A simplified poloidal beta response model in JET

A simple but reliable poloidal beta response model is derived from Goldstonʹs scaling law and successfully applied to a large number of plasma configurations and pulses in the JET tokamak (plasma current up to 2.7 MA, poloidal beta up to 2.1, internal inductance from 0.6 to 1.3, elongation from 1.3 to 1.8). It provides a good prediction of both transient phase and steady state conditions without the need of an auxiliary pulse. The model, although non linear as a function of the input power, is actually linear if the input quantity is the square root of the overall input power divided by the plasma current. The model can then be used for the design of an integrated feedback controller that simultaneously regulates plasma current, position, shape and poloidal beta.