Open-loop non-linear Simulations with MAXFEA code






Screen print from Maxfea.





In modern tokamaks vertically elongated plasma cross sections are employed to reach better performances. Such configurations have the drawback of being unstable, requiring therefore an active feedback control system to keep the plasma in equilibrium.

Plasma movements are stabilized on the fast time scale by the image currents induced in the passive structures. At this regime no active control seems feasible since the instability growth time is of the order of few micro seconds. On a longer time scale the plasma is still unstable since, as the induced currents decay, the plasma drifts from the original position. However, on such a slower time scale, tipically of the order of hundreds of milli seconds, active control is possible. Open loop analysis are needed to optimize the stabilizing effect of the conducting structures surrounding the plasma and to examine the stability parameters of the configuration.

The analysis are computed by the MAXFEA code written by P. Barabaschi. The code solves for the free boundary Grad-Shafranov problem, a two dimensional formulation of the ideal Magneto Hydro Dinamics (MHD) equilibrium equations. In this approach plasma pressure and current density profiles are derived from experimental data and described by means of two main parameter, the internal plasma inductance li and the Poloidal Beta ßp. The plasma equations are coupled with the circuits equations for the active and passive conductors surrounding the plasma region. The numerical technique employed to compute the solution is based on the finite-element formulation. 
 

Related pubblications

  1. M. Cavinato, G. Marchiori, A. Beghi, D. Ciscato, and A. Portone, "ITER scenario simulations with a non-linear MHD equilibrium code,'' in Proc. of the 20th Symposium on Fusion Technology (B. Beaumont, P. Libeyre, B. de Gentile, and G. Tonon, eds.), vol. 1, (Marseille, France), pp. 587-590, September 1998.
  2. M. Cavinato, A. Kavin, V. Lukash, and R. Khayrutdinov, "Non-linear simulations by numerical Magneto Hydro Dynamics equilibrium codes in ITER-FEAT," submitted to the IEEE Conf. on Control Appl. 2000.

 
 

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