2012 Events Discussion
- Tim Bergel
- Posts: 29
- Joined: Mon Nov 23, 2009 1:31 pm
Re: 2012 Events Discussion
Everything seems to be going very smoothly ... too smoothly ...
Seriously though, is it my imagination or is it taking much less time between the end of one period of stable beams and the start of the next? The turnround only seems to take about two hours - I'm sure it used to take longer.
Seriously though, is it my imagination or is it taking much less time between the end of one period of stable beams and the start of the next? The turnround only seems to take about two hours - I'm sure it used to take longer.
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- Joined: Mon Mar 29, 2010 10:09 pm
- Location: Titusville Florida
Re: 2012 Events Discussion
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This is what last year looked like.- Attachments
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Re: 2012 Events Discussion
2 copies of the same image? or do I need new glasses?
best regards
Dave
best regards
Dave
- DCWhitworth
- LHCPortal Guru
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- Location: Norwich, UK
Re: 2012 Events Discussion
The latest USLHC blog comments on this http://www.quantumdiaries.org/2012/04/1 ... pectations they imply no one seems to know.tomey36 wrote:why is the atlas lumi so much lower than cms?
However the luminosity readings are only estimates I believe. They seem to have tuned the way they estimate them over the break.
DC
The LHC - One ring to rule them all !
The LHC - One ring to rule them all !
- DCWhitworth
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Re: 2012 Events Discussion
I have to say I agree, things seem to be going seriously well. I could be mistaken but I think we've had three consecutive programmed dumps.Tim Bergel wrote:Everything seems to be going very smoothly ... too smoothly ...
Seriously though, is it my imagination or is it taking much less time between the end of one period of stable beams and the start of the next? The turnround only seems to take about two hours - I'm sure it used to take longer.
DC
The LHC - One ring to rule them all !
The LHC - One ring to rule them all !
Re: 2012 Events Discussion
Thanks DCWhitworth. It looks like they are about to do some VDM scans, so maybe we will know more after.
Re: 2012 Events Discussion
There have been more programmed dumps this year so far, not because the machine is better but because the priorities are different. They are trying to increase the intensity back to 1380 bunches. To get there there are a number of milestones to pass and boxes to tick, in order to satisfy the Machine Protection team that it's safe to increase the intensity. Requirements are generally something like [2 hours of Stable Beams with N bunches]. Once this is achieved they can dump and try to tick the next box. There's no point trying to keep collisions going for longer because whatever luminosity they collect now will be negligible compared to what they will get later with a full machine.
Re: 2012 Events Discussion
@adam_jeff, your point is valid but even taking that into account the stability and turn-round times have been exceptionally good compared to last year.
The beams have been dumped at around 50% of peak lumi as they often were in 2011 if they lasted. This is quicker now because the luminosity half-life is getting shorter as luminosity increases. I wonder if they will do some longer runs to get some low pile-up data later.
Looks like they should reach the maximum 1380 bunches before the technical stop and they may even reach 1/fb. They could not have wished for more.
The beams have been dumped at around 50% of peak lumi as they often were in 2011 if they lasted. This is quicker now because the luminosity half-life is getting shorter as luminosity increases. I wonder if they will do some longer runs to get some low pile-up data later.
Looks like they should reach the maximum 1380 bunches before the technical stop and they may even reach 1/fb. They could not have wished for more.
Re: 2012 Events Discussion
If we can trust the CMS lumi, they have delivered 1 fb^-1 in 2012 with the current fill. No doubt the LHC is running very smoothly.
- DCWhitworth
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Re: 2012 Events Discussion
Well since the technical stop everything seems to have gone in the opposite direction, glitches everywhere !Tim Bergel wrote:Everything seems to be going very smoothly ... too smoothly ...
Seriously though, is it my imagination or is it taking much less time between the end of one period of stable beams and the start of the next? The turnround only seems to take about two hours - I'm sure it used to take longer.
DC
The LHC - One ring to rule them all !
The LHC - One ring to rule them all !
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- LHCPortal Guru
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Re: 2012 Events Discussion
Most frustrating Cryo dysfunction. They are having repeated trips of the S 78 cold compressor and are trying to hook that sector up to the S 81 compressor. They are trying to be efficient with the time though fixing and adjusting things in unaffected sectors.
I'm sure the powers that be are asking many questions about what is the fundamental problem with S 78 cold compressor reliability.
I'm sure the powers that be are asking many questions about what is the fundamental problem with S 78 cold compressor reliability.
- chriwi
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Re: 2012 Events Discussion
Looks like they have another record fill this time, ATLAS and CMS each way above 100.000 integrated fill luminoaity @ 13 houres stable beams and not yet the end.
bye
chriwi
chriwi
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- LHCPortal Guru
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Re: 2012 Events Discussion
Things do seem to have settled down and they are putting together back to back productive runs. Over the last four days in ten fills CMS and Atlas have each been provided with about 1/2 Fb-1 of data.
Onward!
https://lhc-statistics.web.cern.ch/LHC-Statistics/
Onward!
https://lhc-statistics.web.cern.ch/LHC-Statistics/
- terryburton
- Posts: 13
- Joined: Thu Mar 11, 2010 11:44 am
Re: 2012 Events Discussion
Onwards indeed... "During the stable beams, the injectors profited to fix the problem of emittance blow-up. The investigation was so proficuous that the SPS started re-measuring low emittances as before the TS and we decided to dump to refill."
The current fill had initial luminosities exceeding 5300 b⁻¹s⁻¹ and 5500 b⁻¹s⁻¹ for ATLAS and CMS, respectively, average of 1.38×10¹¹pb⁻¹, without losses during the ramp and squeeze.
Much admiration and respect to the teams in nearing the conclusion of a long and difficult recovery from the technical stop!
The current fill had initial luminosities exceeding 5300 b⁻¹s⁻¹ and 5500 b⁻¹s⁻¹ for ATLAS and CMS, respectively, average of 1.38×10¹¹pb⁻¹, without losses during the ramp and squeeze.
Much admiration and respect to the teams in nearing the conclusion of a long and difficult recovery from the technical stop!