Lancashire and Cumbria

4GLS Background Information

This web page provides further information about the 4GLS Prototype at Daresbury.

It is a companion page for the article in the March issue of LANBRIA, the branch newsletter.

Linac: linear accelerator - a device to impart kinetic energy to charged particles (e.g. electrons). It is 'linear' because the accelerating elements are placed in a straight line not a circle.

Superconducting linac: a linac that has components that exploit superconducting technology.

Superconductor: a material that loses all its electrical resistance below a certain temperature.

Cavity: a hollow, usually cylindrical, metal box pumped with electromagnetic energy (radio waves) in order to accelerate charged particles passing through it. The EM energy unfortunately causes electric currents to flow in the cavity walls which heat up unless they are superconducting.

Synchrotron: a circular particle accelerator with magnets to guide the particles in a circle so they pass an accelerating cavity once per turn.

Synchrotron radiation: all charged particles radiate electromagnetic energy when they accelerate and moving around a curve involves acceleration. Electrons radiate more than protons because they have less mass. The radiation is a broad mix from radio waves through light to UV, X-rays and gamma rays. The upper frequency limit and energy spread of the radiation is fixed by the energy of the charged particles and the strength of the magnetic bending fields.

Wigglers and undulators: types of (multi-pole) magnets which cause a snaking movement of electrons to generate synchrotron radiation without an overall change of electron beam direction.

First Generation Light Source: source of synchrotron radiation ('light') which is primarily a high energy electron accelerator or storage ring/collider. The SR light emerges from the bending (dipole) magnets which guide the electrons in a circle.

Second Generation Light Source: a purpose-built electron storage ring with dipole magnets, wigglers and/or undulators to provide intense synchrotron radiation along many beam lines for research. Darebury Lab's SRS is an example.

Third Generation Light Source: state-of-the-art electron storage ring providing synchrotron radiation, building upon the lessons learned from 2nd generation machines. The DIAMOND project at the Rutherford Appleton Lab, Oxfordshire and the ESRF at Grenoble, France are examples.

Fourth Generation Light Source: a synchrotron radiation light source producing photons in the so-called low energy photon region (infra-red, IR, to the extreme ultra-violet, XUV), exploiting free-electron lasers and superconducting linacs with energy-recovery technology.

Laser: a device that produces intense light of one frequency and with photons all in phase.

Free electron laser: a laser exploiting a beam of accelerated electrons (i.e. not inside materials).

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