Study of the angular dependence of radiation emission from short pulse laser-thin foil interactions

The radiation background generated by the interaction of an intense laser with thin plastic foils has caused adverse signal crosstalk in simultaneous transverse laser driven radiography experiments and is thought to be dominated by energetic electrons [1]. To better characterize this radiation background, the OMEGA EP backlighter laser (0.7 ps, 250-500 J, >4e19 W/cm2) was used to drive a range of thin polystyrene foils (300-1500 nm thick) where the spectral distribution of electrons was measured as a function of angle. These measurements were gathered with the Wide-Angle X-ray and Electron Spectrometer (WAXES), which utilizes a set of six filter stack spectrometers (FSS’s) oriented around the laser target in 45-degree increments, resulting in 270 degrees of angular range around the target. The FSS’s consisted of alternating layers of filter material (Al, Sn, or Ta) and radiochromic film, giving up to 14 spectral resolution steps of electron energy between 0.5 and 30 MeV. Analysis which includes a spatial and spectral reconstruction of the radiation background for a target thickness scan, a laser energy scan, and a comparison between normal laser incidence and oblique (45 deg) laser incidence is given in this work.

[1] Wong, Chun-Shang, et al. "Mitigation and characterization of crosstalk between laser-driven radiography sources." High Energy Density Physics 52 (2024): 101133.