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, H. Kugel

From: W. Reiersen

Date: 10/18/00

Re: Minutes of 10/18 Engineering telecon

An engineering telecon was held on 10/18 to discuss progress on our engineering tasks. The meeting opened with Mike Cole discussing recent modifications to the modular coil design for improved NB and RF access [1]. The modular coil on the v=0 symmetry had been moved in slightly and adjacent coils had been moved out slightly to improve NB access. Cole discussed two layouts – a 3 co/1 counter layout and a 2 co/2 counter layout. Both looked promising. A 4 co layout did no appear feasible. Neilson concurred and indicated that no further effort to accommodate 4 co-beams should be made.

Cole discussed candidate locations for RF launchers for the two layouts. It appeared that if there only a single co-beam was being injected at a NB port (under the v=0 modular coil), then an RF launcher might also be positioned there. If both co-beam and counter-beams were being injected at a NB port, it appeared difficult to provide the necessary feeds and supports to the RF launcher. It also appeared possible to accommodate the RF launcher in the bays adjacent to the v=0.5 bay provided that neutral beams were not shining directly on it. The v=0.5 bays could not accommodate RF launchers because of severe height restrictions. The bays adjacent to the NB ports although large, did not appear usable because of neutral beam sightlines. The conclusion of the discussions was that there did not appear to be any showstoppers for neutral beam or RF access. However, a few caveats were made:

TF and PF coils were not in the model yet

Intercoil structure and a cryostat were not in the model yet

Gaps required for assembly and differential thermal growth have not yet been set

RF feeds and supports not yet considered

Nevertheless, excellent progress was clearly evident.

Williamson and Strickler then discussed progress in the modular coil design [2]. Williamson first discussed improvements to the modular coil twist algorithm. By adjusting the local twist angle, coil-to-coil interferences can be avoided while preserving a 12x16cm cross-section. Moving the winding surface 5cm closer to the plasma would allow a larger (12x20cm) cross-section. This might bring the chilled water option back into contention but would likely impact the plasma reconstruction.

Action: Strickler to assess the impact at the plasma of moving the winding surface as proposed by Williamson

Williamson also discussed a change by which the coil-to-coil separation was increased by 2cm. This case is referred to as 1017a1. Its reconstruction was verified after the telecon by Strickler who forwarded it to Art Brooks for posting.

Action: Williamson to provide the geometry of a supplemental TF and PF sets to complete the coil specification for analysis

The discussion then turned to future actions. Development of a structural concept, the addition of a cryostat, and establishment of an assembly scheme were identified as areas where additional work is required.

At the previous telecon, the stray fields in the vicinity of the neutral beams from the oversized modular coil were identified as an area of concern. Reiersen calculated the stray fields [3] at the ion source to be 40G and at the front of the neutralizer to be 80G. These results were subsequently discussed with Kugel. Kugel indicated that these fields should not present major problems. However, this issue should be re-visited in more detail prior to the PVR.

The next telecon will be next week at our regular time, 1:30pm Eastern time. The main topic will be to finalize plans for the PVR.