1. Measurement of Gas Bremsstrahlung at the Pohang Light Source Hyosang Lee Seoul National University, Q2C Pusan National University, HANUL HNP2011

2. Contents Measurement of gas bremsstrahlung Measurement of hadron photoproduction

3. Motivation Pohang Light Source (PLS) 3rd generation synchrotron facility with a beam emittance of 18.9nm ⋅ rad 2.5GeV electron linear accelerator : full energy injector for the storage ring 2.5GeV Electron Storage Ring : 12-period Triple Bend Achromat lattice 180mA at 2.5GeV Design to provide synchrotron radiation with continuous wavelengths down to 1Å LINAC Storage Ring

4. Motivation Bremsstrahlung produced through electromagnetic interactions of circulating electrons with storage ring components with residual gas in vacuum carrying polarization information of the electrons circulating time evolution of the electron polarization (due to spin-flip synchrotron radiation) -> electron energy measurement of gas bremsstrahlung = measurement of electron energy Eγ = 0 ∼ E max,e- First gas bremsstrahlung measurement at PLS

5. Experimental method 3 data taking run : 2007, 2009, 2010 Detector : scintillation crystal [CeF 3, PbWO 4, CsI] 1C1 beam line straight section with 5.3 m vacuum : 0.5nTorr photon transport : 6.3 ϕ, 13.6m soft-X ray shielding : 2mm Pb slabscomponent Mole fraction(%) Weight fraction(%) H2H2 9041.86 N 2 /CO532.55 CH 4 311.16 CO 2 110.23 H2OH2O14.18

6. Experimental method CeF3 PbWO4 CsI Detector : CeF3, PbWO4, CsI Tungsten collimator : ϕ 3, 7mm veto by plastic scinti. to reject e+e-

7. Beam profile - 2007 data tungsten wire + 1x1mm2 scinti. CeF3 x-axis : 10mm y-axis : 4mm

8. Raw data & Energy Calibration center CeF3 : ~78% (MC 77.6%) 1/Eγ distribution Geant4 simulation center - 77.6% surrounding - 19.4% leakage - 3% Energy calibration

9. Result - 2007 data photon flux - 10/s @ >400MeV with 180mA - 39/s @ 180mA Energy resolution -

10. Experimental setup - 2009 Detector PbWO4 : 1.9cm x 1.9cm x 20cm CsI : 7cm x 7cm x 30cm 5B1 beam line with 5.3 m straight line PWO center PWO sum Total sum CeF3 sum

11. Result - 2009

12. Need energy calibration with fixed energy beam CsI energy PWO energy Energy sum ? ?

13. Hadron photoproduction - motivation Hadron photoproduction : 0.23 Hz By using gas bremsstrahlung γp -> π0p π p

14. Hadron photoproduction - Experiment 3x3 PWO 5x5 CsI Target & Start Count to measure bremsstrahlung to measure π 0 ->γγ Measurement of bremsstrahlung Measurement of hadron photoproduction with γp->π0p Experimental setup start time ToF to measure p Beam γp -> π0p

15. Hadron photoproduction - Signal UpvetoStart Counter Multiplicity in ToFToF

16. Hadron photoproduction - ToF Calibration t0 calibration time correction position calculation

17. Hadron photoproduction - CsI Calibration CsI calibration with cosmic-ray muon

18. Hadron photoproduction - γ clustering Geant4 simulationreal data clustering method

19. No π0 events ? Next to do : - γ hit position - energy leakage - energy calibration No π0 events ? Next to do : - γ hit position - energy leakage - energy calibration Hadron photoproduction - π0 mass real data Geant4 simulation CeF3 Energy

20. Hadron photoproduction - Dipole Magnet

22. Summary Measurement of Gas Bremsstrahlung First measurement 3 data run Detector : CeF3, PbWO4, CsI photon flux - 10/s @ >400MeV with 180mA - 39/s @ 180mA Need to energy calibration with fixed energy beam Measurement of Hadron Hadron photoproduction : 0.23 Hz By using gas bremsstrahlung γp -> π0p