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

2 Outline Data selection  dependence at constant B t The influence of plasma current profile on  The ‘pivot’ phenomenon in  profile The influence of lithium on energy transport Conclusion

3 Data selection 2008 Data: 04/ /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 –With-lithium: e.g –No-lithium: e.g 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 and cm -3

4  dependence on B p (or q) Parameters: I p (900kA), B t (0.48T), P heat (5.6MW), and (4.6~5.6  cm -3 ), (490~608eV) A significant influence of ngTx in the relation between  s and B p (or q) –ngTx: the abbreviation of ‘local - n e *  T i/e ’ value –units: B p in T, n e in cm -3, T i/e in eV, r is normalized magnetic surface The proportional relation between  and B p (or the inversely proportional relation between  and q )

5 The dependence of local heating on P heat Parameters: I p (900kA), B t (0.48T) P b i/e x, P heat i/e x, P cond i/e x Q ie x

6 Relation between ngTx and current profile Equilibrium – I px : the area integral of j  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 

7  dependence on plasma current P cond vs ngTx and q at constant B t and different I p –No obvious dependence on I p –Plasma current profile Constant ngTx – Constant q Peaky and flat (hollow) profile

8 Multiple Linear Regression Analysis (1) The fit using j  B p instead of ngTx

9 Multiple Linear Regression Analysis (2) The result without using local P heat, -  T as independent variables –The dependence on Bp is inconsistent with data observed –Low R 2

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 |  '|~|  p| reduce the drive of the  B and curvature drifts responsible for the interchange instability. The  -stabilization while using ballooning formulism –The stabilizing effect of high |  '| can induce enhanced temperature and density peaking leading to even higher values of |  '|, i.e. a positive feedback loop with respect to turbulence suppression and enhanced confinement. It can be responsible for part of the ITB sustainment.

11 The ‘pivot’ phenomenon in  e  profile Governed by local current density (or current profile) –Data at constant B t (2008) –Data at different B t (2006) Ip=900kAIp=1100kA Data at different B t (2006 )

12 The influence of lithium on energy transport Energy confinement time –Parameters: I p (kA): 800, 900 B t (T): 0.54(max), 0.51(avg), 0.48(min) P heat (MW): 4.3(max), 3.7(avg), 3.2(min) –  E increases –0mg: without-lithium data Radiated power –Local  e decreases –Large percentage of radiated power –No obvious improvement on  i

13 The influence of lithium on energy transport

14 The influence of lithium on energy transport  e (direct comparison) –More than 50% reduction  i (indirect comparison) –Effective The third lithium state I p : 900kA B t : 0.47T P heat : 5MW I p : 900kA B t : 0.49T P heat : 3.6MW

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

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.

17 Thank you for your attention !