Excitation Behavior of Rare Gases in Low-Energy Plasma

Heavy rare gases like Xe have the highest abundance as fission products formed with dependence on the burnup of nuclear fuels. The interaction between heavy rare gases and low-energy electrons excited by the irradiation effect is very important for understanding the gas release mechanism and for developing the collecting method of radioactive fission product gases. Two types of plasma-testing apparatuses for the opened and closed low-energy plasmas were arranged using the radio frequency exciting source. The excitation behavior was evaluated by measuring the density and the temperature of the excited electrons. The electron density in the opened plasma increased with increase of the ionization energy of each rare gas. However, the electron density in the closed plasma of heavy rare gases (Ar, Kr, and Xe) was enhanced nearly a thousand times higher than that of light rare gases (Ne and He). The difference was interpreted as based on the cross section for energy transfer to the low-energy electron formed by the multisputtering effect on wall surfaces in the closed plasma.