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1. Compton Scattering

The scattering of high-energy photons by electrons. High-energy (662 keV) photons in a collimated beam from a radioactive 137 Cs source are scattered from electrons in a target which is itself a scintillation counter which detects the recoil electron. The scattered photons are detected in a second scintillation counter. The distribution in size of pulses from either the target or the scatter counter are recorded by a multichannel analyzer gated by pulses from a coincidence circuit activated by coincident pulses from the two detectors. In the first part of the experiment both scintillators are NaI crystals, and the energies of the scattered photons and the recoil electrons are measured as functions of the scattering angle; the results are compared with the theory of Compton scattering.

In the second part the target is a plastic scintillator, and the relative intensities of scattered photons are recorded at several scattering angles. The results, normalized to a separate measurement of the total scattering cross section of the plastic scintillator, are used to derive the differential scattering cross section; the results are compared withf the Thomson and the Klein-Nishina formulas for the scattering of photons by free electrons.

Student Wiki: Compton Scattering

Download Lab Guide in PDF format

References (certificates required)

  1. 1927 Nobel Prize to A.H. Compton for his Discoveries and Research in the Field of X-Ray Spectroscopy
  2. A.H. Compton, Phys. Rev., 21, 715 (1923).
  3. A.H. Compton, "The Spectrum of Scattered X-Rays," Phys. Rev., 22, 409-413, (1923).
  4. A.H. Compton, "A Quantum Theory of the Scattering of X-Rays by Light Elements," Phys. Rev., 21, 483-502, (1922).
  5. R. Hofstadter and J.A. McIntyre, "Measurement of Gamma-Ray Energies with Two Crystals in Coincidence," Phys. Rev., 78, 619-620 (1950).
  6. N.H. Lazar, R.C. Davis, and P.R. Bell, "Peak Effeciency of NaI," Nucleonics, 14, 52 (April 1956).
  7. A.C. Melissinos, Experiments in Modern Physics, (Academic Press, San Diego, 1966), "Compton Scattering," 253-265.
  8. R.P. Garner and K. Verghese, "On the Solid Angle Subtended by a Circular Disc," Nucl. Instrum. Methods, 93, 163-167 (1971).
  9. J. Higbie, "Undergraduate Relativity Experiment," Am. J. of Phys., 42, 642-644 (1974).
  10. G.F. Knoll, Radiation Detection and Measurement (John Wiley, New York, 2000), "Optimization of Counting Experiments," pp.92-95
  11. G.F. Knoll, Radiation Detection and Measurement (John Wiley, New York, 2000), "Radiation Spectroscopy with Scintillators," pp.306-355

Selected Resources

  1. Canberra 2000 NIM Bin and Power Supply
  2. Canberra 802 Scintillation Detector [Na(Ti) Detectors]
  3. Canberra 805 Scintillation Detector Preamplifier
  4. Canberra 3002 HV Power Supply (3002D is a newer digital version)
  5. Canberra 2126 Constant Fraction Discriminator
  6. Ortec 533 Dual Sum and Invert Amplifier
  7. Ortec 418A Universal Coincidence

 

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