GTC Related Movies
Linear properties of reversed shear Alfven eigenmodes in DIII-D tokamak, W Deng, Z Lin, I Holod, Z Wang, Y Xiao, and H Zhang, submitted to Nuclear Fusion (2011).
Verification and validation of gyrokinetic simulation of Alfvén eigenmodes in DIII-D tokamak, D. A. Spong, E. Bass, W. Deng, W. Heidbrink, Z. Lin, B. Tobias and M. A. Van Zeeland, in preperation (2012).
The movie can be downloaded (file size 1.2MB) from: http://phoenix.ps.uci.edu/gtc/movies/rsaed3d.mp4
This movie shows the simulation results of the linear reversed shear Alfvén eigenmode (RSAE) excited by density gradient of fast ions in DIII-D tokamak discharge #142111. The left panel shows the evolution of the RSAE in the poloidal cross section in the GTC simulation. The mode rotates in the fast ion diamagnetic direction. The right panel shows the frequency and growth rate comparisons among the experiment and the simulations by GTC, GYRO, and TAEFL.
Turbulent transport of trapped electron modes in collisionless plasmas, Yong Xiao and Zhihong Lin, Phys. Rev. Lett. 103, 085004 (2009).
The movie can be downloaded (file size 16MB) from: http://phoenix.ps.uci.edu/zlin/movie/PRL2009.mp4
The movie shows that the CTEM turbulence eddies are predominantly microscopic (a few gyroradii) but with a significant component in the mesoscale (tens of gyroradii). The macroscopic, linear streamers (hundreds of gyroradii) are mostly destroyed by the zonal flow shearing. The mesoscale eddies form in a competing process between the breaking of the macroscopic streamers by the zonal flows and the merging of the microscopic eddies. The trapped electrons behave as fluid elements in the transport process, and their ballistic radial drifts across the mesoscale eddies drive a nondiffusive component in the electron heat flux. The nondiffusive electron heat flux, together with the turbulence spreading, leads to an electron heat conductivity dependent on the device size, i.e., a breaking of the gyro-Bohm scaling. The results were presented as an invited talk at the 2009 International Sherwood Fusion Theory Conference. This GTC simulation was the first petascale fusion simulation and was highlighted in a Reuters report on 07/29/2008, Researchers Run World’s Largest-Scale Fusion Energy Simulation on Cray Supercomputer.
Properties of microturbulence in toroidal plasmas with reversed magnetic shear, Wenjun Deng and Zhihong Lin, Phys. Plasmas 16, 102503 (2009).
The movie can be downloaded (file size 22M) from: http://phoenix.ps.uci.edu/wdeng/sherwood2010/ctem_rs.mp4
This video shows the evolution of a collisionless trapped electron mode (CTEM) turbulence in a tokamak plasma with reversed magnetic shear simulated by the global gyrokinetic toroidal code (GTC). The video has four panels: on the upper left panel is the poloidal contour plot of the electrostatic potential with the black ring indicating the q_min position; on the upper right panel is the radial profile of the flux-surface averaged electrostatic potential intensity; on the lower left panel is the radial profile of the zonal flow; on the lower right panel is the radial profile of the flux-surface averaged electrostatic field energy flow. The simulation starts with random noise. Then the linear CTEM eigenmode forms only in the positive shear region (r/a > 0.5) and grows exponentially in the linear stage. In the nonlinear stage, the amplitude saturates and the turbulence propagates into the negative shear region (r/a < 0.5), so in the end the turbulence occupies the whole volume and no internal transport barrier (ITB) is formed. More details can be found in the paper linked above and the slides ( http://phoenix.ps.uci.edu/wdeng/sherwood2010/rs_sherwood10.pdf) presented as an invited talk at the 2010 International Sherwood Fusion Theory Conference.
Turbulent Transport Reduction by Zonal Flows: Massively Parallel Simulations, Z. Lin, T. S. Hahm, W. W. Lee, W. M. Tang, and R. B. White, Science 281, 1835 (1998).
The movie can be downloaded (file size 128MB) from: http://phoenix.ps.uci.edu/zlin/movie/Science98.avi
GTC simulations show turbulence self-regulation by spontaneously-generated E x B zonal flows, which are radially varying but toroidally and poloidally symmetric flows. The shear of the fluctuating zonal flows breaks up the radially elongated eigenmodes of toroidal drift waves, and reduces the turbulence transport level. The simulation results support the view that the shearing effect of E x B flows is the most likely mechanism responsible for the transitions to various forms of enhanced confinement regimes observed in magnetically confined plasmas. The simulations have inspired worldwide theoretical studies and experiment search of the zonal flows in fusion experiments. The GTC simulation was published in a 1998 Science paper, which has received the most citations for all magnetic fusion research papers published since 1996.