Conditions and behaviour related to non-local electron heat transport on TFTR

Abstract

A database of 70 distinct and randomly collected cold pulse cases from TFTR is analysed. Observations show a striking parameter regime cut-off for the presence of non-local transient transport and coincident magnetohydrodynamic (MHD) (1/1 mode) activity, as well as for changes in the radial speed of the non-local transport effect and changes in the sawtooth period. A significant link is demonstrated between electron heat transport and MHD properties through observation of a common cut-off in the parameter ne(0)/Te(0)1/2 and a common threshold for changes in the radial speed of propagation and in the sawtooth period. Auxiliary heating (via energetic neutral beams) destroys whatever process is responsible for the non-local transport effect, unless the discharge contains significant amounts of injected tritium. These observations are evidence, albeit circumstantial, that changes in the propagation of some MHD related phenomenon are responsible for a large fraction of the electron heat transport. This propagation is then probably a function of ne(0)/Te(0)1/2, ion mass and, possibly, beam power. An analysis of ohmic cases indicates the non-local transport effects that occur when the electrons are collisionally thermally decoupled from the ions.