PACS 29.30.Hs, 29.40.Vj, 29.40.Wk The common methods of neutron detection are reviewed with special attention paid to the application of cryogenics and semiconductors to the problem. The authors' work with LiF-and boron-based cryogenic instruments is described as well as the use of CdTe and HgI 2 for direct detection of neutrons. 1 Introduction Advances in materials and methods have enabled the detection of radiation by means today that would have seemed, to pioneers in the field a century ago, like science fiction. Improvements in technology have resulted, for gamma ray detection, in high-purity germanium operating at 77 K and providing 0.1% energy resolution above 1 MeV, more than an order of magnitude improvement over what was (and still is) achievable by scintillators. However, operating below 1 K, cryogenic calorimeters have been used in X-ray astronomy, in the search for dark matter, and more recently in gamma ray spectroscopy, and have achieved better than 70 eV resolution at 60 keV [1], a factor of 4 to 5 improvement over what can be achieved by germanium at that energy. Meanwhile, at the other end of the temperature spectrum, the development of new, wide band-gap semiconductors has sparked research in room temperature gamma ray detectors and has held out the hope of 1 -2% resolution and freedom from cryogenics [2,3].With such results being reported from the X-and gamma ray world it is natural to examine the possibilities for neutron detection. A cryogenic neutron detector would operate by detecting the heat pulses caused by neutron capture and scattering, while a semiconducting detector would detect the nuclear reaction products from a sensitizer (for example, fission fragments detected in a 235 U-coated Si diode) or from some constituent of the semiconductor.In the following sections, the common methods of neutron detection are described and their deficiencies with respect to neutron spectroscopy at energies above thermal (0.025 eV) are outlined. Published work on neutron-detecting cryogenic calorimeters will be reviewed and work by the present authors on boron-and lithium-based instruments will be discussed. Turning to semiconductors, we review work with coated and native (uncoated) semiconductor, including Cd 1-x Zn x Te (CZT) and HgI 2 , as applied to neutron detection. Results obtained by the authors with HgI 2 will be shown.

An ion microprobe mass analyzer was used to investigate the reaction pathway for the formation of lithium hydroxide and lithium oxide on freshly cleaved lithium deuteride surfaces. Mass spectra were obtained from the lithium deuteride surfaces before and after exposure to room air, and the composition of the corrosion film was determined by depthprofiling methods. The corrosion film appears to be layered in the following manner: lithium hydroxide on lithium oxide on lithium deuteride.

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