Abstract:
A new method to eliminate beam-uncorrelated background in
photonuclear experiments has been developed at the High
Intensity Gamma-Ray Source (HIgS). Background suppression of
over 3 orders-of-magnitude has been achieved by using a gain
modulation technique to generate giant high-peakpower (GHPP)
pulses in the OK-4/ Duke storage ring FEL. The time
structure of these laser pulses was tuned so that their
duration was B100 ms; repeated every 50 ms: The associated
FEL photons were backscattered from 780 MeV electrons to
produce linearly polarized 40 MeV g-rays having the same
time structure as the FEL pulses. As an initial test of the
technique, a nearly background-free measurement of the
analyzing power in the Compton scattering reaction 16Oð~g;
gÞ16O was performed. r 2003 Elsevier B.V. All rights reserved.
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