BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:1 UID:UW-Physics-Event-8646 DTSTART:20240304T180000Z DTEND:20240304T191500Z DTSTAMP:20260413T223402Z LAST-MODIFIED:20240228T082537Z LOCATION:1227 Engineering Hall SUMMARY:Schnack Memorial Seminar: "Plasma instabilities associated wit h runaway electron beam and their potential influences”\, Plasma Phy sics (Physics/ECE/NE 922) Seminar\, Dr. Chang Liu\, PPPL (Princeton Pl asma Physics Laboratory) DESCRIPTION:High-energy runaway electron beams can be generated in fus ion experiments during various discharge phases. Control and mitigatio n of runaway electron beams and reducing their energy impact on the pl asma-facing walls is critical to the operation of ITER and other tokam aks. Interestingly\, the high energy of these electrons can also provo ke plasma instabilities\, creating pathways for the electrons to dissi pate energy and diffuse in space. In this presentation\, I will discus s some of the common instabilities driven by runaway electrons observe d in experiments and the efforts to model them. High-frequency plasma waves\, such as whistler and extraordinary electron (EXEL) waves\, can be stimulated by the anisotropic distribution of runaway electrons an d resonating with their cyclotron motion. This resonance can lead to r apid pitch-angle scattering\, manifested as an abrupt increase in elec tron cyclotron emission (ECE) signals. In addition\, these instabiliti es can affect the runaway electrons' avalanche growth and raise the cr itical electric field for the transition from growth to decay of runaw ay electron population. Lower frequency plasma waves can also be excit ed if they resonate with the precession motion of the trapped runaway electrons. The excitation of plasma instabilities in the Alfvén frequ ency range has been observed in DIII-D\, AUG and JET disruption experi ments\, and has been shown to contribute to the loss of runaway electr ons during current quench. The interaction between these Alfvén oscil lations in the background plasma and runaway electrons can be explored through kinetic-MHD simulations\, including calculations of linear gr owth\, nonlinear saturation\, and the consequent transport of runaway electrons. URL:https://www.physics.wisc.edu/events/?id=8646 END:VEVENT END:VCALENDAR