New Cern particle accelerator to triple speed of proton beams into LHC

A new particle accelerator unveiled at Cern this week will more than triple the speed of beams being fed into the Large Hadron Collider (LHC), rising from 50MeV to 160MeV.

Stretching for almost 90m at a depth of 12m below the ground, the Linac 4 will replace an older unit which has been in service since 1978. The linear accelerator will feed the Cern complex with higher energy particle beams, allowing the LHC to reach higher luminosity by 2021 as scientists continue their project of measuring the properties of the Higgs boson. The increase in luminosity indicates a rise in the number of particles colliding within a set time, with plans for it to increase by a factor of five by 2025.

Cern director general Fabiola Gianotti called the Linac 4 “the first key element of our ambitious upgrade programme”. It will become the first step in Cern’s accelerator chain, delivering beams of protons to a wide range of experiments.

Scientists hope the increased luminosity from Linac 4 will allow them to collect 10 times more data than before between 2025 and 2035. Gianotti said it will “considerably increase the potential of the LHC experiments for discovering new physics and measuring the properties of the Higgs particle in more detail.”

Despite stretching almost 90m, the Linac 4 is half the size of the Linac 2, which it replaced. The smaller size allowed engineers to almost double the frequency it operates at to 350MHz. The new structure accelerates particles faster and has more than tripled the potential energy output, meaning the particles leave the machine quicker than before. The smaller size also made it easier to build, said Frank Gerigk, the engineer responsible for the Linac’s accelerating structures.

Although the Linac 4 will be used with the LHC, Gerigk said the accelerator could have many other potential uses. It could theoretically be used for proton beam therapy, destroying deep-lying cancer cells with highly focused beams while minimising damage to surrounding tissue. The treatment is suitable for dealing with complex childhood cancers as well as tumours at the base of the skull or the spine.

“It could also be used for an ADS (accelerator driven system),” Gerigk said. “These are systems which could be used to transform long-lived nuclear waste into much shorter-lived versions. That is something an idea which came from Carlo Rubbia, the Cern Nobel prize winner from many years ago.” Although the idea has not been put into practice, Gerigk said researchers in India and China are making “great progress” with the technique.