Difference between revisions of "List of changes since the 2006 HallD Tagging Spectrometer and Photon Beamline Review"
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# electron beam dump -- in 2006 the electron beam dump was located in an out-building that was connected to the tagger hall by a buried beam pipe. The present civil design now has the electron beam dump located in the tagger hall, which has been extended in the south-east direction to accommodate it. | # electron beam dump -- in 2006 the electron beam dump was located in an out-building that was connected to the tagger hall by a buried beam pipe. The present civil design now has the electron beam dump located in the tagger hall, which has been extended in the south-east direction to accommodate it. | ||
# electron beam emittance -- in 2006 the horizontal emittance of the 12 GeV electron beam predicted by ray-tracing simulations was 1 x 10<sup>-8</sup> m-r. Since then, a bug in the simulation was corrected, leading to a reduced estimate of 5 x 10^<sup>-9</sup> m-r. | # electron beam emittance -- in 2006 the horizontal emittance of the 12 GeV electron beam predicted by ray-tracing simulations was 1 x 10<sup>-8</sup> m-r. Since then, a bug in the simulation was corrected, leading to a reduced estimate of 5 x 10^<sup>-9</sup> m-r. | ||
| + | # radiator crystal size requirement -- in 2006 the requirement on the transverse dimension of the diamond crystal radiator was set at 8 mm minimum in order to contain the electron beam spot out to 2 standard deviations. Since then a new configuration has been found of the electron beam lattice that reduces the horizontal beam spot size to 1 mm rms. Based on this, the minimum transverse diamond radiator size requirement has been reduced to 4 mm. | ||
| + | # electron beam halo requirement -- in 2006 we set a conservative requirement of 10<sup>-6</sup> on the fraction of the current that resides in the tails (outside the central Gaussian peak) of the electron beam. Considerable work has been done since that time on refining this specification and simulating the impact of halo on tagger performance. The new halo specification requires that no more than 1 x 10<sup>-5</sup> of the electron beam current lie outside a cylinder of radius 5 mm centered on the nominal beam axis. | ||
Revision as of 10:32, 10 June 2010
In January 2006 the lab held an external review of the Hall D Tagging Spectrometer and Beam Line. The list below represents an attempt to collect in one place all of the changes to the tagger and photon beam line that have taken place since then, up until the PAC report in summer 2010.
- electron beam dump -- in 2006 the electron beam dump was located in an out-building that was connected to the tagger hall by a buried beam pipe. The present civil design now has the electron beam dump located in the tagger hall, which has been extended in the south-east direction to accommodate it.
- electron beam emittance -- in 2006 the horizontal emittance of the 12 GeV electron beam predicted by ray-tracing simulations was 1 x 10-8 m-r. Since then, a bug in the simulation was corrected, leading to a reduced estimate of 5 x 10^-9 m-r.
- radiator crystal size requirement -- in 2006 the requirement on the transverse dimension of the diamond crystal radiator was set at 8 mm minimum in order to contain the electron beam spot out to 2 standard deviations. Since then a new configuration has been found of the electron beam lattice that reduces the horizontal beam spot size to 1 mm rms. Based on this, the minimum transverse diamond radiator size requirement has been reduced to 4 mm.
- electron beam halo requirement -- in 2006 we set a conservative requirement of 10-6 on the fraction of the current that resides in the tails (outside the central Gaussian peak) of the electron beam. Considerable work has been done since that time on refining this specification and simulating the impact of halo on tagger performance. The new halo specification requires that no more than 1 x 10-5 of the electron beam current lie outside a cylinder of radius 5 mm centered on the nominal beam axis.
