Millimeter-wave receiver design for plasma diagnostics

Scattered millimeter waves entering from the collective Thomson scattering diagnostic at ASDEX Upgrade fusion device are generally elliptically polarized. In order to convert the millimeter waves to linearly polarized waves (required for the detector), birefringent window assemblies (sapphire) have been developed to replace grooved metal mirrors. This allows a significantly more compact receiver design which is less susceptible to misalignment. The setup has been tested and implemented at ASDEX Upgrade.