激光-近临界等离子体高能高亮度X射线的产生

Production of bright high-energy X-rays based on interaction of laser and near-critical-density plasma

基于激光驱动超热电子产生的高品质X射线源是高能量密度实验中有效的诊断技术手段,对辐射源亮度、穿透性和时空分辨率等特性具有极高的要求。结合粒子模拟和蒙特卡罗模拟研究,首先利用近临界密度等离子体实现了激光自聚焦通道中的大电量高能电子加速,通过直接加速机制产生了电量超过600nC、有效温度可达15 MeV的高能电子;以此为基础提高电子-光子能量转换率,有效优化了光子能量和产额,并通过一定的转换靶参数优化方案产生了微焦点(FWHM小于200μm)、高能、高亮度X射线,为高空间分辨(小于200μm)成像诊断提供了很好的途径,有望早日实现激光等离子体轫致辐射单脉冲瞬态照相的实际应用。

Laser-driven electrons can produce high-quality X-ray source with broad applications including measurement of shock-compressed matters, inertial confinement fusion and laboratory astrophysics.For high energy density experiments, bright high-resolution diagnosis radiation is required.To meet the requirement, it is decisive to optimize the production of hot electrons and radiation emission.In this paper, we combine the Particle-In-Cell and Monte Carlo simulation, firstly use near-critical-density plasma to accelerate high-charge energetic electrons （exceeds 600 nC, 15 MeV） by direct laser acceleration in self-focusing channel, then get enhanced energy conversion between electrons and photons, finally obtain brilliant micro-spot （FWHM〈200 μm） high-energy X-rays via parameter optimization.Our findings provide a promising access to high-spatial-resolution （〈200 μm） diagnostics, and it is hopeful to realize single-pulse transient imaging based on laser-plasma bremsstrahlung source.