Physics Conference Call, 1 April, 1996

Paritcipants: Bathke, Ehst, Jardin, Kessel, Mau, Petrie, Wong

T. Petrie summarized his work related to the design parameter space for divertors for the strawman RS power plant. His proposal is to radiate 75% of the core heating power with a radiating mantle which has roughly a thickness of 0.1-0.2a, with Argon or Krypton as the impurity. A flatter density profile creates a density pedestal near the separatrix and a temperature of less than or equal to 1 keV within the mantle is required. A higher Zeff and a higher density pedestal will help reduce the thickness of the mantle. The design does not entail the plasma to be detached from the divertor plates because experimental data in double-null configurations suggest that high confinement regimes may not be accessible. It was suggested by Ehst that vanadium be considered as the main radiating impurity since it exists naturally in the plasma with a vanadium structure surrounding the plasma. It was agreed to look into that possibility.

It was noted that a recent paper appeared in Phys Plasmas, March 1996, p1012, by W.Stacey titled "Radial thermal stability of the radiative mantle". We should make sure our radiating mantle satisfies the stability criteria in this paper.

It was offered by S.Jardin that the Physics group take over the job of finding profiles and impurity concentrations that radiate up to 75% of the power inside the separatrix. This will be done by adding coronal equilibrium radiation physics to the JSOLVER equilibrium code. This should allow us to calculate a single equilibrium, and evaluate it for stability, bootstrap current, current drive and radiation. This should be complete within the next two months, allowing complete physics consistency among the various issues.

D. Ehst described what he will present at the upcoming project meeting, including CD results, rotation data, fueling, and effects of grassy ELMs on edge density profiles. He will present gamma_B as a function of for the latest RS equilibrium with stabilizing wall located at 0.1a beyond the outboard first wall, using LFFW and HFFW. Based on calculations in which the edge density is varied, he concludes that the effect on bootstrap fraction is minimal. He also calculates the gamma_B value as a function of the current profile mismatch, and concludes that the CD power increases as the mismatch comes down. He suggests that a CD system other than HFFW should be considered for driving currents inside or near the q_min location.

T.K. Mau described plans for his presentation in the meeting. He'll present a gamma_B scaling with for the latest RS equilibrium (using LFFW, HFFW, and LHW), and a gamma_B scaling with Zeff > 1.7 for the purpose of reducing the mantle thickness. He'll present data for plasma rotation in ICRF heated discharges in TFTR, and also some theoretical analysis based on GA's work. And he'll comment on the CD and heating power requirements on startup and their compatibility to steady-state requirements.

Kessel and Jardin are to give T.K. a workplan for the PPPL MHD group for the coming two months to present at the meeting.