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CMS e-commentary for 2009 LHC Beams |
CMS e-commentators
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CMS e-commentary for 2009 LHC Beams |
CMS e-commentators
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It's official - the 2009 run of the LHC has come to an end at 18:20 today. In fact the CMS magnet started ramping down in the last hour already to prepare for the technical stop. It has been an amazing restart of the machine after the extensive repair work and improved protection system put in place after the incident that occurred in one LHC sector during the 2008 start of the LHC. In just 26 days, the LHC operators have brought up the machine from scratch, stored both beams, collided them at 900 GeV center-of-mass energy, and ramped and collided both beams at 2.36 TeV as well. We have seen the first physics processes coming from the LHC in the many pictures you have seen posted! It has been a long road of design, construction, and commissioning to bring us to this point, and that is why you see much enthusiasm being reported here from members of the CMS collaboration. The LHC is here!
We now enter a short technical stop to complete the commissioning of the LHC protection system. This will allow the machine to ramp safely each beam to 3.5 TeV (7 TeV collision energy in total), well beyond what any accelerator has achieved, and will mark the start of a physics program in a completely new energy regime. The restart is foreseen to take place in February next year.
During this time, the CMS experiment also enters a period of maintenance. We need to open up the experiment in order to improve the reliability of the cooling system for the endcaps. A very special thanks goes to the physicists, engineers, and technicians that must work over the holidays and throughout January in order to ensure the success of CMS for physics in 2010.
LHC operators have ramped both beams to an energy 1.18 TeV again. Now they "squeeze" the beams (reduce their transverse profile) by focusing the beams with magnets. This increases the luminosity (which is inversely proportional to "beta*") when the beams pass through each other. The steps achieved are in the Page 1 displays above. Trigger rate started from below 2 Hz and increased to around 3 Hz as beta* decreased from about 11m to 9m and then to 7m.
Another event from Monday morning's run at 2.36TeV. This time it is a nice candidate dimuon event. Also a nice photograph taken at the CCC to celebrate the collisions in CMS.
LHC made three successful 16 + 16 fills of the machine last night & this morning.
LHC has just injected 16 proton bunches into each beam, culminating in an intensity of about 1.85*10**11 protons/beam.
As usual our beam and radiation monitoring system (BRM) followed the event perfectly......
and the global run with all detectors included started to see the event rate increase accordingly. Congratulations to all!
Two of the first events from the 2.36 TeV collisions earlier this morning.
Some photos from the control room, courtesy of Richard Breedon. More at http://cms.web.cern.ch/cms/Media/Images/LHCMilestones/2_4TeVCollisions/index.html
LHC made some more ramp tests in the early hours of this morning and managed to achieve their goal: 2 beams each at 1.18 TeV with long lifetimes. During the course of the "quiet beams" period (where the operators did not make further fine adjustments) the whole of CMS was powered and took data for a couple of hours.
After all the excitement in the last weeks, we are operating more or less stably with routine proton fills and the steady accumulation of proton collisions. While not quite boring on shift, it is at least a lot calmer, with fewer people in the control room.
Tonight's central shift is an all-female crew. Beams and data-taking have been remarkably stable. Coincidence?
Beams were in the LHC from about 6pm to 11pm, and then again sinceabout 2am. Expecting beam operations throughout the weekend.
The LHC operators have succeeded in injecting more protons into the machine (7E10 protons in total for one beam), which allows the experiments to collect data with higher collision rates (about 6 times higher). The "Page 1" display from LHC shows the intensities from the second fill this morning.
LHC just accelerated two counter-rotating beams to 1.18 TeV per beam (corresponding to 2kA in the dipoles).
The proton store is in and declared stable for physics. Collision rate is approximately 2 Hz.
LHC injected two beams of 4 bunches each, 2 colliding in CMS. Total proton intensity of each bunch is about 5E9.
Candidate collision from the long morning fill that produced two jets. The transverse energy of each jet is of the order of 20 GeV.
Kudos to Darin for staying at P5 until 11am this morning - a 24-hour stint! Having a well-earned rest now. Plan for the rest of the day is more fills, more collisions and more physics. Looks like it is going to be a busy and eventful CMS Week at CERN!
After a nearly 4 hour fill, beams were lost (of course they were dumped in the correct place, not simply lost into the ether!). General plan is that we may expect more fills until tomorrow morning.
This is from the first colliding store. Candidate muon in the forward CSC muon system seen in the two views.
LHC plans to keep this for a few hours. 4 on 4 again.
Another 4x4 fill is in and colliding with an estimated minbias rate of 1Hz. BRM display above.
Transverse view of the tracks in yellow. ECAL hits are in red Zoomed in on the right plot.
Events seen with tracks in the silicon systems! Everyone very excited and rewarded after a sleepless night.
Lifetime of this store looks good! Keeping beams stable. Ramping voltage on sensitive detectors. Pixels up.
Some difficulty before with 4x4. RF problem. Now trying again with 4 on 4 bunches. Beam lifetime of beam 2 rather low.
LHC informs us that we go for 4-on-4 bunches with collisions next.
The LHC "debunched" the beams, meaning that the protons were allowed to spread out (the RF was turned off, but beams still circulating). This means that the intensity in any specific location becomes too small to measure, and you see that in the bottom plot shown for the 2 beams. But the beam activity is still seen in the scintillators around the beam pipe, as shown in the upper plot.
LHC achieved 4 bunches in both beams. Dumped properly as shown by the 4 beam spots painted onto the dump. Plot taken from LHC logbook.
Despite the hour, SMS messages are sent out (and received as shown here) to gather the experts in preparation for the first physics fills of the LHC.
LHC has injected 4 proton bunches into beam 1. You can see the bunch counter increase to 4 from the beam pipe RF pickups.
Two beams back in the LHC, appear that they may be colliding. Original program of providing several fills of protons for collisions is still to be maintained.
It has been a waiting game for a few hours, and looks like we have to wait still more. We have not yet started the overnight collision running. LHC is investigating sector 1-2.
LHC is currently colliding. Beam intensities are about 3.5E9 protons/bunch. The minbias trigger rate is of the order 0.3 Hz at CMS. This a tuning period, preparing for a relatively long time of running overnight with collisions.
LHC operators successfully injected protons into two separate bunches for one beam tonight. This is the first time to have multi-bunch beams. You can see the proton intensity double in the plot above. Soon one can expect both beams to have multiple bunches. The ultimate design of the LHC will actually call for over 2800 bunches in the beam, but that is far down the road. But for this weekend, we might see 4 bunches on 4 bunches.
DA rejoins DB, after having stuffed himself with turkey in the U.S. last week :-)
For those of you curious about what has been going on recently, the LHC folks have been performing aperture scans. This means steering the beams and probing the effective clearance window along the beam line. This can lead to significant proton losses along the ring, and so sensitive detectors must be kept off. The good news is that we have quite good clearance, and specifically for the region of CMS (point 5).
CMS is in stable operation, preparing for the weekend events.
Beam circulation, collisions at 900 GeV, ramping to a new World Record energy, and more!
The amazing startup of the LHC last night, achieving circulation of both beams!
The story of the beam shots two weeks ago.
The story of last year's start-up.
