Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

Abstract

We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. The sensitivity of the measurements to thermal conductivity is confirmed by simulations. V

Thermomechanical response of thickly tamped targets and diamond anvil cells under pulsed hard x-ray irradiation

“…Such practical challenges of using radiation heating to study equilibrium warm dense matter in the laboratory often complicate the experimental study of equilibrium extreme systems common in nature and technology. Other methods of irradiative volumetric energy deposition providing access to similar states of matter have similar limitations, include intense proton 4,11 , heavy ion 12 , and electron 8 beams. Dynamic compression, the driving of compression (i.e.…”

“…One strategy to extend the lifetime of an irradiation-driven warm dense state is to provide a tamper material around samples through which energy may be deposited and which delay, prevent, or otherwise control expansion [10][11][12][23][24][25] , such as by extending the time it takes pressure release waves and cracks to propagate through the heated target. This tamping approach can even confine the heated region entirely, enabling recovery of high density samples quenched from conditions that would normally lead to vaporization 23 .…”

“…metal) layer between transparent (i.e. dielectric) tamper materials 10,11,24 , by tightly-focussing the beam within the tamper itself 23 , or other configurations such as utilizing energetic electron transport to deposit energy deeply in a target 2 . However, tamping using high-power optical laser irradiation is limited by the need to deliver sufficient energy through the tamper to the sample, and thus depends on the optical transmission of the material under high brightness radiation, often requiring thin tampers at all but the lowest irradiances 10 which limit the efficacy of this strategy.…”

“…Intense x-rays also rapidly heat matter 3,7,9,11,[26][27][28][29][30] . This energy deposition may be introduced deliberately (e.g.…”

“…to optical lasers or ion beams 7,27,30 , and scaling up of targets to enable larger irradiated volumes 7,30 . X-ray heating performed with large optical laser 11,30 , pulsed-power 25 , and free electron laser (FEL) 3,7,9,11,26,27,29 facilities has been demonstrated. Many of these studies used lower photon energies (hundreds of eV to several keV) which can still limit the potential thickness and materials of target components and hence experimental timescales.…”