Collimator
JLAB Collimator design 6/14/07
On June 14, 2007, I went to Paulo Dedeiros's office on the 5th floor of the ARC cubicle 43 (500-43). He output the pdf file below which describes the back side of the first collimator in Qweak.
I can then compare the dimensions on this version with the version I recieved back in 12/3/06.
summary
I do not see any major changes so I conclude that the collimator has not changed and the montecarlo results for the profiles of elastic electrons are still valid.
JLAB Collimator design 8/7/07
From Paulo's Drawing "Hall -V QWEAK EXPERIMENT COLLIMATOR BUNKER SETUP UPSTREAM CLEAUP COLLIMATOR" # 67503-E-00021 dated 8/8/07 I saw the following description of what I believe is the backside of collimator 1.
Summary
It looks like the collimator has a new lower radial limit of 7.03 cm compared with the previous limit of 6.2 cm shown in the drawing on 6/14/07 above. This gives us about 8.3 mm of more space for chamber material between the beam pipe and the collimator opening at the backside of the first collimator.
The smallest width of the collimator is now 3.82 cm. Measuring the width of the already manufactured GEM foils for Qweak, I see the smallest width is 4 cm. The width is 4.5 cm at a radial distance of 0.8 cm away from the edge of the GEM foil. If the GEm detector were placed right up against the backside of Collimator 1 then there would be more than enough space. We will need to look at elastic electron profile to determine how things look at the GEM location.