Ions emitted by a pulsed titanium-hydride spark plasma source

The mass and velocity distributions of ions from a pulsed titanium-deuteride arc plasma source in vacuum were measured by a time-of-flight mass spectrometer. The arc source consisted of a thin deuterium-loaded titanium layer between two electrodes on an alumina substrate with a narrow groove across the center. Operation of the plasma source by 0.25, 0.75, and 2.1 μs 100 A pulses eroded the cathode side of the groove. The deuterium ions were found to have mean velocities only 20% higher than the ⁺⁺Ti ions. Almost all the deuterium ions were emitted during the first 0.75 μs of the pulse. The titanium ions had charge states of 1+, 2+, and 3+, with 2+ predominating. Their mean energy-per charge state decreased slightly with increasing charge state. The findings are interpreted as arising from a dense cathode spot in which acceleration of the ions occurs and in which ion-ion and ion-atom collisions slow down the very light ions