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ARIES-RS to ARIES-AT. C. Kessel, PPPL ARIES Project Meeting, Sept. 18, 2000. ARIES-AT Equilibrium. ARIES-AT Free-Boundary Plasma. ARIES-RS to ARIES-AT. Use of 99% free-boundary flux surface leads to more consistent calculations and higher b from stronger shape parameters
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ARIES-RS to ARIES-AT C. Kessel, PPPL ARIES Project Meeting, Sept. 18, 2000
ARIES-RS to ARIES-AT • Use of 99% free-boundary flux surface leads to more consistent calculations and higher b from stronger shape parameters • More flexible pressure profile allows simultaneous b and bootstrap alignment optimization • Increased triangularity increases bNand Ip • Increased elongation increases bN and Ip • Elimination of HFFW reduces CD power
Pressure Profile Optimization to Maximize b and Bootstrap Alignment ARIES-RS ARIES-AT
Old fixed boundary plasma is determined by k=kx-0.2, d=dx-0.2 Plasma current determined by qedge about 3.2-3.5 Full R and a used, plasma volume not consistent with free-boundary plasma New fixed boundary plasma is 99% flux surface from free-boundary equilibrium Plasma current determined by q95 =3 from free-boundary Plasma volume fully consistent with free-boundary Plasma Boundary Specification
Plasma Boundary Specification Old New
Increased Triangularity • Previously our triangularity was limited by neutron heating of inboard SC TF magnet due to slot to obtain radiating divertor • Experiments and simulations show that no slot is required to obtain detachment on inboard side (radiating divertor) • This allows increased triangularity • A short slot may still be desirable to distribute radiated heat flux
Increased Elongation • Previously our elongation was limited by the tungsten stabilizer being located between the blanket and shield • Blanket optimization has allowed the stabilizer to move into the blanket and closer to the plasma • This allows increased elongation • However, the stabilizer must operate at high temperature, and the poloidal extent and thickness is limited by TBR
Reduction in External Current Drive • Previously the off-axis current drive consisted of HFFW (48 MW) and LHCD (35 MW) • HFFW was used to drive current deeper in the plasma • Bootstrap alignment improvements from the extended pressure profile description have eliminated the need for HFFW
Lessons Learned - ARIES-AT • Accurate bootstrap current models are necessary to determine MHD stability and CD requirements • The highest b is not associated with lowest CD power, a minimum exists in PCD vs b • Use of free-boundary equilibria for fixed boundary analysis is the correct approach for configuration design