Feature of energy transport in nstx plasma
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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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Feature of energy transport in nstx plasma

Feature of Energy Transport in NSTX plasma

Siye Ding

under instruction of Stanley Kaye

05/04/09

1


Outline

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


Data selection

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


C dependence on b p or q

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


The dependence of local heating on p heat

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


Relation between ngtx and current profile

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


    C dependence on plasma current

    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


    Multiple linear regression analysis 1

    Multiple Linear Regression Analysis (1)

    The fit using jfBp instead of ngTx

    8


    Multiple linear regression analysis 2

    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


    Support from recent theoretical work

    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


    The pivot phenomenon in c e profile

    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


    The influence of lithium on energy transport

    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


    The influence of lithium on energy transport1

    The influence of lithium on energy transport

    13


    The influence of lithium on energy transport2

    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


    Conclusion

    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


    Work plan for the extended month

    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


    Thank you for your attention

    Thank you for your attention !

    17


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