D.J. Morrissey

Pulsed extraction of ionization from helium buffer gas

The migration of intense ionization created in helium buffer gas under the influence of applied electric fields is considered. First the chemical evolution of the ionization created by fast heavy-ion beams is described. Straight forward estimates of the lifetimes for charge exchange indicate a clear suppression of charge exchange during ion migration in low pressure helium. Then self-consistent calculations of the migration of the ions in the electric field of a gas-filled cell at the National Superconducting Cyclotron Laboratory (NSCL) using a particle-in-cell computer code are presented. The results of the calculations are compared to measurements of the extracted ion current caused by beam pulses injected into the NSCL gas cell.

High precision Penning trap mass spectrometry of rare isotopes produced by projectile fragmentation

The Low Energy Beam and Ion Trap (LEBIT) is the only present facility to combine high precision Penning trap mass spectrometry with fast beam projectile fragmentation. Located at the National Superconducting Cyclotron Laboratory (NSCL), LEBIT is able to measure radionuclides produced in a chemically independent process with minimal decay losses. Recent exotic mass measurements include 66As, 63-66Fe, and 32Si. 66As is a new candidate to test the Conserved Vector Current (CVC) hypothesis. The masses of the neutron-rich iron isotopes provide additional information about the mass surface and the subshell closure at N = 40. 32Si is a member of the A = 32, T = 2 quintet; its measurement permits the most stringent test of the validity of the isobaric multiplet mass equation (IMME). An overview of some recent measurements will be presented as well as advanced techniques for ion manipulation.