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Feature of Energy Transport in NSTX plasma

Feature of Energy Transport in NSTX plasma. Siye Ding under instruction of Stanley Kaye 05/04/09. Outline. Data selection c dependence at constant B t The influence of plasma current profile on c The ‘pivot’ phenomenon in c profile The influence of lithium on energy transport

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Feature of Energy Transport in NSTX plasma

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  1. Feature of Energy Transport in NSTX plasma Siye Ding under instruction of Stanley Kaye 05/04/09 1

  2. Outline • Data selection • c dependence at constant Bt • The influence of plasma current profile on c • The ‘pivot’ phenomenon in c profile • The influence of lithium on energy transport • Conclusion 2

  3. Data selection • 2008 Data: 04/21---07/14 • Quasi-steady plasma state • A least discharge length of 500ms • Flat top of at least 80ms in total stored energy during the flat top of plasma current • No transients in the loop voltage • Quiet MHD activities • There lithium states • Pre-lithium: e.g. 128584 • With-lithium: e.g. 129021 • No-lithium: e.g. 130187 • TRANSP analysis • Data used: equilibrium data, temperature and density profile, visible bremsstrahlung radiation, beam power, etc. • Match neutron emission rate by adjusting the neutral density boundary condition to values between 1010 and 1013 cm-3 3

  4. c dependence on Bp (or q) • Parameters: Ip(900kA), Bt (0.48T), Pheat(5.6MW), and <ne>(4.6~5.61013cm-3), <Te> (490~608eV) • A significant influence of ngTx in the relation between cs and Bp (or q) • ngTx: the abbreviation of ‘local -ne*Ti/e’ value • units: Bp in T, ne in 1013cm-3, Ti/e in eV, r is normalized magnetic surface • The proportional relation between c and Bp (or the inversely proportional relation between c and q) 4

  5. The dependence of local heating on Pheat • Parameters: Ip(900kA), Bt (0.48T) • Pb i/e x, Pheat i/e x, Pcondi/e x • Qie x 5

  6. Relation between ngTx and current profile • Equilibrium • Ipx: the area integral of jf from zero to the local position, i.e. the plasma current generated from core to the local position • Validity • Equilibrium • could not be met. The other terms in the motion equation? • Tn • The relation fails if two plasma states have too different Tn (the discreteness becomes too large) • Current profile has an important impact on c 6

  7. c dependence on plasma current • Pcond vs ngTx and q at constant Bt and different Ip • No obvious dependence on Ip • Plasma current profile • Constant ngTx • Constant q • Peaky and flat (hollow) profile 7

  8. Multiple Linear Regression Analysis (1) The fit using jfBp instead of ngTx 8

  9. Multiple Linear Regression Analysis (2) • The result without using local Pheat, -T as independent variables • The dependence on Bp is inconsistent with data observed • Low R2 9

  10. Support from recent theoretical work • Reference • Phys. Plasmas 10(2003)2881 C. Bourdelle et al. • Nucl. Fusion 45(2005)110 C. Bourdelle et al. • Conclusion of their theory and simulation work • High |b'|~|p| reduce the drive of the B and curvature drifts responsible for the interchange instability. • The a-stabilization while using ballooning formulism • The stabilizing effect of high |b'| can induce enhanced temperature and density peaking leading to even higher values of |b'|, i.e. a positive feedback loop with respect to turbulence suppression and enhanced confinement. • It can be responsible for part of the ITB sustainment. 10

  11. The ‘pivot’ phenomenon in ceprofile • Governed by local current density (or current profile) • Data at constant Bt (2008) • Data at different Bt (2006) Ip=900kA Ip=1100kA Data at different Bt (2006 ) 11

  12. The influence of lithium on energy transport • Energy confinement time • Parameters: • Ip (kA): 800, 900 • Bt (T): 0.54(max), 0.51(avg), 0.48(min) • Pheat (MW): 4.3(max), 3.7(avg), 3.2(min) • tE increases • 0mg: without-lithium data • Radiated power • Local ce decreases • Large percentage of radiated power • No obvious improvement on ci 12

  13. The influence of lithium on energy transport 13

  14. The influence of lithium on energy transport • ce (direct comparison) • More than 50% reduction • ci (indirect comparison) • Effective • The third lithium state Ip: 900kA Bt: 0.47T Pheat: 5MW Ip: 900kA Bt: 0.49T Pheat: 3.6MW 14

  15. Conclusion • The local energy transport properties of the NSTX plasmas both with and without lithium were investigated. • The significant influence of ‘local -ne*Ti/e’ (ngTx) value was discovered, as well as a proportional relation between c and Bp. • Plasma current profile affects c values via ngTx. • The ‘pivot’ phenomenon w/o Bt varying is the consequence of different current profile. • Lithium can improve energy confinement time and enhance radiation. • Lithium can reduce ce more than 50% when large quantities are injected. For ci, it is effective, but not quantitative investigated. 15

  16. Work plan for the extended month • The purpose of my visit • Analysis: TRANSP • Prediction: pTRANSP • The key issue: learn the technique of doing pTRANSP predictive run • Learn the skill of using the some auxiliary heating packages for pTRANSP and build EAST launcher model. 16

  17. Thank you for your attention ! 17

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