2003 MSE Calibration: Preliminary Analysis H. Yuh, S. D. Scott, R. Grantez 2 June 2003 File: 2June2003 MSE calibration.ppt Note: This presentation is best viewed with PowerPoint 2002 or later

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

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.

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

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.

MSE Measured Angles at BT=5.4 Tesla

MSE Measured Angles at BT=5.4 Tesla

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

Shots with Matched Ratio of TF/EF

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.

MSE Measured Angles at BT=2.7 Tesla

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

The expected nonlinearity is small

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

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

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

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

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.

MFLUX Pitch-Angles during EF scan at 5.4 Tesla

MFLUX Mapped Pitch-Angles during EF scan at 5.4 Tesla

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

MFLUX Pitch-Angles during EF scans at 2.7 Tesla

MFLUX Mapped Pitch-Angles during EF scan at 2.7 Tesla

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.

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

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

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.

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.

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

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

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

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

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

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

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.

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.