Physical characteristics of ion extraction simulation system based on gas discharge plasma jet

Abstract

In an atomic vapor laser isotope separation process, the required isotope atoms are ionized selectively by a pulsed laser with a specific narrow line width, and then the produced isotope ions are extracted to the collected plates under an externally applied electromagnetic field. In the whole ion separation process, the ion extraction sub-process is one of the most important physical processes. Previous studies have shown that the key parameters of the laser-induced plasma, e.g., the initial electron number density and temperature, have a significant influence on the ion extraction features. In an actual isotope separation process, a specifically designed laser is necessary to produce the required isotope ions, which, however, leads the whole facility to have a very complicated structure, high capital cost, and especially, very narrow window of the key plasma parameters. These will, to some extent, limit a more in-depth investigation of the influences of the key plasma parameters on the ion extraction characteristics. In this paper, an ion extraction platform (ion extraction simulation experimental platform-2015, IEX-2015) is developed on the basis of a gas discharge plasma jet driven by a kilo-hertz high-voltage power supply. And an argon plasma collisional-radiative model is established to measure the electron temperature and number density in the plasma jet region. The experimental results show that the power input and driving frequency of the power supply and the argon mass flow rate can all affect the electron temperature and electron number density. The measured variation ranges of the electron number density and temperature are 109-1011 cm-3 and 1.7-2.8 eV, respectively, under a chamber pressure on the order of 10-2 Pa, which are close to the parameter levels in the actual ion extraction process. Subsequently, the preliminary ion extraction experiments are conducted under different extraction conditions including different externally applied voltages, different electrode distances and different plasma densities. The experimental results are also qualitatively consistent with those in an actual ion extraction process. The preceding preliminary experimental results show that it is feasible to conduct the ion extraction simulation study on IEX-2015. This is very helpful for systematically studying the ion extraction characteristics under different operating conditions in our future research.