Hot electron velocity distribution in ultra-short laser produced plasma diagnosed with X-ray polarization spectroscopy

Polarization degree of helium-like Cl-Heαline (1s21S0- 1s2p 1P1) from a chrolinated triple-layer target was measured using a 130 fs laser pulse at 1017W/cm2. The polarization degree was given as a function of overcoat thickness. It was found that the emission from a layer closer to the target surface is polarized parallel to the surface direction whereas emission from a deeper region in perpendicular to the surface. The experimental result was analyzed using a two dimensional (2D) Maxwellian distribution function for hot electrons. Beam-like distribution was found in the depth of plasma.