1. 1 Report on analysis of PoGO Beam Test at Spring-8 Tsunefumi Mizuno mizuno@SLAC.Stanford.EDU July 15, 2003

2. 2 Detector/Beam configuration (1) Beam goes from +x to –x Polarization vector of incident beam: along x-axis Beam size: a circle of 2.68cm diameter Expected beam energy:83.6 keV (incident beam of 100keV is scattered at 90 degree; this direction picks up the minor component of incident beam whose polarization vector is along z-axis) Expected polarization vector: along z- axis Beam(100keV) polarization vector Collimator (smaller hole) Collimator (bigger hole) x y

3. 3 Detector/Beam configuration (2) y z Id:1 2 34 5 67 Expected polarization vector 26.8mm 49mm hexagonal scintillators 20cm long Beam direction Beam goes from +x to –x Beam size: a circle of 2.68cm diameter Expected polarization vector: along z-axis Expected beam energy:83.6 keV (incident beam of 100keV is scattered at 90 degree) Right figure corresponds to the rotation angle of 0 degree. We rotated the detector. rotation angle

4. 4 Run summary Data are stored in http://www.slac.stanford.edu/~mizuno/PoGO/Spring8http://www.slac.stanford.edu/~mizuno/PoGO/Spring8 calibration with 241Am for PMT1 (before beam test): run16_p.txt 0 degree run/bg: run17_p.txt and run18_p.txt 30 degree run/bg: run19_p.txt and run20_p.txt 15 degree run/bg: run21_p.txt and run22_p.txt 180 degree run/bg: run23_p.txt and run24_p.txt bg without beam: run25_p.txt calibration with 241Am (after beam test): run26_p.txt Data files with _p are peak data and without are waveform data (binary).

5. 5 Calibration run (1) PMT/scint 1 PMT/scint 2 PMT/scint 3 PMT/scint 4

6. 6 Calibration run (2) PMT/scint 5 PMT/scint 6 PMT/scint 7 PMT/scint 4 PMT/scintillator of #4 is taken by ch4(upper card) and ch8(lower card) and gives consistent spectra -> DAQ itself works well. (real time monitor might not)

7. 7 Energy spectrum of each scint. 0 degree 180 degree 2 scintillators are with hit (detection threshold is assumed to be 3keV) Total deposit energy above 45 keV is selected. Energy scale of ch1 might be incorrect (see page 5). For other PMT/scintillators, no significant difference (modulation) is observed.

8. 8 Total energy deposition 2 scintillators are with hit (detection threshold is assumed to be 3keV) Total deposit energy above 45 keV is selected. Beam energy was expected to be 83.6 keV (100keV is scattered at 90 degree), but is ~70 keV. -> main component is double scattered photons? might be unpolarized? run17: 0 degreerun23: 180 degree