Optimization of X-Ray Laser Pumping in Recombining Plasma Scheme

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Atomic processes and the effect of irradiation schemes has been investigated in the recombination x-ray laser.1.Soft x-ray spectroscopy of x-ray laser media in the recombining plasma schemeA new soft x-ray spectrograph has been designed and constructed for diagnostics of highly ionized aluminum plasmas. The absolute calibration of the soft x-ray spectrograph was performed for the wavelength range from 2 to 5 nm by using synchrotron radiation or laserproduced plasma. Spectroscopic analyses showed that the electron temperature was very low in the plasma where the population inversion was produced and the measured population density of excited state of Li-like ions agreed well with the calculated population density from the new CR model that included doubly excited states of Be-like ions.2.Effects of irradiation scheme(1)Pulse-train irradiationEffects of irradiation scheme on x-ray laser gain production were investigated systematically for the three types of pulse-train waveform. Plasma hydrodynamics simulation was also performed to search the time history of plasma parameters for each pulse-train waveform. The experimental results have been interpreted by combining the simulation and the new CR model calculation.(2)Micro-dot-array irradiationThe micro-dot-array irradiation pattern was produced by using a new line-focus optics with a segmented prism array for a YAG laser beam. It was confirmed that the plasma produced by this irradiation method could expand rapidly and could reduce its electron temperature faster than that in a plasma produced by a smooth line focus irradiation.