NCSX Memorandum

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

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

From: W. Reiersen

Date: 12/19/2000

Re: Minutes of 12/13 Engineering telecon

An engineering telecon was held on 12/13. Nelson provided an excellent review of the scope of work and technical requirements in each of the WBS elements within WBS 1.

PFCs

PFC requirements were somewhat nebulous. It was not clear where the fast ions were being ejected. (Mioduszewski to report at next week’s project meeting.) Requirements for a divertor were also unclear. Nelson discussed two options for configuring the plasma facing components: a discrete tile approach and a large panel approach. The large panels appeared more attractive provided they were not prohibitively expensive and could be readily fabricated. In the large panel approach, basically a surface conformal to the plasma would be completely covered with a carbon wall made out of large, formed carbon panels. Holes would be cut in the panels as required for access. Diagnostic sensors would be mounted to the vacuum vessel behind the panels. The panels would provide continuous coverage for known requirements (NB armor, fast ion loss [ripple] armor, and thermal diffusion heat loads) and would be a robust solution in the face of an abundance of uncertainties, especially in regard to flexibility. Initially, the panels could be thin with modest thermal conductivity. When we went to higher power (12MW v. 6MW) and longer pulse lengths (1.7s v. 0.3MW heating pulses), we could replace the panels in the high heat flux areas (once we knew where they were) with thicker panels with improved thermal conductivity. Cooldown was raised as an issue. Goranson should calculate whether radiation cooling of the panels to a room temperature vacuum vessel would be adequate. ORNL should proceed to develop the configuration of the plasma facing components based on the large panel approach. One of the key configuration issues is whether the panels is mounted on the vacuum vessel or is self-supporting (like the internal liner investigated for an early in-PBX option). Another key configuration issue is whether the panel assembly is radiatively cooled to the vacuum vessel, conduction cooled to the vacuum vessel, or actively cooled. (I think I listed these options in order of decreasing attractiveness.) Nelson thought that by the first part of January, we would have a feel as to the cost and fabricability of the large panel approach. We should expedite the steps required to get to that point.

Vacuum Vessel

Nelson then moved on to discuss the vacuum vessel. Zarnstorff asked about the cost of the 350C bakeout requirement. Nelson should provide a ROM cost estimate for the 350C bakeout to see if this is worth putting on our list of things to pursue in the post-PVR timeframe as a possible avenue for cost reduction. The basic shell has changed from what it looked like for the saddle option. Nelson pointed out that the kinks at the top and bottom near the NB port should be blended out. It was also apparent that there are large flat regions in this area. A quick analysis should be done to determine if the vessel is capable of handling a 1-atmosphere differential pressure load in these regions (if the large flat areas remain after blending).

Nelson reviewed the fabrication of the vacuum vessel. It appears that it will be necessary to form the vacuum vessel in four pieces rather than three pieces. This revised geometry might affect the work the Ukrainians are being asked to do about investigating different forming options. We should make sure they are considering a relevant geometry.

Vacuum vessel supports are not yet shown and need to be addressed. The question arose whether we had to provide active control of the plasma vertical position. Zarnstorff indicated that this was not necessary, at least not in the scope of the TPC.

The vacuum vessel (and PFCs, if necessary) will be heated and cooled by helium gas. Interface requirements for the helium gas system need to be generated in order for the system to be conceptualized and costed.

Coils

The discussion then moved on to coils. The reference design has been modified to reflect 5-coil PF system. Zarnstorff expressed concern as to whether or not the PF system could provide enough volt-seconds to meet flexibility requirements. Reiersen agreed to provide an assessment of the volt-second capabilities of the PF system and the requirements for the 2T reference scenario.

A while back, the question was raised as to whether we could use the surplus TFTR coils. At the time, there were some promising options. We agreed to tell the folks doing TFTR D&D in December 2000 whether we could use the TFTR PF coils on NCSX. Williamson agreed to overlay the TFTR PF coils on the current 5-coil PF set and determine which coils might be interesting. Zarnstorff reminded us that the surplus PBX and LANL coils are also available.

Tom Brown has been reviewing the configuration model and expressed concerns about possible interferences. The most critical of these might be in the region where the neutral beams pass through the modular coils. Nelson should review the port configurations and ensure that potential interferences are resolved.

Dave Williamson has been supporting Dennis Strickler in reviewing some of the more recent modular coil designs. He recently took a look at one featuring 18 modular coils (instead of 21 coils) with 4 different coil types. In this design, both symmetry planes had coils on them. Neutral beam access looked promising.

Due to the Project meeting on December 19-20, the next engineering telecon will be held on 1/5/01. Best wishes for happy holidays and a blessed New Year!

Wayne