Difference between revisions of "Photon Beam Design Requirements"
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# continuous real-time monitoring of post-collimator beam spectrum [8] | # continuous real-time monitoring of post-collimator beam spectrum [8] | ||
# average polarization within coherent peak determined with accuracy ±2% absolute [8] | # average polarization within coherent peak determined with accuracy ±2% absolute [8] | ||
− | # absolute photon energy calibration better than ±30 MeV [8] | + | # absolute tagged photon energy calibration better than ±30 MeV [8] |
# post-collimated beam shielding sufficient to keep detector backgrounds originating outside the experimental target below 1% of those coming from the target seen by all detectors, for each significant particle species considered separately [9] | # post-collimated beam shielding sufficient to keep detector backgrounds originating outside the experimental target below 1% of those coming from the target seen by all detectors, for each significant particle species considered separately [9] | ||
Revision as of 18:06, 29 January 2008
Global Specifications for the Hall D Photon Beam
The following top-level specifications for the Hall D photon beam are determined by the physics requirements of the GlueX experiment and the anticipated capabilities of the CEBAF accelerator at 12 GeV. The specifications for Hall D beamline components and related instrumentation are derived, in turn, from these. References added to the end of each item in the list below indicate which subsystem is affected.
- choice of photon energy in the range 8 - 12 GeV [1]
- duty factor >90% at 500 MHz beam pulse repetition rate [1]
- orientable diamond crystal bremsstrahlung radiator [2]
- peak linear polarization of 40% at 9 GeV with collimation [2,3]
- average polarization 36% in coherent peak 8.4 - 9.0 GeV [2,3]
- photon beam collimator with half-angle 22 μr [3]
- photon beam centered on collimator to within 3 μr [1,3]
- photons tagged with energy resolution better than 60 MeV (0.5%) within coherent peak [1,4,5]
- beam tagged with reduced resolution over extended range 3.0 - 11.4 GeV [4,6]
- complete tagger coverage in range 9.0 - 11.4 GeV with 1% resolution [4,6]
- nominal operation at 10 MHz tagged photons in coherent peak after collimator [1,3]
- tagging rate 25 MHz within coherent peak at nominal intensity [5]
- tagger capable of operating above nominal intensity, up to 100 MHz in coherent peak after collimator [1,3,5]
- beam adjustable down to threshold of 10-4 nominal intensity for absolute normalization measurements [1,7]
- average tagging efficiency at least 50% within coherent peak under nominal conditions, 70% for higher intensity running [1,4,5]
- continuous real-time monitoring of post-collimator beam spectrum [8]
- average polarization within coherent peak determined with accuracy ±2% absolute [8]
- absolute tagged photon energy calibration better than ±30 MeV [8]
- post-collimated beam shielding sufficient to keep detector backgrounds originating outside the experimental target below 1% of those coming from the target seen by all detectors, for each significant particle species considered separately [9]
Photon Beam Subsystems
- 12 GeV electron beam and associated instrumentation
- diamond radiator and goniometer mount
- active photon collimator system
- tagging magnetic spectrometer
- high-resolution tagging microscope
- broad-band tagging hodoscope
- total absorption counter
- pair spectrometer and hodoscopes
- collimator cave shielding