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The ITER tokamak includes 18 superconducting D-shaped toroidal field (TF) coils. Unavoidable shape deformations as well as assembly errors will lead to error fields in the final configuration, which can be modeled with the knowledge of the current center line (CCL). We are building a room temperature magnetic measurement system using low-frequency ac excitation current through the TF coil and arrays of pickup coils, fabricated with printed circuit board technology. Deviations from the expected shape of the CCL will be obtained by comparing the amplitude of magnetic flux measured at several locations around the perimeter of the TF coil, with values computed assuming the nominal current distribution. We present experimental results obtained with a cable placed in one-turn groove of a full scale radial plate. [ABSTRACT FROM PUBLISHER]

The ITER tokamak includes 18 superconducting D-shaped toroidal field (TF) coils. Unavoidable shape deformations as well as assembly errors will lead to field errors, which can be modeled with the knowledge of the current center line (CCL). Accurate survey during the entire manufacturing and assembly process, including transfer of survey points, is complex. In order to increase the level of confidence, a room temperature magnetic measurement of the CCL on assembled and closed winding packs is foreseen, prior to insertion into their cold case. In this contribution, we discuss the principle of the CCL determination and present a low frequency ac measurement system under development at PSI, within an ITER framework contract. The largest current allowed to flow in the TF coil at room temperature and the precision requirements for the determination of the CCL loci of the coil are hard boundaries. Eddy currents in the radial plates, the winding pack enclosures, and possibly from iron in the reinforced concrete floor of the assembly hall are more subtle to bring under control quantitatively, and will limit the highest frequency that can be used to measure reliable values of the field gradients. Our objective is to measure the CCL loci by combining magnetic data obtained with printed circuit board flux coils and survey data gathered around the perimeter of the D-shaped coil. [ABSTRACT FROM PUBLISHER]

The production of more than 60% of superconducting cables for the main dipoles of the Large Hadron Collider has been completed. The results of the measurements of cable magnetization and the dependence on the manufacturers are presented. The strand magnetization produces field errors that have been measured in a large number of dipoles (approximately 100 to date) tested in cold conditions. We examine here the correlation between the available magnetic measurements and the large database of cable magnetization. The analysis is based on models documented elsewhere in the literature. Finally, a forecast of the persistent current effects to be expected in the LHC main dipoles is presented, and the more critical parameters for beam dynamics are singled out. [ABSTRACT FROM AUTHOR]