For my final engineering project at Swarthmore College, I designed and simulated gamma ray detector for CubeSat applications. Based on work I did at NASA Goddard Space Flight Center over the past two years, I developed a simple phoswitch detector for shoebox sized spacecraft.
The final presentation I did on the project is on YouTube, but I've summarized some of it below.
Design
My detector studies high energy photons, like X-rays but even higher energy. Gamma rays don't interact with materials like the film used in a dental X-ray, so gamma ray detectors measure the light produced indirectly as gamma rays go through blocks of specially chosen clear materials. In my phoswitch design, a block of plastic a block of crystal sit on top of silicon photomultipliers, a chip that detects individual visible light photons produced in the blocks.
In the image below, the grid of squares on the left with dots in the middle are silicon photomultipliers, and the clear block on the right is plastic wrapped in plumbing tape. The circuit board amplifies and shapes the signals so they can be recorded by an oscilloscope.
Simulation
Since I couldn't do normal lab testing this spring to prove my design, I turned to MEGAlib, a gamma ray simulation library built on the famous particle physics simulator GEANT4. The code referenced below generates a huge numbers of gamma rays to pass through the detector and measures the energy left in the detector. The distribution of those energies is in the histogram below and a reconstruction of those gamma rays is shown in the cover photo.
Challenges
With my engineering background, rather than physics, I could not have done these particle physics simulations without being able to collaborate quickly and consistently with my mentors and troubleshoot with the MEGAlib project. While I'm sad that laboratory testing wasn't possible this semester, I'm still hopeful that this project will be fully implemented eventually and my simulation work will provide a springboard for that future work.
Code
A simple functional setup for MEGAlib.
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