A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating,accelerating and guiding protons,using a single-cone target with a beam collimator through a target normal sheath acc...A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating,accelerating and guiding protons,using a single-cone target with a beam collimator through a target normal sheath acceleration mechanism.In addition,the problems involved are studied by using two-dimensional particle-in-cell simulations.The results show that the proton beam can be collimated,accelerated and guided effectively through this type of target.Theoretically,a formula is derived for the combined electric field of accelerating protons.Compared with a proton beam without a beam collimator,the proton beam density and cut-off energy of protons in the type II are increased by 3.3 times and 10%respectively.Detailed analysis shows that the enhancement is mainly due to the compact and strong sheath electrostatic field,and that the beam collimator plays a role in focusing energy.In addition,the simulation results show that the divergence angle of the proton beam in type II is less than 1.67 times that of type I.The more prominent point is that the proton number of type II is 2.2 times higher than that of type I.This kind of target has important applications in many fields,such as fast ion ignition in inertial fusion,high energy physics and proton therapy.展开更多
A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is ...A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is found that the circular target can enhance the density of γ-photons significantly more than a plane target, when two colliding circularly polarized lasers irradiate the target.By multi-laser irradiating the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping.Hence, γ-photons with a high density of beyond 5000 ncare obtained through nonlinear Compton backscattering.Meanwhile, 2.7×1011 positrons with an average energy of 230 MeV are achieved via the multiphoton Breit-Wheeler process.Such an ultrabright γ-ray source and dense positron source can be useful in many applications.The optimal target radius and laser mismatching deviation parameters are also discussed in detail.展开更多
The dynamics of the confinement transition from L mode to H mode（LH） is investigated in detail theoretically via the extended three-wave coupling model describing the interaction of turbulence and zonal flow（ZF） f...The dynamics of the confinement transition from L mode to H mode（LH） is investigated in detail theoretically via the extended three-wave coupling model describing the interaction of turbulence and zonal flow（ZF） for the first time.Thereinto, turbulence is divided into a positive-frequency（PF） wave and a negative-frequency（NF） one, and the gradient of pressure is added as the auxiliary energy for the system. The LH confinement transition is observed for a sufficiently high input energy. Moreover, it is found that the rotation direction of the limit cycle oscillation（LCO） of PF wave and pressure gradient is reversed during the transition. The mechanism is illustrated by exploring the wave phases. The results presented here provide a new insight into the analysis of the LH transition, which is helpful for the experiments on the fusion devices.展开更多
The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate ...The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc.展开更多
文摘A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating,accelerating and guiding protons,using a single-cone target with a beam collimator through a target normal sheath acceleration mechanism.In addition,the problems involved are studied by using two-dimensional particle-in-cell simulations.The results show that the proton beam can be collimated,accelerated and guided effectively through this type of target.Theoretically,a formula is derived for the combined electric field of accelerating protons.Compared with a proton beam without a beam collimator,the proton beam density and cut-off energy of protons in the type II are increased by 3.3 times and 10%respectively.Detailed analysis shows that the enhancement is mainly due to the compact and strong sheath electrostatic field,and that the beam collimator plays a role in focusing energy.In addition,the simulation results show that the divergence angle of the proton beam in type II is less than 1.67 times that of type I.The more prominent point is that the proton number of type II is 2.2 times higher than that of type I.This kind of target has important applications in many fields,such as fast ion ignition in inertial fusion,high energy physics and proton therapy.
基金supported by the National Natural Science Foundation of China (Nos.11875007, 11305010)supported by the STFC Cockcroft Institute core grant
文摘A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is found that the circular target can enhance the density of γ-photons significantly more than a plane target, when two colliding circularly polarized lasers irradiate the target.By multi-laser irradiating the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping.Hence, γ-photons with a high density of beyond 5000 ncare obtained through nonlinear Compton backscattering.Meanwhile, 2.7×1011 positrons with an average energy of 230 MeV are achieved via the multiphoton Breit-Wheeler process.Such an ultrabright γ-ray source and dense positron source can be useful in many applications.The optimal target radius and laser mismatching deviation parameters are also discussed in detail.
基金supported by the National Natural Science Foundation of China(Grant Nos.11305010 and 11475026)the Joint Foundation of the National Natural Science FoundationChina Academy of Engineering Physics(Grant No.U1530153)
文摘The dynamics of the confinement transition from L mode to H mode（LH） is investigated in detail theoretically via the extended three-wave coupling model describing the interaction of turbulence and zonal flow（ZF） for the first time.Thereinto, turbulence is divided into a positive-frequency（PF） wave and a negative-frequency（NF） one, and the gradient of pressure is added as the auxiliary energy for the system. The LH confinement transition is observed for a sufficiently high input energy. Moreover, it is found that the rotation direction of the limit cycle oscillation（LCO） of PF wave and pressure gradient is reversed during the transition. The mechanism is illustrated by exploring the wave phases. The results presented here provide a new insight into the analysis of the LH transition, which is helpful for the experiments on the fusion devices.
基金supported by National Natural Science Foundation of China(NSFC)under Grant Nos.11475026,11664039 and 11305010
文摘The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc.
