New Electron Beam Facility proposed for CERN

he design of a potential new electron facility at CERN has been published as a conceptual design report (CDR). The so called eSPS project, will involve injecting electron beams into the existing CERN super proton synchrotron (SPS), and has been designed by a collaboration including several researchers from the John Adams Institute. Published on 18th December 2020, the CDR can found here.

The primary use of the eSPS would be to contribute to the search for dark matter. The famously illusive particles have so far evaded discovery from the world's scientists with all searches showing negative results. Typically these searches have looked at candidate particles of either a very low mass, a few eV, or a very high mass, of order a few TeV. A new experiment, proposed to utilise the beams produced by the eSPS and known as the light dark matter experiment (LDMX), will use missing-momentum techniques to search for dark matter particles in the mass range we typically see most ordinary matter occupy, of order a few GeV.

As well as providing beams for the LDMX, the eSPS facility will act as a test-bed for the proposed future collider projects, the compact linear collider (CLIC) and the future circular collider (FCC), marrying technology from both in its design. The electron beams will be accelerated by a 3.5 GeV X-band linac, utilising high gradient CLIC accelerating cavities. The beam would then be transferred into the SPS and accelerated by superconducting cavities, similar to those required for the FCC-ee project, to an energy of 16 GeV when it would then be directed to the LDMX.

In addition to its use in the search for dark matter, the eSPS beam could be used for a plethora of different research and development projects. As well as the vital next step that the facility would provide in the development of CLIC, there would be an opportunity to do research into plasma wakefield acceleration, the production of positrons beams for future colliders, and beam instrumentation.

Oxford DPhil student Luke Dyks (pictured), who worked on and co-edited the CDR, said that the facility,

Provides an excellent opportunity for electron beams to be brought back to CERN. The eSPS would be an incredibly useful project both in the search for dark matter as well as for the future of accelerator design. I thoroughly enjoyed working on its design and will follow its future closely, I am hoping to be involved as much as possible in that future!