Events at Physics
Events During the Week of May 3rd through May 10th, 2015
- Plasma Physics (Physics/ECE/NE 922) Seminar
- 43 years of fun basic plasma experiments
- Time: 12:00 pm
- Place: 1610 Engineering Hall
- Speaker: Noah Hershkowitz , UW-Madison
- Abstract: This talk will present an overview of some of the most enjoyable low-temperature plasma experiments I have carried out with my students over the course of my career. It will begin with the connection between solitons and the Schrödinger equation, and continued with the discovery of cylindrical and spherical soliton-like structures. From moving structures we will progress to stable ones: sheaths and double layers. Where do double layers form? How can we measure double layer potentials? These questions lead to the development of emissive probe techniques. From there we will move on to the Bohm criterion and the first measurements of the full plasma potential variations of sheaths and presheaths in a single-species plasma, and later in two-ion-species plasmas. Finally, our recent measurements of double layers and presheaths in uniform helicon plasma will be presented, which address the earlier unresolved question of where double layers form.
- Host: UW
- No events scheduled
- No events scheduled
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Probing hadronic interactions with atmospheric leptons
- Time: 2:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Anatoli Fedynitch, Karlsruhe
- Abstract: Inclusive fluxes of muons and neutrinos in the atmosphere provide a continuous source of information about the spectrum and composition of cosmic rays interacting with air nuclei. Furthermore, measurements of the fluxes allow us to learn more about hadronic interactions in phase space regions not accessible at high-energy colliders. Using an accurate and flexible solution of the coupled cascade equations, called matrix-method, it is possible to study numerically the connection between atmospheric muon observations and measurements made at fixed-target or collider experiments. I will present the status of lepton
flux calculations using different interaction models and primary cosmic ray flux assumptions. Emphasis is put on the role of hadronic interactions by discussing the importance of different phase-space regions, particle species and interaction energies for the prediction of atmospheric lepton fluxes.
- Host: Paolo Desiati
- Astronomy Colloquium
- Searching for evidence for ongoing cold accretion in the local universe using the Green Bank Telescope
- Time: 3:35 pm
- Place: 4421 Sterling Hall
- Speaker: DJ Pisano, West Virginia University Physics & Astronomy
- Abstract: One of the key questions in astronomy today is how galaxies accrete the gas they need to fuel ongoing star formation. While many interferometric surveys have revealed populations of low mass HI clouds around galaxies, they have not found enough gas to sustain continued star formation. One possible explanation of this deficit is that this HI is extended and diffuse such that it is missed by interferometers. To rectify this problem, my collaborators and I are conducting a Green Bank Telescope (GBT) HI survey of about 50 local galaxies. The GBT's unique design makes it the ideal single-dish telescope for observing low column density HI and makes it capable of detecting HI emission from analogs to Lyman limit systems. I will present the initial results from our search for ongoing accretion from the ``cosmic web", how it compares with theoretical predictions, and our future plans.
- Physics Department Colloquium
- Distinguished Alumni Award Winner
- Where Did Half the Starlight in the Universe Go?
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Mark Devlin, University of Pennsylvania
- Abstract: We believe that approximately half of all the light from stars is absorbed and reprocessed by dust. The resulting emission is grey body with a temperature near 30 Kelvin. The COBE satellite made the first measurements of the resulting Far Infrared Background (FIRB), but since that time, we have been unable to resolve the background into individual galaxies. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) was designed to do this job. Its three bands at 250, 350, and 500 microns span the peak in emission for galaxies at z=1. I will discuss the BLAST experiment and present results from our measurements of resolved and unresolved galaxies. I will also discuss the implications for star formation in our own galaxy and how dust is changing the way we look at current and future searches for primordial gravity waves with the Cosmic Microwave Background.
- Host: Dan McCammon