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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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