Experimental measurements of hypervelocity impact plasma yield and energetics

Ion yields and their characteristic energies have been measured experimentally in the plasma produced by hypervelocity impacts of iron rrmicroparticles on rhodium in the range 1.2 to 87 km s'. The ion yield shows a greater velocity dependence than has generally been reported in the literature, though the difference is attributed to experimental and analytical effects. The higher value derived here is believed to be a better representation for the yield of plasma from the primary impact. The impact plasma is shown not to be in thermal equilibrium. Characteristic energies of the target and projectile material ions typically lie in the range 20-40 eV (also higher than values generally quoted in the literature) and show little variation with impact velocity, while contaminant ions (alkali metals and hydrogen) show significantly different trends indicating a different production mechanism.