The final curtain; and, it's curtains for fish eggs
Saturday, October 18, 2008
Last day of the LCLS/SSRL users' conference, with a series of joint workshops on using soft X-rays. This was the best attended set of workshops, I believe. Especially for a Saturday.
I blogged about beamline 13 yesterday, with a link to a more detailed article on it's instrumentation. Basically it's now the dedicated soft X-ray beamline at SSRL, with one instrument (13.3) serving as a test bed for a technique to be used at the LCLS—high resolution imaging of microscopic samples, using coherent X-rays. Part of the problem with using X-rays for imaging is focusing. Traditional lenses don't work because X-rays are so penetrating they go straight through most materials and can't be made to bend easily. (Although special Fresnel lenses called "zone plates" work for certain applications.) Andreas Scherz and colleagues are now working on "lensless" imaging techniques that have a lot in common with holography. Henry Chapman (DESY, Hamburg) gave a talk on imaging biomolecules that I found most interesting. A major concern with imaging biomolecules (such as proteins or viruses) is getting them into a beam of X-rays. The preferred route is to stream them one by one (if possible) in a vacuum, so that there is nothing extra for the X-rays to interact with and cause noise in the image. The cool part to me is the technology behind making jets of biomolecules. Apparently this is not something that's been done to much extent, and an entirely new technology is developing around how to inject objects of that tiny size in a regular stream. Even more difficult to imagine, a few groups are looking at how to make jets of *living* cells… in a recent conversation with Janos Hajdu, he told me about researchers who successfully fired a stream of living zebra fish embryos at incredible velocities, in the hundreds of meters per second, and then caught them, all without damaging them. The embryos went on to hatch normally. Advances in sample delivery technologies is good news for biologists, clearing the way for studies of living structures at super high resolution. The LCLS beam, however, will vaporize any sample instantaneously. The technical hurdle of capturing enough information about a sample in that sliver of time before it vaporizes has been solved for longer wavelengths of X-rays, which bodes well for honing the technique using the hard X-rays of the LCLS. (Even if we do procure a fish-safe fish gun, I don't think SLAC should worry about building a hatchery.) posted by Brad Plummer @ 2:00pm
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