Measurements of the angular dependence of electron emission from short pulse laser matter interactions

A new diagnostic, the Wide-Angle X-ray and Electron Spectrometer (WAXES) was designed and fielded on the OMEGA EP laser to investigate the radiation environment arising from intense laser matter interactions. Specifically, the angular distribution of electron spectra was measured when a 0.7 ps, 250-500 J (> 4×10²⁰ W/cm²) laser was focused onto 750 nm thick CH plastic foils. Energetic electrons are thought to contribute mostly to the radiation environment surrounding such laser-target interactions, impacting simultaneous transverse laser driven radiography experiments through signal crosstalk. WAXES measures the angular electron spectral distribution through a set of six filter stack spectrometers (FSS’s) oriented around the laser target in 45-degree increments, resulting in a total of 270 degrees of angular range around the target. The filter stack spectrometers consisted of alternating layers of filter material (Al and Ta) and radiochromic film (RCF), resulting in 12 spectral resolution steps of electron energy between 0.5 and 20 MeV. Preliminary analysis of the WAXES FSS’s, including a spectral reconstruction, along with spatial analysis of the radiation environment is given.