Release of 37K from catcher foils

The release fraction of implanted 12 keV 37K (T1/2=1.23 s) ions from a variety of catcher foils was measured. The temperature dependence was measured for V, Fe, Ni, Y, Zr, Nb, Mo, Hf, Ta, W, Re, C, and Pt foils. The release fraction was found empirically to be a reasonably universal function of the ratio of temperature to catcher melting point. Limits on diffusion parameters (ignoring desorption) and on desorption (ignoring diffusion) were deduced. The results were used to find the optimal neutralizing catcher foil to load a neutral atom trap, and can be used to help choose ISOL target production materials.