Radiative neutron capture as a counting technique at pulsed spallation neutron sources: a review of current progress

Abstract

Neutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed.Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007.In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources.

Double-GEM based thermal neutron detector prototype

“…1.1, were evaluated from direct integration of the average dE/dx plot generated through SRIM [33]. It is also necessary to consider the energy threshold, which was done by finding 𝜏 for which the average remaining energy for the given particle is equal to the threshold used in the experiment, of 100 (10) keV. This process is shown in Fig.…”

“…Beyond its historical tradition, it presents several advantages, such as the large neutron capture cross-section (𝜎 = 5325 b for 25 meV [5]), low sensitivity to gamma-rays, and the possibility of working on a wide neutron energy range in the low energy region [1]. However, due to a shortage of this gas since the early 2000s [6], the scientific community keeps searching for alternative solutions with 3 He-free detectors [7], employing 113 Cd , 157 Gd , 10 B, and 6 Li [8][9][10][11][12] as neutron converters. Nevertheless, substituting 3 He has the price of reducing the neutron detection efficiency or increasing the detection complexity.…”

“…1.1, are a critical factor in detector's design. Since 10 B has a relatively large neutron capture cross section of 3870 b for 25 meV [5] and about 19 % natural abundance [23], one of its compounds, 10 B 4 C, is particularly interesting for our purposes, given that it also presents good wear resistance besides chemical and thermal stability [24]. n + 10 B −→ This prototype can be easily assembled and offers the possibility to cover large areas, an essential requirement for some applications.…”

Optimization of detection strategies for epithermal neutron spectroscopy using photon-sensitive detectors

“…Full details of the detection setup are given in Ref. 37. The spectra were recorded using the TOF technique, 1 whereby the neutron energy transfer is inferred from the time a neutron takes to travel from the source to the detector and, in order to get rid of the large photon background at pulsed neutron sources, 38,39 the Foil Cycling Technique (FCT) 25,40 was exploited.…”

Double-GEM based thermal neutron detector prototype

“…Beyond its historical tradition, it presents several advantages, such as the large neutron capture cross-section (𝜎 = 5325 b for 25 meV [5]), low sensitivity to gamma-rays, and the possibility of working on a wide neutron energy range within the low energy region [1]. However, due to a shortage of this gas since the early 2000s [6], the scientific community keeps searching for alternative solutions with 3 He-free detectors [7], employing 113 Cd, 157 Gd, 10 B, and 6 Li [8][9][10][11][12] as neutron converters. Nevertheless, substituting 3 He has the drawback of reducing the neutron detection efficiency or increasing the detection complexity.…”