At least 60 times more powerful than its predecessors, the laser at the National Ignition Facility (NIF) in California is an impressive?feat of precision engineering. It contains the largest optical instrument ever built, 7,500 ash-lamps, 97 kilometres (60 miles) of mirrors and fibre optics, and is roughly the size of three football pitches. At the master oscillator of the NIF, a low-energy pulse of photons is generated using an optical fibre laser. To?amplify the laser pulse it is broken down into 192 separate beams;?these are then carried through fibre-optic cables to a series of amplifiers. Powerful white ash-lamps are used to energize sheets of neodymium-impregnated phosphate glass, which energizes electrons in the neodymium atoms. As the photons pass through the amplifier they cause the electrons to drop back to their ‘ground state’, and in the process more photons are released. The photons collide and vibrate together, creating a stream of photons all of the same wavelength and traveling in a single direction.?An optical switch in the amplifier works like a mirror and forces the photons to travel back and forth, bumping in to more electrons and producing more and more identical photons. This process boosts the power of each beam from a fraction of a joule to over 20,000 joules. Once the beams have been amplified, two ten-storey mirrored ‘switchyards’ focus them into a spherical target chamber, pinpointing a target smaller than a pencil eraser. The combined power of all 192 beams heats the target to 100 million degrees Celsius (180 million degrees Fahrenheit) – more than six times hotter than the core of the Sun – and puts it under a force exceeding 100 billion atmospheres, all in less than a second.
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At least 60 times more powerful than its predecessors, the laser at the National Ignition Facility (NIF) in California is an impressive?feat of precision engineering. It contains the largest optical instrument ever built, 7,500 ash-lamps, 97 kilometres (60 miles) of mirrors and fibre optics, and is roughly the size of three football pitches. At the master oscillator of the NIF, a low-energy pulse of photons is generated using an optical fibre laser. To?amplify the laser pulse it is broken down into 192 separate beams;?these are then carried through fibre-optic cables to a series of amplifiers. Powerful white ash-lamps are used to energize sheets of neodymium-impregnated phosphate glass, which energizes electrons in the neodymium atoms. As the photons pass through the amplifier they cause the electrons to drop back to their ‘ground state’, and in the process more photons are released. The photons collide and vibrate together, creating a stream of photons all of the same wavelength and traveling in a single direction.?An optical switch in the amplifier works like a mirror and forces the photons to travel back and forth, bumping in to more electrons and producing more and more identical photons. This process boosts the power of each beam from a fraction of a joule to over 20,000 joules. Once the beams have been amplified, two ten-storey mirrored ‘switchyards’ focus them into a spherical target chamber, pinpointing a target smaller than a pencil eraser. The combined power of all 192 beams heats the target to 100 million degrees Celsius (180 million degrees Fahrenheit) – more than six times hotter than the core of the Sun – and puts it under a force exceeding 100 billion atmospheres, all in less than a second.