Optics Meeting Oct 25 2022 230PM ET

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  • GEM frame implementation into Geant4 (Bill)[1]
  • Low energy electron processes for Livermore em library (Kate) [2]
  • Optics_update_25Oct (Vassu)[3]


Kate, Vassu, Zuhal, David, Bill, James, Nathan


  1. (Kate) - Further debugging in use of Livermore libraries. 1) tried adding /process/em/lowestElectronEnergy 100 keV, didn't seem to stop lower energy electrons from being tracked/getting stuck. 2) tried eIoniModelSetLowEnergyLimit (100*keV) (was 200 MeV): not sure of it is doing what we want, see 465 keV electron which undergoes energy loss via bremss, but not ionization. The events that get stuck with many steps and no ionization loss all seem to be in magnet coils, and undergo "CoupledTransportation". Maybe want to limit this process based on energy threshold and/or number of steps? Lack of ionization still a puzzle to be solved.
  2. (Bill) - working on more realistic geometry for Al frame for the GEMs (the very thin G10 frame is less relevant than the 7 mm Al frame). Using "subtractions" to generate geometry; Vassu suggests "nested volumes" may be better for processing speed. Will put into remoll, and test effect of frames/no frames on processing time for modest number of Moller events.
  3. (Vassu) - a) Trying to improve 12C/Moller separation in pass 1 by looking at r' and not just r: doesn't solve the issue. b) tried single 12C foil for pass 1 (just the DS foil, since the US is mainly out of the core Moller acceptance anyway at this beam energy); this seems to really help, most holes clearly separated; still an issue with holes 61 and 41 at one-pass. Perhaps try reducing hole diameter for these holes (9 mm -> 5 mm?). d) Looking at one-foil results from pass 2 - the double peak in the theta residual (due to confusing of the two foils goes away: good. e) Looking at fit parameters for theta vs. beam pass, including 5 beam energies, for case in which we have a 15 parameter fit (using all 4 GEM variables). Don't see simple/smooth evolution with beam energy. Maybe overfitting? Will instead try reduced parameterization, with only fitting to r and r'. May need to look at smaller steps in beam energy also. We may want some data with single foil targets, some with multiple foils.

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Meeting ID: 972 5975 5403

Passcode: 4937

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