2017 Operation

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dukwon
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Location: Geneva

Re: 2017 Operation

Post by dukwon » Mon Jun 26, 2017 10:56 am

2460b is not the maximum. We have seen 2820b already this year, albeit for scrubbing, and I believe the intensity ramp will end at 2556b (due to BCMS?).

Today's morning meeting slides are mostly about the losses at 16L2.

If you want daily summaries, hang around in the IRC channel.

jmc2000
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Re: 2017 Operation

Post by jmc2000 » Mon Jun 26, 2017 11:44 pm

https://indico.cern.ch/event/632309/con ... faroli.pdf
Page 19 gave a few possible 2017 scenarios with 2448b + BCMS giving higher luminosities compared to standard 2736b.

We're at a luminosity of around 1.4/nb/s so would I be right in believing they haven't tried BCMS yet this year?

jmc

sciing
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Re: 2017 Operation

Post by sciing » Tue Jun 27, 2017 10:08 am

jmc2000 wrote: We're at a luminosity of around 1.4/nb/s so would I be right in believing they haven't tried BCMS yet this year?
No, it looks clearly like BCMS.
Emi is around 2.3 like BCMS
Lumi is up to 1.55, which could not be achieved with 2460 bunches, if not BCMS.
I guess the difference to calculation is due higher crossing angle at start, calculation is for 150µrad, but they start now at 240µrad to lower pile up and decrease to 140µrad after lumi has gone down.

dukwon
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Location: Geneva

Re: 2017 Operation

Post by dukwon » Tue Jun 27, 2017 10:52 am

jmc2000 wrote:https://indico.cern.ch/event/632309/con ... faroli.pdf
Page 19 gave a few possible 2017 scenarios with 2448b + BCMS giving higher luminosities compared to standard 2736b.
It should be noted that the figure of 2448 is the number colliding in IPs 1 and 5. This corresponds to the current filling scheme (as of fill 5877 at least) with 2460b

jmc2000
Posts: 137
Joined: Sun May 08, 2011 2:51 pm

Re: 2017 Operation

Post by jmc2000 » Tue Jun 27, 2017 6:19 pm

sciing wrote: No, it looks clearly like BCMS.Emi is around 2.3 like BCMS
Lumi is up to 1.55, which could not be achieved with 2460 bunches, if not BCMS.
I guess the difference to calculation is due higher crossing angle at start, calculation is for 150µrad, but they start now at 240µrad to lower pile up and decrease to 140µrad after lumi has gone down.
Interesting, so even if they manage to get beta=0.33 this year, the increase in pile up will make the increase in luminosity pointless.

Jmc2000

mfb
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Joined: Sat Oct 03, 2015 7:58 pm

Re: 2017 Operation

Post by mfb » Tue Jun 27, 2017 11:50 pm

It is always nice to have higher luminosities later in the run. Ideally the luminosity would be a constant value all the time, where the constant depends on the experiment.

The morning meeting slides suggest 2556 bunches starting tomorrow. The first MD/TS block is coming up soon.

4.5/fb collected by ATLAS/CMS, exceeding the 2015 dataset already.

sciing
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Re: 2017 Operation

Post by sciing » Wed Jun 28, 2017 5:21 am

CMS reported over 700/pb delivered for yesterday.

mfb
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Re: 2017 Operation

Post by mfb » Wed Jun 28, 2017 7:31 pm

Physics with 2556 bunches.
A nice machine availability, ~150% the design luminosity at the start of runs and the crossing angle reduction later lead to a fast luminosity collection - as fast as in the best weeks in 2016.

The first Machine Development block will start Friday 9 am.

jmc2000
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Re: 2017 Operation

Post by jmc2000 » Tue Jul 04, 2017 1:05 am

Does anyone know how the MDs went, and if a lower beta is a possibility?

jmc2000

mfb
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Re: 2017 Operation

Post by mfb » Tue Jul 04, 2017 3:25 pm

They did some measurements at beta* = 35 cm and 25 cm, but I don't know if that is planned for later this year.

neocortex
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Re: 2017 Operation

Post by neocortex » Wed Jul 05, 2017 3:01 am

For the ATS optics MD they were able to use the telescopic part of the squeeze to get beta* to 25 cm. The optics was measured and corrected at 35 and 30 cm with crossing and separation bumps on. You might be surprised to learn they've actually pushed beta* down to 15 cm using this optics a few years ago during a MD, but they can't use beta* any lower than 30 cm during physics operation due to the available space in the aperture. Pushing beta* in the MD was mostly about gaining experience controlling and correcting the telescopic part of the optics for HL-LHC.
Before the telescopic squeeze can be used in this year's physics run they need to find collisions, realign the collimators on either side of ATLAS and CMS, and verify the aperture with loss maps. My guess is this will be done during another MD period.
BCMS beams have been used since the start of the intensity ramp-up, and they can mitigate the pileup at beta* of 30 cm using separation levelling.

mfb
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Re: 2017 Operation

Post by mfb » Thu Jul 20, 2017 7:00 pm

Recovery from the technical stop took quite some time due to various issues from the RF cavities and other parts of the machine, but we are back to stable beams with 2556 bunches. Currently at a slightly lower intensity per bunch as a few runs were dumped from high losses in one region of the accelerator. Currently 6 hours in stable beams, 0.27/fb collected, the luminosity is now crossing the design luminosity (initially it was 1.5 times this value). That's how it should look like.

jmc2000
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Joined: Sun May 08, 2011 2:51 pm

Re: 2017 Operation

Post by jmc2000 » Thu Jul 20, 2017 8:53 pm

At one point they managed a new instantaneous luminosity record of 1.65\nb/s, but dumped an hour later because of losses. 1.7\nb/s is the aim this year for beta = 40cm, 1.9\nb/s for beta = 33cm.

JMc

mfb
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Re: 2017 Operation

Post by mfb » Fri Jul 21, 2017 6:09 pm

More than 2.11 would be an absolute luminosity record, surpassing the KEKB record from 2009. As far as I know it would be the first time ever a proton-proton machine has the absolute luminosity record. It would be a stretch, but maybe they can make it possible. 2018 SuperKEKB will surpass this record and quickly go beyond even the HL-LHC values, so it is a unique chance.

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