Equilibrium-based iterative tomography technique for soft x-ray in stellarators

This paper reports on a method to deduce local values of plasma emissivity from chord measurements that has been developed and tested using data from a 30 detect or soft X-ray array in the Wendelstein 7A stellarator. This technique, based on the calculated distribution of toroidal magnetic flux as the initial guess for the plasma emissivity, uses an iterative scheme to determine algebraically the distribution of the detector signals, and solves some drawbackds of the currently available tomography techniques This method is especially adequate for stellarator devices where plasma cross sections are markedly noncircular and change as a function of the toroidal angle