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Compton Scattering Experiment

Compton Scattering Experiment. John Klumpp And Ainsley Niemkiewicz. What is Compton Scattering?. Occurs when incident photon interacts with free electron Produces scattered photon and recoil electron. What Does it Predict?.

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Compton Scattering Experiment

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  1. Compton Scattering Experiment John Klumpp And Ainsley Niemkiewicz

  2. What is Compton Scattering? • Occurs when incident photon interacts with free electron • Produces scattered photon and recoil electron

  3. What Does it Predict? • The energy of the scattered photon is dependent on the angle of its deflection. • Expressing energy in terms of wavelength, this relation reads: • Or, alternatively,1/E – 1/Eo = m-1(1 – cos(θ))

  4. What About the Scattering Cross Section? • This is predicted by the Klein-Nishina Formula:

  5. What Does Measuring Compton Scattering Tell Us? • Electron Mass • Highly suggestive of the particle properties of photons • Refutes Classical Scattering

  6. How Do We Measure Compton Scattering? • Scatter gamma rays from a Cesium137 source against a copper target • Detect scattered photons using scintillation detector which revolves about the target

  7. Calibrate MCA using peaks of Cs137, Ba133, Co57, and Co60 and their known energies • Collect data for angles 30-90 in increments of 10, and angles 105-150 in increments of 15

  8. Calibration Data

  9. Scattering Data

  10. Energy Peaks • Subtract background • Calculate energy at each angle

  11. Energy vs. Angle The slope of this line represents the inverse of the electron mass. Result: M = 474 keV

  12. Cross-Section Comparison

  13. Sources of Uncertainty • Statistical-Uncertainty on energy ~ 0.15% – 0.3%-Total statistical uncertainty ~ 1% • Systematic-Placement of angle ~ .5o-Huge change in calibration constant ~5% • Final result: M =475 +/ 31 keV

  14. Conclusion • Substantial uncertainty • Known value does lie within uncertainty • Cross sections agree with quantum/ relativistic predictions • Confirms particle properties of light • Should be done in one day to minimize changes in calibration constant

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