Using the Tore Supra infrared thermography diagnostics, a new real time feedback control has been successfully implemented to maximize additional RF power while preventing plasma facing components (PFCs) from overheating and damage. As a first step, a thermography feedback control has been used to detect and extinguish electric arcs on lower hybrid current drive (LHCD) launchers. Secondly, heating sources on PFCs have been identified highlighting the role of the power from each ion cyclotron resonance heating (ICRH) antenna and LHCD launcher and the interactions between them. A new feedback control algorithm was developed to control the additional power. The real time feedback control of PFC temperatures which makes part of an integrated feedback controller, is a reliable tool routinely used as a basic protection system. Furthermore, it has proven its capability to operate in parallel with other control schemes such as the current profile control.

RF heating optimization on Tore Supra using feedback control of infrared measurements

Progress in real-time feedback control systems in RFX

Plasma control systems relevant to ITER and fusion power plants

The Tore Supra tokamak is devoted to long-duration, high-performance plasma research. The real-time measurements and control (RTMC) system has been developed to address the basic tokamak controls, such as plasma equilibrium and density control. Over the years, more and more sophisticated and demanding controls have been implemented, allowing the improvement of plasma performance and machine protection. This includes current profile control to enhance the performance and to avoid magnetohydrodynamic instabilities, infrared monitoring of plasma facing components to prevent overheating, and disruption detection and mitigation techniques. Most of these improvements are relevant to the plasma operation in a full steady-state regime. This paper describes the present status of the Tore Supra RTMC system, detailing recent progress and highlighting the advantages of the various control schemes implemented so far.

Plasma Control in Tore Supra

Cette these traite de la resolution theorique et constructive de problemes inverses pour des equations de diffusion isotropes dans des domaines plan simplement et doublement connexes. A partir de donnees de Cauchy (potentiel, flux) disponibles sur une partie de la frontiere du domaine, il s’agit de retrouver ces quantites sur la partie du bord ou l’on ne dispose pas d’information, ainsi qu’a l’interieur du domaine. L’approche mise au point consiste a considerer les solutions de l’equation de diffusion comme les parties reelles des solutions complexes d’une equation de Beltrami conjuguee. Ces fonctions analytiques generalisees d’un type particulier permettent de definir des classes de Hardy, dans lesquelles le probleme inverse est regularise en etant reformule comme un probleme de meilleure approximation sous contrainte (ou encore probleme extremal borne, d’adequation aux donnees). Le caractere bien pose de celui-ci est assure par des resultats d’existence et de regularite auxquels s’ajoutent des proprietes de densite a la frontiere. Une application au calcul de la frontiere libre d’un plasma sous confinement magnetique dans le tokamak Tore Supra (CEA-IRFM Cadarache) est proposee. La resolution du probleme extremal a partir d’une base de fonctions adaptees (harmoniques toroidales) fournit un critere permettant de qualifier les estimations de la frontiere plasma. Un algorithme de descente permet de le faire decroitre, en ameliorant l’estimation de la frontiere. Cette methode, qui ne requiert pas d’integration de l’equation dans le domaine, fournit de tres bons resultats et semble appelee a connaitre des extensions pour d’autres tokamaks tels que JET et ITER.

https://tel.archives-ouvertes.fr/tel-00643239/document

B. Couturier

Papers

The real time plasma control system of Tore Supra