25 July 1989 Diagnostics In H2 Discharges Using A Tunable 193nm Excimer Laser
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Abstract
An H- source for high brightness H° beams should have the lowest possible internal temperature T, because the beam-power density at a distance scales as 1/T. We determine local T inside a discharge with the use of a tunable ArF excimer laser that measures the populations of the lowest four rotational states of H2 by means of (2+1) resonance enhanced multiphoton ionization (REMPI). The number of laser-created ions causes a proportional change of the discharge's electrical impedance. A calibration in room temperature H2 (without a discharge) showed that the REMPI works well. Another objective is to develop a monitor for the vibrationally excited molecules, H2(v), that are believed to be the primary origin of H- within volume-type ion sources. We use the same apparatus and approach, but add a Raman shifter to change the laser wavelengths to those appropriate for (2+1) REMPI of H2(v).
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Lynne M. Hitchcock, Gene P. Reck, Erhard W. Rothe, C. C. Tung, "Diagnostics In H2 Discharges Using A Tunable 193nm Excimer Laser", Proc. SPIE 1061, Microwave and Particle Beam Sources and Directed Energy Concepts, (25 July 1989); doi: 10.1117/12.951850; https://doi.org/10.1117/12.951850
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