Muon and Geiger counter (old TTL style)

[madexp]

This project was born out of the need to create something practical and engaging to showcase during the Open Day at the ISISS Piero Gobetti Institute in Morciano, where I teach.



The focus of the project is a detector specifically designed to count cosmic rays, particularly muons. Muons are elementary particles, similar to electrons but about 200 times heavier. They are a component of cosmic rays, which originate from outer space and are mostly high-energy particles produced by the sun, distant stars, and supernovae. When these particles interact with the Earth's atmosphere, they create showers of secondary particles, including muons, which are highly penetrative and can reach the ground.

The detector prototype consists of the following components:

   

• Two stacked Geiger tubes (model SI22G): These are sensitive to gamma rays and are excellent for reducing background noise, isolating the signal produced by muons more effectively.
• A high-voltage converter circuit: This circuit boosts a 5V input voltage to 400V, providing the necessary power to the Geiger tubes.
• A logic network: This processes input pulses from the two Geiger tubes, shaping and widening the signals. It also performs a temporal coincidence check to ensure that the detections are simultaneous, which is crucial for distinguishing muons from random background events.
• A selector switch: This allows the user to choose between two modes:

      > Geiger counter mode: Counts all detected events, useful for general radiation detection.
      > Muon counter mode: Operates in coincidence mode, only counting events detected simultaneously by both tubes, characteristic of muons passing through.

• A counter and display unit: Based on the classic combination of a 74LS47 decoder/driver and a 74LS90 counter IC, this unit increments counts and displays the result on a seven-segment display.

The prototype is mounted on a cherry-colored varnished plywood base. To ensure a neat and functional design, I also created several custom supports using a 3D printer and PETG filament.

The following photos provide a visual representation of the prototype and its assembly, illustrating the design and functionality better than words can describe.

This device is not only a practical tool for demonstrating the detection of cosmic rays but also serves as an engaging educational model for students to understand advanced physics concepts such as particle physics and cosmic ray interactions.

All the following traces are in complemented logic (0 is logic true).
Yellow trace: coincidence output
Purple: Geiger mode OR output
Green: Geiger-1 pulse
Blue: Geiger-2 pulse

These two pictures are pulses from the two tubes:





This one is the output with pulse coincidence: