Diagnostics for Hydrogen Atoms and Molecules in H-Atom Sources and Beams Using VUV Laser Light.

摘要

An H(-) ion source for high brightness H atoms beams should have the lowest possible internal temperature T, because the beam-power density at a distance scales as 1/T. We determine local Temperature 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 monitor 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). Keywords: Neutral beam, Ion source diagnostics, Laser diagnostics, REMPI, Particle accelerator components, Physics. (JG)