Correcting beam monitor and diffraction data for chopped delayed neutron backgrounds.

摘要

Delayed neutron choppers in pulsed source neutron beams serve to reduce the background caused by delayed neutrons in pulsed source instruments. The authors analyze the effect of a drum chopper placed in an incident pulsed beam which contains delayed neutrons and compute its influence on the detector counting rate. Expressions are found for the time and wavelength dependence of the counting rates for both prompt and delayed neutrons, in both monitor and scattered neutron detectors. On the basis of these results, they suggest an exact, random-phasing method for determining the delayed neutron background for use in measuring the delayed neutron counting rate, and propose a rapidly convergent iterative scheme for computing the correction from normally measured data. They report measurements which confirm the analysis. 5 refs., 7 figs.