Polarimeter 11 01 2010

Preliminary evaluation of the options for polarimetry with nuclear pair production

References

• A photon beam polarimeter based on nuclear e⁺e^- pair production in an amorphous target
• Experimental study of photon beam polarimeter based on nuclear e⁺e^- pair production in an amorphous target

Considered Options

1. Put a an e⁺e^- detector in the beamline before the PS magnet allowing for ~2.5 m lever arm.

Pros

• No magnetic field distortions.

Cons

• Short lever arm.
• Detector is exposed to the photon beam.

1. Put a an e⁺e^- detector in the beamline after the PS magnet allowing for ~4.5 m lever arm, no B-field.

Pros

• Relatively longer lever arm.

Cons

• Detector is exposed to the photon beam.
• Small distortion effects due to incomplete degaussing of the PS magnet.

1. Put separate e⁺ and e^- detectors off the beamline after the PS magnet allowing for ~4.5 m lever arm, small $\int Bdl\sim 0.12$ T m.

Pros

• Relatively longer lever arm.
• Detector not exposed to the beam

Cons

• Magnetic field mixes different momenta and angles at the same position of the detector.
• Distortion due to the fringe fields.