Experiments on Carbon Balmer-.ALPHA. Soft X-Ray Lasers Pumped with a 12ps KrF Laser.

Abstract

Carbon Balmer-α soft X-ray lasers were studied by using a KrF Raman laser system (SPRITE) at the Rutherford Appleton Laboratory in UK. The studies were carried out in collaboration of the Rutherford Appleton Laboratory and the Institute of Laser Engineering, Osaka University. Carbon fiber targets (7μm in diameter) were irradiated with a 268nm laser light at a pulse duration of 12ps, an energy of 5J and an average irradiance of 3×1014W/cm2. Time resolved Balmer-α (18.2nm) intensity from hydrogen-like carbon ions was measured with a flat-field XUV spectrometer coupled to a streak camera. The gain in the Balmer-α transition observed at 4 mrad from the target axis showed gain after 200ps from the pump laser irradiation. Experimental results were compared with a time dependent average-atomic-model coupled with a hydrodynamic code (MEDUSA102). We take into account of effects of nonuniformity of the absorption irradiance to explain small gain observed in the experiment.