Experimental results concerning to the effects of the initial position of the projectile on the conversion efficiency of a reluctance accelerator

A single stage reluctance accelerator, was designed and built as a proof of concept of this kind of electromagnetic launcher. An experimental setup was designed for this launcher, consisting in doing a series of firings varying, for each one of them, the initial position of a ferromagnetic projectile - a tubular section of steel - inside its drive coil at different values of initial voltage in its capacitor bank (i.e. its electrical energy initially stored): 60 V, 75 V, 100 V, 125 V, and 150 V. For each firing the estimated exit speed of the projectile, obtained via an optical sensor consisting in a par IR LED/Phototransistor, was recorded in order to estimate the conversion efficiency, n, of the launcher. This paper describes the effects of the variation of the initial position of the projectile inside the drive coil, on the conversion efficiency of a reluctance accelerator observed in this experimental setup. Also, possible causes of such effects are discussed.