Capdessus Remi, King Martin, Del Sorbo Dario, Duff Matthew, Ridgers Christopher P, McKenna Paul
SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
York Plasma Institute, Department of Physics, University of York, York, YO10 5DQ, UK.
Sci Rep. 2018 Jun 14;8(1):9155. doi: 10.1038/s41598-018-27122-9.
The relativistic Doppler effect is one of the most famous implications of the principles of special relativity and is intrinsic to moving radiation sources, relativistic optics and many astrophysical phenomena. It occurs in the case of a plasma sail accelerated to relativistic velocities by an external driver, such as an ultra-intense laser pulse. Here we show that the relativistic Doppler effect on the high energy synchrotron photon emission (~10 MeV), strongly depends on two intrinsic properties of the plasma (charge state and ion mass) and the transverse extent of the driver. When the moving plasma becomes relativistically transparent to the driver, we show that the γ-ray emission is Doppler-boosted and the angular emission decreases; optimal for the highest charge-to-mass ratio ion species (i.e. a hydrogen plasma). This provides new fundamental insight into the generation of γ-rays in extreme conditions and informs related experiments using multi-petawatt laser facilities.
相对论多普勒效应是狭义相对论原理最著名的推论之一，是移动辐射源、相对论光学和许多天体物理现象所固有的。它发生在等离子体帆被外部驱动源（如超强激光脉冲）加速到相对论速度的情况下。在这里，我们表明相对论多普勒效应在高能同步辐射光子发射（约10兆电子伏特）上，强烈依赖于等离子体的两个固有特性（电荷态和离子质量）以及驱动源的横向范围。当移动的等离子体对驱动源变得相对论性透明时，我们表明γ射线发射会受到多普勒增强，并且角发射会减小；对于最高荷质比的离子种类（即氢等离子体）是最优的。这为极端条件下γ射线的产生提供了新的基本见解，并为使用多拍瓦激光设施的相关实验提供了参考。
