Nuclear Radiation Sensor Measures Radioactivity Without Need of a Geiger Tube

While there are many ways to measure radiation levels, most methods in the hobbyist arena are Geiger–Müller based. One alternative is the use of semiconductors to sense interactions between ionizing radiation and the p-n junction. A project posted by Robert Gawron explores the possibilities for semiconductor-based sensors in the DIY space.

The sensor’s output functions more or less like a Geiger counter: the higher the radioactivity is, the more pulses produced in the device’s output. It is constructed using three photodiodes in parallel, polarized using four 12V batteries. The first stage of amplification consists of a transimpedance amplifier, followed by an inverting amplifier. The circuit diagramis available in the post. There are two possible outputs for the device: analog or digital. With an analog output, an oscilloscope can be connected, while the digital output, with a logic level of 12V, can be collected and analyzed after it is produced.

All hardware for the project was designed using Kicad, and data is stored using NUCLEO-F091RC with a small breadboard attached. This makes it possible to watch the results in real-time via a small LCD, as well as collecting it for further analysis. More on the data logging project can be found here. A simple script to plot the results was created using R and creates a graph of change in counts per minute over time and a histogram of counts vs. percentage.

Gawron's finished device is not usable without proper shielding from EMI light, and its chassis must be both made of metal and grounded. It is recommended that you drill a small hole where the photodiodes are located and cover that with tin foil to allow for easier penetration of radioactivity. Many aspects of the design are flexible to the user, and hardware and software files for the project are available on GitHub.