Development of Faraday-cup-based Fast Ion Loss Detector in Wendelstein 7-X

摘要

Study of fast-ion losses due to magnetic field ripples and fast-ion-driven magnetohydrodynamic (MHD) modes is an important research regarding fusion-born alpha losses [1]. In order to understand fast-ion losses in Wendelstein 7-X (W7-X) plasmas, installation of fast-ion loss diagnostic is planned [2]. For the upcoming OP1.2b campaign in 2018, a prototype Faraday-cup-based fast-ion loss detector (FILD) has been designed as a joint cooperative project between National Institute for Fusion Science (NIFS) and Max Planck Institute for Plasma Physics. The Faraday-cup-based FILD, which is relatively cost-effective in construction compared with a scintillator-based FILD, has been installed to measure the fast ion loss flux in the Compact Helical System (CHS) [3, 4], the National Spherical Torus eXperiment (NSTX) [5], the Joint European Torus (JET) [6, 7], the Doublet III-D (DIII-D) [8], and the Heliotron-J [9, 10]. The FILD is capable of measuring the flux, the pitch angle (χ), and the energy (E) of escaping fast ions simultaneously, thus providing a clear understanding of fast-ion losses induced by MHD modes and non-axisymmetric magnetic field ripples. An increase of co-going fast-ion losses due to energetic particle modes (EPM) and toroidal Alfvén eigenmodes (TAE) was reported in CHS [4].