Confinement in electron heated plasmas in Wendelstein 7-X and ASDEX Upgrade; the necessity to control turbulent transport

Nuclear Fushion

article

M.N.A. Beurskens¹  C. Angioni¹  S. A. Bozhenkov¹  O. Ford¹  C. Kiefer¹  P. Xanthopoulos¹  Y. Turkin¹  J.A. Alcusón¹  J.P. Baehner¹  C. Beidler¹  G. Birkenmeier¹  E. Fable¹  G. Fuchert¹  B. Geiger²  O. Grulke¹  M. Hirsch¹  M. Jakubowski¹  H.P. Laqua¹  A. Langenberg¹  S. Lazerson¹  N. Pablant⁴  M. Reisner¹  P. Schneider¹  E.R. Scott²  T. Stange¹  A. von Stechow¹  J. Stober¹  U. Stroth¹  Th. Wegner¹  G. Weir¹  D. Zhang¹  A. Zocco¹  R.C. Wolf¹  H. Zohm¹ 

[1] Max-Planck Institut für Plasmaphysik;University of Wisconsin-Madison;Technical University of Denmark;Princeton Plasma Physics Laboratory, Princeton;Technische Universität Berlin

关键词: stellarator transport;    turbulent transport;    electron heating;    ion temperatureclamping;   

DOI  :  10.1088/1741-4326/ac36f1

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

In electron (cyclotron) heated plasmas, in both ASDEX Upgrade ( L -mode) and Wendelstein 7-X, clamping of the ion temperature occurs atT _i ∼ 1.5 keV independent of magnetic configuration. The ions in such plasmas are heated through the energy exchange power as {n}_{mathrm{e}}^{2}({T}_{mathrm{e}}-{T}_{mathrm{i}})/{T}_{mathrm{e}}^{3/2} , which offers a broad ion heating profile, similar to that offered by alpha heating in future thermonuclear fusion reactors. However, the predominant electron heating may put an additional constraint on the ion heat transport, as the ratioT _e/ T _i > 1 can exacerbates ITG/TEM core turbulence. Therefore, in practical terms the strongly 'stiff' core transport translates intoT _i-clamping in electron heated plasmas. Due to this clamping, electron heatedL -mode scenarios, with standard gas fueling, in either tokamaks or stellarators may struggle to reach high normalized ion temperature gradients required in a compact fusion reactor. The comparison shows that core heat transport in neoclassically optimized stellarators is driven by the same mechanisms as in tokamaks. The absence of a strongH -mode temperature edge pedestal in stellarators, sofar (which, like in tokamaks, could lift the clamped temperature-gradients in the core), puts a strong requirement on reliable and sustainable core turbulence suppression techniques in stellarators.

【 授权许可】

Unknown