Evaluation of Timing and Pulse Shape Analysis Method for the Measurement of Photoneutron Energy Distribution Using Commercially Available Digitizer

Abstract

Photonuclear reactions triggered by high-energy photons are crucial in simulations for both nuclear physics and radiation transport. In such simulations, understanding the photonuclear reaction cross section and the energy distribution of secondary particles, particularly neutrons, is vital owing to the energy-dependent nature of neutrons. Experimental investigations have used monoenergetic, linearly polarized photons in the range of tens of MeV to measure neutron energy distributions resulting from photonuclear reactions. In an experiment, we adopted an electronic circuit and detector system based on the time-of-flight (ToF) method and particle identification to determine the energy distribution of emitted neutrons. This system required precise nanosecond-level timing and the ability to distinguish signals with millivolt-level differences. The advent of GHz sampling digitizers, field-programmable gate arrays (FPGAs), and high-speed interfaces allows these measurements to be conducted using commercially available single-board electronics. This study highlights the data acquisition (DAQ) process using a 1-GHz sampling rate, 14-bit resolution, FPGA-based real-time signal processing, and 1-MHz throughput digitizer (APV8104 by TechnoAP Company). Moreover, it provides a detailed description of the motivation behind the study, underscoring the importance of the energy spectrum. We evaluated the digitized data for their applicability and analyzed the raw data for potential improvements in timing and signal differentiation compared to those of traditional FPGA-based schemes.