Events at Physics

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Events During the Week of April 29th through May 6th, 2018

Monday, April 30th, 2018

Plasma Physics (Physics/ECE/NE 922) Seminar
Centrifugal Confinement for Fusion and the Maryland Experiment (MCX)
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Adil Hassam, University of Maryland, College Park
Abstract: An axisymmetric magnetic mirror, rotating azimuthally at supersonic speeds, centrifugally confines plasma to the midplane, closing off the mirror loss cone. The accompanying velocity shear can stabilize the destructive flute interchange mode. The electric potential well scales as the deep centrifugal potential and exponentially throttles parallel electron heat losses, allowing access to the Lawson Condition at Mach 4 to 5. An experiment at the University of Maryland, spinning at Mach 2.5, showed steady state quiescent conditions with a density drop of ~12 along the field, and showed velocity shear exceeding the ideal interchange growth rate. The centrifugally confined mirror system can be steady state, and has no abrupt disruptions. While key questions need answering, the system presents unique possibilities as a strategic element for fusion. The theoretical basis for this system will be discussed and results from the MCX will be presented.
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Council Meeting
Time: 4:00 pm
Place: 2314 Chamberlin Hall
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Tuesday, May 1st, 2018

Chaos & Complex Systems Seminar
Year-end celebration
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin (Refreshments will be served)
Speaker: General discussion, UW Madison
Abstract: Following the tradition of recent years in which we had a delightful discussion of where we have come and where we might go with the seminars, this last seminar of the semester will be devoted to a continuation of that discussion without any formal speaker. We will also discuss what we want to do during our informal weekly lunches on the Memorial Union Terrace which begin on May 8th. This celebration will include expanded refreshments, to which your own culinary contribution is welcome.
Host: Clint Sprott
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"Physics Today" Undergrad Colloquium (Physics 301)
LZ and Dark Matter at UW
Time: 1:20 pm - 2:10 pm
Place: 2241 Chamberlin Hall
Speaker: Kimberly J. Palladino, UW Madison Department of Physics
Host: Wesley Smith
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Wednesday, May 2nd, 2018

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, May 3rd, 2018

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Fission and the formation of the r-process rare-earth abundance peak in neutron star mergers
Time: 2:30 pm
Place: 5280 Chamberlin Hall
Speaker: Nicole Vassh, University of Notre Dame
Abstract: The recent observations of the GW170817 electromagnetic counterpart
suggest lanthanides were produced in this neutron star merger event.
However many questions regarding heavy element production in mergers
remain: can such events account for all the r-process lanthanide material
observed in the galaxy? are precious metals such as gold produced in
sufficient amounts? are actinides produced? where within the merger
environment does nucleosynthesis occur and under what specific conditions?
Such questions can only be answered with careful studies of the nuclear
physics uncertainties affecting r-process calculations. Here I will
discuss recent extended calculations of beta-delayed fission and their
implications for r-process nucleosynthesis. The influence of fission
fragment distributions will also be addressed with a particular emphasis
on the unknown origin of the r-process rare-earth peak at A~164. Since the
rare-earth peak is formed as the r-process path begins to draw closer to
stability, the rare-earth nuclei contributing to peak formation will soon
be within reach of nuclear physics experiments performed at, for example,
the CPT at CARIBU and the upcoming FRIB. Here I will present the latest
results for the masses found to produce the rare-earth peak in a low
entropy accretion disk wind scenario and compare directly with recent mass
measurements from the CPT at CARIBU. Such collaborative efforts between
theory and experiment could soon be in a position to make definitive
statements regarding the mechanism of rare-earth peak formation and thus
the astrophysical site of the r process.
Host: Baha Balantekin
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Astronomy Colloquium
Can we send relativistic-speed nanocrafts to nearby exoplanets? Challenges and Solutions?
Time: 3:30 pm - 5:00 pm
Place: 4421 Sterling Hall, Coffee and Cookies 3:30 PM, Talk begins at 3:45 PM
Speaker: Thiem Hoang, University of Toronto
Abstract: The Breakthrough Starshot initiative aims to launch gram-scale spacecraft to relativistic speeds of v ~ 0.2 c, capable of reaching the closest Earth-like exoplanet, Proxima b, in 20 years. One of the most critical challenges facing this ambitious project originates from the interactions of relativistic nanocrafts with the interstellar medium during its journey to Proxima b. In this talk, I will first present our quantitative evaluation of the damage to a relativistic nanocraft by interstellar gas and dust. Second, I will discuss the deflection and oscillation of a charged nanocraft due to the interstellar magnetic field. Third, I will discuss the gas drag force at high energy regime and quantify its effect on the deceleration of a relativistic lightsail. Finally, I will discuss practical strategies to mitigate the impacts of the interstellar medium, and to control the nanocraft attitude in order for the spacecraft to reach an intended exoplanet.
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Friday, May 4th, 2018

Physics Department Colloquium
The microphysics of the GW170817 kilonova
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Rebecca Surman, Notre Dame University
Abstract: The optical signal that accompanied the GW170817 gravitational wave event
provided the first firm proof that neutron star mergers produce heavy
elements. Still, it is not known exactly which elements are produced by
mergers and in what proportions. A full understanding of neutron star
mergers and their role in galactic chemical evolution requires progress in
a number of areas. Two key areas are neutrino and nuclear physics.
Neutrino physics shapes the initial conditions for element synthesis, and
the nuclear physics of extreme neutron-rich nuclei governs how the
nucleosynthesis proceeds. Here we will review these microphysics aspects
of neutron star merger nucleosynthesis and discuss how current
uncertainties influence our interpretations of observed abundance patterns
and kilonova signals. We will then explore the promise of experimental
campaigns at rare isotope beam facilities to both reduce these
uncertainties and provide insight into astrophysical environments of heavy
element production.
Host: Baha Balantekin
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Physics Awards Banquet
Time: 5:30 pm
Place: The University Club
Abstract: Awards presentation for student and alumni award winners.
Host: Sridhara Dasu
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