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.