1) We are calculating things now with the "correct" efficiency formulas, which increases the photon backgrounds slightly.
2) For now we are leaving helium in the collimator region only until we are satisfied we have cut down the background coming from there.
3) We are leaving the photoelectric effect turned off for now, we will turn it on after we finish the analysis of the collimator background to see what kind of effect it has.
Here is an overview of different geometries where each Case has
and the cases are:
- A) no lintel
- B) with lintel
- Case -1: VT Collimator + floor + no wall
- Case 0: VT Collimator + floor + 50 cm concrete wall
- Case 1: VT Collimator + floor + 50 cm lead wall
- Case 2: Reducing theta_max of VT collimator to 10.25 + floor + 50 cm lead wall
- Case 3: Yongguang's collimator (25 cm upstream, 5.25 cm thick W + lead, theta_max 10.25) + floor + 50 cm lead wall
There is a lot of information presented in this table, but right now we can just focus on the elastic photon background - which is what we are trying to reduce by adding the lintel. The motivation for Yongguang reducing theta_max and moving the collimator upstream were to increase the separation between the photons and the electrons at Z=-80, where the lintel was placed (see images below). First, the tabl:
Table #: Table
| Elastic Photons | Elastic Photons from coll. region | Inelastic Photons | Inelastic Electrons | Moller Photons | Moller Electrons | |
| -1 A | 0.190377% +/- 0.004904% | 0.046164% +/- 0.001925% | 0.002537% +/- 0.000123% | 0.015341% +/- 0.000620% | 0.708639% +/- 0.027255% | 0.780017% +/- 0.051211% |
| -1 B | 0.163549% +/- 0.004788% | 0.016341% +/- 0.001141% | 0.001447% +/- 0.000095% | 0.016235% +/- 0.000630% | - | - |
| 0 A | 0.231946% +/- 0.005119% | 0.048369% +/- 0.001976% | 0.034644% +/- 0.000513% | 0.234147% +/- 0.003133% | - | - |
| 0 B | 0.210199% +/- 0.005125% | 0.018953% +/- 0.001290% | 0.031204% +/- 0.000485% | 0.231683% +/- 0.003109% | - | - |
| 1 A | 0.204375% +/- 0.004862% | 0.044000% +/- 0.001901% | 0.015188% +/- 0.000319% | 0.062165% +/- 0.001520% | 0.557065% +/- 0.023797% | 0.300599% +/- 0.038176% |
| 1 B | 0.190644% +/- 0.005052% | 0.015059% +/- 0.001049% | 0.014251% +/- 0.000314% | 0.060140% +/- 0.001514% | 0.181706% +/- 0.012392% | 0.130086% +/- 0.022996% |
| 2 A | 0.223063% +/- 0.005299% | 0.037380% +/- 0.001772% | 0.020730% +/- 0.000433% | 0.074769% +/- 0.001854% | - | - |
| 2 B | 0.191558% +/- 0.004774% | 0.015819% +/- 0.001092% | 0.017439% +/- 0.000382% | 0.072529% +/- 0.001838% | - | - |
| 3 A | 0.203853% +/- 0.004984% | 0.030238% +/- 0.001607% | 0.019698% +/- 0.000410% | 0.071440% +/- 0.001850% | 0.343130% +/- 0.018059% | 0.130074% +/- 0.025033% |
| 3 B | 0.173794% +/- 0.004778% | 0.001828% +/- 0.000318% | 0.018821% +/- 0.000407% | 0.068924% +/- 0.001819% | 0.117567% +/- 0.011641% | 0.118366% +/- 0.026467% |
We can look at the xy position of the photons and electrons at Z=-80 and compare the separation for the 3 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
and get the images for the xy projection (click on image for full size):
| VT collimator, theta_max = 10.53 | VT collimator, theta_max = 10.25 | Yongguag's 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. I'm going to be showing you these images on the scale of the photon projection, so just as a reference you can see that the electrons peak much much higher than the photons:
So focusing in on the overlap:
*VT collimator, theta_max = 10.53:
*VT collimator, theta_max = 10.25
*Yongguag's collimator, theta_max = 10.25
Conclusions