Gradient length driven electron heat transport study in modulated electron cyclotron heating FTU tokamak
| Autor: | G. Bracco, Alessandro Bruschi, S. Podda, Carlo Sozzi, F. De Luca, S. Cirant, A. Jacchia, O. Tudisco, P. Buratti |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | Nuclear fusion 42 (2002): 1116–1123. doi:10.1088/0029-5515/42/9/310 info:cnr-pdr/source/autori:Jacchia A. (1); De Luca F. (2); Cirant S. (1); Sozzi C. (1); Bracco G. (3); Bruschi A. (1); Buratti P. (3); Podda S. (3); and Tudisco O. (3)/titolo:Gradient length driven electron heat transport study in modulated electron cyclotron heating FTU tokamak/doi:10.1088%2F0029-5515%2F42%2F9%2F310/rivista:Nuclear fusion/anno:2002/pagina_da:1116/pagina_a:1123/intervallo_pagine:1116–1123/volume:42 |
| ISSN: | 0029-5515 |
| DOI: | 10.1088/0029-5515/42/9/310 |
| Popis: | Perturbative and steady-state heat transport of FTU tokamak in current ramp-up discharges are investigated by means of modulated electron cyclotron heating (MECH). Perturbative and steady-state transport experiments are coherent with an electron heat transport which switches from low to high values when electron temperature gradient length reaches a threshold value 1/L_Tc. The threshold value 1/L_Tc is shown to be proportional to the ratio s/q. The experimental findings are compared to predictions of an empirical model based on the assumption of a threshold gradient length, L_Tc (1/L_T = |grad Te/Te|), in the electron temperature Te below which electron thermal diffusivity, chi_e, switches from low to high values. Plasma responses to steady state and MECH are modelled assuming the electron diffusivity as chi_PB = chi_0 + alpha Te^(3/2) (1/L_T - 1/L_Tc)^(1/2); here Te^(3/2) reflects the gyro-Bohm assumption, chi_0 represents the heat transport for 1/L_T < 1/LT_c and the term (1/L_T - 1/L_Tc)^(1/2), which sets in for 1/L_T > 1/L_Tc , mimics an extra transport possibly due to electron temperature gradient (ETG) modes. In agreement with ETG threshold 1/L_Tc is shown to be correlated with the magnetic shear s. |
| Databáze: | OpenAIRE |
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