Accelerator Report: HiLumi LHC Beam Reliability Runs Pave the Way to the Future

Why It Matters

Proving reliable, high‑intensity beam delivery is essential for the HL‑LHC to achieve its unprecedented collision rates and physics goals. Successful injector performance directly impacts the timeline and scientific output of the next generation of particle‑physics experiments.

Key Takeaways

• LIU upgrades double LHC beam intensity
• SPS delivered 2.3×10¹¹ protons per bunch
• Reliability runs showed 8 injections, 6 reached flat‑top
• Beam stability improved via cycle and orbit tuning
• Upcoming three‑week run will test night/weekend operation

Pulse Analysis

The LHC’s injector chain received a major overhaul during the 2019‑2020 Long Shutdown 2 under the LHC Injectors Upgrade (LIU) project. By boosting beam brightness and nearly doubling intensity, the upgrades prepare the accelerator for the High‑Luminosity LHC, slated to begin after LS3 (2026‑2030). Denser proton bunches—more than 2,000 per beam spaced 25 ns—will increase collision rates, sharpening measurements of the Higgs boson and rare processes while expanding the discovery reach for new physics. These improvements place CERN at the forefront of high‑energy research.

During 2026 the injector complex began a series of dedicated HiLumi LHC beam‑reliability runs. In the SPS, eight injection attempts were made, six reaching flat‑top energy, and 15‑20 bunches per run satisfied the stringent quality criteria. The machine delivered nominal parameters—2.3 × 10¹¹ protons per bunch, 2.1 µm transverse emittance, and 1.65 ns bunch length—demonstrating that the upgraded hardware can sustain the required intensity. Early stability issues were mitigated through refined energy matching, orbit corrections, local bump adjustments and the commissioning of a beam scraper, leading to progressively shorter times to first‑beam OK.

The next phase will extend reliability testing into nights and weekends for three weeks, stressing the injector chain under realistic operational loads. Successfully proving continuous, high‑quality beam delivery will be critical for the 2030 physics start, where the HL‑LHC aims to collect up to 300 fb⁻¹ per year, unlocking unprecedented precision in particle‑physics measurements. Beyond fundamental science, the technologies refined—high‑current RF systems, advanced vacuum control, and fast beam diagnostics—have spill‑over potential for medical accelerators and industrial applications, reinforcing Europe’s strategic leadership in accelerator engineering.