A rare LHC tour—avoiding radiation to see scientific history up close
CESSY, France—As we drive through small villages in Eastern France, some for the second time, it's becoming increasingly clear that my tour guide is lost. She's got a stack of printed Google Maps, but, without a clear indication of where we actually are, it's tough to tell where in the stack she should be looking.
Eventually, on the other side of a corn field, she spots a building that looks out of place. Someone apparently ripped this structure out of an office park in New Jersey and dropped it into France. Before long, we step onto an elevator and step out into a scene that wouldn't look out of place in a science fiction movie. A building-sized heap of electronics dominates the underground cavern before us, and this contraption has an equally sci-fi-ish name: the Compact Muon Solenoid.
Best known for helping physicist Peter Higgs earn his Nobel Prize for the discovery of the Higgs boson, the CMS is one of two general purpose particle detectors built on the Large Hadron Collider (LHC) at CERN, which extends from Switzerland and into France. Normally when the LHC runs, the chambers housing the detectors experience intense radiation; security systems keep pretty much anyone from entering (and for good reason).
But for the past two years, the building hasn't been used for physics. Instead, physical repairs and improvements to all of the detectors, as well as the LHC itself, were made. A bit over a year ago, while the LHC was shut down and partly disassembled, I was lucky enough to be invited underground to see its massive detectors and walk the vast tunnels housing the particle accelerator itself.
CERN initially targeted March of 2015 for the return of protons to the LHC, but everyone knows the saying about best laid plans. According to Nature, metal debris in a diode box caused the most recent delay. That meant, following a planned two-year hiatus, the team behind LHC needed to fix one final short circuit before a triumphant return. In late March, they sent an electrical discharge through to burn away the problematic metal, and follow-up tests confirmed the fix worked.
Now, the LHC is finally gearing up for its second major scientific run. On the eve of its return, we're bringing you a rare look inside.
CMS
Ohio State University's Carl Vuosalo helped show us around the CMS, but first he had to shepherd us past higher security than I've ever experienced. To do so, he passed through a retina-scanning security system that simultaneously checked his weight (presumably to keep someone with a disembodied eyeball from making their way past the system). I passed it solely because of Vuosalo's ingenuity. He opened a door meant for the delivery of equipment, slipping me through as if I was a UPS shipment.
Even though the LHC was shut down, the team made safety the highest priority. They lectured on protocol; they issued me a hard hat. The greatest risk of death at the LHC, as it turns out, is suffocation. Liquid helium (120 tons of it, along with another 10,000 tons of liquid nitrogen) cool the accelerator hardware, while many parts of the giant detectors rely on liquid argon to track particles through them. Either of those will happily convert to a gas if let loose from their containers. In addition, the fire suppression system could fill the entire chamber the CMS resides in with foam in under a minute.
That says a lot. Despite its name, no one would call the CMS compact. At over 20 meters long and 15 meters across, it weighs about 14,000 tonnes—and the chamber itself is considerably larger. That's because the space has to be big enough to allow the detector to enter in pieces. Teams lowered the detector to the site in sections, and the sections were currently slid apart in order to allow workers to service the individual detectors. Despite the immense mass, CMS comes apart by floating on a cushion of air. Tubes allow compressed air to be pushed under the detector's feet, raising it just enough that its main parts can be slid around the chamber. Vuosalo said the noise involved is deafening even several stories above the chamber floor.
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Eventually, on the other side of a corn field, she spots a building that looks out of place. Someone apparently ripped this structure out of an office park in New Jersey and dropped it into France. Before long, we step onto an elevator and step out into a scene that wouldn't look out of place in a science fiction movie. A building-sized heap of electronics dominates the underground cavern before us, and this contraption has an equally sci-fi-ish name: the Compact Muon Solenoid.
Best known for helping physicist Peter Higgs earn his Nobel Prize for the discovery of the Higgs boson, the CMS is one of two general purpose particle detectors built on the Large Hadron Collider (LHC) at CERN, which extends from Switzerland and into France. Normally when the LHC runs, the chambers housing the detectors experience intense radiation; security systems keep pretty much anyone from entering (and for good reason).
But for the past two years, the building hasn't been used for physics. Instead, physical repairs and improvements to all of the detectors, as well as the LHC itself, were made. A bit over a year ago, while the LHC was shut down and partly disassembled, I was lucky enough to be invited underground to see its massive detectors and walk the vast tunnels housing the particle accelerator itself.
CERN initially targeted March of 2015 for the return of protons to the LHC, but everyone knows the saying about best laid plans. According to Nature, metal debris in a diode box caused the most recent delay. That meant, following a planned two-year hiatus, the team behind LHC needed to fix one final short circuit before a triumphant return. In late March, they sent an electrical discharge through to burn away the problematic metal, and follow-up tests confirmed the fix worked.
Now, the LHC is finally gearing up for its second major scientific run. On the eve of its return, we're bringing you a rare look inside.
CMS
Ohio State University's Carl Vuosalo helped show us around the CMS, but first he had to shepherd us past higher security than I've ever experienced. To do so, he passed through a retina-scanning security system that simultaneously checked his weight (presumably to keep someone with a disembodied eyeball from making their way past the system). I passed it solely because of Vuosalo's ingenuity. He opened a door meant for the delivery of equipment, slipping me through as if I was a UPS shipment.
Even though the LHC was shut down, the team made safety the highest priority. They lectured on protocol; they issued me a hard hat. The greatest risk of death at the LHC, as it turns out, is suffocation. Liquid helium (120 tons of it, along with another 10,000 tons of liquid nitrogen) cool the accelerator hardware, while many parts of the giant detectors rely on liquid argon to track particles through them. Either of those will happily convert to a gas if let loose from their containers. In addition, the fire suppression system could fill the entire chamber the CMS resides in with foam in under a minute.
That says a lot. Despite its name, no one would call the CMS compact. At over 20 meters long and 15 meters across, it weighs about 14,000 tonnes—and the chamber itself is considerably larger. That's because the space has to be big enough to allow the detector to enter in pieces. Teams lowered the detector to the site in sections, and the sections were currently slid apart in order to allow workers to service the individual detectors. Despite the immense mass, CMS comes apart by floating on a cushion of air. Tubes allow compressed air to be pushed under the detector's feet, raising it just enough that its main parts can be slid around the chamber. Vuosalo said the noise involved is deafening even several stories above the chamber floor.
Read More
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