2011 Events Discussion

The place to discuss the LHC. Commissioning, operation, issues, events ....
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Kasuha
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Re: 2011 Events Discussion

Post by Kasuha » Sun Apr 17, 2011 6:17 pm

Isn't LHC breaking its own records for a while already? I believe we'll see a few more of them till it reaches design parameters, but I don't think every step is a big deal anymore...
My personal opinion is that putting over 1000 bunches in the ring during the scrubbing period was much better achievement.

lap
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Re: 2011 Events Discussion

Post by lap » Sun Apr 17, 2011 7:12 pm

tomey36 wrote:I could be wrong but i am pretty sure the LHC just broke the world record in luminosty.
Not yet, Tevatron luminosity WR is 402.4/ub/s (http://tomato.fnal.gov/ops/records.php)

tomey36
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Re: 2011 Events Discussion

Post by tomey36 » Sun Apr 17, 2011 7:47 pm

I wasn't talking just about the LHC breaking its own records, but i belive firmilab's maximum luminosty is 3.5 e32 which the LHC broke yesterday.

zaim
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Re: 2011 Events Discussion

Post by zaim » Sun Apr 17, 2011 8:30 pm

You can see the Tevatron records here http://www-bd.fnal.gov/pplot/today/Data ... ables.html.

The luminosity record at the Tevatron is 402.4 (ub.s)^-1, so the LHC is not quit there yet, but in a couple of days, it will surpass its American counterpart.

A record it did take however, was integrated luminosity per fill. Today Atlas recorded more than 10 pb^-1 while the record at the Tevatron is 9.8 pb^-1 in one fill.

cheers Zaim

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DCWhitworth
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Re: 2011 Events Discussion

Post by DCWhitworth » Sun Apr 17, 2011 11:41 pm

Oh dear. Looks like there's been some sort of 'incident'. Cryo lost and several quenched magnets. Anyone got more info ?
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drsnooker
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Re: 2011 Events Discussion

Post by drsnooker » Mon Apr 18, 2011 1:48 am

Recovering from B2 injection kicker flashover which happened during 72 bunch injection. Vacuum OK.
NEXT beam some time in the morning.

josch222
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Re: 2011 Events Discussion

Post by josch222 » Mon Apr 18, 2011 7:06 am

There was a flash over at an injection kicker magnet during injection.
36 bunches impacted on injection collimators and absorbers, probably the resulting
high radiation triggered the quench heaters in 9 dipoles and 2 quadrupoles and
closing of some vacuum valves.
88% of total intensity where dumped, the rest went somewhere else.
LHCbs BCMs saw readings factor 100 higher than ever.
So far there seems to be no real damage.

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DCWhitworth
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Re: 2011 Events Discussion

Post by DCWhitworth » Mon Apr 18, 2011 7:32 am

Looks like something went badly wrong with the injection but the machine protection systems worked OK. I guess they need to work out why now and stop it happening again.

From the LHC Logbook -

"MKI D (1st one seen by the beam) had a real flashover between the two sets of 36b during the 3rd 72b injection.

The result was the second 36b of the 72b train hitting the TDI with between 75 and maybe 90% of the nominal MKI deflection...as the beam was missing some kick it looks like the breakdown was in the first half of the magnet and has maybe produced a true grazing case, already spectacular with 36b.

If we believe the TD BCT we dumped about 88% of the expected beam, which means nearly all the p+ in this 36b impacted the TDI/TCLIB.

The big injection oscillations for the 2nd set of 36b are clearly visible in IQC (+/-5mm), as is the vertical offset and reduced intensity on BTVDD in XPOC.

Kicker vacuum showed some degradation with the injections before the bad one - to be checked if this is normal or if it's a precursor of the problem.!
DC

The LHC - One ring to rule them all !

josch222
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Re: 2011 Events Discussion

Post by josch222 » Mon Apr 18, 2011 10:17 am

What I don't understand:
They are preparing for injection right now.
If there was a flashover at the kicker magnet there should have been some insulation
problem before the spark and even more after it. Electrical arcs don't tend to improve
insulation.
How did they fix this in just a few hours?

But may be the flashover was not in or at the magnet itself but in the driving circuit,
which may be easy to replace.

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DCWhitworth
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Re: 2011 Events Discussion

Post by DCWhitworth » Mon Apr 18, 2011 10:47 am

From the morning meeting "Beam after kicker flash-over has been fully analyzed.
For the moment it seems that protection, collimation and MP reaction was OK (designed for this)."

I don't know what the state of the injection equipment is but they must be confident it's a one off or that it's been resolved.

Looks like there were at least 9 genuine magnet quenches, I think this is the biggest incident they've had since they restarted the LHC in 2009. Nice to see all the protection equipment worked as expected.
DC

The LHC - One ring to rule them all !

josch222
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Re: 2011 Events Discussion

Post by josch222 » Tue Apr 19, 2011 9:36 am

According to the slides from the daily meeting this morning,
they plan "no beam from 16:00 - 19:00+ for VIP visit" tomorrow.

Does anybody know who will visit?

Must be really important, possibly some politician involved in funding.

pcatom
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Re: 2011 Events Discussion

Post by pcatom » Tue Apr 19, 2011 7:29 pm

Jose Barroso, President of the European Commission.

tomey36
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Re: 2011 Events Discussion

Post by tomey36 » Thu Apr 21, 2011 12:05 am

i noticed that the atlas background #2 which is usuly in the thousands dropped down to the 20's does any one have any more information on this?

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DCWhitworth
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Re: 2011 Events Discussion

Post by DCWhitworth » Thu Apr 21, 2011 7:31 am

Heads up, next fill 480 bunches. New luminosity world record likely coming up.
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DCWhitworth
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Re: 2011 Events Discussion

Post by DCWhitworth » Thu Apr 21, 2011 9:59 am

Very close. Was over 400 (ub.s)^-1 certainly, not sure if they quite got the world record. Thought they'd make it easily but they only squeezed to 2m not 1.5m
DC

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