Large Hadron Collider Gets “Open Heart Surgery”

The massive physics experiment in Switzerland is receiving an upgrade

Pixel Tracker
The innards of the Large Hadron Collider's CMS module Max Brice/CERN

The Large Hadron Collider has been smashing atoms together for almost a decade now, and making some incredible discoveries in the process. Now, a major upgrade of one of its detectors combined with a recent boost in the collider's power promises to make the world's largest machine even better at unlocking the sub-atomic secrets of the universe.

Yesterday, according to Paul Rincon at the BBC, engineers at the collider swapped out a large component known as a “pixel tracker” in the Compact Muon Solenoid (CMS), one of the major experiments along the LHC’s oval. The complexity and delicate nature of this procedure makes it comparable to performing open-heart surgery on the massive scientific instrument, which straddles the border between Switzerland and France, Rincon reports.

The collider uses 1,200 magnets to guide two beams of particles moving at almost the speed of light around the 16-mile-long oval. Researchers then cross those beams, resulting in high-energy collisions that sometimes reveal new types of particles. Discoveries made at the LHC include the vaunted Higgs boson as well as other exotic particles including pentaquarks and antiquarks. Along the particle beam's route are four major detectors, including CMS, that pick up signals from different types of particles created by the collisions.

The need to upgrade CMS comes from a recent upgrade of the supercollider itself. In 2015, after two years of rejiggering, the LHC began operating at 14 teravolts, almost twice the energy of the 8 teravolts it operated at during its first few years. Running at the lower energy level, the CMS detector could image the paths of 25 or 30 charged particles at a time by taking roughly 40 million images per second, recording them as a superimposed pictures that had to be disentangled.

The higher-power collisions will produce twice as many particle paths, meaning the CMS needs to capture even more data. The new pixel tracker will allow the CMS to do that. “It’s like substituting a 66 megapixel camera with a 124 megapixel camera,” Austin Ball, technical co-ordinator for the CMS, tells Rincon. “There are limits to the camera analogy—it’s a 3D imaging system. But the point is that the new system is more powerful at disentangling the effects of having multiple collisions superimposed on top of each other.”

Yesterday, the team finished putting the new pixel tracker in place. But that’s just the first step. They need to test it and make sure it is operating correctly before the LHC turns on again on May 1. “It’s like launch date for a satellite,” Ball tells Ryan F. Mandebaum at Gizmodo. “The last few months have been exciting, because we’ve been under quite a lot of time pressure. Today, to find it installed and fitting around the beampipe correctly, this is an important culminating day.”

Then again, the incredibly complex LHC is known for its delays. It didn't even begin operating until more than two years after its initial launch date. Since then, issues including short circuitsmultiple suicidal weasels and a baguette-carrying bird have led to many smaller shutdowns and delays.

According to a press release from CERN, the European Organization for Nuclear Research which operates the LHC, the new device will eventually be replaced by a third-generation pixel tracker when the LHC undergoes another major upgrade, around 2020.

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