Multi-Grid detector for neutron spectroscopy: results obtained on time-of-flight spectrometer CNCS

Abstract

A : The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of 3 He detectors on an operational instrument. The demonstrator has an active area of 0.2 m 2 . It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering data in parallel to the He-3 detectors of CNCS. In this paper, we present a comprehensive analysis of this data, in particular on instrument energy resolution, rate capability, background and relative efficiency. Stability, gamma-ray and fast neutron sensitivity have also been investigated. The effect of scattering in the detector components has been measured and provides input to comparison for Monte Carlo simulations. All data is presented in comparison to that measured by the 3 He detectors simultaneously, showing that all features recorded by one detector are also recorded by the other. The energy resolution matches closely. We find that the Multi-Grid is able to match the data collected by 3 He, and see an indication of a considerable advantage in the count rate capability. Based on these results, we are confident that the Multi-Grid detector will be capable of producing high quality scientific data on chopper spectrometers utilising the unprecedented neutron flux of the ESS.

Fast neutron sensitivity for 3He detectors and comparison with Boron-10 based neutron detectors

“…A promising technique is based on solid converter layers ( 10 B, Gd) and either gas proportional counter or solid state material as the sensing medium. Some examples that employ 10 B are: the Multi-Grid [13][14][15][16], the Multi-Blade [17][18][19], the Jalousie detector [20], BandGEM [21,22], the Boron-coated straw-tubes [23] and CASCADE [24]. Other technologies are based on Gd, e.g., the Gd-GEM [25,26], and a whole branch dedicated to the development of solid state neutron detectors coupled with Gadolinium as a converter layer [27][28][29][30].…”

Performance study of the Jalousie detector baseline design for the ESS thermal powder diffractometer HEIMDAL through GEANT4 simulations

“…In view of the projected need for the new instruments at the future European Spallation Source and planned upgrades of the existing neutron scattering facilities, several research labs and private companies worldwide devoted resources to develop alternatives for large-area detectors [32,33]. The potential of the boron thin film gaseous detector, one of the oldest technology used to detect thermal and cold neutrons, was immediately recognised and now, almost a decade later, gas detectors with solid 10 B 4 C converter layers are being considered for deployment in over half of the initial instruments at ESS [34,35].…”

Performance evaluation of the Boron Coated Straws detector with Geant4

“…As previously said, the latter results from the convolution of the conversion efficiency and the DCR. The conversion efficiency could be increased by using a thicker conversion layer but that would lower the escape probability of the conversion products and consequently the DCR [5,6,40]. The cumulative effect of the converter layer thickness is wavelength dependent and not straightforward.…”

“…For many years 3 He-based detectors have been dominant in the field of neutron scattering science, as they satisfied scientific requirements and 3 He was available in sufficient quantities at an affordable price. The situation has changed in recent years due to the worldwide 3 He crisis [1,2] that necessitated the development of alternative neutron detector technologies based on 10 B 4 C [3,4,5,6,7,8,9], 6 LiF [10,11,12] and scintillators [13,14,15,16,17,18,19,20].…”