03 September SIT Meeting Summary

The project's technical baseline is currently the CDR design, which was based on the M45 (unhealed) coil design.

The current plan is that there will be an ECP in the Fall to update to a new baseline configuration design. The goal is to have the updated model available in time to give to the modular coil manufacturing development suppliers, ideally at the time contract negotiations start (scheduled for end of November). The updated design would include:

- Revised structure geometry and a coil design that provides increased plasma-wall standoff and healed islands.
- Improved cooling concept.
- Possibly one less PF coil pair (PF 3&4 merged)
- Possibly a revised central solenoid support concept.

What are the issues?

1. Structure time constants may be too long.
The steel modular coil supports provide a poloidally continuous conducting path. Time constant has been roughly estimated at 50ms; refined calculations are in progress (Brooks). But, 50ms is seen as problematic for plasma control, since time scales of interest (e.g., for current or beta rise) are much shorter. Will poloidal breaks be necessary to break up the eddy currents and thereby reduce the time constants? Need Art's analysis as input to finding a solution path.

2. Structure and coil geometry modifications.
Coil designs that provide the required physics and engineering properties have been generated on the new winding surfaces issued by Williamson (2, 3, and 4 cm displaced from the CDR design). Encouragingly, the coil-plasma spacing has been increased by 5 cm using the 2-cm displaced winding surface in combination with a shifted-out plasma. It probably provides adequate space for divertor needs. Issues:
- Still needs to be healed. Recent experience (i.e. with early-June designs) is that healing takes at least two months.
- After a healed design has been selected, must update the CAD model. Expected to take 2 months.
- Must confirm that the coils can be assembled over the vacuum vessel. This is said to require construction of a physical model.

So, it could be at least four months (early January) before we have an updated CAD model of a satisfactory coil design, more than a month later than desired. It will be some time later still before we can build a physical model and confirm assembly.

ACTIONS:
Can we improve the schedule by shortening the healing process (Mike)?

Can we improve the schedule by shortening the CAD model updating time (Brad)?

If we later find that there are assembly problems with the revised geometry, how will we solve it? (Brad)

3. Cooling and CS support concepts (Wayne)

We are close to finishing the evaluation of the cooling options and should be able to select one by Sept. 13. The CS support evaluations are in similarly good shape.

4. PF Coils (Wayne)

ACTION: Brad propose a geometry (coil center and cross section) for a new PF coil that merges PF 3-4.

5. Next SIT Meeting: Monday, Sept. 9, 2002, 11:00 a.m. EDT.

Please forward any questions or comments to mailto:reiersen@pppl.gov

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