Fundamental Physics At Extremes
Xian bin Huang
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Jets are commonly observed astrophysical phenomena. To study the x-ray emission characteristics of jets, a series of radial foil Z-pinch experiments are carried out on the Primary Test Stand at the Institute of Fluid Physics, China Academy of Engineering Physics. In these experiments, x-ray emission ranging from the soft region (0.1–10 keV) to the hard region (10 keV–500 keV) is observed when the magnetic cavity breaks. The radiation flux of soft x-rays is measured by an x-ray diode and the dose rate of the hard x-rays by an Si-PIN detector. The experimental results indicate that the energy of the soft x-rays is several tens of kilojoules and that of the hard x-rays is ～200 J. The radiation mechanism of the x-ray emission is briefly analyzed. This analysis indicates that the x-ray energy and the plasma kinetic energy come from the magnetic energy when the magnetic cavity breaks. The soft x-rays are thought to be produced by bremsstrahlung of thermal electrons (～100 eV), and the hard x-rays by bremsstrahlung of super-hot electrons (～mega-electron-volt). These results may be helpful to explain the x-ray emission by the jets from young stellar objects.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.014401
High Pressure Physics and Materials Science
Metal halide perovskites (HPVs) have been greatly developed over the last decade, with various compositions, dimensionalities, and morphologies, leading to an emergence of high-performance photovoltaic and optoelectronic applications. Despite the tremendous progress made, challenges remain, which calls for a better understanding of the fundamental mechanisms. Pressure, a thermodynamic variable, provides a powerful tool to tune materials’ structures and properties. In combination with in situ characterization methods, high-pressure research could provide a better fundamental understanding. In this review, we summarize the recent studies of the dramatic, pressure-induced changes that occur in HPVs, particularly the enhanced and emergent properties induced under high pressure and their structure-property relationships. We first introduce the characteristics of HPVs and the basic knowledge of high-pressure techniques, as well as in situ characterization methods. We then discuss the effects of pressure on HPVs with different compositions, dimensionalities, and morphologies, and underline their common features and anomalous behaviors. In the last section, we highlight the main challenges and provide suggestions for possible future research on high-pressure HPVs.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.018201
Recent advances in high-pressure technologies and large-scale experimental and computational facilities have enabled scientists, at an unprecedented rate, to discover and predict novel states and materials under the extreme pressure-temperature conditions found in deep, giant-planet interiors. Based on a well-documented body of work in this field of high-pressure research, we elucidate the fundamental principles that govern the chemistry of dense solids under extreme conditions. These include: (i) the pressure-induced evolution of chemical bonding and structure of molecular solids to extended covalent solids, ionic solids and, ultimately, metallic solids, as pressure increases to the terapascal regime; (ii) novel properties and complex transition mechanisms, arising from the subtle balance between electron hybridization (bonding) and electrostatic interaction (packing) in densely packed solids; and (iii) new dense framework solids with high energy densities, and with tunable properties and stabilities under ambient conditions. Examples are taken primarily from low-Z molecular systems that have scientific implications for giant-planet models, condensed materials physics, and solid-state core-electron chemistry.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.018202
Andrea L. Kritcher
Madison E. Martin
Robert E. Tipton
Heather D. Whitley
Damian C. Swift
Benjamin L. Bachmann
Amy E. Lazicki
Natalie B. Kostinski
Brian R. Maddox
Gilbert W. Collins
Siegfried H. Glenzer
Roger W. Falcone
Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials, such as CH plastic at extreme pressures, up to 800 Mbar. The “Gbar” design employs a strong spherically converging shock launched through a solid ball of material using a hohlraum radiation drive. The shock front conditions are characterized using x-ray radiography. In this paper we examine the role of radiation in heating the unshocked material in front of the shock to understand the impact it has on equation of state measurements and how it drives the measured data off the theoretical Hugoniot curve. In particular, the two main sources of radiation heating are the preheating of the unshocked material by the high-energy kilo-electron-volt x-rays in the hohlraum and the heating of the material in front of the shock, as the shocked material becomes hot enough to radiate significantly. Using our model, we estimate that preheating can reach 4 eV in unshocked material, and that radiation heating can begin to drive data off the Hugoniot significantly, as pressures reach above 400 Mb.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.018401
Castable solids from Aremco (//www.aremco.com/potting-casting-materials/) are convenient media for pressure transmission in multianvil geometries of complex shape. A zirconia-based castable ceramic, Aremco Ceramacast 646, is introduced and compared to MgO-Al2O3-SiO2-based Aremco Ceramacast 584. Ceramacast 646 has some advantages over the widely used Ceramacast 584; these include ease of consistent fabrication and better thermal insulation. Some disadvantages are poorer efficiency in converting press thrust to sample pressure and slower quenching rates. Potential applications are informed by these differences.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.018402
S. I. Kawaguchi
An overview of the recently renovated high-pressure X-ray diffraction (XRD) BL10XU beamline for the diamond anvil cell at SPring-8 is presented. The renovation includes the replacement of the X-ray source and monochromator, enhanced focusing systems for high-energy XRD, and recent progress in the sample environment control techniques that are available for high-pressure studies. Other simultaneous measurement techniques for combination with XRD, such as Raman scattering spectroscopy and M?ssbauer spectroscopy, have been developed to obtain complementary information under extreme conditions. These advanced techniques are expected to make significant contributions to in-depth understanding of various and complicated high-pressure phenomena. The experience gained with the BL10XU beamline could help promote high-pressure research in future synchrotron radiation facilities.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.018403
Pulsed Power Technology and High Power Electromagnetics
Powerful lasers interacting with solid targets can generate intense electromagnetic pulses (EMPs). In this study, EMPs produced by a pulsed laser (1 ps, 100 J) shooting at CH targets doped with different titanium (Ti) contents at the XG-III laser facility are measured and analyzed. The results demonstrate that the intensity of EMPs first increases with Ti doping content from 1% to 7% and then decreases. The electron spectra show that EMP emission is closely related to the hot electrons ejected from the target surface, which is confirmed by an analysis based on the target–holder–ground equivalent antenna model. The conclusions of this study provide a new approach to achieve tunable EMP radiation by adjusting the metal content of solid targets, and will also help in understanding the mechanism of EMP generation and ejection of hot electrons during laser coupling with targets.
PDF全文 Matter and Radiation at Extremes, 2020年第5卷第1期 pp.017401