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Speed of sound in methane under conditions of planetary interiors
Authors:
Thomas G. White,
Hannah Poole,
Emma E. McBride,
Matthew Oliver,
Adrien Descamps,
Luke B. Fletcher,
W. Alex Angermeier,
Cameron H. Allen,
Karen Appel,
Florian P. Condamine,
Chandra B. Curry,
Francesco Dallari,
Stefan Funk,
Eric Galtier,
Eliseo J. Gamboa,
Maxence Gauthier,
Peter Graham,
Sebastian Goede,
Daniel Haden,
Jongjin B. Kim,
Hae Ja Lee,
Benjamin K. Ofori-Okai,
Scott Richardson,
Alex Rigby,
Christopher Schoenwaelder
, et al. (10 additional authors not shown)
Abstract:
We present direct observations of acoustic waves in warm dense matter. We analyze wave-number- and energy-resolved x-ray spectra taken from warm dense methane created by laser heating a cryogenic liquid jet. X-ray diffraction and inelastic free-electron scattering yield sample conditions of 0.3$\pm$0.1 eV and 0.8$\pm$0.1 g/cm$^3$, corresponding to a pressure of $\sim$13 GPa. Inelastic x-ray scatte…
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We present direct observations of acoustic waves in warm dense matter. We analyze wave-number- and energy-resolved x-ray spectra taken from warm dense methane created by laser heating a cryogenic liquid jet. X-ray diffraction and inelastic free-electron scattering yield sample conditions of 0.3$\pm$0.1 eV and 0.8$\pm$0.1 g/cm$^3$, corresponding to a pressure of $\sim$13 GPa. Inelastic x-ray scattering was used to observe the collective oscillations of the ions. With a highly improved energy resolution of $\sim$50 meV, we could clearly distinguish the Brillouin peaks from the quasielastic Rayleigh feature. Data at different wave numbers were utilized to derive a sound speed of 5.9$\pm$0.5 km/s, marking a high-temperature data point for methane and demonstrating consistency with Birch's law in this parameter regime.
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Submitted 3 May, 2024; v1 submitted 13 November, 2023;
originally announced November 2023.
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Physically motivated moment-tensor decomposition for mining-induced seismicity
Authors:
Alex Rigby
Abstract:
Abstract Compared to existing schemes, the decomposition of moment tensors for mining-induced seismic events into closing-crack and double-couple components has the advantage that each can be interpreted in terms of a physical source process (excavation convergence and slip/shear, respectively). Obviously, not every moment tensor permits such a decomposition, and we translate existing bounds on th…
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Abstract Compared to existing schemes, the decomposition of moment tensors for mining-induced seismic events into closing-crack and double-couple components has the advantage that each can be interpreted in terms of a physical source process (excavation convergence and slip/shear, respectively). Obviously, not every moment tensor permits such a decomposition, and we translate existing bounds on those that do to the Hudson source-type plot. For moment tensors falling within these bounds, it has previously been noted that there will be a infinite set of possible decompositions in general. We derive an implicit equation defining this set and suggest physically motivated criteria that can be used to select a single decomposition from it. Furthermore, for moment tensors falling outside the source-type bounds, we present a simple geometric scheme for determining the closest moment tensor within them (which can then be decomposed). To demonstrate the methods developed in this paper, we apply them to two catalogues of mining-induced seismicity.
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Submitted 28 October, 2023; v1 submitted 18 February, 2023;
originally announced February 2023.
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Description of seismic sources in underground mines: Dynamic stress fracturing around tunnels and strainbursting
Authors:
Dmitriy Malovichko,
Alex Rigby
Abstract:
This paper considers dynamic fracturing of the rockmass surrounding a tunnel statically loaded by compressional stress as a possible source of seismic events in underground mines. This begins with two-dimensional dynamic modelling of failure for six plausible scenarios. In each case, the seismic source derived from these models has significant negative isotropic and negative compensated linear vec…
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This paper considers dynamic fracturing of the rockmass surrounding a tunnel statically loaded by compressional stress as a possible source of seismic events in underground mines. This begins with two-dimensional dynamic modelling of failure for six plausible scenarios. In each case, the seismic source derived from these models has significant negative isotropic and negative compensated linear vector dipole components as well as a P-axis approximately aligned with the direction of maximum compressional principal stress. These features indicate that at wavelengths larger than the diameter of the tunnel and the extent of damage along it, seismic radiation is controlled by the elastic convergence of the surrounding rockmass rather than by rock fracturing. An analytical approximation of the source mechanism is suggested that is based solely on mechanical and geometric properties: the magnitudes $σ_{\mathrm{max}}$ and $σ_{\mathrm{min}}$ of the maximum and minimum principal stresses orthogonal to the tunnel's axis, the Poisson's ratio $ν$ of the rockmass, the length $L_{3}$ of dynamic fracturing along the tunnel, the effective tunnel dimension $\bar{L_{A}}$, and the increase in depth of failure $\triangle d_{f}^{A}$ in the direction of $σ_{\mathrm{min}}$. Furthermore, it is shown that the scalar seismic moment can be approximated as $|\mathbf{M}|\approx2[(1-ν)/(1-2ν)]|σ_{max}|L_{3}\bar{L_{A}}\triangle d_{f}^{A}$. The suggested approximations are considered in the context of seismic data from a real underground mine. It is shown that many mechanisms inverted from observed waveforms are consistent with the suggested model and that the proposed source mechanism approximation can be used for the forensic analysis of damaging seismic events and quantitative monitoring of the evolution of fractured zones around tunnels.
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Submitted 15 May, 2022;
originally announced May 2022.
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Strong suppression of heat conduction in a laboratory replica of galaxy-cluster turbulent plasmas
Authors:
J. Meinecke,
P. Tzeferacos,
J. S. Ross,
A. F. A. Bott,
S. Feister,
H. -S. Park,
A. R. Bell,
R. Blandford,
R. L. Berger,
R. Bingham,
A. Casner,
L. E. Chen,
J. Foster,
D. H. Froula,
C. Goyon,
D. Kalantar,
M. Koenig,
B. Lahmann,
C. -K. Li,
Y. Lu,
C. A. J. Palmer,
R. Petrasso,
H. Poole,
B. Remington,
B. Reville
, et al. (10 additional authors not shown)
Abstract:
Galaxy clusters are filled with hot, diffuse X-ray emitting plasma, with a stochastically tangled magnetic field whose energy is close to equipartition with the energy of the turbulent motions \cite{zweibel1997, Vacca}. In the cluster cores, the temperatures remain anomalously high compared to what might be expected considering that the radiative cooling time is short relative to the Hubble time \…
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Galaxy clusters are filled with hot, diffuse X-ray emitting plasma, with a stochastically tangled magnetic field whose energy is close to equipartition with the energy of the turbulent motions \cite{zweibel1997, Vacca}. In the cluster cores, the temperatures remain anomalously high compared to what might be expected considering that the radiative cooling time is short relative to the Hubble time \cite{cowie1977,fabian1994}. While feedback from the central active galactic nuclei (AGN) \cite{fabian2012,birzan2012,churazov2000} is believed to provide most of the heating, there has been a long debate as to whether conduction of heat from the bulk to the core can help the core to reach the observed temperatures \cite{narayan2001,ruszkowski2002,kunz2011}, given the presence of tangled magnetic fields. Interestingly, evidence of very sharp temperature gradients in structures like cold fronts implies a high degree of suppression of thermal conduction \cite{markevitch2007}. To address the problem of thermal conduction in a magnetized and turbulent plasma, we have created a replica of such a system in a laser laboratory experiment. Our data show a reduction of local heat transport by two orders of magnitude or more, leading to strong temperature variations on small spatial scales, as is seen in cluster plasmas \cite{markevitch2003}.
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Submitted 18 May, 2021;
originally announced May 2021.
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Time-resolved fast turbulent dynamo in a laser plasma
Authors:
A. F. A. Bott,
P. Tzeferacos,
L. Chen,
C. A. J. Palmer,
A. Rigby,
A. Bell,
R. Bingham,
A. Birkel,
C. Graziani,
D. H. Froula,
J. Katz,
M. Koenig,
M. W. Kunz,
C. K. Li,
J. Meinecke,
F. Miniati,
R. Petrasso,
H. -S. Park,
B. A. Remington,
B. Reville,
J. S. Ross,
D. Ryu,
D. Ryutov,
F. Séguin,
T. G. White
, et al. (3 additional authors not shown)
Abstract:
Understanding magnetic-field generation and amplification in turbulent plasma is essential to account for observations of magnetic fields in the universe. A theoretical framework attributing the origin and sustainment of these fields to the so-called fluctuation dynamo was recently validated by experiments on laser facilities in low-magnetic-Prandtl-number plasmas ($\mathrm{Pm} < 1$). However, the…
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Understanding magnetic-field generation and amplification in turbulent plasma is essential to account for observations of magnetic fields in the universe. A theoretical framework attributing the origin and sustainment of these fields to the so-called fluctuation dynamo was recently validated by experiments on laser facilities in low-magnetic-Prandtl-number plasmas ($\mathrm{Pm} < 1$). However, the same framework proposes that the fluctuation dynamo should operate differently when $\mathrm{Pm} \gtrsim 1$, the regime relevant to many astrophysical environments such as the intracluster medium of galaxy clusters. This paper reports a new experiment that creates a laboratory $\mathrm{Pm} \gtrsim 1$ plasma dynamo for the first time. We provide a time-resolved characterization of the plasma's evolution, measuring temperatures, densities, flow velocities and magnetic fields, which allows us to explore various stages of the fluctuation dynamo's operation. The magnetic energy in structures with characteristic scales close to the driving scale of the stochastic motions is found to increase by almost three orders of magnitude from its initial value and saturate dynamically. It is shown that the growth of these fields occurs exponentially at a rate that is much greater than the turnover rate of the driving-scale stochastic motions. Our results point to the possibility that plasma turbulence produced by strong shear can generate fields more efficiently at the driving scale than anticipated by idealized MHD simulations of the nonhelical fluctuation dynamo; this finding could help explain the large-scale fields inferred from observations of astrophysical systems.
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Submitted 24 July, 2020;
originally announced July 2020.
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Transport of high-energy charged particles through spatially-intermittent turbulent magnetic fields
Authors:
L. E. Chen,
A. F. A. Bott,
P. Tzeferacos,
A. Rigby,
A. Bell,
R. Bingham,
C. Graziani,
J. Katz,
M. Koenig,
C. K. Li,
R. Petrasso,
H. -S. Park,
J. S. Ross,
D. Ryu,
T. G. White,
B. Reville,
J. Matthews,
J. Meinecke,
F. Miniati,
E. G. Zweibel,
S. Sarkar,
A. A. Schekochihin,
D. Q. Lamb,
D. H. Froula,
G. Gregori
Abstract:
Identifying the sources of the highest energy cosmic rays requires understanding how they are deflected by the stochastic, spatially intermittent intergalactic magnetic field. Here we report measurements of energetic charged-particle propagation through a laser-produced magnetized plasma with these properties. We characterize the diffusive transport of the particles experimentally. The results sho…
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Identifying the sources of the highest energy cosmic rays requires understanding how they are deflected by the stochastic, spatially intermittent intergalactic magnetic field. Here we report measurements of energetic charged-particle propagation through a laser-produced magnetized plasma with these properties. We characterize the diffusive transport of the particles experimentally. The results show that the transport is diffusive and that, for the regime of interest for the highest-energy cosmic rays, the diffusion coefficient is unaffected by the spatial intermittency of the magnetic field.
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Submitted 30 March, 2020; v1 submitted 13 August, 2018;
originally announced August 2018.
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Setup for meV-resolution inelastic X-ray scattering measurements at the Matter in Extreme Conditions Endstation at the LCLS
Authors:
E. E. McBride,
T. G. White,
A. Descamps,
L. B. Fletcher,
K. Appel,
F. Condamine,
C. B. Curry,
F. Dallari,
S. Funk,
E. Galtier,
M. Gauthier,
S. Goede,
J. B. Kim,
H. J. Lee,
B. K. Ofori-Okai,
M. Oliver,
A. Rigby,
C. Schoenwaelder,
P. Sun,
Th. Tschentscher,
B. B. L. Witte,
U. Zastrau,
G. Gregori,
B. Nagler,
J. Hastings
, et al. (2 additional authors not shown)
Abstract:
We describe a setup for performing inelastic X-ray scattering measurements at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source (LCLS). This technique is capable of performing high-, meV-resolution measurements of dynamic ion features in both crystalline and non-crystalline materials. A four-bounce silicon (533) monochromator was used in conjunction with three si…
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We describe a setup for performing inelastic X-ray scattering measurements at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source (LCLS). This technique is capable of performing high-, meV-resolution measurements of dynamic ion features in both crystalline and non-crystalline materials. A four-bounce silicon (533) monochromator was used in conjunction with three silicon (533) diced crystal analyzers to provide an energy resolution of ~50 meV over a range of ~500 meV in single shot measurements. In addition to the instrument resolution function, we demonstrate the measurement of longitudinal acoustic phonon modes in polycrystalline diamond. Furthermore, this setup may be combined with the high intensity laser drivers available at MEC to create warm dense matter, and subsequently measure ion acoustic modes.
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Submitted 5 June, 2018;
originally announced June 2018.
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Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma
Authors:
P. Tzeferacos,
A. Rigby,
A. Bott,
A. R. Bell,
R. Bingham,
A. Casner,
F. Cattaneo,
E. M. Churazov,
J. Emig,
F. Fiuza,
C. B. Forest,
J. Foster,
C. Graziani,
J. Katz,
M. Koenig,
C. -K. Li,
J. Meinecke,
R. Petrasso,
H. -S. Park,
B. A. Remington,
J. S. Ross,
D. Ryu,
D. Ryutov,
T. G. White,
B. Reville
, et al. (5 additional authors not shown)
Abstract:
Magnetic fields are ubiquitous in the Universe. Extragalactic disks, halos and clusters have consistently been shown, via diffuse radio-synchrotron emission and Faraday rotation measurements, to exhibit magnetic field strengths ranging from a few nG to tens of $μ$G. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are…
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Magnetic fields are ubiquitous in the Universe. Extragalactic disks, halos and clusters have consistently been shown, via diffuse radio-synchrotron emission and Faraday rotation measurements, to exhibit magnetic field strengths ranging from a few nG to tens of $μ$G. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. The standard theoretical model for the origin of these strong magnetic fields is through the amplification of tiny seed fields via turbulent dynamo to the level consistent with current observations. Here we demonstrate, using laser-produced colliding plasma flows, that turbulence is indeed capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. These results support the notion that turbulent dynamo is a viable mechanism responsible for the observed present-day magnetization of the Universe.
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Submitted 9 February, 2017;
originally announced February 2017.
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Numerical modeling of laser-driven experiments aiming to demonstrate magnetic field amplification via turbulent dynamo
Authors:
P. Tzeferacos,
A. Rigby,
A. Bott,
A. R. Bell,
R. Bingham,
A. Casner,
F. Cattaneo,
E. M. Churazov,
J. Emig,
N. Flocke,
F. Fiuza,
C. B. Forest,
J. Foster,
C. Graziani,
J. Katz,
M. Koenig,
C. -K. Li,
J. Meinecke,
R. Petrasso,
H. -S. Park,
B. A. Remington,
J. S. Ross,
D. Ryu,
D. Ryutov,
K. Weide
, et al. (7 additional authors not shown)
Abstract:
The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between the filaments of galaxy clusters to several teragauss in black holes and neutron stars. The standard model behind cosmological magnetic fields is the nonlinear amplification of seed fields via turbulent dynamo to the values observed. We have conceived experiments that aim to demonstrate and…
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The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between the filaments of galaxy clusters to several teragauss in black holes and neutron stars. The standard model behind cosmological magnetic fields is the nonlinear amplification of seed fields via turbulent dynamo to the values observed. We have conceived experiments that aim to demonstrate and study the turbulent dynamo mechanism in the laboratory. Here we describe the design of these experiments through simulation campaigns using FLASH, a highly capable radiation magnetohydrodynamics code that we have developed, and large-scale three-dimensional simulations on the Mira supercomputer at Argonne National Laboratory. The simulation results indicate that the experimental platform may be capable of reaching a turbulent plasma state and study dynamo amplification. We validate and compare our numerical results with a small subset of experimental data using synthetic diagnostics.
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Submitted 9 February, 2017;
originally announced February 2017.