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Alpha Spec


High Energy Physics

Alpha Particle Spectroscopy

Objectives of the Project

  • Determine the range in air, and other gases, of alpha particles from an Am241 source.
  • Measure the Bragg ionisation curve.


Experimental Procedure

  1. Study the properties of the solid state detector. How does it work?
  2. Use the alpha spectrum from the standard Pu/Am/Cm source in a vacuum to calibrate the scale of the MCA in keV.
  3. Plot the counting rate of the detector at atmospheric pressure as a function of source – detector separation and at constant separations as a function of pressure.
  4. Measure the Bragg curve using the Multi-Channel Analyser (MCA) to obtain the particle energy.

Safety and Precautions

Remember that Am241 is both an alpha and a gamma emitter.
The technician will insert the source in the apparatus. Subsequently, DO NOT OPEN the vacuum box without prior consultation with the laboratory supervisor.

Do not touch the front face of the detector.

  • Siegbahn, K.: Alpha, Beta and Gamma Spectroscopy.
  • Knoll, G.F.: Radiation Detection and Measurement.
  • Leo, W.R.: Techniques for Nuclear and Particle Physics Experiments
  • Useful statistics

External links