The term “shutter” implies the deliberate introduction of material between the radiation source and an object to reduce the radiation intensity and, hence, damage to the object. However, attenuation and absorption of radiation are also important in radiotherapy and radiation processing, where the aim is to deliver a precise amount of radiation “dose” to a tumor or sample. It is easy to shield ion and electron sources; almost any material thicker may be used to stop all ions. Electrons are easily stopped by a few millimeters of any solid material.