NCSX Memorandum

To:������� T. Brown, A. Brooks, H-M. Fan, B. Nelson, D. Williamson, M. Cole, P. Goranson, R. Hatcher, C. Neumeyer, L. Dudek

CC:������ J. Schmidt, H. Neilson, P. Heitzenroeder, J. Lyon, S. Hirshman, M. Zarnstorff, A. Reiman. L. Berry, D. Strickler, R. Simmons, H. Kugel

From:��� W. Reiersen

Date:���� 11/02/00

Re:������� Minutes of 11/01 Engineering telecon

An engineering telecon was held on 11/01.� Williamson presented recent progress in the design of the modular coil option [1].� The structural shell has been moved closer to the windings to provide more effective support for the coils.� The shell will be segmented in 21 segments.� Each segment will be joined on equi-spaced radial planes.� The 21 supplemental TF coils will be mounted on flat plates that are located between the segments on these radial planes.� The toroidal excursion of the modular coils extends well beyond the toroidal extent of the structural shell segments.� Features need to be added that would allow the modular coils to be attached to adjacent shell segments where the modular coils are otherwise unsupported.� Cut-outs in the shell are required for access.� These cut-outs need to avoid the 21 parting planes.

The discussion then shifted to trim coils.� Brooks has tested a concept for helical trim coils.� The concept appears to work well when the coils are located close to the plasma.� The m=5 set below did a nice job of suppressing the 3/5 island chain without exciting any other islands.� It did this with modest current requirements (<10kA) for both saddles and modulars when located on the nominal winding surface of the saddle coils.� An m=6 set for suppressing the 3/6 island chain is also shown.� We will incorporate these two helical trim coils into the saddle and modular options.� Williamson will define a winding surface for these trim coils for the modular design.� The winding surface will be inside the modular coils and outside the vacuum vessel.� The windings will be pre-fabricated on panels that are installed in 60� segments prior to installation of the vacuum vessel.� Once the winding surface is defined, Brooks will generate the optimum winding path.� Williamson will modify the winding path to accommodate access and assembly requirements.� Modifications to the winding path must preserve stellarator symmetry.� Brown will do the same for the saddle option.� Brooks will be exploring concepts other than helical windings in parallel.