Events During the Week of July 20th through July 27th, 2025
Monday, July 21st, 2025
- No events scheduled
Tuesday, July 22nd, 2025
- Thesis Defense
- Design and Operation of a Novel Spectrometer Diagnostic at DIII-D for the Measurement of Magnetic Pitch and Toroidal Rotation at ELM-Relevant Timescales
- Time: 1:00 pm - 3:00 pm
- Place: ERB 106 or
- Speaker: Ryan Albosta, Physics PhD Graduate Student
- Abstract: Two novel single-channel Czerny-Turner spectrometers [1&2] have been deployed at the DIII-D tokamak for simultaneous and co-located measurements of the full spectrally-resolved Motional Stark Effect (MSE) Split Deuterium Beam Emission and the Carbon CVI charge exchange emission at high spectral (∆λ=0.13 nm) and temporal resolution (1-5 kHz). High throughput optics (f/#=2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. Initial results from a 2024 DIII-D ITER-similar H-mode experiment at DIII-D show clear toroidal rotation collapse during ELM crashes from the CER channels, accompanied by Sigma/Pi ratio changes over a similar timescale from the MSE channels. However, non-equilibrium neutral beam excited state populations appear to play a large role in pedestal MSE line ratios, as qualitatively predicted by the NOMAD quantum collisional codebase. Complex neutral beam physics has also been observed and successfully reproduced with a physics forward model, revealing a continuum of beam energies that further complicate the MSE spectrum. These effects and their impact on the MSE fitting process during fast ELM dynamics in the DIII-D pedestal will be discussed, as well as the implications for fast magnetic beam-emission measurements – and therefore bootstrap current analysis – in H-mode pedestals generally. Simultaneous magnetic pitch, beam populations, and rotation measurements will be shown during type-1 ELMs at 5 kHz, along with next steps towards further disentangling population and pitch effects within the MSE spectrum during large density fluctuations. [1] Albosta R et al.: Rev Sci Instrum. 2022
[2] Albosta R et al.: Rev Sci Instrum. 2024
*Supported by US DOE grants DE-FG02-89ER53296, DE-FG02-08ER54999 and DE-FC02-04ER54698. - Host: Benedikt Geiger and John Sarff
Wednesday, July 23rd, 2025
- Social Gathering
- Summer Recess
- Time: 12:30 pm - 1:00 pm
- Place: Bascom Hall in front of Birge Hall
- Speaker: Everyone is welcome
- Abstract: If the weather is nice, we'll meet on Bascom Hill (in front of Birge Hall). Feel free to bring your lunch. We will borrow cornhole and ladder toss from the L&S Dean's Office and play outside for 30 minutes. Some of us will probably walk up together, meeting in the courtyard between Chamberlin and Sterling ~12:25. Feel free to walk with us! No need to sign up. Just come join us!
- Host: Sharon Kahn
Thursday, July 24th, 2025
- Preliminary Exam
- The Ursa Major Moving Group: Membership, Age, and Planet Search
- Time: 11:00 am - 1:00 pm
- Place: B343 Sterling or
- Speaker: Julia Sheffler, Physics PhD Graduate Student
- Abstract: Since the discovery of the first exoplanet in 1992, the number of confirmed exoplanets has grown to nearly six thousand with more than seven thousand candidates awaiting confirmation. The rapidly increasing quantity of known exoplanets allows scientists to shift their focus from exoplanet discovery to deeper characterization and population studies. Of particular interest are populations of planets with known and, especially, young ages. The challenges associated with estimating ages of individual stars limits the existence of accurate age estimates for the majority of confirmed planets. By concentrating on stars within moving groups or clusters, we overcome many of these challenges, opening up a variety of independent age diagnostics. We focus on Ursa Major (UMa), a young (~400Myr), nearby (~25pc) moving group. We perform a volume limited kinematic membership analysis, provide more accurate and precise age estimates, and, in time, search for planets among UMa stars. Increasing our population of exoplanets with known ages less than 500 Myr, with proximity making them amenable to follow-up observations, provides critical data for understanding planetary evolution at early timescales.
- Host: Melinda Soares-Furtado
Friday, July 25th, 2025
- No events scheduled