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Visit to CERN

Posted: Tue Jun 17, 2014 12:39 pm
by jsmaje
Some of you will have visited CERN near Geneva before, but I’ve recently come back from my first time.
The 27-kilometer-circumference LHC (Large Hadron Collider, of recent Higgs boson fame) happens to be off-line at the moment while they double the proton-proton beam collision energy to a huge 13-14 TeV, so the Sci-Am-arranged tour group I was with (led by one of the CERN scientists) was allowed down into the 300-ft-underground tunnel to see one of the four main sub-atomic particle detector machines, the CMS: ‘Compact Muon superconducting Solenoid’ experiment.

If in the picture below I might look a bit underwhelmed, it’s because I was in fact overwhelmed, indeed totally humbled and somewhat tearful. And the photo doesn’t do justice to the cathedral-like cavern, hugeness and complexity of the machine.

ATLAS (on the opposite side of the LHC ring, in Switzerland) is dimensionally bigger, but the CMS (in France) is the heaviest at 40,000 tons of the four collision-point experiments, has the largest magnet of its type ever constructed producing a field 100,000 times that of earth, and registers the counter-rotating proton-proton near-light-speed collision products at the rate of 40 million times per second!
We also visited the cryogenics engineering facility which enables the magnets to superconduct 20,000 amps at just 1.9 degrees Kelvin above absolute zero, half the temperature of outer space.

And yes, there is a customs post between Switzerland & France at ground-level half way across the LHC ring. It happened to be unmanned that day since it was some Saints festival! How weird, I thought, that official territorial suspicion could be briefly suspended due to medieval religious superstition, all amidst the most non-territorial/religious of institutions in the world.

What I found reassuringly ordinary-world was that each of the 400 million tiny hi-tech components within the various detector layers you see all around the central collision point (presently split in half, the other half being off-photo to the right) are actually connected by domestic-sized insulated wires, albeit thousands & thousands of them bunched into thousands of cables that connect to the multiple banks of computers and control rooms on the levels above that we were ushered through, where they are simply plugged into the relevant ports, just the same as your desktop PC. I’m not surprised it apparently took 3 years for the technicians to make the correct connections and test them all.

Access to the underground LHC tunnel and experiment machines will NOT be possible once it comes back on-line next Spring, and my personal view is that the free public exhibitions at CERN are unlikely to teach you anything more than a regular read of the latest Scientific American, New Scientist or whichever science magazine.
But at least (weather-depending) you could enjoy, as we did, the view toward the Jura mountains to the north and snow-capped Alps including Mont Blanc to the south.

As they emphasise, the extraordinary engineering for CERN, especially in cryogenics, superconductivity, vacuum, microelectronics and civil engineering, gives companies experience that they can apply elsewhere for practical applications such as medical diagnosis and treatment.
All in all, an unforgettable combination of the beauty and wonder of Nature and our best attempts to understand it.



Re: Visit to CERN

Posted: Wed Jun 18, 2014 5:26 am
by caprarom
Interesting report, John. Thanks for sharing your experience with us. Mike C.

Re: Visit to CERN

Posted: Mon Aug 08, 2016 4:47 am
by Eric Romano
That's a very interesting experience you've shared. Switzerland is known for science as well and I've read about the CERN super collider as I was doing some research for my descriptive essay back in college.
The Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator. It first started up on 10 September 2008, and remains the latest addition to CERN’s accelerator complex. The LHC consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way.

Inside the accelerator, two high-energy particle beams travel at close to the speed of light before they are made to collide. The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets. The electromagnets are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy. This requires chilling the magnets to ‑271.3°C – a temperature colder than outer space. For this reason, much of the accelerator is connected to a distribution system of liquid helium, which cools the magnets, as well as to other supply services.

Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator. These include 1232 dipole magnets 15 metres in length which bend the beams, and 392 quadrupole magnets, each 5–7 metres long, which focus the beams. Just prior to collision, another type of magnet is used to "squeeze" the particles closer together to increase the chances of collisions. The particles are so tiny that the task of making them collide is akin to firing two needles 10 kilometres apart with such precision that they meet halfway.

Re: Visit to CERN

Posted: Sun Aug 14, 2016 10:52 am
by jsmaje
Eric – it's good to know that you share my interest in the LHC, and I'd be interested to read your essay; but how do I find it on that ‘studymode’ site?

As well as the many large aspects of the project, both engineering and scientific-wise, I was equally struck when visiting by how small some of the most vital components actually are.
First, that single lonely red bottle of compressed hydrogen gas, apparently sufficient to provide enough protons (hydrogen nuclei) to collide 600 million times per second for at least 4 months:


Second, the modest diameter (~ 6 cm) of the two proton beam pipes - visible with the cream-colored caps in the middle of this display section of the LHC tube, the rest being the all the electrical, vacuum, cryogenic etc. services you mention:


It’s a truly amazing place, but as I said, an underground visit may well not be possible just at the moment.

Re: Visit to CERN

Posted: Wed Aug 17, 2016 12:17 pm
by DanZ
I'm very envious!!