1. R. Arnold SLAC 24 June 2002 Real Photon Collaboration Conceptual Design Review Beam Monitoring Instruments

2. Spent Electron Detectors Dump Collimator Toroids Wire Array Cherenkov -- “thin” detector Ion chamber -- “thin detector” Secondary Emission Quantameter -- “thick” detector Electron beam instruments in BSY Photon beam instruments in ESA

3. Photon Beamline in SLAC BSY Dump magnets Sweep magnet C37 Collimator Electron dump e- and  beam from diamond  beam to ESA Beam monitors go here

4. Photon Beamline for E160 ESA BSY Q27 Q28 GoniometerDump Toroid Wire Array Sweep Ion chambers C37Collimator D3LASS Dipole Detectors Compton Polarimeter Ion Ch. Dump BendTarget SEQ

5. Spent Electron Detectors Purpose is to measure electrons that have radiated Measure energy spectrum mirror image of photons Continuously monitor flux for every beam pulse Monitor beam quality and diamond condition Parasitic to the photon beam, non interfering Detailed spectral shapes are used to compare to calculations of photon flux and polarization Design number of channels and resolution to match expected spectral shapes Goals and Requirements

6. SED Design Features Detectors are segmented ion chambers Located outside and under vac chmb in B33, B34 Cover electron energy ~1 to ~38 GeV Position vac chmb to optimize SED performance Segmentation matched to expected spectral features Radiation hard construction (metal and ceramic) Readout into CAEN ADC’s Design optimized by GEANT simulations Similar to one used in 1970’s SLAC photon beam

7. Typical Spent Electron Spectra For various energies of beam and coherent gamma peak Spent Electron Energy (GeV) 0 20 40 Beam / Gamma = 45 / 15 GeV45 / 25 GeV 48 / 35 GeV48 / 45 GeV

8. GEANT Simulation B33 x scale compressedB34 Cu bar SED Ion chamber B33 normal scale SED Ion chamber

9. Position of vac chambers is important GEANT results with chambers and Cu bars parallel to magnet axis gap spike shadow Cu bars Cu bar in gap

10. Gap in Cu bar causes problems

11. Preferred Design Cu bars parallel to each other fill the gap with short bars B33 Magnet vac chamber Small ion chamber under bellows Cu bar

12. SED Ion Chamber Construction Al plates Al channel with lid Macor (ceramic) 8 cm long segments HV and signal path Sealed Al Box with N gas flow through All radiation hard materials

13. SED installation under B33 vac chamber ion chamber

14. SED Assembly Side View B33 B34 Small ion chamber Region below 1 GeV not covered

15. Resolution Study 5 GeV10 15 20 25 30 Response to mono energetic peaksRadiative tail -- no coherent peaks z position in SED ion chamber -- 8 cm bins

16. SED Response vrs X X (cm) in Ion Chamber SED Ion chamber SED Position and X response B33 cut view

17. Input electron spectra SED response Beam / Gamma = 45 / 15 GeV 45 / 25 GeV

18. Input electron spectra SED response Beam / Gamma = 48 / 35 GeV 48 / 45 GeV

19. A line Torroid Assembly 4 inch aperture 20 kW supported in air

20. Existing dump line torroid components Ferrite to be reused Make new coils and supports for torroid in air 4.9 inch aperture

21. Dump Line Wire Array Parameters Similar to E158 Wire Array -- uses SEM from wires Measure electron beam integrated over every pulse Monitor beam spot, energy, position continuously 48 x 48 wires, 0.007 in CuBe, 0.020 in spacing Under tension to prevent sagging from expansion Radiation hard all metal and ceramic construction In separate vac tank Readout via twisted pair to CAEN ADC’s in CHA

22. Dump Line Wire Array Conceptual design

23. Typical Performance of E158 Wire Array

24. E160 End Station A Plan Start with E158 Layout D2 Collimator D3 Dipole New for E160 LASS DipoleDetectors Compton Polarimeter Ion Ch. SEQ

25. Thin/Thick detector method for diamond alignment Thin = cherenkov and ion chamber -- measures number of gammas Thick = SEQ -- measures energy of gammas Data from SLAC beam in ‘70s

26. Secondary Emission Quantameter Total Absorption shower detector Measures total energy of one beam pulse Uses secondary emission from Cu plates Non saturating (no gas) Power capacity to 10 kW Water cooled

27. SEQ Al foil + 1/2” Cu plates 0 3 6 inch High Power Total Absorption Secondary Emission Quantameter Built in ‘70’s for SLAC photon beams

32. E158 detector cart -- support stand for SEQ, Cherenkov and Ion chamber

33. Cherenkov, Ion Chamber, SEQ