Linacs pushed to the limit in Chamonix

24 January 2020
Delegates at the 2019 International High-Gradient Linac Technology Workshop. Credit: HG2019

This past June in Chamonix, CERN hosted the 12th edition of an international workshop dedicated to the development and application of high-gradient and high-frequency linac technology. These technologies are making accelerators more compact, less expensive and more efficient, and broadening their range of applications. The workshop brought together over seventy 70 and engineers involved in a wide range of accelerator applications, with common interest in the use and development of normal-conducting radio-frequency cavities with very high accelerating gradients ranging from around 50 MV/m to above 100 MV/m.

Applications for high-performance linacs such as these include the Compact Linear Collider (CLIC), compact XFELs and inverse-Compton-scattering photon sources, medical accelerators, and specialised devices such as radio-frequency quadrupoles, transverse deflectors and energy-spread linearisers. In recent years the latter two devices have become essential to achieving low emittances and short bunch lengths in high-performance electron linacs of many types, including superconducting linacs. In the coming years, developments from the high-gradient community will be increasing the energy of beams in existing facilities through retrofit programs, for example in an energy upgrade of the FERMI free-electron laser. In the medium term, a number of new high-gradient linacs are being proposed, such as the room-scale X-ray-source SMART*LIGHT, the linac for the advanced accelerator concept research accelerator EUPRAXIA, and a linac to inject electrons into CERN’s Super Proton Synchrotron for a dark-matter search. The workshop also covered fundamental studies of the very complex physical effects that limit the achievable high gradients, such as vacuum arcing, which is one of the main limitations for future technological advances.

Vacuum arcing is one of the main limitations for future technological advances

Originated by the CLIC study, the focus of the workshop series has grown to encompass high-gradient radio-frequency design, precision manufacture, assembly, power sources, high-power operation and prototype testing. It is also notable for having a strong industrial participation, and plays an important role in broadening the applications of linac technology by highlighting upcoming hardware to companies. The next workshop in the series will be hosted jointly by SLAC and Los Alamos and take place on the shore of Lake Tahoe from 8 to 12 June.

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