March 9, 2006 Meeting

Attending: Josh, Stan, Chris, Dan, Bill S., Matt

Agenda

Reports

Neutron leakage plots from Matt:

Goal: compare neutron "leakage" around the acrylic sphere between RAT v0.1 and ReactorFsim. This tests the material compositions and neutron cross-section data between the two simulations.

Method: Select events with IBD vertex within +/- 20 cm of the Gd/no-Gd boundary (the inner edge of the acrylic sphere at R = 260 cm). For each of these samples (240 < Rgen < 260 cm and 260 < Rgen < 280 cm) plot the simulated location of the eventual neutron capture.

ReactorFsim: generated 200k IBD events out to R = 350 cm.
RAT v0.1: generated 20,500 IBD events filling the scintillator, acrylic and oil regions evenly by volume.

Results:

For RAT v0.1:
Events generated inside scint:
Total = 1772 (4.8% of generated)
Captured inside scint = 1686 (91.3%)
Captured outside scint = 86 (8.7%)

Events generated outside scint:
Total = 2376 (5.5% of generated)
Captured inside scint = 435 (34.3%)
Captured outside scint = 1941 (65.7%)

For ReactorFsim:
Events generated inside scint:
Total = 9236 (4.6% of generated)
Captured inside scint = 8406 (91.0%)
Captured outside scint = 830 (9.0%)

Events generated outside scint:
Total = 9837 (4.9% of generated)
Captured inside scint = 3294 (33.5%)
Captured outside scint = 6543 (66.5%)

Conclusion: the neutron leakage is idential to within the statistical reach (driven by the number of RAT events) of these samples.

Minutes

Stan plans to run the BW geometry in SNOMAN to compare Cherenkov light from 5 MeV electrons. He hopes to also run the SNO layout in RAT. To do this he has updated tracking variables to tag Cherekov and reemission photons. This will take several weeks to get going.

Chris has studied the angular response of the PMT (angle of incoming photon to PMT-looking direction). There is a possible problem in how reflections are handled, where a totally reflected photon will produce a PE inside the tube. He reports that G4 handles up to the oil/glass boundary, and GLG4sim takes over inside the glass and produces the PE. Thus this is a possible GLG4sim bug. Hopes for a fix in about 1 week.

Bill S. has time to work. He will talk to Matt and Stan about possible projects.

Dan is working on neutron capture in the simulation. He reports that the gammas from 155Gd capture do not always sum to the total expected energy, on the order of a 20 keV effect. He hopes to have a fix by the end of next week. He also reports that the fraction of H captures may be low relative to Gd.

Matt reported his neutron leakage study above. Matt also will assemble a list of our changes to GLG4sim for future reference.

Next Meeting(s)