Femtosecond Single-Shot Measurements of the Temperature of Laser-Shocked Copper

The dynamical compression of condensed matter on nanosecond timescales, with the pressure applied via laser ablation of a surface layer, provides a means to reach pressures far greater than those that can be applied statically in diamond anvil cells. Subsequent pulsed x-ray diffraction provides structural information on a timescale short compared with that of the nanosecond compression. This combination of laser-compression and pulsed diffraction has been applied at a number of high-power laser, synchrotron, and x-ray free-electron-laser (FEL) facilities over the past few decades, providing a wealth of information on high strain-rate deformation physics and phase transitions at pressures from a few GPa well into the multi-TPa regime. Whilst density information can be provided by diffraction, and pressure can be deduced via the VISAR technique, temperature has proven to be a more difficult parameter to measure, particularly when the temperatures are too low to be extracted from pyrometry. We present here a diffraction technique that allows single shot measurements of the temperature to be made, even at relatively low temperatures. Our initial results from the inaugural DiPOLE experiment at the European XFEL show that the conceptually simple method is robust against texture changes of the sample during compression, and gives good agreement with predictions from the SESAME EOS.