Deep beneath the French-Swiss border, the world’s largest scientific instrument has fallen silent. After years of smashing proton particles together at nearly the speed of light, Cern’s Large Hadron Collider (LHC) has stopped operations and entered a long shutdown.

While no particle collisions are taking place at the LHC, thousands of scientists, engineers and technicians are dismantling parts of the machine, installing new technologies and preparing one of the most ambitious upgrades ever attempted in experimental physics.

When it switches on again, around 2030, it will become the High-Luminosity Large Hadron Collider (HL-LHC), capable of delivering roughly seven times more data than the collider that discovered the Higgs boson.

For me, this shutdown marks another milestone in a project that has shaped much of my scientific life. I first became involved in the High-Luminosity collider long before the Higgs boson particle was discovered in 2012. Over nearly two decades I have had the privilege of contributing to the programme on both sides of the Atlantic.

In the United States, I served as upgrade coordinator for the Compact Muon Solenoid (CMS), a key experiment at the LHC. The CMS is built at one of the points within the Large Hadron Collider where separate beams of proton particles collide. CMS then captures data from these collisions so that it can be analysed by Cern physicists. I helped lead the international effort preparing CMS for the HL-collider era.

Today, in Oxford, I work on another LHC experiment called Atlas. Atlas and CMS work in broadly similar ways, but having two machines like this helps ensure significant discoveries by one experiment are cross-checked by a counterpart with a separate team of scientists. Here, my colleagues and I are building silicon pixel detector modules for its upgraded inner tracker. This will form a vital part of........

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