Development of the BAND-GEM detector solution for SANS experiments

New high count rate detectors are needed for future spallation neutron sources where large areas and high efficiency (>50%) detectors are envisaged. In this framework, GEM is one of the explored detector technologies since they feature good spatial resolution (<0.5 cm) and timing properties, have excellent rate capability (MHz/mm2) and can cover large areas (some m2) at low cost. In the BAND-GEM (Boron Array Neutron Detector) approach a 3D geometry for the neutron converter cathode was developed that is expected to provide an efficiency > 20% in the wavelength range of interest for SANS instruments. A system of thin lamellas (250 μm) of dielectric material coated with 1 μm layer of $^{10}$B$_{4}$C has been built and positioned in the first detector gap, orthogonally to the cathode. By tilting the lamellas system with respect to the beam, there is a significant increase of effective thickness of the borated material crossed by the neutrons. As a consequence, both interaction probability and detection efficiency are increased. This paper presents the results of the performance of the first prototype of BAND-GEM detector in terms of efficiency (as a function of tilting angle).