Search

High-precision mass measurements of 64,65Ge and 66,67As are presented, which were obtained with the LEBIT (Low Energy Beam Ion Trap) facility at NSCL. The rare isotopes were produced by fast beam fragmentation, slowed down with a high-pressure gas stopping cell and analyzed with LEBIT's Penning-trap mass spectrometer. Compared to previous data, the uncertainties of the masses of 67As and 66As were reduced threefold to 550 eV and five-fold to 5.7 keV, respectively. The mass measurements of 64Ge and 65Ge with respective uncertainties of 40 keV and 4 keV confirm previous LEBIT data. The mass value of the superallowed beta emitter 66As leads to a new Q E C value of 9581.5(6.1) keV. Its improvement brings 66As closer to the group of isotopes with well-known Q-values that are used to test the conserved vector current (CVC) hypothesis in searches for physics beyond the Standard Model.

A collinear laser-spectroscopy (CLS) system in the BEam COoler and LAser spectroscopy (BECOLA) facility was constructed at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The BECOLA facility will be used to advance measurements of nuclear properties of low-energy rare isotope beams generated via in-flight reactions and subsequent beam thermalization in a buffer gas. The CLS studies at BECOLA will complement laser spectroscopy studies of charge radii and nuclear moments mostly obtained so far at Isotope SeOn Line (ISOL) facilities. Commissioning tests of the CLS system have been performed using an offline ion source to produce stable-ion beams. The tests set the ground work for experiments at the future Facility for Rare Isotope Beams (FRIB) as well as experiments at the current Coupled Cyclotron Facility at NSCL.

Rare isotope beams of many elements can be difficult or impossible to obtain at ISOL facilities due to their high melting points or chemical reactivity, but they are easily produced by projectile fragmentation and in-flight separation, a technique that rapidly produces fragments lighter than the projectile in a chemistry-free manner. Until recently, such high-energy projectile fragments could not be reduced to the thermal energies necessary for precision mass measurements in Penning traps. The Low Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory (NSCL) has demonstrated that projectile fragment beams can be thermalized and measured in a high-precision Penning trap. Since 2005, over 30 isotopes have been measured with LEBIT, including several isotopes of elements which are difficult for ISOL facilities to produce, such as Fe, Co, Si, Br, and S. These measurements have contributed to our understanding of nuclear structure, nuclear astrophysics, and fundamental symmetries. Some recent highlights include the discovery of an isomeric state in 65Fe, testing the Isobaric Mass Multiplet Equation (IMME) with the A = 32, T = 2 quintet with a measurement of 32Si, probing out to the proton dripline with 70m Br, and studying the N = 28 shell closure with measurements of 40 − 44S. Results of these measurements will be discussed, along with the technical developments which made them possible.

Accelerator-based neutron sources offer many advantages, in particular tunability of the neutron beam in energy and width to match the needs of the application. Using a recently constructed neutron beam line at the 88-Inch Cyclotron at LBNL, tunable high-intensity sources of quasi-monoenergetic and broad spectrum neutrons from deuteron breakup are under development for a variety of applications.