Schmidt Julian, Hönig Daniel, Weckesser Pascal, Thielemann Fabian, Schaetz Tobias, Karpa Leon
Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany.
Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University, Collège de France, 4 place Jussieu, Paris, France.
Appl Phys B. 2020;126(11):176. doi: 10.1007/s00340-020-07491-8. Epub 2020 Oct 9.
We study a method for mass-selective removal of ions from a Paul trap by parametric excitation. This can be achieved by applying an oscillating electric quadrupole field at twice the secular frequency using pairs of opposing electrodes. While excitation near the resonance with the secular frequency only leads to a linear increase of the amplitude with excitation duration, parametric excitation near results in an exponential increase of the amplitude. This enables efficient removal of ions from the trap with modest excitation voltages and narrow bandwidth, therefore, substantially reducing the disturbance of ions with other charge-to-mass ratios. We numerically study and compare the mass selectivity of the two methods. In addition, we experimentally show that the barium isotopes with 136 and 137 nucleons can be removed from small ion crystals and ejected out of the trap while keeping ions Doppler cooled, corresponding to a mass selectivity of better than . This method can be widely applied to ion trapping experiments without major modifications since it only requires modulating the potential of the ion trap.
我们研究了一种通过参数激励从保罗阱中进行质量选择性去除离子的方法。这可以通过使用成对的相对电极以两倍于回旋频率施加振荡四极电场来实现。虽然在与回旋频率共振附近的激励仅导致振幅随激励持续时间呈线性增加，但在该频率附近的参数激励会导致振幅呈指数增加。这使得能够以适度的激励电压和窄带宽有效地从阱中去除离子，从而大幅减少对其他质荷比离子的干扰。我们对这两种方法的质量选择性进行了数值研究和比较。此外，我们通过实验表明，具有136和137个核子的钡同位素可以从小离子晶体中去除并从阱中射出，同时保持离子处于多普勒冷却状态，对应的质量选择性优于 。由于该方法仅需调制离子阱的电势，无需重大修改即可广泛应用于离子捕获实验。
