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

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 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



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