The use of polyimide foils to prevent contamination from self-sputtering of 252Cf deposits in high-accuracy fission counting

It is demonstrated that a thin polyimide foil can be employed to prevent contamination from the self-sputtering of a 252Cf source under vacuum, with small energy loss of the emitted fission fragments, with very small effect on the efficiency of counting the fission fragments, and with a long lifetime of the plastic foils.