Modular Multiwire Proportional Chambers: Design, Testing, and Simulation

The Society of Physics Students (SPS) at Kennesaw State University is building a series of multiwire proportional chambers as a tool to detect cosmic ray muons with the goal of doing muography on large structures. The chamber consists of two cathode plates that enclose an array of wires under high voltage and is filled with an ArCO2 mixture. High energy muons that pass through the chamber will trigger an electron avalanche that induces a current in the anode wires. Paschen theory was considered to determine wire spacing and operating voltage. In the avalanche formation region the electric field strength exceeds 3 million volts per meter. The chambers must be modular, inexpensive, and efficient. These requirements impact the design and need creative solutions. The chambers are 8 inches square, utilize 3D printed frame material, and can connect to each other. The chambers must be able to hold up to 2.5kV of stable voltage and transmit a clean signal to detection circuits. Simulations of the electric field were created using ComSol to visualize the avalanche region and electric field over the chamber. Geant is also being employed to run simulations of various particles through our geometry including alpha and beta guns and cosmic ray muon flux.