2008-08-23

The first particles have been injected into the biggest atom smasher on the planet, marking the start of the countdown to probing the secrets of the universe.

Scientists are pushing ahead with powering up the machine, shrugging off speculative fears that it could destroy all life on Earth by sucking it into a black hole.

Starting up the biggest scientific experiment ever built is not as simple as flipping a switch.

Earlier this month, the successful injection of the first particles - protons - into part of the Large Hadron Collider (LHC) experiment at CERN, the European Centre for Nuclear Research, took place.

This weekend, scientists are hoping to complete testing of another part of the machine, which sits in a 17 mile circular tunnel approximately 100 metres underneath the Franco-Swiss border, with the aim of seeing particles travel the whole way around for the first time.

As such preparations for the formal September 10th start date continue, the entire machine has been successfully cooled to temperatures below minus 270ºC, a fraction of a degree above the lowest achievable temperature.
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In this temperature range, helium becomes a liquid, and is used to cool the superconducting magnets which keep the proton beams circulating at almost the speed of light as well as making the LHC the biggest refrigerator on the planet.

The LHC is the world's most powerful particle accelerator, producing beams seven times more energetic than any previous machine, and around 30 times more intense when it reaches design performance, probably by 2010.

The protons injected into the giant machine are obtained by removing electrons from hydrogen gas and are then accelerated in bunches.

For the tests, the proton bunches were first accelerated by the Super Proton Synchrotron (SPS), a smaller 4.3 mile ring, before injection (like a lane merging onto a motorway) into the LHC, which has to be timed to the nanosecond to work.

Once the individual detectors around the LHC are ready (the "eyes" that study the effects of collisions between particles), further injection tests will attempt to ensure two counter-rotating proton beams circulate throughout the machine.

Capturing the remnants of high energy collisions between these beams will then become possible, setting the stage for the LHC to potentially rewrite the laws of physics as we know them.

Tests will continue into September to ensure that the entire machine is ready to accelerate and collide beams at an energy of 5 TeV per beam, the target energy for the end of 2008 - this is equivalent to each particle having the energy of a flying mosquito squeezed into a space a million million times smaller.

Withstanding any major setbacks, the LHC will see its first circulating beam on 10 September at the injection energy of 450 GeV (0.45 TeV). Once stable circulating beams have been established, they will be brought into collision, and the final step will be to commission the LHC's acceleration system to boost the energy to 5 TeV, taking particle physics research to a new frontier.

'We're finishing a marathon with a sprint,' said LHC project leader Lyn Evans. 'It's been a long haul, and we're all eager to get the LHC research programme underway.'

One aim of the machine is to improve current theory about the forces that bind together the particles in every atom. Known as the Standard Model, this is one of the triumphs of 20th-century science and fits in with the results of all experiments ever done on sub-atomic particles.

Key to that will be to find a crucial ingredient, the Higgs particle, whose existence goes some way to explain why atoms contain particles that have weight.

Others hope that a menagerie of new particles will be seen when the LHC is switched on - and perhaps some of them will help account for the "dark matter" that astronomers cannot see, although they can detect its existence via the gravitational forces it exerts on other particles.

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