Preparations for the UK’s contribution to the international Proton Improvement Plan II project (known as PIP-II) are well underway – with teams from the Science and Technology Facilities Council (STFC) readying facilities at Daresbury Laboratory, the cleanroom facility to be used for the string assembly for the cryomodules.
When it opens at Fermi National Accelerator Laboratory (Fermilab) in the US, the PIP-II particle accelerator will power an intense neutrino beam for the Deep Underground Neutrino Experiment (DUNE). The high-energy neutrino beam will travel an amazing 1,300 kilometres straight through the earth, across three states, from Illinois to South Dakota.
Cryomodules are key parts of a particle accelerator. They hold the cavities and need to be taken down to very cold temperatures, around 2 Kelvin, in order to accelerate the beams.
Because the PIP-II cryomodules will contain six cavities, along with other instrumentation, they will be much larger than any the lab has dealt with before. In order to accommodate them during the building (string assembly) phase, a new cleanroom, with specialist tooling, has been integrated into the labs existing cleanroom suite.
The cleanroom journey
Six superconducting cavities will enter the new cleanroom to create a 10 metre-long string. This is where cavities are aligned and connected together following processes and procedures meeting ISO4 cleanroom standards. In order to work with these cavities, the new cleanroom is 13.9m long 4.3m wide and 2.75m high with a volume of 163.7 cubic metres. Not only is the new cleanroom impressively large, but there is a single rail system cutting through the centre of the room to move the string assembly out of the cleanroom to the next workstation to continue with the building process.
From transporting the string of cavities on the rail to the next workstation, the cavities are then put onto the strongback assembly which enables the building process to commence for cold mass cell. The cold mass cell is a mechanical assembly of components and cryogenic circuitry for the module during operation. Once complete, the cold mass cell is moved further down the rail and is inserted into a vacuum chamber.
The final station on the rail line, so to speak, sees the final touches with the vacuum chamber emerging as a completed cryomodule.
How clean?
The new facility has been classified as ISO 4, for the main assembly area. This means that the number of 0.5 micron-sized particles in the air cannot exceed 350 particles per cubic metre.
That might sound like a lot, but in ambient air, in the room you are sitting reading this right now, there will be approximately 3.5 million particles per cubic metre. These microscopic particles of dirt, skin, pollution, and more, can cause accelerators to underperform, or even break. But with years of scientific research dependent on them, our teams use cleanrooms to mitigate the risks of contamination.
STFC are delivering various work packages for the PIP-II project as part of the UK’s scientific contribution. Other work at Daresbury includes the cryomodule transportation modules, and building anode plane assemblies for the DUNE detector which has seen a huge bespoke factory built at DL.
When completed, the 800MeV PIP-II linac will generate a proton beam exceeding 1MW.
The original article appeared here.
