Temperature measurement of ~6He~+ ions confined in a transparent Paul trap

摘要

The LPCTrap setup is a transparent Paul trap dedicated to the measurement of the β–ν correlation coefficient aβν in the β decay of trapped radioactive nuclides. In a first experiment, the system has been used to record ～10~5 coincidences between the β particles and recoiling ions emitted from the decay of ~6He~+ ions. The analysis of the collected data has already shown that the size of the ~6He~+ ion cloud confined in the Paul trap is a critical parameter, potentially limiting the accuracy on the aβν measurement. We report here the precise determination of the trapped ion cloud temperature and size. This was performed by extracting the trapped ions toward a position sensitive micro channel plate detector at different phases of the RF driving field. We find a temperature Texp = 0.107(7) eV, consistent with the temperature values inferred using two other observables but 20% higher than the temperature Tsim = 0.09 eV predicted by realistic simulations of the ions interacting with the H_2 buffer gas.