Improvement of the CISAS high-shot-frequency light-gas gun

A preliminary version of Two Stage Light Gas Gun for impact testing directly derived from fusion pellet injectors was built in the CISAS laboratories few years ago. The main purpose of that system was to have a starting point to develop a new unit expressly dedicated to hypervelocity impacts. The system has started its development phase in the late '97 and it was fully operative in the late '99. In that configuration, it was able to accelerate 200 mg at 3.5km/s and 100 mg at 4 km/s with a shot frequency between 20-30 shot per day. The system at, that point was reliable but the performances were not good enough for impact testing. A great computational and experimental work started at that point to improve the gun performances. The main subsystems of the gun have been completely revised. Extensive numerical simulations have been used to optimise the first stage, the head and the damping system. Leaving almost unaltered the main geometric parameters of the original gun, an almost new unit has been developed, building a new first stage valve, a new damping system, and a new gun head. The new system has then been tested and experimentally characterised and optimised. In its new configuration, the gun is able to accelerate 100 mg at 5.5 km/s with a shot frequency of (at least) 10 shots per day; some tests show also that a speed up to 6 km/s with the same shot frequency is reachable. In this paper, the basic gun configuration and the improvement of each part are discussed. (C) 2003 Elsevier Ltd. All rights reserved.