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The electron thermal diffusivity Chi(TTP) has been determined using time-to-peak method (TTP), applied to the heat pulse that propagates following sawtooth crashes. More than 300 FTU ohmic discharges have been analysed. All discharges were in deuterium with a magnetic field of 6 T. The temperature perturbation induced by sawteeth has been measured by a 12 channel polychromator covering 2/3 of plasma diameter. The noise level of polychromator channels varies from a few eV to 15 eV, and many sawteeth (up to 100 in the worst case) during a steady state phase of the discharges, had to be added in order to reach a good signal to noise ratio. Both low and high field side channels have been used for the analysis. Polychromator signals have been calibrated against ECE Michelson spectra. The values obtained have been tested by numerical simulation with fixed boundary condition. The Chi(TTP) range from 1 to 5 times Chi(PB). The Chi(TTP)/Chi(PB) ratio decreases with density and increases with temperature gradient in contrast both with a model that would predict a constant ratio, and with the Rebut-Lallia model that would predict a decreasing trend of the ratio with the temperature gradient.

Additional information

Authors: BRACCO G, ENEA, Centro Ricerche Energia Frascati, Roma (IT);BURATTI P, ENEA, Centro Ricerche Energia Frascati, Roma (IT);TUDISCO O, ENEA, Centro Ricerche Energia Frascati, Roma (IT)
Bibliographic Reference: Paper presented: Workshop on Local Transport Studies in Fusion Plasmas, Varenna (IT), August 30 - September 3, 1993
Availability: Available from (1) as Paper EN 37904 ORA
Record Number: 199311436 / Last updated on: 1994-11-28
Original language: en
Available languages: en