X-ray Generator Fits In the Palm of Your Hand 32
ananyo writes "Scientists have reported the first tabletop source of ultra-short, laser-like pulses of low energy, or 'soft,' X-rays. The light, capable of probing the structure and dynamics of molecules (abstract), was previously available only at large, billion-dollar national facilities such as synchrotrons or free-electron lasers, where competition for use of the equipment is fierce. The new device, by husband-and-wife team Margaret Murnane and Henry Kapteyn based at JILA in Boulder, Colorado, might soon lie within the grasp of a university laboratory budget — perhaps allowing them to one day be as common in labs as electron microscopes are."
Re:Proteome (Score:4, Informative)
With instruments like this, it will make the task of X-ray crystallography determination of protein structures much easier.
No, it won't. Two reasons:
1) You need "hard" X-rays for crystallography - with a wavelength similar to the chemical bond length. The maximum resolution you can achieve is equivalent to half the wavelength, and even that requires a complicated detector setup, so in practice you want a wavelength around 1 Å for crystallography. The wavelength of this device is 8Å, which is fine for spectroscopy and small-angle scattering studies, but useless for crystallography. While I suspect the technology could be made to work at shorter wavelengths, this usually involves tradeoffs such as higher cost, higher energy consumption, etc.
2) The intensity of the source is far less than a synchrotron (let alone a free-electron laser). This means that data collection times will take far longer. At a synchrotron beamline, in favorable conditions, you can collect an entire data set in seconds (of course, the detector alone costs more than $1 million). Usually it's not quite that fast, but you don't need to wait days for your data - and you can hedge your bets by collecting data on as many crystals as possible.
A secondary reason is that the improvement in synchrotron beamline technology has also made them more accessible - much of the work is now done remotely using robotic sample changers. Being able to grow decent crystals in the first place is a far more limiting factor. And my impression is that beamtime isn't terribly difficult to get; people do still use home X-ray sources while they're waiting for beamtime, but most people are content to wait for the synchrotron to get the truly publishable data.
Excellent work, not FEL competition (Score:5, Informative)
This is a very good experiment, but this is far from being competition for the large X-ray facilities. They are generating 10^5 photons in a 1% bandwidth at 1 KeV. The LCLS (X-ray Free Electron Laser at SLAC) generates about 10^13 photons in a ~0.3% bandwidth. (100 million times more) and operates at 6 X the repetition rate. The LCLS can also operate up to 10 KeV with the same pulse energy if needed. Near future facilities like the Euro XFEL will operate at 100X the average power of LCLS.
The very wide bandwidth of the harmonic generation described in the paper is very interesting because it can in principal support very short (few attosecond) bunches for future experiments, however at the moment they seem to be operating with 80 femtosecond bunches (or bunch trains), comparable to the FELs. (LCLS can run as short as a few femtoseconds with 10^12 photons). It is not clear how to compress their very broad band pulses to generate short pulses, though it is in principal possible. The minimum pulse length for FELs is likely to be around 100-200 attoseconds, so the harmonic generation scheme may eventually have a large advantage here.
It really is excellent work and a low power, ultra-short pulse tabletop X-ray source is a very valuable research tool, but I just want to point out that at the moment it is not a substitute for large X-ray facilities.
Josef Frisch
SLAC / LCLS