Events on Monday, September 15th, 2025
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Plasma physics, results, and learnings from the first year of WHAM’s operation
- Time: 12:00 pm - 1:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Jay Anderson, UW Madison
- Abstract: WHAM has just completed its first year of operation, becoming the first fusion experiment to combine high-temperature-superconducting coils with MW-scale plasma heating systems in confining a relatively small (a ~ 15 cm, L = 2 m) plasma. Applying 17 T on the plasma in the mirror throat (a world record in magnetic confinement fusion research) presents a broad 4 T contour in the plasma to enable fundamental ECH at 110 GHz with access to high density operation. Indeed, WHAM’s achieved operational space spans central electron density between 2x10^17 and 2x10^20 per m3, bookended by an intense hot electron regime at low density and a fully collisional gas-dynamic regime at high density. WHAM’s physics missions focus on an intermediate density regime dominated by hot ions (via neutral beam injection) where particle confinement is governed by ion-ion pitch angle scattering and increases rapidly with average energy. The axisymmetric mirror is unstable to MHD interchange, and the tradeoff to its simple geometry and engineering advantages is requirement of additional actuators to ensure MHD stabilization. WHAM has partially reproduced the spectacularly successful vortex confinement technique via imposed ExB rotation and has achieved modest perpendicular beta of nearly 10% and ion energies up to 1 keV. Ongoing work aims to reduce charge exchange and radiated power losses, investigate alternate stabilization techniques, determine optimal mirror ratio, and continue to press upwards in ion energy via addition of rf heating. WHAM’s construction was funded by ARPA-E and ongoing research is supported by Realta Fusion.
- Host: Cary Forest
- Theory Seminar (High Energy/Cosmology)
- Astrophysical Probes of Complex Dark Sectors
- Time: 1:00 pm - 2:30 pm
- Place: Chamberlin 5280
- Speaker: Caleb Gemmell, UW-Madison
- Abstract: Complex dark sectors are models where a 'sector' of new particles with intra-sector interactions are used to extend the Standard Model. Motivated by theoretical considerations such as the Hierarchy Problem, these models generically also provide dark matter candidates. In this talk I will cover a range of astrophysical probes from the indirect detection of dark matter to using cosmological simulations to study sub-galactic structure, and outline how these methods are sensitive to the novel interactions and signatures that become possible in new dark confining sectors, or models of atomic dark matter. Event recording:
- Host: Joshua Foster