Recent measurements at the CSNS towards the construction of a nMCP detector for the energy resolved neutron imaging instrument

Abstract

The energy resolved neutron imaging instrument (ERNI) will be built at the China Spallation Neutron Source (CSNS). It requires an energy resolved neutron imaging detector of a microsecond-scale timing resolution, a high spatial resolution of less than 100 μm, and a neutron detection efficiency of over 20% @ 2.9 Å. A good choice is the neutron sensitive microchannel plate (nMCP) detector. In this paper, a nMCP detector prototype was constructed based on natural Gadolinium (natGd) doped nMCP followed by a standard MCP and a single anode plate readout. We show the outcome of the proof of principle test, including the detector’s response to neutrons and gamma rays as well as detection efficiency measurements. The acquired samples of neutron and gamma signals, needed for subsequent readout electronics design, illustrate the difficulty of neutron/gamma discrimination using the natGd-doped nMCP when considering only the pulse amplitude and width. Fortunately, the use of TOF (Time Of Flight) at CSNS allows us to distinguish between neutron and gamma-induced events. The measured detection efficiencies of 35.4 ± 3.0% for 2.9 Å neutrons and 42.4 ± 3.1% for 4.8 Å neutrons are in good agreement with Geant4 simulations. The presented results confirm the nMCP detector’s feasibility for ERNI and contribute to the further development of the nMCP detector.