Laser-beam characteristics of Phoenix, an HF oscillator-amplifier system

Abstract
Energy‐extraction and beam‐quality measurements are reported for Phoenix, Sandia’s high‐energy HF laser system. The final amplifier in this oscillator‐amplifier chain used electron‐beam initiation of high‐pressure gas mixtures of H2‐F2‐O2. The oscillator and preamplifier utilized fast electric discharges in SF6‐HI mixtures. Energy‐extraction efficiency using this oscillator system was the same as that previously determined using an H2‐F2‐O2‐fueled oscillator which produced a better spectral match to the amplifier but which yielded poorer beam quality. Lateral shearing interferograms showed no significant phase‐front degradation of the beam by the final amplifier. Pinhole energy‐transmission measurements using a short‐focal‐length parabolic mirror determined that the focal‐spot diameter was 2.7 times the diffraction‐limited diameter.