Design and development of the ITER CTS diagnostic

¹ Technical University of Denmark, Department of Physics , 2800 Kgs. Lyngby Denmark
² Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Univ., Lisboa Portugal
³ Technical University of Denmark, Center for Nuclear Technologies , 4000 Roskilde, Denmark
⁴ IDMEC, Instituto Superior Técnico, Univ. Lisboa, Lisboa, Portugal
⁵ Fusion for Energy 08019 Barcelona, Spain
⁶ ITER Organisation 13115 Saint Paul Lez Durance, France

^* Corresponding author: sbko@fysik.dtu.dk

Published online: 25 March 2019

Abstract

The Collective Thomson Scattering (CTS) diagnostic will be a primary diagnostic for measuring the dynamics of the confined fusion born alpha particles in ITER and will be the only diagnostic for alphas below 1.7 MeV [1]. The probe beam of the CTS diagnostic comes from a 60 GHz 1 MW gyrotron operated in a ~100 Hz modulation sequence. In the plasma, the probing beam will be scattered off fluctuations primarily due to the dynamics of the ions. Seven fixed receiver mirrors will pick up scattered radiation (the CTS signal) from seven measurement volumes along the probe beam covering the cross section of the plasma. The diagnostic is planned to provide a temporal resolution of ~100 ms and a spatial resolution of ~a/4 in the core and ~a/20 near the plasma edge where a = 2.0 m is the nominal minor radius of ITER. The front-end quasi-optics will be installed in an equatorial port plug (EPP#12). A particular challenge will be to pass the probing beam through the fundamental electron cyclotron resonance, which is located in the port plug (R=10.3 m) for the nominal magnetic field B_t = 5.3 T. Hence, particular mitigation actions against arcing have to be applied. The status of the design and specific challenges will be discussed.