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Validation of electron multiple scattering 13 to 20 MeV Daren - - PowerPoint PPT Presentation
Validation of electron multiple scattering 13 to 20 MeV Daren - - PowerPoint PPT Presentation
Validation of electron multiple scattering 13 to 20 MeV Daren Sawkey September 29, 2015 Geant4 collaboration meeting Experiment: Ross et al., Med. Phys. 35 , 4121 (2008) 7 materials, various thickness, 13 and 20 MeV Simulation:
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- 1. Width of Gaussian fit to central part
- 2. Overall goodness of fit
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Improvements:
- Use physics lists from Geant4 source rather than local
- same # of incident particles for each physics list (previously SS was 10%)
- calculation of p-value
- Include simulation, measurement uncertainties in chi-squared
Simulation uncertainty: Measurement uncertainty: 1% in width—what is it for each data point?
determine empirically
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Width good, chi-sq good
Examples
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Width good, chi-sq poor
Examples
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Width poor, chi-sq poor
Examples
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What is the uncertainty of the measured data points?
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Assume 0% measurement uncertainty
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Assume 1% measurement uncertainty
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Assume 2% measurement uncertainty
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Summarize results
- Calculate average chi-square
- Root-mean-square (ratio of widths – 1)
- Express as %
- Function of Geant4 version
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20 MeV
ratio of widths
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Chi-squared
20 MeV 20 MeV
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20 MeV
p-value
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IDEAL
All data vs. version: Widths
1-
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IDEAL
All data vs. version: chi-square
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All data vs. version: p-value
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Examples of two problems found
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LateralDisplacementBeyondSafety
- n
- ff
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Step Limit
Boundary Safety SafetyPlus
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TestEm5, 10 MeV e- through 10 um Cu
Distance to boundary: msc limits step; strict near boundary SafetyPlus: msc doesn’t limit step in absorber.
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