High-energy response of the PRESCILA and WENDI-II neutron rem meters

Abstract

WENDI-II was designed at the Los Alamos National Laboratory (LANL) specifically as a wide-range rem meter, suitable for applications at particle accelerators, with response extension to 5 GeV. PRESCILA was also designed at LANL, mainly as a lightweight alternative to traditional rem meters, but has shown excellent response characteristics above 20 MeV. This Note summarises measurements performed over a span of 4 y to characterise the high-energy neutron response (>20 MeV) of these meters to several hundred million electron volts. High-energy quasi-monoenergetic beams utilised as part of this study were produced by the cyclotron facilities at the Université Catholique de Louvain (33 and 60 MeV) and the T. Svedberg Laboratory ( 46, 95, 143 and 173 MeV). In addition, measurements were also conducted at the Los Alamos Neutron Science Center, 800 MeV spallation neutron source, in broad energy fields with an average energy of 345 MeV. For the sake of completeness, data collected between 2.5 and 19 MeV in monoenergetic neutron fields at the German Physikalisch-Technische Bundesanstalt (PTB) facility are also included in this study.

Characterization of Radiation Instruments at the Summit of Mt. Fuji

“…The threshold for n/g discrimination was set as a default value; the negligibly low sensitivities to g-rays were confirmed for both monitors using 60 Co and 137 Cs source g-rays. The detail dosimetric properties of NCN1 and WENDI-II are introduced by Nakane et al (2004), Olsher et al (2000), and Olsher and McLean (2008), respectively. These two monitors were tested to measurements onboard a business jet aircraft near Japan (Yasuda et al, 2009).…”

Ambient dose equivalent measurements in secondary radiation fields at proton therapy facility CCB IFJ PAN in Krakow using recombination chambers

“…Below 0.1 and over 100 MeV, the instrument overestimates the H*(10) value. Important for this work is the fact that in the neutron energy range from 10 to 100 MeV, there is underestimation, with minimum value of about 0.5 in the range from about 15 to about 40 MeV [29,30]. Monte Carlo simulations of the proton therapy facility [31] have shown that about 70% of total H*(10) value is due to neutrons of energy from the range between 10 and 30 MeV.…”

“…Tungsten or tungsten carbide (WC) powder is added to a polyethylene moderator for the purpose of generating spallation neutrons in tungsten nuclei and thus enhance the high-energy response of the meter beyond 8 MeV. Tungsten's absorption resonance structure below several keV was also found to be useful in contouring the meter's response function [29,30]. NM2B is a moderated BF 3 proportional counter, whose response is considered acceptable for neutron energies between thermal limits and ~10 MeV.…”

Instrument intercomparison in the pulsed neutron fields at the CERN HiRadMat facility

“…It consists of a 3 He proportional counter surrounded by a cylindrical polyethylene moderator assembly and a layer of tungsten powder. This additional layer of high-Z material enhances the detector response to high-energy neutrons via inelastic scattering interactions [13,14]. The geometry of the detector is shown in Figure 7.…”