ELECTRON-DENSITY PROFILE RECONSTRUCTION FROM MULTICHANNEL MICROWAVE INTERFEROMETER DATA AT W7-AS

A multichannel microwave interferometer has been built for the W7-AS f usion experiment in order to study temporal phenomena in plasma densit y. For this reason, electron density profile reconstruction methods ba sed on regularization functionals were studied. Simulations showed, th at the minimum Fisher-information approach (adapted from tomography) g ives better results than the maximum entropy approach. This is due to the fact, that in the minimum Fisher-information method the reconstruc ted distribution is inherently assumed to be continuous, whereas the m aximum entropy method the distribution is assumed to be noncontinuous. The profiles reconstructed from multichannel interferometer data are in good agreement with the profiles measured by other diagnostic syste ms. (C) 1997 American Institute of Physics. [S0034-6748(97)00611-4].