Study on measurement influence of reaction cross-section for irradiated neutron fluence in single-crystal silicon

Abstract

BackgroundWhen the activation method is used to measure the irradiated thermal neutron fluence of single-crystal silicon neutron transmutation doping, the measured value may have a certain deviation due to the difference in the curve shapes of the target reaction cross-section as a function of neutron energy between activated detector and silicon.PurposeThis study aims to suppress the measurement influence caused by reaction cross-section difference between activation detector and silicon, and to reduce the measurement deviation.MethodsBased on the Stoughton-Halperin convention relation, the binary first-order equations solution method and a linear least-squares fitting method were established. A variety of activation detectors and their combinations were applied to experimental measurement to verify their feasibility. These activation detectors were placed in the irradiation facility and irradiated in the Minjiang test reactor at Sichuan province. Finally, all of detectors were taken out from the reactor, and the radioactive activity was measured by high purity germanium γ spectrometer.ResultsThe results show that obvious differences exist in the measurement values of different activated detectors at the same position, and the measurement deviation based on suitable detector combination is greatly reduced to be less than 3% by using above two methods.ConclusionsThe two methods proposed in this study can effectively suppress the influence of the reaction cross-section difference on measurement. The equation method has certain advantages over the least-square method with only two kinds of compulsory detectors, it can also be applied to other thermal neutron irradiation samples.

Keywords

• single-crystal silicon
• neutron transmutation doping
• thermal neutron fluence
• activation method
• reaction cross-section