Events at Physics |
Events During the Week of October 11th through October 18th, 2015
Monday, October 12th, 2015
- Plasma Physics (Physics/ECE/NE 922) Seminar
- H-mode and ELM Studies at Near-Unity Aspect Ratio
- Time: 12:00 pm - 1:00 pm
- Place: 2241 Physics Bldg
- Speaker: Kathreen Thome, Engineering Physics
- Abstract: The H-mode confinement regime is achieved at near-unity aspect ratio (A < 1.2) in the Pegasus Toroidal Experiment via high-field-side fueling and low edge recycling. Ohmic H-mode is attained in both limited and diverted magnetic topologies. This regime is characterized by: reduced Dα emissions; increased core rotation; increased central heating; formation of edge current and pressure pedestals; and improved energy confinement. The H-mode power threshold, PLH, behaves quite differently at low-A when compared with high-A operations. PLH/PLH_ITPA08 increases sharply as A is lowered and no difference in PLH for limited and diverted plasmas is observed at A ~ 1.2. No minimum in PLH with density is observed. Some of these results are consistent with the FM3 model for the L-H transition [1]. Two classes of ELMs have been observed. Small, Type III-like ELMs are present at low input power and have n ≤ 4. At POH >> PLH, they transition to large, Type-I-like ELMs with intermediate 5 < n < 15. The Type III ELM magnetic structures behave opposite to that observed in high-A plasmas, with n much higher, presumably due to the naturally higher J/B peeling mode drive at low-A. Long-sought measurements of the Jedge(R,t) pedestal collapse during an ELM event show a complex, multimodal pedestal collapse and the subsequent ejection of a current-carrying filament.
- Host: Engineering Physics
Tuesday, October 13th, 2015
- Chaos & Complex Systems Seminar
- The power to change lives: The UW Odyssey Project
- Time: 12:05 pm - 1:00 pm
- Place: 4274 Chamberlin (refreshments will be served)
- Speaker: Emily Auerbach, UW Department of English
- Abstract: Yasmin’s son rescued her from a crack house in Chicago and brought her to Madison, where she enrolled in the UW Odyssey Project. She now has her bachelor’s degree, works as a substance abuse counselor, and is on her way to a master’s in social work from the UW-Madison. How can one intervention, one alteration in a pathway, change whole families and break a cycle of generational poverty? Why is improvisation the best teaching method for helping at-risk adults and youth find their voices and change their lives? Come learn how the UW Odyssey Project (www.odyssey.wisc.edu) has been transforming lives for over a dozen years.
- Host: Sprott
- Theory Seminar (High Energy/Cosmology)
- Cosmological Probes of Nearly Decoupled Dark Sectors
- Time: 3:30 pm - 4:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Josh Berger, University of Wisconsin-Madison
- Abstract: Many models of cold dark matter generate the observed relic abundance by employing dark photons and/or dark Higgs bosons as mediators. In this work, we place constraints on the mediator parameter space by considering nucleosynthesis and CMB spectral distortion constraints. We focus on the limit when the mediators have very weak mixing with the Standard Model. Before their decay, mediator abundance is frozen-in. We find dramatic improvement on the spectral distortion constraints can be generated from a proposed experiment such as PIXIE.
- Host: Amol Upadhye
Wednesday, October 14th, 2015
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin Hall
Thursday, October 15th, 2015
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:15 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (lzhang263@wisc.edu) - Host: Peter Timbie
- Cosmology Journal Club
- Time: 12:15 pm - 1:15 am
- Place: 5242 Chamberlin Hall
- Abstract: An informal discussion about a broad variety of arXiv papers related to cosmology. Please visit the following link for more details:<br><br>
<a href="<a href="http://cmb.physics.wisc.edu/journal/index.html">http://cmb.physics.wisc.edu/journal/index.html</a>"><a href="http://cmb.physics.wisc.edu/journal/index.html">http://cmb.physics.wisc.edu/journal/index.html</a></a><br><br>
Please feel free to bring your lunch! If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Amol Upadhye (aupadhye@wisc.edu). - Host: Amol Upadhye
- Astronomy Colloquium
- Observational Assessment of Stellar Feedback in Star-Forming Regions
- Time: 3:45 pm - 5:00 pm
- Place: 4421 Sterling Hall, Coffee and Cookies 3:30 PM
- Speaker: Laura Lopez, Ohio State University
- Abstract: Stellar feedback has a profound influence in many astrophysical phenomena, yet it is often cited as one of the biggest uncertainties in star and galaxy formation models today. This uncertainty stems from a dearth of observational constraints as well as the great dynamic range between the small scales (<1 pc) over which feedback occurs and the large scales (>1<br>kpc) on which galaxies are shaped by that feedback. In this talk, I will show how multiwavelength observations can be used to overcome these challenges to assess the role of many stellar feedback mechanisms, including radiation, stellar winds, supernovae, and cosmic rays. I will present results from the application of these approaches to a variety of sources and discuss the implications regarding the dynamics of star-forming regions and the launching of galactic winds. Finally, I will highlight the exciting prospects of using current and upcoming facilities to explore feedback in diverse conditions.
- Graduate Introductory Seminar
- Plasma Physics
- Time: 4:30 pm - 5:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Boldyrev, Egedal, Forest, Sarff, Terry, Zweibel
Friday, October 16th, 2015
- Physics Department Colloquium
- Particle acceleration and magnetic field generation in astrophysical plasmas
- Time: 3:30 pm - 4:30 pm
- Place: 2241 Chamberlin Hall (Coffee & Cookies at 3:15pm)
- Speaker: Anatoly Spitkovsky, Princeton University
- Abstract: Shocks in low density plasmas (so-called "collisionless shocks") are ubiquitous throughout the Universe, and are thought to be responsible for the generation of nonthermal particles that extend over decades in energy. I will describe the progress in modeling collisionless shock structure and particle acceleration using ab-initio kinetic simulations, focusing on the current understanding of magnetic field amplification mechanisms, the conditions necessary for particle injection into the acceleration process, and the physics behind the electron-to-ion ratio in shock acceleration. I will also describe a new scenario for generation of the first magnetic fields during structure formation that can be important for seeding magnetic fields in galaxies.
- Host: Jan Egedal