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 theworld as well as one of the most complicated, the LHC holds twenty sevenkilometers of wiring, magnets, cooling systems and advanced technologies. You’rebound to run into a few bugs, like those that shut down the machine lastSeptember. But the LHC is on schedule torestart this fall when scientists will get to fullfill their ambitions offinding a particle that gives matter mass, uncovering the nature of darkmatter, and recreating conditions during the big bang. The science it hopes toproduce is truly tantalizing for scientists and science lovers everywhere.
The LHC is the largest and mostpowerful accelerator in the world, but the field also expands horizontally intosmaller, yet equally important applications. There are, of course, medicalapplications such as proton therapy which treats on the order of 8,000 patientsa year at 25 proton therapy centers in the US. There are even more biologicalapplications at synchrotron light sources: accelerators that give off X-rays asthey 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 NationalAccelerator Laboratory and offer scientists a chance to watch incrediblyfast 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 developinga type of accelerator that drives a thorium reactor (rather than uranium orplutonium which are limited resources as well as major safety issues). Thewaste 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 of10 megawatts, which does not exist yet, but plans are stirring.
Scientist all over the world arecontributing to plans for a project called the International Linear Collider,or ILC, a 31 kilometer electron-positron collider that would compliment theLHC. No country has granted space or funding yet, but there are already over2,000 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 protontherapy 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 comesback online. Fermilab has plans to continue leading the field by hosting atleast one of two proposed next generation projects. The first, Project X, wouldbe the first superconducting linear collider, the advantages of which areincreased stability and lowerwall-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 forbuilding such a machine is trifold: create, collect and make a beam out ofthese particles in less than a microsecond. The collisions would provide new physics to study and saveenergy and reduce size.
Particle-physicists certainly want to push the upper limit of accelerator power, but to go anybigger than the LHC would begin to cost in the hundreds of billions of dollars,which would require some major justification. So thenext generation, if they hope to continue to push the energy limits, must eventuallyreduce in size. This would not only mean big accelerators with even more power,but also making small accelerators smaller; so that, for example, protontherapy devices could it inside an office rather than a football field.
The leader in such technology comes from plasma wakefieldaccelerators, where particles sit in a plasma (rather than a vacuum) and in oneversion are accelerated with lasers. One bunch of electrons actually catches aride 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 traditionalR&D model for new accelerator technologies has been that the particlephysicists…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 wereally want…to turn around the time from the basic accelerator technologydevelopment to something you can use in a hospital, we need to get closerconnections between the people doing this kind of research and the people thatknow what they want to use it for.”