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Events During the Week of February 25th through March 3rd, 2024

Monday, February 26th, 2024

Plasma Physics (Physics/ECE/NE 922) Seminar
"From the laboratory to astrophysics: the Rayleigh-Taylor instability"
Time: 12:00 pm - 1:15 pm
Place: 1227 Engineering Hall
Speaker: Dr. Bhuvana Srinivasan, Director, PLASMAWISE Laboratory - Univ of Washington
Abstract: Recent breakthroughs in inertial confinement fusion have demonstrated fusion ignition, but significant physics and engineering challenges remain to truly achieve energy breakeven. Hydrodynamic mix at material interfaces is known to be detrimental for laser-driven and pulsed-power-driven inertial confinement fusion implosions. Hence, mitigation of mix remains an open challenge. The Rayleigh-Taylor instability (RTI), which occurs when the interface between two fluids with different densities is accelerated, has been known to play a critical role in producing hydrodynamic mix at material interfaces. The RTI is an ubiquitous instability and RTI-like features and growth have been noted in astrophysical observations. The presence of magnetic fields, plasma transport, and kinetic effects can significantly alter the evolution of the RTI, which may explain discrepancies between numerical simulations and observations. These will be discussed in this talk. Other high-energy-density research relevant to pulsed-power implosions such as the growth of the electrothermal instability that can seed the late-time RTI will be discussed briefly. There is a need for high-fidelity computational models to study high-energy-density plasmas. A hierarchy of models, ranging from magnetohydrodynamic (MHD) to fully kinetic, are developed and applied across a wide range of parameter regimes in the PLASMAWISE laboratory at the University of Washington.

Bio: Bhuvana Srinivasan is an Associate Professor in the William E. Boeing Department of Aeronautics and Astronautics at the University of Washington. Prior to this appointment, she was an Associate Professor in the Kevin T. Crofton Department of Aerospace and Ocean Engineering at Virginia Tech where she developed a program in computational plasma physics. Prior to joining Virginia Tech, she was a postdoc and a scientist at the Los Alamos National Laboratory. She is the director of the PLASMAWISE Laboratory (previously the Plasma Dynamics Computational Laboratory at Virginia Tech). The primary research areas in her group include plasma-material interactions in thrusters and fusion devices, instabilities in high-energy-density fusion and astrophysical plasmas, ionospheric plasma instabilities, and numerical algorithm development for fluid and kinetic models. She is a recipient of the NSF CAREER award, the 2017 Outstanding Assistant Professor award and the 2019 Faculty Fellow awarded by the Dean of the College of Engineering at Virginia Tech. She was appointed to the Endowed Crofton Faculty Fellowship in Engineering from 2021-2023. She is a member of the Fusion Energy Sciences Advisory Committee to the U.S. Department of Energy and serves on the Executive Committee for the American Physical Society Division of Plasma Physics. She is also active in Diversity, Equity, and Inclusion (DEI) efforts as the past Chair of the DEI committee in the aerospace and ocean engineering department at Virginia Tech, as a member of the Committee on Women+ in Plasma Physics, and through her involvement with the Center for the Enhancement of Engineering Diversity at Virginia Tech.
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Plasma Seminar
Highlights from the path toward confined e+e- pair plasmas
Time: 3:30 pm - 4:30 pm
Place: B343 Sterling Hall
Speaker: Eve Stenson, Max Planck Institute for Plasma Physics
Abstract: The grand challenge being pursued by the APEX (A Positron Electron eXperiment) Collaboration is to create and study cold, confined, strongly magnetized, matter-antimatter “pair plasmas” in the laboratory. This unusually simple, symmetric type of plasma has been the subject of theory/simulation predictions going back over four decades; we would like to test some of these experimentally. Our path to pair plasmas involves joining together and further developing state-of-the-art physics and engineering in several disciplines. This talk will give an overview of recent highlights ---including novel techniques in the areas of positron beams, non-neutral plasmas, and gamma diagnostics --- as well as the progress on our two, complementary, tabletop-sized, pair-plasma traps: a levitated dipole and an optimized stellarator, both based on small, non-insulated, HTS (high-temperature superconducting) coils. Finally, I will outline plans for the few next year(s), during which we will continue to assemble the pieces of the pair plasma "puzzle", and beyond.
Host: Jan Egedal
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Tuesday, February 27th, 2024

Wisconsin Quantum Institute
Quantum Coffee Hour
Time: 3:00 pm - 4:00 pm
Place: Rm.5294, Chamberlin Hall
Abstract: Please join us for the WQI Quantum Coffee today at 3PM in the Physics Faculty Lounge (Rm.5294 in Chamberlin Hall). This series, which takes place approximately every other Tuesday, aims to foster a casual and collaborative atmosphere where faculty, post-docs, students, and anyone with an interest in quantum information sciences can come together. There will be coffee and treats.
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Wednesday, February 28th, 2024

Theory Seminar (High Energy/Cosmology)
Effective Field Theory Approach to Physics Beyond the Standard Model
Time: 4:00 pm - 5:00 pm
Place: 5280 Chamberlin Hall
Speaker: Xiaochuan Lu, UC San Diego
Abstract: Effective Field Theories (EFTs) are widely applied in particle physics of and beyond the Standard Model. They also serve as the foundation to understand renormalizations in Quantum Field Theories. In this talk, I will discuss a few crucial aspects of EFTs, including how to define EFTs, how to apply EFTs, and how to handle field redefinitions in EFTs. Modern technologies involved are the Hilbert series method, functional matching with covariant derivative expansion, and geometric formulation of EFTs. I will explain the key ideas of these technologies, and how they facilitate the phenomenological studies in high energy physics.
Host: Lisa Everett
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Thursday, February 29th, 2024

Plasma Seminar
Investigations of fundamental Alfvénic Wave Physics
Time: 1:00 pm - 2:00 pm
Place: B343 Sterling Hall
Speaker: Seth Dorfman, Space Science Institute
Abstract: nvestigations of fundamental Alfvénic wave physics in the laboratory and in space Low frequency Alfvénic waves and fluctuations are ubiquitous in laboratory and space plasmas, and these fundamental modes of a magnetized plasma often serve as building blocks for more complicated structures and dynamics. The linear and non-linear properties of these waves may play key roles in the turbulent solar wind, heating of the solar corona, and the environment near the Earth's bow shock. In this seminar, I will present a vision for how laboratory and spacecraft studies focused on these fundamental building blocks can help us develop a more complete picture of important space physics phenomena. Our recent work on the Large Plasma Device at UCLA successfully isolated important non-linear Alfvénic phenomena that may be building blocks of the turbulent solar wind [e.g., Dorfman and Carter, PRL 2016]. Recent results include a proof-of-principle measurement of the Parametric Decay Instability (PDI) growth rate [Dorfman, et. al, in prep]; PDI has been previously shown to bound the solar wind parameter space. We also recorded the first observation of residual energy in a non-linear Alfvén wave interaction [Abler, et. al, in prep]; this is important because residual energy is observed in the inertial range of the turbulent cascade (i.e. there is more energy in the magnetic than the velocity fluctuations), but an MHD Alfvén wave has equal amounts of energy in fluctuations of each type. On the spacecraft study side, I will introduce the Earth's ion foreshock as a natural laboratory for wave studies and show a new method to detect the foreshock edge that also has wide implications for the interpretation of minimum variance techniques commonly used to determine wave properties [Dorfman, et. al, 2023]. After examining these various examples, I will discuss the prospects of a new Solar Wind Machine aimed at producing magnetized plasma turbulence in the laboratory for detailed study to complement and extend spacecraft observations [Dorfman, et. al, Heliophysics Decadal White Paper 2022]. You are invited to join us on April 18-20 for a workshop to refine physics targets and develop candidate machine designs:
Host: Jan Egedal
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
New probes of ultrahigh energy cosmic ray source evolution
Time: 2:30 pm - 3:30 pm
Place: Supernova @WIPAC
Speaker: Marco Muzio, Penn State University
Abstract: Despite first observing cosmic rays with energies above an EeV (10^18 eV) in the 1960s, the source of these particles remains an open question. Modern observatories, in particular the Pierre Auger Observatory and Telescope Array, have firmly established that the cosmic ray spectrum continues up to ~10^20.3 eV and have significantly advanced our understanding of these particles. However, limited statistics, uncertainties in particle physics, and significant deflections in the Galactic magnetic field have made progress towards discovering their astrophysical source extremely challenging. One key astrophysical input needed to understand ultrahigh energy cosmic ray data is the distribution of their sources, or the source evolution. In this talk, I will focus on multimessenger observations which have the potential to pin down the source evolution for the very first time.
Host: Lu Lu
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Astronomy Colloquium
Exploring the diversity of H2-H2O subNeptunes
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Raymond T. Pierrehumbert, University of Oxford
Abstract: Astronomical observations directly probe the properties of only the outer portions of a planet's atmosphere. When both mass and radius observations are available, the resulting mean density provides further, though highly degenerate, constraints on the composition of the interior. In this talk, I will discuss the kinds of inferences that can be drawn when the two kinds of information are put together. The emphasis will be on planets whose fluid layer is composed of H2 and H2O with various proportions, potentially interacting with a silicate core. An important physical consideration constraining plausible interior structures is that for liquid water interiors, the solubility of H2 is constrained by Henry's Law solubility, whereas for supercritical water interiors H2 (and other gases) are completely miscible with the interior. We will discuss the range of possible H2:H2O ratios in the outer atmosphere that can be compatible with a supercritical water atmosphere. Although an H2 layer is miscible with a supercritical water interior, there is a stable density jump at the interface, which inhibits mixing between the two layers; an essential missing piece of the puzzle is the quantification of the rate of such mixing. Once mixing begins, the moistening of the H2 layer leads to additional phenomena, including both water vapour feedback and generation of steep radiative layers near the interface through compositional stabilization of the lower atmosphere. I will also discuss thermal evolution models and implications of interaction of the H2:H2O fluid layer with a basal magma ocean. K2-18b and GJ1214b will be used as the archetypes of two very different types of subNeptunes, but I will also discuss results from a recent JWST survey of subNeptunes selected to have densities compatible with a potentially H2O-rich composition.
Host: Ke Zhang
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Friday, March 1st, 2024

Graduate Program Event
Prospective Visit Days
Time: 8:30 am
Place: all over Chamberlin
Speaker: various
Abstract: This weekend, we'll host several prospective PhD student visitors to the department. Please welcome them as you see them around Chamberlin!
Host: Sharon Kahn
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Physics Department Colloquium
Quantum engineering for superconducting quantum computers
Time: 3:30 pm - 6:00 pm
Place: 2241 Chamberlin Hall
Speaker: Prof. Yasunobu Nakamura , University of Tokyo
Abstract: The motivation for observing quantum superposition in macroscopic systems guided us to the research of superconducting quantum circuits and the realization of superconducting qubits. The qubit itself is a many-body system of interacting electrons designed and fabricated in the form of an electrical circuit, where quantized energy levels of a collective excitation mode are used as the bases for storing and manipulating quantum information. With the strong nonlinearity due to the Josephson effect and the large dipole moments that allow fast control and readout of the quantum states, superconducting qubits comprise versatile platforms for quantum information processing. Now, having accumulated knowledge and technology, we are facing new challenges in constructing an artificial quantum system with a macroscopic number of qubits and controlling them precisely. We will discuss our approach at RIKEN.
Host: Robert McDermott
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