Job Shadowing @ GTA section, CSS Group, BE Department, Cern, Geneva
From mid July to early August 2025, I spent three weeks at CERN, the European Organization for Nuclear Research, working with the Control-Software & Services Group in the Beams Department as my internship for the TUMKolleg. While CERN is best known for its massive particle‑physics experiments, the internship gave me a close‑up view of how modern science depends on sophisticated software and teamwork.
I arrived in France on Sunday, where I was living for the duration of the internship. On my very first Monday morning I traveled to the main CERN site in Meyrin, Switzerland, to collect my security badge, a prerequisite for accessing any of the labs. After clearing security, I boarded CERN‘s dedicated shuttle that crosses the border to the French campus in Prévessin.
When the shuttle pulled into the French side, the area looked very inconspicuous even though the LHC (Large Hadron Collider) control center was just across the street from the office I would be working in for the next three weeks. But from the inside of the control center, it is a whole other story. I was allowed a brief tour, and seeing the rows of monitors with all of the data of the experiments left a lasting impression.
My first assignment was to become comfortable with the development environment the team uses daily. Over the next few days I dove into Java Spring, a framework that helps developers build reliable backend services.
Midway through the first week I transitioned to the frontend side of things, working with Angular, a popular JavaScript library for building interactive web pages. Together with the Material Design component library, I learned how to craft clean, responsive layouts that look good on both desktop monitors and tablets. To cement what I’d learned, I created a tiny ToDo list application. It was a modest project – just a place to add, check off, and delete tasks – but it forced me to apply the new skills in a concrete way.
Around the end of the first week the team introduced me to their current main effort, WRAP (Web‑Based Rapid Application Platform). It is essentially a “no‑code” environment that lets engineers assemble control-system dashboards without writing traditional code. Domain experts – physicists, engineers, technicians – could prototype and iterate on interfaces themselves, reducing the bottleneck that often occurs when only software developers are allowed to make changes.
For the last two weeks I tackled a more demanding problem: designing an event-management system for experiment data. In high energy physics, detectors generate streams of events that must be processed in strict chronological order. However, due to network latency and hardware quirks, events sometimes arrive out of order or a few seconds late. The solution we implemented involved a buffering mechanism. Incoming events are temporarily stored, sorted, and then released in the correct sequence once we’re confident no earlier events will appear. This ensures downstream analysis modules receive a clean, ordered stream, preserving the integrity of the data.
Beyond the technical work, daily life at CERN was rich with cultural exchange and collaboration. Weekly standup-meetings gave everyone a chance to share progress and the topics during the coffee breaks ranged from international politics to the current Marvel film.
During one weekend, I also visited the CERN Science Gateway in Meyrin, which I can not recommend enough to anybody coming nearby. Not only was the exhibition very interesting, not as simple-minded as in some museums and also not to advanced, but there was also a very interesting show on the topic of superconducting magnets which was very fascinating.
Looking back, the three weeks felt both intense and rewarding. I left with a deeper appreciation for how software, hardware, and scientific ambition intertwine.
The experience clarified several possible career directions for me. I’m grateful for the mentorship and the chance to get an insight into one of the most ambitious scientific enterprises on Earth.
