Week 9 Blog

Hi everybody!

Welcome to week 9 of my senior project. This week, I talk about radiation spectrum peaks and progress on my project.

Nuclear Physics Weekly

Last week, we covered analyzing gaussian peaks to obtain counts at certain energies. Today, since I’m running code on real sensors now, I wanted to cover some common peaks to look out for in gamma spectra.

Let’s go through a few of the most frequently observed gamma energies and the isotopes that emit them:

1. 1460 keV — Potassium-40

Potassium-40 is a naturally occurring isotope found in soil, bananas, and even the human body. It’s part of the natural background radiation. Its 1460 keV peak is a giveaway—it’s high in energy, relatively isolated, and almost always present if you’re measuring ambient background. Since it’s so prominent and reliable, it’s also typically used to calibrate sensors.

2. 609 keV, 1120 keV, and 1764 keV — Bismuth-214 (²¹⁴Bi)

These peaks often show up together and point to one thing: the uranium-238 decay chain, which usually points to the existence of uranium and/or radon in the environment. Bi-214 is a short-lived daughter product that emits multiple gamma rays. These energies—609, 1120, and 1764 keV—are some of the most intense and are commonly used to track environmental uranium and radon levels.

5. 295 keV and 352 keV — Lead-214 (²¹⁴Pb)

Also part of the U-238 chain, these lower-energy peaks come from Pb-214. When seen alongside the Bi-214 peaks mentioned above, they support the presence of a uranium decay series. These are especially helpful in confirming radon presence when analyzing indoor air or building materials.

6. 511 keV — Positron Annihilation

This peak doesn’t come from a specific isotope, but rather from a process. When a positron (the antimatter counterpart of an electron) encounters an electron, they annihilate and produce two 511 keV gamma rays emitted in opposite directions. This can happen in isotopes that decay by beta-plus (positron) emission, such as Fluorine-18 or Sodium-22. So if you see a distinct peak at 511keV, you probably have a positron emitter.

Project Progress

As I near the end of the project, this week was mainly focused on testing with a real sensor and working on my presentation. Luckily, the sensor outputted usable data, and I’ll keep testing and refining next week.

See you all next week!