Dr. Tsubokura's Radiation Lecture Vol.73
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
145. Detecting the number of electrons emitted from collisions against radiation rays
The extent of radiation exposure determines its impact on health. There are various measuring devices to detect levels of radiation and radioactivity.
Radiation rays have a feature of colliding against substances in their way and forcing those materials to emit electrons. When radiation rays pass through a measuring device filled with stable gas, they collide against the substances composing the gas, and electrons are emitted from those substances. Measuring devices that detect the amounts of emitted electrons are called Geiger counters.
Another measuring device is called a "semiconductor detector" (the common type being a Germanium-based semiconductor detector), which utilizes materials called "semiconductors" instead of gas. While materials that allow the flow of electric current (e.g., iron and copper) are called "conductors," materials that do not transmit electricity (e.g., rubber and glass) are called "insulators." A semiconductor lies between a conductor and an insulator; in other words, it transmits electricity to some degrees. A cooled germanium semiconductor detector can conduct electricity only when stimuli are added. Therefore, it can conduct electricity when electrons are emitted after radiation rays c