The safety factor profile in the RFP plasma core from soft x-ray tomography

We report experimental results on the identification of rational surfaces in the Reversed Field Pinch (RFP) plasma core. The position of rational surfaces has been obtained from tomographic measurements of the m = 1 structure which develops during Quasi-Single Helicity (QSH) states. These results allow the estimate of the safety factor profile, which is measured for the first time in a RFP with plasma current ? 1 MA.