Particle Beam Collimation of Alpha Particles
Stage, camera holder, source holder, collimator, polonium-210, Minipix-EDU
- Launch the Pixet Basic software and modify settings to the following:
- Min Level: 0
- Max Level: 50
- Measurement Mode: Tracking
- Frames: 100
- Exposure: 1 s
- Sum: check
- Color Map: Hot
- Mount the MiniPix EDU camera and polonium on the Stage. Make sure to put polonium in the rear slot and then insert the collimator.
- Keep the camera and the source at a distance of 2.5 cm and click on the play button.
- We observe a circular image of concentrated alpha particles (Fig. 1).
Figure 1. The collimated beam of alpha particles from polonium-210
- We can determine the diameter of the circle hovering the cursor to the two extreme opposite ends of the circle. Making sure the y-coordinate for the two points are the same, subtract the x- coordinate of one point from another as shown in figure 2(a) and 2(b).
221- 98 = 123 pixels
a) x-coordinate of the left corner b) x-coordinate of the right corner
Figure 2. Hovering the cursor to measure the diameter
- The difference gives us the number of pixels and since each pixel is 55 µm x 55 µm, the diameter will be
123 x 55 = 6765 µm = 6.76 mm
- The diameter of the collimator is 6 mm and that of the observed circle of alpha particles is 6.76 mm. The error is ~12.7% which is quite low and it can be reduced if we further decrease the distance between the collimator and camera.
- The data collected with the minimum distance resulted in only 1.7% of error.
Caution: It is not advisable to perform the scan at less than 2.5 cm distance because there is a high risk of hitting the collimator into the camera sensor.
- The observed circle of alpha particles is proof of the linear propagation of particles.
- Also, the increase in diameter is proof of the linear divergent beam of alpha particles.