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

A method to deduce local values of plasma emissivity from chord measurements has been developed and tested using data from a 30 detector 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 algebraically determine the distribution of the detector signals, and solves some drawbacks of the currently available tomography techniques. This method is especially suited for stellarator devices in which plasma cross sections are markedly noncircular and change as a function of the toroidal angle