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Powering the European Spallation Source

STFC and the University of Huddersfield have successfully delivered the final assignment of radio frequency distribution system waveguide runs to the European Spallation Source (ESS) project in Lund, Sweden. The hardware has also been installed and tuned onsite, a milestone achievement in the ESS programme.

What is a radio frequency distribution system (RFDS)?

The RFDS will deliver power to the accelerating cavities in the linear proton accelerator which is currently under construction in Lund, Sweden.  The system is designed to take power from the main power source situated above ground, into the radio frequency cavities which will be situated in the accelerator tunnel 5m below ground.

This will be done via waveguides – components which, as the name suggests, will guide power (in the form of RF waves) to the correct cavity. Each cavity will be serviced by an individual waveguide run, which has resulted in nearly 5km of aluminium waveguides and 100 tonnes of steel support structures being designed and specified by the STFC team.

Richard Smith, STFC Mechanical Engineer commented: “In terms of sheer scale, this has definitely been the largest project I have worked on. The huge volume of components and their physical size have made this a unique and challenging project. For example, every one of the 19 support structures we designed for the power delivery system was the size of an average 3 bedroom house and each one supports over 15 tonnes of equipment. These massive steel structures now populate the 500 metre-long gallery and represent some of the first major pieces of accelerator equipment to be installed at the world’s most powerful neutron source. This feat is something that I am very proud of and could only have been achieved through the team’s collective hard work and enthusiasm to collaborate with ESS on every level.”

The STFC and University of Huddersfield partnership

STFC colleagues from Daresbury Laboratory have been working in partnership with a small team based across RAL and the University of Huddersfield who have expertise in tuning and commissioning this type of equipment.

Faced with a huge empty hall when the project began in 2016, the team have designed the RFDS support structures, created and overseen the tender process, managed installation issues in Sweden and, more recently, been involved in the tuning of the components.

Prior to the COVID-19 travel restrictions, a small team of STFC staff, spent a significant amount of time in suppliers' factories performing various tests and inspections. This took the team all over the world, from the very tip of Scotland, to Slovakia, Germany, and all over America. Gerard Bell, the Engineer with responsibility for quality assurance and quality control on the project, would spend much of his time in Maine, USA. When faced with providing specifications for components, Gerard would work closely with the manufacturers to make sure that every element was the very best it could be – ensuring that they will stand the test of time when the ESS begins to conduct experiments when the build is complete. The high standards the team set have become benchmarks for future projects to follow, both at STFC and ESS.

Gerard Bell, explained: “Some initial batches of equipment weren’t up to the required standard, and a considerable amount of time was spent working with the supplier to turn things around. With the helpful guidance of the STFC procurement team and ESS, we achieved a quality level that I think we can now be very proud of. This in turn was recognised by the supplier and ESS.“

The ESS RFDS system in numbers

  • >100 tonnes of steel structures
  • 5,256 waveguide pieces
  • Nearly 5km of waveguides
  • 106 loads – these absorb any power which gets reflected through the system and could damage it if not managed
  • 106 circulators – pass the power from one part of the structure to the next
  • 238 arc detectors – ensure that power arcs are detected and managed
  • 428 duel directional couplers
  • 62 shutter switches
  • >600,000 fasteners - nuts, bolts, screws...
  • 76 shipping containers
  • Just 7 team members from STFC and the University of Huddersfield

Project Manager Paul Aden relays how this project has been completed: “The radio frequency distribution system for ESS has been a triumph of teamwork. We had, at peak, just seven people working on this project which meant that we all had to be very clear of what was needed and by whom. Our engineers have worked incredibly hard to bring our suppliers on board to make sure that we were designing, and they were creating, the absolute top spec for every single piece – be it a small bolt, huge steel support structure or a cutting-edge arc detector system. The complexities of building for a proton accelerator means that we can’t just take parts off the shelf, many of our components are bespoke designs. We have of course worked closely with ESS and other in-kind partners to make sure that the installation and tuning onsite all went smoothly – even when we couldn’t be there. It has been very rewarding to get to this point but is a terrible shame we can’t finish it off in the same manner which we started: with friends and colleagues.”

Although the physical hardware has now all been delivered and fitted, the team will still be involved in the RFDS project for the coming months: offering ongoing support and advice from the Daresbury Laboratory team and additional equipment design and analysis work from the University of Huddersfield.

The radio frequency distribution system is one of several work packages being delivered by STFC and other partners as part of the UKs in-kind contribution to the ESS project. A small project team based in STFC’s ISIS Neutron and Muon Source is managing the programme including the crucial interfaces to the ESS project.

For more information about the ESS, you can visit the ESS website.

Watch this video to find out more about STFC’s involvement in ESS-UK.


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Last updated: 19 February 2021

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