The fission track technique for detecting235U has been used in conjunction with a mechanical time-of-flight spectrometer in order to measure the energy spectrum in the region 1 eV to 1 keV of material sputtered from a 93% enriched235U foil by 80 keV40Ar+ions. The spectrum was found to exhibit a peak in the region 2–4 eV and to decrease approximately asE–1.77forE≳ 100 eV. The design, construction and resolution of the mechanical spectrometer are discussed and comparisons are made between the data and the predictions of the random collision cascade model of sputtering.