Generation of arbitrarily polarized GeV lepton beams via nonlinear Breit-Wheeler process

Generation of arbitrarily spin-polarized electron and positron beams has been investigated in the single-shot interaction of high-energy polarized r-photons with an ultraintense asymmetric laser pulse via nonlinear Breit-Wheeler pair production.We develop a fully spin-resolved semi-classical Monte Carlo method to describe the pair creation and polarization.In the considered general setup,there are two sources of the polarization of created pairs:the spin angular momentum transfer from the polarized parent-photons,as well as the asymmetry and polarization of the driving laser field.This allows to develop a highly sensitive tool to control the polarization of created electrons and positrons.Thus,dense GeV lepton beams with average polarization degree up to about 80%,adjustable continuously between the transverse and longitudinal components,can be obtained by our all-optical method with currently achievable laser facilities,which could find an application as injectors of the polarized e^(+)e^(-)collider to search for new physics beyond the Standard Model.

光子对撞机产生正负电子对的数值方法

光子对撞产生正负电子对的Breit-Wheeler过程,是由能量直接产生物质的过程,在物质的起源与光子物理理论的研究中有着极为重要的作用.随着激光与物质作用产生γ光源品质的提升,使得在实验室首次观测双光子对撞的Breit-Wheeler过程成为,可能.针对光子对撞机的数值模拟方法,本文提出了一种基于严格的双光子对撞动力学过程的计算电子产额与动力学参数的数值方法.在对Breit-Wheeler过程的模拟中,根据光子的运动规律将光子划分为定量的区块,检测区块的对撞,然后在区块内部以动力学原理检测光子是否发生对撞,该方法可以有效提升计算模拟的效率.同时,该方法与已经发表的理论结果进行了比较,发现该计算结果与理论结果高度一致.应用这一数值方法,能够为Breit-Wheeler过程给出较为精确的模拟结果,也可以为未来γγ对撞机的实验设计提供参照.

High density γ-ray emission and dense positron production via multi-laser driven circular target

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.

Dense positrons and γ-rays generation by lasers interacting with convex target

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.

Controlled Fusion Strategy Using Ultra-Intense Laser Derived Positron Generation for Initiation

A controllable strategy for eliciting nuclear fusion is presented through ultra-intenselaser derived positron generation by a conceptual first physics perspective. The capability to generate positrons on demand in a controlled manner through an ultra-intense laser incident on a high atomic number target, such as gold, is the intrinsic core to the foundation of controllable nuclear fusion. Positron antimatter generated from the periphery of the fusion fuel pellet provides the basis for initiating the fusion reaction, which is regulated by controlling the operation of the ultra-intense laser. A dual pulsed Fast Ignition mechanism is selected to achieve the fusion reaction. Based on first physics performance analysis the controllable strategy for eliciting nuclear fusion through ultra-intenselaser derived positron generation offers a realizable means for achieving regulated nuclear fusion. A future perspective of the controllable fusion strategy addresses the opportunities and concerns of a pathway toward regulated nuclear fusion.

Quantum electrodynamics experiments with colliding petawatt laser pulses

A new generation of high power laser facilities will provide laser pulses with extremely high powers of 10 petawatt(PW)and even 100 PW, capable of reaching intensities of 1023 W/cm^2 in the laser focus. These ultra-high intensities are nevertheless lower than the Schwinger intensity IS= 2.3×1029 W/cm^2 at which the theory of quantum electrodynamics(QED) predicts that a large part of the energy of the laser photons will be transformed to hard Gamma-ray photons and even to matter, via electron–positron pair production. To enable the investigation of this physics at the intensities achievable with the next generation of high power laser facilities, an approach involving the interaction of two colliding PW laser pulses is being adopted. Theoretical simulations predict strong QED effects with colliding laser pulses of 10 PW focused to intensities 10^(22) W/cm^2.