​CERN's souped-up Large Hadron Collider to launch again after Higgs boson hiatus

CERN hopes to find dark matter this year with its refitted LHC, which can produce beams powerful enough to melt a car.
Written by Liam Tung, Contributing Writer

Nearly two years after CERN shut its Large Hadron Collider (LHC) down for repairs, scientists are once again gearing up to smash particles inside the chilly 27km ring - only this time with enough energy to blitz one tonne of copper.

The LHC's three-year "season two", as CERN calls it, will begin later this month with super-charged equipment and injectors capable of producing 13 tera-electron-volt (TeV) energy collisions, nearly double the 8 TeV that was possible in 2012 when CERN researchers discovered the Higgs boson quantum particle.

While the LHC has produced one Higgs boson particle, the researchers are hoping the more powerful LHC, which is capable of producing one billion collisions per second, will increase the chances of creating Higgs bosons during collisions and thus provide more opportunities to compare experiments with the Standard Model of particle physics. After all, there could be an entire family of Higgs boson particles that weren't discoverable with the less powerful collider.

And, if nature is kind, the collisions may also present a chance to look at dark matter. However, at a press launch for the refitted LHC, CERN scientists warned it could take two decades to find dark matter.

"We don't know if we're going to find dark matter this year. We don't know. We want to find out what nature has in store for us and it could be that dark matter is in a place where we can start to produce it and see it this year. Or it could be that we'll only really start to see signs of it with more years of data. It could be it'll take us 20 years," said Dave Charlton, a spokesperson for the ATLAST experiment at CERN.

Still, there are hopes a more powerful collider will bring new discoveries. The advantage of more energy can be explained by Einstein's famous equation E=MC2.

"This says that mass is equivalent to energy. If you want to produce a new state of matter that has a certain mass, then you need to have the energy to produce it. Until now, we have not found things like dark matter or other evidence of new particles which go beyond the Standard Model. Having higher energy allows us to access a new mass regime," CERN physicist and head of Compact Muon Solenoid, Tiziano Camporesi, said.

The more powerful LHC is also expected to generate tonnes of data. In 2012, the LHC was generating one petabyte a second when it was in operation. However, CERN only kept a fraction of that, amounting to a still hefty 30PB of data a year (roughly 1.2 million Blu-ray discs).

Answering a question from ZDNet, Charlton said the new LHC will produce about five times more data than its predecessor, while the LHC's detectors will pick up twice as much data, requiring a tough compression regime. Camporesi however added that CERN wasn't using "brute force" to cope with the data explosion, adding the centre wouldn't need an "exponential increase in computing power".

Besides boosting its energy capacity, CERN has also hardened the LHC with new magnets, equipment to produce higher energy and narrower beams, improved cryogenics, radiation-resistant electronics and a more secure vacuum to accelerate particles through.

Given the near total refit of the LHC, CERN isn't rushing to fire up its first particle collisions, in part because the more powerful LHC has the potential to melt a car. The first collisions are expected to begin by June after more testing.

"This is nearly a new machine," said CERN's director general, Rolf-Dieter Heuer. "You have to remember that during the shutdown we opened the machine essentially every 20 metres, all connections between the magnets were inspected, 30 percent of the connectors were redone. A 100 percent of these 10,000 connectors have been reinforced to be rock stable, even if the magnets move as they cold to warm or the other way around."

"You need to be very careful about switching on high power lasers, so to speak, because it has enough power to could melt 500kg of copper - each beam, both beams together, one tonne of copper. Actually, we don't want to do that," said Heuer.

Safety at the LHC has been improved with extra safety valves fitted along the collider, which can be used to release excess pressure from the liquid helium that is used to cool the superconducting magnets.

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Those magnets along the ring help boost the energy of particles that travel along two separate tubes with a seriously powerful vacuum that, according to CERN, stronger than the vacuum between Earth and the moon. The superconducting electromagnets are chilled to ‑271.3°C to remove the resistance of materials as they pass through.

Another safety feature added were 27,000 new shunts that were placed on 10,200 high-current splices - the superconducting interconnections - that sit between magnets on the LHC. The shunts will provide an alternate pathway for the 11,000-amp current to pass in the event of a fault.

CERN today released a video detailing the unusual conditions of doing maintenance work in the tunnel, which at its lowest point is 180m below the earth's surface and has a narrow path for workers to navigate its circumference. But because access points to the 27km tunnel are 3km apart, engineers would ride bikes between points, which of course meant finding parking space for them too.

New radiation-resistant electronics were installed in the LHC to replace components that suffered wear and tear from radiation caused by previous collisions.

Scientists at CERN are aiming to generate collisions at 13 TeV by the end of May or early June after an initial run at circulating beams of proton in the week beginning 23 March. This follows a trial last Saturday running proton beams through a 10km segment of the ring, marking the first activity since the LHC shutdown.

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