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I was under the impression that the tunnel must remain locked for access while at Cyro conditions but I see repeated Access discussions in the log. Exactly how close can they get to the cold machine? Do they use suits?

I thought that it took weeks before they could enter sector 3-4 after the malfunction last year which is why I based access was not possible.

Can someone set me straight?

Thankx again all for all the help!
J

The cold is kept almost completely inside the machine structure its my understanding. Lots of insulation. So I think its quite safe to touch the outside of the magnets. I would imagine they might not even feel cold.

Radiation is a danger when the machine is running. So no access when the beam is on. This is thier main focus i think..

Also its more dangerous when its filled with cryo fluid because if a leak occurred its a confined space. So i think they keep access to a minimum for safely reasons as well.

AFAIK..

teh problen last year was that when the bad joint failed it opened the cryo pipes to the tunnel and flooded the are with huge amounts of He. till all the He was vented/removed the tunnels were not enterable

The magnet enclosures are basically big thermos bottles with the space inside at a vacuum to minimize heat transfer. There are also a few thin layers of reflective foil insulation to block IR radiation. Though I imagine it is rather cool down in the tunnels on a winters day.

As mentioned the greatest danger is from asphyxiation should a massive He leak displace the air in the tunnel.
They have very strict rules about access and have Patrols to ensure no one is left behind.

http://accelconf.web.cern.ch/AccelConf/ ... upc129.pdf