60-inch cyclotron, circa 1939, showing a beam of accelerated ions (likely protons or deuterons) escaping the accelerator and ionizing the surrounding air causing a blue glow. This phenomenon of air ionization is analogous to the one responsible for producing the blue flash infamously noted by witnesses of criticality accidents. Though the effect is often mistaken for Cherenkov radiation, this is not the case.

Click this LINK to visit the original image and attribution information. Right click on the image to save the 800px teaching JPEG.



60-inch cyclotron, circa 1939, showing a beam of accelerated ions (likely protons or deuterons) escaping the accelerator and ionizing the surrounding air causing a blue glow. This phenomenon of air ionization is analogous to the one responsible for producing the blue flash infamously noted by witnesses of criticality accidents. Though the effect is often mistaken for Cherenkov radiation, this is not the case.