Discussion of e+/e- tertiary beams in Hall D
From GlueXWiki
- Running conditions of 2-photon experiment in Hall B, based on numbers in this talk by Robert Bennett
- primary beam energy: 5.5 GeV
- max beam current: 120 nA
- radiator thickness: 0.009 radiation lengths
- max power in photon beam: 5.9 W
- For comparison, here are the maximum design numbers for polarized running with GlueX. Note that these rates are a bit higher than the standard high-luminosity running conditions, but these are the upper limits that we simulated when we designed the collimator cave shielding and beam line instrumentation.
- primary beam energy: 12 GeV
- max beam current: 3 μA
- radiator thickness: 0.00014 radiation lengths (20 micron diamond)
- max power in photon beam: 4.8 W
- Imagine just taking the running conditions from the TPE experiment in Hall B and replicate them in Hall D, sticking as close as possible to the GlueX photon beam configuration.
- primary beam energy: 12 GeV
- max beam current: 3 μA
- radiator thickness: 0.00036 radiation lengths (50 micron diamond)
- max power in photon beam: 12 W
- The radiator thickness was increased just enough to get the same photon beam intensity as the Hall B experiment. Notice that the total photon beam is only a factor 2.5 higher absorbed dose in the collimator cave than expected for high-luminosity running in GlueX. A more conservative configuration with the same photon beam power might be the following, with the same photon beam intensity.
- primary beam energy: 12 GeV
- max beam current: 300 nA
- radiator thickness: 0.0036 radiation lengths (500 micron diamond)
- max power in photon beam: 12 W
- Another idea to think about:
- O(m/E) precollimation of photon beam at exit from tagger hall would give factor 2.7 reduction in beam power, also harden the spectrum.
- 1m/E collimator @ 30m (radiator - tagger hall exit) has diameter 2.6mm which is feasible in terms of alignment and beam focal spot size. Under these conditions, the following would apply.
- primary beam energy: 12 GeV
- max beam current: 300 nA
- radiator thickness: 0.0025 radiation lengths (500 micron diamond)
- max power in photon beam: 4.5 W
Now one is fully within the limits of the beamline design for GlueX, in terms of photon beam power being incident at the collimator cave.
