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 as a constraint for reconstruction of the plasma current profile and q profile. A model current profile was used to compare the sensitivity of the equilibrium reconstruction using soft x-ray (SXR) image constraints to motional Stark effect (MSE) constraints. The deviation in the χ2 of the fit versus 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 the internal flux surfaces on PEGASUS. One diagnostic consists of a series of vertically spaced, tangentially viewing linear detector arrays. Another design using a two-dimensional pinhole camera for a soft x-ray image of the plasma is also being evaluated. copyright 1999 American Institute of Physics