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Microchannel plate (MCP) event-counting imaging detectors with very high spatial resolution (~10 µm) and timing accuracy (~100 ps) are widely employed for the detection and imaging applications of electrons and ions, as well as UV and X-ray photons.Recently it was demonstrated that the many advantages of MCPs are also applicable to neutron detection with high 2-dimensional spatial resolution. Boron, enriched in the isotope 10 B, was added to the MCP glass structure to enhance the neutron interaction within the MCP through the 10 B(n,α) 7 Li reaction. The energetic charged particle reaction products release secondary electrons directly into MCP channels, initiating an electron avalanche and a subsequent strong output pulse. In this paper we present a detailed model for calculating the quantum detection efficiency of MCP neutron detectors incorporating * Corresponding author. E-mail address: ast@ssl.berkeley.edu (A.S.Tremsin) 2 10 B, for the specific case of square channel MCP geometry. This model predicts that for thermal neutrons (0.025 eV), MCP detection efficiencies of up to 78% are possible using square channels. We also show theoretically that square channel MCPs should have a very sharp (~ 17 mrad) angular drop in sensitivity for detection of normal incidence neutrons, opening up new possibilities for angle-sensitive neutron imaging as well as collimation. The calculations can be used to optimize MCP neutron detection efficiency for a variety of applications. In a subsequent companion paper, the model will be extended to the case of hexagonally-packed circular channels.

The Cold Neutron Depth Profiling (CNDP) instrument at the NIST Cold Neutron Research Facility (CNRF) is now operational. The neutron beam originates from a 16 L D2O ice cold source and passes through a filter of 135 mm of single crystal sapphire. The neutron energy spectrum may be described by a 65 K Maxwellian distribution. The sample chamber configuration allows for remote controlled scanning of 150 × 150 mm sample areas including the varying of both sample and detector angle. The improved sensitivity over the current thermal depth profiling instrument has permitted the first nondestructive measurements of 17O profiles. This paper describes the CNDP instrument, illustrates the neutron depth profiling (NDP) technique with examples, and gives a separate bibliography of NDP publications.