In most of its excited quantum states the atomic nucleus is a small magnet with a dipole field like that of the Earth. Because this nuclear magnetism is determined by the flow of charge and distribution of intrinsic spins within the nucleus, measurements of magnetic dipole moments give important insights into the internal structure of the nucleus.
This project focuses on nuclei in the sd shell. These nuclei, with proton and neutron numbers between 8 and 20, have been the subject of the most complete shell model studies to date. The figure shows experimental data for the gyromagnetic ratios of the first excited states in the N=Z nuclei in the sd shell. These are 20Ne, 24Mg, 28Si, 32S and 36Ar. Published results are shown as filled circles whereas the new precise result for 24Mg is the open circle. (This measurement, which represents a breakthrough in experimental precision, used a novel technique devised at ANU and was performed by an international team in Orsay, France.)
For many years it was thought that these gyromagnetic ratios should all be very close to 0.5, however recent calculations, shown as the solid line, predict a value about 10% larger. Only the new measurement on 24Mg has the precision to test these predictions. This project aims to perform similarly precise measurements on 28Si and 32S, and related isotopes, using the Heavy Ion Accelerator, and hence comprehensively test the shell model.
Students will gain experience working with radiation detectors, electronics, data acquisition, accelerator operations, and data analysis skills.