ABSTRACT
We developed neutron detectors for detecting thermal and fast neutrons. The sensing element of the neutron detector uses a high-purity chemical-vapor-deposited (CVD) diamond plate, with a size of 3â¯mmâ¯×â¯3â¯mmâ¯×â¯0.5â¯mm, and the ø5 mm detector is sealed for use in the reactor as a small tube by using laser micro welding. The electrodes of the fast and thermal neutron detectors are made up of Ag and Gd with approximately 100-nm and 5⯵m thicknesses, respectively. The deposition method of the electrode uses the RF plasma sputtering system. The developed neutron detectors were tested on a 30-MeV cyclotron, which generates fast neutrons and gamma rays. High-density polyethylene plates, Cd plates, and Pb bricks were used for the moderator and shielding. The Ag electrode detector measured the current generated by fast neutrons and gamma rays. Although the sensitivity of the Gd electrode detector is smaller than that of the Ag electrode detector, it measured the current generated by thermal neutrons as well as fast neutrons and gamma rays.
ABSTRACT
We have developed a processing circuit for overlapped pulse signals. The overlapped pulse signals are generated when the pulse signals of a He-3 detector, by using a neutron coincidence counter, are connected to shift register coincidence electronics by an OR gate device. The developed circuit detects the overlapped pulse signals from among four input signals and produces new 50 ns pulse wide signals. We considered a case where two pulse signals are simultaneously overlapped among four signals. This circuit was tested with an ACP safeguards neutron counter (ASNC) for an advanced spent fuel conditioning process (ACP) and a (252)Cf neutron source at high rates. The loss rate of the output signal was reduced by 1.27% for singles and 4.75% for doubles when compared with the OR gate device. Also the variation for the triples was much bigger.
