Near midplane scintillator-based fast ion loss detector on DIII-D

Abstract

A new scintillator-based fast-ion loss detector (FILD) installed near the outer midplane of the plasma has been commissioned on DIII-D. This detector successfully measures coherent fast ion losses produced by fast-ion driven instabilities (≤500 kHz). Combined with the first FILD at ∼45° below the outer midplane [R. K. Fisher, et al., Rev. Sci. Instrum. 81, 10D307 (2010) https://doi.org/10.1063/1.3490020.], the two-detector system measures poloidal variation of losses. The phase space sensitivity of the new detector (gyroradius rL ∼ [1.5–8] cm and pitch angle α ∼ [35°–85°]) is calibrated using neutral beam first orbit loss measurements. Since fast ion losses are localized poloidally, having two FILDs at different poloidal locations allows for the study of losses over a wider range of plasma shapes and types of loss orbits.