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Posts Tagged ‘schedule’

Read-Set-Go: The LHC 2012 Schedule

Thursday, September 20th, 2012

From Now Until Mid-December, Expect One Thing from the LHC: More Collisions.

Figure 1: Integrated luminosity for LHC Experiments versus time. 8 TeV proton-proton collisions began in April 2012. Credit: CERN

 

Hi All,

Quick post today. That plot above represents the amount of 8 TeV data collected by the LHC experiments. As of this month, the ATLAS and CMS detector experiments have each collected 15 fb-1 of data. A single fb-1 (pronounced: inverse femto-barn) is equivalent to 70 trillion proton-proton collisions. In other words, ATLAS and CMS have each observed 1,050,000,000,000,000 proton-proton collisions. That is 1.05 thousand-trillion, or 1.05×1015.

To understand how gargantuan a number this is, consider that it took the LHC’s predecessor, the Tevatron, 24 years to deliver 12 fb-1 of proton-antiproton collisions*. The LHC has collected this much data in five months. Furthermore,  proton-proton collisions will officially continue until at least December 16th, at which time CERN will shut off the collider for the holiday season. Near the beginning of the calendar year, we can expect the LHC to collide lead ions for a while before the long, two-year shut down. During this time, the LHC magnets will be upgraded in order to allow protons to run at 13 or 14 TeV, and the detector experiments will get some much-needed tender loving care maintenance and upgrades.

To estimate how much more data we might get before the New Year, let’s assume that the LHC will deliver 0.150 fb-1 per day from now until December 16th. I consider this to be a conservative estimation, but I refer you to the LHC’s Performance and Statistics page. I also assume that the experiments operate at 100% efficiency (not so conservative but good enough). Running 7 days a week puts us at a little over 1 fb-1 per week. According to the LHC schedule, there about about 10 more weeks of running (12 weeks until Dec. 16 minus 2 weeks for “machine development”).

By this estimation, both ATLAS and CMS will have at least 25 fb-1 of data each before shut down!

25 fb-1 translates to 1.75 thousand-trillion proton-proton collisions, more than four times as much 8 TeV data used to discover the Higgs boson in July**.

Fellow QDer Ken Bloom has a terrific breakdown of what all this extra data means for studying physics. Up-to-the-minute updates about the LHC’s performance are available via the LHC Programme Coordinate Page, @LHCstatus, and @LHCmode. There are no on-going collisions at the moment because the LHC is currently under a technical stop/beam recommissioning/machine development/scrubbing, but things will be back to normal next week.

 

Happy Colliding

– richard (@bravelittlemuon)

 

* 10 fb-1 were recorded each by CDF and DZero, but to be fair, it also took Fermilab about 100 million protons to make 20 or so antiprotons.

** The Higgs boson discovery used 5 fb-1 of 7 TeV data and 5.5 fb-1 of 8 TeV data

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This morning, the LHC ended proton-proton collisions for 2010. What an exciting year! Seven months ago, there had never been particle collisions at a center of mass energy of 7 TeV in an accelerator. Now, LHC physicists are busy combing through the mountains of data that have been accumulated since. True, the collisions are still a factor of two below design energy, and a factor of a hundred below design collision rate — we have a long way to go. However, the improvements we have seen this year have been very encouraging and show that we are well on our way to getting there. We have seen the instantaneous collision rate (luminosity, really, for those who want the right techical term) increase by a factor of 100,000 over the past seven months. As a result, the bulk of the collision data has actually arrived within the past month. Everyone has had to be on their toes to keep up with it.

Today thus marks the end of at least one era. With the heavy-ion run about to start and then an extended technical stop to begin in early December, we don’t expect proton collisions again until late February 2011. This break of at least three months gives everyone a chance to chew on the data that we do have in hand. This dataset is thus going to be the basis for a raft of papers that are going to be published in 2011. At the very least, this data will be used to re-establish a variety of standard-model processes at this energy scale, and will be able to exclude a number of theories of new phenomena. (Or, if we are very lucky, discover some new phenomena!) On top of that is another intriguing possibility: it is possible (but certainly not yet confirmed!) that in 2011 the LHC will run at a collision energy of 8 TeV rather than 7 TeV. This decision will likely be made at the Chamonix workshop in January, where CERN will set the run plan for the year. A move to 8 TeV will increase the production rate of a variety of particles, including the much-sought Higgs boson (if such a thing actually exists). If this happens, then it is likely that 7 TeV collisions will never be done again, in which case the data we have collected this year, and the measurements done with them, will be something unique in the history of particle physics.

Your LHC physicists will be hard at work over the next few months to fully explore the 2010 data. Watch this space for more news about the science that will come out of it!

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This past Monday we had our annual US CMS Tier-2 computing workshop. Once again, we held our workshop as part of the Open Science Grid All-Hands Meeting. Those of you who have been reading the blog for more than a year will remember that last year this meeting was held at the totally neat LIGO facility in Louisiana. This year the meeting was at totally neat…Fermilab! OK, I’ve been to Fermilab before, so no travelogue this time, but as usual it was good to meet so many collaborators face to face.

I don’t want to jinx ourselves, but I’m feeling pretty good about the state of the computing for the experiment right now. As we reviewed the status of the seven CMS Tier-2 sites in the United States and two in Brazil, we generally saw that everyone is operating pretty stably and happily. A year ago, there was a lot of discontent with existing large-scale disk storage systems. But since then we’ve developed and implemented some new systems, and there have been a lot of improvements in the existing systems, so it all just looks a lot better.

That being said, this all just dress rehearsal — we’ll see how it really goes when thousands of physicists start using the system to do hundreds of data analyses. Now that the LHC running schedule has been defined for the coming three years, we have a much better handle on the needed computing resources for for this period. Overall, we’re going to be running at lower collision rates than previously anticipated, but with pretty much the same livetime. This means that we’ll be recording the same number of events we would have at higher collision rates, implying that the density of interesting physics will be smaller. It creates a more challenging situation for the computing, but at least we now know what has to be done, and have a reasonably good idea of how to get there.

As for the second half of the title — the real excitement was on my trip home. I had an 8:10 AM flight out of O’Hare, which would arrive in Lincoln around 9:40, giving me plenty of time to be ready for my 12:30 PM class. But there was fog in Chicago, and an aircraft was late, and then the crew was swapped, and then the aircraft was sent to Peoria instead while we waited for the crew, and in the end we didn’t leave until around 10:45. The plane touched down on the runway in Lincoln at 11:57. And I was in my classroom just on time. Ah, lovely Lincoln, where the airport is small, you park right next to the airport, and you can drive to campus in minutes!

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Sunny Sunday

Sunday, October 25th, 2009

This weekend the weather has been playing tricks on me in New York. I intended to go camping upstate with some friends, but after a valiant attempt on Friday evening/Saturday morning, we decided to take our soggy sleeping bags and head back to Long Island. It literally rained all day, night and the next morning – which being from Colorado – I’ll never get used to. I decided to share this with you on a Sunday afternoon sitting in my apartment looking out my window at this:

A room with a view

A room with a view

The gods must be conspiring against me to make sure I get work done this weekend :).  So I thought I’d update everyone as to the status of the LHC. My email’s been a buzz with information. So far all the repairs have been completed and the entire ring is back at the operating temperature of 1.9 K. The schedule is still on to start circulating beams in mid November with low energy collisions soon to follow. Although we probably won’t be at the full energy this year, any collisions would be an amazing milestone.

There’s also a new LHC First physics Physics Website that you will probably want to check out. It will have the most up-to-date information. Happy reading on a beautiful Sunday!

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Realism and the LHC

Wednesday, August 12th, 2009

Maybe I have a bit of a contrarian streak, but some of my fellow bloggers’ exhortation to “try to be optimistic” rubs me the wrong way.  I absolutely agree with them that some recent news coverage of LHC delays has been unduly pessimistic and misleading, and I am as excited as ever about both the short- and long-term prospects for the LHC, but I think I would rather try to be realistic.  Fortunately, the two positions aren’t that different: realism still gives us mostly good news.

Of course, there is an underlying optimism in being a particle physicist: the basic assumption — perhaps belief, or hope — that the physical universe can be described by equations and laws, so that the physics we know already can point us to the physics we have yet to discover.  That idea has proven true since the days when physics was a branch of “natural philosophy,” and been very constructive indeed, and that line of reasoning tells us that the LHC is a place where great discoveries will very probably be made.  So that much optimism I’m happy to grant; it’s what I’m building my entire career on.  No high-energy particle physicist has changed his or her mind about the importance of the LHC.  Of all the ATLAS graduate students I know, only one has switched away from the ATLAS to work at the Tevatron — and that’s not based on a lack of confidence or interest in the LHC, but simply a bet that he can write a thesis and get back to the LHC in time to catch most of the exciting stuff.

It’s pure realism that refutes some of the implied doubts about the long-term stability of the LHC project.  Repairs on the machine are done except for a few tweaks, and it will be running very soon.  There are a lot of important measurements to be made at our initial run goal of “only” half energy — which, don’t forget, is more than triple the energy of any previous particle physics experiment.  It is significantly less likely, though by no means impossible, that new particles will be discovered at lower energy; but getting to the LHC’s design energy, or very close to it, is only a matter of time and effort.  And, realistically again, time and effort are things that the LHC has in abundance: CERN’s core funding and personnel are guarenteed by international treaty, and contributions to the LHC and its experiments are guaranteed by almost-equally ironclad agreements between universities and funding agencies worldwide.

I think the main difference between realism and optimism is on what we can expect in the next few months.  The start-up plan calls for the LHC to begin running in November, which happens to be exactly when I’m moving back to Berkeley.  I would love to be here at CERN, working in the trenches, as things start up — so why on earth am I doing that?  There are three reasons.  The first is practical; my group wants to keep graduate students in both Berkeley and Geneva, and a bunch of younger students are about to move out.  That means that I could stay a little longer, but not too much — so I’d have to believe that we were going to start in November and get very prompt collisions if I were going to try to stay for them.  Second, although I have no complaints about any schedule or plan produced for the LHC this year, they have all been provisional from a realistic perspective.  There’s a very good reason for this: you can say how long things will take if everything goes according to plan, but it’s very hard to guess what extra work or delays might crop up with a one-of-a-kind machine.  So I’m “betting” on a little bit more unscheduled delay, although I don’t expect it to be very long in the grand scheme of things.  (Of course, I’m not an expert on the work on the LHC or how it’s going; I’m just guessing, and making the best decision I can based on that.)  Third, it will take some time to proceed from the first running of the LHC to high-energy collisions.  How long?  Again, nobody quite knows, it’s never been done before.  But I do know that the folks who run the LHC plan to be cautious and take things step-by-step; we experimentalists waiting for collisions, no matter how eager we are, obviously support this.  So an optimist might not move back in November, but I am.  I’ll come back out for a month in the Spring once I have a better idea how things are going.

Of course, realistically, I could be wrong.

Facebook folks: I’m Seth, http://blogs.uslhc.us/?author=9

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LHC Chief Steve Myers gave a very interesting talk on the LHC Status today to a packed auditorium here at CERN.  The slides and video can be found here: http://indico.cern.ch/conferenceDisplay.py?confId=62277

Here is a brief summary of what I took to be the most important lessons from the talk (although of course you’ll learn more from going back to the original):

  • The LHC schedule has been delayed by about three weeks from what was forseen in February.  That’s routine schedule slippage and no big deal as far as I’m concerned; if there are no other major issues than we will certainly be running this Fall.
  • The limiting factor in when and how the LHC starts are the measurements of the resistances of the welding between copper busbars at the connection between magnets, which only carry current when the superconducting wire isn’t superconducting.  Some of them have resistances that are too high, and if one of these is affected during a quench, then both the copper and the superconducting wire can melt and cause a current arc. This is what happened last September, and was part of the chain of events that caused significant damage to the LHC.  There are other busbars with resistances that are too high, and the highest one in the LHC will limit the total current in the magnets and therefore the accelerator energy.
  • So far about half the resistances in the accelerator have been fully checked.  The rest are planned to be checked by early August, and if there are no significantly higher resistances are found than those seen so far, the LHC will probably be able to do an initial run with energy of about 4 TeV.
  • Once all these resistances have been measured, and in particular if higher values are found, the LHC experts will have to decide what the highest safe machine energy is.  Then CERN, the LHC, and the experiments can decide together if it is better to run at that energy or wait longer in order to repair the worst resistances.
  • There have been significant upgrades to a variety of systems for preventing and reducing large-scale problems caused by future current arcs or other damage to the helium cryostats in the LHC magnets, although of course the goal is to avoid these in the future.
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Into the woods, for one year

Wednesday, February 11th, 2009

My apologies to all you loyal readers and our even more loyal editors for not posting as often as might like to (or at least ought to).  I am busy teaching a large lecture course for the first time, and it is keeping me rather busy.  I’m certainly enjoying the topic of this course (electromagnetism), and am thankful for all the technology tools that we have to manage classes with large numbers of students (all homework assignments and exams are done online).  But it still takes a lot of time.  Our first midterm exam is at the end of this week.  “Are you nervous?” I asked at the start of class today.  All the students said yes, and I told them that I was nervous too.  An exam is an accountability moment for all involved; if they don’t do well, I should shoulder some of the blame.

As I work my way through the material to prepare my classes, I am struck by how much we are asking the students to learn in one semester.  If you haven’t seen any of this before, it must be quite daunting.  Now, I’ve known about this stuff for twenty years, so I can easily see the big picture, but it is harder for someone who is new to it.  Just last weekend, I was at a party, and was chatting with a friend who teaches in our Modern Languages department and some of her colleagues.  When it came out that I’m in physics, one of them noted that physics was hard for her when she took it.  “It’s not that hard!” I said.  “You just have to remember that there are really only a few concepts in play, and the rest of it is applications.”  This is totally true — electromagnetism, for instance, comes down to four basic physical laws — but of course she didn’t believe me.  It is hard to see the forest for the trees.

When the LHC turns on, there are going to be quite a lot of trees, of course, and it is going to take us a while before we figure out what the forest looks like.  When it comes to LHC physics, we’re all going to be new students who haven’t seen any of it before.  That is rather bracing, of course, but it’s also going to be a lot of fun!

While writing, I ought to comment on some other current events:

  • I think that the announced plan for LHC running is good news.  These experiments need to start accumulating some data so that we can figure out how the detectors work and how to reconstruct what is going on in them, and by planning for a long data run (into Autumn 2010), CERN is intending to give us just that.  Nothing like data to make you smarter.
  • Other bloggers here have expressed concern about the stimulus plan currently under consideration in the Congress.  I agree; I worry that it is not big enough and not fast enough.  Science projects can easily absorb and make good use of the funding that has been proposed and is now at risk.  Let’s not forget that all money goes to people eventually.  Spending on science doesn’t go into a hole in the ground (not even a hole like the LHC!); it pays people to do stuff, and those people spend their money in the economy, and so forth.  I’ve been a bit dismayed to see that a certain Senator from a certain state has been less than helpful on this front.  I called his office; it hasn’t seemed to have gotten me anywhere.
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Welcome, Dr. Heuer

Saturday, January 3rd, 2009

Now that 2009 has begun, CERN has a new management team and a new Director General, Rolf-Dieter Heuer. Dr. Heuer is a former spokesperson for the OPAL collaboration at CERN and was most recently the Research Director for particle and astroparticle physics at the DESY in Hamburg, Germany.  While working on my talks for next week’s giant annual LBNL ATLAS group meeting in Berkeley, I ran across his first message to the CERN community.  This is my favorite part:

Our top priority for this year is providing data to the LHC experiments. After the spectacular success of the LHC’s first beam, and the bitter disappointment of the malfunction barely nine days later, we have emerged stronger. As an outsider, but also a former CERN staff member, it was most gratifying to see that the Organization and its staff has lost none of its determination, none of its creativity and none of its pragmatism. It is remarkable how quickly our engineers have got to grips with the problem, and given us a roadmap to restart. We now understand what went wrong, and we know how to fix it. The timetable for repairs published at the end of 2008 is an aggressive one, and we’ll do our best to keep to it. However, if the work takes longer to accomplish, we will not rush. I will be keeping you all up to date with progress on a regular basis as we go through to the restart and physics later this year.

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Schedule Disappointments

Wednesday, November 19th, 2008

As Adam noted yesterday, the date now being cited by the CERN Press Office for the restart of the LHC is early summer.  Unfortunately, there are two reasons why I’m personally not inclined to take this new estimate too seriously.

First, CERN has an increasingly long history of being over-optimistic on LHC start-up times.  At one time it was scheduled to run in 2005. Even into 2007, the official schedule said there would be a low-energy run that year; but in the end, it didn’t start running until almost a year later.  After the accident on September 19, CERN initially announced that the incident would lead to minor delays, then that it would take several months because of the winter shutdown, and now we have the revision that the repairs will push into the summer. Obviously some of these delays were due to unforeseen circumstances, for example the recent accident itself.  But even if all the schedule changes are due to equally-unforeseeable (if less dramatic) issues, the sheer number of revisions seems to suggest that CERN ought to take a step back and consider how it does contingency planning and the certainty with which it expresses its scheduling announcements.

Second, this new announcement is not accompanied by a new detailed schedule.  What would be useful for the experiments is more information about the damage and a full discussion of how the repairs will proceed, along with a range of possible start times depending on how well still-unknown factors turn out; this would let us do better contingency planning for our own maintenance work, not to mention our careers.  It’s very possible that CERN doesn’t yet have all the information about what repairs will be necessary, but then why the new announcement?  What use can it have beyond publicity, and what meaning can anyone possibly extract from it?

I should be clear here what I mean when I talk about “CERN” making announcements.  Obviously I’m not talking about the technicians, engineers, and physicists who work on the LHC; I’m sure they’re doing a great job, and of course they don’t write the press releases or talk to the media.  I’m also not referring to anyone in particular in the CERN Press Office or Management; the Press Office does a lot of good work on outreach, including putting forth an extraordinary effort for First Circulation Day, and the folks who write the press releases aren’t necessarily the ones who decide what they say.  The truth is that I simply don’t know how decisions about these announcements are made, or who makes them.  But somehow the official system for disseminating information is falling short of providing what the physicists working here need or what the public deserves.

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You may ask why one would speak about an upgrade while everyone is still in “acute anticipation” for the first few particles to make it around the machine? Perhaps there are even skeptics who doubt that we may never be able to circulate particles in this giant hole. I was recently browsing through the “LHC the guide” and stumbled upon one of the fascinating facts which may cool down that skepticism. Apparently, during that major tunnel digging, the two ends of the 27-km circular tunnel met up to within 1 cm!

Ok, that said, and if you believe in the “as soon as possible” version of the beam schedule, it is estimated that focusing magnets closest to the interaction point will reach the end of their lifetime circa 2013-14 (or before) due to radiation damage from collision debris. Instead of replacing exact replicas, why not do better. And why not, since these magnets do have the largest impact on the holy grail called luminosity.

So, discussions about the LHC upgrade began a decade ago which is now being coordinated under the CARE-HHH network, you can find all sorts of stuff here: http://care-hhh.web.cern.ch/CARE%2DHHH/default.html
After several workshops debating about what seemed like infinite new ideas, it now boils down to two contenders (both democrats, I think). Ask me in a couple of years and the priorities maybe completely different, physics and/or management. The U.S. folk under the LARP program (https://dms.uslarp.org/) have been very busy on the upgrade program since the beginning. Now more than ever, about 100 physicists from U.S. labs (this is lot for accelerator physics) are working very hard to get those particles circulating and yes, do even better next time around. It is perhaps a bit ironic, since the beginning of the biggest accelerator may also mean the demise of some other smaller siblings – sort of “survival of the fittest”. To be cont’d…

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