A study of irradiation-induced damage in HAVAR^® foils was initiated in order to extract the highest proton dose the foils can sustain. The lattice structure of HAVAR^® foils in different metallurgic conditions is presented, as well as visible internal structure, measured by Transmission Electron Microscopy (TEM). Positron Annihilation Spectroscopy (PAS) techniques were used to investigate these foils, and another foil that had been irradiated to the maximal proton dose limit, set by the manufacturer to a total charge of 1 mAh (= 3.6 C). PAS techniques included Doppler broadening (DB) measurement in the SPONSOR beam and lifetime (LT) measurements, both carried at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Both positron spectroscopy methods show clear differences between the investigated foils, with distinguished characteristics for annealed, cold-rolled and irradiated foils. The advantages of using a slow positron beam to study thin foils and defect profiles, over a table-top LT spectrometer, are discussed and demonstrated by the HAVAR^® measurements.