Traditional electron detectors for scanning electron microscopes (SEMs) are the Everhart-Thornley detector located on one side of the specimen and the overhead backscattered electron detector (BSED), usually mounted under the final lens. In 2011 PulseTor introduced an efficient BSED based on scintillator/silicon photomultipler technology that is small enough to be mounted on the tip of an X-ray detector. The scintillator converts the electron signal to light, which is in turn converted to an electrical current in the silicon photomultiplier (SiPM). Silicon photomultipliers were initially developed in Russia in the 1990s. The review article by Dolgoshein et al. cites much of the historical development. Following the recent work of Piemonte and others, the SiPM consists of an array of many identical and independent detecting elements (microcells) connected in parallel on a common Si substrate. Each microcell is an avalanche photodiode only tens of micrometers in size.