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The Longitudinal Polarimeter at HERA

The Longitudinal Polarimeter at HERA. W. Lorenzon (Michigan) Precision Electron Polarimetry at Jlab (10 June 2003). Electron Polarization at HERA Laser System & Calorimeter Statistical and Systematic Precision Laser Cavity Project Summary and Outlook.

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The Longitudinal Polarimeter at HERA

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  1. The Longitudinal Polarimeter at HERA W. Lorenzon (Michigan) Precision Electron Polarimetry at Jlab (10 June 2003) • Electron Polarization at HERA • Laser System & Calorimeter • Statistical and Systematic Precision • Laser Cavity Project • Summary and Outlook

  2. Electron Polarization at HERA

  3. Sokolov Ternov Effect

  4. HERMES Spin Rotators

  5. Principle of the Pe Measurement with the Longitudinal Polarimeter Eg l (2.33 eV) e (27.5 GeV) a back scattered Compton photon Calorimeter Compton Scattering: e+lg e’+ Cross Section: ds/dEg=ds0/dEg[1+PePlAz(Eg)] ds0, Az: known (QED) Pe:longitudinal polarization ofe beam Pl: circular polarization (1) of laser beam

  6. Compton Polarimetry at HERA

  7. Experimental Setup - Overview

  8. Experimental Setup - Calorimeter

  9. Experimental Setup – Laser System

  10. Experimental Setup - Details

  11. Laser Control - COP

  12. Polarimeter Operation I

  13. Polarimeter Operation II

  14. Polarization Determination

  15. Polarization Performance

  16. “Non-Invasive” Method

  17. A large Systematic Effect - Solved

  18. Systematic Uncertainties

  19. New Sampling Calorimeter

  20. New Sampling Calorimeter - Details

  21. Systematic Uncertainties

  22. Systematic Uncertainties - II

  23. Polarization-2000 beam intensity after cavity Intensity x Final Cavity y Mount for travel

  24. A Comparison of Different Polarimeters PLe-g rateg rate(ng)(dPe)stat (dPe)syst LPOL: 33MW 0.1kHz1000 g/pulse1%/min~2% pulse lasermulti-g mode(all bunches) i.e. 0.01 g/bc1%/(>30min) (bc=bunch crossing)(single bunch) TPOL: 10W 10MHz0.01 g/bc1-2%/min~4% g cw lasersingle-g mode(all bunches)<2% (cw=continuous wave)(upgrade) New LPOL: 5kW 10MHz1 g/bc0.1%/6sper mill cw laserfew-g mode(all bunches) 1%/min (single bunch) Fabry-Perot Cavity Expected precision 0.7W

  25. Photon Detection and Systematic Uncertainty of Pe New LPOL (few-photon mode):Existing LPOL (multi-photon mode): Compton and Bremsstrahlung edges Up to 1000 g produced per pulse clearly visibleSignal/background ratio improved Background determination and > 5TeV measured in the detector! Calibration easy Calibration difficult (dPe)syst: per mill level expectedNon-linearity g main syst. error Sg=-1 Sg=+1 Sg=+1 Sg=-1

  26. Polarization after Lumi Upgrade

  27. TPOL/LPOL Ratio

  28. Conclusions

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