Manufacturing of a prototype for the first diagnostic component to be supplied by F4E to ITER, the Continuous External Rogowski (CER) coils, was completed in December 2010.
These coils are to be located outside the vacuum vessel, within the cases of three Toroidal Field (TF) coils. Their purpose is to measure the toroidal current flowing within the contour of the TF coils, which approximates to the plasma current under steady conditions, a key measurement with relevance for safety and plasma control.
The CER coils are formed by two layers of concentric windings (as seen below in an X-ray image of the prototype) insulated by fibreglass and enclosed in a stainless steel braided sheath. Each coil measures approximately 50 metres in length. By contrast to other common methods of measuring the plasma current, the Rogowski method provides the measurement with a single sensor, resulting in very high reliability.
The prototype was manufactured in the frame of an F4E grant awarded in the spring of 2010 to a group of EU Fusion Associations including CRPP, CEA and RFX. The next step is to subject the prototype to a series of tests in order to confirm its measurement performance and establish its compatibility with the ITER environment. The tests include characterising its behaviour at cryogenic (liquid nitrogen) temperature, in high vacuum and under mechanical stresses foreseen to occur during operation of the TF coils. The testing, which is being carried out at CRPP in Lausanne and CEA in Cadarache, is scheduled to be completed in May 2011.
If the test results are deemed satisfactory, work on finalising the detailed design of the CER coils is expected to follow under the auspices of a new F4E grant and should be completed by the spring of 2012. Thereafter, the coils will be manufactured by F4E and supplied to ITER for installation in the TF coil cases in 2013.
This x-ray image of the CER coils shows the two layers of concentric windings which are insulated by fibreglass and enclosed in a stainless steel braided sheath
The CER coil (in red) installed in a groove in the Toroidal Field coil case. Image courtesy of CEA
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