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Gradient length driven electron heat transport study in modulated electron cyclotron heating FTU tokamak (Articolo in rivista)

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Gradient length driven electron heat transport study in modulated electron cyclotron heating FTU tokamak (Articolo in rivista) (literal)

Anno

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Alternative label

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) (2002)
Gradient length driven electron heat transport study in modulated electron cyclotron heating FTU tokamak
in Nuclear fusion
(literal)

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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) (literal)

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Studio pubblicato su rivista scientifica internazionale ad alta diffusione con Impact Factor nel 2002 pari a 2.302 (literal)

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Rivista

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Risultati sperimentali e modello interpretativo dell'esistenza di un valore critico del gradiente di temperatura per la transizione da un regime laminare a turbolento per la diffusione del calore in un tokamak (literal)

Note

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(1) IFP CNR, EURATOM/ENEA-CNR Assoc., Milano, Italy (2) Dip. Fisica, UNIMI, Milano, Italy (3) CRE, EURATOM-ENEA Assoc, Frascati, Italy (literal)

Titolo

Gradient length driven electron heat transport study in modulated electron cyclotron heating FTU tokamak (literal)

Abstract

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. (literal)

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