Size Effects of Vacuum Chamber for H- (D-) Ion Volume Production by Sheet Plasma 1

摘要

In order to produce H- (D-) ions effectively by volume production in the sheet plasma, effects of vacuum chamber are studied by using two sizes of metal vacuum chamber and by changing their bias voltages for the plasma potential of the sheet plasma. Then, we find the H- (D-) ion current increases abruptly with distance between the sheet plasma surface and the chamber wall perpendicular to the magnetic field, while it takes a maximum near a floating potential of the chamber (negative for the plasma potential outside of the sheet plasma). These effects are related with a size of space where the plasma potential is higher than those of boundaries parallel and perpendicular to the magnetic field. That is, the H- (D-) ion current increases with the spatial size which H- (D-) ions are confined and hydrogen (deuteron) positive ions are lost rapidly along the magnetic field.