Plasma mass and effective inductance in a small railgun

A series of firings of a small caliber plasma-driven electromagnetic railgun are described in which copper, aluminum and zinc foils are used to initiate the plasma. Three different masses of each type of foil are used. Projectile displacement-time profiles in the railgun bore are constructed from streak camera records and calculations based on experimental current vs time records are made to obtain effective inductance per unit length values (L'sub eff) for each firing. The effects of foil mass and species, plasma voltage and plasma leakage past the projectile are discussed in relation to the calculated L' sub eff values.