Dose measurements of bremsstrahlung-produced neutrons from thick targets

Photons of sufficiently high energies (Eγ≥5–15 MeV) can produce neutrons by means of photonuclear interactions. Bremsstrahlung from high energy electron storage rings, which have an energy range of zero to the maximum energy of the particle beam, can interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. This paper presents the results of simultaneous measurements of bremsstrahlung power and corresponding photoneutron dose equivalent rate at the insertion device beamlines of the Advanced Photon Source, using a lead-glass calorimeter and an Andersson–Braun remmeter. Targets made of Fe, Cu, W, and Pb are placed in the bremsstrahlung beam inside the first optics enclosure of the insertion device beamlines. The photoneutron dose equivalent rates, normalized to bremsstrahlung power, beam current, and storage ring pressure, are measured for the four targets. The photoneutron dose equivalent rates, normalized to the bremsstrahlung power and corrected for systematic variations, are given as 2.2±0.5 rem/h/W for Fe,3.0±0.5 rem/h/W for Cu, 3.8±0.5 rem/h/W for W, and 3.7±0.8 rem/h/W for Pb targets, at a distance of 0.8 m perpendicular from the target center.