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 the light so that different frequencies can be generated for different applications. 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 the light so that different frequencies can be generated for different applications. The theory behind undulators was developed by Vitaly Ginzburg in the USSR. However it was Motz and his team who in 1953 installed the first undulator in a linac at Stanford, using it to generate millimetre wave radiation through to visible light. It was not until the 1970s that undulators were installed in electron storage rings to produce synchrotron radiation. The first institutions to take these devices were the Lebedev Physical Institute in Moscow, and the Tomsk Polytechnic University. These installations allowed a fuller characterisation of the behaviour of undulators. Undulators only became practical devices for insertion in synchrotron light sources in 1981, when teams at the Lawrence Berkeley National Laboratory (LBNL), Stanford Synchrotron Radiation Laboratory (SSRL), and at Budker Institute of Nuclear Physics (BINP) in Russia developed permanent magnetic arrays, known as Halbach arrays, which allowed short repeating periods unachievable with either electromagnetic coils or superconducting coils. Despite their similar function, wigglers were used in storage rings for over a decade before they were used to generate synchrotron radiation for beamlines. Wigglers have a damping effect on storage rings, which is the function to which they first put at the Cambridge Electron Accelerator in Massachusetts in 1966. The first wiggler used for generation of synchrotron radiation was a 7 pole wiggler installed in the SSRL in 1979. Since these first insertions the number of undulators and wigglers in synchrotron radiation facilities throughout the world have proliferated and they are one of the driving technologies behind the next generation of light sources, free electron lasers. Insertion devices are traditionally inserted into straight sections of storage rings (hence their name). As the stored particle beam, usually electrons, pass through the ID the alternating magnetic field experienced by the particles causes their trajectory to undergo a transverse oscillation. The acceleration associated with this movement stimulates the emission of synchrotron radiation.