Dutch researchers build affordable alternative to mega-laser X-FEL

Dutch researchers build affordable alternative to mega-laser X-FEL: The essence of their 'poor man's X-FEL' is that it uses electrons instead of X-rays. "Why convert electrons into X-rays if you can use the electrons themselves?", asks Van Oudheusden. "As well as that you only need to give the electrons a low energy, so you can accelerate them in just a centimeter. That's why the whole system fits on a tabletop."

The physical barrier that Van Oudheusden had to overcome is that the electrons in electron bunches repel each other. This causes the electron bunches to expand, making them longer than the desired 100 femtoseconds (1 femtosecond is 10-15 second), which in turn would make the 'video microscope' too slow. Jom Luiten thought of a solution to prevent the undesired expansion. The key was to create bunches of exactly the right shape, so they can be controlled and focused by means of electrical fields into bunches of the desired type and length. All with a number of electrons (1 million) that is sufficient to create a diffraction pattern in just a single shot.