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Measurements were made of the density, species, and velocity of the desorbed gas cloud on intense K^{+} beam bombardment of a stainless steel target. Residual gas analyzer measurements indicate that the gas cloud consists of predominantly H_{2}. Energy analyzer measurements of doubly ionized beam ions show that the ratio of hydrogen gas production to beam density was approximately 3000 molecules/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 mm/μs. Comparison is made with a simple model of the gas cloud behavior.