Development of a novel gamma-ray detection system for decay data measurement and beta-delayed spectroscopy of primary fission fragments at N~82.

Abstract

The work presented in this thesis details three aspects of determining absolute properties of nuclear decay data. The first facet is the design and commissioning of the NAtional Nuclear Array (NANA) for the use of primary standardisation of gamma-cascade emitting nuclides, and to be used more widely as a gamma-ray coincidence spectrometer. Geant4 Monte Carlo simulations were created to characterise possible designs, which were subsequently validated by comparing the response of the constructed array with the model. The simulation was also used to provide correction factors for the absolute standardisation of 60Co. The second strand concerns the determination of absolute emission probabilities of several gamma rays of the medically relevant radioisotope 153Gd. Measurements of these values were made using highly characterised HPGe detectors at the National Physical Laboratory. The absolute gamma-ray emission probability of the 97.4~keV transition was found to be 30.15 (3) %, providing a new standard and correcting a possible discrepancy within the nuclear data of 153Gd reported by the Bureau Interntionale de Poids et Measures (BIPM) international reference system (SIR). The final branch of the thesis presents analyses of beta minus decays of neutron-rich primary fission products created at the RIKEN Research Institute, Tokyo Japan. Absolute beta-delayed gamma-ray emission probabilities and related limits of the beta-delayed neutron emission probabilities have been deduced for 120-124Rh decays to Palladium isotopes and astrophysically important N=82 isotone, 129Ag to states in 128,129Cd. Preliminary beta-delayed level schemes are presented for the daughter nuclei 120,122,124Pd as well as for the N=81, neutron-hole nucleus 129Cd.