Instability and transport driven by electron temperature gradient close to critical

Abstract

Electron transport induced by ETG turbulence is fonnulated using the databases of the calculations of parameter survey. Then , the scaling for transport was obtained and is shown to be in line with experimental observations.Reference:

Short wavelength electron temperature gradient instability in toroidal plasmas

“…One can also expect the linear critical temperature gradient is just same as the onset condition to excite the ETG streamers. Therefore, recent studies 6,7 have been performed on the ETG instabilities and the results seem to be consistent with some experimental observations. 8 At the same time, however, some experimental observations 9 seem to agree well with the model based on other instabilities, for example, the trapped electron mode-ion temperature gradient ͑ITG͒ driven mode.…”

“…Obviously, in the k region from 0.2 to 0.8, the minimum ͑R / L Te ͒ c exists with a value about 4.5, which is consistent with the results from conventional ETG mode. 6,7 When k increases from 0.8 to 1.6, ͑R / L Te ͒ c increases with k rapidly. However, it seems to be another "substeady-state" region for k from 1.6 to 2.2, where ͑R / L Te ͒ c is about 12.5 and slightly depending on k .…”

“…This character is quite similar with that of the conventional ETG mode, but the value of ͑R / L Te ͒ c for the SWETG mode is rather higher than that for the conventional ETG mode. 6 Generally, we should choose a set of k s in the fastest growing regions and find the minimum critical threshold. However, there is no explicit boundary between the conventional and short wave ETG mode.…”

Electron transport and the critical temperature gradient

“…Linear kinetic stability theory for electron and ion temperature gradient (ETG and ITG) instabilities yields a complicated set of growth-rate formulas, depending on the dominant plasma regime, with respect to the trapped particle collisionality, and the magnetic shear profile for tokamaks [1][2][3][4][5][6]. In addition, fluid simulations suggest that self-generated sheared flows may shift the effective critical gradient from the linear value [7,8].…”

“…Jenko et al [11] give a complex formula given in Table 1 for the switching from density gradient to shear control of the critical gradient. Dong et al [3] give a complex set of functions describing the details of the shear and q dependence of the critical gradient and the growth rates derived from the integral eigenvalue problem for ETG drift waves and discuss the relation to the Ryter et al [20].…”