Photoneutron source based on a compact 10 MeV betatron

Accelerator-based photoneutron sources have enjoyed wide use and offer the advantages of long term stability, ease of control and absence of radioacti ve materials. We report here measurements of the yield of photoneutrons fro m a neutron generator using a compact betatron. Electrons were accelerated to energies up to 10 MeV and produced a bremsstrahlung beam with a dose rat e of 0.16 Gy/min (at 10 MeV, 1 m from the bremsstrahlung target) to irradia te LiD, Be, depleted U, and Pb neutron-producing targets. The angular distr ibutions of photoneutrons produced by bremsstrahlung beams were measured wi th a "long" counter and integrated to determine neutron yield. In addition, neutron time of flight spectra were recorded from all targets using a 15.5 m flight path perpendicular to the photon beam. The maximum observed yield s were 4.6 x 10(7) n/s obtained with 1 kg of LID, 5.7 x 10(7) n/s from a 3. 3 kg Be block, 6.2 x 10(6) n/s from 1.5 kg of depleted U, and 7.0 x 10(6) n /s from 10.7 kg of Pb. Optimization of target dimensions, shape, and positi oning is expected to increase the yield from the LiD target by a factor of 35, while optimization of the other targets is expected to yield at most a factor of 10. With the increased yield and a deuteride target, this compact betatron-based system could find application in the interrogation of waste containers for fissile material. (C) 1999 Published by Elsevier Science B. V. All rights reserved.