Application of x-ray imaging to current profile measurements in the PEGASUS experiment

For low-aspect ratio toroidal devices, flux shape information can be used a s a constraint for reconstruction of the plasma current profile and q profi le. A model current profile was used to compare the sensitivity of the equi librium reconstruction using soft x-ray (SXR) image constraints to motional Stark effect (MSE) constraints. The deviation in the chi(2) of the fit ver sus current profile was similar in both cases, showing that the SXR data is as good a constraint on the equilibrium as MSE information. There are two soft x-ray imaging systems under consideration to determine the shape of th e internal flux surfaces on PEGASUS. One diagnostic consists of a series of vertically spaced, tangentially viewing linear detector arrays. Another de sign using a two-dimensional pinhole camera for a soft x-ray image of the p lasma is also being evaluated. (C) 1999 American Institute of Physics. [S00 34-6748(99)57801-5].