Different type of Energy Spectrum of Alpha Particles


Stage, camera holder, source holder, bath tissue (Brady ultra softone), plastic film (Saran wrap), polonium-210, Minipix-EDU


  1. Launch the Pixet Basic software and modify settings to the following:
    1. Min Level: 0
    2. Max Level: 100
    3. Measurement Mode: Tracking
    4. Frames: 100
    5. Exposure: 1 s
    6. Sum: uncheck
    7. Color Map: Hot
  2. Mount the MiniPix EDU camera and polonium on the stage.
  3. Keep the source and camera as close as possible with the tissue between them and click on the play button, as shown in figure 1.

    Figure 1. Setup of polonium and camera with tissue paper blocking the path of radiation.

  4. Repeat the same experiment with a layer of plastic film in place of tissue.


  1. The peak that we observe in the case of food wrapping foil is at ~2200 keV and the spectrum looks similar to the one when nothing is blocking the path of alpha particles (Fig. 2).

    Figure 2. The energy peak of alpha particles being observed at ~2200 keV when the plastic film is blocking the way of alpha particles

  2. But the spectrum of tissue looks very different and we observe a wide range of energies from 0 keV to 3500 keV, instead of a sharp peak (Fig 3).

    Figure 3. A scattered pattern of energy being observed when the path of alpha particles is blocked by a tissue paper


  1. The experiment explains the effect of the non-uniform density of blocking material on the flow of alpha particles. 
  2. The foil has an equal distribution of density all around and thus we observe the usual peak with lower energy (some of the energy is being absorbed by the film).
  3. But in the case of the bath tissue, the probable variation in thickness and its varying porosity at different points results in uneven absorption of energy. Thus, many alpha particles are being stopped and some easily pass through the holes, resulting in the widening of the energy peak.

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