Détection de quench et comportement en cas de quench dans les systèmes magnétiques d'ITER

Le quench d'un système magnétique d'ITER est une transition irréversible d'un conducteur, de l'état supraconducteur à l'état normal résistif. Cette zone normale se propage le long du câble au cours du temps, en dissipant une grande quantité d'énergie. La détection se doit d'être suffisamment rapide afin de permettre une décharge de l'énergie magnétique et éviter un endommagement permanent du système. La détection primaire de quench d'ITER est basée sur la détection de la tension due au quench, qui est le moyen le plus rapide. L'environnement magnétique perturbé pendant le scenario plasma rend la détection de cette tension très difficile, à cause des hautes tensions inductives qu'il génère dans les bobinages. En conséquence, des compensations de tension sont nécessaires afin de discriminer la tension résistive due au quench.Une solution conceptuelle de la détection de quench basée sur la mesure des tensions est proposée pour les trois grands systèmes magnétiques d'ITER. Pour ceci, une méthodologie claire est développée, incluant le calcul classique selon le critère du point chaud, l'étude de la propagation de quench grâce au code commercial Gandalf, et l'estimation des perturbations inductives, grâce au développement du code TrapsAV. Des solutions adaptées sont proposée pour ces systèmes ainsi que les paramètres de cette détection, qui sont le seuil de détection (entre 0.1 V et 0.55 V) et le temps de discrimination (entre 1 s et 1.2 s). Les valeurs choisies, et en particulier le temps de discrimination, sont suffisamment élevées pour garantir la fiabilité du système, et pour éviter le déclenchement intempestif de décharges rapides non nécessaires.The quench of one of the ITER magnet system is an irreversible transition from superconducting to normal resistive state, of a conductor. This normal zone propagates along the cable in conduit conductor dissipating a large power. The detection has to be fast enough to dump out the magnetic energy and avoid irreversible damage of the systems. The primary quench detection in ITER is based on voltage detection which is the most rapid detection. The very magnetically disturbed environment during the plasma scenario, makes the voltage detection particularly difficult, inducing large inductive components in the coils and voltage compensations have to be designed to discriminate the resistive voltage associated with the quench. A conceptual design of the quench detection based on voltage measurements is proposed for the three majors magnet systems of ITER. For this, a clear methodology was developed. It includes the classical hot spot criterion, the quench propagation study using the commercial code Gandalf and the careful estimation of the inductive disturbances by developing the TrapsAV code.Specific solutions have been proposed for the compensation in the three ITER magnet systems and for the quench detection parameters which are the voltage threshold (in the range of 0.1 V- 0.55 V) and the holding time (in the range of 1 -1.4 s). The selected values, in particular the holding time, are sufficiently high to ensure the reliability of the system and avoid fast safety discharges not induced by a quench which is a classical problem

Selection of a quench detection system for the ITER CS magnet

26th Symposium on Fusion Technology (SOFT), Porto, PORTUGAL, SEP 27-OCT 01, 2010International audienceAt variance with most of the existing superconducting systems operating in the world, the ITER central solenoid (CS) magnet is a fast pulsed system. This peculiarity creates a specific situation regarding the quench detection system, as a small resistive signal associated with a quench has to be discriminated from the high inductive signals imposed by the plasma scenario. The quench detection is based on an inductive compensation built from three adjacent double pancakes. The ITER protection rules for a superconducting magnet impose to respect the so-called maximum hot spot temperature criterion of 250 K in the quenched cable at the end of the fast discharge. A careful analysis of the residual inductive signals in the detection voltage shows that a blanking of the quench detection cannot be avoided during the early times of the plasma discharge (i.e. during 3.5 s). It is demonstrated that this blanking is, however, acceptable while fulfilling the hot spot criterion because the plasma initiation phase (PIP) is very similar to a fast safety discharge and corresponds to a fast decrease of the modules currents, which is favourable for the magnet protection. (C) 2011 Elsevier B.V. All rights reserved

The 16 T Dipole Development Program for FCC and HE-LHC

A future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb 3 Sn technology, are being pursued in Europe and in the U.S. In these programs, cos-theta, block-type, common-coil, and canted-cos-theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs

The 16 T dipole development program for FCC and HE-LHC

International audienceA future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb$_3$Sn technology, are being pursued in Europe and in the U.S. In these programs, cos-theta, block-type, common-coil, and canted-cos-theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs

The 16 T Dipole Development Program for FCC and HE-LHC

A future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb3Sn technology, are being pursued in Europe and in the U.S. In these programs, cos-theta, block-type, common-coil, and canted-cos-theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs