Surface heating of wire plasmas using laser-irradiated cone geometries

Petawatt lasers can generate extreme states of matter, makingthem unique tools for high-energy-density physics. Pressures inthe gigabar regime can potentially be generated with cone-wiretargets when the coupling efficiency is high and temperaturesreach 2–4keV (ref. 1). The only other method of obtaining suchgigantic pressures is to use the megajoule laser facilities beingconstructed (National Ignition Facility and Laser M´egaJoule).The energy can be transported over surprisingly long distancesbut, until now, the guiding mechanism has remained unclear.Here, we present the first definitive experimental proof that theheatingismaximizedclosetothewiresurface,bycomparisonofinterferometric measurements with hydrodynamic simulations.New hybrid particle-in-cell simulations show the complex fieldstructures for the first time, including a reversal of the magneticfieldontheinsideofthewire.Thisincreasesthereturncurrentina spatially separated thin layer below the wire surface, resultingin the enhanced level of ohmic heating. There are a significantnumber of applications in high-energy-density science, rangingfromequation-of-statestudiestobright,hardX-raysources,thatwillbenefitfromthisnewunderstandingofenergytransport.