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Archive for June, 2008


Monday, June 30th, 2008

And the winner of the Euro Cup is… SPAIN!!!

This is too good to be true. Needless to say, I am totally thrilled. For so many years, we fans of the Spanish team have waited patiently for this moment. I mean, who can forget Spain’s painful loss in penalties to South Korea in the quarter finals of the 2002 World Cup? Or barely not advancing to the quarter finals in Euro 2004? Or that devastating loss to France in the round of 16 of the World Cup 2006? But only one victory makes up for all the losses.

So, what is next?

For Spain. World Cup 2010 and victory again!!

For non-soccer fans. A return to sanity.

For me. It’s back to work.


Today’s post is not about physics, but is definitely related to something particle physicists do quite frequently: travel.

The trip is to Amsterdam, something I do monthly as I have many friends and all my family there. This time it is a more than normally joyous occasion, a friends wedding. And just like every month, I spend a considerable amount of time trying to arrange transportation. As usual there are two things to consider: cost and time to take off work. The distance is almost 1000 kilometers (over 600 miles). Besides driving, which is not an option as I do not have a car (it would be unmaintainable as there is no parking in Geneva and besides that the public transport is excellent in Switzerland, and considering the high gas prices in Europe it will not be very competitive anyway) there are three travel options. And I would like to share the results of my search with you as it’s not only unexpected but I also do not understand the why: (more…)



Sunday, June 29th, 2008

Just returning from the last of the EPAC08 series (European particle accelerator conference) in Genova, Italy. Never traveled with 70 colleagues on a bus to a conference, but not having to deal air travel and lost baggages was somewhat pleasing. The 7 hour ride was a bit long, by about a couple of hours. Perhaps the DG warned the driver of the precious cargo onboard, imagine the delay of the LHC startup without them!

Many interesting talks and posters and many more familiar faces. Talking about LHC status, the cryogenic folk expect to cool all the 8 sectors down to 1.9 K and try to finish the hardware commissioning and powering tests sometime before mid-august. The optimistic feel that the beam will make into the LHC by the end of August and have collisions in Sep-Oct. Naturally there will be delays, but will the pressure of the deadlines help speed up the commissioning and hopefully not result in some hasty decisions. It feels a bit like the pressure just before the conference submission deadlines, I mean for “last minuters” like me. It was announced that the 1400 papers submitted to EPAC08 are almost processed and available online even before the end of the conference, lets hope the LHC commissioning will beat all expectations. I leave you with one of the conclusions from the ending plenaries at EPAC where Hitoshi Murayama hopes a New York Times headline, “The other half of the world discovered”!


Simultaneous Work and Play

Tuesday, June 24th, 2008

Another weekend of combined ATLAS running.

In the past we would try to exercise the combined system in these big ‘Milestone’ weeks. And those haven’t gone away but now as the beam looms nearer and nearer we have added weekly-weekend combined running as well.

In other words: There goes my summer completely.

ATLAS is just big. In all dimensions. In physical size, in the amount of electronics, in the number of computers, in the number of people. Everything. And so it is no wonder that when we try to get all the little parts of this big system running smoothly together it takes a lot of time.

And getting the system running is exactly what me and several others spent 17 consecutive hours doing last Friday. But! We had things to keep us happy. Initially I was bummed that I was stuck in the control room while the Euro cup quarter-finals were being played.

But hey, this is a high-tech experiment. With a very nice big flat screen, nominally used for displaying the beam parameters. But since there is no beam, why not use it to display… say… Croatia vs. Turkey…

By the end of the night, we had the combined run set-up and the game on the big screen. Here is the video which proves that while we were indeed watching the game, the run was actually going. As the footage was taken from a phone, it is a little hard to see but the zoom in on the computer screen shows a happily running detector. Really.


Critical Mass

Tuesday, June 24th, 2008

LBNL Postdoc OfficeIf Monica is right that, within the “city of ATLAS,” your university’s research group is like your family, then I am blessed with a very big family indeed.  With the combined resources of a major research university and a U. S. national lab, the UC Berkeley / Lawrence Berkeley National Laboratory ATLAS group is one of the largest on the experiment.  Pictured at right are five of the seven people currently working in one of the three offices we fill at CERN; my office down the hall is smaller but technically has more people, although thankfully not all of them are ever here at the same time.  (If they were, some desks would have three people!) Those three offices, along with a few people scattered around in other locations, form the half of our group that works here in Geneva.  Roughly the same number of people work back in Berkeley, although the relative population varies from week to week as people move back and forth for meetings and detector work.   According to one list I found, we seem to have over fifty people officially working on the experiment in various capacities—engineers, technicians, software experts, and physicists running the gamut from detector specialists to theorists—although I can’t say I know them all.

Just as there are complications to having a large family, there are definite complications to working in such a large group—in particular, coordinating all of our activities, especially between people in Geneva and Berkeley—but on the whole it’s a good thing.  In fact, the size of the ATLAS group was one of the two main reasons I came to Berkeley, and I still tell prospective students the same thing four years later.  Why?  Well, as Monica explained, your group members are the people you go to for help, advice, and to ask stupid questions.  They’re the people you can drop in on rather than making an email appointment, and who will help you if they can even when they’re not an official expert.  There are half a dozen faculty members other than my advisor to talk things over with, when I need a different perspective, a different set of expertise, or just because he’s out of town.  Our postdocs all did succesful work on other partical physics experiments, particularly CDF and D0 at the Tevatron (the LHC’s most direct predecessor) at Fermilab, and they are pretty good at explaining the nitty gritty details of how a real physics analysis goes.  For almost anything I might start to work on, there’s someone who’s already working on something similar, or who has in the past.  And that saves me a lot of time and frustration.


Last Friday, everyone here at CERN who works for a US institute was invited to get together for a picture. An estimated 300 people (out of about the 1700 total) showed up. Try and find all of your favorite US LHC bloggers:

some of the US LHC members


Speaking of Cosmics…

Saturday, June 21st, 2008

As reported in the Times (which generally makes things “real”, at least in the US, right?), the CERN-appointed LHC Safety Assessment Group (LSAG) has finally come out with its report.

The Large Hadron Collider (LHC) can achieve an energy that no other particle accelerators have reached before, but Nature routinely produces higher energies in cosmic-ray collisions. Concerns about the safety of whatever may be created in such high-energy particle collisions have been addressed for many years. In the light of new experimental data and theoretical understanding, the LHC Safety Assessment Group (LSAG) has updated a review of the analysis made in 2003 by the LHC Safety Study Group, a group of independent scientists.

LSAG reaffirms and extends the conclusions of the 2003 report that LHC collisions present no danger and that there are no reasons for concern. Whatever the LHC will do, Nature has already done many times over during the lifetime of the Earth and other astronomical bodies. The LSAG report has been reviewed and endorsed by CERN’s Scientific Policy Committee, a group of external scientists that advises CERN’s governing body, its Council.

“Nature has already generated on Earth as many collisions as about a million LHC experiments – and the planet still exists”. It almost makes the LHC sound boring since it’s been done over and over again and nothing “happened”. Fine, no one was looking in the right place, and individual microscopic collisions generally have no macroscopic effects (right?) but still. In any case, I think it’s great that CERN has really rolled up their sleeves and addressed this issue head-on. I’ll report back after having a chance to read it more carefully — but I’m already psyched finally to see the inclusion of actual RHIC data!


Pixel cosmics

Friday, June 20th, 2008

While most of my time is spent on computing issues, there is (just a little) more to my research life.  Our group is also involved in building, installing and commissioning CMS’s forward pixel detector.  This is a silicon-based detector which records the position of charged particles.  Wafers of silicon are segmented into little squares (the pixels) that are 150 microns on a side.  When charged particles pass through a pixel, a little bit of charge is liberated in the material.  This charge can be picked up on a tiny amplifier and recorded into the data stream.  By looking at patterns of pixels that have charge in them, we can reconstruct the paths of the particles that passed through.  One particularly striking aspect of these detectors (to me, at least) is the density of readout channels.  The forward pixel detector is a few wheels that are about 10 cm in radius, but the whole detector has millions of readout channels!  (When I was in grad school, I worked on a similar device that had about 26,000 channels.  It seemed like a lot at the time.)

Even though this detector hasn’t seen any beam yet, it is already time to think about replacing it; in a few years, its performance will be impaired by through radiation damage (it sits right next to the beam), and we can apply lessons that have been learned from building the current detector to the new one.

This summer, we set up a little lab down the hall from my office where we can start to study prototype detectors and readout chips for the next round.  We have a few spare pieces from the current detector and a rudimentary readout system for the electronics.  A couple of our students set up a couple of scintillators and phototubes so that we can trigger the readout on cosmic rays that pass through the silicon.  Here is a plot of the pulseheights that they read out of the system during a cosmic-ray run:

The curve that is superimposed on the distribution is a Landau function, which is what you expect to see.  Not bad!  Our guys pretty much got this on the first attempt — good for them.  I’m told that no one has actually seen an output spectrum from real incident particles from these devices for some time.  (We’ll be seeing lots of them in a few months, when the LHC starts up.)  Now we can start to think about looking how the performance varies as we vary the operating parameters, and about testing out prototype detectors when they become available.


Magnet Tests

Tuesday, June 17th, 2008

Who doesn’t love magnets. I remember as a kid having these two bar magnets and spending hours trying to move them around the kitchen table without actually making them touch (yes, this classifies as fun when you grew up in a small farming town that was 30 miles from the closest movie theater). The ATLAS magnets inspire the same feeling except now these magnets are superconducting and the size of a building (and we generally prefer it when they stay in one place).

ATLAS has two separate magnet systems used for bending the tracks of charge particles in the detector. The magnet surrounding the inner detector is a solenoid (the magnetic field points along the beam pipe). And the magnet for the muon system is a toroid (the magnetic field is circular around the beam pipe). The toroid magnet itself is in three sections: the barrel and two end-caps. And for a sense of size, here is one of the ‘little’ end-cap toroids being transported to the pit many months ago.

End cap toroid

Now that we are in the last steps of closing the detector, the final commissioning of the magnets has begun. The plan of the magnet commissioning is to test each of the four magnets separately (the two endcap toroids, the barrel toroid and the solenoid in that order) and then do the full combined test. And since you can’t have people working on other parts of ATLAS when there are large magnetic fields, all the testing is done at night. Over the past few weeks, the tests on one of the end-cap toroids have concluded (successfully!). Unfortunately in the second end-cap toroid, a helium leak was discovered (helium being used to cool the magnets). As a result, tests with this magnet had to be stopped in order to repair the leak. This does not delay us any but it does involve some reshuffling of the magnet commissioning schedule. Tonight will be the first test of the barrel toroid. Fingers crossed that it goes well!

Oh and Spain in an absolutely, spectacular goal in the last minute of injury time beat Sweden to secure their position in the quarter finals!! One step closer to Euro Cup glory!


Desperately Seeking Summer

Tuesday, June 17th, 2008

It is now June 17, four days until summer, and I wonder, will we have one at all? Normally, I like this time of year the best. Crisp mornings to jog in with warm afternoons to relax in, light early and late into the evening. Instead its been primarily cool and damp, and totally disappointing. I grew up in the California desert with >40C summer temperatures, so I like it warm and dry. The extra daylight here is a nice bonus.

We had a lovely April, so I went out and bought a nice outdoor table and chairs, so I could eat and relax on my terrace. I’ve just used it once – the weekend I bought it. Every weekend after that its been too wet or too cool. I finally had to bring the wood table top inside to treat it since it didn’t stay dry long enough to do it outside.

The potted plants, however don’t seem to mind too much, and there is enough sun for them. They keep flowering and growing, so I guess it isn’t as bad as I thought, since they’re happy. But I’m cranky from not being able to go and sit outside in the evening after work.

I’m going to file a complaint with Mother Nature.