Matter and Radiation at Extremes (MRE) is a new professional academic journal, which is now available to publish papers from all over the world on scientific achievements in experimental and theoretical physics, with a focus on matter and radiation at extreme conditions. The journal is hosted by the China Academy of Engineering Physics (CAEP).

Using an X-ray free electron laser (XFEL) at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon, an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago. It took decades to demonstrate this scheme, because it required a very strong X-ray source that could photo-ionize the 1s (K shell) electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs. In this paper, we model the neon inner shell X-ray laser under similar conditions to those used in the XFEL experiments at the SLAC Linac Coherent Light Source (LCLS), and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon. We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n=3-2 transitions in singlyionized Ar and Cu plasmas. These bright, coherent, and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.

The irradiation of few-nm-thick targets by a finite-contrast high-intensity short-pulse laser results in a strong pre-expansion of these targets at the arrival time of the main pulse. The targets decompress to near and lower than critical densities with plasmas extending over few micrometers, i.e. multiple wavelengths. The interaction of the main pulse with such a highly localized but inhomogeneous target leads to the generation of a short channel and further self-focusing of the laser beam. Experiments at the Glass Hybrid OPCPA Scaled Test-bed (GHOST) laser system at University of Texas, Austin using such targets measured non-Maxwellian, peaked electron distribution with large bunch charge and high electron density in the laser propagation direction. These results are reproduced in 2D PIC simulations using the EPOCH code, identifying direct laser acceleration (DLA) as the responsible mechanism. This is the first time that DLA has been observed to produce peaked spectra as opposed to broad, Maxwellian spectra observed in earlier experiments This high-density electrons have potential applications as injector beams for a further wakefield acceleration stage as well as for pump-probe applications.

The octahedral spherical hohlraums have natural superiority in maintaining high radiation symmetry during the entire capsule implosion process in indirect drive inertial confinement fusion. While, in contrast to the cylindrical hohlraums, the narrow space between the laser beams and the spherical hohlraum wall is usually commented. In this Letter, we address this crucial issue and report our experimental work conducted on the SGIII-prototype laser facility which unambiguously demonstrates that a simple design of cylindrical laser entrance hole (LEH) can dramatically improve the laser propagation inside the spherical hohlraums. In addition, the laser beam deflection in the hohlraum is observed for the first time in the experiments. Our 2-dimensional simulation results also verify qualitatively the advantages of the spherical hohlraums with cylindrical LEHs. Our results imply the prospect of adopting the cylindrical LEHs in future spherical ignition hohlraum design.

We review the development of High Energy Density Physics (HEDP) with intense heavy ion beams as a tool to induce extreme states of matter. The development of this field connects intimately to the advances in accelerator physics and technology. We will cover the generation of intense heavy ion beams starting from the ion source and follow the acceleration process and transport to the target. Intensity limitations and potential solutions to overcome these limitations are discussed. This is exemplified by citing examples from existing machines at the Gesellschaft fur Schwerionenforschung (GSI-Darmstadt), the Institute of Theoretical and Experimental Physics in Moscow (ITEP-Moscow), and the Institute of Modern Physics (IMP-Lanzhou). Facilities under construction like the FAIR facility in Darmstadt and the High Intensity Accelerator Facility (HIAF), proposed for China will be included. Developments elsewhere are covered where it seems appropriate along with a report of recent results and achievements.

Pulsed power technology, whereas the electrical energy stored in a relative long period is released in much shorter timescale, is an efficient method to create high energy density physics (HEDP) conditions in laboratory. Around the beginning of this century, China Academy of Engineering Physics (CAEP) began to build some experimental facilities for HEDP investigations, among which the Primary Test Stand (PTS), a multi-module pulsed power facility with a nominal current of 10 MA and a current rising time ~90 ns, is an important achievement on the roadmap of the electro-magnetically driven inertial confinement fusion (ICF) researches. PTS is the first pulsed power facility beyond 10 TW in China. Therefore, all the technologies have to be demonstrated, and all the engineering issues have to be overcome. In this article, the research outline, key technologies and the preliminary HEDP experiments are reviewed. Prospects on HEDP research on PTS and pulsed power development for the next step are also discussed.

Recently we are witnessing the boom of high-pressure science and technology from a small niche field to becoming a major dimension in physical sciences. One of the most important technological advances is the integration of synchrotron nanotechnology with the minute samples at ultrahigh pressures. Applications of high pressure have greatly enhanced our understanding of the electronic, phonon, and doping effects on the newly emerged graphene and related 2D layered materials. High pressure has created exotic stoichiometry even in common Group 17, 15, and 14 compounds and drastically altered the basic s and p bonding of organic compounds. Differential pressure measurements enable us to study the rheology and flow of mantle minerals in solid state, thus quantitatively constraining the geodynamics. They also introduce a new approach to understand defect and plastic deformations of nano particles. These examples open new frontiers of high-pressure research.