Study of Optical Emission During Spallative Ablation Induced by Soft X-Ray Laser Pulses

Soft x-ray laser (SXRL) pulses were irradiated to the surfaces of LiF, Al, and Cu plate targets. On all irradiated target surfaces, the ablation and/or surface modification structures caused by the SXRL pulse irradiations were confirmed. However, the optical emission (visible spectral range) from the surfaces during the SXRL pulse irradiations were not observed, in spite of high sensitive registration technique. The theoretical model calculations for the interaction between SXRL pulse and material surfaces has revealed the spallative ablation of target surface with a low electron temperature. Our experimental results is consistent with the theoretical model calculations, qualitatively.