Power Management DesignLine Europe - 9 Sep 08

Prof. Robert B. Laughlin
Department of Physics
Stanford University, Stanford, CA 94305

(Copied 8 Aug 09)

Fingers Crossed

Preparing for a Big Bang

By Paul Buckley
September 9, 2008

On Wednesday 10 September the world of physics is going to be holding its breath and turn its gaze towards Europe.

And so will I.

That is the day the first attempt to circulate a beam in CERN's Large Hadron Collider, LHC, will be made at the injection energy of 0.45 tera-electronvolts.

Physicists will be holding their breath to see whether the LHC is going to be able to recreate the conditions just after the Big Bang, by colliding the two beams of protons head-on at very high energy. Teams of physicists from around the world will analyse the particles created in the collisions using special detectors in a number of experiments that have been designed to help us determine how our universe works.

I will be holding my breath on behalf of CERN's engineering team as they try to manage the power and energy aspects of the LHC project. If they fail then the whole project will instantly be the laughing stock of the world.

The LHC project is almost a win-win event for the physicists. If the results match the main theory predictions they should be well on the way to resolving many of the mysteries of how the universe was formed and evolved. And even if the results prove (as is quite likely) inconclusive it means that the physicists and mathematicians can scratch their heads and carry on once again trying to postulate some more theories.

So what could go wrong? Well quite a lot actually. And the one thing that could really leave everyone at CERN with egg on their face is if the big switch on simply fails to switch on.

Everything about the LHC tends to be on a grand scale.

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. Housed in a 27-kilometre tunnel, the LHC is essentially a giant prototype. And we all know how reliable prototypes can be.

Starting up the LHC is not as simple as flipping a switch. The commissioning process has proved to be a long-winded exercise that starts with the cooling down of each of the machine's eight sectors. This is followed by the electrical testing of the 1600 superconducting magnets and their individual powering to nominal operating current. These steps are followed by the powering together of all the circuits of each sector, and then of the eight independent sectors in unison in order to operate as a single machine.

A single failure anywhere in the power management planning and an awful lot of scientists could be left twiddling their thumbs for several months.

At full power, trillions of protons will race around the LHC accelerator ring 11 245 times a second, travelling at 99.99% the speed of light. Two beams of protons will each travel at a maximum energy of 7 TeV, corresponding to head-to-head collisions of 14 TeV. The result should see about 600 million collisions take place every second. The total energy in each beam at maximum energy is about 350 MJ, which is equivalent to the French TGV train, travelling at 150 km/h. It is enough energy to melt around 500 kg of copper. The total energy stored in the LHC magnets is some 30 times higher (11 GJ).

Around 120 MW of power (230 MW for all CERN) will be needed to drive the project. That is about the power consumption for households in the Canton (State) of Geneva in Switzerland. The estimated yearly energy consumption of the LHC in 2009 is about 800 000 MWh. That figure covers the site base load and the experiments.

The estimated total yearly cost for running the LHC is about 19 million Euros. CERN is supplied mainly by the French company EDF. It will be interesting to see what the real cost actually is. Estimated running costs from energy suppliers seem to be rather unreliable these days. Just look at your own utility bills.

A large proportion of the LHC power consumption is not used up by the accelerator itself but is required to keep the superconducting magnet system at the operating temperatures (1.8 and 4.2 K). Effectively, most of the energy is used to power the cooling systems in what is arguably the largest refrigerator system ever created.

So fingers crossed for all concerned. But most of all for those power engineers at CERN.

They might need it.