Ion extraction from a cold plasma produced by laser multiphoton ionization has been enhanced by using radio-frequency (140 MHz) dielectric plasma heating. When 10 W in heating power is applied to a plasma of ion density around 3×1010 cm−3, it is observed that the peak ion flux extracted with an electrostatic voltage of 20 V increases by a factor of more than 2. The time for extracting all the ions becomes short by a factor of 3 without any production of radio-frequency discharged plasma. It is considered that these results are due to the increase in the electron temperature of the plasma. This method will be very useful for the process of ion extraction in atomic vapor laser isotope separation.

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The temporal change of thermal lens effects has been measured for the development of high efficient laser system. Ytterbium phosphate glass was used due to its high saturation fluence property. A free running flashlamp pumped Ti:sapphire laser was developed for the high energy pump source. Pumping intensity on the glass surface exceeded 800 kW/cm 2 which is enough high for laser diode simulator. Shack-Hartmann wavefront sensor system was applied to measure the thermal lens effects on a highly pumped ytterbium glass oscillator. The temporal change of wavefront was successfully measured at high repetition rate of 100 Hz. The measured wavefront were expanded to Zernike coefficients. Cooling process for the focus coefficient agreed well with the prediction of unsteady one dimensional heat conduction.

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