Physics Department

Terrestrial Gamma-ray flashes (TGFs) are energetic flashes of gamma-rays produced by lightning in thunderstorms. The levels of radioactivity and effects that TGFs have on people and aircraft in close proximity to lightning are still unknown. Current TGF detectors have proven to paralyze and oversaturate when in close proximity to bright TGFs. Because of this, the Intense Radiation Integration Sensor (IRIS) was developed to detect TGFs at close range without saturation, using two photodiodes (bare and with scintillator attached) to detect incoming relativistic Compton electrons from the bremsstrahlung TGF gamma-rays. IRIS was developed at the Santa Cruz Institute of Particle Physics (SCIPP) in Santa Cruz, California and field tested using a Mobetron electron-beam accelerator at the MD Anderson Cancer Center in Houston, Texas. Field testing showed IRIS’s sensitivity levels to be higher than we ultimately wanted, warranting next steps in IRIS development to use four bare photodiodes with widely spaced sensistivity levels. Long term IRIS goals include mass production of these dosimeters and distribution to people and aircraft in high lightning areas, using citizen science to help advance the understanding of the radioactivity of TGFs.