1. 1 C. E. Bush (ORNL), B. C. Stratton, S. von Goeler, J. Robinson, L. E. Zakharov, E. Fredrickson (PPPL) D. Stutman and K. Tritz (JHU) and the NSTX Team 17th Topical Meeting on the Technology of Fusion Energy November 12-16, 2006 Albuquerque, New Mexico Investigation of MHD Phenomena in NSTX Using a Fast Soft X-ray Imaging Camera ORNL PPPL

2. C. Bush, ANS-TOFE 17-2006 2 Goal, Motivation and Outline Goal: MHD physics studies on NSTX using fast soft x-ray camera imaging. Knowledge of fast particle behavior important in NSTX and ITER SXR camera obtains a snapshot of mode and structure of MHD Rich variety of MHD observed on NSTX: EPMs, NTMs and ELMs. — Important to ITER and future STs Tools are available for effective data analysis and physics modeling.

3. ORNL PPPL C. Bush, ANS-TOFE 17-2006 3 The Camera System is Optimized for Time and Spatially Resolved Observation of MHD State of the Art PSI5 CCD Camera. — 300 frames of 64x64 pixel at up to 500 kHz — Image allows fast ID of mode and structure Important for NSTX, future STs and ITER. Fast conversion of 1-5 keV soft X-ray to visible light — Uses P47 phosphor (plus signal gain) Electrostatic image intensifier and lenses — demagnify image by 6:1; couples light to CCD Pinhole camera for wide-angle tangential view — Remotely selectable pinholes: 1-5 mm dia Remotely selectable beryllium foils.

4. ORNL PPPL C. Bush, ANS-TOFE 17-2006 4 The Horizontal Field-of-View of the Camera Includes Nearly the Full Minor Cross-Section of Plasma Optical axis inclined at 9º downward angle with respect to midplane Full spatial structure of MHD Mode captured in each frame. Remotely Selectable Size: 1-5 mm

5. ORNL PPPL C. Bush, ANS-TOFE 17-2006 5 System Installed on NSTX CCD camera Image intensifier inside magnetic shield Pinholes and Be foils NSTX bay K port

6. ORNL PPPL C. Bush, ANS-TOFE 17-2006 6 Example of SXR Images of m/n=1/1 Mode t 0 =175.060 ms t 0 +90  s Camera frame rate= 100 kHz Mode frequency: ~2.5 kHz Images show 4 times during one mode period m/n=1/1 mode character clearly seen Shot #113778 t 0 +180  st 0 +270  s

7. ORNL PPPL C. Bush, ANS-TOFE 17-2006 7 SXR Diode Traces for a m/n = 1/1 mode Shot 113778 Time (s) Shot 113778 I p (kA) W tot (kJ) I SXR- center (arb) I SXR-above-mid (arb) 00.10.20.30.4 0 200 0 1000 0 0 10 20 400 600

8. ORNL PPPL C. Bush, ANS-TOFE 17-2006 8 SXR Diode Traces for a Tearing Mode I p (kA) I SXR-center (arb) I SXR-below-mid (arb) I SXR-above-mid (arb) 0 400 600 800 1200 Time (s) 400 200 800 1200 400 800 400 0.1770.1730.1750.179 3 ms Time of FSXIC Camera

9. ORNL PPPL C. Bush, ANS-TOFE 17-2006 9 Camera Images Clearly Show m/n = 1/1 Mode for Shot 113778 Camera frame rate: 100 kHz (for 3 ms)

10. ORNL PPPL C. Bush, ANS-TOFE 17-2006 10 Singular Value Decomposition (SVD) of the Camera Data Separates Coherent Fluctuations in Space and Time from Background Noise SVD identifies major components 300 frames are recorded per shot, N = 300 Matrix A(MxN) of N time series of M frames is decomposed into 3 matrices — A(MxN) = UWV T Where: — U(MxN) - columns are spatial vectors (topos) — V(NxN) - columns are temporal vectors (chronos) — W(NxN)- a diagonal matrix (of weights)

11. ORNL PPPL C. Bush, ANS-TOFE 17-2006 11 SVD for a m/n = 1/1 mode 0.175 0.176 0.177 0.178 10 3 10 5 10 7 113778 Time (s) U1 U0 U2 U3 U4 V0 V1 V3 V4 V2 The Singular Value Decomposition (SVD) yields the coherent fluctuaions in space “topos” U0-U4 and time “chronos” V0-V4 within a background of noise. U0, V0 => global time evolution of the Plasma Ref. S. Ohdachi et al. Rev. Sci. Instrum., 74 2136 (2003)

12. ORNL PPPL C. Bush, ANS-TOFE 17-2006 12 Time Evolution of m/n=1/1 Mode from Soft X-ray Diode Shows Mode Slowing Down Signal from conventional soft x-ray diode with radial midplane view shows time evolution of m/n=1/1 mode (Shot 113355). Later, will show of reconstruction of a camera image late in the evolution of the mode (247.0 ms). Time (s) SXR Signal

13. ORNL PPPL C. Bush, ANS-TOFE 17-2006 13 Shot 113355: Tearing Mode Camera frame rate: 10 kHz

14. ORNL PPPL C. Bush, ANS-TOFE 17-2006 14 SVD Shows the m/n = 1/1 mode 0.22 0.23 0.24 0.26 10 3 10 5 10 7 113355 Time (s) U1 U0 U2 U3 U4 V0 V1 V3 V4 V2 The Singular Value Decomposition (SVD) yields the coherent fluctuaions in space “topos” U0-U4 and time “chronos” V0-V4 within a background of noise. U0, V0 => global time evolution of the Plasma Ref. S. Ohdachi et al. Rev. Sci. Instrum., 74 2136 (2003)

15. ORNL PPPL C. Bush, ANS-TOFE 17-2006 15 SXR Camera Image and Reconstruction at t=247.0 ms (shot=113355) using Cbbst Code Camera Image Reconstruction

16. ORNL PPPL C. Bush, ANS-TOFE 17-2006 16 Example: Multi-Mode (shot 113384) 072 122 139 227 232244

17. ORNL PPPL C. Bush, ANS-TOFE 17-2006 17 Summary A state of the art fast soft X-ray imaging camera has been successfully used for MHD physics on NSTX — 300 frames at up to 500 kHz — Full cross sectional structure with excellent time resolution — Several MHD phenomena have been observed and studied — tearing mode, fishbones, sawteeth — m/n = 1:1 and higher observed Tools for analysis and physics modeling are providing consistent results Plan to use thicker foils for hotter NSTX Plasmas Plan to study more complex MHD phenomena This work was supported by the US DOE, Contract No. DE-AC02-76-CHO-3073.

18. 18 EXTRAS