Mechanical Design of the NSTX High-k Scattering Diagnostic

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 lambda=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 (rhoap.1) or near the edge (rhoap.8). 150 feet of carefully aligned corrugated waveguide was installed for injection of the probe beam and collection of the scattered signal into the detection electronics