Construction of a Multi-Wire Proportional Chamber for Muon Detection

The Society of Physics Students (SPS) at Kennesaw State University is building a series of Multi-Wire Proportional Chambers as a tool to detect cosmic ray muons with the goal of doing muon tomography on large structures.

Chamber construction is done using a 3-D printer. The chambers are required to be sealed and hold an ionizing gas, which in our case is an Argon/CO2 mix in an 80:20 ratio. The design of the prototype chamber was reworked such that the entire frame could be made in a single 3-D print operation, rather than as a series of printed pieces which needed to be sealed together. This modification allowed the chambers to hold the gas mixture properly without leaking. The geometry of the 3-D printing was done using SolidWorks, and the printing was done using a Makerbot Ultimaker 2 with PLA, a biodegradable, plant-based plastic.

Once the frames were printed, both the sense wires and field-shaping wires needed to be attached and soldered under tension, with spacing between wires of 3 mm. Since the wires are extremely fine, (the sense wires are gold-plated tungsten with a diameter of 25 microns) the process of attaching them is not trivial, so grooves were added to the printed frame design to aid in the alignment of the wires.