So what’s next for high-energy physics? The LHC won’t be the end. Physicists will want to go to higher energies. The question is, how? The International Linear Collider — a planned linac that will do for positrons and electrons what the LHC did for protons — is what the community wants right now, but it won’t go to any higher energies. It might be too expensive to build just to match the LHC’s capabilities. Machines like the ILC struggle to achieve accelerating gradients of 30 MeV per metre, and the radio wave power delivered to the metallic cavities would melt them were they not supercooled and superconducting.
But all is not lost. SLAC’s Mark Hogan gave a talk about all the novel accelerating technologies in the works. He presented the so-called Livingston chart, which at right shows the hard-won exponential increase in accelerator energies with time. Every few decades or so, an order of magnitude increase in energy is earned. But you can also see how each successive family of accelerator technologies – cyclotrons, synchrotrons, storage rings – leap to new heights, but taper off with time. Something has to be done. And Hogan thinks that wakefields will be the way to go — using initial pulses to create a wave in a plasma, or a fiber, that in turn allow successive electron pulses to surf on the wake.
Of course, the technology is years away — but it could offer gradients in the GeV per metre range. That would put desktop light sources within reach. Who knows — maybe there could be desktop colliders, too. The future is wide open. But my future at Lepton Photon is quite limited. I am skipping out on Friday, the last day — but have enjoyed my time in Hannover thoroughly. Thanks very much to the organizers.