A closed-cycle, 1kHz pulse repetition frequency, HF(DF) laser

We describe the design and performance of a closed cycle, high pulse repetition frequency HF(DF) laser. A short duration, glow discharge is formed in a 10 SF6:1 H-2(D-2) gas mixture at a total pressure of similar to 110 torr. A pair of profiled electrodes define a 15 x 0.5 x 0.5 cm(3) discharge volume through which gas flow is forced in the direction transverse to the optical axis. A centrifugal fan provides adequate gas flow to enable operation up to 3kHz repetition frequency. The fan also passes the gas through a scrubber cell in which ground state HF(DF) is eliminated from the gas stream. An automated gas make-up system replenishes the spent fuel gases removed by the scrubber. Total gas admission is regulated by monitoring the system pressure, whilst the correct fuel balance is maintained through measurement of the discharge voltage. The HF(DF) generation rate is determined to be close to 5 x 10(19) molecules per second per watt of laser output. Typical mean laser output powers of up to 3 watts can be delivered for extended periods of time. The primary limitation to life is found to be the discharge pre-ionisation system. A distributed resistance corona pre-ioniser is shown to be advantageous when compared with an alternative are array scheme.