Progress in ITER ECE diagnostic design and integration

Abstract

The ITER electron cyclotron emission (ECE) diagnostic system has primary roles in providing measurements of the core electron temperature profile and the electron temperature fluctuation associated with the neoclassical tearing modes. The ITER ECE system includes a radial and oblique line-of-sight. Four 43-meter long low-loss transmission lines (TLs) are designed to transmit millimeter wave power in the frequency range of 70–1000 GHz in both X- and O-mode polarization from the port plug to the ECE instrumentation room in the diagnostic building. The measurement instrumentation includes two Fourier transform spectrometer (FTS) systems and two radiometer systems. The Indian Domestic Agency (IN-DA) and United States Domestic Agency share the responsibility. The IN-DA scope excluding instrumentation and control has passed its preliminary design review and is progressing towards the final design review (FDR). In parallel, the diagnostic integration in different areas is ongoing. Several captive components for the TLs have passed FDR and will be manufactured for installation in the tokamak building soon. A peer review meeting has been held on the prototype hot calibration source, and its integration and new thermal analysis in the diagnostic shield module are continuing. A prototype TL is being tested. A prototype polarizing Martin-Puplett type FTS, operating in the frequency range 70–1000 GHz, features an in-vacuo fast scanning mechanism and a cryo-cooled dual-channel THz detector system. Its performance has been assessed in detail against ITER requirements.

Parametric Decay Instabilities during Electron Cyclotron Resonance Heating of Fusion Plasmas, Problems and Possibilities

“…Trapped UH wave PDIs in the ITER full-field scenarios may create strong microwave signals with frequency shifts ∼ 10 GHz from f 0 = 170 GHz [1]. This makes them a potential risk to the ITER electron cyclotron emission (ECE) and low-field side reflectometer systems, operating in the frequency ranges 70−1000 GHz [67,68] and 30−165 GHz [69], respectively. PDIs involving a significant amount of X-mode ECRH power reflected from the high-field side wall reaching the UHR are unlikely to occur in the fullfield ITER scenario, as the fundamental ECR is located close to the plasma center and therefore expected to be optically thick for the O-mode ECRH waves [61].…”

“…This means that 110 GHz and 104 GHz ECRH waves are also likely to drive PDIs involving decay of the O-mode ECRH waves into trapped UH waves and low-frequency lower hybrid waves in regions allowing UH wave trapping on the highfield side in ITER half-field scenarios. Such trapped UH wave PDIs would again pose a risk to the ECE [67,68] and low-field side reflectometer [69] systems at ITER. Operation with pellet fueling above n G e would allow the trapped UH wave PDIs to occur near the plasma center and on the low-field side in addition to the high-field side; once again, the requirement of n e < n G e at the plasma edge means that there will always be some point with R < R 0 + a at which f 0 = f UH in stable plasmas.…”

Design of a Fourier-transform spectrometer for detector characterization on CMB polarization telescope

“…Nowadays, MPI has become a conventional system for nearly all major magnetically confined devices (Alcator C [4], Alcator C-Mod [5], DIII-D [6], EAST [7], JET [8], LHD [9], JT-60 [10], JT-60U [11], TFTR [12], W7-X [13], etc.) and even for the future burning plasmas such as ITER [14].…”