Plasma Seminars Fall 2020

Tuesday December 1, 2020 at 4:00pm, Lothar Schmitz, Department of Physics & Astronomy, UCLA, "Reducing the L-H Transition Power Threshold in ITER—What Can We Learn from Microscopic Transition Physics?" Contact Meg Murphy for Zoom meeting link and information.

Abstract: High confinement mode (H-mode) operation is essential for the International Thermonuclear Experimental Reactor (ITER) and future burning plasmas, yet no predictive physics-based model exists so far for the required L-H transition threshold power. We demonstrate here on DIII-D that fast (0.1-1 ms) electric field transients, quantitatively consistent with the radial polarization current, initiate the transition once the transient E×B shearing rate exceeds the plasma frame turbulence decorrelation rate [1]. Edge turbulence is subsequently suppressed as the Reynolds stress increases, allowing the edge transport barrier to form.

Significant differences in transition dynamics are observed between Helium and Hydrogen plasmas (important for pre-nuclear physics operation in ITER). In recent experiments, we have demonstrated that the observed high power threshold in hydrogen (a substantial challenge for ITER) could be reduced by Helium dilution. Initial experiments also indicate that the L-H power threshold can be reduced at low ion collisionality via Neoclassical Toroidal Viscosity (NTV) from applied n=3 non-resonant magnetic fields (NRMF).

[1] L. Schmitz et al., Phys. Rev. Lett. 108, 155002 (2012).

Tuesday November 17, 2020 at 3:00pm, Nuno F. Loureiro, MIT, Boston MA, "New Insights into Plasma Turbulence." Contact Meg Murphy for Zoom meeting link and information.

Abstract: The current understanding of plasma turbulence in the MHD regime suggests that turbulent eddies become progressively more elongated structures in the plane perpendicular to the local mean magnetic field. Using recent results from reconnection theory, we argue that such eddies must inevitably fall prey to the tearing instability. As a result, there is a transition, in the inertial range, to a tearing (reconnection)-mediated turbulent cascade, where the spectral scaling k^{-11/5} is predicted. These results can be extended to collisionless plasmas; in the different regimes of interest that have been explored, the magnetic energy spectral scaling is invariably found to be in the range k^{-8/3} to k^{-3}, consistent with many observations.

SoCal Plasma Zoom Seminar: Tuesday November 3, 2020 at 9:00am, David Hughes (Leeds University UK), "Inertialess Dynamos in Rotating Convection." Contact Meg Murphy for Zoom meeting link and information. Co-sponsored by UC San Diego, UCI, UCLA.

Plasma Seminars Winter 2020

Friday January 24, 2020, 1:00pm, PAB 4-330, Matthias Knolker, General Atomics/Oak Ridge Associated Universities: Super H-mode: Optimizing the pedestal to raise performance in future fusion reactors.

Monday, March 2, 2020, 1:00pm, PAB 4-330, Marija Vranic, University of Lisbon: Extreme plasma dynamics in intense laser fields

Thursday, March 5, 2020, 11:00am, PAB 4-330, Alfred Mallet, University of California, Berkeley: The Structure of Plasma Turbulence: Anisotropy, Intermittency and Reconnection

Thursday, March 12, 2020, 11:00am, PAB 4-330, Colby Haggerty, University of Chicago: Non-Linear Ion Acceleration in Collisionless Plasma Shocks: New Perspectives from Kinetic Simulations

Monday, March 16, 2020, 1:00pm, department members only, Rogerio Jorge, University of Maryland at College Park: Confining Plasmas at Arbitrary Collisionalities and Arbitrary Geometries

Thursday, March 19, 2020, 11:00am, department members only, Silvia Espinosa, NYU Courant Institute of Mathematical Sciences: Quadrupling fusion power with free fueling

Monday, March 30, 2020, 1:00pm, department members only, Luca Comisso, Columbia University: From Turbulence to Reconnection to Particle Acceleration: Connecting Fundamental Plasma Processes

Monday, April 6, 2020, 1:00pm, department members only, Paulo Alves, Stanford Linear Accelerator National Laboratory: Accelerating our understanding of the multi-scale dynamics of high-energy plasmas

Thursday, April 9, 2020, 11:00am, department members only, Siyao Xu, University of Wisconsin-Madison: Turbulent amplification of cosmic magnetic fields

Plasma Seminars Fall 2019

Monday September 30, 2019, 2:00pm, PAB 4-330: Marija Vranic, Instituto Superior Tecnico, Universidade de Lisboa, Portugal: Plasma in Extreme Conditions.

Friday Oct 4, 2019, 1:30pm, PAB 4-330: Vladimir V. Zhdankin, Princeton University: Kinetic turbulence in relativistic and radiative plasmas.

Friday Oct 11, 2019, 2:00pm, BaPSF Auditorium 15-70 Rehab: Matthew Poulos, UCLA: Model for emissive cathode operation in a large magnetized plasma and controlled generation of plasma flows.

Thursday Dec 5, 2019, 1:00pm, PAB 4-330: Xianzhu Tang, Los Alamos National Laboratory: The physics of runaway electrons in a tokamak disruption.

Tuesday Dec 10, 2019, 2:00pm, PAB 4-330, Noemie Globus, NYU/CCA: Plasma injection and jet formation in black holes.

Click here to view the Plasma Seminars archive (PDF).