Flux normalization for d-T sources

We have developed a technique for measuring the source strength of d-T neutron generators used in well logging. The ¹⁶O(n,p)¹⁶N reaction was chosen to monitor the 14-MeV flux because of the high (11-MeV) threshold for this reaction. An oxygen containing scintillator, cerium-activated yttrium orthosilicate, is used as both oxygen target and detector for the decay products of ¹⁶N. The detector is gated on between accelerator pulses to reduce interference with the seven-second half-life signal from ¹⁶ N. Only those events which deposit greater than 7.7 MeV in the scintillator are counted, to reduce interference from external oxygen background reactions and from backgrounds arising from thermal neutron capture in the steel casing pipe. Gain stabilization is achieved by observing the double-escape peak from an external gamma source. The cerium-activated scintillator performs well at the elevated temperatures found downhole