Temperature Moderation in Ultracold Plasmas

Jacob Roberts, Chad Fertig, and Steve Rolston

By combining the techniques of laser cooling and photoionization, we have created a reasonably dense (up to 1010 cm-3), stable, neutral plasma at ultracold temperatures from a sample of metastable Xenon atoms.  Altering the frequency and intensity of the photoionzing laser allows us to control the initial temperature (Telectron = 1-1000 K) and density of the plasma. In the absence of any other considerations, this control over temperature and density should allow us a simple way to create plasmas in the interesting strong-coupling regime. Measurements of the plasma temperature, however, shows that after formation of the plasma the heating and cooling mechanisms that are both present tend to bring plasmas to similar temperatures after several ms of evolution time regardless of the initial conditions.  While these temperature measurements indicate that the strong-coupling regime may be difficult to achieve, they produce additional insight into the behavior of these ultracold plasma systems and will allow more detailed studies of plasma dynamics at low temperatures.