There are 6 geometries:
1) VT collimator design, theta_max = 10.53
2) VT collimator design, theta_max = 10.25
3) YL collimator design: theta_max = 10.25, moved 25 cm upstream, reduced to 5.25 cm thick tungsten, 11.2 cm Pb behind, 3rd collimator changed (clearance decreased by 1 cm)*See note below
4) YL2 collimator design: YL collimator, but returning 3rd collimator to original design
5) GW collimator design: theta_max = 10.25, left at VT position, reduced to 5.25 cm thick tungsten, 11.2 cm Pb behind
6) GW2 collimator design: GW collimator, but with Yongguang's 3rd collimator
*Note: While looking closer at the geometries I found that Yongguang also changed the 3rd collimator: he increased the lower radii by 1 cm and decreased the upper radii by 1 cm (i.e.: on the downstream face of the collimator her changed 39.5 -> 40.5 and 82 -> 81).
First, looking at the backgrounds for NO LINTEL
Table 1: Elastic photon backgrounds, no lintel
| Elastic Photons | Elastic Photons from coll. region | |
| VT 10.53 | 0.188331% +/- 0.003381% | 0.052232% +/- 0.001505% |
| VT 10.25 | 0.198938% +/- 0.003600% | 0.051386% +/- 0.001497% |
| YL 10.25 | 0.203228% +/- 0.003557% | 0.031570% +/- 0.001155% |
| YL2 10.25 | 0.178552% +/- 0.004684% | 0.045991% +/- 0.001954% |
| GW 10.25 | 0.174815% +/- 0.004503% | 0.043505% +/- 0.001816% |
| GW2 10.25 | 0.182637% +/- 0.003292% | 0.046623% +/- 0.001369% |
Conclusions:
- GW abd YL2 are lowest, followed by VT 10.53, which are lower than VT 10.25 and YL designs for photons coming from all space.
- YL design is lowest for collimator region photons, followed by the rest, with the VT designs having the highest.
Next, the backgrounds for WITH LINTEL:
Table 2: Elastic photon backgrounds, with lintel
| Elastic Photons | Elastic Photons from coll. region | |
| VT 10.53 | 0.163549% +/- 0.004788% | 0.016341% +/- 0.001141% |
| VT 10.25 | 0.152613% +/- 0.004550% | 0.016943% +/- 0.001153% |
| YL 10.25 | 0.139216% +/- 0.004463% | 0.005013% +/- 0.000637% |
| YL2 10.25 | 0.151495% +/- 0.004772% | 0.005486% +/- 0.000634% |
| GW 10.25 | 0.158447% +/- 0.004720% | 0.015568% +/- 0.001072% |
Conclusions:
- YL is the lowest, followed by the rest with VT 10.53 having the highest background from all space.
- The lintel best reduces the collimator regions for the YL designs.
- YL is the best, however - what about the 3rd collimator?
We can look at the xy position of the photons and electrons at Z=-80 and compare the separation for the 5 major geometries:
1) VT collimator design, theta_max = 10.53
2) VT collimator design, theta_max = 10.25
3) Yongguang's collimator design: theta_max = 10.25, moved 25 cm upstream, reduced to 5.25 cm thick tungsten, 11.2 cm Pb behind
4) GW collimator design: theta_max = 10.25, left at VT position, reduced to 5.25 cm thick tungsten, 11.2 cm Pb behind
6) GW2 collimator design: GW collimator, but with Yongguang's 3rd collimator
| VT collimator, theta_max = 10.53 | VT collimator, theta_max = 10.25 |
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| Yongguag's collimator, theta_max = 10.25 | GW collimator, theta_max = 10.25 |
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| GW2 collimator, theta_max = 10.25 | |
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We can also look at just the x projection at Z=-80 to get a better idea of the separation.
| VT collimator, theta_max = 10.53 | VT collimator, theta_max = 10.25 |
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| Yongguag's collimator, theta_max = 10.25 | GW collimator, theta_max = 10.25 |
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| GW2 collimator, theta_max = 10.25 | |
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Conclusions? - Yongguang's collimator seems to be the best if using a lintel is desired. It creates the most separation between the electrons and photons and in the end has the lowest elastic photon background.(Note to self: something to do in the future is study the lintel position more - how precise does the location need to be? Right now Yongguang has the y position centered at 126.74064, so what effect does it have to make a +/- .5 cm change?)