Development of a small-sized apparatus for hypervelocity impact experiment in a standard-scale laboratory of one unit

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Atwo-stage light gas gun is the only launcher which can accelerate a small projectile over 3 km/s with good reproducibility. This launcher needs to be set up in a large-scale laboratory isolated from other facilities because of its safety operation and silence for environment. However a very small-sized two-stage light gas gun, so called a micro gun, could be designed as a luncher to be set up in a standard-scale laboratory of 30 m^2 in floor surface. It was successfully constructed on a base of only 2.8 min length.This gun was designed to be modified easily in sizes of its launch tube and compression tube which act effectively on projectile acceleration.The launch tube and compression one have the inner diameters of 1.58 mm and 9 mm, respectively for standard operation.One of reasons for this selection is that high-pressure tubes on the market can be used as these tubes.A magne'to-flyer method was adopted for simple and precise measurement of projectile velocity.A projectile made of ferromagnetic material needs to be prepared for this method.Thus, sphere-shaped projectiles of MnAl alloy with mass density of 5.1 g/cm^3 and diameter of 1mm were made.Each projectile was put in a sabot made of nylon as a flyer in the launch tube.Acceleration experiments were conducted with respect to some of the parameters as follows ; amount of charge, thickness of a diaphragm set between the launch tube and a high-pressure coupling, weight of a piston for light-gas compression, and weight of a projectile.Experimental results showed that this micro two-stage light gas gun can accelerate a projectile up to 5 km/s by using of safety helium gas, and that this gun was successfully developed.