We present measurements of window energy loss and pulse height defect in a silicon surface barrier detector for nuclei of hydrogen, helium, nitrogen, neon, and argon at incident energies of ≲ 15 to ≳ 200 keV. The values ofdE/dxin the gold window were low by [inverted lazy s] 20% for neon and [inverted lazy s] 40% for argon, and high by [inverted lazy s] 30% for nitrogen and [inverted lazy s] 50% for helium, compared to previously calculated energy loss curves extrapolated to these low energies. The pulse height defect energy losses were within [inverted lazy s] 10% for neon, low by [inverted lazy s] 15% for argon and low by [inverted lazy s] 30% for nitrogen compared to theoretical calculations.