Speaker
Alessandro Fassina
(Consorzio RFX-CNR)
Description
RFX-mod RFP is now under shutdown and it is undergoing a deep modification in the plasma magnetic boundary, with changes in the vacuum vessel, first wall and stabilizing shell. A diagnostics upgrade is also foreseen; in particular, an improvement in the signal level of the main Thomson Scattering Diagnostics becomes crucial for the diagnostic operation in low density RFP and tokamak discharges.
Launching and reflecting optics for a double passage of the laser beam in the equatorial plane: a retroreflector is needed, as well as a manipulator for retroreflector substitution and precise positioning. Analysis of the expected energy density on the optics is presented; stray light generation, positioning issues and optical damage risk are examined. Moreover, beam retro-reflection allows in principle re-injection in the edge Thomson Scattering system, lying in another toroidal position; this possibility is analyzed focusing on the reflected beam profile and pointing stability.
Alone, laser beam recirculation can provide a doubling in the signal level, while a further 30% gain can be obtained maximizing the collection optics transmission: an alternative, simplified design featuring a 3 elements objective is presented and discussed, the major drawback being a non-planar image surface.
Primary author
Alessandro Fassina
(Consorzio RFX-CNR)
Co-author
Dr
Paolo Franz
(Consorzio RFX-CNR)
