Benchmarking a New Digital Data Acquisition System for Fast Neutron Metrology

Digital data acquisition for fast neutron metrology: defining the digital light output parameter

“…A practical solution is presented here where both anode and dynode signals are only recorded for the purpose of calibrating the integrated anode pulse, with subsequent measurements only requiring the acquisition of the anode pulse. For the AMANDE analyses [2], the integration time tL was chosen to ensure agreement between the integral of the anode and the dynode pulse height by comparing the location of the gamma-calibrated edge associated with monoenergetic neutrons. For the present n-lab measurements, this process was replicated, resulting in an optimised integration time of 1100 ns.…”

“…Figure 2 shows the scaled and calibrated light output spectra measured with the EJ-301 for 14 MeV neutrons produced by the STNG for the three scenarios. The expected lineshape for 14 MeV neutrons is taken from the IRSN response matrix used for unfolding analyses [2]. It is interesting to note that the edge of the 14 MeV lineshape matches the edge of the dynode and anode (1100 ns) light output spectra, which are observed to have slightly inferior edge resolution to the lineshape.…”

“…For each recorded event, a parameter QL was determined by integrating the digitised signal over a time approaching the full length of the pulse, typically around 500 ns. Measurements of the Compton edges of gamma rays from 137 Cs, 22 Na and AmBe radio-isotopic sources were used for scaling QL to a calibrated light output parameter L, according to the standard approach [2]. The relationship between QL and L is typically found to be linear over the energy range of the calibration sources.…”

“…Neutron metrology and spectrometry communities are beginning to adopt modern digital pulse processing systems to complement, and eventually replace, the existing analogue data acquisition systems. A new digital data acquisition system for fast neutron metrology has been benchmarked against the standard NIM-based acquisition system [2] over a range of neutron energies and field intensities at the Accelerator for Metrology and Neutron Applications in External Dosimetry (AMANDE) facility [3], IRSN Cadarache, France. The measurements of neutron fields made at AMANDE highlighted that the method implemented to obtain a calibrated light output parameter from the integrated anode output has a high sensitivity to the selection of pulse integration time [4].…”

Elemental analysis of concrete with fast neutron beams

“…A 6.0 cm thick sample of SiO2 beads (< 0.1 cm diameter) was prepared with a crosssectional area of 5.0 x 5.0 cm 2 . Neutrons (and gamma rays) were detected using a 2" x 2" EJ301 organic liquid scintillator, and data were acquired digitally [11]. The light output parameter L was taken to be the pulse height of the dynode signal after shaping and amplification and calibrated with a series of gamma ray sources.…”