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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.

An experimental study of the enhancement of the electron temperature of a laser-induced plasma by use of radio-frequency dielectric heating has been carried out. A radio-frequency electric field of 140 MHz is used to heat the plasma produced by multistep resonant photoinization. It is clearly observed that the electron temperature increases from 0.3 to 1.0 eV when a radio-frequency input power of 1.0 W is applied. Also, applying heating induces a plasma oscillation. This is due to the generation of ion waves in the plasma, and therefore, means that the enhanced electron temperature is higher than the ion temperature. It is expected that this method will improve the efficiency for extracting ions rapidly from a laser-induced plasma in atomic vapor laser isotope separation.