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.