How do you build a research-grade radiation detector on a budget? This Immersion demonstrates a complete signal chain—from the physical interaction of radiation with matter to the digital processing of data—using a solder-free, breadboard-based approach.

In this session, we will explore different scintillating materials, including BGO (Bismuth Germinate) and CsI(Tl). BGO is particularly advantageous for the teaching lab because it is non-hygroscopic, requiring no special sealing or humidity control, and its high density provides excellent stopping power for gamma rays.

These crystals are coupled with Silicon Photomultipliers (SiPM), which operate at low voltages (typically <30V), making them much safer and more convenient for students than traditional high-voltage PMTs. A major focus of this session is the Analog Front-End: you will learn to build and tune your own amplifier and comparator circuits using standard operational amplifiers (op-amps). This "white-box" approach ensures students understand exactly how a tiny pulse from a detector is conditioned into a signal a microcontroller can read.

The heart of the digital system is the Raspberry Pi Pico. We will use its high-speed ADC to digitize pulses, allowing us to perform gamma spectroscopy and identify isotopes without the need for expensive commercial multi-channel analyzers (MCAs).

Key Learning Outcomes

• Scintillator Physics: Compare materials like BGO (non-hygroscopic, high density) vs. CsI(Tl) (high light yield).
• Analog Electronics: Design and assemble op-amp-based amplifiers and comparators on a breadboard to shape SiPM pulses.
• Microcontroller Integration: Interface your custom analog circuit with the Raspberry Pi Pico to digitize waveforms.
• Firmware Development: Utilize the pico firmware (github.com/jintonic/pico) to trigger detections, blink LEDs, and drive OLED status displays.
• Gamma Spectroscopy: Analyze pulse-height distributions to create energy spectra and identify unknown radioactive sources.

Curriculum Schedule

Day	Morning Session	Afternoon Session
Day 1	Physics of BGO/CsI(Tl) & SiPMs	Breadboard assembly: Op-amp Amplifiers
Day 2	Building the Comparator & Pico setup	Signal debugging with Oscilloscopes
Day 3	Data Analysis: Energy Calibration	Identifying unknown isotopes

Synergy with Geant4

Note: This Immersion is designed to complement the "Geant4 Simulation of Radiation Detection" Immersion. While Geant4 allows you to simulate the "ideal" response of a detector, this session gives you the hands-on reality of building the hardware and dealing with real-world noise and signal conditioning.

Host and Mentor:

Dr. Jing Liu is a Professor at the University of South Dakota with 20 years of experience in experimental particle physics. He is a strong advocate for "hackable" lab equipment that pulls back the curtain on how detectors work. Through his pico project and his popular YouTube tutorials, he provides open-source tools that empower physics departments to implement advanced nuclear labs at a fraction of the traditional cost.

Please note that the Jonathan F. Reichert Foundation has established a grant program to help purchase apparatus used in Laboratory Immersions. Limitations and exclusions apply, but generally speaking the Foundation may support up to 50% of the cost of the required equipment.