ITER-India Diagnostics

The ITER ECE diagnostic system provides electron temperature profiles of the plasma. It comprises front-end optics with an in-situ 1000 oK hot calibration source, a polarization splitter unit for selecting O-mode and X-mode emissions, and four transmission lines that deliver the radiation to radiometers and Fourier Transform Spectrometers (FTSs) located in the ITER Diagnostics Hall. The system includes an in-lab calibration source, two broadband FTS units (70–1000 GHz), an  low frequency radiometer (122–230 GHz), and an high frequency  radiometer (230–344 GHz). The front-end optics, including the hot source and the high frequency  radiometer, are under the US-DA scope, while the remaining components are under the IN-DA scope. A prototype system developed by IN-DA includes an 8 m transmission line (72 mm diameter), a hot calibration source operable up to 650 °C, and an FTS covering 70–1000 GHz with 10 GHz spectral resolution.

A broadband X-ray spectrometer (1-22 Å/ 0.5 keV-12 keV) which measures X-ray radiation from various intrinsic impurities such as W, Fe, Cu and externally injected impurities such as Ar, Ne and Xe for impurity detection and machine protection. The spectrometer is comprising of nine novel cubic shaped X-ray crystals along with four X-ray detectors (one hybrid photon counting detector and three CCDs to cover the entire energy range). The spectrometer is designed in such a way that it captures emissions from all these impurity lines radiations, simultaneously. The X-ray emissions from the ITER plasma are transported via 12-meter vacuum extension connected to the closure flange at the Equatorial port 11. The wavelength and intensity calibrations will be performed using X-ray sources of different targets. 

A high-resolution imaging type of X-ray spectrometer for measurement of edge ion temperature. The spectrometer will probe the edge plasma impurity emissions of Argon species in the wavelength region of ~ 4 Å. The spectrometer is situated in upper port -09, consists of a double‑reflection optics with toroidal graphite and spherical quartz crystals placed in Rowland mount configuration. The emission spectra are recorded with a large area hybrid photon counting detector. The X-ray emissions are coupled to the spectrometer using a ~3m vacuum extension tube from closure flange of upper port 9. 

This diagnostic provides ion temperature and plasma rotation at the pedestal region (ρ > 0.85). This diagnostic view the pedestal region of the diagnostics neutral beam (DNB) plasma interaction zone and collects the charge exchange emissions of He, Ar and Ne and beam emissions from hydrogen DNB. The emissions are collected via optical labyrinth situated inside Equatorial port -3 and transported to the visible spectrometers using radiation resistant fiber optic bundles. The CXRS spectrometers are one of its kind having a customized design to measure three wavelengths, simultaneously. Developments include high-transmission radiation hard fiber bundles (> 82 %), a magnetic resilient and radiation resistant Misalignment Compensator (MAC) and High Etendue Visible Spectrometer are under progress. 

The upper port -09 hosts two tenant diagnostics: XRCS-Edge spectrometer and High Field side Reflectometer (HFSR)waveguides. The port plug design caters to the need of providing line of sight for the X-ray spectrometer and also HFSR. The neutron shielding blocks used in port plug are made up of B₄C blocks. As a protype activities these B4C blocks are developed along with Indian industry: M/s Bhukanvala, Gujarat.