Relationship between production and extraction of D/H negative ions in a volume negative ion source

Pure volume production of D negative ions is studied in rectangular negative ion source equipped with an external magnetic filter (MF). Production and control of D2 plasma with the MF is nearly the same as that of H2 plasmas. Plasma parameters (ne and Te) in D2 plasmas are varied mainly in the downstream region by changing the magnetic field intensity of the MF (i.e., BMF), although the values of ne and Te in D2 plasmas are slightly higher than that of H2 plasmas. With choosing the optimum combination of gas pressure and BMF, plasma conditions are well controlled for volume production of D/H ions. With decreasing BMF from 150 Gauss to 80 Gauss, negative ion production increases in its value, and D production (or density) is nearly the same as H production at the optimum gas pressure. Depending on BMF, however, extraction of D current is limited in low level compared to that of H current although D production is nearly the same as H production. Optimum gas pressure for D production is slightly higher than that for H production.