Texas Physicists Create Tabletop Particle Accelerator 89
An anonymous reader sends this quote from a University of Texas news release:
"Physicists at The University of Texas at Austin have built a tabletop particle accelerator that can generate energies and speeds previously reached only by major facilities that are hundreds of meters long and cost hundreds of millions of dollars to build (abstract). 'We have accelerated about half a billion electrons to 2 gigaelectronvolts over a distance of about 1 inch,' said Mike Downer, professor of physics in the College of Natural Sciences. 'Until now that degree of energy and focus has required a conventional accelerator that stretches more than the length of two football fields. It’s a downsizing of a factor of approximately 10,000.' ... Downer said that the electrons from the current 2 GeV accelerator can be converted into “hard” X-rays as bright as those from large-scale facilities. He believes that with further refinement they could even drive an X-ray free electron laser, the brightest X-ray source currently available to science. A tabletop X-ray laser would be transformative for chemists and biologists, who could use the bright X-rays to study the molecular basis of matter and life with atomic precision, and femtosecond time resolution, without traveling to a large national facility."
Size is deceptive... (Score:5, Informative)
Area needed for experimental appratus: One 6' folding table from Office Depot
Equipment needed: One petawatt-class laser, occupying a large portion of the physics building
Not new (Score:5, Informative)
However, accelerating a LARGE number of electrons is complicated. Accelerating a large number of ions is even more so. That's why LHC is necessary - you can't hope get enough luminosity with small tools, even if you can reach the same energies.
Re:Size is deceptive... (Score:5, Informative)
Looking into it:
The petawatt laser is installed on a 10m long optics table, and is controlled by 1 19" server rack. Granted, that's a Big Freakin Laser (tm), but hardly half the physics building, and I'm not sure, but if I understand their explanations correctly making the accelerator longer needn't necessarily require higher power from the laser. Besides, this is the engineering phase, we'll see in 10 years or so if it's actually useful and interesting from a useful science perspective. As it stands, there are facilities that can produce X-rays at these power levels, this system just seems to be designed to put one in every major college campus, rather than having 2 or 3 in the nation.
Re:Wow... (Score:5, Informative)
Some details missing... (Score:5, Informative)
The press release makes some very grand-sounding claims about replacing synchrotrons and free-electron lasers. I'm not an expert in the accelerator field but I've used these systems, and I have some idea of what the actual output needs to be in order to be useful for biologists. Specifically, it's not just the electron energies that matter, but the photon flux per unit of area. The figures for modern synchrotrons are on the order of 10^11 - 10^13 with a spot size of 100 microns or less - the very best will focus down to just a few microns. From what I can understand of the paper, they're talking about several orders of magnitude fewer photons over much larger areas. (If someone who understands this stuff better can confirm whether or not I'm reading it correctly, I'd be grateful.) The only hard free-electron laser in the US, the LCLS at Stanford, is orders of magnitude brighter than synchrotrons, and compressed into pulses on the order of tens of femtoseconds long.
It would be great if someone could build a high-intensity hard X-ray source at every big research university. But it's not the first time such claims have been made; there is (or was) a company called Lyncean that tried to build a tabletop synchrotron in the previous decade, and made similar predictions about its utility for biology. Their technology worked perfectly well from a theoretical standpoint - but it was several orders of magnitude too weak to be competitive with existing synchrotron beamlines, and too expensive to be competitive with existing laboratory X-ray sources.
(Of course this is pretty much standard stuff from university PR departments, which would always like you to believe that they're on the brink of curing caner or revolutionizing some widely used method. The actual Nature Communications article is much more sober.)
Re:Size is deceptive... (Score:5, Informative)
I graduated from UT with a PhD in physics, and Mike Downer was a prof while I was there. He does "femtosecond physics" ie things you can do with extremely short pulses of laser light. Pretty cool stuf, actually. Anyway, a petawatt laser (10^15 W) fired in a femtosecond (10^-15 s) has a total energy of ~1 J per pulse...they're really not giant gizmos.
Message: the lasers in question aren't petawatt CW, but pulsed.