Studies of the Kα X-ray spectra of low-density SiO2 aerogel induced by Ca projectiles for different penetration depths

Abstract The classical definition of the virial temperature of a galaxy halo excludes a fundamental contribution to the energy partition of the halo: the kinetic energy of nonthermal gas motions. Using simulations of low-redshift, ∼L* galaxies from the Figuring Out Gas & Galaxies In Enzo (FOGGIE) project that are optimized to resolve low-density gas, we show that the kinetic energy of nonthermal motions is roughly equal to the energy of thermal motions. The simulated FOGGIE halos have ∼2× lower bulk temperatures than expected from a classical virial equilibrium, owing to significant nonthermal kinetic energy that is formally excluded from the definition of T vir. We explicitly derive a modified virial temperature including nonthermal gas motions that provides a more accurate description of gas temperatures for simulated halos in virial equilibrium. Strong bursts of stellar feedback drive the simulated FOGGIE halos out of virial equilibrium, but the halo gas cannot be accurately described by the standard virial temperature even when in virial equilibrium. Compared to the standard virial temperature, the cooler modified virial temperature implies other effects on halo gas: (i) the thermal gas pressure is lower, (ii) radiative cooling is more efficient, (iii) O vi absorbing gas that traces the virial temperature may be prevalent in halos of a higher mass than expected, (iv) gas mass estimates from X-ray surface brightness profiles may be incorrect, and (v) turbulent motions make an important contribution to the energy balance of a galaxy halo.

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Progress in HXR diagnostics at GOLEM and COMPASS tokamaks

Journal of Instrumentation ◽

10.1088/1748-0221/17/01/c01033 ◽

2022 ◽

Vol 17 (01) ◽

pp. C01033

Author(s):

J. Cerovsky ◽

O. Ficker ◽

V. Svoboda ◽

E. Macusova ◽

J. Mlynar ◽

...

Keyword(s):

Diagnostic Tool ◽

Runaway Electron ◽

Sampling Rate ◽

Data Acquisition System ◽

Scintillation Detectors ◽

Low Density ◽

Runaway Electrons ◽

X Ray ◽

Radiation Induced ◽

Pulse Analysis

Abstract Scintillation detectors are widely used for hard X-ray spectroscopy and allow us to investigate the dynamics of runaway electrons in tokamaks. This diagnostic tool proved to be able to provide information about the energy or the number of runaway electrons. Presently it has been used for runaway studies at the GOLEM and the COMPASS tokamaks. The set of scintillation detectors used at both tokamaks was significantly extended and improved. Besides NaI(Tl) (2 × 2 inch) scintillation detectors, YAP(Ce) and CeBr3 were employed. The data acquisition system was accordingly improved and the data from scintillation detectors is collected with appropriate sampling rate (≈300 MHz) and sufficient bandwidth (≈100 MHz) to allow a pulse analysis. Up to five detectors can currently simultaneously monitor hard X-ray radiation at the GOLEM. The same scintillation detectors were also installed during the runaway electron campaign at the COMPASS tokamak. The aim of this contribution is to report progress in diagnostics of HXR radiation induced by runaway electrons at the GOLEM and the COMPASS tokamaks. The data collected during the 12th runaway electron campaign (2020) at COMPASS shows that count rates during typical low-density runaway electron discharges are in a range of hundreds of kHz and detected photon energies go up to 10 MeV (measured outside the tokamak hall). Acquired data from experimental campaigns from both machines will be discussed.

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X-ray studies of the transformation from high- to low-density amorphous water

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2018.0164 ◽

2019 ◽

Vol 377 (2146) ◽

pp. 20180164 ◽

Cited By ~ 5

Author(s):

Daniel Mariedahl ◽

Fivos Perakis ◽

Alexander Späh ◽

Harshad Pathak ◽

Kyung Hwan Kim ◽

...

Keyword(s):

Ambient Pressure ◽

Structural Evolution ◽

High Energy ◽

Real Space ◽

High Density ◽

Low Density ◽

X Ray ◽

Amorphous Ice ◽

Density State ◽

Amorphous States

Here we report about the structural evolution during the conversion from high-density amorphous ices at ambient pressure to the low-density state. Using high-energy X-ray diffraction, we have monitored the transformation by following in reciprocal space the structure factor S OO ( Q ) and derived in real space the pair distribution function g OO ( r ). Heating equilibrated high-density amorphous ice (eHDA) at a fast rate (4 K min –1 ), the transition to the low-density form occurs very rapidly, while domains of both high- and low-density coexist. On the other hand, the transition in the case of unannealed HDA (uHDA) and very-high-density amorphous ice is more complex and of continuous nature. The direct comparison of eHDA and uHDA indicates that the molecular structure of uHDA contains a larger amount of tetrahedral motives. The different crystallization behaviour of the derived low-density amorphous states is interpreted as emanating from increased tetrahedral coordination present in uHDA. This article is part of the theme issue ‘The physics and chemistry of ice: scaffolding across scales, from the viability of life to the formation of planets'.

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Radiation-hydrodynamical models of X-ray photoevaporation in carbon-depleted circumstellar discs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2939 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5596-5614 ◽

Cited By ~ 2

Author(s):

Lisa Wölfer ◽

Giovanni Picogna ◽

Barbara Ercolano ◽

Ewine F van Dishoeck

Keyword(s):

Mass Loss ◽

Gas Phase ◽

Central Star ◽

X Rays ◽

Hydrodynamical Models ◽

X Ray ◽

Energetic Radiation ◽

Low Metallicity ◽

Penetration Depths ◽

Loss Rates

ABSTRACT The so-called transition discs provide an important tool to probe various mechanisms that might influence the evolution of protoplanetary discs and therefore the formation of planetary systems. One of these mechanisms is photoevaporation due to energetic radiation from the central star, which can in principal explain the occurrence of discs with inner cavities like transition discs. Current models, however, fail to reproduce a subset of the observed transition discs, namely objects with large measured cavities and vigorous accretion. For these objects the presence of (multiple) giant planets is often invoked to explain the observations. In our work, we explore the possibility of X-ray photoevaporation operating in discs with different gas-phase depletion of carbon and show that the influence of photoevaporation can be extended in such low-metallicity discs. As carbon is one of the main contributors to the X-ray opacity, its depletion leads to larger penetration depths of X-rays in the disc and results in higher gas temperatures and stronger photoevaporative winds. We present radiation-hydrodynamical models of discs irradiated by internal X-ray + EUV radiation assuming carbon gas-phase depletions by factors of three, 10, and 100 and derive realistic mass-loss rates and profiles. Our analysis yields robust temperature prescriptions as well as photoevaporative mass-loss rates and profiles which may be able to explain a larger fraction of the observed diversity of transition discs.

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Effect of Sintering Temperature on Property of Low-Density Ceramic Proppant Adding Coal Gangue

Materials Science ◽

10.5755/j01.ms.26.1.19376 ◽

2019 ◽

Vol 26 (1) ◽

pp. 94-98

Author(s):

Jianying HAO ◽

Huilan HAO ◽

Yunfeng GAO ◽

Xianjun LI ◽

Mei QIN ◽

...

Keyword(s):

Solid Waste ◽

Bulk Density ◽

Apparent Density ◽

Sintering Temperature ◽

Coal Gangue ◽

Low Density ◽

X Ray Diffraction ◽

X Ray ◽

Sintering Method ◽

Waste Coal

Calcined flint clay (45.6 wt.% Al2O3) and solid waste coal gangue were used to prepare low-density ceramic proppant by solid state sintering method. The density and breakage ratio of the ceramic proppant were systematically investigated as a function of sintering temperature. The morphology and phase composition of the ceramic proppant were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the ceramic proppant is composed of rod-like mullite and granular cristobalite. Bulk density and apparent density of the proppant first rise and then slightly decrease with increasing the sintering temperature, while breakage ratios under 35 MPa and 52 MPa pressure gradually decrease and then increase. As the sintering temperature increases up to 1400 °C, the ceramic proppant shows denser microstructure. The proppant sintered at 1400 °C have the best performance with 1.27 g/cm3 of bulk density, 2.79 g/cm3 of apparent density, 3.27 % of breakage ratio under 35 MPa closed pressure and 8.36 % of breakage ratio under 52 MPa closed pressure, which conform to the requirement of low-density ceramic proppant. The addition of solid waste can greatly reduce the preparation cost of the ceramic proppant.

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Heating of the Interstellar Medium by Supernova Remnants

Symposium - International Astronomical Union ◽

10.1017/s0074180900034173 ◽

1983 ◽

Vol 101 ◽

pp. 385-392

Author(s):

Donald P. Cox

Keyword(s):

Interstellar Medium ◽

Supernova Remnants ◽

Supernova Remnant ◽

Low Density ◽

The Sun ◽

X Ray ◽

Interstellar Material ◽

X Ray Background

We observe the heating of interstellar material in young supernova remnants (SNR). In addition, when analyzing the soft X-ray background we find evidence for large isolated regions of apparently hot, low density material. These, we infer, may have been heated by supernovae. One such region seems to surround the Sun. This has been modeled as a supernova remnant viewed from within. The most reasonable parameters are ambient density no ~ 0.004 cm−3, radius of about 100 pc, age just over 105 years (Cox and Anderson 1982).

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