With two-dimensional quantum electrodynamics（QED） particle-in-cell simulations, a dense electron-positron（e^-e~＋） pair generation from laser-solid interactions is demonstrated. When the interaction of two linearl...With two-dimensional quantum electrodynamics（QED） particle-in-cell simulations, a dense electron-positron（e^-e~＋） pair generation from laser-solid interactions is demonstrated. When the interaction of two linearly polarized laser pulses with a thin target enters into the relativistic transparency regime, a stable standing wave（SW） field can be formed by the overlap of the two counter-propagating laser pulses directly. The present study aims to clarify the effects of the S W field on the dynamics of e^-e^＋ pair plasmas. Our results indicate that under the combined effect of the SW field and radiation reaction（RR） effect, the created e^-e^＋ pairs can be trapped into the electric field nodes when the field strength is strong.The trapping effect contributes to the generation of γAV≥400 and ultra-dense pair plasmas in the two-side irradiation scheme. Despite different laser intensities, these pair plasmas have a Maxwellian spectral distribution with a peak energy of 150 MeV. Besides, the periodical modulation of the average energy, spatial, phase-space, and angular patterns of the e^-e^＋ pair plasmas can be triggered. In the angular patterns, as long as the SW field exists, pair plasmas can be pinched along the laser polarization direction. These results may offer a better understanding of the laser-solid interactions in the experiments when 10-PW laser facilities come into operation in the future.展开更多
By using a high-intensity flying focus laser,the dephasingless[Phys.Rev.Lett.124134802(2020)]or phase-locked[Nat.Photon.14475(2020)]laser wakefield acceleration(LWFA)can be realized,which may overcome issues of laser ...By using a high-intensity flying focus laser,the dephasingless[Phys.Rev.Lett.124134802(2020)]or phase-locked[Nat.Photon.14475(2020)]laser wakefield acceleration(LWFA)can be realized,which may overcome issues of laser diffraction,pump depletion,and electron dephasing which are always suffered in usual LWFA.The scheme thus has the potentiality to accelerate electrons to Te V energy in a single acceleration stage.However,the controlled electron injection has not been self-consistently included in such schemes.Only external injection was suggested in previous theoretical studies,which requires other accelerators and is relatively difficulty to operate.Here,we numerically study the actively controlled density transition injection in phase-locked LWFA to get appropriate density profiles for amount of electron injection.The study shows that compared with LWFA driven by lasers with fixed focus,a larger plasma density gradient is necessary.Electrons experience both transverse and longitudinal loss during acceleration due to the superluminal group velocity of the driver and the variation of the wakefield structure.Furthermore,the periodic deformation and fracture of the flying focus laser in the high-density plasma plateau make the final injected charge also depend on the beginning position of the density downramp.Our studies show a possible way for amount of electron injection in LWFA driven by flying focus lasers.展开更多
We use quantum electrodynamics particle-in-cell simulation to study the generation of dense electron–positron plasma and strongγ-ray bursts in counter-propagating laser beam interactions with two different solid tar...We use quantum electrodynamics particle-in-cell simulation to study the generation of dense electron–positron plasma and strongγ-ray bursts in counter-propagating laser beam interactions with two different solid targets,i.e.planar(type I)and convex(type II).We find that type II limits fast electron flow most effectively.while the photon density is increased by about an order of magnitude and energy by approx.10%–20%compared with those in type I target.γ-photon source with an ultrahigh peak brilliance of 2?×?1025 photons/s/mm2/mrad2/0.1%BW is generated by nonlinear Compton scattering process.Furthermore,use of type II target increases the positron density and energy by 3 times and 32%respectively,compared with those in type I target.In addition,the conversion efficiencies of total laser energy toγ-rays and positrons of type II are improved by 13.2%and 9.86%compared with type I.Such improvements in conversion efficiency and positron density are envisaged to have practical applications in experimental field.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CBA01504)the National Natural Science Foundation of China(Grant Nos.11347028,11405083,and 11675075)+1 种基金the Natural Science Foundation of Hunan Province,China(Grant No.2018JJ2315)the Youth Talent Project of Hunan Province,China(Grant No.2018RS3096)
文摘With two-dimensional quantum electrodynamics（QED） particle-in-cell simulations, a dense electron-positron（e^-e~＋） pair generation from laser-solid interactions is demonstrated. When the interaction of two linearly polarized laser pulses with a thin target enters into the relativistic transparency regime, a stable standing wave（SW） field can be formed by the overlap of the two counter-propagating laser pulses directly. The present study aims to clarify the effects of the S W field on the dynamics of e^-e^＋ pair plasmas. Our results indicate that under the combined effect of the SW field and radiation reaction（RR） effect, the created e^-e^＋ pairs can be trapped into the electric field nodes when the field strength is strong.The trapping effect contributes to the generation of γAV≥400 and ultra-dense pair plasmas in the two-side irradiation scheme. Despite different laser intensities, these pair plasmas have a Maxwellian spectral distribution with a peak energy of 150 MeV. Besides, the periodical modulation of the average energy, spatial, phase-space, and angular patterns of the e^-e^＋ pair plasmas can be triggered. In the angular patterns, as long as the SW field exists, pair plasmas can be pinched along the laser polarization direction. These results may offer a better understanding of the laser-solid interactions in the experiments when 10-PW laser facilities come into operation in the future.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11991074,12225505 and12135009)。
文摘By using a high-intensity flying focus laser,the dephasingless[Phys.Rev.Lett.124134802(2020)]or phase-locked[Nat.Photon.14475(2020)]laser wakefield acceleration(LWFA)can be realized,which may overcome issues of laser diffraction,pump depletion,and electron dephasing which are always suffered in usual LWFA.The scheme thus has the potentiality to accelerate electrons to Te V energy in a single acceleration stage.However,the controlled electron injection has not been self-consistently included in such schemes.Only external injection was suggested in previous theoretical studies,which requires other accelerators and is relatively difficulty to operate.Here,we numerically study the actively controlled density transition injection in phase-locked LWFA to get appropriate density profiles for amount of electron injection.The study shows that compared with LWFA driven by lasers with fixed focus,a larger plasma density gradient is necessary.Electrons experience both transverse and longitudinal loss during acceleration due to the superluminal group velocity of the driver and the variation of the wakefield structure.Furthermore,the periodic deformation and fracture of the flying focus laser in the high-density plasma plateau make the final injected charge also depend on the beginning position of the density downramp.Our studies show a possible way for amount of electron injection in LWFA driven by flying focus lasers.
基金supported by National Natural Science Foundation of China(NSFC)under Grant No.11875007
文摘We use quantum electrodynamics particle-in-cell simulation to study the generation of dense electron–positron plasma and strongγ-ray bursts in counter-propagating laser beam interactions with two different solid targets,i.e.planar(type I)and convex(type II).We find that type II limits fast electron flow most effectively.while the photon density is increased by about an order of magnitude and energy by approx.10%–20%compared with those in type I target.γ-photon source with an ultrahigh peak brilliance of 2?×?1025 photons/s/mm2/mrad2/0.1%BW is generated by nonlinear Compton scattering process.Furthermore,use of type II target increases the positron density and energy by 3 times and 32%respectively,compared with those in type I target.In addition,the conversion efficiencies of total laser energy toγ-rays and positrons of type II are improved by 13.2%and 9.86%compared with type I.Such improvements in conversion efficiency and positron density are envisaged to have practical applications in experimental field.
