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A new target to explore the unknown

The BDF facility is being designed for dark matter and hidden sector experiments


BDF target prototype assembly
Assembly of the target prototype before installation (Image: Julien Ordan/CERN)

The Physics Beyond Colliders programme encompasses several new proposals and experiments that aim to use CERN’s infrastructure for new explorations. One of these proposals, which is currently awaiting approval and is being discussed in the context of the European Strategy for Particle Physics, is a facility that will use the beams of the Super Proton Synchrotron (SPS). This facility, known as the Beam Dump Facility (BDF), is based on a “beam dump” target for high intensity beams. 

The target, located 15 metres underground, will stop the main proton beam and produce mainly charmed mesons to enable physicists to carry out research on dark matter and the hidden sector. The aim is to observe the existence of very weakly interacting hypothetical particles. 

The 1.5 metre thick target will be capable of absorbing all the energy of the SPS beam which should reach an average power of 355 kW. This is why the BDF set-up is more like a beam dump than a traditional fixed target. Furthermore, the target will be very dense in order to produce heavy hadrons while also stopping lighter particles. 

The BDF will be significantly more sophisticated than the existing targets and will therefore need a complex shielding and handling system. The target will be surrounded by approximately 3,700 tonnes of cast iron and stainless steel shielding. The target and the shielding will be handled remotely and maintained by robots and cooled. 

How will the facility work? A proton beam produced by the SPS will be sent along the existing extraction line to the North Area through a separator that will then direct the beam towards the new target. A new junction cavern and a new transfer line will be built. 

The BDF facility will inter alia feed into the Search for Hidden Particles (SHiP) experiment which is designed to look for extremely weakly interacting particles within the hidden sector as well as dark matter particles. If the SHiP experiment is approved it will enter a technical design phase followed by a five-year construction phase and should produce its first set of data at the earliest in 2028. 

Last year, the BDF team tested a prototype target to gauge the feasibility of the project. The target resisted the impact of the beam and confirmed the results of simulations, giving confidence that the characteristics needed for the final design can be properly simulated and achieved.