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Register a new userA Compact High-Energy Neutron Spectrometer
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Added by
Volker Dangendorf Dr
Publication date
2007
fields
Physics
and research's language is
English
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A compact liquid organic neutron spectrometer (CLONS) based on a single NE213 liquid scintillator (5 cm diam. x 5 cm) is described. The spectrometer is designed to measure neutron fluence spectra over the energy range 2-200 MeV and is suitable for use in neutron fields having any type of time structure. Neutron fluence spectra are obtained from measurements of two-parameter distributions (counts versus pulse height and pulse shape) using the Bayesian unfolding code MAXED. Calibration and test measurements made using a pulsed neutron beam with a continuous energy spectrum are described and the application of the spectrometer to radiation dose measurements is discussed.
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We present the development of a segmented fast neutron spectrometer (FaNS-2) based upon plastic scintillator and $^3$He proportional counters. It was designed to measure both the flux and spectrum of fast neutrons in the energy range of few MeV to 1 GeV. FaNS-2 utilizes capture-gated spectroscopy to identify neutron events and reject backgrounds. Neutrons deposit energy in the plastic scintillator before capturing on a $^3$He nucleus in the proportional counters. Segmentation improves neutron energy reconstruction while the large volume of scintillator increases sensitivity to low neutron fluxes. A main goal of its design is to study comparatively low neutron fluxes, such as cosmogenic neutrons at the Earths surface, in an underground environment, or from low-activity neutron sources. In this paper, we present details of its design and construction as well as its characterization with a calibrated $^{252}$Cf source and monoenergetic neutron fields of 2.5 MeV and 14 MeV. Detected monoenergetic neutron spectra are unfolded using a Singular Value Decomposition method, demonstrating a 5% energy resolution at 14 MeV. Finally, we discuss plans for measuring the surface and underground cosmogenic neutron spectra with FaNS-2.
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The concept of a small-scale, pulsed-proton accelerator based compact ultracold neutron (UCN) source is presented. The essential idea of the compact UCN source is to enclose a volume of superfluid $^{4}mathrm{He}$ converter with a supercold moderator in the vicinity of a low-radiation neutron production target from (p, n) reactions. The supercold moderator should possess an ability to produce cold neutron flux with a peak brightness near the single-phonon excitation band of the superfluid $^{4}mathrm{He}$ converter, thereby augmenting the UCN production in the compact UCN source even with very low intensity of neutron brightness. The performance of the compact UCN source is studied in terms of the UCN production and thermal load in the UCN converter. With the proposed concept of the compact UCN source, a UCN production rate of $P_{mathrm{UCN}}=80mathrm{UCN}/mathrm{cc}/mathrm{sec}$ in the UCN converter could be obtained while maintaining thermal load of on the superfluid $^{4}mathrm{He}$ and its container at a level of $22mathrm{mW}$. This study shows that the compact UCN source can produce a high enough density of UCN at a small-scale, low-energy, pulsed-proton beam facility with reduced efforts on the cooling and radiation protection.
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