Journal Article

Creation and diagnosis of a solid-density plasma with an X-ray free-electron laser

Wang, T., Ciricosta, O., Vinko, S. M., Juha, L., Vysin, L., Brown, C. R. D., Turner, J. J., Toleikis, S., Higginbotham, A., Chung, H.-K., Scherz, A., Schlotter, W., Lee, H. J., Engelhorn, K., Wu, B., Graves, C., Messerschmidt, M., Zhu, D., Heimann, P. A., Lee, R. W., Murphy, C. D., Hájková, V., Cho, B. I., Burian, T., Nagler, B., Falcone, R. W., Zastrau, U., Wark, J. S., Chalupský, J., Krzywinski, J., Ping, Y.

2012

Overview

Experimental study of the interactions between intense X-rays and solid matter illustrate the generation of a solid-density plasma governed by electron–ion collisions; these results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological samples, material science investigations, and the study of matter in extreme conditions. Solid progress for X-ray lasers With the advent of free-electron lasers, the high intensities previously only achievable with optical lasers can be produced at X-ray wavelengths. This opens new opportunities for theory and experiment. Here, Vinko et al . report the first detailed study of intense X-ray radiation interacting with solid density matter, carried out on the Linac Coherent Light Source free-electron laser at the SLAC National Accelerator Facility in California. They observe the generation of a solid-density plasma and establish that collisions have a pivotal role. The results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological samples and materials science investigations. Matter with a high energy density (>10 5  joules per cm 3 ) is prevalent throughout the Universe, being present in all types of stars 1 and towards the centre of the giant planets 2 , 3 ; it is also relevant for inertial confinement fusion 4 . Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities 5 , 6 . With the advent of the Linac Coherent Light Source (LCLS) X-ray laser 7 , high-intensity radiation (>10 17  watts per cm 2 , previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated 8 . An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10 6 kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray–matter interactions, and illustrate the importance of electron–ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/33/525 / 639/766/400 / 70 PLASMA PHYSICS AND FUSION TECHNOLOGY / Atomic properties / Chemical properties / Electromagnetism; electron and ion optics / Electrostatic, collective, and linear accelerators / Exact sciences and technology / Experimental methods and instrumentation for elementary-particle and nuclear physics / Experiments / Free electron lasers / Fundamental areas of phenomenology (including applications) / High temperature plasmas / Humanities and Social Sciences / Lasers / letter / Light sources / Materials science / multidisciplinary / Nuclear physics / Origin / Physics / Physics of gases, plasmas and electric discharges / Physics of plasmas and electric discharges / Plasma (Ionized gases) / Plasma properties / Radiation by moving charges / Science / Science (multidisciplinary) / Spectrum analysis / Temperature / Transport properties / Wavelengths / X-ray lasers / X-rays