Weekend of 12-3-09 collision events !

The place to discuss the LHC. Commissioning, operation, issues, events ....
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Xymox
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Re: *** COLLISION ALERT ***

Post by Xymox » Sat Dec 05, 2009 4:46 pm

Told you ! They are sneaky !

The CMS page is good. They have some guys who staff it live when events happen. ALWAYS watch that page.

Im just waking up.. Glad I havn''t missed too much...

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Texanguy
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Re: *** COLLISION ALERT ***

Post by Texanguy » Sat Dec 05, 2009 4:47 pm

Well, good mornin', stranger. ._.

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aperture_science
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Re: *** COLLISION ALERT ***

Post by aperture_science » Sat Dec 05, 2009 4:50 pm

Just before the collisions post at CMS (13:10h), the LHC OP log reads

"Adjusted beam separations for colliding beams in all IRs." (Dec 5 12:51h)
"Finished with reference orbit. CMS and ATLAS see triggers." (Dec 5 13:06h)

Later on, the log talks about collimator studies.. what are those?
♪ This was a triumph ♪

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Re: *** COLLISION ALERT ***

Post by LHC_Insider » Sat Dec 05, 2009 4:55 pm

Xymox wrote:Told you ! They are sneaky !
I never know quite how public the schedule is, so I just chuckle to myself with pessimistic (as compared to the actual schedule which is publicised twice daily internally) suggested dates people come up with :)

Lots going on, as said, hoping for a decent physics run tonight... Lots of us are preparing for a long night analysing this data. I've got the coffee machine on.

Collimators are movable devices which essentially scrape the edge of the beams to keep them in good shape, and stop stray particles going of any doing things such as inducing quenches in the magnets. As a movable, computer controlled device, their positions and behaviors need to be understood. By monitoring beam losses during controlled moving of the collimators, it is possible to work out exactly where they are in relation to where the control software says they are. Note that this is only possible due to the very impressive beam stability the machine people have achieved.

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Re: *** COLLISION ALERT ***

Post by Danny252 » Sat Dec 05, 2009 5:08 pm

Hmm, I'm doubting any collisions have taken place. The LHC OP eLogBook mentions nothing about collisions - and the timetable for today's collisions has been moved back to 2000 (2 hours time).

Edit: Well the pictures on CMS's blog seem to be fairly conclusive in saying they did collide... oh CERN, why do you have to confuse us so?!

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Re: *** COLLISION ALERT ***

Post by Xymox » Sat Dec 05, 2009 5:17 pm

Yes I must point out the absolute importance of watching Dave Barney's CMS page. They are awesome at keeping it updated almost real time. They do a awesome job. He was one of the very first people I had email with at CERN. The page auto updates.

If you have more then one computer, get it set up so you can watch more then one thing at once. JUST like they do in the control rooms..

physics run
That is a important term you used there... This would be the first one right ?

**BIG milestone** The first physics run. As important as the first collisions and the first beam..


Danny, the CMS guys are awesome at coverage, the LHC logs can lag behind.. Dave Barney does a really good job of posting things as close to live as CERN will allow..

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aperture_science
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Re: *** COLLISION ALERT ***

Post by aperture_science » Sat Dec 05, 2009 5:26 pm

I thought those two terse log entries I quoted above were indicative of impending collisions - and that it was up to the guys and girls at CMS to write it up with a little more excitement in their voices :D

Thanks for the explanation of the collimators!
♪ This was a triumph ♪

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Xymox
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Re: *** COLLISION ALERT ***

Post by Xymox » Sat Dec 05, 2009 5:36 pm

YES....

He has a VERY good point...

You gotta watch for the terms he quotes from the comments on page 1.... The Page 1 stuff will be first of course...

The problem is that stuff can disappear with a new update and you can miss it..

We need a log of the history of the comments section on page 1 !

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Re: *** COLLISION ALERT ***

Post by Xymox » Sat Dec 05, 2009 5:43 pm

I want to point out to everybody how important "Science run" is...

It looks like for the first time the whole process of doing science is going to proceed like it would during full operations. This is a big deal... We are just focused on the operation of the machine,,, there is a MUCH bigger goal of course,,, science. This must have a whole proceedure where the physicists get the data, analyze it and post results..

This process is just as important, detailed and complex as running the LHC. Its also a whole separate process that I know little about as its kinda secret. I have no idea how it works, does some software suddenly report data to be analyzed ? Then how is the work of analyzing the data broken down to each person ? For each Experiment ?

For me the entire theoretical physics division's involvement and procedures is a complete mystery to me..

It sounds like this process is going to get tested in this run...

THATS a important milestone..

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Re: *** COLLISION ALERT ***

Post by LHC_Insider » Sat Dec 05, 2009 5:50 pm

Xymox wrote:This process is just as important, detailed and complex as running the LHC. Its also a whole separate process that I know little about as its kinda secret.
It's not secret at all. What is secret are the results until they are approved by the collaboration (you don't want Mr. Scientist no. 1 making a mistake, publishing something that later needs to be retracted).

I will post some details of how analysis proceeds later. But, do note that all the mechanisms have been used for some time now; this is just now with real collision data.

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Re: *** COLLISION ALERT ***

Post by Lexa » Sat Dec 05, 2009 5:57 pm

2 years ago I worked on integrating the validation process of atlas paper (and maybe used for other exp now) into the cern library.
It's quite... complex, and long. Involving multiple boards, and reviewing possible from any guy in the collaboration +2000 persons for the biggest :P).

Otherwise, for what they are going to do this WE, it is rather callibration of detectors than breakthrough physic analysis.
Last edited by Lexa on Sat Dec 05, 2009 6:51 pm, edited 1 time in total.

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Re: *** COLLISION ALERT ***

Post by mihtjel » Sat Dec 05, 2009 6:29 pm

The ALICE eLog has a plausible answer:

"13:00: Message on LHC page, "Colliding beams in all points, ramping ALICE solenoid" - no supporting phonecall. Run restarted. Confirmation over telephone finds that actually circulating beam from both sides but not stable and no collisions."

So it seems the trigger for collisions was a mistake?

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Re: *** COLLISION ALERT ***

Post by Xymox » Sat Dec 05, 2009 6:40 pm

Hmm............ Interesting.... No collisions ? hmmm....

Lexa, LHC_Insider... Yes we need info on the process if its not too much trouble. Start a topic in Science on it. It would be good for the public to fully understand this process. Its the next phase as we go from commissioning to real science and I would like to understand it before we get to it.

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Re: *** COLLISION ALERT ***

Post by Texanguy » Sat Dec 05, 2009 7:07 pm

On Page 1....
"Circuits in S12 Tripped... Investigating"
"No beam for a while"
hmm.

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Re: *** COLLISION ALERT ***

Post by Xymox » Sat Dec 05, 2009 7:11 pm

GOOD ! I can take a break ! Im sure thats what they are thinking too !

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