Spinning Wheel of Solar Energetic Protons

The CRaTER (Cosmic Ray Telescope for the Effects of Radiation) instrument is a radiation instrument on the Lunar Reconnaissance Orbiter (LRO) that will orbit the Moon. The instrument will measure the amount of energy deposited into a plastic that simulates living tissue. This will be used to calculate the radiation dose that an astronaut might get when exposed on the surface of the moon. To test the instrument using, the proton beam at Proton Radiation Therapy Facility of Massachusetts General Hospital was passed through a spinning wheel. The wheel was constructed to modify the energy of the beam and produce a spectrum very much like what might be seen during a solar flare event.