1. Recent Experiments on the STOR-M Tokamak
Chijin Xiao （肖持进）
Plasma Laboratory
University of Saskatchewan
ASIPP, May 26, 2011
number slides

2. Outline STOR-M tokamak program
Retarding Field Energy Analyzer for Ion Temperature Measurements
Helical Field Coils for MHD suppression
SXR measurements for determination of MHD locations

3. STOR-M Tokamak R = 46 cm, a (limiter) = 13 cm, Bt ~ 1 T, Ip ~ 50 kA
ne ~ (1-3)x1013/cm3, Te = 200 eV
PPL, Univ. of Sask.

5. STOR-M Programs Turbulent heating, heat pulse
Compact Torus (CT) injection
fuelling, pressure profile (bootstrap current) control in burning plasmas
Turbulent heating, heat pulse
AC operation
quasi steady state tokamak operation
most efficient ohmic heating method
Diagnostics development
Plasma flow velocity measurements
Ion temperature measurement (one of the today’s topics)
PPL, Univ. of Sask.

6. STOR-M Programs (cont.)
Ohmic H-modes
CT injection, plasma biasing, edge heating
MHD studies
Helical field coils  suppression of m=2 mode (one of the today’s topics)
Magnetic island structures (one of the today’s topics)
PPL, Univ. of Sask.

7. Ti Measure Motivation for Ti measurements RFA principles Simulation
Model
Results
Probe design
Experimental Results

8. Motivation for Ti Measurements
Electron temperature measurements in SOL and edge region are routinely carried out using conventional electric probes
Ion temperature measurements are scarecy and not easy
Retarding Field Analyzers (RFA) have been used in large (JET, Tore Supra) and small (ISTTOK, STOR-M) tokamaks
Precise interpretation of the data still depends on models
Technical development is still needed
Importance of global or core temperature. Some values. Some measuring techniques.

9. Importance of Ti Measurements in the Edge Region and SOL
H-mode (ETB)
Radial force balance equation
Poloidal velocity shear calculation needs ion temperature and the parallel flow velocity
Importance of Edge region measurements. Some measuring techniques. Sentence describing main point.

10. Importance of Ti Measurements in the Edge Region and SOL
Flow measurements
Geodesic Acoustic Mode (GAM) frequency
Needs ion temperature
Importance of Edge region measurements. Some measuring techniques. Sentence describing main point.

11. What Can RFA Measure? Measures ion temperature
Measures parallel flow Mach number
and velocity
It is relatively simple and cost effective
Importance of Edge region measurements. Some measuring techniques. Sentence describing main point.

12. Principle of the RFA
Pitts R.A. et al 2003 Rev. Sci. Instrum

13. I-V curve for the RFA eVshift (>0)=min. ion kinetic energy
Pitts R A et al 2003 Rev. Sci. Instrum

14. Example I-V curve from JET
Different characteristic curve
different ion temperature
Why?
What is the true temperature?
Ion side probe
Electron side probe
Pitts R A et al 2003 Rev. Sci. Instrum

15. Geometry Vװ ES G1 C Bt Vװ
Give more description of the function for flux. Derivation for Gamma?

16. Simulation – Derivation
Condition 2b:
Condition 3:
Fix bound in Gamma2 to g(v)

17. Simulation – With Plasma Flow
Probe 1 - upstream
Probe 2 - downstream
measured

18. As RFA currently being used on STOR-M
a = 1.30mm
l1 = 6.94mm
l2 = 4.40mm
Plot of measured temperature vs actual temperature with Mach number of 0.4

19. T_i routinely measured higher than T_e
T_i routinely measured higher than T_e. No complete explanation is available for this.
Plot of measured temperature vs actual temperature for several probe dimensions

20. Veco Grids Nickel base 283 micron by 283 micron openings
50 micron wide bars
About 30 micron thick
- these don’t cover plate thickness
3 basic designs outlined in report
Thickness introduces a opacity. Transmission is not 100%. Calculate same conditions as in model to determine if these need to be taken into account during the design.

21. Probe design - these don’t cover plate thickness
3 basic designs outlined in report
Thickness introduces a opacity. Transmission is not 100%. Calculate same conditions as in model to determine if these need to be taken into account during the design.

22. Probe design
- these don’t cover plate thickness
3 basic designs outlined in report
Thickness introduces a opacity. Transmission is not 100%. Calculate same conditions as in model to determine if these need to be taken into account during the design.
Dreval M., Rohraff D., Xiao C., Hirose A., 2009 Rev. Sci. Instrum

35. Resonance helical coil experiments
Identifications of MHD modes
m/n=2/1 helical coils to supress the dominant mode
Simple model to identify required RHC current.
Experimental results

36. SVD for mode analysis 12 poloidally distributed coils (up to m=6 mode)
4 toroidally distributed coils (up to n=2 mode)
Singular value decomposition spatial structure and temporal frequency of the dominant mode

37. Resonant Helical Coils

38. Mirnov coils

39. SXR arrays

40. Simple Simulations

41. Results

42. Expanded traces

43. Mirnov and SXR signal amplitudes and their wavelet spectra

44. Spatial structure of modes

45. Spatitial Fourier analysis and the rms amplitudes of m=1 to m=4

46. Relative mode amplitudes
Before Suppression
During suppression
After suppression

47. Determination of radial location of the m=2 mode
New SXR analysis techniques based on difference signals
Effectively rejects common mode noises
Reliable method for dominant single mode
May be used for mode coupling cases

48. Active MHD activities with dominant m=2 mode

49. SXR chords and assumed magnetic islands

50. Assumed emissivity profile
Along vertical axis

51. Ideal integrated signal without noises
Clear phase reversal, not much difference in amplitude

52. Actual measured SXR signal with noises or other small modes

53. Calculated difference signals
Clear phase reversal, and also change significantly in amplitude

54. Difference signal shows on the right
More clear sinusoidal oscillations with clear phase reversal
At I4 and I10 channels

55. Another shot with lower discharge current
phase reversal at I3 and I9 channels, m=2 island moved inwards
Explanations:
Ip decreases  q(a) increases
 q=2 resonance surface moves inward
M. Dreval, C. Xiao, et al, RSI (to be published)

56. Acknowledgements Drs. A. Hirose, M. Dreval (SXR)
Mr. Sayf Elgriw (MHD), Mr. Kurt Kreuger (RFA)
NSERC Canada
科学院和科技部磁约束聚变国际合作创新团队 (ASIPP)

57. Thank You!

58. Where is Univ. of Saskatchewan ?
C. Xiao, Institute of Physics, Beijing, June 25, 2001
Where is Univ. of Saskatchewan ?
Saskatoon •
SWIP, Chengdu
2017年4月22日4时4分

59. Research in Plasma Physics Laboratory
Fusion plasma theory (A. Hirose, A. Smolyakov)
Partially ionized plasma theory (A. Smolyakov)
Tokamak experiments (A. Hirose, C. Xiao)
CT injection (C. Xiao, A. Hirose)
Plasma Processing (A. Hirose, Q.Q. Yang, C. Xiao)
Ion implantation, photonics (M. Bradley)
SWIP, Chengdu
2017年4月22日4时4分