Drift velocity of gadolinium plasma generated in the vicinity of electron beam evaporation source

By electron beam heating and evaporation, the atom beam of the metals having high melting point can be obtained easily. At the same time, due to the ionization of atoms by electron beam in the vicinity of evaporation sources, plasma arises. It was pointed out by Graper that this plasma exists at the place several tens cm distant from the evaporation source by drift. In order to carry out atom collision experiment or laser isotope separation by using only atom beam, the inflow of plasma must be restrained, but in CVD or ion plating, plasma plays an important role. It is important to know the characteristics of plasma in both cases. In this study, it was attempted to measure the drift velocity of the gadolinium plasma generated in the vicinity of evaporation part by the method using a Langmuir's probe. The experimental setup, the measurement of plasma drift velocity by delay time method and the experimental results are reported. The velocity of ions was 1.3 - 1.4 times as fast as that of the atom beam, and nearly agreed with the value calculated by assuming the acceleration due to the spatial potential difference of plasma. (K.I.)