Non-Evaporative Cooling via Inelastic Collisions in an Optical Trap.

摘要

Through the use of spin-exchange collisions in a magnetic field combined with optical pumping, it is possible to cool an ultracold gas without requiring the loss of atoms. This cooling technique was implemented and characterized for 85-Rb and 87-Rb in an optical trap. Unexpected optical trap loading physics during the simultaneous loading of the two Rb isotopes and hyperfine changing collisions that were difficult to avoid without encountering problems with reabsorption of optical pumping photons presented significant challenges to effective cooling in this Rb mixture. A characterization of the cooling was conducted that provided criteria for evaluating systems suited to this cooling technique. The model of the cooling process indicates that the use of two different types of atoms in the cooling as opposed to a single type of atom should show significant benefits as the density of the gas increases. Additional measurements led to the development of an ultracold plasma apparatus that was designed to confine ultracold plasmas in a Penning trap. The ultracold plasmas produced in this apparatus had much lower density than typical systems elsewhere, and that has led to studies of ultracold plasma oscillation, response to short electric field pulses, and electron evaporative cooling (in progress).