Tsutomu Tetsuka

Ion extraction characteristics by an electric field on laser-produced barium plasma

Time evolution of a two‐dimensional ion‐density distribution in a barium plasma produced by simultaneously illuminating a tuned dye laser light and an excimer laser light has been measured by means of laser‐induced fluorescence technique to investigate the ion extraction characteristics by an electric field. When the plasma is produced between two parallel plates with a potential difference, the ion behavior is governed by three factors: bulk plasma flow, plasma diffusion, and ion extraction by the electric field. The flow velocity of the bulk plasma is equal to the mean velocity of the atoms emanating from a hot source. The expansion velocity of the plasma boundary into a vacuum agrees well with the ambipolar expansion velocity corresponding to that of an ion acoustic wave, while the diffusion coefficient obtained from the density decay rate is smaller by a factor of about 8 than the ambipolar expansion coefficient for the steady state because of low collision frequency between ions. Enhancement of the i...

Ion extraction characteristics on a barium plasma produced between grounded parallel plate electrodes and a positively biased upper plate electrode

When a barium plasma was suddenly produced between parallel plate electrodes and an upper plate electrode with a higher potential, the ion extraction was investigated in comparison with characteristics of the usual parallel plate electrode configuration. The parameter dependencies of ion extraction time by an external electric field, measured under a variety of experimental conditions, led to the conclusion that the ion extraction time can be expressed as the product of exponents of the applied voltage, plasma width, and ion density as well as the parallel plate electrodes. This scaling relation estimates the ion extraction time with an accuracy of 15% for a given parameter set. Comparison of the scaling relations for the new electrode concept with a highly biased upper plate electrode and the parallel plate electrodes showed that the former improves the ion extraction time by a maximum factor of 2.6.

New scaling relation for ion extraction by external electric field on a barium plasma produced between parallel-plate electrodes

Parameter dependencies of ion extraction time by an external electric field have been investigated by using barium plasmas suddenly produced between parallel‐plate electrodes under a variety of experimental conditions. It is concluded that the ion extraction time can be expressed as the product of exponents of the three controllable parameters, applied voltage, plasma width, and ion density. This scaling relation can estimate the ion extraction time with an accuracy of 15% for a given controllable parameter set, supporting its universality.