Enhanced ion charge states in vacuum arc plasmas using a “current spike” method

Ion charge state distributions of vacuum arc ion sources are correlated to the arc operating voltage. An enhancement of ion charge state via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. A current spike of 100–1000 A and several microseconds width was produced on top of the main arc current pulse (100 A, 250 μs). The ion charge state distribution was measured by charge-to-mass spectrometry. The measured charge state distributions were used as input data to the plasma model of partial local Saha equilibrium, giving the time-dependent electron temperature of the plasma at the freezing zone near the cathode spot.