Isotope Effect of H – /D – Volume Production in Low‐Pressure H 2 /D 2 Plasmas – Measurement of VUV Emissions and Negative Ion Densities

Isotope effect on H – /D – volume production is studied by measuring both VUV emission and negative ion density in the source. In a double plasma type source, under some discharge conditions, extracted D – currents are nearly the same as H – currents, although VUV emission intensity (corresponding to production of vibrationally excited molecules) in D 2 plasmas is slightly lower than that in H 2 plasmas. Considering the factor √2 due to mass difference, D – ion density in the extraction region of the source is higher than H – ion density. In another experiment with a rectangular arc chamber, axial distributions of H – /D – ion densities in the source are measured directly using a laser photodetachment method. Relationship between H – /D – production and plasma parameter control with using a magnetic filter (MF) is discussed. Furthermore, relative intensities of extracted negative ion currents are discussed compared with the negative ion densities in the source. Production and control of D 2 plasmas are well realized with the MF including good combination between the filament position and field intensity of the MF. Extracted H – and D – currents depend directly on negative ion densities in the source. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)