Use of a Low Energy Proton Accelerator for Calibrating a Large NaI(Tl) Array in a High Energy Physics Experiment

We report the use of a 500 keV Van de Graaff proton accelerator to produce γ-rays in the range 4 - 18 MeV via nuclear reactions for the purpose of calibrating a large NaI(Tl) crystal array. Data analysis indicates an energy calibration to ~ 1% over this range.