Directional fast neutron detection using a time projection chamber and plastic scintillation detectors

Abstract

A new method for directional fast neutron detection is proposed based on a neutron time projection chamber (TPC) and position-sensitive plastic scintillation detectors. The detection system can efficiently locate the approximate location of a hot spot with 4π field-of-view using only the neutron TPC. Then, the system generates a high-resolution image of the hot spot using selected coincidence events in the TPC and the scintillation detectors. A prototype was built and tested using a 252 Cf source. An efficiency of 7.1×10 -3 was achieved for fast searching. The angular resolution was 7.8° (full width at half maximum, FWHM) for high-resolution imaging using the simple back projection method.

Performance study of a directional fast neutron detection system based on TPC and plastic scintillation detectors

“…The angular resolution of the image is 7.8° (FWHM). The efficiency is calculated to be 2.2×10 -5 [9], which is in good agreement with the results calculated from the cross-sections (efficiency is between 2.93×10 -5 and 1.94×10 -5 for E scin (th) between 100 and 500 keV when E TPC (th) is 1 MeV (refer Figure 17)). For the elastic scattering between a fast neutron and a proton, the distribution of the recoil angle 𝛼 is proportional to sin 2𝛼.…”

“…The first imaging results were presented in a previous report [9]. The prototype system achieved an angular resolution of 91° (FWHM) and an efficiency of 7.1×10 -3 using single scatter events in the TPC, which allowed for fast imaging of the hot spot with a 4π FOV.…”

“…Each channel is sampled by a 25 MHz FADC. The simulation results show that the angular resolution of the system worsens with a pad size of more than 4×4 mm 2 [9]. To reduce the number of electronic channels, 4×4 mm 2 is chosen as the readout pad size.…”

“…The direction of the incident neutron can be restricted to a conical surface to improve the angular resolution. We proposed a method to improve the angular resolution of the neutron TPC by adding several plastic scintillation detectors and using the coincidence events [9] (figure 2). Besides fast imaging of the hot spots with a 4π FOV using single scatter events in the TPC, the detector system can also provide high-resolution imaging using double scatter events: first in the TPC and subsequently in the scintillation detector.…”