Production of negative ion plasmas in a Q machine

A negative ion plasma is produced by introducing a small amount of SF 6 gas into a low-temperature ( approximately=0.2 eV) potassium plasma produced in a Q machine. The density ratio of negative to positive ions is continuously varied in the range up to more than 0.9999, where there appears a remarkable decrease in electron shielding for potential variations, yielding a clear effect on plasma collective phenomena. By introducing fullerene (C 60 )particles into the Q-machine plasma, we can produce a plasma including large negative C 60 ions. This ultrafine particle plasma might prove very attractive in fields of materials science.