NCSX Memorandum

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

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

From: W. Reiersen

Date: 10/11/00

Re: Minutes of 10/11 Engineering telecon

Attachments: [1] 001011_DJS_Modular_Coil_Design.pdf [2] williamson_1011.pdf [3] 001011_MJC_Access.pdf

An engineering telecon was held on 10/11 to discuss progress on our engineering tasks. The meeting opened with Dennis Strickler providing an update on modular coil design to accommodate tangential NBI [1]. Dennis explored a six coil per period option that did not look too good – access was not good and fitting errors were up. The seven coil per period option in which the symmetry plane coil was moved inward also did not fare well – fitting errors were high. However, the seven coil per period option in which the symmetry plane coil was moved out looked good. Fitting errors were about the same as before. With a few tweaks, it appeared the NB access could be made acceptable. This was indeed great news!

David Williamson followed with a comparison of the new design with the 0907 design [2]. It was clearly shown that the symmetry plane coil moved out about 1m and the adjacent coils moved a bit outward and closer to the symmetry plane coil. One of the areas Williamson has been working is to try to improve the structural design by moving the structural shell closer to the coils, avoiding long cantilevers. Preliminary efforts have been frustrated by Pro/E’s unwillingness to cooperate in making models. Williamson is investigating a NURBS-based modeler as an alternative to Pro/E.

Mike Cole presented an assessment of NB access with this new coil design [3]. It looked very promising although the clearances are still a bit tight. The neutral beam appeared to fit very well within the plasma. Cole looked at changing the injection angle of the neutral beams very slightly – 2 degrees. This opened up the clearances significantly. The beam just started to poke out on the inboard side.

It appears we have an avenue forward for the modular coil design. Subsequent actions include:

Nelson to define envelope requirements for minimum acceptable clearances

Strickler to work with Cole to tweak modular coil design to provide optimal access

Williamson to modify TF and PF geometry to avoid interferences with modular coils

One concern with the new design is the stray field in the vicinity of the beamlines. Reiersen agreed to calculate the stray fields and compare them to allowables.

The issue of current density was discussed. The current density in the present design is uncomfortably high, as are the power requirements for modular coils. It appears unlikely that we will be able to perform the minor miracle required to solve this problem without changing the basis of the design. Two alternatives that would work (if we can do them) are winding the coil out of solid copper conductor and pre-cooling the coil to LN2 temperatures. The second option appeared to be the more palatable and will be pursued in the near term.