High precision mass measurements and in trap-decay spectroscopy of rare isotopes at TITAN / TRIUMF

by Stephan Ettenauer (Harvard University (US))

Thursday 7 Mar 2013, 14:30 → 15:30 Europe/Zurich

26-1-022 (CERN)

Atomic masses of rare isotopes continue to be a fundamental ingredient for studies of nuclear structure, nuclear astrophysics, and fundamental symmetries. In the endeavor to explore the nuclear mass surface towards the limits of nuclear existence, TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN) has pioneered Penning trap mass spectrometry along two aspects: Firstly, it is uniquely capable to handle very short lived nuclides with half-lives even below 10 ms [1]. Secondly, it is pushing on the precision frontier by utilizing an electron beam ion trap to breed short-lived nuclides delivered from ISAC / TRIUMF to a higher charge state. The precision of the mass measurement in a Penning trap is thereby boosted by a factor identical to the charge state q of the ion. In combination with advanced excitation schemes such as the recently introduced Ramsey technique [3], this novel approach for rare isotopes opens the path towards gains of 1-2 orders of magnitude in experimental precision. Recently, these unique experimental capabilities at a radioactive ion beam facility allowed TITAN to make contributions in a variety of physics questions. These range from nuclear structure topics as neutron-rich Ca-isotopes as a superb testing ground for 3-body forces [4] or shell gaps in the island of inversion [5], over superallowed nuclear beta decays to determine Vud of the Cabibbo–Kobayashi–Maskawa matrix [2], to solar neutrino physics [6]. For the latter, the energy threshold (or Q-value) of 71Ga(ν,e−) 71Ge was determined accurately using ions with up to q=22+. Previously this Q-value represented a nuclear physics uncertainty relevant for the discrepancy observed in the SAGE and GALLEX neutrino calibration measurements [7]. In addition to the mass measurement program, TITAN is developing a novel method for in-trap decay spectroscopy to determine very weak electron capture branching ratios as relevant in the context of nuclear matrix elements of 2νββ- decays [8]. This talk will provide an overview over the TITAN facility and a summary of recent results. [1] M. Smith et al., Phys. Rev. Lett. 101, 202501 (2008) [2] S. Ettenauer et al., Phys. Rev. Lett. 107, 272501 (2011) [3] S. George et al., Phys. Rev. Lett. 98, 162501 (2007) [4] A. T. Gallant et al., Phys. Rev. Lett. 109, 032506 (2012) [5[ A. Chaudhuri et al., in preparation [6] D. Frekers, M.C. Simon et al., in preparation [7] C. Giunti and M. Laveder, Phys. Rev. C 83, 065504 (2011) [8] T. Brunner et al., NIM B 266, 4643 (2008)