Prompt γ radiation measured with a Nal scintillation detector: a beam monitor for neutron scattering instruments which needs no space in the beam
(English)
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We investigate the possibility of using the prompt γ rays emitted by aluminum windows in order to monitor the neutron flux of the beam. A Nal scintillation detector is used to detect the prompt γ rays. No additional material apart from the unavoidable Al windows along the flight path is placed in the beam. The performance of the monitor is compared to that of a standard BF3-monitor placed in the beam. Influences of a magnetic field on the photomultiplier of the Nal monitor is discussed, as well as the influence of activation gammas. At an instrument using a beam chopper the time behaviour is discussed.