LS2 report: innovation to stop protons in their tracks


New PS internal dump produced in the framework of the LIU project 2020
New PS internal dump produced in the framework of the LIU project
(Image: Julien Ordan/CERN)

The old Proton Synchrotron (PS) is being decked out with ultra-modern equipment. As part of the LHC Injectors Upgrade (LIU) project, two novel beam dumps will be installed in the PS during the Long shutdown 2, in April, with a third waiting in the wings as a spare. Two of the three dumps are almost ready and will be commissioned following metrology checks and acceptance tests for the ultra-high vacuum. This equipment will enable the PS operators to stop any type of beam circulating in the machine when necessary and thus contributes to the safe operation of the accelerator.

This innovating beam dump is made of two materials, the second denser than the first, which absorb the energy of the particle beam. A first isostatic graphite block is used for its excellent resistance to thermal shock. The beam then meets a block made of copper, chromium and zirconium alloy, hot isostatically-pressed on three stainless steel tubes where the cooling water circulates. This last block efficiently evacuates the energy from the beam.

The new beam dump works differently to those normally used at CERN, where particles are deflected by a kicker magnet towards a static dump. Instead, the PS’s new beam dump moves to meet the beams, oscillating to block the vacuum chamber so that the particles’ trajectory does not need to be deflected.

The dump block oscillates up and down, gradually stopping all the beam particles. This technique is being used due to space constraints in the Proton Synchrotron: installing a static dump would have also required the addition of a beam extraction system which would take up too much room.

For François-Xavier Nuiry, the project leader, this is the culmination of more than four years spent developing a highly complex piece of equipment. “From the very beginning, the team’s commitment has amazed me. These beam dumps would not be here if it weren’t for their collective effort. It was also a great opportunity to train students and fellows in highly technical fields.”

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