Spark Chamber Detector

A spark chamber is a construction of metal plates placed in a sealed box. A high voltage is applied between the plates and since they are close to each other, it creates a big electric field. The plates are placed in a sealed box which is filled with gas. Here, the particles we want to detect, i.e. the muons, are negatively charged.

The basic idea of the detector is simple. The travelling particle will ionise the gas between the plates. Using a triggering system, the high voltage is applied to the plates immediately after the particle went through the chamber. This produces sparks on the exact trajectory of the particle.

The triggering system is made of two scintillators coupled with a photomultiplier tube, one on top of the chamber and the other below it. We are seaching for coincidences between the two scintillators. When a coincidence is observed, a pulse is sent to a spark gap high voltage supply. It triggers a capacitor to discharge itself in the chamber.

Then, the data acquisition system plays its role. Using audio transducers, we can retrieve the trajectory of the particle in the chamber simply by analyzing the travelling times of three sound waves coming from the spark. Since the trajectory is assumed t o be a straight line, we use the data from the top spark and the bottom spark to retrieve the trajectory.

In this particular project, we use aluminum plates and helium gas to fill the chamber.