C. Andreoiu

New precision mass measurements of neutron-rich calcium and potassium isotopes and three-nucleon forces

We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system, the mass of 51K was measured for the first time, and the precision of the (51,52)Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, 52Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces.

The on-line charge breeding program at TRIUMF's Ion Trap For Atomic and Nuclear Science for precision mass measurements

TRIUMFs Ion Trap for Atomic and Nuclear science (TITAN) constitutes the only high precision mass measurement setup coupled to a rare isotope facility capable of increasing the charge state of short-lived nuclides prior to the actual mass determination in a Penning trap. Recent developments around TITANs charge breeder, the electron beam ion trap, form the basis for several successful experiments on radioactive isotopes with half-lives as low as 65 ms and in charge states as high as 22+.

First Use of High Charge States for Mass Measurements of Short-lived Nuclides in a Penning Trap

Penning trap mass measurements of short-lived nuclides have been performed for the first time with highly charged ions, using the TITAN facility at TRIUMF. Compared to singly charged ions, this provides an improvement in experimental precision that scales with the charge state q. Neutron-deficient Rb isotopes have been charge bred in an electron beam ion trap to q=8-12+ prior to injection into the Penning trap. In combination with the Ramsey excitation scheme, this unique setup creating low energy, highly charged ions at a radioactive beam facility opens the door to unrivaled precision with gains of 1-2 orders of magnitude. The method is particularly suited for short-lived nuclides such as the superallowed β emitter 74Rb (T(1/2)=65  ms). The determination of its atomic mass and an improved Q(EC) value are presented.

TIGRESS: TRIUMF-ISAC gamma-ray escape-suppressed spectrometer

The TRIUMF-ISAC gamma-ray escape-suppressed spectrometer (TIGRESS) is a new γ-ray detector array being developed for use at TRIUMFs Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. TIGRESS will comprise 12 32-fold segmented clover-type HPGe detectors coupled with 20-fold segmented modular Compton suppression shields and custom digital signal processing electronics. This paper provides an overview of the TIGRESS project and progress in its development to date.

Z = 50 shell gap near 100Sn from intermediate-energy Coulomb excitations in even-mass 106-112Sn isotopes.

Rare isotope beams of neutron-deficient 106,108,110Sn from the fragmentation of 124Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0(1)(+)-->2(1)(+)) values for 108Sn and 110Sn and the results obtained for the 106Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region.

Highly charged ions in Penning traps: A new tool for resolving low-lying isomeric states

The use of highly charged ions increases the precision and resolving power, in particular for short-lived species produced at on-line radio-isotope beam facilities, achievable with Penning trap mass spectrometers. This increase in resolving power provides a new and unique access to resolving low-lying long-lived (

Trapped-ion decay spectroscopy towards the determination of ground-state components of double-beta decay matrix elements

T_{1/2} > 50

High-resolution γ-ray spectroscopy: a versatile tool for nuclear β-decay studies at TRIUMF-ISAC

ms) nuclear isomers. Recently, the

Nuclear and in-source laser spectroscopy with the ISAC yield station

111.19(22)

Charge breeding rare isotopes for high precision mass measurements: challenges and opportunities

keV (determined from