Photo: © CERN; Impressive: 21 metres long, 15 metres in diameter and weighing 12,500 tonnes – the CMS detector takes up to 40 million measurements per second.

100 metres below ground

Automated air analysis at CERN with Festo valve terminal VTSA

At CERN, the world’s largest particle physics laboratory, thousands of scientists are working hard to figure out the unsolved mysteries of physics. Their valuable scientific research is supported by the intelligent and flexible application of automation technology. The Festo valve terminal VTSA controls the analysis processes of the air in the experimentation cavern of the Compact Muon Solenoid detector (CMS).

Deep underground, close to Lake Geneva, at the Large Hadron Collider (LHC) particle accelerator of CERN, the European Organization for Nuclear Research, huge detectors sift through a stream of subatomic particles and collect gigantic volumes of data, which are analysed using powerful algorithms. Modern technologies are making the tiny particles that hold the cosmos together visible on a larger scale.

The existence of matter

In 2012, a milestone in particle physics was achieved with the discovery of the Higgs boson particle. Scientists Robert Brout, François Englert and Peter Higgs had first predicted its existence back in the 1960s. According to the Standard Model of particle physics at the time, there should strictly speaking be no mass. Subatomic particles should move at the speed of light. Yet, as previously stated, they should be massless. The three researchers nevertheless developed the theory of the Higgs field. According to this theory, the Higgs field slows down the smallest particles – comparable with beads flying through honey – giving them inertia and therefore mass. 50 years later, the big breakthrough finally came. Protons were accelerated at virtually the speed of light in the LHC to allow them to collide. Higgs bosons broke free from the Higgs field and it was thus possible to measure them and prove that they actually exist. And so the existence of matter was proven. Higgs and Englert were awarded the Nobel Prize in Physics in 2013 for their theory. Brout had died in 2011.

The biggest of its kind

The research conducted at CERN involves scientific work with breathtaking dimensions. Established in 1954, the research organisation receives almost 1 billion euros in funding every year from 22 member states and currently employs more than 2,500 scientists. Over 12,000 guest scientists from all over the world work on CERN experiments. The world’s largest laboratory for particle physics operates a network of several accelerators which prepare various particles for a wide range of experiments. These include muons for researching the structure of the proton, heavy ions for creating states of matter and radioactive ion beams for observing exotic nuclei.

The world’s largest and most powerful particle accelerator is the LHC. It is located around 100 metres underground in a circular tunnel with a circumference of 27 kilometres. The LHC uses strong electric fields in order to transmit energy to particle beams and guides the beams through the system using magnetic fields. The particles acquire more and more acceleration energy until they travel around the LHC at close to the speed of light – 11,245 times per second. When they collide, four huge detectors – CMS, ATLAS, ALICE and LHCb – record what happens.

The LHC particle accelerator is located close to the border between France and Switzerland and lies at a depth of around 100 metres.

The LHC particle accelerator is located close to the border between France and Switzerland and lies at a depth of around 100 metres.

Safety always takes priority

The CMS detector is a technologically advanced detection device measuring 21 metres in length, 15 metres in diameter and weighing 12,500 tonnes. Composed of 100 million individual measuring elements, it takes up to 40 million measurements per second and is one of the most complex and precise scientific instruments ever built. To prevent measurement errors, all influencing factors must remain within defined tolerances.

These influencing factors also include the composition of the ambient and venting air in the underground caverns. To ensure consistently correct operation, air is continuously extracted and analysed at more than 100 measuring points inside and outside of the detector. This is all the more important given that the word “Compact” in the name also means that it is not possible to intervene quickly anywhere and at any time. In a critical situation, such as a gas leak or a fire in the detector, it would take up to two weeks to reach the emergency openings to access the inner areas.

Intelligently automated

In the past, each individual air pick-off point had a separate analytical device, which led to high costs. Furthermore, the maintenance costs and possible failure rate were too high for CERN standards. Since the beginning of 2016, valve terminals type VTSA have been ensuring that the air flows are guided to the analytical devices by the fastest route possible. The new solution reduces the number of analytical devices required by a factor of 10. The air flows are now combined centrally and assigned to downstream analytical devices. The main valves of the VTSA are piloted with compressed air and have the advantage of being insensitive to the magnetism of the CMS detector. The valve terminal was configured to the specific requirements of CERN. The most important technical adaptation was reversible operation.

In normal operation, the air from a measuring line is routed through the valve terminal to the downstream analysis station. At the same time, all the other measuring lines are permanently primed in low pressure operation. The current ambient air is therefore available at the valve when changing over to the next measuring line. This flexible application shows that the high-quality standard components of the VTSA can provide an intelligent technical solution that delivers a long-term efficiency gain for the CMS both in terms of performance and cost.

Small step, big future

The joint project for automated air analysis began in August 2015, and the units were delivered at the end of October. The new system was commissioned at the beginning of 2016. “Festo was an obvious choice to supply this technology given that we have been using Festo products in CERN and CMS for many years and are very happy with them”, explains Gerd Fetchenhauer, CMS Gas Safety Officer at CERN.

Whereas in the past it was primarily individual components that were purchased, the ready-to-install system solution is the first of its kind in the many years that Festo and CERN have cooperated. It lays the foundation for similar applications in other detectors of the Large Hadron Collider so that small steps can continue to lead to major new scientific discoveries.