2003 MSE Calibration: Preliminary Analysis

1. 2003 MSE Calibration: Preliminary Analysis H. Yuh, S. D. Scott, R. Grantez 27 May 2003 File: 27may2003 MSE calibration.ppt Note: This presentation is best viewed with PowerPoint 2002 or later

2. Shot Summary 21-May-2003: A Good Day • 35 shots total • 3 - Lost due to DNB gate-valve permissive (90 minutes) • 1 - No-power test • 1 - No-field fault • 2 - Short DNB, too short to use • 28 usable MSE shots • 3 shots with about 25 ms DNB duration – usable • 5 shots with ~5 ms faults (45 ms good DNB) – good • 20 shots with full-length, 50-ms DNB

3. Calibration Data Obtained • EF3 and EF4 scan at both TF=2.7 and TF=5.4 • One shot at TF = 4.5 Tesla • One shot each with EF1 and EF2 • Several shots at same conditions to determine shot-to-shot reproducibility.

4. Two Analysis Methods Agree Well Channels 0-8: Average Difference = -0.003 degrees Scatter = 0.05 degrees Channel 9 (innermost): Average Difference = 0.06 degrees Scatter = 0.14 degrees

5. Statistical Uncertainty is ~0.06 Degrees • Inferred from standard deviation in mean angle (10 x 5-ms intervals) • Scatter is larger for innermost channel • In frame of polarimeter. • Shot-shot scatter is somewhat larger – being investigated.

6. MSE Measured Angles at BT=5.4 Tesla

7. MSE Measured Angles at BT=5.4 Tesla

8. Overall Trends Look Very Consistent – No Special Behavior at EF=0

9. Shots with Matched Ratio of TF/EF

10. Calibration Against Expected Angles • Compute field-line pitch-angle with mflux for all shots. • Data looks quite good – consitent trends -- except for outer three channels with EF3=EF4=0. • Faraday rotation effect appears to be small. • Analysis in progress.

11. MSE Measured Angles at BT=2.7 Tesla

12. We expect small variation in measured angles at the outer channels due to viewing geometry Mse measured angle (degrees) Actual field-line angle (degrees)

13. The expected nonlinearity is small

14. A Puzzle: Profiles of Measured Angles for EF=0 ‘Uptick’ at edge not understood Rmajor (cm)

15. Angle in Edge Channels Edge channel Measured Angle in Other Channels Core channels Measured Angle in Channel 4

16. Shot-Shot Scatter Sometimes Consistent with Measured Variation within a Single Shot

17. Shot-Shot Scatter Sometimes Consistent with Measured Variation within a Single Shot

18. Shot-Shot Scatter Sometimes Not Consistent with Measured Variation within a Single Shot Note: these shots have TF = 5.4 Tesla and EF3 = EF4 = 0, which seem to be problematic in other ways.

19. MFLUX Pitch-Angles during EF scan at 5.4 Tesla

20. MFLUX Mapped Pitch-Angles during EF scan at 5.4 Tesla

21. Measured MSE Angles during EF scan at 5.4 Tesla Strong rise in measured angle at outer edge Strong rise in measured angle at innermost point.

22. MFLUX Pitch-Angles during EF scans at 2.7 Tesla

23. MFLUX Mapped Pitch-Angles during EF scan at 2.7 Tesla

24. Measured MSE Angles during EF scans at 2.7 Tesla Behavior at edge similar to that at 5.4 Tesla Reasonably well-behaved on innermost points.

25. Measured MSE Polarization Fraction F Typical range of measured angles Imax - Imin Polarization fraction = F (Imax + Imin)

26. +/- 0.05 Polarization Fraction during 5.4 Tesla EF Scan • Systematic +/- 0.05 shot-to-shot variation. • Polarization fraction is much smaller on innermost channel.

27. Polarization Fraction during 2.7 Tesla EF Scan +/- 0.05 • Values at outer edge reduced from (0.6-0.7) in 5.4 Tesla scan • to (0.5-0.6) in 2.7 Tesla scan. • Innermost channel not different from others.

28. Polarization During EF4 Scan at 5.4 Tesla • Polarization fraction generally increases with increasing EF4. • Suggests possible tuning problems but effect on measured • angle should (??) be small.

29. Polarization During EF3 Scan at 5.4 Tesla Some trend toward increasing polarization fraction with increasing EF4

30. Polarization During EF3+4 Scan at 5.4 Tesla Scaling with EF is not so clear in this dataset.

31. Polarization During EF4 Scan at 2.7 Tesla Scaling with EF is not so clear in this dataset.

32. Polarization During EF3 Scan at 2.7 Tesla No clear scaling with EF in this dataset.

33. Phase Offset between 40 kHz PEM drive and Signal Offset between PEM drive and MSE Signal (radians) • Varies about mean value by +/- 0.05 radians. • No apparent trend with EF or TF

34. Phase Offset between 44 kHz PEM drive and Signal Offset between PEM drive and MSE Signal (radians) • Varies about mean value by +/- 0.10 radians. • No apparent trend with EF or TF

35. Effect of Phase Shift on Measured MSE Angle Phase Offset Amplitude Ratio D Angle (radians) (degrees) - 0.125 0.9919 0.120 - 0.100 0.9948 0.075 - 0.075 0.9970 0.043 - 0.050 0.9986 0.020 - 0.025 0.9996 0.006 0.000 1.0000 0.000 0.025 0.9997 0.004 0.050 0.9989 0.016 0.075 0.9974 0.037 0.100 0.9952 0.069 0.125 0.9925 0.108 Angle = 0.5 * atan(Amplitude Ratio) Conclusion: the observed variability in phase shift might account for 0.02 – 0.08 degrees shot-to-shot variability.

36. Conclusions • Tuning is definitely off for innermost channel at 5.4 Tesla. • Polarization fraction measurements might suggest tuning problems generally, but hard to see how this could appreciably affect our measurements. • Variability in phase shift between PEM and MSE signals is reasonably small … not enough to account for unusual behavior of edge channels during calibration.