Summary of BPM/quad offset measurements at 18E
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2 March 2024
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Tune change X: +-4 kHz Y: +-0.4 kHz
X offset: N=10 avg = -0.200 +- 0.007  rms = 0.023 +- 0.007 mm 
Y offset: N=10 avg =  0.231 +- 0.007  rms = 0.046 +- 0.014 mm 

Tune change X: +-8 kHz Y: +-0.8 kHz
X offset: N=10 avg = -0.212 +- 0.004  rms = 0.011 +- 0.004 mm 
Y offset: N=10 avg =  0.307 +- 0.014  rms = 0.043 +- 0.014 mm 


19 March 2024
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Tune change X: +-4 kHz Y: 0.4 kHz
X offset: N=53 avg = -0.167 +- 0.002  rms = 0.017 +- 0.002 mm 
Y offset: N=53 avg =  0.308 +- 0.007  rms = 0.060 +- 0.007 mm 

Tune change X: +-6 kHz Y: +-0.6 kHz
X offset: N=9 avg = -0.15 +- 0.01  rms = 0.023 +- 0.01 mm 
Y offset: N=9 avg =  0.34 +- 0.01  rms = 0.029 +- 0.01 mm 

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The X and Y offsets for the default tune range are 
now known to a statistical accuracy of about 2%.
The RMS widths are smaller for larger beta (larger tune change).

Need more data to check

1) if the measurement of the average offset depends on the tune range
2) if the rms decreases with increased tune range
3) how the repeat-ability depends on the centered orbit criterion
4) how the repeat-ability depends one the phase measurement repeat-ability alone
 
Also in the queue: repeat-ability of re-calibrations of all entries in offset.bpm.
May be able to address Suntao's concerns about SA B&C BPMs.