Speaker
Mr
John Sarff
(USA)
Description
This overview of results from the MST program summarizes physics important for the advancement of the RFP as well as for improved understanding of toroidal magnetic confinement in general. Evidence for the classical confinement of ions in the RFP is provided by analysis of impurity ion transport. With inductive current profile control, the test-particle diffusivity for ions in a stochastic magnetic field is reduced below the classical transport level. (The neoclassical enhancement of radial transport is negligible in the RFP.) Carbon impurity measured by CHERS reveals a hollow profile and outward particle convection. Modeling of classical transport agrees with the profile evolution, and temperature screening explains the hollow profile. Classical confinement is also observed for energetic ions created by 1 MW NBI. The energetic ion confinement is consistent with classical slowing-down and ion loss by charge-exchange. The first appearance of Alfven eigenmodes and energetic particle modes by NBI in a RFP plasma are obtained. MST plasmas robustly access the quasi-single-helicity state that has commonalities to the stellarator and “snake” formation in tokamaks. The dominant mode grows to 8% of the axisymmetric field strength, while the remaining modes are reduced. Energy confinement is improved as a result. Predictive capability for tearing mode behavior has been improved through nonlinear, 3D, resistive MHD computation using the measured resistivity profile and Lundquist number, which reproduces the sawtooth cycle dynamics. New two-fluid analysis that includes Hall physics and gyro-viscosity has established a new basis for understanding physics beyond a single-fluid model. Nonlinear two-fluid (NIMROD) computation reveals coupling of parallel momentum transport and current profile relaxation. Large Reynolds and Maxwell stresses, plus separately measured kinetic stress, indicate an intricate momentum balance and possible origin for MST’s intrinsic plasma rotation. Microturbulence from drift-wave-like instabilities might be important in the RFP when magnetic fluctuations are reduced. New gyrokinetic analysis indicates that micro-tearing modes can be unstable at high beta, with a critical gradient for the electron temperature that is larger than for tokamak plasmas by roughly the aspect ratio. Supported by US DoE and NSF.
Country or International Organization of Primary Author
USA
Primary author
Mr
John Sarff
(USA)
Co-authors
Dr
Abdulgader Almagri
(University of Wisconsin-Madison)
Mr
Adam Falkowski
(University of Wisconsin-Madison)
Dr
Alexander Ivanov
(Budker Institute of Nuclear Physics)
Mr
Andrew Seltzman
(University of Wisconsin-Madison)
Ms
B Momo
(Consorzio RFX)
Dr
Brett Chapman
(University of Wisconsin-Madison)
Carl Sovinec
(University of Wisconsin-Madison)
Prof.
Cary Forest
(University of Wisconsin-Madison)
Dr
D Terranova
(Consorzio RFX)
Mr
Daniel Carmody
(University of Wisconsin - Madison)
Dr
Daniel Den Hartog
(University of Wisconsin-Madison)
Prof.
Darren Craig
(Wheaton College)
Dr
David Brower
(UCLA)
Dr
Derek Thuecks
(University of Wisconsin-Madison)
Dr
Deyong Liu
(University of Wisconsin-Madison)
Dr
Diane Demers
(Xantho Technologies)
Dr
Don Holly
(University of Wisconsin-Madison)
Dr
Donald Spong
(Oak Ridge National Laboratory)
Mr
Douglas Stone
(University of Wisconsin-Madison)
Dr
E Martines
(Consorzio RFX)
Mr
Eli Parke
(University of Wisconsin-Madison)
Dr
F Auriemma
(Consorzio RFX)
Dr
Hillary Stephens
(University of Wisconsin-Madison)
Mr
J. David Lee
(University of Wisconsin-Madison)
Dr
Jacob King
(University of Wisconsin-Madison)
Mr
James Duff
(University of Wisconsin-Madison)
Dr
James Titus
(Florida A&M University)
Dr
Jay Anderson
(University of Wisconsin-Madison)
Mr
Jeff Waksman
(University of Wisconsin-Madison)
Dr
Jinseok Ko
(University of Wisconsin-Madison)
Dr
John Goetz
(University of Wisconsin-Madison)
Mr
Jonathan Koliner
(University of Wisconsin-Madison)
Mr
Joseph Triana
(University of Wisconsin-Madison)
Dr
Joshua Reusch
(University of Wisconsin-Madison)
Mr
Juhyung Kim
(University of Wisconsin-Madison)
Dr
Karsten McCollam
(University of Wisconsin-Madison)
Mr
Kyle Caspary
(University of Wisconsin-Madison)
Dr
Liang Lin
(UCLA)
Dr
M Spolaore
(Consorzio RFX)
Dr
Maria Ester Puiatti
(Consorzio RFX)
Dr
Mark Nornberg
(University of Wisconsin-Madison)
Mr
Mark Thomas
(University of Wisconsin-Madison)
Ms
Meghan McGarry
(University of Wisconsin-Madison)
Mr
Michael Borchardt
(University of Wisconsin-Madison)
Dr
N Stupishin
(Budker Institute of Nuclear Physics)
Dr
P Deichuli
(Budker Institute of Nuclear Physics)
Dr
P Franz
(Consorzio RFX)
Dr
P Innocente
(Consorzio RFX)
Dr
P Piovesan
(Consorzio RFX)
Dr
P Zanca
(Consorzio RFX)
Mr
Paul Nonn
(University of Wisconsin-Madison)
Prof.
Paul Terry
(University of Wisconsin-Madison)
Dr
Peter Fimognari
(Xantho Technologies)
Dr
R Lorenzini
(Consorzio RFX)
Dr
R.W. (Bob) Harvey
(CompX)
Dr
Richard Magee
(University of Wisconsin-Madison)
Dr
S Polosatkin
(Budker Institute of Nuclear Physics)
Dr
Santosh Kumar
(University of Wisconsin-Madison)
Mr
Scott Eilerman
(University of Wisconsin-Madison)
Mr
Steve Oliva
(University of Wisconsin-Madison)
Dr
Susanna cappello
(Consorzio RFX)
Dr
V Davydenko
(Budker Institute of Nuclear Physics)
Dr
Vladimir Mirnov
(University of Wisconsin - Madison)
Dr
W Bergerson
(UCLA)
Weixing ding
(UCLA)
