Inside Science at CERN: HL-LHC Upgrades, CLOUD Aerosol Lab and the Future Circular Collider

The episode takes listeners on a guided tour of CERN to unpack the physics driving the Large Hadron Collider upgrade and the tech that makes collisions more frequent. It also dives into the CLOUD aerosol lab where cosmic rays and beams are used to study cloud formation and climate-relevant aerosol chemistry, then looks ahead to the Future Circular Collider proposal for precise Higgs measurements. Interwoven are Open Skylab soil experiments repurposing tunnel mollasse and a glimpse of the broader research ecosystem at CERN.

• HL-LHC upgrade aims for about 10x more collision events by increasing fuel, tightening the beam and using stronger superconducting magnets with crab cavities.
• The CLOUD lab uses beam-induced ionization to simulate atmospheric conditions and investigate aerosol formation, linking fundamental physics to climate modeling.
• The Future Circular Collider concept would tunnel 91 km for electron-positron collisions to measure the Higgs with unprecedented precision.

Overview and on-site context

The podcast takes the listener on location at CERN, descending into service tunnels and then into the underground facility where major upgrades are underway. The team explains why the accelerator complex is being upgraded: to increase the rate of proton-proton collisions so researchers can probe rarer events and extend the reach of the Standard Model. The conversation emphasizes not just the physics goals but the engineering feats required to significantly boost luminosity, including injecting more protons, densifying the beam, and installing powerful superconducting magnets that function like optical lenses for particles. A key feature is the crab cavity innovation which aligns beams for more effective collisions and raises the overall collision rate.

The Large Hadron Collider and its upgrade

Listeners hear about the LHCs Large Hadron Collider, the purpose of proton beams, and how collisions are detected by massive particle detectors. The deputy project leader Paul Fessia explains the Illuminosity LHC project and how the upgrade will increase event production by approximately a factor of ten. The discussion covers the physics rationale for pursuing higher collision rates, including the need to explore physics beyond the Standard Model. The episode also introduces the crux of beam physics: reoptimizing beam shape, cross-section, and collision geometry to maximize the probability of protons meeting each other. The role of sophisticated magnets and the crab cavities in achieving tighter, more synchronized collisions is highlighted as a central upgrade component.

What would excitement look like in this upgrade?

Interviewees emphasize that the real thrill would be discovering something unexpected, potentially opening new doors in particle physics or enabling energy-recovery technologies that reduce the machine’s environmental footprint. The discussion also touches on the machines electricity use, describing the upgrade as a substantial energy draw comparable to a mid-size city, and outlining efforts to recover energy from magnet systems for re-use.

The CLOUD aerosol lab and climate connections

Eva Sommer explains CERNs Cloud Run project, an environmental science experiment housed in a large, insulated chamber designed to study cloud formation. The cloud chamber is described as a near-ideal, ultra-clean environment where researchers can isolate specific molecules and microphysical processes. They explore why such a facility is at CERN: to modulate ionization rates with a particle beam, approximating high-altitude atmospheric conditions where cosmic ray ionization is higher. The aim is to constrain microphysical aerosol processes so climate models can predict cloudiness and thus cooling effects more accurately. The lab uses marine trace gases, including dimethyl sulfide, to simulate marine aerosol formation and to examine how certain compounds participate in particle formation, which has implications for the climate system and our understanding of atmospheric chemistry.

Clouds, aerosols and natural sources

The Cloud Run team discusses how natural sources, such as ammonia from agriculture, contribute to cloud condensation nuclei formation. They emphasize the importance of isolating variables in the aerosol chamber to understand fundamental mechanisms while acknowledging the real atmosphere’s complexity. The conversation covers the environmental significance of marine aerosols, the role of sulfuric acid and newly investigated components like MSA, and how this work informs climate predictions by reducing uncertainties about cloud formation and aerosol-cloud interactions.

Open Skylab and soils from CERNs tunnels

In a separate thread, Christiana Staudinger introduces Open Skylab, a project to convert mineral waste from the tunnels into engineered soils. The process involves crushing mollasse rock to a 0–20 mm range, mixing with organic amendments and microbial inoculants, and then observing soil formation, nutrient cycling and biomass production. The goal is to develop soil formulations that hold water, filter and sustain plant life while enabling microbial and plant colonization. The segment highlights hedgerows and biodiversity-minded planting strategies as a demonstration space for potential soil-building approaches that could repurpose tunnel waste and contribute to sustainable land-use projects.

The Future Circular Collider and the broader physics agenda

The show turns to the Future Circular Collider concept, a 91 km circumference accelerator designed for electron-positron collisions, intended to complement the LHCs proton-proton program. The discussion covers why electrons and positrons offer a cleaner collision environment than protons, enabling precise Higgs boson measurements and broad physics improvements. The project costs are discussed at around 15 billion Swiss francs, with expected approval in 2028 and tunnel construction in the 2030s, potentially starting operations in the mid-2040s. The interview also notes the physics consensus about pursuing a collider with greater reach and precision and the debate within the community about the projects scale and cost. The episode ends with a reminder that the CERN site remains a living laboratory, where the open exchange of ideas and exploratory science continues, even while heavy construction is underway in the background.

Closing reflections

As the podcast closes, the team reflects on CERNs role as a hub for collaboration among physicists, engineers, and environmental scientists. The message is one of curiosity and caution: the future of fundamental physics, climate science, and soil ecology depends on both bold ideas and careful, incremental progress. The final impression is that the work at CERN is about pushing the frontiers of knowledge and testing new technologies, all while fostering a community that can adapt to unpredictable discoveries.