On April 3 last year, the left-hand side of the Fermilab Today website had a graphical weather forecast depicting storm clouds. It was a fitting metaphor for the mood of the US lab, which had recently discovered that one of the “quadrupole” magnets it supplied the European lab CERN for the Large Hadron Collider (LHC) had failed a preliminary test. On the right-hand side of the website, Pier Oddone, the director of Fermilab, admitted they had taken “a pratfall on the world stage”.

Indeed they had. The failure meant they had to replace all similar magnets with redesigned models and skip the low-energy test runs that were due to take place before winter. It also added to the problems that forced CERN to delay the LHC’s (already repeatedly delayed) start up from May to July this year.

Now, though, everything looks to be well again. On the right-hand side of Fermilab Today, Oddone writes that the first of the replaced magnets has passed the test it failed last year. He writes that the 50 or so scientists, engineers and technicians at CERN who made the repairs deserve “a crown”. And the left-hand side of the website is forecasting sunshine.

The original problem was that the magnets had inadequate support to withstand the forces produced during “quenching”. This is when a magnet gets warmed up above its 1.9 K operating temperature, and could happen happen, for example, if one of the LHC’s proton beams veers off course. Last Friday the replaced magnet passed the one-hour test designed to simulate quenching.

“Everyone commissioning the LHC,” writes Oddone, “both accelerator and detectors, is racing excitedly towards colliding-beam operation and the great physics results that we can almost taste.”