Detector Seminar: 10B-based MultiGrid detectors as an alternative to 3He: achievements and construction of a large area demonstrator

Friday 23 May 2014, 14:00 → 15:30 Europe/Stockholm

Scheele (ESS Headquarter)

Speaker: Mathieu Ferraton, Detector Group, ILL Abstract: A position sensitive detector technology for thermal neutrons, based on solid 10B-enriched B4C layers as a converter, is being developed in collaboration between ILL, ESS and Linköping University. This technology called MultiGrid aims at providing a spare solution to replace 3He tubes for neutron scattering instruments requiring several tens of square meter active area. Several prototypes have been tested over the past few years, confirming the good expected performances. The last prototype, covering a 32x48 cm² sensitive area, was mounted on the IN6 instrument at ILL to carry out measurements in the conditions of a scientific experiment. This prototype has shown performances comparable to those of the 3He-based detection system of the instrument, except for an unexpected high level of background. This background was identified as originating from the natural alpha radioactivity of 238U and 232Th, present as contaminants in the standard aluminum alloy composing the mechanical structure of the detector. Reduction of the background to a level close to 3He tubes’ was achieved either by plating standard aluminum parts with a nickel layer or by using purified aluminum. Development of MultiGrid detectors has now entered the final phase which aims at demonstrating the capacity to scale-up the technology. The IN5 instrument’s detector, which active area of 30 m² is the largest at ILL, was chosen as a benchmark for the construction of a large area demonstrator. This prototype, which is currently under fabrication, will be the size of an IN5 module (1/12 of the instrument’s detector), covering a 0.8x3 m² active area, fifteen times larger than the IN6 prototype. Global performances of MultiGrid detectors will be presented, as well as design, fabrication details and status of the large area demonstrator.

Slides ESS_Seminar.pptx