Modification and generalization of some methods to improve the accuracy of α-determination in the 1/E1+α epithermal neutron spectrum

Some methods described in the literature for the determination of α in the 1/E^1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements, thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods are applied in channel 15 of the Thetis reactor (Gent). Research Associate of the “Nationaal Fonds voor Wetenschappelijk Onderzoek”