1. An Investigation of Topological Structures in Radiation Profiles and on Impurity Confinement by Laser Ablation B. Zurro, A. Baciero, K. J. McCarthy, M. A. Ochando, F. Medina, T. Estrada, A. López-Fraguas, A. López-Sánchez, J. Vega and TJ-II Team Laboratorio Nacional de Fusión, CIEMAT, Asociación EURATOM/CIEMAT, 28040 Madrid, Spain

2. Motivation The scope of our research on transport using spectroscopic techniques covers: - Impurity injection experiments to search for non-exponential decays that are characterized by stretched exponentials, A 0 exp (-(t/  )  ).  - Investigation of topological structures in radiation profiles and their correlation with confinement. - Study of non-thermal velocities via Doppler spectroscopy of heavy ions injected by laser ablation.

3. Non-Exponential Relaxation and Transport ~ 2 D t  second moment of the Gaussian [hallmark of Brownian motion,  =1] distribution that governs the probability of being at site x at time t subdiffusionsuperdiffusion (  012 normal diffusion ballistic diffusion

4. Typical Raw Data Plot of the most relevant traces for the impurity injection experiment. Temporal evolution of two Fe XVI lines as recorded by a CCD mounted on a normal incidence VUV spectrometer.

5. Effect of Strong Injection Effect of strong Fe injection in TJ-II plasma monitors (lhs). Temporal evolution of the density profile during Fe injection as observed by a reflectometer (rhs).

6. Impurity Confinement Time vs n e Plot of the decay parameter  versus line-averaged electron density for a series of TJ-II discharges having different magnetic configurations (lhs). Plot of the beta parameter versus density for 32_102_65 (rhs)

7. N e Scan at [(  bar (0) = 1.375,  bar (a) = 1.458)] Plot of  and  parameters versus n e for a single magnetic configuration (lhs). Comparison of  from relaxation in n e and rad (top right) and  (bottom right).

8. Density scan (100_44_63) Plots of  parameters versus n e from:  from radiation -avg / local- (lhs)  from central signals after tomographic reconstruction (rhs)

9. VUV / X-RAY Linear Camera Baciero, Zurro, McCarthy et al. Rev. Sci. I. 73, 287(2002)

10. Position of flattenings/humps This plot was calculated from the data from 4 discharges belonging to the same TJ-II configuration. Open red circles correspond to features from profiles at 3 different times while blue ones correspond to time t 2. Good symmetry is observed in the location of features.

11. Simulation of feature position Simulation of chord-averaged effects on the feature algorithm, including the influence of islands on local radiation profiles at positions defined by the iota profile (rhs) and with its estimated theoretical widths.

12. Comparison simulation-experiment A comparison of feature positions obtained from simulation (lhs) and experimental (rhs) profiles when using the same algorithm to recover such features (Baciero, Zurro, McCarthy et al. EPS 2002).

13. Correlation topological structures-confinement The relevance of these topological structures, as characterised by two parameters (up and sum), is plotted versus density together with the energy content of the plasmas, as quantified by the robust product n e T e. Density scan in ECRH plasmas

14. Conclusions CONFINEMENT BY IMPURITY INJECTION Impurity confinement time (  ) rises dramatically above a certain density. Non-exponential relaxation is observed in impurity injection experiments with the beta parameter of the stretched exponential ranging from ~ 0.5 to 2. Electron and ion confinement seems to exhibit some difference as a function of density (a more detailed analysis is needed). TOPOLOGICAL STRUCTURES We have shown that low level signals in radiation profiles can be associated with structures in plasmas: symmetry and coincidence with rational surfaces position. When we quantify features in profiles, we have note some relationship with plasma energy. APPARENT TEMPERATURE OF HEAVY IONS Mass dependence of the apparent impurity temperature validate the role played by non-thermal velocities (astrophysical model). Its dependence with density will allow its correlation with confinement to be studied.

15. References IMPURITY INJECTION 1 Seguin, F.H. and Petrasso R., Phys. Rev. Lett. 51, 455 (1983) 2 Fussmann G., Report IPP III/105 (1985) 3 Leung, W. K. et al., Plasma Phys. Control. Fusion 28, 1753 (1986) 4 Horton L. D. et al., Nucl. Fusion 32, 481 (1992) 5 Zurro B. et al., Proc. 1998 ICPP & 25 th CCFPP, Praha 1670-1673 (1998). 6 Zurro B.et al., Plasma Phys. Control. Fusion 30, 1767 (1988) 7 Navarro A.P., M A Ochando and Weller A.W., IEEE Transactions on Plasma Science, 19, 569 (1991) 8 Ochando M. A. et al., 12th IAEA Stellarator Workshop, Madison (1999) TOPOLOGICAL STRUCTURES 9 Baciero A., Zurro B., McCarthy K.J. et al., Rev. Sci. Instrum. 73, 283 (2002). 10 Arsenault H.H. and P. Marmet, Rev. Sci. Instrum. 48, 512 (1977) 11 Baciero A., Zurro B., McCarthy K.J. et al. Plasma Phys. Control. Fusion (2001) 12 Zurro B., McCarthy K.J. et al., Europhys. Lett. 40, 269 (1997) NON-THERMAL VELOCITIES 13 McCarthy et al. EPS (2002) 14 Zurro et al. Phys. Rev. Lett. 69, 2919 (1992)

16. TJ-II Stellarator CURRENT TJ-II PARAMETERS R = 1.5 m ≤ 0.22 m B o = 1.2 T P ecrh ≤ 2  300 kW t pulse ≤ 300 ms n e (0) ech ≤ 1.7  19 m -3 T e (0) ech ≤ 2 keV

17. Neutral Beam Injectors Ion mass Injected energy Energy mix ratio Pulse length H o 40 keV 80:10:10 ≤300 msec. INJECTION PARAMETERS

18. TJ-II Experimental Set-up

19. Non-thermal Velocities. Motivation - Doppler spectroscopy of emission lines is one of the most powerful ways to measure ion temperatures. It is assumed that ions at the same location and time have the same kinetic temperature. So by measuring it for one, the correct ion temperature is found. However superimposed micro- and macro-turbulence could affect this and result in line- widths that do not fit the general interpretation framework. - An obvious test is to measure the Doppler temperatures of several ions of different masses that are well localised in a hot plasma and that have sufficient residence time so as to be well thermalised. In this way, thermal and non-thermal contributions can be separated and the linear mass dependence claimed by the model can be checked.

20. Non-thermal velocities. Background - In astrophys., the theory of non-thermal velocities is used to account for excess broadening of spectral emission lines. The spectral line shape is taken as a convolution of a thermal Gaussian distribution and a turbulent one. -  FWHM) = 1.665( /c)(2kT i /m i + NT 2 ) 1/2 where NT 2 = 2kT(T z - T i )/m i and T z = T i + (m i / m p ) T T - NT 2 is the dispersion of the isotropic micro-turbulence velocity distribution, T i and T T are the ion temperature and the temperature associated with the micro-turbulence, m i and m p are the ion and proton mass.

21. Impurity Lines - Spectrum about 36 nm before and after iron injection (lhs). - Spectrum about 165 nm of O VII lines (rhs). - All spectral lines used are emitted by ions in plasma centre.

22. Line Profile Fitting - Fe XVI line at 33.54 nm (lhs) & O VII line at 163.8 nm (rhs). - Lines are isolated and can be well fitted by Gaussian profile. - After deconvolution of line width with instrument function excess broadening is observed.

23. Apparent Ion Temp. vs. Ion Mass -The proton temperature profile is flat, T i ~65 ± 10 eV. -The mass dependence of the apparent impurity temp. validates the role played by non-thermal velocities (astrophys. model). -Its dependence with density will allow its correlation with confinement to be studied.

24. TJ-II Experimental Set-up

25. Iron Injection

26. Oxygen VII Lines

27. Fe XVI Line Profile Fitting

28. OVII Line Profile Fitting

29. Proton Temperature Profile

30. Apparent Ion Temp. vs. Ion Mass

31. Density Scan