Abstract
European Spallation Source instruments like the macromolecular diffractometer (NMX) require an excellent neutron detection efficiency, high-rate capabilities, time resolution, and an unprecedented spatial resolution in the order of a few hundred micrometers over a wide angular range of the incoming neutrons. For these instruments solid converters in combination with Micro Pattern Gaseous Detectors (MPGDs) are a promising option. A GEM detector with gadolinium converter was tested on a cold neutron beam at the IFE research reactor in Norway. The μTPC analysis, proven to improve the spatial resolution in the case of 10B converters, is extended to gadolinium based detectors. For the first time, a Gd-GEM was successfully operated to detect neutrons with a measured efficiency of 11.8% at a wavelength of 2 Åand a position resolution better than 250 μm.
Highlights
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A GEM detector with gadolinium converter was tested on a cold neutron beam at the Institute for Energy Technology (IFE) research reactor in Norway
Summary
Despite the very large neutron capture cross section of 155Gd and 157Gd, the material is not a popular converter due to the nature and the energy of the secondary particles. Kinetic Energy [keV] CSDA Range [cm]a Maximum Penetration Depth [cm]b Standard Deviation [cm]c. The conversion electron track is fully contained in the drift space if its maximum penetration depth is smaller than the drift length. A CsI layer applied to the gadolinium was used as an electron emitter to localize the electron energy loss and, improve the spatial resolution [25, 26] The disadvantage in this case is the very small amount of primary electrons and deposited energy that requires a detector with very large gain. The challenge is here that in contrast to the α particles and Li ions created in the 10B4C converter, the gadolinium conversion electrons have on average a far larger range, and do not leave a straight ionization track.
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