The mass of 22^Mg and a concept for a novel laser ion source trap

Abstract

Clean and high-quality radioactive ion beams can be prepared by combining ion trap and resonance laser ionization techniques. A feasibility study for such a laser ion source trap has been carried out which shows enormous improvement in the beam emittance, purity, and in addition allows for a variation of the ion beam time structure. Direct high-precision mass measurements around mass number A=22 are of utmost importance. First, the masses of the superallowed beta-emitter 22^Mg and its daughter 22^Na are needed to test the conserved-vector-current(CVC) hypothesis and the Cabibbo-Kobayashi-Maskawa(CKM) matrix unitarity, both being predictions of the Standard Model. Second, to calculate the reaction rate of 21^Na(p,gamma)22^Mg the involved masses are required very accurately. This rate is needed in order to extract an upper limit on the amount of a characteristic gamma-radiation emitted from classical nova bursts which has been searched for but not yet detected. At the triple trap mass spectrometer ISOLTRAP at ISOLDE/CERN, the masses of 21^Na, 22^Na, and 22^Mg have been measured with relative uncertainties of better than 1.5*10^{-8}. This solved a conflict between two available mass values for 22^Mg. The mass measurements as well as their impact are discussed. In addition a vivid description of the present ISOLTRAP setup along with the standard experimental procedure is described. Special emphasis has been made on the development of a carbon cluster ion source for absolute mass measurements at ISOLTRAP.