M. J. Jensen

Laser-cooled ion plasmas in Penning traps

A laser-cooled ion plasma in a Penning trap provides a rigorous realization of a strongly coupled one-component plasma. After a brief review of the crystal structures that have been observed in Penning traps, we summarize two recent experiments. First we describe careful measurements of the stability of the plasma rotation which is controlled by a rotating electric field. We then discuss the excitation of plasma wakes produced by radiation pressure from a laser.

Temperature Measurements of Laser‐Cooled Ions in a Penning Trap

Between 104 and 106 9Be+ ions are trapped in a Penning trap. The ions are laser‐cooled to ∼millikelvin temperatures, where they form ion crystals. This system is an example of a strongly coupled one‐component plasma. By means of Doppler laser spectroscopy we have measured the temperature and heating rate of the plasma. Initially the heating rate is low, 60 ± 40 mK/s, but after about 100 ms the plasma heats up rapidly to a few kelvin. The onset of the rapid heating coincides with the solid‐liquid phase transition.