Events at Physics

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Events During the Week of September 24th through October 1st, 2023

Monday, September 25th, 2023

Plasma Physics (Physics/ECE/NE 922) Seminar
The high-field, compact mirror path to fusion
Time: 12:00 pm - 1:15 pm
Place: 1610 Engineering Hall
Speaker: Prof. Cary Forest, UW-Madison Physics/ Realta
Abstract: In this talk I will provide a brief introduction to the compact magnetic mirror path to building a fusion energy system based on the tandem mirror. This approach relies on recent game changing physics results from axisymmetric mirror experiments [1] and the revolution in engineering high field magnets using high temperature superconductor materials. Our Wisconsin centric development path was started through ARPA-E sponsorship at the UW of WHAM (the Wisconsin HTS Axisymmetric Mirror) — I will begin a status report of the construction of WHAM including magnets (first successful tests of the 17 T magnets at CFS) and preparation of WHAM's heating systems (ECH, NBI and RF) and MHD stabilization systems. I will then review the theoretical physics basis for the fusion performance of WHAM that has relied on CQL3D Fokker Plank solutions for the fast ions injected by neutral beams and then heated by rf reported in a recent paper by Endrizzi [2]. The next phase along the development path will be carried out by a public-private partnership lead by an early stage startup, Realta Fusion. Realta is now beginning the engineering design activity of BEAM (a Break Even Axisymmetric Mirror) that will be a several MW DT device with Q approaching 1. Its purpose is two-fold, first it will provide the physics validation needed predict the performance of tandem mirror end plugs and second it will be well-suited to operate as a Fusion Volumetric Neutron Source (FVNS) for demonstrating heat removal and tritium breeding technology and described in Forest et al [3].

1 Simonen, T. C. et al, Three Game Changing Discoveries: A Simpler Fusion Concept? J Fusion Energ 35, 63–68 (2016).
2 Endrizzi, D. et al, Physics Basis for the Wisconsin HTS Axisymmetric Mirror Experiment, accepted in J Plasma Physics, (2023).
3 Forest, C.B et al, Prospects for a Break Even Axisymmetric Mirror (BEAM) and Applications, submitted to J Plasma Physics (2023).
Host: Prof. Steffi Diem
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Tuesday, September 26th, 2023

Coding Just Got Easier with Wolfram's New AI-Powered Chat Notebooks
Time: 3:00 pm - 3:30 pm
Place: Chamberlin Hall 5310
Speaker: Jeff Weidenaar, Wolfram
Abstract: Mathematica now has built-in AI, enabling you to interact in plain English and generate quality code. You will leave this session knowing how to use new Chat Notebooks in Mathematica. You'll also learn about some new Physics functionality.
Host: Dan Bradley
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Wednesday, September 27th, 2023

Theory Seminar (High Energy/Cosmology)
Problems with de Sitter in string theory
Time: 12:00 pm - 1:15 pm
Place: Chamberlin 5280 (Zoom link also available for online participants who signed up on our mailing list)
Speaker: Daniel Junghans, Institute for Theoretical Physics, TU Wien
Abstract: The simplest explanation for the observed accelerating expansion of our universe is that we live in an approximate de Sitter space. On the other hand, there is growing evidence that various popular proposals for realizing de Sitter space in string theory do not self-consistently control neglected string corrections. In this talk, we show such a control problem in two rather different proposals: the large-volume scenario and the supercritical scenario.
Host: Gary Shiu
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Thursday, September 28th, 2023

Astronomy Colloquium
The Census of Supermassive Black Holes over Cosmic Time
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Jonathan Trump, University of Connecticut
Abstract: Supermassive black holes are a critical ingredient in our Universe. They are the most luminous persistent sources in the sky, in both photons and gravitational waves, and they play an essential role in the formation and growth of galaxies. My research seeks a comprehensive census of black holes using two complementary approaches. First, I will show how pioneering new SDSS time-domain spectroscopy enables a census of black hole mass, growth rate, and spin over most of cosmic time. I will also present the forecast for Rubin/LSST discovery of binary black holes: the electromagnetic counterparts to gravitational echoes seen in pulsar timing and (eventually) LISA. Meanwhile the first year of JWST observations has revealed a surprisingly active early Universe, with a large number of massive black holes identified in z>5 galaxies. This implies a significant population of heavy black hole seeds and suggests that accreting black hole play a significant role in reionizing the Universe. The next generation of time-domain, space-telescope, and multi-messenger experiments make it a truly bright time for understanding the dark nature of black hole astrophysics.
Host: Ke Zhang
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Graduate Program Event
Coral biomineralization vs. climate change
Time: 6:00 pm - 8:00 pm
Place: 2241 Chamberlin
Speaker: Pupa Gilbert, Physics Faculty
Abstract: Coral reefs cover only 1% of ocean floors, yet they host 25% of all known marine species. This incredible
biodiversity is sheltered by the 3D structure of coral skeletons. My group and I revealed that corals form
their skeletons by attachment of amorphous calcium carbonate (ACC) nanoparticles, then fill
interstitial spaces by ion attachment. Subsequent crystallization starts as aragonite (CaCO3)
nanocrystals, randomly oriented and termed sprinkles, which coarsen and become radially oriented
acicular crystals termed spherulites. This is Nature’s 3D printing! The resulting space-filling, solid,
isotropic structure grows slowly (0.5-5.0 cm/year) to form m-km coral reefs visible from outer space.
Corals are threatened by climate change, including ocean warming and acidification. With acidification,
the solubility of CaCO3 increases, thus, making it increasingly difficult for corals to build their skeletons,
especially because the ACC transient precursor phase is more soluble than aragonite. Different coral
species are differently sensitive to ocean acidification, indicating that mechanistic biological factors link
ocean chemistry and CaCO3 mineral growth, which we are studying. My group’s research suggests two
science-based interventions to help coral reefs. First, species selection based on resilience to acidification may allow repopulation of damaged reef ecosystems. Second, we are building electrified grids on
which corals are expected to grow faster, resist bleaching and acidification.
Presentation: Pupa's flyer-2.pdf
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Friday, September 29th, 2023

Physics Department Colloquium
Hunting for “fifth forces”, axions, and dark matter with optomechanical and spin-based sensors
Time: 3:30 pm - 5:00 pm
Place: Chamberlin 2241
Speaker: Andrew Geraci, Northwestern
Abstract: Despite the enormous success of the Standard Model of particle physics, many basic phenomena around us remain without any explanation, including the nature of Dark Matter and Dark Energy, which together make up 95 percent of our universe. Complementary to high-energy particle colliders or large-scale detectors, a variety of ultra-sensitive tabletop experiments are well-suited to discover a wide range of new phenomena beyond the Standard Model, where feeble interactions require precision measurements rather than high energies. In this talk I will describe our experimental efforts using dielectric objects supported by radiation pressure as precision sensors to search for quantum effects related to gravity, high-frequency gravitational waves, and Dark Matter. I will also discuss The Axion Resonant InterAction Detection Experiment (ARIADNE), which aims to detect novel short-range spin-dependent interactions.
Host: Mark Saffman
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