Cosmic Rays

Equipment

Stage, camera holder, Minipix-EDU

Procedure

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: 1800
   5. Exposure: 1 s
   6. Sum: check
   7. Color Map: Hot
2. Mount the MiniPix EDU camera on the stage and click on the play button.
   NOTE: Make sure that View -> Rotate Image is set to zero.
3. Cosmic rays are always present around us and thus we do not need the radiation source.
4. Repeat the same scan with the camera placed flat on the table, as shown in figure 1. For this purpose, the camera has to be taken off the stage.
   
   Figure 1. The detector laid flat on the table to collect radiation in a different orientation

Results

1. We observe the usual beta and gamma radiation. The alpha blob coming up in figure 3 should not be related to the orientation of the camera. We may observe alpha particles in any orientation.
2. Other than these three particles, when the camera is vertical, we observe some long straight streaks of muons in figure 2.
3. Although, by laying the camera flat on the table, the muons suddenly disappears (Fig. 3)
   
   
   Figure 2. The long streak of muons from cosmic showers when the camera sensor is vertical
   
   
   
   Figure 3. Hardly any muon shows up when the camera is laid flat on the table. We observe the alpha blob from the background radiations.
   
   
4. The number of these tracks in case of vertical position is much higher than the one in a horizontal position.

Conclusion

1. These long streaks can only be created by highly penetrating particles moving in the plane of the sensor.
2. Since the thickness of the sensor is only 300 µm, it can be concluded that the particle is not coming from a nearby source.
3. Most of the streaks are at a range of 45 degrees to 90 degrees of angle with the horizontal plane. So most probably, these particles are coming from right above our head. These can be muons from the secondary shower of cosmic rays.
4. These muons are usually generated at a height of approximately 10 km above the earth’s surface and move at almost the speed of light but have a very short life span.