Precision measurement of thermal neutron beam densities using a 3He proportional counter

Jens Aage Als-Nielsen, A. Bahnsen, W.K. Brown

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    A new method, based on the 3He(n, p)T reaction, has been developed for the accurate determination of thermal neutron beam densities. Several comparisons were made with the conventional Au-foil activation method, and agreement was obtained between the two methods within an experimental uncertainty of ±0.4%. Fundamental advantages of the method include the 1ν dependence of the 3He(n, p)T cross section up to 1 keV, and the assurance of homogeneity even for very small macroscopic cross sections, because of the gaseous detector material. Although the method requires a relatively clean neutron beam, it can be used over a wide range of neutron densities and, in particular, is capable of measuring extremely weak beams. A detector has been constructed with a well-defined efficiency and which is able to accept beams of diameters up to 10 cm. The 3He counter method is proposed as a precision standard for the absolute measurement of thermal neutron beam densities.
    Original languageEnglish
    JournalNuclear Instruments and Methods
    Volume50
    Issue number2
    Pages (from-to)181-190
    ISSN0029-554X
    Publication statusPublished - 1967

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