Design challenges and analysis of the ITER core LIDAR Thomson scattering system

Abstract

Articles you may be interested inData processing and analysis of the imaging Thomson scattering diagnostic system on HT-7 tokamak Rev. Sci. Instrum. 84, 053502 (2013); 10.1063/1.4804161 High-resolution Thomson scattering system on the COMPASS tokamak: Evaluation of plasma parameters and error analysisa) Rev. Sci. Instrum. 83, 10E350 (2012); 10.1063/1.4743956 Conceptual design of new polychromator on Thomson scattering system to measure Zeff a) Rev. Sci. Instrum. 83, 10E334 (2012); 10.1063/1.4733737Design and implementation of a full profile sub-cm ruby laser based Thomson scattering system for MAST Rev.The maximum temperature expected in ITER is in the region of 40 keV and the minimum average density of approximately 3 ϫ 10 19 m −3 is also expected. The proven capability, convenience, and port occupancy of the LIDAR Thomson scattering approach, demonstrated on JET, makes it an excellent candidate for ITER. Nonetheless, there are formidable design challenges in realizing such a diagnostic system. The expected high temperature presents its own problem of a very large relativistic blueshift of the scattered spectrum ͑e.g., / 0 ϳ 0.35 for T e = 40 keV͒, impacting on the laser choice and spectrometer/detector system. The combination of coupling high power lasers to the plasma and broadband wavelength detection has been examined in terms of minimizing the operational risk to the overall system, while optimizing the diagnostic performance. Part of the exercise has also included identifying the present critical components, and reducing their impact, e.g., on diagnostic reliability and performance, and attempt to make the design compatible with possible long term developments and operational requirement. Issues such as redundancy of key operational components, e.g., lasers are explored.

Rhodium coated mirrors deposited by magnetron sputtering for fusion applications

“…[1][2][3] Due to its high reflectivity in the visible wavelength range ͑Ͼ70% -80% ͒ and its low sputtering yield, rhodium may be a good candidate for first mirrors in ITER and is proposed as an option in the present design of ITER diagnostic systems such as LIDAR. 4 However, there is a lack of experiments with mirrors made from this material. Single crystal molybdenum is currently the main candidate 5 for first mirror material owing to its low sputtering yield and acceptable reflectivity.…”

Synergistic effects of hydrogen plasma exposure, pulsed laser heating and temperature on rhodium surfaces

“…This has the key advantage of separating the requirements for high power handling of the laser mirror from wide spectral bandwidth for the collection mirror [26][27][28]. This also avoids the synergistic effect presented in this paper.…”

Reactivity of rhodium during co-deposition of rhodium and carbon

“…Rhodium is considered to be one of the most promising materials for the first mirrors [1][2][3] of the diagnostic systems of the International Thermonuclear Experimental Reactor, due to its high reflectivity in the visible range and its low sputtering yield. It is thus envisaged to use rhodium coatings on polished metallic substrates.…”