Schlieren diagnostics of pulsed electron beam ablation of polymethyl-methacrylate

Abstract

The investigation of the interaction of pulsed electron beams with PMMA (polymethylmethacrylate) targets is reported. The electron beam of some 10⁻⁸ s in duration is produced in a pulsed low-pressure gas discharge. The beam power density of up to 10⁸ W/cm² leads to a surface plasma formation similar to that of the pulsed laser ablation process. The propagation of the ablated material and the shock wave inside the PMMA target are observed by means of Schlieren diagnostics. An electron density gradient of over 3×10¹⁹ cm⁻⁴ has been observed in the expanding plasma up to 1.5 μs after the plasma formation. During the early stage of expansion, the expansion velocity of the plasma plume as determined by the steep electron density gradient is around 10⁵ cm/s. The pressure behind the shock front inside the PMMA target as determined from the shock velocity exceeds 0.3 Gpa.