Development of an Active Detector for the Characterization of the Late-Time Radiation Environment from a Reactor Pulse^*

This paper discusses the use of a commercially available ²³⁵U fission chamber, with a matching compensating ion chamber, originally sold as a single-ended detector with the signal conducted over the shield of a coaxial cable. The authors designed an aluminum housing that isolates the two detectors and converts the signals to full differential mode as a noise-reduction technique. The signals are processed using the switched resistor technique to extend the signal range to longer times from the peak of the pulse [Luker, S. M., Griffin, P. J., King, D. B., and Suo-Anttila, A. J., “Improved Diagnostics for Analysis of a Reactor Pulse Radiation Environment,” 13th International Symposium on Reactor Dosimetry, Akersloot, Netherlands, May 25, 2008, pp. 4–6.]. The newly configured fission chamber assembly has been used at the annular core research reactor at Sandia National Laboratories to provide a high-fidelity characterization of the neutron time profile from a pulsed operation.