The lifetimes of excited quantum states in the atomic nucleus give extremely important information about nuclear structure and the shape of the nucleus. One of the most accurate ways to measure nuclear lifetimes is by direct timing, i.e. by observing the time between the population of a nuclear state and its decay. Some students who do the 3rd year nuclear physics labs will have performed such measurements using a pair of barium fluoride detectors, as illustrated in the figure.
A new scintillator material, lanthanum bromide, LaBr3, is now available, which has similar time resolution to BaF2, but with much superior energy resolution. Six LaBr3 detectors have been purchased that can be installed in the key instruments for nuclear structure studies, including the Caesar Array, Solenogam, and the Hyperfine Spectrometer. They make direct timing measurements possible for nuclear levels that are up to two orders of magnitude shorter-lived than was previously possible with these instruments. The new array of LaBr3 detectors has been commissioned with conventional analog electronics and several data sets collected. Analysis procedures are being developed. An order has been placed for 500 MHz Pixie-16 PXI digital processors, which will replace the analog electronics by sophisticated digital signal processing.
The outcome of the project will be the commissioning of the array of LaBr3 detectors. The new equipment will give a much enhanced nuclear lifetime measurement capability for nuclear structure studies. Students will gain accelerator-based laboratory experience and develop skills in building scientific instruments, digital data acquisition and data analysis.