Photon Polarization Analysis Bill Bugg Data selection: 1) PCALE Max cut <400

1. Photon Polarization Analysis Bill Bugg Data selection: 1) PCALE Max cut <400 2) Visual Inspection. For every cycle of every run we plot and examine a series of 72 histograms and scatter plots of signals from individual counters. PCALE,D,C,B Ag1Sic Ag2Sic Ag1 Ag2 GCAL CsI (channel 9) Toroid >50 ADC counts Possi TL,TR,BL,BR X,Y, collimator counters, etc. We look for changes in toroid current, or beam position, saturated channels, missed undulator pulses during the cycle and eliminate cycles on this basis.

2. Adjacent runs with opposite field are treated in pairs to obtain the global asymmetry. • I choose not to remove ‘flyers’(results outside 3 sigma) • unless study of data for the cycles involved identifies a problem • missed earlier. The photon results are not sensitive to this choice. • In addition to the plots for each run cycle we write out file with mean, rms and number of events passing the tests for 18 elements. These are: • Ag1SiC, Ag2SiC, Ag1, Ag2, GcaL Possi Sum(4 quadrants), Toroid, Possi old, PcalE, D, C, x(bpm 6130), y(bpm 6130), and 4 collimator counters(ColT, ColB, ColR, ColL). These are recorded both for Undulator on and off. These data are written into an Excel file for processing and study and asymmetriy results passed to PAW for final fits. • 5) Processed Excel files are available for all the September data so that anyone interested can play with the data. These files are my working files so you will find them full of a variety of plots and correlations which you can ignore if you wish.

3. ANALYSIS In routine analysis we use the means for each cycle. Background is subtracted and counter data normalized to AG1SiC signal. (Ag1 works about as well) . Normalization to toroid signal gives poorer results, Normalized signals and the difference/sum value evaluated are for each pair. For target in data we also evaluate asymmetries for CsI central channel We also look at Possisum which should show no asymmetry. The results are fit by PAW An example follows of output looked at for each cycle (same cycle I showed in Princeton. I was too lazy to make new slides)

4. Run 2542 target in Good

13. Run 2590 cycle 1 Target out (Bad)

18. Run 1571 saturation of Ag2Sic(bad)

19. Analysis has been completed for all the September data for target in and target out and Spectrometer currents 100, 120, 140, 160positrons, 160electrons, 180 normal fluid and 180 ferro fluid. There is no a priori reason to expect the photon results to depend on spectrometer current but we present them separately for comparison as some differences in errors show up. Data for Spectrometer current = 100 are shown as an example

20. Asymmetry Photon September data Spectrometer=100

21. Positron data

28. Asymmetry

29. % error

30. June data Spectrometer=140

31. Conclusions • Photon Asymmetry is well measured in all 3 counters • Best measurement with Ag2SiC, then Gcal followed by Ag2 • Measurements are consistent with having same asymmetry within errors independent of spectrometer current. • Errors in each counter increases with spectrometer current( or more probably in my opinion due to data quality deterioration as run progressed)

32. Comments • Transmission is very different from June • Positrons strike almost entirely the left hand side of exit window • Positrons (and electrons) pass primarily through the downstream half of jaw slit. • Beam is consistently steered to left of gamma collimator aperture. Steering is different for undulator on/off • Undulator steers the electron beam about 25 microns in x and y when it fires (bpm 6130)

33. Spect=100 data