通过laser -等离子体相互作用产生高极化高能亮$γ$ -射线
Generation of highly-polarized high-energy brilliant $γ$-rays via laser-plasma interaction
摘要：
在量子辐射-反应体系中研究了激光-等离子体相互作用产生高偏振高能明亮$γ$ -射线。我们采用量子电动力学的粒子在细胞的代码来描述自旋分辨电子动力学半经典和光子发射和偏振量子力学的局部恒定场近似。当超强线偏振（LP）激光脉冲照射到近临界密度（NCD）等离子体上后，再照射平面铝靶时，NCD等离子体中的电子首先被驱动激光加速到超相对论能量，然后与铝靶反射的激光脉冲迎面碰撞，由于非线性康普顿散射，发射明亮的LP $γ$ -射线，平均偏振度约为70%，能量高达数百MeV。通过比较发现，采用填充NCD等离子体的锥形金靶时，由于等离子体中强激光驱动的准静态磁场的增强，发射的$γ$射线束的线偏振度、准直度和亮度都得到了显著改善。这种$γ$射线可以用目前可实现的激光设备产生，并在高能物理学和天体物理学中找到各种应用。
英文摘要：
Generation of highly-polarized high-energy brilliant $γ$-rays via laser-plasma interaction has been investigated in the quantum radiation-reaction regime. We employ a quantum-electrodynamics particle-in-cell code to describe spin-resolved electron dynamics semiclassically and photon emission and polarization quantum mechanically in the local constant field approximation. As an ultrastrong linearly-polarized (LP) laser pulse irradiates on a near-critical-density (NCD) plasma followed by an ultrathin planar aluminum target, the electrons in NCD plasma are first accelerated by the driving laser to ultrarelativistic energies, and then head-on collide with reflected laser pulse by the aluminum target, emitting brilliant LP $γ$-rays due to nonlinear Compton scattering with an average polarization of about 70\% and energy up to hundreds of MeV. By comparison, as a conical gold target filled with NCD plasma is employed, the linear polarization degree, collimation and brilliance of emitted $γ$-ray beam are all significantly improved due to the enhanced strong laser-driven quasi-static magnetic field in plasmas. Such $γ$-rays can be produced with currently achievable laser facilities and find various applications in high-energy physics and astrophysics.
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