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Mercredi, 09 Février 2011 15:34

Video: Vacuum Tubes Implode in the Name of Physics

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To design stronger vacuum tubes for a proposed high-stakes physics experiment, researchers first need to understand their weaknesses — so they blew up the devices in an old torpedo test chamber.

The destructive tests, seen in the video above, support the development of a planned $1 billion experiment to detect neutrinos, particles that are forged in the heart of stars. Despite being as numerous as photons of light in the universe, they are virtually undetectable — it takes a lifetime of trillions passing through your body each second for just one to interact with a cell.

The ghostly particles are thought to play crucial roles in everything from triggering supernovas to the evolution of the cosmos.

“Neutrinos could be responsible for why the universe is made out of matter and not antimatter. Basically, for why we exist,” said particle physicist Milind Diwan of Brookhaven National Laboratory. “We are planning to build a gigantic underground detector to understand a key property that may have caused an imbalance in favor of matter.”

That property is how neutrinos morph into one of three “flavors” over long distances, and the detector proposed to study it is called the Long Baseline Neutrino Experiment.

Video: Vacuum Tubes Implode in the Name of Physics The project involves two major facilities. Fermilab near Chicago would shoot the world’s most intense neutrino beam toward an abandoned South Dakota mine about 800 miles away. There, two 37-million-gallon water tanks lined with up to 50,000 basketball-sized photomultiplier tubes would catch light emitted when neutrinos hit water.

Data collected should reveal how neutrinos morph over long distances — but one overlooked manufacturing defect, improper installation or accident could implode a photomultiplier under pressure and set off a chain reaction of destruction. A single faulty tube in a Japanese neutrino detector, for example, destroyed close to 7,000 of its 11,000 photomultipliers in 2001.

”Each LBNE tank’s photomultiplier array may cost roughly $100 million, so you have to make sure one flaw won’t take down everything with it,” Diwan said.

To understand the dynamics of photomultiplier tube destruction in an environment similar to the proposed tanks, Diwan and five colleagues at Brookhaven found a mothballed Navy torpedo testing chamber in Rhode Island. The researchers filled up the 50-foot-wide, 500,000-gallon sphere and imploded the tubes while filming the action with high-speed cameras.

The team is currently building a computer model with data from the tests, but they ultimately hope to expose a full array of tubes to punishing shockwaves at the Navy facility.

“We know the shockwave’s intensity and how it spreads, but we don’t know if it will take out other tubes,” Diwan told Wired.com. “We still have a ways to go.”

The LBNE project is only in planning stages and not fully approved by the Department of Energy. But Diwan hopes construction of the colossal device will begin sometime in 2015 and be online by 2022.

Video: Three different underwater implosion tests courtesy of Brookhaven National Laboratory. 1) A 3,800-frames-per-second sequence of a lightbulb imploding in a 60-gallon pressurized water tank. 2) A photomultiplier tube imploding in the same 60-gallon tank at 6,000 fps (a nail-like device at the bottom right triggers the tube’s collapse). 3) A tube implodes within the Navy’s 17-year-old torpedo test bed called the Propulsion Noise Test System at 6,000 fps.

Image: Photomultiplier vacuum tube./Brookhaven National Laboratory.

Via Brookhaven bits & bytes.

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