In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulation...In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy densities.The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur.We give the electron and ion energy densities for broad target parameter ranges.The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold greater.At optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) level.In the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results well.Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.展开更多
Laser-accelerated ion beams(LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here w...Laser-accelerated ion beams(LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample.展开更多
The production of broadband,terawatt terahertz(THz) pulses has been demonstrated by irradiating relativistic lasers on solid targets.However,the generation of extremely powerful,narrow-band and frequency-tunable THz p...The production of broadband,terawatt terahertz(THz) pulses has been demonstrated by irradiating relativistic lasers on solid targets.However,the generation of extremely powerful,narrow-band and frequency-tunable THz pulses remains a challenge.Here,we present a novel approach for such THz pulses,in which a plasma wiggler is elaborated by a table-top laser and a near-critical density plasma.In such a wiggler,the laser-accelerated electrons emit THz radiations with a period closely related to the plasma thickness.The theoretical model and numerical simulations predict that a THz pulse with a laser-THz energy conversion of over 2.0%,an ultra-strong field exceeding 80 GV/m,a divergence angle of approximately 200 and a center frequency tunable from 4.4 to 1.5 THz can be generated from a laser of 430 mJ.Furthermore,we demonstrate that this method can work across a wide range of laser and plasma parameters,offering potential for future applications with extremely powerful THz pulses.展开更多
基金This work was supported by the NSFC innovation group project(Grant No.11921006)the National Grand Instrument Project(Grant No.2019YFF01014402)+1 种基金the United States Department of Energy(Grant No.DE-FG03-93ER40773)the NNSA(Grant No.DENA0003841)(CENTAUR).The PIC simulations were carried out using the High-Performance Computing Platform of Peking University。
文摘In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy densities.The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur.We give the electron and ion energy densities for broad target parameter ranges.The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold greater.At optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) level.In the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results well.Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11875077,11975037,and 11921006)the National Grand Instrument Project of China(Grant Nos.2019YFF01014400 and 2019YFF01014404).
文摘Laser-accelerated ion beams(LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample.
基金supported by the National Natural Science Foundation of China(Grant Nos.11921006 and 12175058)Beijing Distinguished Young Scientist Program and National Grand Instrument Project(Grant No.SQ2019YFF01014400)in part funded by UK EPSRC(Grant Nos.EP/G054950/1,EP/G056803/1,EP/G055165/1 and EP/M022463/1).
文摘The production of broadband,terawatt terahertz(THz) pulses has been demonstrated by irradiating relativistic lasers on solid targets.However,the generation of extremely powerful,narrow-band and frequency-tunable THz pulses remains a challenge.Here,we present a novel approach for such THz pulses,in which a plasma wiggler is elaborated by a table-top laser and a near-critical density plasma.In such a wiggler,the laser-accelerated electrons emit THz radiations with a period closely related to the plasma thickness.The theoretical model and numerical simulations predict that a THz pulse with a laser-THz energy conversion of over 2.0%,an ultra-strong field exceeding 80 GV/m,a divergence angle of approximately 200 and a center frequency tunable from 4.4 to 1.5 THz can be generated from a laser of 430 mJ.Furthermore,we demonstrate that this method can work across a wide range of laser and plasma parameters,offering potential for future applications with extremely powerful THz pulses.
