Photon Beam Design Requirements

Global Specifications for the Hall D Photon Beam

1. choice of photon energy in the range 8 - 12 GeV [1]
2. orientable diamond crystal bremsstrahlung radiator [2]
3. peak linear polarization of 40% at 9 GeV with collimation [2,3]
4. average polarization 36% in coherent peak 8.4 - 9.0 GeV [2,3]
5. bremsstrahlung collimator with active stabilization [3]
6. photons tagged in coherent peak with energy resolution better than 60 MeV (0.5%) [1,4,5]
7. beam tagged at 1% resolution over extended range 3 - 11.4 GeV [4,6]
8. absolute photon energy calibration better than ± 30 MeV
9. nominal operation at 10 MHz tagged photons in coherent peak after collimator [1,3]
10. tagging rate 25 MHz within coherent peak at nominal intensity [5]
11. tagging possible up to 100 MHz tagged photons on target in coherent peak [1,3,5]
12. 500 MHz beam pulse repetition rate [1,5,6]