A laser wakefield accelerator is a kind of plasma accelerator that uses a high energy laser to stimulate an electron wave in the plasma. These accelerators can be used to produce high speed particles and radiation and are very size efficient for their task but the X-Rays produced are themselves very disorganised and lack any form of coherence. To overcome this problem the idea is to use magnetic and plasma undulators to create these X-Rays at specific tunable frequencies.
An undulator is two rows of magnets alternating their polar directions and always opposite a complementary magnet. This creates a stationary magnetic field that undulates like a wave along the device. Any charged particle, like all parts of the plasma, entering it are forced to accelerate up and down as they pass through the tunnel. An accelerating charge always radiates and that is exactly what the plasma does producing electromagnetic radiation with a frequency related to the acceleration. Using this method it has been shown that the radiation given out is controllable by changing features such as the plasma makeup, the amplitude of acceleration, the laser intensity and polarising filters on the device. The advances in this field will hopefully be able to produce greater quality, greater intensity lasers but in reduced spaces in the future.