Conventional, single view interferometer and polarimeter imaging diagnostics require greater machine access than will generally be available in future tokamak devices. Alternative approaches, such as the utilization of fan beams, are preferred for these devices. Below is an illustration of an interferometer and polarimeter diagnostic for ITER.

ITER diagnostic
  • Hollow circular oversized waveguide is utilized to deliver FIR radiation to the small transmitting horns.

  • Each elliptically polarized FIR fan beam operates at a slightly different frequency, allowing data to be collected simultaneously from both sources utilizing a single array of receivers.

  • The radiation issuing from each source is collected by a array of small horns positioned within the blanket material, then directed along suitably shielded rectangular overmoded waveguide.

  • If the emitters are located on the outboard side of the tokamak, the first wall may be utilized as a mirror to reflect fan beams back onto the receiver array.

  • Thin ceramic windows (composed of SiC) keep plasma ash away from the interior surfaces of all horns.

  • For more information, contact Ross Geck at geck@ece.ucdavis.edu.