[Triumf-seminars] TRIUMF Seminar today at 14:00

postmaster at admin.triumf.ca postmaster at admin.triumf.ca
Tue Jun 12 05:00:00 PDT 2007

Date/Time: Tue 2007-06-12 at 14:00

Location:  Auditorium          

Speaker:   Michael Block (NSCL, Michigan State University)

Title:     High-precision mass measurements of rare isotopes at LEBIT

Abstract: The combination of gas stopping with advanced ion-beam manipulation techniques allows the preparation of stopped rare-isotope beams from projectile fragmentation with high beam quality. Thus, high-precision experiments such as Penning trap mass measurements or laser spectroscopy are possible for a very large range of rare isotopes far away from stability. The Low Energy Beam and Ion Trap (LEBIT) facility at the NSCL was the first to start an experimental program with stopped rare isotopes produced by projectile fragmentation. At LEBIT mass separated rare-isotope beams with energies between 80-100 MeV/u are stopped in a gas cell. Advanced radio frequency quadrupole ion guiding and trapping techniques are used to prepare a high-quality, pulsed low-energy beam. The short bunches are then injected into a 9.4T-Penning trap mass spectrometer where the mass is determined. Since 2005, the masses of more than 30 radionuclides have been measured with relative uncertainties in the order of 10-8 [1,2,3]. For example, a high-precision mass measurement of the super-allowed beta emitter 38Ca [2] was performed making it a new candidate for tests of the conserved-vector current hypothesis. The results obtained for nuclei around N=Z=33 contribute to the study of proton-neutron pairing and the astrophysical rp process [3]. The mass uncertainty of the waiting point nuclei 64Ge and 68Se has been significantly improved and the mass of the drip line nucleus 70mBr has been determined for the first time. Furthermore, high-precision mass measurements of the neutron-rich nuclei 40-44S, 63-65Fe, and 64-66Co have been performed supporting studies of the shell structure evolution in very neutron-rich nuclei. 

Stimulants available 15 minutes before the talk.


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