When cosmic rays hit the top of Earth’s atmosphere, they create a spray of secondary radiation that penetrates airplanes and even reaches the ground below. For years, the students of Earth to Sky Calculus have been measuring secondary cosmic rays on airplanes and high-altitude balloons using two types of sensors.
First are the neutron bubble chambers:
Each bubble pictured above is formed by an energetic neutron (200 keV – 15 MeV) passing through the chamber. Counting bubbles yields the total dose.
Second, we monitor X-rays and gamma rays using sensors based on Geiger tubes:
Cosmic rays at aviation altitudes are a cocktail of different things: e.g., neutrons, protons, pions, electrons, X-rays, and gamma rays spanning a wide range of energies. Our sensors sample only three ingredients of that cocktail (neutrons, X-rays, gamma-rays) at relatively low energies typical of medical X-rays and airport security devices. This means our data are only the tip of the iceberg. Flight crews and passengers absorb even more radiation than we can detect.