Characteristics of Sub-100-Ps Laser Irradiation of Cylindrical Cavities

Laser irradiation of cylindrical cavities has attracted considerable interest in the context of soft x-ray laser experiments because the confined plasma may act as an x-ray waveguide. Waveguiding requires a concave, radially symmetric density profile and thus uniform plasma ablation inside the cavity. In the case of transverse irradiation presented in this work, the uniformity of plasma ablation is primarily determined by the mechanisms which redistribute the energy from the initial location of plasma generation by the incident laser. Among the mechanisms to be considered are x-radiation, hot electrons, and laser light reflected at the primary spot. Experimentally, evidence was found that for short-pulse, long-wavelength, high-irradiance conditions, the redistribution of energy is dominated by reflected laser light.