The Moxon-Rae setup from Karlsruhe

Moxon-Rae detectors consist of a converter, typically of carbon or bismuth, to "convert" the capture - rays into electrons by Compton scattering, pair production, or the photo effect. These electrons are either absorbed in the converter or detected in a thin plastic scintillator, which is mounted between the converter and a photomultiplier (see figure). The efficiency of such a detector increases almost linearly with - ray energy. This property results in an efficiency for neutron capture events, which is nearly proportional to the neutron binding energy and independent of the capture - ray cascade, if the probability of detecting more than one - ray out of a cascade is negligible.

Figure: Schematic scetch of the experimental setup.


In measurements with Moxon-Rae detectors, the main systematic uncertainty is due to deviations from the ideal proportionality between efficiency and - ray energy. Therefore, the slope of the efficiency curve has to be measured. With these data, a reliable efficiency correction can be derived (reference for more details).


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