Identification of heavy isotope beams with multiple charge states

One of the primary challenges in performing successful inverse-kinematics measurements with heavy nuclei is the successful identification and tagging of the beam, which often contains many species. For this purpose, the Heavy Isotope Tagger (HEIST) was developed and commissioned at the National Superconducting Cyclotron Laboratory (NSCL). HEIST utilizes two micro-channel plate timing detectors to measure the time-of-flight, a multi-sampling ion chamber to measure energy loss, and a high-purity germanium detector to identify isomer decays and calibrate the isotope identification system. We discuss the simulation and performance of HEIST using a rare isotope beam centered around ¹⁹⁷Pb at about 75 MeV/A. With heavy nuclei at this energy, the beam is not fully stripped, and multiple charge states of each isotope can be present. This is one of the largest sources of contamination when trying to uniquely identify the beam. In this talk, we examine the simulation of beam production, including charge state distributions, and compare the simulation to the experimentally determined performance of HEIST. We will present the purity of typical experimental cuts on the beam PID and show how our measured charge state distributions compare to charge state models such as GLOBAL.