Bun (hairstyle) Bun (hairstyle) A bun is a type of hairstyle wherein the hair is pulled back from the face, twisted or plaited, and wrapped in a circular coil around itself, typically on top or back of the head or just above the neck. A bun can be secured with a hair tie, barrette, bobby pins, one or more hair sticks, a hairnet, or a pen or pencil. Hair may also be wrapped around a piece called a "rat". Alternatively, hair bun inserts, or sometimes rolled up socks, may also be used to create donut-shaped buns. Buns may be tightly gathered, or
Insertion device Insertion device An insertion device (ID) is a component in modern synchrotron light sources, so called because they are "inserted" into accelerator tracks. They are periodic magnetic structures that stimulate highly brilliant, forward-directed synchrotron radiation emission by forcing a stored charged particle beam to perform wiggles, or undulations, as they pass through the device. This motion is caused by the Lorentz force, and it is from this oscillatory motion that we get the names for the two classes of device, which are known as wigglers and undulators. As well as creating a brighter light, some insertion devices enable tuning of