As Juliette mentioned, we have defined the opening of the 14 cm thick Pb collimator with the general trapezoid volume TRAP:
The new geometry defintion can be found here.
The original collimator definition pieced together odd shapes to define the opening. Using trap's is a much easier and cleaner way to define things. However, there are limitations to this method because the sides of the trap must be coplanar, which restricts us slightly in what values we can use on the corners. We are hoping that it will be easier to look at how changing the phi angle of the sides affects the backgrounds and the figure of merit. This is in the beginning stages, this first definition has the phi angle opening slightly. We need to try to define the volumes with straight sides so we can compare results directly to the original. For a rough idea, here are some values:
Table 1: 14 cm thick Pb collimator
| FOM | Elastic Photons | Elastic Photons from coll. region | |
| orig. | 4.223% | 0.0533% +/- 0.0021% | 0.0428% +/- 0.0018% |
| trap | 4.239% | 0.0520% +/- 0.0021% | 0.0464% +/- 0.0020% |
Initial reviews show that the electron envelope is unchanged, but Juliette gave me a nifty kumac to draw the QTOR support structures over plots of the envelope at possible interference locations, and I still need to check those. Overall, as I said before, this is in the very first stages, some tweaking still needs to be done.
Bronze Alloy
We were asked to consider the bronze alloy due to its ease of precision machining. This is 70% Cu, 25% Pb, and 5% Sn. More information can be found at the companies website, here.
25 radiation lengths of this material corresponds to 27.0573 cm. Comparing this to the Pb collimator:
Table 2: 25 radiation length collimator
| Material | FOM | Elastic Photons | Elastic Photons from coll. region | Inelastic Photons | Inelastic Electrons |
| Pb | 4.223% | 0.0533% +/- 0.0021% | 0.0428% +/- 0.0018% | 0.0014% +/- 0.0001% | 0.0125% +/- 0.0005% |
| CuPb | 4.236% | 0.0761% +/- 0.0018% | 0.0643% +/- 0.0025% | 0.0023% +/- 0.0001% | 0.0123% +/- 0.0005% |
The geometry file for the CuPb collimator with the new material definition can be found here.