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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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Bronin SY, Vikhrov EV, Zelener BB, Zelener BV. Ultracold plasma expansion in quadrupole magnetic field. Phys Rev E 2023; 108:045209. [PMID: 37978663 DOI: 10.1103/physreve.108.045209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 10/04/2023] [Indexed: 11/19/2023]
Abstract
We present simulation results of ultracold Sr plasma expansion in a quadrupole magnetic field by means of molecular dynamics. An analysis of plasma evolution influenced by a magnetic field is given. Plasma confinement time behavior under variation of magnetic field strength is estimated. Similarity of the time dependence of the concentration and distribution of ion velocities against the parameters of the plasma and magnetic field is established. Simulation results are in agreement with the experimental ones.
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Affiliation(s)
- S Ya Bronin
- Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya Street 13, Building 2, Moscow 125412, Russia
| | - E V Vikhrov
- Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya Street 13, Building 2, Moscow 125412, Russia
| | - B B Zelener
- Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya Street 13, Building 2, Moscow 125412, Russia
| | - B V Zelener
- Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya Street 13, Building 2, Moscow 125412, Russia
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Dong C, Hu W, Li D, Zhang W. Impact of magnetic field on the parallel resistivity. Phys Rev E 2022; 105:055204. [PMID: 35706199 DOI: 10.1103/physreve.105.055204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 04/22/2022] [Indexed: 06/15/2023]
Abstract
The impact of magnetic field (MF) on the parallel resistivity η_{∥} is studied for strongly magnetized plasmas with the electron thermal gyroradius ρ_{the} smaller than the Debye length λ_{D} but much larger than the Landau length λ_{L}. Two previous papers [P. Ghendrih et al., Phys. Lett. A 119, 354 (1987)10.1016/0375-9601(87)90614-1; S. D. Baalrud and T. Lafleur, Phys. Plasmas 28, 102107 (2021)10.1063/5.0054113] found η_{∥} to increase monotonically with MF. Unfortunately, both works used predetermined electron distribution functions and are thus not self-consistent. In this paper, we analyze the MF dependence of η_{∥} self-consistently by solving the electron magnetized kinetic equation in a Lorentz gaslike approximation. It is found η_{∥} decreases monotonically with MF, with λ_{D} in the usual Coulomb logarithm lnΛ=ln(λ_{D}/λ_{L}) being replaced by ρ_{the}. The underlying physics is that the electrons affected only by the collisions with impact parameters between λ_{L} and ρ_{the} carry almost all the parallel current.
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Affiliation(s)
- Chao Dong
- Beijing National Laboratory for Condensed Matter Physics and Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wei Hu
- Institute of Optoelectronic Technology, Lishui University, Lishui 323000, China
| | - Ding Li
- Beijing National Laboratory for Condensed Matter Physics and Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Wenlu Zhang
- Beijing National Laboratory for Condensed Matter Physics and Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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Sprenkle RT, Bergeson SD, Silvestri LG, Murillo MS. Ultracold neutral plasma expansion in a strong uniform magnetic field. Phys Rev E 2022; 105:045201. [PMID: 35590663 DOI: 10.1103/physreve.105.045201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 02/16/2022] [Indexed: 06/15/2023]
Abstract
In strongly magnetized neutral plasmas, electron motion is reduced perpendicular to the magnetic field direction. This changes dynamical plasma properties such as temperature equilibration, spatial density evolution, electron pressure, and thermal and electrical conductivity. In this paper we report measurements of free plasma expansion in the presence of a strong magnetic field. We image laser-induced fluorescence from an ultracold neutral Ca^{+} plasma to map the plasma size as a function of time for a range of magnetic field strengths. The asymptotic expansion velocity perpendicular to the magnetic field direction falls rapidly with increasing magnetic field strength. We observe that the initially Gaussian spatial distribution remains Gaussian throughout the expansion in both the parallel and perpendicular directions. We compare these observations with a diffusion model and with a self-similar expansion model and show that neither of these models reproduces the observed behavior over the entire range of magnetic fields used in this study. Modeling the expansion of a magnetized ultracold plasma poses a nontrivial theoretical challenge.
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Affiliation(s)
- R Tucker Sprenkle
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - S D Bergeson
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Luciano G Silvestri
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
| | - Michael S Murillo
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
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Gorman GM, Warrens MK, Bradshaw SJ, Killian TC. Magnetic Confinement of an Ultracold Neutral Plasma. PHYSICAL REVIEW LETTERS 2021; 126:085002. [PMID: 33709740 DOI: 10.1103/physrevlett.126.085002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 01/05/2021] [Accepted: 01/22/2021] [Indexed: 06/12/2023]
Abstract
We demonstrate magnetic confinement of an ultracold neutral plasma (UCNP) created at the null of a biconic cusp, or quadrupole magnetic field. Initially, the UCNP expands due to electron thermal pressure. As the plasma encounters stronger fields, expansion slows and the density distribution molds to the field. UCNP electrons are strongly magnetized over most of the plasma, while ion magnetization is only significant at the boundaries. Observations suggest that electrons and ions are predominantly trapped by magnetic mirroring and ambipolar electric fields, respectively. Confinement times approach 0.5 ms, while unmagnetized plasmas dissipate on a timescale of a few tens of microseconds.
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Affiliation(s)
- G M Gorman
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - M K Warrens
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - S J Bradshaw
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - T C Killian
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
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Scheiner B, Baalrud SD. Viscosity of the magnetized strongly coupled one-component plasma. Phys Rev E 2021; 102:063202. [PMID: 33466065 DOI: 10.1103/physreve.102.063202] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 11/10/2020] [Indexed: 11/07/2022]
Abstract
The viscosity tensor of the magnetized one-component plasma, consisting of five independent shear viscosity coefficients, a bulk viscosity coefficient, and a cross coefficient, is computed using equilibrium molecular dynamics simulations and the Green-Kubo relations. A broad range of Coulomb coupling and magnetization strength conditions are studied. Magnetization is found to strongly influence the shear viscosity coefficients when the gyrofrequency exceeds the Coulomb collision frequency. Three regimes are identified as the Coulomb coupling strength and magnetization strength are varied. The Green-Kubo relations are used to separate kinetic and potential energy contributions to each viscosity coefficient, showing how each contribution depends upon the magnetization strength. The shear viscosity coefficient associated with the component of the pressure tensor parallel to the magnetic field, and the two coefficients associated with the component perpendicular to the magnetic field, are all found to merge to a common value at strong Coulomb coupling.
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Affiliation(s)
- Brett Scheiner
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Scott D Baalrud
- Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA
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Sánchez-Arriaga G, Zhou J, Ahedo E, Martínez-Sánchez M, Ramos JJ. Kinetic features and non-stationary electron trapping in paraxial magnetic nozzles. ACTA ACUST UNITED AC 2018. [DOI: 10.1088/1361-6595/aaad7f] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Baalrud SD, Daligault J. Transport regimes spanning magnetization-coupling phase space. Phys Rev E 2017; 96:043202. [PMID: 29347622 DOI: 10.1103/physreve.96.043202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Indexed: 06/07/2023]
Abstract
The manner in which transport properties vary over the entire parameter-space of coupling and magnetization strength is explored. Four regimes are identified based on the relative size of the gyroradius compared to other fundamental length scales: the collision mean free path, Debye length, distance of closest approach, and interparticle spacing. Molecular dynamics simulations of self-diffusion and temperature anisotropy relaxation spanning the parameter space are found to agree well with the predicted boundaries. Comparison with existing theories reveals regimes where they succeed, where they fail, and where no theory has yet been developed.
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Affiliation(s)
- Scott D Baalrud
- Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA
| | - Jérôme Daligault
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, 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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Zhang XL, Fletcher RS, Rolston SL. Observation of an ultracold plasma instability. PHYSICAL REVIEW LETTERS 2008; 101:195002. [PMID: 19113277 DOI: 10.1103/physrevlett.101.195002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Indexed: 05/27/2023]
Abstract
We present the first observation of an instability in an expanding ultracold plasma. We observe periodic emission of electrons from an ultracold plasma in weak, crossed magnetic and electric fields, and a strongly perturbed electron density distribution in electron time-of-flight projection images. We identify this instability as a high-frequency electron drift instability due to the coupling between the electron drift wave and electron cyclotron harmonic, which has large wave numbers corresponding to wavelengths close to the electron gyroradius.
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Affiliation(s)
- X L Zhang
- Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
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