Heavy, highly charged ions, including “naked” uranium (U92+), can be generated most efficiently at high energies. This involves firing an ion beam traveling at typically more than 50% of the speed of light through a thin foil, stripping off (almost) all of the electrons. Once the ions generated in this way are stored in the ESR storage ring, experiments can be carried out on them at high speeds. For many precision measurements, however, it is desirable to use these ions at the lowest possible energy, ideally at rest in an ion trap. The HITRAP facility was developed at GSI for this purpose. It is designed to slow down such heavy, highly charged ions, trap them in a Penning trap, cool them further, and finally transfer them to various experimental setups.
To this end, HITRAP is breaking new ground in several respects. The capture of highly charged ions after production at an accelerator has never been demonstrated before. Nor has the electron cooling of highly charged ions in a Penning trap.
Once these milestones have been achieved, laser spectroscopy will then be performed in the ARTEMIS Penning trap. The first candidates for this are hydrogen-like and lithium-like bismuth 209Bi80+,82+.
In addition to precision spectroscopy, the highly charged slow ions also offer exciting opportunities for experiments in materials and surface physics.