Difference between revisions of "Photon Beam Design Requirements"
From GlueXWiki
(→Global Specifications for the Hall D Photon Beam) |
(→Global Specifications for the Hall D Photon Beam) |
||
Line 11: | Line 11: | ||
# photon beam collimator with half-angle 22 μr [4] | # photon beam collimator with half-angle 22 μr [4] | ||
# photon beam centered on collimator to within 3 μr [1,4] | # photon beam centered on collimator to within 3 μr [1,4] | ||
− | # photons tagged with energy resolution better than | + | # photons tagged with energy resolution better than 10 MeV within coherent peak [1,5,6] |
− | # beam tagged with reduced resolution over extended range 3.0 - 11. | + | # beam tagged with reduced resolution over extended range 3.0 - 11.7 GeV [5,7] |
− | # complete tagger coverage in range 9.0 - 11. | + | # complete tagger coverage in range 9.0 - 11.7 GeV with energy resolution better than 30 MeV [5,7] |
# nominal operation at 10 MHz tagged photons in coherent peak after collimator [1,6] | # nominal operation at 10 MHz tagged photons in coherent peak after collimator [1,6] | ||
# tagging rate 25 MHz within coherent peak at nominal intensity [6] | # tagging rate 25 MHz within coherent peak at nominal intensity [6] | ||
# tagger capable of operating above nominal intensity, up to 100 MHz in coherent peak after collimator [1,5,6] | # tagger capable of operating above nominal intensity, up to 100 MHz in coherent peak after collimator [1,5,6] | ||
− | # beam adjustable down to threshold of 10<sup>- | + | # beam adjustable down to threshold of 10<sup>-3</sup> nominal intensity for absolute normalization measurements [1,8] |
# average tagging efficiency at least 50% within coherent peak under nominal conditions, 70% for higher intensity running [1,5,6] | # average tagging efficiency at least 50% within coherent peak under nominal conditions, 70% for higher intensity running [1,5,6] | ||
# continuous real-time monitoring of post-collimator beam spectrum [9,10] | # continuous real-time monitoring of post-collimator beam spectrum [9,10] | ||
# average polarization within coherent peak determined with accuracy ±1% absolute [9,10] | # average polarization within coherent peak determined with accuracy ±1% absolute [9,10] | ||
− | # absolute tagged photon energy calibration better than ± | + | # absolute tagged photon energy calibration better than ±10 MeV [9,10] |
# 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 [11] | # 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 [11] | ||
Revision as of 12:52, 15 May 2008
Notice: this document is currently in draft form, and is expected to change over the coming weeks - Richard Jones, 2/7/2008
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 [2,3]
- peak linear polarization of 40% at 9 GeV with collimation [2,3,4]
- average polarization 36% in coherent peak 8.4 - 9.0 GeV [2,3,4]
- photon beam collimator with half-angle 22 μr [4]
- photon beam centered on collimator to within 3 μr [1,4]
- photons tagged with energy resolution better than 10 MeV within coherent peak [1,5,6]
- beam tagged with reduced resolution over extended range 3.0 - 11.7 GeV [5,7]
- complete tagger coverage in range 9.0 - 11.7 GeV with energy resolution better than 30 MeV [5,7]
- nominal operation at 10 MHz tagged photons in coherent peak after collimator [1,6]
- tagging rate 25 MHz within coherent peak at nominal intensity [6]
- tagger capable of operating above nominal intensity, up to 100 MHz in coherent peak after collimator [1,5,6]
- beam adjustable down to threshold of 10-3 nominal intensity for absolute normalization measurements [1,8]
- average tagging efficiency at least 50% within coherent peak under nominal conditions, 70% for higher intensity running [1,5,6]
- continuous real-time monitoring of post-collimator beam spectrum [9,10]
- average polarization within coherent peak determined with accuracy ±1% absolute [9,10]
- absolute tagged photon energy calibration better than ±10 MeV [9,10]
- 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 [11]
Photon Beam Subsystems
- 12 GeV electron beam and associated instrumentation
- diamond crystal radiator
- goniometer mount for radiators
- active photon collimator system
- tagging magnetic spectrometer
- high-resolution tagging microscope
- broad-band tagging hodoscope
- total absorption counter
- pair spectrometer and target
- pair spectrometer hodoscopes
- post-collimator beamline and shielding