Photo Credits: DESY/SciComLab

“Accelerators are the central tools of particle physics,” explains Jürg Öhri, Sales Manager at VAT. “These massive instruments provide the decisive clues about what our universe is made of, what the original building blocks look like, and what holds it all together. For example, they have enabled the discovery of quarks, which revealed how fundamental forces of nature propagate, and the Higgs boson, an elementary particle that gives other particles mass.”

The current generation of particle accelerators use radiofrequency (RF) cavities to kick their particle beam up to high kinetic energy level before smashing them into other particles. By analyzing these collisions, scientists gain insight into the structure of the subatomic world and fundamental laws of nature. However, to achieve even higher energies that would enable scientists to peer deeper into how subatomic particles behave, future colliders would need to be even bigger than the world’s largest accelerator, the Large Hadron Collider (LHC) located at the CERN facility in Geneva, Switzerland. The largest machine in the world, the LHC is housed in an underground ring 27 km (17-miles) in circumference.

"The costs of designing and building even larger accelerators are high, very high," explains Jürg Öhri. “While funding to enable these larger facilities is being sought through worldwide research collaboration, some particle physics researchers are looking for alternative solutions. Their goal is to build new particle accelerators on a smaller footprint, which feature higher energy levels and better beam quality than existing systems – at a lower cost. Previously considered impossible, this concept may just become reality thanks to a new technology: the plasma wakefield accelerator."

Surfing on plasma waves

A plasma wakefield accelerator uses a laser or electron or proton beam to generate a charged wave that travels through the plasma at nearly the speed of light. This allows particles to surf on top of a plasma wave – accelerating the particles to higher energy levels in a shorter distance than in existing accelerators.

"If the concept is successful, plasma accelerators could drastically reduce the size and cost of such facilities," emphasizes Jürg Öhri.

Further development of the plasma wave technology – that would replace the RF cavities used in current particle accelerators – could yield an exponential increase in electron volts of energy over much shorter distances. Initial results of the “Advanced Proton Driven Plasma WAKEfield Accelerator Experiment” (AWAKE) at CERN reached one billion electron volts – one gigaelectron volt over a distance of only three centimeters.

“An ordinary accelerator would need distances of 150-200 meters to generate the same energy levels,” enthuses Jürg Öhri. “The most recent results achieved a level of four gigaelectronvolts over a distance of a mere nine centimeters, then an amazing eight gigaelectronvolts over twenty centimeters. That's a tremendous reduction in size!"

Global R&D effort – also for VAT

AWAKE is only one of many development efforts to find a smaller accelerator technology. Berkeley Labs, and the FACET project at SLAC (Stanford University), both in California, as well as the LAOLA project of the Deutsche Elektronen-Synchrotron (DESY) in Hamburg and Zeuthen (near Berlin), as well as JuSPARK in Jülich, all in Germany, are working on new solutions. DESY, for example, is testing a concept using a particle beam (instead of a laser) to generate a plasma wave.

The new concepts also place new demands on the system components, such as the vacuum valves. VAT's R&D teams are therefore on board when it comes to providing the desired technical solutions. VAT's development work focuses on the specific requirements of the high-energy environment of these experiments, such as extremely fast and precise valve functions and high long-term resistance to the extreme temperature and radiation conditions. The integration of different valve functions into a single compact, space-saving assembly is another aspect that VAT's growing portfolio of vacuum valves for plasma-related processes takes into account.

“Further tests on the wakefield concept are ongoing,” says Jürg Öhri. “The VAT valves that are part of the accelerator prototypes also continue to perform as expected – consistently meeting the project milestones for performance and reliability.”