First light from world's first hard X-ray laser

A couple of days ago, it was published that the the world's first X-ray laser (LCLS) has achieved "first light".

When fine tuning is complete, the LCLS will provide the world's brightest, shortest pulses of laser X-rays for scientific study. As tool for studying the arrangement of atoms in materials, this source will find a wide range of applications in science.

(I love this video, you can really feel the passion of these scientists for their work)

But do you know how it works?

Imagine an accelerated electron bunch which goes through a sinusoidal transverse magnetic field. It will experience a force given by F=q(E+vxB) (Lorentz's force) and thus the trajectory will be sinusoidal too; if the trajectory is a curve, the electrons suffer centripetal acceleration. As it is well known, a charged accelerated particle emits radiation (Lienard-Wiechert). In the Spring-8 website, you can download a program to simulate the radiation emitted by an electron in different magnetic fields.

Due to the electron-radiation interaction, the electrons form electron bunches which emit coherently and the intensity is increased.

These systems are called free electron lasers (FEL); they consist on an accelerator (formed by klystrons which deliver microwave radiation to accelerate the electron and a resonator) and a ondulator (a periodic structure of magnets to produce the sinusoidal transverse magnetic field).

The main problem of these facilities is the size and cost.
Another approach to get X-rays is based on high power lasers: instead of the accelerator, a high-power laser accelerates the electrons which go later through the ondulator. This implementation leads to a reduction of energy and size (in fact, these systems are called Table-Top XFEL).