The ITER core imaging x-ray spectrometer

Abstract

The core imaging x-ray spectrometer (CIXS) is one of several ITER diagnostic systems planned for measurements of the central ion and electron temperature profiles and of the toroidal and poloidal rotation velocity profiles, Ti, Te, vϕ, and vθ respectively. The diagnostic is based on precision determinations of the Doppler broadening and centroid shift of the lines of highly ionized heavy impurities using a curved Bragg crystal spectral disperser and imager. In a departure from earlier designs, the CIXS employs a novel imaging geometry utilizing spherically bent crystals operating at a Bragg angle near 45°, which spatially and spectrally resolves the x-ray emission from the plasma. In addition, the working radiation will be the L-shell emission of highly charged tungsten ions. Particular emphasis is placed on the strong 3d5/2 → 2p3/2 electric dipole transition in neon-like tungsten W64 +. Here we present the conceptual design of the instrument, which may include an x-ray calorimeter, and discuss the spectral features used in future measurements.