Investigation of ion dynamics in a Penning trap using a pulse-probe technique

We demonstrate a pulse-probe method for measuring the ion-cloud rotation frequency in a Penning trap. We show that it is useful over a range of parameters not accessible to the photon correlation method of Dholakia et al. [1]. In particular, the pulse-probe method works for larger clouds than the photon-correlation method. We show that the pulse-probe method measures the space-charge-shifted frequency and gives us the optical pumping times within clouds. Furthermore, we show that, for Mg⁺ ions, it is capable of measuring much higher degrees of space-charge shift than the photon-correlation method. Improvements to the method may enable its use in measuring diffusion rates for ions in clouds.