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

Slide 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

Slide 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.

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

Slide 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.

Slide 6 MSE Measured Angles at B T =5.4 Tesla

Slide 7 MSE Measured Angles at B T =5.4 Tesla

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

Slide 9 Shots with Matched Ratio of TF/EF

Slide 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.

Slide 11 MSE Measured Angles at B T =2.7 Tesla

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

Slide 13 The expected nonlinearity is small

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

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

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

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

Slide 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.

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

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

Slide 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.

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

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

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

Slide 25 Measured MSE Polarization Fraction Polarization fraction = F I max - I min F (I max + I min ) Typical range of measured angles

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

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

Slide 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.

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

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

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

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

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

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

Slide 35 Effect of Phase Shift on Measured MSE Angle Phase Offset Amplitude Ratio  Angle (radians) (degrees) 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.

Slide 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.