The VELO subdetector, which for many years was one of the central components of the LHCb experiment at CERN, is back at Nikhef. This showcase of Nikhef technology is now on display in the institute’s lobby.
CERN Director-General Mark Thomson and LHCb Program Leader Mara Senghi Soares jointly unveiled the device in its display case on Thursday, July 9; it is a new addition to the Nikhef Expostrip. The VELO symbolizes the successful convergence of science and technology at Nikhef.
The VELO on display is the original subdetector, which operated flawlessly in the accelerator beam between 2010 and 2018. VELO stands for vertex locator, an instrument designed to pinpoint the exact location of proton collisions (the vertex) from which particle tracks originate in the LHCb detector.
VELO was built after the turn of the century for the LHCb experiment, which was under construction at the time. The project was an international collaboration involving at least ten institutes. Nikhef designed and built large parts of the mechanical structure, the motion system, the vacuum system, the cooling system, and the electronics for the subdetector.
At the unveiling, Nikhef Director Jorgen D’Hondt stressed how the VELO is a testament to the tremendous work of engineers and technicians in the development, construction, and operation of the LHC detectors.
VELO consists of two halves that can gradually close around the proton beam using a special transport system until they are less than a centimetre apart. The subdetector is located just outside the actual LHCb detector and is, in fact, part of the LHC accelerator beam.
VELO contains 23 silicon strip sensor panels positioned perpendicular to the beam, which together can record the first few centimetres of particle tracks. This information is crucial for reconstructing and analysing the particle tracks around the collision point and the decay points of unstable particles.
The installation of VELO1 at CERN around 2007 was also a Nikhef responsibility. After 2018, the first VELO was replaced by a newer version equipped with pixel detectors. Nikhef engineers then assisted with the dismantling of the first VELO and the installation of the upgrade. Part of this work took place during the COVID-19 pandemic.
The original detector was then stored for an extended period at CERN and was released last year for transport back to Amsterdam. Starting this week, the VELO display case further enriches the Nikhef Expostrip, an in-house exhibition about particle physics and the institute. The display was developed by Nikhef engineer Marco Kraan and Nikhef Communications in collaboration with designer Wiek Rozenmond, and was produced by LetterZ.
LHCb is one of the four experiments at the LHC accelerator at CERN. Nikhef is one of the partners in the experiment, with groups at the universities of Maastricht and Groningen and the Vrije Universiteit.
The LHCb detector was specifically designed to study differences between matter and antimatter in detail. The detector records particles and antiparticles released during proton collisions in a single direction. The oppositely charged particles are deflected in opposite directions by a strong magnetic field.
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