Continuous Multi-Cycle Terahertz Measurements of the Electrical Conductivity of Free-Electron Laser Irradiated Warm Dense Gold*

Recently, we developed the capability to directly measure the evolution of DC electrical conductivity of high intensity laser excited solid density plasmas using ultrafast terahertz radiation that overcomes the high frequency (\textgreater 1PHz) electron shielding. Our measurements resolve the DC conductivity in free-electron laser-irradiated gold at lattice heating rate exceeding 10\textasciicircum 14K/s where melting occurs under superheating conditions that produce pressures of the order of 10 GPa [1]. The experimental results further allow us to determine the electron scattering between electron-electron and electron-ion. These unprecedented data will help to test and improve models of warm dense matter. [1] Z. Chen et al., PRL. 121, 075002 (2018)