Scientists build 'Poor Man's Free Electron Laser'
If you want to obtain moving images of high-speed molecular processes at an atomic scale, one of the best facilities in the world is the X-ray Free Electron Laser (X-FEL) at Stanford University. Should you wish to use it, however, you’ll have get on a waiting list, then bring your materials to its California home once it’s your turn. If you’re thinking of building your own, you’d better start saving now – Stanford’s laser reportedly cost several hundred million dollars to build, and the cost of a new European X-FEL has been set at one billion euro (US$1.3 billion). Researchers from the Netherlands’ Eindhoven University of Technology (TU/e), however, have recently announced the development of a tabletop “poor man’s X-FEL.” It performs some of the same key functions as the big laser, but costs under half a million euro (US$656,006).
Instead of visible light, free electron lasers emit ultra-short X-ray pulses, to create a series of extremely short exposures. These pulses are generated by speeding electrons through an accelerator that’s at least one kilometer (0.6 miles) in length, then converting them to X-rays. Not only is such a facility extremely expensive to create, but it also consumes a lot of power, and requires a team to operate.
The big difference with the poor man’s X-FEL is the fact that it doesn’t convert the electrons to X-rays. “Why convert electrons into X-rays if you can use the electrons themselves?” asked the system’s creator, doctoral candidate Thijs 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.”
Electrons repel one another when placed in a bunch, causing that bunch to expand to the point of making the TU/e system too slow. To get around that problem, van Oudheusden’s advisor Dr. Jom Luiten created electron bunches that were of such a shape that they could be controlled and focused by electrical fields. This allowed the bunches to be of a type and length that they could be used to create moving video footage of microscopic molecular processes.