Abstract
In order to produce H- (D-) ions effectively by volume production in a sheet plasma, effects of vacuum chamber are studied by using two sizes of metal vacuum chamber and by changing their bias voltages with respect to the sheet plasma. Then, we find the H- (D-) ion current increases abruptly with the increase of width of the chamber 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. That is, the H- (D-) ion current increases with the spatial size in which H- (D-) ions are confined and hydrogen (deuteron) positive ions are lost rapidly along the magnetic field.
