AIP Digital Archive
Electrical Engineering, Measurement and Control Technology
The full package of magnetics diagnostics for Alcator C-Mod is now installed inside the vacuum vessel. This consists of four poloidal arrays of pickup coils for measuring Bp, three Rogowski coils, a set of full flux loops, two diamagnetic loops with compensation coils, a small 2-D array of Mirnov coils to measure edge fluctuations, and some partial flux loops for detecting locked modes. All the coils have been absolutely calibrated to ±0.5% before installation, and an in situ calibration of this system will also be carried out. Internal mounting enables fast response despite the shielding effects of skin currents in the thick vessel wall. However, this complicates the design considerably due to constraints on physical size, vacuum compatibility, temperature extremes, protection from plasma damage, etc.
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