1. Compton Scattering James Durgin Physics 521 March 19, 2009

2. Background Collecting energies at several points lets one find electron mass and cross section Image from user-review.ca

3. Photomultiper tube Scintillator Lead shielding Copper cylinder Source inside shielding

4. 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

5. Calibration Isotope First Decay Energy First Decay Percentage Second Decay Energy Second Decay Percentage Co-57122.06 keV85.60%136.47 keV10.60% Co-601173.24 keV100%1332.50 keV100% Cs-137661.66 keV85.10% Ba-133356.02 keV62.10% Isotope energies v. channel number

6. Energy Spectrums Counts per channel v. channel number Net counts v. channel number

7. Slope (inverse electron mass)0.001985 95% interval(0.001928, 0.002043) Y intercept7.23E-05 95% interval(1.04e-05, 0.0001342) Degrees of freedom9 R2R2 0.9984 Electron mass503.8 keV Uncertainty± 14.6 keV Graphical Compton’s Equation Net counts v. channel number Fit for Compton Scattered Photons

8. Cross section comparison Collected data follows Klein-Nishina cross section Thomson cross section Thomson equation Klein-Nishina cross section Klein-Nishina equation

9. Uncertainty Analysis Statistical nature of counts Setup uncertainty Conversion uncertainty Negligible events

10. Conclusion Experimental electron mass of 503.8 ± 14.6 keV v. actual electron mass of 510.998910±0.000013 keV Collected data has closer agreement with Klein-Nishina model