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This Week at Physics

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Events During the Week of November 18th through November 24th, 2012

Monday, November 19th, 2012

Plasma Physics (Physics/ECE/NE 922) Seminar
Fast Ion Confinement and Stability of an NBI-heated RFP
Time: 12:00 pm
Place: 1310 Sterling Hall
Speaker: Jay Anderson, University of Wisconsin-Madison
Abstract: The envisioned burning plasma experiment, regardless of magnetic concept, relies on sufficient confinement of the charged fusion products for plasma self heating. As such, the confinement of fast ions and their impact on the bulk plasma are crucial issues. While well-studied in tokamak, ST and stellarator plasmas, relatively little is known in RFP plasmas about the dynamics of fast ions and the effects they cause as a large population. These studies are now underway in MST with an intense 25 keV, 1 MW hydrogen neutral beam injector (300 MW/m^2 at injection port). Fast particles are confined much better than thermal particles in the stochastic RFP magnetic field, and a significant population of fast ions develops during NB injection. TRANSP simulations predict a super-Alfvenic ion density of up to 25% of the electron density with both a significant velocity space gradient and a sharp radial density gradient. There are several effects on the background plasma including enhanced toroidal rotation, electron heating and an altered current density profile. The abundant fast particles affect the plasma stability. Fast ions at the island of the core-most resonant tearing mode have a stabilizing effect, and up to 60% reduction in the magnetic fluctuation amplitude is observed during NBI. Simultaneously, beam driven instabilities are observed for the first time in the RFP. Repetitive 50 us bursts of m=1 modes have scaling signatures of both Alfvenic and continuum energetic particle modes. The dominant modes are n=4 (EP-like) and n=5 (AE-like), which nonlinearly couple to an n=1 mode. The feedback of the altered plasma stability on the fast ion confinement is investigated.
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Condensed Matter Theory Group Seminar
The Anderson-Higgs mechanism in Condensed Matter Physics
Time: 4:30 pm
Place: 5310 Chamberlin
Speaker: Dushko Kuzmanovski & Saurabh Maiti
Abstract: With recent renewed interest in the Higgs mechanism after the announced discovery of the Higgs particle by experimental groups at the LHC, it is instructive to remind oneself of its manifestations in Condensed Matter Physics phenomena. We give a pedagogic overview of the topic of spontaneous symmetry breaking and the role of gauge symmetries. We also try to assess the role that P.W. Anderson had played in the formulation of the mechanism from a historical perspective. Finally, we put things into perspective of the electroweak gauge symmetry breaking.
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Tuesday, November 20th, 2012

Chaos & Complex Systems Seminar
Searching for the earliest life on Earth
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Clark Johnson, UW Department of Geoscience
Abstract: Finding evidence for the earliest life on Earth requires a bit different approach than say digging for dinosaur bones, because the evidence is much more cryptic. Microbial life dominated the biosphere for perhaps 4 billion years, yet the number of known localities of undisputed microfossils is quite small. What is a weird spot under the microscope and what represents true cellular remains? Fossilized microbial communities (stromatolites), which give us a hint about ancient ecosystems, are even more rare, and also subject to debate. Another approach, one we are taking at UW-Madison, is to look for the fingerprints of ancient microbial metabolisms that are left in the isotopic record of element that are cycled by life. These can be found in remnant carbon compounds, or in inorganic minerals that may be the product of microbial metabolism. In addition, such fingerprints inform us about past environmental conditions that permit, or do not permit, life (liquid water, etc.). We will take a broad tour of these issues, focusing on what we know, and do not know, from the formation of the Earth at 4.5 b.y. ago up to the first major rise in atmospheric oxygen about 2 b.y. ago.
Host: Sprott
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Wednesday, November 21st, 2012

No events scheduled

Thursday, November 22nd, 2012

Thanksgiving Recess

Friday, November 23rd, 2012

Thanksgiving Recess

Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:00 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
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