TITLE
	Experiments about active control of the turbulence in the SOL of the tokamak Castor
	
AUTHOR
	Pascal DEVYNCK (in collaboration with G. Bonhomme, E. Martines, J. Stöckel, G. Van Oost, I. Voitsekhovitch, J. Adámek, F. Doveil, I. Duran, J. Gunn, M. Hron)

ABSTRACT 
	We will present preliminary results of recent experiments about active 
	control of turbulence in the tokamak Castor. The experiments based on 
	excitations of spatio-temporal electric fields are performed in the Scrape 
	off Layer of Castor (region in the shadow of a limiter) with the help of a 
	poloidal ring of 32 electrodes covering the whole perimeter. Each electrode 
	is equipped with a flush mounted probe to allow feedback operation. The 
	signals propagate along the magnetic field lines and their effect can be 
	detected on a second ring of probes located 180° toroidally away from the 
	first one. We monitor the changes of both the turbulence and the turbulent 
	particle flux. Three methods have been investigated so far: The open loop 
	which aims at forcing the turbulence in a selected poloidal mode, the 
	multipoint TDAS method which shrinks the turbulence towards an existing 
	dominant poloidal mode and the standard feedback technique. Some results 
	about these experiments will be presented and the nature of the turbulence, 
	the existence of a dominant poloidal mode number, the geometrical 
	effects linked to the magnetic topology will be discussed.