Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session PO07: Fundamental Plasmas: Waves, Oscillations, InstabilitiesLive Streamed
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Chair: Stephen Vincena, UCLA Room: 401 ABC |
Wednesday, October 19, 2022 2:00PM - 2:12PM |
PO07.00001: Ion cyclotron emission by a spiraling proton beam on the Large Plasma Device Shreekrishna Tripathi, Bart G Van Compernolle, Stephen T Vincena, Walter N Gekelman, Troy Carter, Patrick Pribyl, Yhoshua Wug, William W Heidbrink Resonant interaction between energetic-ions and plasma waves is a fundamental topic of importance in space and laboratory plasma physics. We report results on the ion cyclotron emission (ICE) by a spiraling proton beam (5-15 keV, 10 A) in a linear magnetized plasma (n ≈ 1010 – 1013 cm-3, Te ≈ 5.0-15.0 eV, B = 0.6–1.8 kG, He+ and H+ ions, 19 m long, 0.6 m diameter) on the Large Plasma Device (LAPD). The ICE appears as a sequence of narrow frequency peaks extending up to 150th harmonics of the beam gyro-frequency. These peaks are accompanied by a broad continuum around the lower-hybrid frequency. In this experiment, the proton beam forms a helical orbit (pitch-angle ≈ 7°–55°) and propagates with an Alfvénic speed (beam-speed/Alfvén-speed = 0.2–3.0). The role of resonant processes in destabilizing these waves were examined by recording the mode-structure of these waves and relevant parameters of plasma using a variety of diagnostic tools (retarding-field energy analyzer, three-axis magnetic-loop, Dipole, and Langmuir probes). Our results suggest that ICE on LAPD are electrostatic-beam modes associated with long parallel wavelengths and destabilized by Doppler-shifted cyclotron resonance with the beam. |
Wednesday, October 19, 2022 2:12PM - 2:24PM |
PO07.00002: Exploration of Propagation Window for Ion Acoustic Waves in Multi-cusp Plasma Device Meenakshee Sharma, Prabhakar Srivastav, A. D. Patel, N. Ramasubramanian, Y. C. Saxena The Multi-pole line cusp Plasma Device (MPD) has adopted cusp magnetic field geometry produced using six electromagnets for plasma confinement. The variation in cusp magnetic field strength gives us the opportunity to explore the propagating and non-propagating regimes for the ion-acoustic (IA) wave. |
Wednesday, October 19, 2022 2:24PM - 2:36PM |
PO07.00003: Topological Edge States in Tunable Bulk Gyrotropic Media Composed of Magnetized Low-Temperature Plasma Discharges Jesse A Rodriguez, Luc Houriez, Hossein Mehrpour-Bernety, Mark A Cappelli Gyrotropic media exhibit several interesting electromagnetic properties, including topologically protected edge states that allow for one-way, back-scattering immune propagation of interfacial electromagnetic waves. Unfortunately, such media are challenging to create for engineering applications since the use of ferromagnetic (gyrotropic) materials limit the range of operating frequencies and a homogeneous bulk magnetized plasma is difficult to produce in practice. In this presentation, we show how a tunable bulk gyrotropic medium can be constructed using magnetized low-temperature plasma discharge tubes in a two-dimensional photonic crystal configuration. Experiments are performed for microwave frequencies in the range of 2-10 GHz. Band structures for both the magnetized and unmagnetized case are compared and confirmed via experimental transmission measurements and numerical simulations of the actual device. Evidence for topologically-protected edge states from local field measurements is presented. |
Wednesday, October 19, 2022 2:36PM - 2:48PM |
PO07.00004: Spectral analysis of current-driven instabilities relevant to anomalous transport in hollow cathode plumes Wai Hong Ronald Chan, Kentaro Hara, Jonathan M Wang, Suhas S Jain, Kevin P Griffin, Iain D Boyd Large-scale current-driven instabilities in plasma plumes can generate energetic ions responsible for sputtering and subsequent degradation of hollow cathodes. While fluid and hybrid plasma simulations have been used to model these plasmas with the aid of model coefficients for anomalous transport, thorough investigation of high-energy ion formation requires a fully kinetic solver. A 2D2V grid-based Vlasov-Poisson (direct kinetic) solver is used to study the transient characteristics and nonlinear saturation of these instabilities over a range of initial electron Mach numbers. The degree to which recently developed nonuniform grid capabilities can reduce computational cost while preserving accuracy in quantities of interest is explored. Physical aspects and spectral characteristics of the growth process are analyzed for a variety of initial perturbations to determine the sensitivity of turbulence generation and energetic ion formation to initial conditions. This multidimensional study sheds light on the effects of a transverse density gradient on longitudinal plasma instabilities. |
Wednesday, October 19, 2022 2:48PM - 3:00PM |
PO07.00005: Nontrivial topological low-frequency waves at the boundary of magnetized plasmas Roopendra Singh Rajawat, Tianhong Wang, Gennady Shvets The topological properties of a magnetized cold gaseous plasma have recently been explored and the existence of a topologically protected edge states have been established [1,2,3]. These studies are limited to a magnetized plasma, where ions are infinitely massive and provide a neutralizing background. When ion motion is included, a new class of low-frequency unidirectional topological waves emerges in the dispersion relation. The group velocity of these waves is in opposite direction of high frequency topological electron waves for a given magnetic field direction. The Berry curvature and Chern numbers are calculated to establish non-trivial topological phase. A theoretical model is developed for very small inhomogeneity scale lengths to calculate the band-spectrum and establish the existence of an edge mode. It is also presented that if a continuous wave spectrum exists at the boundary of a magnetized plasma, these low-frequency topological waves undergo collisionless damping due to coupling with lower-hybrid resonance, consequently resulting into heating of a plasma. We also demonstrate by ab-initio 3D particle-in-cell simulations that edge states, undergoing collisionless damping, are robust, unidirectional, and topologically protected. These finding broadens the possible applications of these exotic excitations in space and laboratory plasmas. |
Wednesday, October 19, 2022 3:00PM - 3:12PM |
PO07.00006: Frequency-resolved local measurements of phase-space energization Emily R Lichko, James L Juno, Sarah A Horvath, Gregory G Howes, Mel Abler, Kristopher G Klein In order to disentangle the competing kinetic-scale energy dissipation processes that are intrinsic to space and astrophysical plasmas it is critical to be able to diagnose the energy transfer that is occurring locally in both time and space. A relatively recent technique to resolve the local rate of energy transfer between the fields and particles is the field-particle correlation (Klein & Howes APJL 2016), which has resolved local energy transfer at a single point in space for a large variety of systems and physical processes. This work details an updated version of the field-particle correlation that includes for the first time a breakdown of the energy transfer in frequency space, as well as time and velocity space. In addition to the increase in available information, this new method more cleanly separates magnitude and phase information of the signal, resulting in an improvement of the temporal resolution. This new method is applied to Gkeyll simulations of electron Landau damping as a proof of concept, as well as a high-resolution gyrokinetic simulation of space plasma turbulence performed using AstroGK. |
Wednesday, October 19, 2022 3:12PM - 3:24PM |
PO07.00007: Non-linear evolution of the current filamentation instability on ion time scales Cinzia Chiappetta, Maria Elena Innocenti, Kevin M. Schoeffler, Nitin Shukla, Elisabetta Boella The current filamentation instability (CFI) is a plasma microinstability believed to be responsible for magnetic field generation in many astrophysical environments, such as gamma-ray bursts, supernova remnants and active galactic nuclei. The instability is also relevant in laboratory settings, where it is triggered in the presence of counterstreaming plasma flows and produces intense fields of the order of 106 Gauss. |
Wednesday, October 19, 2022 3:24PM - 3:36PM |
PO07.00008: Multimode theory of electron hole instability Ian Hutchinson, Xiang Chen We analyze 3-D Vlasov-Poisson instabilities, which limit final shape |
Wednesday, October 19, 2022 3:36PM - 3:48PM |
PO07.00009: Enhancement of the non-linear frequency shift due to electron-electron collisions Archis S Joglekar, Roman Lee, Warren B Mori, Alexander G Thomas, Bedros B Afeyan During the evolution of a weakly-collisional non-linear electron plasma, an enhancement of the non-linear frequency shift is observed in kinetic simulations. Theory and simulations of damping due to electron-electron collisions modeled using a Fokker-Planck operator show that the wave damps weakly for a range of physically relevant parameters. By performing perturbative expansions on the kinetic dispersion relation in frequency, time, and velocity, we show that the growth rate of the frequency is directly proportional to the damping rate of the electric field amplitude. A relation for the complex non-linear frequency of quasi-steady-state, weakly-collisional, non-linear electron plasma waves is provided. |
Wednesday, October 19, 2022 3:48PM - 4:00PM |
PO07.00010: Wave breaking through phase mixing of a variant of Lower Hybrid Modes in cold electron-ion plasma Mithun Karmakar, Sourav Pramanik, Chandan Maity The wave breaking through a process called phase mixing of low frequency |
Wednesday, October 19, 2022 4:00PM - 4:12PM |
PO07.00011: The Quantum Three Wave Instability Michael Q May, Hong Qin The three wave interaction, the lowest order nonlinear interaction in plasma physics, has both a well-known classical description [1] and a recently investigated quantum description [2]; however, the relationship between these descriptions has not been fully investigated. The classical three wave interaction is subject to a parametric linear instability which would initially seem at odds with a quantum description. The present work describes how a time-independent finite-dimensional quantum system, which is Hermitian with all real eigenvalues, can give rise to a linear instability in the corresponding classical system. It is found that the distribution of eigenvalues in the quantum description of the classically unstable system has a richer spectrum than for the quantum description of the classically stable system, and the instability is realized in the quantum regime as a cascade of probability from higher to lower probability states. Finally, the nonlinear regime of classical instability is compared with the corresponding quantum regime, and the conditions for quantum instability are described. |
Wednesday, October 19, 2022 4:12PM - 4:24PM |
PO07.00012: Wave-Driven Torques in Fluid and Oscillation Center Theories Ian E Ochs, Nathaniel Fisch The evaluation of ExB rotation drive by waves in laboratory plasmas requires calculating the torques induced by the waves. Such calculations are plagued with subtleties, and ensuring the self-consistency (and particularly momentum conservation) of the underlying theory is paramount to obtaining correct results. Recently, using a theory that treated nonresonant particles as a fluid and resonant particles kinetically, it was shown that there was an important difference between quasi-electrostatic plane waves which grow or decay in time, which do not apply a torque, and spatially structured waves, which do [1-3]. However, there are other, completely different approaches to calculating ponderomotive forces, which focus on the motion of the oscillation center, and which have their own momentum and energy conservation theorems. Thus, both theories should lead to the same conclusions—though this turns out to be far from straightforward to show. Here, we discuss the relationship between the two types of theory, showing the different subtleties that affect each in practical calculations, and demonstrate how the two theories can ultimately be shown to agree. |
Wednesday, October 19, 2022 4:24PM - 4:36PM |
PO07.00013: Modeling experiments that probe beam spray thresholds in ICF-relevant plasmas Thomas D Chapman, David Turnbull, Michail Belyaev, Richard L Berger, Mark Sherlock Recent experiments at the Omega Laser Facility (D. Turnbull et al., accepted by Physical Review Letters) have carefully studied the spraying of laser light as it propagates through underdense plasmas of relevance to inertial confinement fusion experiments. In these experiments, frequency redshits of the transmitted light were measured that exceed estimates based on the Dewandre shift caused by the plasma expansion alone. Such redshifts are a signature of forward Brillouin scattering. Here, these experiments are modeled using three-dimensional simulations that describe the necessary absorption, backscattering, filamentation, and forward scattering of the laser light. The phase plate of the experimental beam is reproduced numerically, allowing for a direct comparison with the experimentally measured transmitted beam spot and frequency. |
Wednesday, October 19, 2022 4:36PM - 4:48PM |
PO07.00014: Role of bandwidth in Two Plasmon decay instability Sonali Khanna, Ratul Sabui, Angana Mondal, Ram Gopal, M Krishnamurthy Laser plasma interaction is an all-encompassing source of high energy electrons, ions, and electromagnetic radiation ranging from THz to X-rays. Due to the small source size and high flux, the beam has potential applications in various contexts, from defence to medical physics and many other industries. To make the source viable for many applications, producing high energy electrons with high repetition rate lasers is essential. High repetition lasers have low energy, longer pulse width, and shorter bandwidth. Our recent studies have shown that structural modification of the target reduces two plasmon decay instability threshold and enhances electron acceleration to MeV energies even at an intensity of ~ 1016 W/cm2. In this work, we present the role of bandwidth on the emission of electrons studied by manipulating the chirp of the laser pulse for its potential use with MHz lasers. |
Wednesday, October 19, 2022 4:48PM - 5:00PM |
PO07.00015: Self-magnetization of CO2-produced plasmas by electron Weibel instability Chaojie Zhang, Yipeng Wu, Mitchell Sinclair, Audrey Farrell, Kenneth A Marsh, Irina Petrushina, Navid Vafaei-Najafabadi, Apurva Gaikwad, Rotem Kupfer, Karl Kusche, Mikhail Fedurin, Igor Pogorelsky, Mikhail Polyanskiy, Chen-Kang Huang, Jianfei Hua, Wei Lu, Warren B Mori, Chandrashekhar Joshi Weibel-type instability can self-generate and amplify magnetic fields in plasmas with anisotropic velocity distribution. Thermal Weibel instability driven by temperature anisotropy of a stationary plasma, as originally proposed by E. S. Weibel, has proven challenging to measure because of the difficulty in preparing such a distribution. Here we show that by using an ultrashort but intense CO2 laser to ionize hydrogen gas, one can prepare a plasma with tri-Maxwellian velocity distribution that is perfectly suitable for studying thermal electron Weibel instability. The onset, growth and damping of the magnetic fields are captured by a picosecond-long, relativistic electron probe bunch from a linear accelerator. We find that the magnetic fields start growing with a broad two-dimensional wavenumber spectrum, but as the instability grows, the spectrum shrinks to a quasi-single mode in both directions perpendicular to the probe direction. The k-resolved growth rates of the instability deduced agree with kinetic theory. It is also observed that Weibel instability amplifies the magnetic fields and converts up to ~1% of the plasma thermal energy into magnetic energy, which supports the hypothesis of spontaneous magnetization of collisionless astrophysical plasmas by Weibel instability. |
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