Category: LHC

After a 2 year hiatus for a significant upgrade, the Large Hadron Collider is being switched back on and, early on Sunday, the world’s most powerful particle accelerator saw the first circulation of protons around its 27 kilometer ring of superconducting electromagnets.

This is awesome news, especially as there was a minor electrical short last week that could have derailed this momentous occasion for weeks, or maybe months. In one of magnet segments, a metallic piece of debris from the upgrade work had become jammed in a diode box, triggering the short. Manual removal of the debris would have forced a lengthy warm up and then cool down back to cryogenic temperatures, but CERN engineers were able to find a quick fix — by passing an electrical current through the problem circuit the tiny piece of debris was burnt away, no warm-up required.

With this small hiccup out of the way, the complex task of circulating protons around the LHC began this weekend, resulting in two sparsely populated beams of protons speeding around the LHC in opposite directions. So far, so good, but the particle accelerator is far from being ready to recommence particle collisions.

“Bringing the LHC back on, from a complete shutdown to doing physics, is not a question of pushing a button and away you go,” Paul Collier, head of beams at CERN, told Nature News.

Sure, the LHC is circulating protons, but it is far from restarting high-energy collisions. In fact, over the coming weeks and months, engineers will be tuning the machine to finely collimate the counter-rotating beams of protons and gradually ramping-up their speed. The first collisions aren’t expected to begin until June at the earliest.

But seeing protons pump around the LHC for the first time since 2013 is an awesome sign that all the high-energy plumbing is in place and the electrical backbone of the accelerator appears to be working in synergy with the massive magnetic hardware.

Over the next 8 weeks, engineers will turn on the LHC’s acceleration systems, boosting the beam energy from 450 GeV to 6.5 TeV, gradually focusing the beams in preparation for the first collisions.

According to Nature, the re-started LHC will slam 1 billion pairs of protons together every second inside the various detectors dotted around the accelerator ring with a collision energy of 13 TeV, boosting the LHC’s energy into a whole new regime. During the LHC’s first run, the maximum energy recorded was 8 TeV.

This makes for a curious time in cutting-edge particle physics.

Before the LHC was fully commissioned in 2008, its clear task was to track down, discover and characterize the Higgs boson, the last remaining piece of the Standard Model. Having achieved the Higgs discovery in 2012 — resulting in the 2013 Nobel Prize being awarded to Peter Higgs and François Englert — physicists have been combing through the reams of data to understand the new particle’s characteristics. Although a lot still needs to be learnt about the famous boson that endows all matter with mass, Run 2 of the LHC has a rather vague mission. But “vague” certainly doesn’t mean dull, we could be entering into a new era of physics discovery.

We’ve never seen collision energies this high before, and with the Standard Model all but tied up, physicists are on the lookout for phenomena with an “exotic” flavor. Exotic, in this case, means the production of quantum effects that cannot be easily explained or may be driven by mechanics that have, until now, been considered pure speculation.

Personally, I’m excited that the LHC may generate a signature that we cannot explain. I’m also trilled by the possibility of micro-black holes, the discovery of dark matter particles, potential hints of supersymmetry and quantum gravity. But I’m doubly-thrilled by the prospect of something popping out of the collision debris that doesn’t make any sense.

As the LHC will now slam protons (and, later, ions) at energies nearly double of what it was previously capable of, we are in uncharted territory. Physicists are recreating the conditions of the Big Bang, condensing primordial particles and forces from the concentrated energy of colliding beams of charged particles. So far, after only 7 years since the LHC was first powered up, it has already confirmed the existence of a Standard Model Higgs boson. So now, without a single ultimate goal, the LHC will do what physics does best, discovery-driven science that could answer many quantum mysteries and, hopefully, create many more.