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Archive for June, 2008

Amsterberne

Monday, June 16th, 2008

As most of you are by now hopefully aware, Euro2008 (the European soccer championship for country teams) is currently taking place in Austria and Switzerland. Just like Monica and Pam I am having substantial problems not getting distracted by this extravaganza. Being Dutch doesn’t help, the Netherlands is performing much better than anyone expected, including the Dutch themselves. This leads to almost surreal celebrations. Let me give you an example:

(more…)

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The Usual Tag Team

Friday, June 13th, 2008

This always seem to happen when I return from trips to the United States. After a week or two of cramming in all the activities I possibly can, and eating all the wonderful (and affordable!) Americanized ethnic food that I miss when I’m in Switzerland, and being exposed to microbes from another continent, I generally return to Geneva both sick and jet lagged. With “only” six hours time difference to get over, rather than the usual nine from California, I think I would have slept fairly normal hours last night—except that I had a terrible headache that made it hard to get to sleep, and an even worse cough that would wake me up 20 minutes later every time I did.

Needless to say, I am not at work today, although I am making meetings for Monday, consulting on code that I wrote that has been passed on to others, and (obviously) blogging. I need rest, but I also need to remind my body when daytime is, or the jet lag will take over beating me up again.

On a completely different note, my friend Joel back in Berkeley has written a guest post on Cosmic Variance about graduate school, teaching, and the Compass Project. The Compass project is a program at UC Berkeley, run by graduate students, “which supports excellence in science education, especially for women and minorities.” I encourage you to go over and take a look, either to read my arguments with him in the comments about how much graduate programs should emphasize teaching or (better still) to learn about Compass. They’re small, new, and could use more support for the good work they’re doing.

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“Good Morning”

Friday, June 13th, 2008

How often do you greet perfect strangers?

I have a great bike ride from Ferney-Voltaire (where I am staying) to CERN: Here’s the route (red line):

My Route from Ferney to CERN

Much of it is on little roads through fields of alfalfa, sunflowers (which are in fact purple when they first flower), poppies, and other plants I cannot identify, just skirting the suburb of Meyrin (I don’t have a camera with me, else I’d post a picture). On my way in I typically come across 5 or 6 random people out walking (usually with the dog) or running, basically just enjoying the nice morning and environs, and each of these people I greet with a “Bon jour” (although my French is terrible) and they return the greeting. That is just how it is done here – quite a departure from the “don’t make eye contact with anyone” standard in the US (at least the urban US), and much more friendly. So usually I’m in a pretty good mood when I get to work.

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Ah Priorities

Friday, June 13th, 2008

My ability to focus this week is essentially non-existent. For starters we just ended a three-week long detector integration run. And second it is the start of the Euro Cup. So basically there is no hope for me.

In one corner, we have Work. In the other corner, Soccer.
Work. Soccer. Work. Soccer.
Soccer. Work. Soccer. Work.
Soccer. Soccer. Work. Soccer.
Soccer. Soccer. Soccer. Soccer.
Work? What work?
Soccer. Soccer. Soccer. Soccer.

In one corner, we just finished the 7th Milestone week (which was actually three weeks). Just like the 5th and 6th milestone weeks, the aim is to combine all the sub-detectors and try to run as if there was beam. We try to push the system as much as we can, try to have fixed all the bugs from the previous integration weeks and try to debug the new problems that have occurred. It is an important milestone.

In the other corner, Spain destroyed Russia in their opening match! Very important.

For you non-soccer fans, in only two weeks the rest of us will all be back to normal again. And I might be able to once again focus.

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99.9%

Thursday, June 12th, 2008

The ATLAS Liquid Argon Calorimeter has 183,296 separate channels, meaning it makes that many independent measurements of energy simultaneously all around the point where the protons collide in the LHC. It has to be able to reliably make these measurements millions of times per second for many years. Since we are expecting collisions very soon, the detector has now been closed up and we won’t have access to it again until December for any repairs.

Last week here at CERN was a Liquid Argon Week. These are weeks that happen about 4 times per year, and they are when the whole community (hundreds of people) get together to discuss the current status of the Liquid Argon Calorimeter project. There were presentations and discussions of how the calorimeter is working now that it is in the state it will be in for the eagerly awaited first proton-proton collisions.

It has taken a long time to get to this point. According to the article in Nuclear Instruments and Methods A 558 Issue 2, 15 March 2006, p 388:

The first studies of liquid argon calorimetry for LHC date back to 1990…the choice of the liquid argon technology by the ATLAS collaboration for its electromagnetic calorimetry [was made in] in 1995…The fabrication of some of the elements of the calorimeter…started in the beginning of 2000.

In order for the calorimeter to work, everything from design to construction to installation has to go right. The temperature and purity of the liquid argon must be maintained, the front end crates that receive the deposited energy and turn it into digital data cannot fail, the trigger and data-acquisition systems have to get the data to permanent storage, and of course there is plenty of other infrastructure including the high voltage and low voltage power, many custom-designed electronics boards, and cabling between all the systems. Basically, everything from this:

Part of the ATLAS Liquid Argon Calorimeter being installed

to this:

and beyond has to be working correctly.

So last week there was a tallying of “dead” channels; those that didn’t make it through this whole process and probably can’t ever be used. The great news is that more than 99.9% of all the channels are working and ready to find that Higgs boson, or whatever else awaits. This is a pretty impressive achievement!

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Not a cabling exercise

Wednesday, June 11th, 2008

Despite all of our high-minded talk about new physics discoveries, lots of nitty-gritty work has to be done in the trenches. The day to day work of particle physics can typically be characterized either as a cabling exercise (building the detectors) or a bookkeeping exercise (analyzing the data). Since most of the other bloggers are writing about their cabling exercises, I’ll write a bit about a bookkeeping exercise.

The Tier-2 computing site that I help to manage currently hosts about 150 TB of data, in about 200 datasets, which in turn consist of about 135,000 individual files. These files are in turn spread over many different disks in about 20 different storage servers. When someone submits a job to our site, they specify which files they want to analyze. We have to then locate those files and make sure the jobs can actually work on them. Bookkeeping, indeed.

When we copy datasets here from Tier-1 sites, we use a tool that looks up a database of what files exist and where they exist, and then tries to transfer all of those files here.  This transfer tool, called PhEDEx (a name both beautiful and horrible), then records which files are at our site.  It also writes this information into a different record that a tool called DBS can look at.  When users submit jobs, they check against DBS to locate datasets.  So, this means that PhEDEx needs to be in synch with DBS (and vice-versa), or else user jobs will come here and look for data files that we don’t have.  And of course what is actually on the disk needs to be consistent with what PhEDEx thinks we have on disk.

This is what I have been chasing around for the last week or so.  We did some careful checking and discovered that PhEDEx thought we had about 2% more files on disk than we actually had.  That might not sound so terrible, but it is 4 TB, not a small amount.  That we got fixed by telling PhEDEx that we didn’t actually have those files; it then went and re-transferred them for us, without incident.  However, PhEDEx and DBS disagree with each other too, I suspect by an even larger amount.  We’re still trying to figure that one out.

I decided that one way to reduce the number of inconsistencies is just to reduce the number of datasets that we host.  Heck, how did we end up with 200 datasets here anyway, and who exactly wanted to use them?  I trolled through a lot of old emails and other records, and now have a picture of how we got here.  What I still need is to be able to understand how actively each dataset is being used.  If no jobs are actually looking at a given dataset, I can delete it without anyone being offended.  (That’s how I got down to the 200 I’m quoting…I was able to knock off the easy ones.)  We need to develop some better tools for this.

All this is nothing compared to trying to understand how the funding that supports this and other work of our research group here actually flows to us.  That’s been another recent project.  It’s a bookkeeping exercise, for sure, but I wouldn’t call it particle physics.

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Countdown Down?

Wednesday, June 11th, 2008

Why do I  learn about things like the LHC Countdown web page from Gizmodo, of all places? Yes, I like gadgety things like the next physicist (can I get a witness here?), but I’m always surprised when I learn things relevant to, like, science, from, like, you know, nerds.

But why is the webpage, um, down for the count?  Gizmodo effect?  Google cache has a recent copy, and it doesn’t look like an official announcement page (as I expected).  Nor does it look like a doomsday-fringe page, as I expected next.  Seems to be a genuinely-excited person, but one who seems to be attracting a lot of excited, um, commenters.  Blogs are what they are, folks.

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It’s kind of mind-bending how fast things are ramping up, but no-one knows when “it” will happen, and how “it” will go — “it” being the initial collisions and the data analysis to follow. You get the same sense from everyone you talk to about the LHC, and especially from the younger people i know (students and postdocs) whose, well, *lives* depend on things getting going soon. I remember this feeling well, just as RHIC was starting — although things felt smaller in those days, or at least my 50-person experiment did.

This week is a Physics and Performance Workshop concerned with how ATLAS will deal with early data. I have a particular interest in this from the standpoint of a guy interested in heavy ions since this is precisely the data we will use to compare with lead-lead collisions when they eventually arrive. And yet, the last few months finishing up our proposal (more on that later, i’m serious) have shielded me from the outrageous amount of work going into so many different aspects of the detector and analysis. I’m scrambling to catch up long-distance, from my office, reading slides, and keeping up with emails, and we even have a heavy ion videoconference tomorrow (for which I’m assembling a talk now…). But there’s a lot to keep up with, and then I still have to get ready for the big ATLAS week in July! (and let’s not mention we have a short Alpine vacation to plan as well…)

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It was hectic week, though only four days long (we had family visiting up until very early Tuesday morning). Every day I had a meeting of some sort. I had a couple of slides to prepare. A relay race to run in and “train” for (see Monica’s post – BTW that is me second from the left, in the womens’ team with matching black shirts – which definitely improved our running 😉 ), and late Thursday until 10:00 pm doing a study (see this post about a previous one).

This week we spend another short spell running our detector for five days, like I described here. I am grateful I have no shifts (especially the 11pm-7am) and that the whole thing ends on Saturday afternoon. Just in time to join my husband for a two-day late anniversary dinner in downtown Geneva. Three years and counting (though I have known him much longer – since 1996).

So there is more hardware to prepare tomorrow morning and to check out. By the way that stands for Cosmic Run at Zero Tesla. Pronounced Crew-zay, due to the French influence around here.

On top of it all, EURO 2008 (soccer/football) has started. This time it is in Switzerland & Austria. I have never seen so many national flags on display, nor as much energy emanating from a crowd, than I did on Saturday while I was out shopping at a Geneva area mall. So, since I have almost all my paternal-side family in the Netherlands, now I head home to watch them play Italy. If they do well, I might finally buy the orange (eek) jersey for myself. You can see Dutch fans for miles…

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Cern Relay

Saturday, June 7th, 2008

Once a year, the CERN running club organizes a six person relay race within the main site of CERN. The distances in the relay are 1000m, 2x800m, 2x500m and 300m. And the race is open to the public. Now if your first impression is that this is a fun, leisurely race, mainly consisting of physics geeks trotting around the main site, let me correct you. This race is incredibly competitive. With teams training much in advance to win it. It is also very popular, with 76 teams (456 people) participating. But although most people take the run very seriously, we still insist on having geeky names like ‘Tile Missing Energy’ or ‘The Powercuts’ or ‘We’re cold’ (this IS a race at a particle physics lab after all).

For the past two years, I have run with a team of ATLAS women aptly named ‘The Running Athenas’ (‘Athena’ referring to the name of ATLAS’ detector simulation software). And for the second year in a row, we have taken second place! But this is also the second year in a row that we have lost to the CMS women’s team.

Hmmm… This does not bode well….

Here is our team on the 2nd place podium. Unfortunately this is not a particularly good picture but it is the only picture I have. But looking at this, I think it is pretty obvious why CMS is better. They have matching shirts. And it is a universal truth that any team with matching shirts runs faster.

So next year, Running Athenas, we are going to train! No excuses.

Or at a minimum we will get matching shirts.

ATLAS women's team

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