The Capability of the Ion Cyclotron Emission Diagnostic on Observing High-K Waves in DIII-D.

At the DIII-D tokamak, the Ion Cyclotron Emission (ICE) diagnostic is used to monitor plasma waves within the ion cyclotron frequency regime, f < 500 MHz, using an array of loop antennas placed throughout the vessel walls. This diagnostic allows for passive monitoring of fast ions which are products of burning plasmas that form from fusion reactions or neutral beam injection (NBI). During the FY24 campaign, a four-element ICRF antenna array was repurposed to be a part of the ICE diagnostic. The 18.5 cm center-to-center toroidal spacing of the four elements in the array allows for the observation of high-k toroidal modes up to a nominal observable mode of |n|~ 56. Mode observations of Ion Cyclotron Emission from NBI were verified between the ICRF antenna array and the single loop antennas. Further analysis of the mode and polarization of these plasma waves will be done at high frequency to study nonlinear interactions of fast ions such as with the daughter waves of Parametric Decay Instability produced by the Helicon current drive. This work is supported by US DOE under DE-FC02-04ER54698 and grant # DE-SC0020337.