1. Tagging spectrometer and photon beamline Review January 23-24, 2006 1 Response to Questions Bremsstrahlung Tagging Spectrometer and Photon Beam Review Richard Jones, Jim Kellie, Dan Sober and Elton Smith

2. Tagging spectrometer and photon beamline review Jan 23-24, 2006 2 Response to questions  Describe the procedure for assembly and alignment of magnets, vacuum chamber and hodoscope, including mounting for the first time and also after a disassembly. ─ See presentation by Jim Kellie  What is the requirement for the vacuum in the tagging system? ─ Require that the radiation due to air < 10 -3 radiation from radiator → vacuum < 10 -3 torr.  What is required for the magnetic properties of the steel? ─ Define the chemistry of the steel (e.g. low carbon) ─ Request samples of steel and measure B-H curves for the samples ─ Accept final steel with same chemistry of samples ─ Note: We are not very sensitive to the quality of the steel at 1.5 T.

3. Tagging spectrometer and photon beamline review Jan 23-24, 2006 3 Response to questions  What plans do we have to determine the absolute photon energy? ─ For initial running, calculation of the photon energy based on measured (calculated?) field maps of the magnets should be sufficient. ─ Calibration of the absolute energy scale to 10 -3 can be achieved using a magnetic pair spectrometer. This procedure has recently been completed for the Hall B tagger (see CLAS-NOTE 2005-012). This would require instrumenting the pair spectrometer with additional microstrip detectors.  To what precision does the experiment need to know the polarization? ─ Richard will write a response to this