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Events During the Week of December 3rd through December 10th, 2023

Monday, December 4th, 2023

Plasma Physics (Physics/ECE/NE 922) Seminar
Dept of Energy Fusion Energy Sciences Town Hall
Time: 12:00 pm - 1:15 pm
Place: 1610 Engineering Hall
Speaker: Dr. Jean-Paul Allain, DOE Fusion Energy Sciences (FES) Associate Director
Questions for the upcoming FES Town Hall on Monday, December 4th at noon in room 1610 of Engineering Hall are being collected via this google form.

Please submit as many questions as you would like.

There will also be an opportunity to ask questions during the event.

Here's the link to the DOE announcement when Dr. Allain was announced as the new Associate Director:

Host: Prof. Steffi Diem
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Tuesday, December 5th, 2023

Council Meeting
Physics Council Meeting
Time: 3:00 pm - 4:00 pm
Place: 2314 Chamberlin Hall
Speaker: Mark Eriksson, UW - Madison
Host: Mark Eriksson
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Wednesday, December 6th, 2023

Department Meeting
Time: 12:15 pm - 1:00 pm
Place: B343 Sterling Hall
Speaker: Mark Eriksson, UW-Madison
agenda to come a day or so before the meeting.
Host: Mark Eriksson
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Graduate Program Event
Towards Measurement of Pressure Anisotropy during Collisionless Magnetic Reconnection
Time: 2:30 pm - 6:00 pm
Place: B343 Sterling or
Speaker: Cameron Kuchta, Physics PhD Graduate Student
Abstract: The Terrestrial Reconnection EXperiment (TREX) at the Wisconsin Plasma Physics Laboratory (WiPPL) studies collisionless magnetic reconnection [1]. We have developed a new Pressure Anisotropy (PA) probe consisting of 24 langmuir probes; 12 outer tips collect plasma isotropically while the remaining 12 inner tips are shielded and receive plasma directionally. This allows us to measure plasma flows and pressure anisotropy during reconnection. With recent upgrades to our experiment, we are now able to enter the collisionless kinetic regime of magnetic reconnection in which we expect electron anisotropy effects to dominate the physics in the ion diffusion region. This regime is relevant to reconnection in the magnetosphere. Embedded jets, seen in laboratory data, are driven into the outflow of reconnection as expected from spacecraft observation, theory, and simulations [2]. We have also observed signatures of pressure anisotropy with the PA probe. Current progress on probe design and analysis will be presented.

[1] Olson et al. PRL (2016) 116, 255001.Experimental Demonstration of the Collisionless Plasmoid Instability below the Ion Kinetic Scale during Magnetic Reconnection [2] Wetherton et al. JGR Space Physics (2021) 125, e2020JA028604.

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award Number DE-SC0018266 and DE-SC0020989. It is also based upon work supported by NASA under award No. 80NSSC22K0556.
Host: Jan Egedal
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Thursday, December 7th, 2023

R. G. Herb Condensed Matter Seminar
Inducing non-equilibrium phases in semiconductors with time-periodic drives
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Ilya Esin, Caltech
Abstract: “Floquet engineering” - designing band structures “on-demand" through an application of coherent time-periodic drives, has recently emerged as a powerful tool for inducing exotic phenomena in ordinary materials. In this talk, I will discuss the application of Floquet engineering for inducing novel non-equilibrium phases of matter in steady states of time-periodically driven semiconductors. The steady states are achieved due to the interplay between the coherent external drive, electron-electron interactions, and dissipative processes arising from the coupling to phonons and the electromagnetic environment. I will show that despite the highly non-equilibrium nature of these systems, by judicially choosing the properties of the material, the external drive, and the environments, their steady states can exhibit topological transport and strongly correlated phases such as a novel electronic liquid gyro-crystalline phase.
Host: Ilya Esterlis
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Astronomy Colloquium
Decoding Exoplanet Atmospheres: The Revolutionary Role of JWST
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Luis Welbanks, Arizona State University
Abstract: The 2020s and beyond will be the era of spectroscopy of exoplanet atmospheres. In just 2 years, our field has made dramatic advancements, moving from having very limited wavelength coverage and precision data from the Hubble Space Telescope (HST), to having high-precision spectroscopy over a wide wavelength range (~0.4 to 20μm) with the James Webb Space Telescope (JWST). These exquisite observations come with the opportunity to perform detailed reconnaissance of exoplanet atmospheres, explore their chemical and physical properties, and perform population-level studies to test our hypotheses for planet formation and evolution.

In this talk, I will share with you the advancements ushered by the era of JWST, allowing us to answer not only what exoplanet atmospheres are made of, but also which data drive our inferences and how reliable these inferences are. I will present the results from several programs with JWST. In these programs, we detect and constrain several chemical species that were previously elusive in exoplanetary atmospheres, including methane (CH4), ammonia (NH3), sulfur dioxide (SO2), carbon monoxide (CO), and carbon dioxide (CO2), alongside several precise water (H2O) measurements. The atmospheric retrievals performed on these data provide insights into the dynamics, chemistry, and climatic conditions of these distant worlds, as well as their metallicities. They also provide the relative elemental ratios (C/O, N/O, N/S) necessary to better understand the formation and evolution pathways of planetary systems.

I will present our progress in robustly and accurately processing JWST Time-Series Observations data. Additionally, I'll discuss modeling advancements and our methods for reliably inferring the complete chemical inventory of our diverse exoplanet sample. Our findings underscore the transformative power of JWST and pave the way for future, in-depth atmospheric investigations of a larger exoplanet population.
Host: Ke Zhang
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Friday, December 8th, 2023

Graduate Program Event
Preliminary Exam
Detection and Characterization of Core Magnetic Fluctuations on DIII-D using Faraday-Effect Polarimetry
Time: 1:30 pm - 3:30 pm
Place: 2301 Sterling
Speaker: Rachel Myers, Department of Physics Graduate Student
Abstract: Internal, resistive MHD instabilities called tearing modes (TMs) significantly contribute to disruptions and confinement degradation in tokamaks. Measuring nonlinear TM coupling with high m/n near the magnetic axis can aid in understanding neoclassical TM seeding, growth, and decay. For this tracking, we use the Radial Interferometer-Polarimeter (RIP), which is sensitive to core-resonant magnetic fluctuations on DIII-D and has detected TMs well before they appear on edge magnetic sensing coils [Pandya, DPP invited talk 2021]. Here we employ RIP to analyze the impact on pre-existing TMs of multiple, emerging MHD modes that are never detected by the coils. In one example, RIP detects a higher-frequency mode coupled to both an n=2 mode and a lower-frequency mode that later diminishes. All three modes are resonant near the magnetic axis, and their interaction is only visible using RIP. In this talk we will also discuss tearing mode structure and its potential effects on RIP-measured tearing mode amplitudes.

Zoom link:
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Graduate Program Event
Q&A with ISS representative
Time: 2:15 pm - 3:00 pm
Place: 2241 Chamberlin
Abstract: Sara Sheibani from ISS will be joining us. She will have a short presentation about ISS and then we’ll have plenty of time for questions. I encourage you to pose questions in advance, but feel free to just bring them along, too. Questions ahead can be added here: Hope to see you there! p.s. Come to ask questions. . .or come for the bagels and coffee! Either way, come join us!
Host: Sharon Kahn and Arifa
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Physics Department Colloquium
Origins of nematicity and field-induced superconductivity in iron-based materials
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Shua Sanchez, Postdoctoral Fellow, MIT
Abstract: Materials with strongly correlated electrons can give rise to interesting and useful phenomena, such as nematicity, magnetism, and unconventional superconductivity. In these systems, the charge, spin, and lattice degrees of freedom become intertwined, such that the origin of these phenomena becomes obscured. In this talk, I will discuss a new experimental platform which combines tunable applied strain, transport measurements, and several x-ray techniques to probe the origin and mechanisms of strongly correlated phases. I will review three recent studies in iron-based superconductors, which examine (1) the transport-structural correspondence in the nematic phase of doped BaFe2As2, (2) the orbital driver of nematicity in FeSe, and (3) the mechanism of field-induced superconductivity in ferromagnetic doped EuFe2As2. These diverse investigations demonstrate the power and promise of multimodal characterization for solving other puzzles in strongly correlated materials.

Sanchez, et al. Nature Materials (2021) DOI: 10.1038/s41563-021-01082-4
Occhialini and Sanchez, et al., Nature Materials (2023) DOI: 10.1038/s41563-023-01585-2
Sanchez, et al. Science Advances (2023) DOI: 10.1126/sciadv.adj520

Host: Victor brar
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