Comparing DINA code simulations with TCV experimental plasma equilibriumresponses

Abstract

The DINA nonlinear time-dependent simulation code has been validated againstan extensive set of plasma equilibrium response experiments carried out on theTCV tokamak. Limited and diverted plasmas are found to be well modelled duringthe plasma current flat top. In some simulations the application of thepoloidal field coil voltage stimulation pulse sufficiently changed the plasma equilibriumthat the vertical position feedback control loop became unstable. Thisbehaviour was also found in the experimental work, and cannot be reproducedusing linear time-independent models. A single null diverted plasma dischargewas also simulated from start-up to shut-down and the results were found toaccurately reproduce their experimental equivalents. The most significantdifference noted was the penetration time of the poloidal flux, leading to adelayed onset of sawtoothing in the DINA simulation. The complete set offrequency stimulation experiments used to measure the open-loop tokamak plasmaequilibrium response was also simulated using DINA and the results wereanalysed in an identical fashion to the experimental data. The frequencyresponse of the DINA simulations agrees with the experimental results.Comparisons with linear models are also discussed in order to identify areas of goodand only occasionally less good agreement.