LHC Shutdown schedule

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Glacialis
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Re: LHC Shutdown schedule

Post by Glacialis » Wed Dec 16, 2009 9:53 pm

Sorry to double post. The Register (IT geeks should know the site) has an article on it. My favorite phrase "ultra-violent hadron billiards".

http://www.theregister.co.uk/2009/12/16 ... _shutdown/

Oh yeah...

LHCPORTAL.COM IS MENTIONED IN THE ARTICLE!
(at the bottom)

^^^
This is a big deal to me because El Reg is a big site, and that means more popularity for this place.

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DCWhitworth
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Re: LHC Shutdown schedule

Post by DCWhitworth » Wed Dec 16, 2009 10:51 pm

LHCPortal has been mentioned on THe Register several times before :)
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Glacialis
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Re: LHC Shutdown schedule

Post by Glacialis » Thu Dec 17, 2009 1:16 am

Well I'm new here, so bah! :lol: I love the Register, brightens my day with just the right amount of snark.

Harbles
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Re: LHC Shutdown schedule

Post by Harbles » Thu Dec 17, 2009 3:03 am

Well I guess this http://hcc.web.cern.ch/hcc/file/cmm.png answers my earlier question about Cryo maintain over xmas.

josch222
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Re: LHC Shutdown schedule

Post by josch222 » Thu Dec 17, 2009 8:58 am

Harbles wrote:Well I guess this http://hcc.web.cern.ch/hcc/file/cmm.png answers my earlier question about Cryo maintain over xmas.
Take a look at http://lhc.web.cern.ch/lhc/Cooldown_status.htm.
It seems that they let most of the LSS-magnets warmup, for some reason.
Some of the Arc-magnets going up too, it looks like they chosse exactly the ones
with the false temperature sensor readings plus some of their neighbours.
I suppose they are grouped to the liquid helium supply so they can only
warm up the whole group to get access to a single one.
All the other ones seems to stay at cryo at the moment.

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DCWhitworth
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Re: LHC Shutdown schedule

Post by DCWhitworth » Thu Dec 17, 2009 10:08 am

I'm not convinced the temperature readings were incorrect. The warmer magnets seem to be the LSS magnets which stands for Long Straight Section so I guess these are less important.
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josch222
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Re: LHC Shutdown schedule

Post by josch222 » Thu Dec 17, 2009 12:53 pm

DCWhitworth wrote:I'm not convinced the temperature readings were incorrect. The warmer magnets seem to be the LSS magnets which stands for Long Straight Section so I guess these are less important.
All the LSS temperatures in operational state have been between 4-6K, as far as I
remeber. Now some of them are rising, don't know why, but surely because they
want to do some work on them.

The arc temperatures have been below 1.9K, except some that read 7K, 10K, 14K or 20K.
There was one in sector 3-4 that reads below 1.9K (I think it was 1K). At least the
latter one was clearly defective IMHO, because boiling liquid Helium at a controlled pressure would not allow that temperature.
Given the fact that now that groups of arc magnets including the temp. readings outliers are allowed to warm up (except the one in sector 1-2) leads me to the speculation that they want to fix the sensors.

An argument that individual sensor readings are less important:
If you have groups of strongly thermally coupled magnets, because they share the
same LHe supply at the same pressure, you don't have to rely on a single
sensor. You get somewhat redundancy, avoiding the single point of failure
that otherwise a defective sensor would introduce.

But maybe I speculate too much, lets call a piquet or an expert ;-)

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DCWhitworth
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Re: LHC Shutdown schedule

Post by DCWhitworth » Thu Dec 17, 2009 1:46 pm

Well the whole LHC seems to be warming up I think most likely because they've turned the power off to the cryogenics.
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josch222
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Re: LHC Shutdown schedule

Post by josch222 » Thu Dec 17, 2009 2:08 pm

DCWhitworth wrote:Well the whole LHC seems to be warming up I think most likely because they've turned the power off to the cryogenics.
Oh yes, now I see, but that wasn't the case a few hours ago, then I saw only the
mentioned "groups" and LSSs going up. I thougt they would keep the cryo for the others.

I wonder what they do with all the Helium, either thy keep it liquid and cool or they
need a really large storage volume and high pressure.
Another interesting question comes to mind: Are there any problems with
pumping superfluids?


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chriwi
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Re: LHC Shutdown schedule

Post by chriwi » Thu Dec 17, 2009 2:32 pm

Anyone knows what the scedule for the cryogenics is? Will they switch it off completely leave it warm up und still have enough time to cool it down again before Feb 20th or will they kepp the temperature at some lets say "standby level" for example at the temp of liquid nitrogen (at least in an old document I read there was a 75k-standby-mode available)?

@Joined: They don't really have to pump the superfluid helium at least not at this point, because it will go back to normal-fluid-state as it warms above 3k. Besides I am not sure if there are any special problems in pumping supefluid, the main problem of superfluids is when they are in an open environment not when they are in fully filles pipes and containers.
bye

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DCWhitworth
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Re: LHC Shutdown schedule

Post by DCWhitworth » Thu Dec 17, 2009 2:41 pm

I see LHCb now says "Merry Xmas !" on the Ops page :)
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Harbles
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Re: LHC Shutdown schedule

Post by Harbles » Thu Dec 17, 2009 3:17 pm

I'm going to guess that they will allow sectors with no work scheduled to warm to 4.5 k so they can turn off the 1.8 k compressors, some sectors warm to 70 k for testing and some to warm right up if they need work. I hope it's not many because it will take at least 3 wks to cool down again.
You can laugh at me if I'm way wrong.

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Re: LHC Shutdown schedule

Post by chriwi » Thu Dec 17, 2009 3:26 pm

Hi harbels,

I am also guessing things like that, but I am looking for someone who finds some documents aubout this tipic or one of the insiders who can really tell us.
bye

chriwi

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Re: LHC Shutdown schedule

Post by Harbles » Sat Dec 19, 2009 11:46 pm

CERN has installed Helium storage tanks that can hold a fraction of the total amount in the LHC system. So I would assume that is a major factor in managing energy hence most sectors will stay at 4.5 K and act as helium storage.
I have been looking for a log note or any other info on the Xmas break plan for Cryo but no joy so far.
However this CERN News video from Oct. featuring the very charming Paola Catapano on the Cryo system is helpful.
http://www.youtube.com/cern#p/a/AB4B2AB ... 4J1Rck22U8

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DCWhitworth
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Re: LHC Shutdown schedule

Post by DCWhitworth » Sun Dec 20, 2009 12:07 am

I've noticed tha the cryo temperatures seem to have risen after shutdown but then stabilised. Seems it's still on just not at quite such a low temperature.
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