부산대학교 도서관

We describe an omegatron-type mass spectrometer used for measurement of the molecular and atomic ion concentrations as well as the ion species temperatures in hydrogenic plasmas. The experiments were performed in the PISCES-A linear plasma experiment with electron densities n{approx}10{sup 11}--10{sup 12}cm{sup -3}, ion temperatures T{sub i}{approx}2--8eV, electron temperatures T{sub e}{approx}3--30eV, and magnetic fields B=0.8--1.9kG. The resulting mass spectra show clear evidence of atomic hydrogen H{sup +}, as well as of the molecular ions H{sub 2}{sup +} and H{sub 3}{sup +}, with H{sup +} and H{sub 3}{sup +} usually being dominant. It is found that large electron repeller voltages ({approx}-200 V) are important for preventing electrons from entering the diagnostic region and ionizing the residual gas. The relative peak heights for the different ions are found to vary as a function of ion repeller voltage, probably due to differences in ion temperature.