Absolute calibration of nuclear activation diagnostics for intense pulsed ion beams

Absolute calibration of an annihilation‐radiation NaI coincidence detection system for short‐lived ion‐induced radioactivity is described. Calibration with a 22Na radioactive source is compared with an independent calibration using the 12C(p,γ)13N(β+) reaction with 1 MeV protons from a Van de Graaff accelerator. These calibrations are consistent, provided correction for summing of the 0.51 and 1.27 MeV gamma rays from the 22Na source in the NaI detectors is included. This summing correction depends on the total efficiency for detecting 1.27 MeV gamma rays and can alter the calibration by as much as a factor of 2, depending on the size and separation of the detectors. A procedure to determine this correction using 60Co and 22Na radioactive sources is described. These two calibrations give a thick‐target yield for the 12C(p,γ)13N reaction at 1 MeV of (8.0±0.4)×10−10 reactions/proton. Intense pulsed proton fluences of 0.08 to 3.7 cal/cm2, determined by coincidence counting β+ annihilation radiation produced ...