XP532 – B T / b Scaling of Confinement

1. Office of Science Supported by XP532 – BT/b Scaling of Confinement College W&M Colorado Sch Mines Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Maryland U Rochester U Washington U Wisconsin S. M. Kaye (PPPL) Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAERI Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec

2. Objectives • Objectives • Perform dedicated Ip and BT scans at fixed density, beam power to determine parametric dependence of confinement on these parameters • Perform dimensionless scans on n*, b holding all other parameters (q, r*) From 2004 Data 2

3. Scans Wildly Successful • Able to operate with relatively fixed density and confirm BT and Ip scalings • Scaling with b is modest, although strong increase with decreasing n* • Also studying the underlying transport (TRANSP, G-K calculations,high-k scattering) 3

4. BT Scan – Performed at Ip=0.7 and 0.9 MA, Two Sources 4

5. Reduction in Electron Transport Outside r/a=0.5 Mostly Responsible for Improvement in Confinement with BT Flattening of Te inside r/a=0.5 leads to increase in ce there (non-local transport?) ETG unstable at r/a=0.5 for 0.35 T, not for higher fields (GS2, analytic theory) 5

6. 0.9 MA Scan Confirms Strong BT Scaling (but weaker than at 0.7 MA)Ip Scaling at 0.55 T Indicates Weaker Ip Scaling • Narrow range of density in each scan • Improvement in ions outside r/a=0.5 mostly responsible for improvement in confinement in Ip scan – related to neoclassical transport? 6

7. Very Modest Decrease of Confinement with Increasing Beta Observed (Source C Appears to Be “Efficient” – large increase in “heating per captured MW”) High b point provides high leverage on scaling 7

8. Collisionality Scan at Constant q, b, r*, PNBIConfinement variation Due to Both Ion and Electron Improvement (as might be expected from individual Ip, BT scans) • Variation with n* based on constant q scan; can interpret as BT1.5 or Ip1.5 8

9. Summary and Plans • The dedicated scans performed during the last run confirm the originally surprising scaling results seen in previous runs • These recent scans keep density fixed, eliminating a primary correlation in the regressor variable set • The scaling with beta is also found to be week, with high leverage from the high beta discharges • The good results allow us to examine the underlying transport properties • BT scaling controlled by electrons • IP scaling controlled by ions • The results are being analyzed in the framework of microinstability theory through linear g-k calculations and analytic theory • Global non-linear runs for some cases are presently underway (GYRO, GTC, GEM?) – results by IAEA deadline?? • Computational issues for high-k modes • Data also being examined relative to high-k fluctuation observations (D. Smith) 9