pro8 2025 visits CERN

CERN in Geneva is the largest particle research centre in the world. Scientists there are working to understand the building blocks of matter. At the centre is the Large Hadron Collider (LHC), which accelerates particles to almost the speed of light and generates collisions in order to investigate the fundamental physical rules and forces. Through experiments such as ATLAS, CMS, ALICE and LHCb, researchers are gaining insights into questions such as the origin of the universe, the nature of matter and the laws of physics.

We started on Monday morning, 8 September 2025, with a visit to the Large Magnet Facility, which Gonzalo Hernando Irisarri guided us through. 

Some of the new magnets for the HL-LHC upgrade of the 27-kilometre-long particle accelerator ring are currently being produced in a huge assembly hall. What looks like a simple steel tube from the outside contains a lot of high-tech inside. As all of these magnets operate at superconducting temperatures, allowing the generation of the very high magnetic field required to steer the particles along their trajectory, flexible buffer elements (bellows) are installed between the rigid steel tubes to compensate of their thermal contraction. We learnt that dipole, quadrupole, and even higher order magnets are arranged in the tubes and that once the LHC is refilled with particles, it takes around 30 minutes for the protons in the ring to reach the maximum speed and maximum energy required for the various experiments.

We learned that dipole magnets are used in the accelerator ring to bend the beam and quadrupole magnets are used to focus the beam to increase the number of collisions that occur.

Davide Bozzini and Samer Yammine then showed us around a hall in which the IT string, a prototype of an HL-LHC machine section about 100 metres long, was fully built and will undergo a complete experimental program to start in the upcoming months. From July 2026 to July 2030, an extensive upgrade programme will be carried out at the LHC. On the IT string, most of the new magnet systems and ancillary components will be brought together in a substantial facility for testing purposes so that any potential difficulties in the design interfaces and assembly can be detected and corrected before implantation in the LHC tunnel. The IT string naturally also incorporates the latest superconducting cable technologies, which supply the magnets with extremely high currents to generate the magnetic field required to guide and focus the beams for highly luminous collisions. These cables have little to do with conventional cables, as cutting-edge materials of heavyweight superconductors are used in the facility.

We then had lunch in one of the CERN restaurants. The break did us good, as we were all buzzing with information.
Then we went on by bus to the CERN Prévessin Site. Here, Ms Flavia Düsselberg from HR Talents Acquisition presented the job opportunities CERN offers to interested students and graduates.

CERN is very interested in building up the interest of German applicants and increasing the proportion of German employees. Prof Dr Kristian Arntz, Dean of the Faculty of Mechanical Engineering and Mechatronics at Aachen University of Applied Sciences, then presented the pro8 competitive teaching module and invited participants to a round table discussion. Various very interested CERN employees listened to us explain pro8, which led to a lively discussion in a pleasant atmosphere over a cup of coffee.

After taking a group photo together, we continued to the CERN Control Centre, where physicist Maarten van Dijk gave us a guided tour. He had the rare gift of being able to explain complicated things in a simplified way, so it was a pleasure to listen to him.

We then visited CERN's BE-CEM-MRO robotics lab. The robotics team introduced us to the various robots that CERN works with and that are used for different tasks. During the operation of the particle accelerators and the collisions of the particles, higher levels of radiation are produced in some of the machine elements. Several regions in the tunnel can therefore only be entered by CERN staff after a long "cool-down" period. When components are being repaired, meticulously developed procedures are followed to ensure safety.

The robots can help intervene, especially in areas where there are safety and space limitations. They inspect tunnels and experimental environments long before humans can enter them, perform inspections, measurements, and remote manipulation tasks. Because CERN is constantly optimising its accelerators and particle collisions, robots will become increasingly important for maintenance work and the operation of CERN in the future.
 

As the last stop on Monday, Oliver Boettcher took us to the HiLumi (internal name for HL-LHC) WP8 workshop. This was precisely the task for which our students in the pro8 project had to present a technical solution proposal: the interface between the collider and the experiment. They had the challenging task of improving the guidance, positioning and cable connections for the VAX modules and the VAX box.

After spending a week working on this topic in pro8, it was very interesting for everyone to see how the whole thing actually works on site. As Antonio Alonso from the WP8 team and Edward Barnes (mechanical engineer working on the VAX modules) assured us, they will follow up and test some of the solutions suggested by our students.

Monday ended with a BBQ on the occasion of the 10th anniversary of the BE-EA group, to which we were invited. Surrounded by delicious barbecue flavours and a tasty buffet, we will never forget the nice and harmonious atmosphere among the CERN employees, who themselves provided the musical accompaniment for the evening with a lot of passion.

On Tuesday morning, 9 September 2025, we visited the ATLAS visitor centre. ATLAS is the largest LHC experiment by volume. In front of the building, we met François Butin, who was actively involved in installing the experiment in the huge underground cavern over 20 years ago. He came racing up on an electric unicycle, which he uses every day to cover the hundreds of metres between the various CERN facilities. At the entrance to the ATLAS building, where there was a display showing how many Higgs boson particle hits had already been detected, he pressed an inconspicuous button. Suddenly the wall became transparent and we looked through a huge window into the impressive ATLAS control centre.

We then went into a room where he presented us with a fantastic 3D show about the creation of ATLAS. Here we learnt that the discovery of the Higgs boson was announced in 2012 by the ATLAS and CMS research groups at the Large Hadron Collider (LHC) at CERN. The Higgs boson is an elementary particle in the standard model of particle physics that confirms the mechanism by which particles such as electrons, quarks and W bosons obtain their mass. Mr Peter Higgs had calculated and predicted it already in the 1960s, and it took more than 50 years for his theory to be proven. 

What an incredibly wonderful confirmation of one's own life's work it must be to experience - as Mr Higgs did during his lifetime - that a theoretically predicted particle is actually found and proven by experiments many years later!

We went on to a building that initially looked like a CERN museum. Here we were shown a short film about the creation of CERN. What looked like a surreal film set turned out to be the Synchrocylotron (SC for short), which was put into operation at CERN in the 1950s. So we were standing right in front of CERN's first particle accelerator, where it all began. On a timeline, we were able to read about important innovations and discoveries that were developed at CERN. In 1989, for example, a CERN employee, Tim Berners-Lee, created a web concept that he presented to the public in 1991. CERN later made the technology openly available, which contributed to the rapid spread of the World Wide Web.

The buildings on the CERN complex are getting on in years. Instead of futuristic-looking design architecture, you will find barracks and functional buildings with the concrete charm of the 1970s. Basic research is expensive and the question always arises: what's the point? But in the case of the WWW, you can see that it often results in amazing things for mankind that primarily have nothing to do with the actual research objective. The WWW data protocol was developed with the aim of being able to exchange research results with physicists on other continents more quickly and collaborate better.

Because clever minds at CERN are constantly working on finding solutions to universal questions and utilising all the expertise available worldwide, front-end technologies are often developed in passing.

Deeply impressed, we went on to the MME main workshop, where we were welcomed by Simon Barrière. He gave us a tour of the halls where the some of the most complicated mechanical parts needed by CERN for its accelerators and the researchers for their experiments are manufactured. The machinery and equipment here made the hearts of our mechanical engineering students beat faster. In another hall there were machining and measuring machines as tall as a house, which were operated from a driver's cab like a crane. Gigantic machines.

After the lunch break, we checked out of the CERN hotels and travelled to our last CERN station: the CMS detector on the French side. Here, Antje Behrens and Noemi Beni welcomed us in front of a window that gave us an insight into the CMS control centre. They handed out helmets, gave us a short safety briefing and then we took the lift down to a depth of around 80 metres. We walked past rows of control cabinets and data servers down to the area that was locked and where access is only granted when the particle accelerator is not running.

The strong magnetic field of the CMS experiment could be felt down here: a paper clip on a mobile phone aligned itself magnetically and a chain hung crookedly from the ceiling, as if someone was pulling on it. We only really realised the scale of this demonstration when we were told that the centre of the magnetic field was around 20m away in the middle of the detector, and that we were separated from it by a 7m-thick reinforced concrete wall.

When we got back up in the lift, we took a deep breath and went to the hall where the CMS particle detector was assembled, from pieces constructed all over the world. Large rings and disks forming the main parts of CMS, weighing up to 2000 tonnes, were lowered one by one through a huge shaft into the CMS experimental cavern using a special crane system that was rented especially for this job. As a reminder of the beauty and complexity of CMS, the 20m high wall at one end of the assembly hall has a 1:1 scale real photograph of the particle detector. In humility and awe, we gathered in front of it for a group photo, standing on a 3m-thick cover plate, under which there is a vertical 100m-deep shaft and the cavern with the huge detector. Then we set off on our journey home to Aachen.