Cross-calibrating Spatial Positions of Light-viewing Diagnostics using Plasma Edge Sweeps in DIII-D
Authors: W.M. Solomon, K.H. Burrell, P. Gohil, R. Groebner, and D. Kaplan
Date of PPPL Report: July 2003
Submitted to: Review of Scientific Instruments
An experimental technique is presented that permits diagnostics viewing light from the plasma edge to be spatially calibrated relative to one another. By sweeping the plasma edge, each chord of each diagnostic sweeps out a portion of the light emission profile. A nonlinear least-squares fit to such data provides superior cross-calibration of diagnostics located at different toroidal locations compared with simple surveying. Another advantage of the technique is that it can be used to monitor the position of viewing chords during an experimental campaign to ensure that alignment does not change over time. Moverover, should such a change occur, the data can still be cross-calibrated and its usefulness retained.