Mechanical Design of the NSTX High-k Scattering Diagnostic
Authors: R. Feder, E. Mazzucato, T. Munsat, H. Park, D.R. Smith, R. Ellis, G. Labik, and C. Priniski
Date of PPPL Report: September 2005
Presented at: the Twenty-First Symposium on Fusion Engineering (SOFE2005), 26 - 29 September 2005, Knoxville, Tennessee USA.
The NSTX High-k Scattering Diagnostic measures small-scale density fluctuations by the heterodyne detection of waves scattered from a millimeter wave probe beam at 280 GHz and λ=1.07 mm. To enable this measurement, major alterations were made to the NSTX vacuum vessel and Neutral Beam armor. Close collaboration between the PPPL physics and engineering staff resulted in a flexible system with steerable launch and detection optics that can position the scattering volume either near the magnetic axis (ρ ≈ .1) or near the edge (ρ ≈ .8). 150 feet of carefully aligned corrugated waveguide was installed for injection of the probe beam and collection of the scattered signal in to the detection electronics.