Construction and Signal Detection Electronics for a Multi-Wire Proportional Chamber

The Society of Physics Students (SPS) at Kennesaw State University is developing a modular multi-wire proportional chamber (MWPC) to detect muons from cosmic rays. The ultimate goal of the project is to deploy an array of chambers for muography, the three-dimensional density mapping of large structures using data from cosmic ray muon absorption. Although the basic technology of MWPCs was developed many years ago, MWPCs are typically large and expensive. A secondary goal of this project is to develop a small, low cost MWPC. These MWPCs are 8” by 8”, and consist of a 3D printed, plastic frame with copper and gold-plated tungsten wires sandwiched between two copper plates. The copper plates are at ground potential, and there is a potential difference of 2,000V between the two types of wire. Muons pass through the chamber and ionize the gas inside, which starts an avalanche of electrons. This causes a current in one of the wires and sends a signal to the data collection equipment. A new phase of testing is about to begin, using “practice signals” from alpha and beta sources. These sources will establish that the chambers are functional, and since they have a known decay rate, they will provide data to determine the chambers’ efficiency.