Collective Thomson Scattering System combined with the MIR system in KSTAR

Abstract

A four-channel collective Thomson scattering (CTS) system being developed for electron-gyroscale turbulence study will provide simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm-1. Due to upcoming new neutral beam injection (NBI) system, the microwave imaging reflectometer (MIR) [1, 2], which was developed for ion-gyroscale fluctuation measurement, has to be rearranged and the space has to be shared with the CTS system [3]. In order to effectively combine both the optical systems for the MIR and CTS system, a large aperture beam splitter will be employed for splitting the 300 GHz O-mode beam for the CTS system from the 78-96 GHz X-mode beam for the MIR system. Design characteristics of the optical systems and laboratory test result are presented in this paper. The modified MIR and new CTS system will be installed prior to the 2018 KSTAR campaign. This work is supported by the NRF of Korea under contract numbers, NRF-2015M1A7A02002627 and NRF-2014M1A7A1A03029865, and the Ministry of Science, ICT and Future Planning under the KSTAR project.