Primary Collimator Live Page
Katherine's Status Report
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Michael's Web Page
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Burnham's collimator pics
Region III status report
Tony's Status Report
Keep Out Zones a la Allena
Previous Reports
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Qweak elog at JLab
Qweak Simulation Forum
Virginia Tech Update for Tracking Group,
Collimator simulation/design:
From primary collimator report*:
"Additional tasks are necessary to finalize the primary collimator design. This working group did not consider backgrounds other than inelastics in the design of the current collimation system. The sides of the collimator are not slanted at all, and the top and bottom edges of the collimator may not have the optimum slant. The upstream cleanup collimator design was more carefully done than the downstream cleanup collimator, because of the impact of the moller rates at the Region II drift chambers, so a more careful design of this (cleanup) collimator(s) is suggested. In addition, no consideration has been paid to the possibility of detector shielding.
Other tasks include ``replacing'' the beamline and shielding, while taking into account the needs of the downstream luminosity monitors. The question of running with minitorus off during production running and on during tracking has to be solidified. The dose on the minitorus and QTOR and the support structures has not been calculated, and the choice of material for the three collimators has not yet been made."
*The items in bold are those that were never looked into in detail. Unless somebody thinks one of those is important to look into, we suggest going with the current design. The current design defines an acceptance that gives us an acceptable error on Qweak with all factors considered (statistics, hadronic contamination, inelastic contamination). It has also been shown that photon backgrounds coming from the primary collimator in the current design can be managed with lintels.
Other issues that may need attention are:
Sizes of slabs:
After Paulo determines the outer size of the collimator slabs from "line-of-sight" considerations, it might be useful to check the backgrounds again in simulation.
Cleanup collimators:
It is important to realize that not a lot of effort went into the dimensions of the holes in the cleanup (#1 and #3) collimators. The dimensions of the hole in Collimator #3 are probably okay, because Katherine has shown that having it in or out doesn't affect the elastic electron acceptance at the focal plane, so it isn't clipping. For the first collimator, things should be looked at. It was initially set for the VT collimator, and it wasn't readjusted when we adopted the 25 cm upstream location. At the minimum that should be done. Also, by opening those apertures up a bit, it may be possible to install the "upstream luminosity monitors" on the front face of the primary (collimator #2) collimator.
The following plots show the acceptances of the cleanup collimators for the 25cm upstream collimator (made of lead, but as thick as the bronze would be).
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Figure 1 - This plot (for the original) formed the basis of the choice of size for the 1st collimator. |
Figure 2 - This plot (for the original) formed the basis of the choice of size for the 3rd collimator. |
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Figure 3 - This plot shows that the clearance at the 1st collimator is maybe to small? |
Figure 4 - This plot shows that the clearance at the 3rd collimator is probably okay. |
See acceptances for original VT row 20 collimator for comparison.
Crude idea for locating upstream luminosity monitors at collimator 2 location
Drift chamber:
We have constructed and are testing a full-size six plane (xuvxuv) drift chamber. Pictures are posted but no tracking results yet. We are going to adapt the HKS tracking code to use for our chambers. Work in progress.
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Figure 5 - Partially assembled chamber of the new design. |
Figure 6 - Chamber with both Al faces; you can see the vacuum window. |
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Figure 7 - Card supports and cabling for new chamber design. |
Figure 8 - High voltage connectors in new chamber design. |
