General Comments: Unless otherwise specified, the geometry has the three collimators, the concrete collimator vault, QTOR coils, lintels, basic beamline, and upstream wall of the shielding hut. All backgrounds are weighted by cross section, photoelectric efficiency, and asymmetry. The beam is 4x4 mm^2 and events were generated in one octant, theta = 2.5-19.5 degrees and phi = -17-17 degrees.
No Lintel
For a basis of comparison, here are the backgrounds for the geometry with the lintel removed:
Table 1: Backgrounds for the geometry without a lintel
Elastic Photons Elastic Photons coll Inelastic Photons Inelastic Electrons Moller Photons Moller Photons coll Moller Electrons no lin 0.2199+/-0.0058 0.0574+/-0.0024 0.0855+/-0.0015 0.5317+/-0.0099 0.9228+/-0.0286 0.7731+/-0.0259 0.3557+/-0.0339
Z Location
The current lintel is positioned so that the front face is at Z=-80 cm (with a total thickness of 8.4 cm). The position should be 2 cm above the electron envelope. For the current lintel the positioning is actually incorrect if you define the top of the envelope at 0.1% of the peak (like we did in for the envelope in the wall). All of the events at these locations are about 0.1% of the peak so you end up including all the random events. Could be that I just didn't run enough statistics? If you look at a second random seed we see the following where the first blue line is the 'cutoff' originally and the second blue line is the 'cutoff' with the 0.1% method:
Figure 1: Upper edge of the elastic electron profile at Z=-80 for two random seeds
We could also generate twice as many events to see how the cutoff changes, and then we see the following:
Figure 2: Upper edge of the elastic electron profile at Z=-80 for 1 and 2 million events
So this makes the 0.1% cutoff seem much too high. But the difference is only 1.2 cm, and since the separation between the photons and electrons at Z=-80 should > 5cm, the extra distance shouldn't be a problem. I did compare old vs. new and the results are in the table, as well as this image comparing the z origin of elastic photons:
Figure 3: Comparing the Z origin of elastic photons for the old and new Z=-80 lintels
Below is a table comparing backgrounds for lintels at different locations
Table 2: Backgrounds for lintels at different Z locations
Z Elastic Photons Elastic Photons coll Inelastic Photons Inelastic Electrons Moller Photons Moller Photons coll Moller Electrons -80 old 0.1629+/-0.0053 0.0059+/-0.0007 0.0762+/-0.0015 0.5442+/-0.0101 0.2192+/-0.0127 0.0745+/-0.0064 0.2323+/-0.0288 -80 new 0.1684+/-0.0055 0.0077+/-0.0008 0.0745+/-0.0015 0.5482+/-0.0101 0.2063+/-0.0129 0.0727+/-0.0065 0.2034+/-0.0260 -70 0.1731+/-0.0056 0.0075+/-0.0008 0.0684+/-0.0013 0.5419+/-0.0100 0.2011+/-0.0120 0.0984+/-0.0080 0.2197+/-0.0299 -60 0.1647+/-0.0052 0.0068+/-0.0007 0.0671+/-0.0013 0.5181+/-0.0098 0.2379+/-0.0138 0.1315+/-0.0100 0.1861+/-0.0251 -50 0.1608+/-0.0052 0.0084+/-0.0009 0.0670+/-0.0013 0.5470+/-0.0100 0.2594+/-0.0146 0.1280+/-0.0094 0.3018+/-0.0346
Link #1: Side view images of triggered events may help determine where a good location is. See the images here.
And below are some x-projections of everything (not just accepted events) that hits at Z=-80, Z=-70, and Z=-60 (the lower edge of the lintel at these locations are X=119.6, X=121.5, X=124.4):
Figure 4: X projection of Elastic Photons:
| Figure 5: X projection of a) Inelastic Photons: | b) Inelastic Electrons: |
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| Figure 6: X projection of a) Mollers Photons: | b) Moller Electrons: |
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| Figure 7: X projection of accepted mollers photons (with lines representing lintel coverage) for a) Z=-80: | b) Z=-70: |
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And here are images comparing the origin of backgrounds for the four cases (Z-80: new, Z-70, Z-60, Z-50): links
Link #2: Elastics
Link #3: Inelastics
Link #4: Mollers