Joseph Lykken of Fermi National Accelerator Laboratory gave a great talk discussing the many ways we use accelerators today, and from there what we will expect the next generation of accelerators to do. For the non-physicists in the crowd it was a helpful overview and at such an interdisciplinary meeting it never hurts to explain the fundamentals.
The big news in accelerator physics these days is the restart of the Large Hadron Collider at CERN in Geneva (shown above with the underground tunnel illustrated above ground). With a price tag of $10 billion and a time line of 20 years to build, Lykken emphasized the empirical trouble with operating such a machine. As the largest piece of machinery in the world as well as one of the most complicated, the LHC holds twenty seven kilometers of wiring, magnets, cooling systems and advanced technologies. You're bound to run into a few bugs, like those that shut down the machine last September. But the LHC is on schedule to restart this fall when scientists will get to fullfill their ambitions of finding a particle that gives matter mass, uncovering the nature of dark matter, and recreating conditions during the big bang. The science it hopes to produce is truly tantalizing for scientists and science lovers everywhere.
The LHC is the largest and most
powerful accelerator in the world, but the field also expands horizontally into
smaller, yet equally important applications. There are, of course, medical
applications such as proton therapy which treats on the order of 8,000 patients
a year at 25 proton therapy centers in the US. There are even more biological
applications at synchrotron light sources: accelerators that give off X-rays as
they drive particles around a circle. These powerful X-rays are becoming a standard part of protein crystallography, and offer many other biological applications. Soon the first free electron laser will start up at SLAC National
Accelerator Laboratory and offer scientists a chance to watch incredibly
fast processes such as protein folding and molecular motion in real time.
Accelerators may even give aid to the energy crisis and reduce global warming. Accelerator scientists may totally revamp nuclear power by developing a type of accelerator that drives a thorium reactor (rather than uranium or plutonium which are limited resources as well as major safety issues). The waste from these reactors would have a half life of 30 years, instead of thousands. The device would require a linear proton accelerator with particle energies of 10 megawatts, which does not exist yet, but plans are stirring.
Scientist all over the world are contributing to plans for a project called the International Linear Collider, or ILC, a 31 kilometer electron-positron collider that would compliment the LHC. No country has granted space or funding yet, but there are already over 2,000 collaborators from 300 countries working on preliminary plans.
Fermilab, Lykken's home institution, continues to reach for the cutting edge of accelerator science in the US. Fermilab hosts a premier proton therapy center, and is home to the country's most powerful proton-antiproton accelerator, the Tevatron, which will lead the hunt for the Higgs boson until the LHC comes back online. Fermilab has plans to continue leading the field by hosting at least one of two proposed next generation projects. The first, Project X, would be the first superconducting linear collider, the advantages of which are increased stability and lower wall-plug power consumption. There is also buzz for the first muon collider at Fermilab. The lifetime of a muon is less than a microsecond, so the challenge for building such a machine is trifold: create, collect and make a beam out of these particles in less than a microsecond. The collisions would provide new physics to study and save energy and reduce size.
Particle physicists certainly want to push the upper limit of accelerator power, but to go any bigger than the LHC would begin to cost in the hundreds of billions of dollars, which would require some major justification. So the next generation, if they hope to continue to push the energy limits, must eventually reduce in size. This would not only mean big accelerators with even more power, but also making small accelerators smaller; so that, for example, proton therapy devices could it inside an office rather than a football field.
The leader in such technology comes from plasma wakefield accelerators, where particles sit in a plasma (rather than a vacuum) and in one version are accelerated with lasers. One bunch of electrons actually catches a ride on the wake of a bunch in front of it - like a water skier behind a boat. These accelerators could move particles to the same speeds as current technologies, but at 1/1,000th the distance.
"The traditional R&D model for new accelerator technologies has been that the particle physicists...do this R&D and everybody else benefits from [it]," said Lykken. "This model has worked very well in the past; it's still working. But if we really want...to turn around the time from the basic accelerator technology development to something you can use in a hospital, we need to get closer connections between the people doing this kind of research and the people that know what they want to use it for."
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