acceleration phase,shorter wavelengths lead to more efficien coupling between the laser and the kinetic energy of the implosion fluid Under the condition that the laser energy coupled to the implosion flui is constant,the ARTI growth rate decreases as the laser wavelength moves toward the extreme ultraviolet band,reaching its minimum value near λ=65 nm,and when the laser wavelength continuously moves toward the X-ray band,the ARTI growth rate increases rapidly.It is found that the results deviate from the theoretical ARTI growth rate.As the laser intensity benchmark increases,the position of the minimum ARTI growth rate shifts toward shorter wavelengths.As the initial sinusoidal perturbation wavenumber decreases,the position of the minimum ARTI growth rate shifts toward longer wavelengths.We believe that the conclusions drawn from the present simulations and analysis will help provide a better understanding of the ICF process and improve the theory of ARTI growth.展开更多
In this study,we theoretically investigate the feasibility of using laser-wakefield accelerated(LWFA)electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obta...In this study,we theoretically investigate the feasibility of using laser-wakefield accelerated(LWFA)electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser-Plasma Accelerator(CLAPA)laboratory.The experiments at the CLAPA show that a stable electron beam with an energy of 78-135 MeV and a charge of 300-600 pC can be obtained.The bremsstrahlung spectra were simulated using Geant4,which suggests that a bremsstrahlung source with a peak intensity of 10^(19) photons/s can be generated.Theoretical calculations of isomer production cross sections from the photonuclear reactions on six target nuclei,^(197)Au,^(180)Hf,^(159)Tb,^(115)In,^(103)Rh,and ^(90)Zr,were performed and compared with the available experimental data in EXFOR,which suggest that further experiments are required for a series of photonuclear reaction channels.Flux-averaged cross sections and isomer ratios(IR)resulting from such bremsstrahlung sources are theoretically deduced.The results suggest that IR measurements can be used to constrain nuclear components,such asγstrength function and optical model potential.In addition,the detection of the decay characteristics was evaluated with Geant4 simulations.The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.展开更多
We present three possible design options of laser plasma acceleration （LPA） for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-k J, 500-fs PETawatt Aquitane Laser （PETAL） at Fre...We present three possible design options of laser plasma acceleration （LPA） for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-k J, 500-fs PETawatt Aquitane Laser （PETAL） at French Alternative Energies and Atomic Energy Commission （CEA）. Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 = 1.4（1.6）, acceleration to 100 （130） GeV requires a 30-m-long plasma waveguide operated at the plasma density ne ≈ 7 ×10^15 c^m-3 with a channel depth An/ne = 20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0 〉/ 2 can reach 100 GeV approximately in a 36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a llr-mm-mrad- level transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0 = 4, radiative energy loss becomes 10% at the maximum energy of 90 GeV.展开更多
Ten million times more compact energy than from burning carbon can be obtained from nuclear fusion reactions corresponding to equilibrium temperature reactions in the range above 100 million degrees.Following the ener...Ten million times more compact energy than from burning carbon can be obtained from nuclear fusion reactions corresponding to equilibrium temperature reactions in the range above 100 million degrees.Following the energy gain in stars,one has to gain nuclear energy from slamming very light nuclei where however the extremely high temperatures above 100 million degrees are needed for the sufficient pressures at thermal equilibrium ignition.A radically new option works with non-thermal pressures of picosecond laser pulses at ultrahigh optical powers by nonlinear forces of ponderomotion.The nuclear fusion of hydrogen with the isotope 11 of boron produces primarily harmless helium and has no problems with dangerous radioactive waste and excludes any catastrophic melt-down as fission reactors,it has the potential to be of low costs and can supply the Earth for more than 10,000 years with electricity.展开更多
基金Supported by the Fund of Science and Technology on Vacuum Technology and Physics Laboratory of Lanzhou Institute of Physics under Grant No YSC0715the National Natural Science Foundation of China under Grant No 62601210the Civil Aerospace Technology Research Project under Grant No D010509
文摘The effects of three different typical resistivity models（Spitzer, Z＆L and M＆G） on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%.Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374209,11374210,and 11774227)the Major State Basic Research Development Program of China(Grant No.2015CB859700)
文摘By using three-dimensional particle-in-cell simulations, externally injected electron beam acceleration and radiation in donut-like wake fields driven by a Laguerre-Gaussian pulse are investigated. Studies show that in the acceleration process the total charge and azimuthal momenta of electrons can be stably maintained at a distance of a few hundreds of micrometers. Electrons experience low-frequency spiral rotation and high-frequency betatron oscillation, which leads to a synchrotron-like radiation. The radiation spectrum is mainly determined by the betatron motion of electrons. The far field distribution of radiation intensity shows axial symmetry due to the uniform transverse injection and spiral rotation of electrons. Our studies suggest a new way to simultaneously generate hollow electron beam and radiation source from a compact laser plasma accelerator.
基金supported by the National Grand Instrument Project No. SQ2019YFF01014400the Natural Science Foundation of China (Grant Nos. 12375147, 12435011, 12075030)+2 种基金the Beijing Outstanding Young Scientist Project, Project for Young Scientists in Basic Research of Chinese Academy of Sciences (YSBR-115)the Beijing Normal University Scientific Research Initiation Fund for Introducing Talents No. 310432104the Fundamental Research Funds for the Central Universities, Peking University
文摘X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.
基金the financial support provided by the National Key Research and Development Program of China(No.2019YFC1805600)the National Natural Science Foundation of China(Nos.21874012,21974010).
文摘The rapid degradation of organic pollutants,process monitoring and online controlling to obtain advanced products and decreased by-products are great and challenging tasks in environmental treatments.Herein,an accelerated plasma degradation in milliseconds was achieved by combining electrospray-based acceleration and plasma-based degradation.Taking the degradation of chloroaniline as an example,97%of the degradation can be achieved in milliseconds.The velocity distribution of droplets was determined to be 40-50 m/s after being degraded for 0.30 ms,which exhibited different degradation behaviors in different milliseconds.Simultaneously,by virtue of the real-time and on-line detection ability of ambient mass spectrometry,intermediates,by-products and advanced products were monitored.Therefore,degradation mechanisms for different degradation times were proposed,which would provide theoretical guidance on obtaining efficient and green degradation.The fabrication,examining and understanding of accelerated plasma degradation not only enlarged application of accelerated reactions,but also promoted green and efficient degradation for environmental treatments.
基金Supported by the National Natural Science Foundation of China under Grant No 11575011the National Grand Instrument Project under Grant No 2012YQ030142
文摘A compact laser plasma accelerator that is a novel accelerator based on the interaction of ultra-intense laser and plasmas is being built now at Peking University. According to the results of experiments and numerical simulations, a beam line combining the advantages of quadrupole and analyzing magnets is designed to deliver proton beams with energy ranging from 1 to 44MeV, energy spread within ±5% and 10^6-8 protons per pulse. It turns out that the existence of space charge force of protons can be ignored for the increase of transverse and longitudinal envelopes even in the case of 10^9 protons in one pulse. To cope with the challenge to obtain a uniform distribution of protons at the final experiment target in laser acceleration, we manipulate the envelope beam waist in the Y direction to a proper position and obtain a relatively good distribution uniformity of protons with an energy spread of 0-±5%0.
文摘Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and cavity electrostatic potential.
基金supported by the Ministry of Education and Science of the Republic of Kazakhstan(IRN AP08053373)。
文摘Due to the growing interest in studying the compression and disruption of the plasma filament in magnetic fusion devices and Z-pinches, this work may be important for new developments in the field of controlled thermonuclear fusion. Recently, on a coaxial plasma accelerator, we managed to obtain the relatively long-lived(~300 μs) plasma filaments with its self-magnetic field. This was achieved after modification of the experimental setup by using high-capacitive and lowinductive energy storage capacitor banks, as well as electrical cables with low reactive impedance. Furthermore, we were able to avoid the reverse reflection of the plasma flux from the end of the plasma accelerator by installing a special plasma-absorbing target. Thus, these constructive changes of the experimental setup allowed us to investigate the physical properties of the plasma filament by using the comprehensive diagnostics including Rogowski coil,magnetic probes, and Faraday cup. As a result, such important plasma parameters as density of ions and temperature of electrons in plasma flux, time dependent plasma filament’s azimuthal magnetic field were measured in discharge gap and at a distance of 23.5 cm from the tip of the cathode. In addition, the current oscillograms and Ⅰ–Ⅴ characteristics of the plasma accelerator were obtained. In the experiments, we also observed the charge separation during the acceleration of plasma flow via oscillograms of electron and ion beam currents.
文摘In addition to the matured ＂Laser Inertial Fusion Energy （LIFE）＂ with spherical compression of deuterium-tritium （DI） for a pure fusion engine or for fusion-fission-hybrid operation, a very new scheme may have now been opened by igniting the neutron-free reaction of proton-boron-11 （p-^11B） using side-on block ignition. Laser pulses of several petawatt power and ps duration led to thc discovery of an anomaly of interaction, if the prepulses are cut off by a factor 108 （contrast ratio） to avoid relativistic self focusing. In this case the Bobin-Chu conditions of side-on ignition of solid fusion fuel can be applied after several improvements leading to energy gains of 10,000 similar to the Nuckolls-Wood ignition with extremely intense 5 MeV electron beams. In contrast to the impossible laser-ignition of p-^11B by the usual spherical compression, the side-on ignition is less than ten times only more difficult of DT ignition. This p-^11B fusion produces less radioactivity per gained energy than burning coal. After encouraging success with computations based on the different nuclear cross sections, next steps are focusing on stability and transport problems.
基金support of the Ministry of Education and Science of the Russian Federation grant to perform scientific work number 82 within the base portion of the state task No. 2014/53 from 2014 in the field of scientific activity
文摘This paper presents separation results of a mixture of nitrogen, argon and krypton ions in the process of plasma-optical mass separation on the POMS-E-3 separator model. We determined the behavior of the separation with a change in the value of magnetic field induction in the azimuthator and in the degree of compensation of the spatial charge in ion flows. An analysis is performed for experimental data by correlation with the results of a theoretical study and numerical experiments. The objectives of future experiments are outlined.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11921006 and 12175058)the Beijing Distinguished Young Scientist Program and National Grand Instrument Project (Grant No.SQ2019YFF01014400)+1 种基金the Beijing Municipal Science&Technology Commission,Administrative Commission of Zhongguancun Science Park (Grant No.Z231100006023003)in part funded by United Kingdom EPSRC (Grant Nos.EP/G054950/1,EP/G056803/1,EP/G055165/1,and EP/M022463/1)。
文摘X-ray sources with tunable energy spectra have a wide range of applications in different scenarios due to their different penetration depths.However,existing x-ray sources face difficulties in terms of energy regulation.In this paper,we present a scheme for tuning the energy spectrum of a betatron x-ray generated from a relativistic electron bunch oscillating in a plasma wakefield.The center energy of the x-ray source can be tuned from several keV to several hundred keV by changing the plasma density,thereby extending the control range by an order of magnitude.At different central energies,the brightness of the betatron radiation is in the range of 3.7×10^(22)to 5.5×10^(22)photons/(0.1%BW·s·mm^(2)·mrad^(2))and the photon divergence angle is about 2 mrad.This high-brightness,energy-controlled betatron source could pave the way to a wide range of applications requiring photons of specific energy,such as phase-contrast imaging in medicine,non-destructive testing and material analysis in industry,and imaging in nuclear physics.
基金the Programme for Scientific Instrument Development of the Chinese Academy of Sciences(No.y2003001)
文摘A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse power supply system including the charging circuit, start switch and current transfer system along with some of the key techniques for this kind of accelerator. Using this accelerator configuration, ceramic beads of 100 μm in diameter were accelerated to a speed as high as 18 km/sec. The facility can be used in a laboratory setting to study impact phenomena on solar array materials, potential structural materials for use in space.
基金supported in part by the National Key R&D Program of China(No.2018YFA0404802)National Natural Science Foundation of China(No.11875319)+2 种基金the Hunan Provincial Science and Technology Program(No.2020RC4020)Innovation Project of IHEP(Nos.542017IHEPZZBS11820,542018IHEPZZBS12427)the CAS Center for Excellence in Particle Physics(CCEPP),the Meritocracy Research Funds of China West Normal University(No.17YC504)。
文摘Recent experimental data for anomalous magnetic moments strongly indicates the existence of new physics beyond the Standard Model.Energetic μ^(+) bunches are relevant to μ^(+) rare decay,spin rotation,resonance and relaxation(μSR)technology,future muon colliders,and neutrino factories.In this paper,we propose prompt μ^(+) acceleration in a nonlinear toroidal wakefield driven by a shaped steep-rising-front Laguerre–Gaussian(LG)laser pulse.An analytical model is described,which shows that a μ^(+) beam can be focused by an electron cylinder at the centerline of a toroidal bubble and accelerated by the front part of the longitudinal wakefield.A shaped LG laser with a short rise time can push plasma electrons,generating a higher-density electron sheath at the front of the bubble,which can enhance the acceleration field.The acceleration field driven by the shaped steep-rising-front LG laser pulse is about four times greater than that driven by a normal LG laser pulse.Our simulation results show that a 300 MeV μ^(+) bunch can be accelerated to 2 GeV and its transverse size is focused from an initial value of w_(0)=5μm to w=2μm in the toroidal bubble driven by the shaped steep-rising-front LG laser pulse with a normalized amplitude of a=22.
基金Item Sponsored by"Fundamental Research Funds for the Central Universities[No.JB2011016]"
文摘Theoretical analysis of the electromagnetically accelerated plasma spraying(EMAPS)by self-developed is carried out.Governing equation of the plasma under dynamic loading conditions is derived.The plasma velocity as a function of time and the length of electrode are also obtained.NiCrAl coating is prepared on medium carbon steel substrate by EMAPS device.Microstructure and hardness of the coating are analyzed with scanning electron microscope(SEM)and hardness tester respectively.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2021YFA1601700)the National Natural Science Foundation of China (Grant Nos. 12074251, 11991073, 12335016, 12305272, and 12105174)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA25000000 and XDA25030400)Yangyang Development Fund,China。
文摘The thorough exploration of the transverse quality represented by divergence angle has been lacking yet in the energy spread measurement of the relativistic electron beam for laser wakefield acceleration(LWFA). In this work, we fill this gap by numerical simulations based on the experimental data, which indicate that in a C-shape magnet, magnetic field possesses the beam focusing effect, considering that the divergence angle will result in an increase in the full width at half maxima(FWHM) of the electron density distribution in a uniformly isotropic manner, while the length-to-width ratio decreases. This indicates that the energy spread obtained from the electron deflection distance is smaller than the actual value, regardless of the divergence angle. A promising and efficient way to accurately correct the value is presented by considering the divergence angle(for instance, for an electron beam with a length-to-width ratio of 1.12, the energy spread correct from 1.2% to 1.5%), providing a reference for developing the high-quality electron beam source.
基金NASA Grant （NNG04GD59G A/C 2-302-14-3380-119） National Science Foundation （ATM 00-70385）.
文摘Heating and acceleration of electrons in solar impulsive hard X-ray （HXR） flares are studied according to the two-stage acceleration model developed by Zhang for solar ^3Herich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons （up to 40 MK） through landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flareproduced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager （RHESSI） HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements.
基金the National AstronomicalObservatories, Chinese Academy of Sciences (NAOCAS) and by NAOCAS grant 991-5102CA.
文摘The bulk kinetic energy of jets can be dissipated via generating tur- bulen plasma waves. We examine stochastic particle acceleration in blazar jets to explain the emissions of all blazars. We show that acceleration of electrons by plasma turbulence wavs with a spectrum W(k) ~ k^(-4/3) produces a nonthermal population of relativistic electrons whose peak frequency of synchrotron emission can fit the observational trends in the spectral energy distribution of all blazars. The plasma nonlinear processes responsible for the formation of turbulent spectrum are investigated. Increases in the ioteraction time of turbulent waves can produce a fiatter spectrum leading to efficient particle acceleration.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.12074399,12204500,and 12004403)the Key Projects of the Intergovernmental International Scientifi and Technological Innovation Cooperation(Grant No.2021YFE0116700)+1 种基金the Shanghai Natural Science Foundation(Grant No.20ZR1464400)the Shanghai Sailing Program(Grant No.22YF1455300)。
文摘The effect of drive laser wavelength on the growth of ablative Rayleigh–Taylor instability(ARTI)in inertial confinemen fusion(ICF)is studied with two-dimensional numerical simulations.The results show that in the plasma acceleration phase,shorter wavelengths lead to more efficien coupling between the laser and the kinetic energy of the implosion fluid Under the condition that the laser energy coupled to the implosion flui is constant,the ARTI growth rate decreases as the laser wavelength moves toward the extreme ultraviolet band,reaching its minimum value near λ=65 nm,and when the laser wavelength continuously moves toward the X-ray band,the ARTI growth rate increases rapidly.It is found that the results deviate from the theoretical ARTI growth rate.As the laser intensity benchmark increases,the position of the minimum ARTI growth rate shifts toward shorter wavelengths.As the initial sinusoidal perturbation wavenumber decreases,the position of the minimum ARTI growth rate shifts toward longer wavelengths.We believe that the conclusions drawn from the present simulations and analysis will help provide a better understanding of the ICF process and improve the theory of ARTI growth.
基金supported by the National Natural Science Foundation of China (Nos.11921006,U2230133)Beijing Outstanding Young Scientists Program+2 种基金National Grand Instrument Project (No.2019YFF01014400)National Key R&D Program of China (No.2022YFA1603303)Open Foundation of Key Laboratory of High Power Laser and Physics,Chinese Academy of Sciences (No.SGKF202104)。
文摘In this study,we theoretically investigate the feasibility of using laser-wakefield accelerated(LWFA)electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser-Plasma Accelerator(CLAPA)laboratory.The experiments at the CLAPA show that a stable electron beam with an energy of 78-135 MeV and a charge of 300-600 pC can be obtained.The bremsstrahlung spectra were simulated using Geant4,which suggests that a bremsstrahlung source with a peak intensity of 10^(19) photons/s can be generated.Theoretical calculations of isomer production cross sections from the photonuclear reactions on six target nuclei,^(197)Au,^(180)Hf,^(159)Tb,^(115)In,^(103)Rh,and ^(90)Zr,were performed and compared with the available experimental data in EXFOR,which suggest that further experiments are required for a series of photonuclear reaction channels.Flux-averaged cross sections and isomer ratios(IR)resulting from such bremsstrahlung sources are theoretically deduced.The results suggest that IR measurements can be used to constrain nuclear components,such asγstrength function and optical model potential.In addition,the detection of the decay characteristics was evaluated with Geant4 simulations.The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.
基金supported by the National Natural Science Foundation of China(Nos.10834008,10974214,60921004,and 51175324)the National"973"Program of China(Nos.2011CB808104,2011CB808100,and 2010CB923203)supported by Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(No.2010T2G02)
文摘We present three possible design options of laser plasma acceleration （LPA） for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-k J, 500-fs PETawatt Aquitane Laser （PETAL） at French Alternative Energies and Atomic Energy Commission （CEA）. Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 = 1.4（1.6）, acceleration to 100 （130） GeV requires a 30-m-long plasma waveguide operated at the plasma density ne ≈ 7 ×10^15 c^m-3 with a channel depth An/ne = 20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0 〉/ 2 can reach 100 GeV approximately in a 36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a llr-mm-mrad- level transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0 = 4, radiative energy loss becomes 10% at the maximum energy of 90 GeV.
文摘Ten million times more compact energy than from burning carbon can be obtained from nuclear fusion reactions corresponding to equilibrium temperature reactions in the range above 100 million degrees.Following the energy gain in stars,one has to gain nuclear energy from slamming very light nuclei where however the extremely high temperatures above 100 million degrees are needed for the sufficient pressures at thermal equilibrium ignition.A radically new option works with non-thermal pressures of picosecond laser pulses at ultrahigh optical powers by nonlinear forces of ponderomotion.The nuclear fusion of hydrogen with the isotope 11 of boron produces primarily harmless helium and has no problems with dangerous radioactive waste and excludes any catastrophic melt-down as fission reactors,it has the potential to be of low costs and can supply the Earth for more than 10,000 years with electricity.
