In-Core Neutron Detection System Using a Dual-Mode Self-Reset Preamplifier With the Micro-Pocket Fission Detector

This article presents the development of an in-core neutron detector readout system utilizing a charge-sensitive amplifier (CSA) with a self-reset technique, alongside data loggers, to measure the output of the CSA. Micro-pocket fission detectors (MPFDs) were developed as in-vessel neutron detectors having many advantages in terms of portability size, reproducibility of charge deposition, usability in high neutron flux, and capability of gamma-ray discrimination. The proposed readout system for MPFDs can be operated in a dual mode which consists of integration and single event modes. The integration mode can count the number of saturated preamplifier outputs in a high-radiation environment. On the other hand, the single-event mode can directly measure the analog data induced by detectors. A novel approach to dead time compensation is also introduced using an active dead time control (ADTC) method. This article shows the reactor transient test results conducted at the transient reactor test (TREAT) reactor. The neutron flux of
$7\,\times \, 10^{15} \text {n/cm}^{2}\cdot \text {s}$
with the full-width half maximum (FWHM) of 126 ms at the reactor power of 2.1 GWth was measured. According to the reactor power of 5.1 GWth, the neutron flux and FWHM were obtained as
$1.24\,\times \, 10^{16} \text {n/cm}^{2} \cdot \text {s}$
and 136 ms, respectively.