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GWU Status Report: 6-22-06

GWU Status Report: 6-22-06




Before we move on to anything new, we want to verify that we are doing things right by reproducing the results that Yongguang reported. These results come from his two status reports: 12-30-05 status report and 2-6-06 status report. This report serves as a reminder of what he was working on and to report my progress in reproducing his results. This has been a hard task, because his logbook is missing so the only numbers we have to go by are what he reported. Also, not all the geometry files are available or labeled well.

I am using Yongguang's executable, bash files, and geometry files.

Also, the formula Yongguang used to calculate uncertainties, which I used to find the uncertainties reported in this status report, underestimates the uncertainty. After we are able to reproduce the results, we will look into this further.


Case 1

"Case 1" is reported to be the standard VT collimator from line 20, with the addition of a 50 cm thick lead shield wall with a window having 2 cm clearance. On his computer, I found a geometry file called "qweakfinal.euclid_vt." This geometry file had a shield wall with 2 cm clearance + 4 cm tungsten, so I tried this and also changing it to 2 cm clearance as he proposed it was in his report.

Table 1 shows the rates for

Table 1: Comparison of "Case 1" results.
Elastic Photons Elastic Photons from coll. region Inelastic Photons Inelastic Electrons Moller Photons Moller Electrons
A 0.21% 0.038% 0.014% 0.12% 0.44% 0.183%
B 0.2091% +/- 0.0052% 0.0383% +/- 0.0018% 0.0138% +/- 0.0003% 0.1194% +/- 0.0022% 0.4366% +/- 0.0216% 0.1831% +/- 0.0259%
C 0.2017% +/- 0.0051% 0.0378% +/- 0.0020% 0.0188% +/- 0.0004% 0.0738% +/- 0.0018% 0.5320% +/- 0.0254% 0.2432% +/- 0.0322%

Important Point: Yongguang claims the window with 2 cm clearance yields the rates reported. However, I found that this was not the case. The rates reported for "case 1" in his 12-30-05 status report come from a window design that has 2 cm clearance and 4 cm tungsten lining the edge of the window.


Case 2

"Case 2" is reported to be different from case 1 by:

and should have a shield wall window with 2 cm clearance. Yongguang does not provide or reference this geometry file. However, in his report Yongguang links the geometry file for case 3 (see below). The only difference between case 2 and case 3 is the lintel. Ideally, we should be able to get a geometry file for case 2 by commenting out the lintel in case 3.

The case 3 geometry file does not work, so hence case 2 does not work yet. Once we get case 3 to work, case 2 should follow easily. To see a table comparing the results that Yongguang reports as well as two versions I tried click here.


Case 3

"Case 3" is reported to be different from case 2 by the addition of a 5.25 cm thick x 16 cm high x 56 cm wide tungsten lintel positioned at Z = -80 cm.

As mentioned before, this geometry file is in his report. However, this geometry file does not produce the rates reported. I tried two configurations

Table 2: Comparison of "Case 3" results.
Elastic Photons Elastic Photons from coll. region Inelastic Photons Inelastic Electrons Moller Photons Moller Electrons
Yongguang 0.16% +/- 0.0045% 0.004% 0.013% +/- 0.00032% 0.041% +/- 0.0014% 0.11% +/- 0.01% 0.125% +/- 0.036%
Katherine A 0.1709% +/- 0.0050% 0.0018% +/- 0.0003% 0.0175% +/- 0.0004% 0.0689% +/- 0.0018% 0.1117% +/- 0.0118% 0.1184% +/- 0.0265%
Katherine B 0.1705% +/- 0.0052% 0.0023% +/- 0.0004% 0.0139% +/- 0.0004% 0.1171% +/- 0.0023% - -


Case's 3 a-c

Yongguang created variations of "case 3" with different, realistic shield wall configurations (some amount of lead + concrete). He started with case 3 (primary collimator moved 25 cm upstream, lintel present) and tried three configurations:


See his report for more information. In his report he does indentify the geometry file used for case 3c so we were able to copy it from his computer. These rates are reproducible. From looking at the rates it seems that configuration B) is the best, however 4 inches of lead is still not feasible. This leads to the studies Yongguang did in report 4.


Case's 4 a-d

These cases are from the 2-6-06 status report. Everything is the same as case 3 except the shield wall. Cases 4 a-c have

where the thickness of the tungsten shielding varies. Case 4 d has the same setup except the window has 4 cm + 2 inch clearance. The thickness of the tungsten "tooth" for each case is:
He has the geometry for case 4d on his report and these rates are reproducible. From looking at his rates we conclude that a) and d) are essentially the same and better than b), c), and case 3.


Conclusions