Tangential imaging for fluctuation studies

Tangential imaging is being pursued on TFTR as a method to study instabilities with high poloidal mode number m. These instabilities cannot be seen with conventional perpendicular viewing soft x-ray diode arrays because the emission is integrated along a line of sight. Computer simulations of tangential imaging indicate that excellent spatial resolution can be obtained. Prerequisites are (a) that the line of sight is nearly parallel to a magnetic field line at the point of closest approach to the center of the plasma, and (b) that there exists a steep gradient of the plasma radiation that is used for the measurements. The TFTR plans for a tangential, two-dimensional imaging, soft x-ray diode array will be outlined.