1. Observations of impurity transport in NSTX Luis F. Delgado-Aparicio Princeton Plasma Physics Laboratory and the NSTX Research Team 4 th ITPA Transport & Confinement Meeting Culham, Oxford, UK, 22-25 March 2010 NSTX Supported by College W&M Colorado Sch Mines Columbia U CompX General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Washington U Wisconsin Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec

2. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 2 In collaboration with… D. Stutman, K. Tritz, M. Finkenthal and D. Kumar Plasma Spectroscopy Group (PSG) The Johns Hopkins University (JHU, USA) R. Bell, S. Kaye, W. Solomon, B. LeBlanc, J. Menard, S. Paul and C. H. Skinner Princeton Plasma Physics Laboratory (PPPL)

3. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 3 Outline 1.Motivation and main diagnostic 1.Impurity transport experiments in NSTX a)  * scan at fixed q-profile b) * scan of NBI heated H-modes c) First-cut results from momentum & particle pinch experiment 3.Toroidal rotation effects on particle diffusivity 3.Future experiments, diagnostic needs & possible “areas” of collaborations

4. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 4 Motivation Melted tungsten for the ITER-DT phase? 1.The understanding of impurity transport in magnetically confined fusion plasmas is one of the challenges facing the current fusion research. 2.Study the properties of impurity particle transport in a spherical tokakak (ST) in a variety of scenarios. 3.Important for extrapolation to the next step ST devices such as CTF and for comparison with the large aspect ratio tokamaks like ITER.

5. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 5 The main diagnostic for impurity transport used in NSTX is the tangential ME-SXR array L. Delgado-Aparicio, et al., RSI, 75, 4020, (2004). JAP, 102, 073304 (2007). PPCF, 49, 1245 (2007). NF, 49, 085028, (2009). Magnetic axis (core) NSTX top view

6. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 6 Outline 1.Motivation and main diagnostic 1.Impurity transport experiments in NSTX a)  * scan at fixed q-profile b) * scan of NBI heated H-modes c) First-cut results from momentum & particle pinch experiment 3.Toroidal rotation effects on particle diffusivity 3.Future experiments, diagnostic needs & possible “areas” of collaborations

7. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 7 Example 1:  * scan at fixed q-profile L. Delgado-Aparicio, et al., PPCF, 49, 1245 (2007). L. Delgado-Aparicio, et al., NF, 49, 085028, (2009). Ne puff

8. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Experimental and simulated SXR profiles at low vs. high field 8 L. Delgado-Aparicio, et al., Nucl. Fusion, 49, 085028, (2009).

9. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Experimental diffusivity in agreement with theoretical models 9 L. Delgado-Aparicio, et al., Nucl. Fusion, 49, 085028, (2009). Note large increase in D neo and D exp at r/a>0.8

10. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Convective velocity changes sign with B T 10 L. Delgado-Aparicio, et al., Nucl. Fusion, 49, 085028, (2009). V Z 0.5 at low-field is anomalous ⇒ instabilities?

11. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 11 Example 2: * scan of NBI heated H-modes * scan of NBI heated H-mode plasmas with n, I p and B  held constant. The high-power discharges have as much as twice the T i,e in the gradient region (r/a~0.6-0.8). * vary up to a factor of four with nearly identical density profiles. 2 MW 4 MW 6 MW

12. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Reconstructions show differences in SXR emissivities for low- & high- NBI power in the regions where * changed 12 1.The low-energy emissivities (  LE-SXR ~n Ne8+, Ne9+ ) indicate that the core emissivity decreases with NBI power while increasing at the gradient region. 2.However, the high- energy emissivity (  HE-SXR ~n Ne10+ ) indicate that both the core and gradient region emissivity increases with NBI power.

13. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Charge state distribution can explain the differences in emissivity without the need of changing the transport 13 Preliminary results from MIST simulations indicate that a factor of two increases of T e (0.6<r/a<0.8) could be solely responsible for modifying the Ne charge state distribution and thus the SXR emissivity, without the need of changing the underlying transport properties.

14. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 14 Outline 1.Motivation and main diagnostic 1.Impurity transport experiments in NSTX a)  * scan at fixed q-profile b) * scan of NBI heated H-modes c) First-cut results from momentum & particle pinch experiment 3.Toroidal rotation effects on particle diffusivity 3.Future experiments, diagnostic needs & possible “areas” of collaborations

15. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Results from the momentum and particle transport experiments are on the way (w/W. Solomon and S. Kaye) 15 The flattening effect during the n=3 braking seems to be stronger in the core than in the edge region. Get D & V from time-dependent MIST modeling. After the n=3 pulses the core impurity pile-up seem to be stronger; need to invoke inward V pinch ?

16. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 16 Outline 1.Motivation and main diagnostic 1.Impurity transport experiments in NSTX a)  * scan at fixed q-profile b) * scan of NBI heated H-modes c) First-cut results from momentum & particle pinch experiment 3.Toroidal rotation effects on particle diffusivity 3.Future experiments, diagnostic needs & possible “areas” of collaborations

17. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 17 Core impurity diffusivity can be affected by rotation in NSTX ( × 10-100 static D Neo ) C O Ar Fe Mo Ne Neon D PS (  ) Neon-like Fe D PS (  ) Wong (‘87) & Romanelli (‘98) Pfirsch-Schlüter D neon (  ) MDMD VV TiTi 1. Charge-states from heavy impurities (Z≠A/2) can have different D PS (  ). 2. D PS (  ) can be several times larger than that of the neoclassical transport for stationary plasmas. 3.This is an additional mechanism to explain enhanced core diffusivities without the need of invoking the presence of long wavelength electrostatic turbulence. D PS (  =0) a) b) c) d)

18. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Pellet injection can probe enhanced core impurity transport 18 n C ( × 10 12 cm -3 ) Ablation resistant, vitreous C pellets deposits impurity deep in the plasma. Evolution of  n Z much slower than that of  T e. D C around 1 m 2 /s for r/a > 0.6 (Neoclass. range). D C (r/a→core) > 1m 2 /s NCLASS range

19. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 19 Outline 1.Motivation and main diagnostic 1.Impurity transport experiments in NSTX a)  * scan at fixed q-profile b) * scan of NBI heated H-modes c) First-cut results from momentum & particle pinch experiment 3.Toroidal rotation effects on particle diffusivity 3.Future experiments, diagnostic needs & possible “areas” of collaborations

20. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 20 Density and impurity control is goal of multi-year Li program on NSTX Lithium Research (LR) Topical Science Group: XP-1002: Core impurity density and radiated power reduction using variations in LLD divertor conditions (V. Soukhanovskii, LRNL). XP-1024: Controlling Impurity Sources by Diffusive Lithium Injection (C. Skinner, PPPL). XP-1027: RMPs below the ELM triggering threshold for impurity screening (J. Canik, ORNL). XP-1056: Can Li Aerosol injection mitigate high-Z impurity accumulation during ELM-free H-modes (D. Mansfield, PPPL)? Advanced Scenario Topical Science Group: XP-1005: Modifications to the early discharge evolution to reduce late impurity content evolution (J. Menard, PPPL). XP-1006: Development of High-Elongation Beam Heated Scenarios with Reduced Impurity Content and Increased Non-Inductive Fraction (S. Gerhart, PPPL). XP-1007: Use of HHFW heating to increase the non-inductive current fraction in NBI produced H-mode plasmas with triggered ELMs to control impurity buildup (M. Bell, PPPL).

21. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 21 New ME-SXR diagnostics will enable transport experiments probing also Z-dependence Increased spatial resolution (~1 cm) probing the edge and gradient region. Five broadband energy ranges will allow estimates of C, O, Ne, Ar and Fe transport. (Courtesy of K. Tritz - JHU)

22. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 22 Possibility of joint experiments (…just some ideas for 2011) 1.Study relationship between D & V and rotation (important for NSTX, NHTX and CTF). Use NBI and/or n=3 magnetic braking. Use different impurities. Exp. tests vs. Wong/Romanelli’s model. 2.Relationship between V p and central electron heating in NSTX. Use HHFW heating →T e /T i ~1-4. Compare with NBI→T e /T i ~1 3.Z-scaling of impurity transport. C, O, Ne, Ar and metals! Reviving the pellet injector. 4.Study relationship between resonant magnetic perturbations and edge transport. 3D-non-axisymmetric perturbations. MHD events such as RWMs & ELMs. Magnetic ELM-pace experiments. i.Impurity transport. ii. “Flushing” impurities from core. 5.Measuring He transport in NSTX. Right diagnostic not working yet! Good time/spatial resolution. (5-10 ms, 1-4 cm) Diagnostic based on beam emission. i.SXR trans. grating spectro. (JHU). ii. Scanning visible spectro. (PPPL).

23. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Acknowledgements 23 The Johns Hopkins University: Gaib Morris, Scott Spangler, Steve Patterson, Russ Pelton and Joe Ondorff. Princeton Plasma Physics Laboratory: Bill Blanchard, Patti Bruno, Thomas Czeizinger, John Desandro, Russ Feder, Jerry Gething, Scott Gifford, Bob Hitchner, James Kukon, Doug Labrie, Steve Langish, Jim Taylor, Sylvester Vinson, Doug Voorhes and Joe Winston (NSTX). This work was supported by U.S. DoE Contract No. DE- AC02-09CH11466 at PPPL and DoE grant No. DE-FG02- 99ER5452 at Johns Hopkins University.

24. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 24 EXTRAS

25. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 25 Add an extrinsic impurity for transport studies

26. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 Ne gas-puff technique proven useful in MHD experiments 26 1.The earlier appearance of the NTM appear to be due to the enhanced P rad. 1.Verifying the linear-dependence of the island-width growth-rate with  ∙P rad is important, as it predicts that tokamaks can be susceptible to TM destabilization by impurity radiation. Study of radiation induced tearing modes Studying the correlations between magnetic and kinetic diagnostics for resistive wall mode identification

27. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 27 Rotation can increase the stationary D Pfirsch-Slüter K. L. Wong, et al., PRL, 59, 2643, (1987); Phys. Fluids B 1, 545, (1989). M. Romanelli, et al., Plasma Phys. Control. Fusion, 40, 1767, (1998). Although Wong and Romanelli’s results were derived using different methods, the neoclassical enhancement due to rotation is the SAME! ∴ Neoclassical diffusivity for heavy impurities can be one to two orders of magnitude higher in a rotating plasma than in a stationary one without the need of invoking the presence of long wavelength electrostatic turbulence.

28. NSTX 4 th ITPA Transport & Confinement Meeting, Culham, Oxford, UK – Delgado-Aparicio March 22-25, 2010 28 Core impurity diffusivity can be affected by rotation in NSTX ( × 10-100 static D Neo ) C O Ar Fe Mo Ne Neon D PS (  ) Neon-like Fe D PS (  ) Wong (‘87) & Romanelli (‘98) Pfirsch-Schlüter D neon (  ) MDMD VV TiTi Can be tested using: a)Pellet injection b)Laser blow-off c)Balanced NBI d)n=3 mag. braking e)Argon injection D PS (  =0) a) c) d) b)