Cooling methods in ion traps

Abstract

In many experiments utilizing ion traps, the ions must be cooled in order to increase the precision and accuracy of the measurements. Laser cooling is very effective when it can be applied, but it can only be used with a few kinds of ions, since it depends critically on the details of the electronic level structure. Other methods, such as resistive cooling, active-feedback cooling, collisional cooling, radiofrequency side-band cooling, or sympathetic laser cooling, can be applied to many kinds of ions. Progress in cooling of trapped ions has made possible improved measurements of mass ratios and atomic spectra and the observation of new phenomena, such as the formation of ordered Coulomb "crystals" of ions.