At the Ion Trapping group at Imperial College London we use a Penning trap in order to spatially confine singly-ionised calcium-40 ions. We then use lasers to cool them to millikelvin temperatures. A Penning trap is a type of ion trap that uses static electric and magnetic fields, rather than the radio-frequency oscillating electric fields found in a Paul trap. Positive voltages are applied to two endcap electrodes which creates a harmonic potential along the axis of the trap, and a magnetic field is applied along this axis which causes the ions to orbit the centre of the trap in the plane perpendicular to it.
The magnetic field means that there is a large splitting of the electronic energy levels and we need to address many different transitions in order to create a closed laser cooling cycle.
The focus of our current research is split into two main areas: working with single ions in order to perform high-resolution spectroscopy and to achieve cooling beyond the Doppler limit, and also the control of small ion Coulomb crystals.
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