Ion extraction characteristics of the laser induced plasma between grounded parallel plate cathodes and upper short plate anodes

For ion extraction in atomic vapor laser isotope separation, anode size should be as small as possible in order to simplify the structure of the ion extraction electrodes. However, too small an anode size may prevent ion extraction. The ion extraction characteristics of a photo-ionized Gd plasma were measured in a simplified electrode configuration, in which the anode size was smaller than that of the cathode. It was found that when the ratio of the anode area to the cathode area was less than 0.1%, the ions could not be extracted rapidly because of the delay in the rise of plasma potential brought about by the effect of the electron space charge. Therefore, it is necessary for rapid ion extraction that the anode area is large enough to raise the plasma potential rapidly. (author)