Active control of the plasma current profile on JET experiments
The interplay occurring between the magnetic shear, the plasma rotation and the bootstrap current profile, to get and sustain an internal transport barriers (ITB), makes mandatory the presence of an active control of both current density and the pressure profile. So far the most used strategy to obtain high performance ITB has been the optimization of the current density profile early in the discharge by combining the skin effect with a pre-programmed off-axis non-inductive currents. The stepping up of the Neutral Beam (NBI) during this phase provides the necessary input of external momentum and auxiliary heating. On JET it has already been shown the possibility of a closed loop real-time control of parameters characterizing the pressure profile in ITB discharges. Moreover preliminary experiments have shown the possibility to control a set of families of target safety factor profile (q). Here we will report the results of controlling the q profile in two different plasma configurations: with and without an ITB. In the first scenario only Lower Hybrid (LHCD) is used to control three different classes of target q profile in absence of the ITB. In the second scenario a combination of the NBI, of the ion cyclotron resonant heating (ICRH) and of the LHCD is used to control the current density profile in an ITB configuration. The goal was achieved by using a technique well adapted to control a distributed parameter system such as a set of radial profiles and that it is based on a truncated singular value decomposition (TSVD) of a model integral operator (diffusion-like).
Bibliographic Reference: An oral paper given at: 30th EPS Conference on Controlled Fusion and Plasma Physics Organised by: European Physical Society Held at: St. Petersburg, Russia, 7-11 July 2003 Paper No. P-2.88 Proceedings available online at: http://eps2003
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel:+33-4-42257001; Fax:+33-4-42256421 E-mail: email@example.com
Record Number: 200317066 / Last updated on: 2003-10-27
Original language: en
Available languages: en