Abstract Details
| status: | file name: | submitted: | by: |
|---|---|---|---|
| approved | abs_sherwood.pdf | 2019-02-21 18:23:17 | Ben Zhu |
Abstracts
Author: Ben Zhu
Requested Type: Pre-Selected Invited
Submitted: 2019-02-21 18:22:41
Co-authors: M.Francisquez, B.N.Rogers, X.Xu
Contact Info:
Lawrence Livermore National Laboratory
7000 East Avenue
Livermore, CA 94550
USA
Abstract Text:
A new particle pinch mechanism other than the Ware effect [1], thermal-diffusion [2] and turbulence equipartition theory [3] has been observed in our global tokamak edge simulations with GDB code [4] – a 3D drift-reduced Braginskii based electromagnetic turbulence model. In this study, radial simulation domain spans from the closed flux region to the SOL (0.8<r/a<1.1 in normalized units) and the simulation is initialized with monotonically decreasing tempera- ture profiles and flat density profile. A flux-driven heat source ST is located on the core side (r/a<0.84) in order to maintain a target Te,i at the boundary. Meanwhile, a Gaussian shape particle source Sn with 1 cm width is located near the LCFS (0.96<r/a<1.05). Figure 1 shows time evolution of the flux surface averaged radial density profile for this 12 ms run. Immediately after the SOL particle source is turned on at t≃0.2 ms, a strong inward (up-gradient) particle flux in the closed flux region away from the particle sourcing zone appears. At t≃4 ms, density profile inside the LCFS flattens and at t≃8 ms a central-peaked quasi-steady density profile is reached. Analysis shows that the net inward particle flux is due to the inboard-outboard asymmetric radial component of E×B drift, or, the up-down asymmetric electrostatic potential φ. As discussed in [5], up-down asymmetric φ is mainly originated from contribution of the ion transverse heat flux as predicted by neoclassical theory. Once the transverse heat flux term is turned off (e.g., no up-down asymmetry driver) at t>8.5 ms, radial density profile starts to relax and are no longer central-peaked.
[1] A. Ware, Phys. Rev. Lett. 25, 15 (1970)
[2] B. Coppi and C. Spight, Phys. Rev. Lett. 41, 551 (1978)
[3] M. B. Isichenko, A. V. Gruzinov and P. H. Diamond, Phys. Rev. Lett. 74, 4436 (1995) [4] B. Zhu, M. Francisquez and B. Rogers, Comp. Phys. Comm. 232, 46 (2018)
[5] B. Zhu, M. Francisquez and B. Rogers, Nucl. Fusion 58 106039 (2018)
Comments:
