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Pak C, Billings V, Schlitters M, Bergeson SD, Murillo MS. Preliminary study of plasma modes and electron-ion collisions in partially magnetized strongly coupled plasmas. Phys Rev E 2024; 109:015201. [PMID: 38366520 DOI: 10.1103/physreve.109.015201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 12/07/2023] [Indexed: 02/18/2024]
Abstract
Magnetic fields influence ion transport in plasmas. Straightforward comparisons of experimental measurements with plasma theories are complicated when the plasma is inhomogeneous, far from equilibrium, or characterized by strong gradients. To better understand ion transport in a partially magnetized system, we study the hydrodynamic velocity and temperature evolution in an ultracold neutral plasma at intermediate values of the magnetic field. We observe a transverse, radial breathing mode that does not couple to the longitudinal velocity. The inhomogeneous density distribution gives rise to a shear velocity gradient that appears to be only weakly damped. This mode is excited by ion oscillations originating in the wings of the distribution where the plasma becomes non-neutral. The ion temperature shows evidence of an enhanced electron-ion collision rate in the presence of the magnetic field. Ultracold neutral plasmas provide a rich system for studying mode excitation and decay.
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Affiliation(s)
- Chanhyun Pak
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Virginia Billings
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Matthew Schlitters
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Scott D Bergeson
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Michael S Murillo
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
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Sprenkle RT, Silvestri LG, Murillo MS, Bergeson SD. Temperature relaxation in strongly-coupled binary ionic mixtures. Nat Commun 2022; 13:15. [PMID: 35013203 PMCID: PMC8748956 DOI: 10.1038/s41467-021-27696-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 12/02/2021] [Indexed: 11/09/2022] Open
Abstract
New facilities such as the National Ignition Facility and the Linac Coherent Light Source have pushed the frontiers of high energy-density matter. These facilities offer unprecedented opportunities for exploring extreme states of matter, ranging from cryogenic solid-state systems to hot, dense plasmas, with applications to inertial-confinement fusion and astrophysics. However, significant gaps in our understanding of material properties in these rapidly evolving systems still persist. In particular, non-equilibrium transport properties of strongly-coupled Coulomb systems remain an open question. Here, we study ion-ion temperature relaxation in a binary mixture, exploiting a recently-developed dual-species ultracold neutral plasma. We compare measured relaxation rates with atomistic simulations and a range of popular theories. Our work validates the assumptions and capabilities of the simulations and invalidates theoretical models in this regime. This work illustrates an approach for precision determinations of detailed material properties in Coulomb mixtures across a wide range of conditions.
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Affiliation(s)
- R Tucker Sprenkle
- Department of Physics and Astronomy, Brigham Young University, Provo, UT, 84602, USA
- Honeywell Quantum Solutions, 303 S Technology Ct, Broomfield, CO, 80021, USA
| | - L G Silvestri
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, MI, 48824, USA
| | - M S Murillo
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, MI, 48824, USA.
| | - S D Bergeson
- Department of Physics and Astronomy, Brigham Young University, Provo, UT, 84602, USA.
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Sprenkle T, Dodson A, McKnight Q, Spencer R, Bergeson S, Diaw A, Murillo MS. Ion friction at small values of the Coulomb logarithm. Phys Rev E 2019; 99:053206. [PMID: 31212549 DOI: 10.1103/physreve.99.053206] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Indexed: 11/07/2022]
Abstract
Transport properties of high-energy-density plasmas are influenced by the ion collision rate. Traditionally, this rate involves the Coulomb logarithm, lnΛ. Typical values of lnΛ are ≈10-20 in kinetic theories where transport properties are dominated by weak-scattering events caused by long-range forces. The validity of these theories breaks down for strongly coupled plasmas, when lnΛ is of order one. We present measurements and simulations of collision data in strongly coupled plasmas when lnΛ is small. Experiments are carried out in the first dual-species ultracold neutral plasma (UNP), using Ca^{+} and Yb^{+} ions. We find strong collisional coupling between the different ion species in the bulk of the plasma. We simulate the plasma using a two-species fluid code that includes Coulomb logarithms derived from either a screened Coulomb potential or a the potential of mean force. We find generally good agreement between the experimental measurements and the simulations. With some improvements, the mixed Ca^{+} and Yb^{+} dual-species UNP will be a promising platform for testing theoretical expressions for lnΛ and collision cross-sections from kinetic theories through measurements of energy relaxation, stopping power, two-stream instabilities, and the evolution of sculpted distribution functions in an idealized environment in which the initial temperatures, densities, and charge states are accurately known.
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Affiliation(s)
- Tucker Sprenkle
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Adam Dodson
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Quinton McKnight
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Ross Spencer
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Scott Bergeson
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Abdourahmane Diaw
- Computational Physics and Methods Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
| | - Michael S Murillo
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
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Bergeson S. Really cool neutral plasmas. Science 2019; 363:33-34. [DOI: 10.1126/science.aau7988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Properties of laser-cooled neutral plasmas can be used to model high–energy-density plasmas
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Affiliation(s)
- Scott Bergeson
- Department of Physics and Astronomy, Brigham Young University, Provo, UT 84602, USA
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Lyon M, Rolston SL. Ultracold neutral plasmas. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:017001. [PMID: 27852983 DOI: 10.1088/0034-4885/80/1/017001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
By photoionizing samples of laser-cooled atoms with laser light tuned just above the ionization limit, plasmas can be created with electron and ion temperatures below 10 K. These ultracold neutral plasmas have extended the temperature bounds of plasma physics by two orders of magnitude. Table-top experiments, using many of the tools from atomic physics, allow for the study of plasma phenomena in this new regime with independent control over the density and temperature of the plasma through the excitation process. Characteristic of these systems is an inhomogeneous density profile, inherited from the density distribution of the laser-cooled neutral atom sample. Most work has dealt with unconfined plasmas in vacuum, which expand outward at velocities of order 100 m/s, governed by electron pressure, and with lifetimes of order 100 μs, limited by stray electric fields. Using detection of charged particles and optical detection techniques, a wide variety of properties and phenomena have been observed, including expansion dynamics, collective excitations in both the electrons and ions, and collisional properties. Through three-body recombination collisions, the plasmas rapidly form Rydberg atoms, and clouds of cold Rydberg atoms have been observed to spontaneously avalanche ionize to form plasmas. Of particular interest is the possibility of the formation of strongly coupled plasmas, where Coulomb forces dominate thermal motion and correlations become important. The strongest impediment to strong coupling is disorder-induced heating, a process in which Coulomb energy from an initially disordered sample is converted into thermal energy. This restricts electrons to a weakly coupled regime and leaves the ions barely within the strongly coupled regime. This review will give an overview of the field of ultracold neutral plasmas, from its inception in 1999 to current work, including efforts to increase strong coupling and effects on plasma properties due to strong coupling.
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Affiliation(s)
- M Lyon
- Joint Quantum Institute, University of Maryland, College Park and NIST, College Park, MD 20742, USA
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Murphy D, Sparkes BM. Disorder-induced heating of ultracold neutral plasmas created from atoms in partially filled optical lattices. Phys Rev E 2016; 94:021201. [PMID: 27627236 DOI: 10.1103/physreve.94.021201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Indexed: 11/07/2022]
Abstract
We quantify the disorder-induced heating (DIH) of ultracold neutral plasmas (UCNPs) created from cold atoms in optical lattices with partial filling fractions, using a conservation of energy model involving the spatial correlations of the initial state and the equation of state in thermal equilibrium for a one-component plasma. We show, for experimentally achievable filling fractions, that the ionic Coulomb coupling parameter could be increased to a degree comparable to other proposed DIH-mitigation schemes. Molecular dynamics simulations were performed with compensation for finite-size and periodic boundary effects, which agree with calculations using the model. Reduction of DIH using optical lattices will allow for the study of strongly coupled plasma physics using low-density, low-temperature, laboratory-based plasmas, and lead to improved brightness in UCNP-based cold electron and ion beams, where DIH is otherwise a fundamental limitation to beam focal sizes and diffraction imaging capability.
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Affiliation(s)
- D Murphy
- School of Physics, The University of Melbourne, Victoria 3010, Australia
| | - B M Sparkes
- School of Physics, The University of Melbourne, Victoria 3010, Australia
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