BCM calibration (d2n)
Contents
Strategy
- Use special run to calibrate OL02 cavity against Faraday cup
- Calibrate EPICS bcm variable by calibrating BCMs against OL02
- Calibrate BB/LHRS scalers against OL02
Key for BcmLog files
Column headings for BCM log file (from Vince via Kalyan):
- Entry #
- BCM 1 voltage (upstream BCM)
- BCM 2 voltage (downstream BCM)
- Unser (not used)
- Faraday Cup (if extracted = 0)
- 0L02 (injector reading)
- 0R07 (not used)
Results for BCM calibration
Final results relating scaler rates (e.g. u1r) in Hz to Beam Current in uA:
| Scaler | Slope (Hz/uA) | Offset (Hz) |
|---|---|---|
| u1 | 2102.26 | 395.8 |
| u3 | 6480.30 | 453.393 |
| u10 | 19731.3 | 770.66 |
| d1 | 2152.44 | 154.58 |
| d3 | 6658.34 | 133.27 |
| d10 | 21007.6 | 293.48 |
The equations follow the form u1r = Slope*(Beam Current in uA) + Offset
Using scripts in Diana's ifarm account, /u/home/dseymour/d2n_analysis/bcm_calibration
From MakeBCMPlotHists, calibrating BCM1 & 2 to OLO2 for each current set point:
BCM1 = 0.020673 * OLO2 - 0.001692
- <math>\sigma_m = 0.000035</math>
- <math>\sigma_b = 0.000243</math>
BCM2 = 0.020990 * OLO2 - 0.001710
- <math>\sigma_m = 0.000037</math>
- <math>\sigma_b = 0.000276</math>
From MakeBCMPlotError, calibrating OLO2 to Faraday cup from linear fit to entire run (minus 12 outlier points). Data points given arbitrary error bars of 0.1 in x and y.
FARA = 0.9971 * OLO2 + 0.0171
- <math>\sigma_m = 0.0003</math>
- <math>\sigma_b = 0.0104</math>
Combining these equations gives the overall real current (in <math>\mu</math>A) from the BCM readings:
<math>\mu</math> = 48.24 * BCM1 + 0.0987
- <math>\sigma_m = 0.0829</math>
- <math>\sigma_b = 0.0157</math>
<math>\mu</math> = 47.51 * BCM2 + 0.0983
- <math>\sigma_m = 0.0849</math>
- <math>\sigma_b = 0.0167</math>
Results for Beam Charge calibration
yet to be done
Relevant HALOG entries
- Feb 17 BCM cal data:
Useful Documents
- Explanatory page from PVDIS experiment
- Vince Sulkosky's tech note
- Mark Jones's tech note: Media:Jones_bcm.pdf
