Probing the limits of nuclear excited state lifetime measurement using fast rare isotope beam and doppler-shift attenuation method with a single active target.

Precise lifetime measurements of excited states provide valuable information for the structure of nuclei. Using Geant4 simulation software, we are able to analyze how different factors such as beam energy, beam composition, and reaction target thickness affect the sensitivity of lifetime measurements. Here, we analyze the properties of fast heavy ion beams with regard to the limits of what measurements are possible using a doppler shift attenuation method. Simulation parameters are set to a single fixed target with the Gretina γ-ray tracking HPGe array measuring decays. The effects of varying thickness of a Carbon target are explored and 1mm thickness is determined to be optimal for lifetimes in the range of 0.5ps to above 5.0ps. Furthermore, it is determined that the use of an active diamond target can allow for more precise lifetime measurements as well as greatly extend the lower bound of what lifetimes can be measured with this method down to ~0.2ps.