Speaker: Justin Wark, University of Oxford
Program Description
A simple glance at the night sky is all it needs to determine that the majority of the visible universe is in the plasma state. Yet despite their prevalence, our understanding of some very fundamental physics of hot dense plasmas (such as their equation of state, or radiative properties) remains elusive. This is particularly the case when the plasmas are 'strongly-coupled' - that is to say when the coulomb energy due to the charged particles is comparable to their thermal energy. In this case we can't ignore the potential energy (which one does for an ideal gas) or the kinetic energy (which one does to zeroth order for a solid), but we are in a hinterland where a perturbative approach won't work. As well as not yielding to simple theoretical analysis, hot dense plasmas have proven difficult to study in the laboratory - a solid-density plasma at a temperature of a couple of million Kelvin exerts a pressure of a few tens of millions of atmospheres, and thus is neither readily produced or contained. In this talk I will explain why LCLS has caught the attention of those of us interested in both creating and diagnosing such extreme states of matter. The high brightness of LCLS allows us to heat matter with X-rays to millions of degrees, and the brevity of the pulses is such that the targets do not have time to 'blow-up' before we interrogate them - they are confined by their own inertia. I will report on our initial experiments, recently published in Nature, that produced matter at conditions comparable to those deep within the sun, and demonstrate how LCLS has already challenged our understanding of some of the basic physics of dense plasmas.
