Time-resolved measurements of desorbed gas during 1-MeVK+pulsed beam deposition in a stainless steel target

Measurements were made of the density, species, and velocity of the desorbed gas cloud on intense ${\mathrm{K}}^{+}$ beam bombardment of a stainless steel target. Residual gas analyzer measurements indicate that the gas cloud consists of predominantly ${\mathrm{H}}_{2}$. Energy analyzer measurements of doubly ionized beam ions show that the ratio of hydrogen gas production to beam density was approximately $3000\text{ }\text{ }\mathrm{\text{molecules}}/\mathrm{\text{ion}}$ at normal incidence. Optical measurements of the evolution of the gas cloud during the beam pulse show a distribution with an average expansion velocity of about $0.5\text{ }\text{ }\mathrm{mm}/\ensuremath{\mu}\mathrm{s}$. Comparison is made with a simple model of the gas cloud behavior.