We report on the isotope-selective manipulation of Ca+ using the laser-heating and laser-cooling techniques in a linear Paul trap. Only 40Ca+ was selectively laser-heated using the optical isotope shift and eliminated from the trap while keeping the target isotope in the trap. The elimination process of the dominant isotope 40Ca+ was investigated and 42, 43, 44, 48Ca+ in the natural isotope mixture of Ca+ generated by laser ablation were successfully observed by means of applying the appropriate dc voltage on the end-cap electrodes without changing the laser frequencies, the laser powers and the duration of the laser irradiation. This simplified method enables us to efficiently laser-cool the rare isotopes.
This study proposes a novel alternative range-verification method for proton beam with acoustic waves generated from spherical metal markers. When proton beam is incident on metal markers, most of the resulting pressure waves are confined in the markers because of the large difference in acoustic impedance between the metal and tissue. However, acoustic waves with frequency equal to marker’s resonant frequency escape this confinement; the marker briefly acts as an acoustic transmitter. Herein, this phenomenon is exploited to measure the range of the proton beam. We test the proposed strategy in 3-D simulations, combining the dose calculations with modelling of acoustic-wave propagation. A spherical gold marker of 2.0 mm diameter was placed in water with a 60 MeV proton beam incident on it. We investigated the dependence of pressure waves on the width of beam pulse and marker position. At short beam pulse, specific high-frequency acoustic waves of 1.62 MHz originating from the marker were observed in wave simulations, whose amplitude correlated with the distance between the marker and Bragg peak. Results indicate that the Bragg peak position can be estimated by measuring the acoustic wave amplitudes from the marker, using a single detector properly designed for the resonance frequency.
We report on the dynamics of loading calcium ions into a linear Paul trap with ICP-MS. Ions are transported from the ICP-MS to the ion trap and isotopes are selectively laser-cooled, and then their laser induced fluorescence (LIF) is observed. We investigated the relationship between LIF and isotopic concentration in liquid samples and successfully obtained a calibration curve. This technique provides a novel tool for isotope analysis based on laser spectroscopy.
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