Anisotropic production of laser-plasma soft x rays and fast electrons from thin plastic targets

Abstract

In separate experiments incident pulses from two different Nd‐glass lasers and a CO₂ laser were fired at planar targets of thin plastic, and the angular distributions of the soft x rays and fast electrons were measured. The focused power densities of the first Nd‐glass laser and the CO₂ laser were 2×10¹² W/mm², of the second Nd‐glass laser, 2×10¹³ W/mm². The electron efficiency of the CO₂ laser plasmas is strongly peaked antiparallel to the incident pulse, the backward‐to‐forward ratio being 100. The electron efficiency of both Nd‐glass lasers is less than 150% of their x‐ray efficiency. The x‐ray efficiencies of the Nd‐glass laser plasmas are at least an order of magnitude greater than that of the CO₂ laser plasmas. The x‐ray efficiency of the first Nd‐glass laser was isotropic. The x‐ray distribution for both the second Nd‐glass laser and the CO₂ laser plasmas had the backward‐to‐forward ratio of 4.