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Events on Friday, February 9th, 2024

Physics Department Colloquium
Retrieving images from tarnished 19th century daguerreotypes using X-ray fluorescence imaging with an X-ray micro beam with tunable energy
Time: 3:30 pm - 5:00 pm
Place: Chamberlin 2241
Speaker: Tsun-Kong (T.K.) Sham, Western University, Ontario
Abstract: An overview of the recent success of using X ray fluorescence (XRF) imaging excited with a tunable X-ray microbeam from synchrotron light sources for the recovery of damaged and obstructed 19th century daguerreotype will be presented. [1, 2] Daguerreotype is the first commercial photography in human history (early 1800’s) produced on a polished, silver coated copper plate. We show that high quality images can always be retrieved from tarnished plates using Hg L XRF as long as the bulk of the image particles and their distribution remain intact. This technique overcomes the challenges of conventional conservation methods which are often unable to bright the image back to life. We also report results from using tunable tender X-rays (2 - 7 keV) to image in high vacuum at energy above the Ag L-edge and the Hg M-edge, extracting images using Ag L and Hg M, respectively among others (e.g., S to track corrosion). Images obtained with the surface sensitive total electron yield (TEY) and the bulk sensitive fluorescence yield (FLY) as well as corresponding micro-XANES are noted. Flux tolerance to high intensity X-beam is also explored. These results and their implications for cultural heritage and other cultural heritage research and prospects of the technique at fourth generation light sources will be discussed. 1. Kozachuk, M.S.; Sham, T.K.; Martin, R.R.; Nelson, A.J.; Coulthard, I.; McElhone, J.P. Recovery of Degraded-Beyond Recognition 19th Century Daguerreotypes with Rapid High Dynamic Range Elemental X-ray Fluorescence Imaging of Mercury L Emission. Sci. Rep. 2018, 8, 1. 2. Stark, A; Filice, F.; Noël, J.J.; Martin, R.R.; Sham T.K.; Finfrock, Y.Z.; Heald, S.M. Retrieving Tarnished Daguerreotype Content Using X-ray Fluorescence Imaging-Recent Observations on the Effect of Chemical and Electrochemical Cleaning Methods, Herit. Sci. 2021, 4, 1605-1615 *Research conducted at Western University is supported by NSERC, CFI, CRC of Canada and OIT of Ontario and Western University
Host: Uwe Bergmann
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Chasing ghost particles: searching for neutrinos from high-energy sources in real time
Time: 7:15 pm - 9:00 pm
Place: Space Place, 2300 S Park St and virtual, see abstract for link
Speaker: Jessie Thwaites, UW–Madison Physics / WIPAC
Abstract: Neutrinos are tiny, nearly massless particles that interact very rarely. Because of this, astrophysical neutrinos can travel very far, all the way to the South Pole, carrying information directly from their sources. The IceCube Neutrino Observatory has detected these astrophysical neutrinos, but only a few sources have been identified thus far. We search for these neutrinos from transient sources – sources that vary in their brightness over time, such as gamma-ray bursts (GRBs), supernovae, novae, or mergers of compact objects. These sources often have very energetic processes happening inside them to accelerate particles and produce these neutrinos. By searching for these transient sources as they’re happening (in real time), we can inform follow-up by other observatories also searching for them, and better understand the nature of some of the highest energy phenomena in our universe.

Jessie Thwaites is a 4th year graduate student in the UW—Madison Physics department, working with Justin Vandenbroucke on the IceCube Neutrino Observatory. Their research focuses on searching for high energy astrophysical sources of neutrinos from transient sources, in both real time and archival data. In addition to research, Jessie writes for Astrobites, a daily science communication blog that summarizes astronomy or astrophysics papers into bite-sized pieces for the public. Outside of physics, Jessie plays horn and enjoys hanging out with their cat, Ryan.

This meeting will take place in-person at our usual Space Place classroom location. It will also be streamed live to our YouTube channel at
Host: Madison Astronomical Society
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