Development of a ceramic double thick GEM detector for transmission measurements at the VESUVIO instrument at ISIS

Abstract

Neutron spallation sources always require new instrument upgrades and innovations in order to improve the quality of their experiments. In this framework, the capability to accurately measure total neutron cross sections at the VESUVIO instrument at the ISIS Facility can be boosted by a tailored transmission detector. For this reason, the first double ceramic thick GEM detector has been realised. Detectors based on GEM technology are broadly developed thanks to their characteristics, such as good spatial resolution (< 0.5 mm), good detection efficiency, high rate capability (MHz/mm2) and a possible coverage area of some meters at low costs. This article shows the realisation of a GEM detector made of a 10B4C cathode, two ceramic thick GEM foils and a padded anode, as well as the device characterisation on the VESUVIO beam line, where stability, γ-sensitivity, imaging capability and sample analysis have been studied. The successful results confirm that the ceramic thick GEM detector performs well in thermal and epithermal neutron detection and it will allow the scientific user community of the instrument to perform better quality transmission measurements so as to determine more accurate total neutron cross section of condensed-matter systems.

Thermal neutron cross sections of amino acids from average contributions of functional groups

“…The values of mass, thickness and integrated proton current are reported in Table I, together with the molecular stoichiometry. Time-of-flight spectra of incident neutrons not interacting with the sample were obtained using the standard GS20 6 Li-doped scintillator available at the instrument, as well as the newly installed double thick Gas Electron Multiplier (GEM) detector 48 . The latter was positioned between the sample position and the GS20 monitor, at a distance from the moderator of 12.60 m, as calibrated at the beginning of the experiment using the VESUVIO incident foil changer 29 .…”

“…In the case of the GEM detector, both S(E) and C(E) were normalized to the number of proton pulses counted by the detector electronics. However, as a slight fluctuation of the efficiency with time is known to affect the GEM detector 48 , of magnitude ca. 2% with no dependence upon the neutron energy, the resulting transmission spectra were scaled so as to overlap to the GS20 spectra for epithermal neutrons.…”

Characterisation of N2-GEM: a beam monitor based on Ar-N2 gas mixture

“…Gas detectors based on Gas Electron Multiplier (GEM) [1] technology are constantly developed for different applications, such as high energy physics [2], plasma physics [3] and matter physics [4]. GEM detectors usually work with an active flow gas containing Ar as active and CO2 as quenchig gases, but recent studies have brought to develop a new configuration of these devices, completely sealed, based on the gas recycle.…”

First evaluation of a novel ionisation chamber for thermal neutron beam monitoring

“…The multitude and complexity of the ESS beam line components, much higher than in existing neutron sources, imply a greater need for monitoring. Therefore, aside from previously characterised beam monitors [2,3,[21][22][23][24][25][26][27] based on discrete events, the concept of an ionisation chamber with a boron converter produc-ing continuous current has been suggested as a candidate for the location close to the so-called bunker, a shielding block surrounding the target monolith that hosts the extraction and primary optical transport guides and in some occasions even chopper systems [28]. At least one beam monitor per instrument is foreseen to be placed inside the bunker zone.…”