A 1‐mm collective scattering experiment for DIII‐D (abstract)

A 1‐mm collective scattering system is under construction for installation on DIII‐D in May/June of 1988. The main objective of the experiment is to extend the recent TEXT work1 on the role of confinement damaging ηi modes to a more CIT/reactor relevant plasma with a divertor, H‐mode, etc. In order to resolve these modes, which propagate in the ion‐diamagnetic drift direction, both spatial resolution and a heterodyne detection capability are required. Spatial resolution will be obtained by operating at λ≊1 mm using both a twin frequency optically pumped FIR laser and a phase‐locked carcinotron. One of the large midplane ports on DIII‐D will be used to reflect a horizontal probe beam off the graphite tiles on the inner wall. This arrangement will allow for scattering angles of up to 18° from the plasma center. This work was supported by U.S. DOE Contract No. DE‐FG03‐86ER53225.