Volume Production of D Negative Ions in Low-Pressure D2 Plasmas - Negative Ion Densities versus Plasma Parameters -

Volume production of D negative ions including isotope effects is studied in a rectangular arc chamber. Production and control of plasma parameters in D2 plasmas are performed by varying the intensity of the magnetic filter. The values of Te and ne in D2 plasmas are slightly higher than ones in H2 plasmas. Te in D2 plasmas cannot be decreased and is kept above 1 eV in the extraction region with the same MF intensity for optimizing H2 plasmas. The stronger MF field is required for control of Te in D2 plasmas. Therefore, plasma production between H2 and D2 plasmas is different from each other. Namely isotope effect of plasma production is observed. H and D densities have different spatial distributions corresponding to those different plasma parameters. Extracted H and D currents are mainly determined by H and D densities in front of the extraction hole, respectively. According to the discussions based on estimated rate coefficient and collision frequency of main collision processes, it is reconfirmed that Te in the extraction region should be reduced below 1 eV with ne keeping higher for enhancement of H and D production. For studying enhancement of D production, preliminary results on VUV emission measurement is presented and discussed briefly.