Compton Scattering James Durgin Physics 521 March 19, 2009
Background Collecting energies at several points lets one find electron mass and cross section Image from user-review.ca
Photomultiper tube Scintillator Lead shielding Copper cylinder Source inside shielding
Experimental Theory Calibrate multichannel analyzer Collect energy spectrums with copper cylinder Collect energy spectrums without copper cylinder Fit points to find electron mass and experimental cross section
Calibration Isotope First Decay Energy First Decay Percentage Second Decay Energy Second Decay Percentage Co keV85.60% keV10.60% Co keV100% keV100% Cs keV85.10% Ba keV62.10% Isotope energies v. channel number
Energy Spectrums Counts per channel v. channel number Net counts v. channel number
Slope (inverse electron mass) % interval( , ) Y intercept7.23E-05 95% interval(1.04e-05, ) Degrees of freedom9 R2R Electron mass503.8 keV Uncertainty± 14.6 keV Graphical Compton’s Equation Net counts v. channel number Fit for Compton Scattered Photons
Cross section comparison Collected data follows Klein-Nishina cross section Thomson cross section Thomson equation Klein-Nishina cross section Klein-Nishina equation
Uncertainty Analysis Statistical nature of counts Setup uncertainty Conversion uncertainty Negligible events
Conclusion Experimental electron mass of ± 14.6 keV v. actual electron mass of ± keV Collected data has closer agreement with Klein-Nishina model