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Posts Tagged ‘control room’

Why are you still doing night shifts?

Thursday, November 13th, 2008

This is a question I’ve received recently from a couple of my friends in the theory community.  Theoretical particle physicists are pretty smart people, and they do know a little something about particle detectors — so if they’re wondering, then I’m sure some of you will be curious too!  This is also a chance to see a snapshot of my psychological state at the end of a night shift: I wrote all of this to explain what I was doing between 6:20 and 6:45 in the morning a couple weeks ago.  My only edits are two places where I wrote something incorrect and replaced it with a new explanation in brackets.

To summarize: I’m busy this week and getting an easy entry out of cutting and pasting from my gChat log.

Again, the question was (more or less), “Why are you still doing night shifts when the accelerator, and large parts of the ATLAS detector, are off?”  Here’s my answer:

06:22 calibrate the detector
the pixel detector has 80 million channels (i.e. pixels, 400 x 50 microns)
06:23 they actually live, physically, on about 1700 modules, which talk to various hierarchically-organized computers
06:24 [to transmit the data the 100 meters to the counting room without high voltage or repeaters] we have optical links for transmitting the data from inside the detector until it gets outside
thus we need lasers to turn digital signals into optical light, and then we also need to convert the light back
the lasers have to be timed and powered correctly, as does whatever reads the information
06:25 at the moment, the ATLAS pixel detector isn’t using some fraction like [3%] of its modules, because they aren’t set correctly. in some cases, they may be impossible to set correctly until we can open the detector and replace components — which may be many years
but in other cases, the automatic-setting didn’t work, and we have to take a closer look.
06:26 some experts were in here today to try to recover a few such modules by taking that closer look; now I’m running scans that tell us if they were succesful or not.
06:27 that’s only one example of the kind of thing we do. there are a lot of things you can set on every module, and we have to get them all set right.
06:38 [My friend asks why we run all night, and if we run all the time]
06:43 me: yes, we have finite time, and lots of work to do
and clearly more people than pixel detectors.
06:44 once the cooling goes off, in a few weeks, we have to turn the modules off. then there’s only a few kinds of calibration scans/studies we can do

It’s worth noting that now, two weeks later, all the optical links are working well, except for a very few that are hard-core unrecoverable — thanks to the work of the experts who looked at the tuning and the very small contribution I made by running scans for them overnight.  Our night shifts continue, with a few nights each from over a dozen people in this month alone.   Although the details of the work at the moment are different, but the overall plan is the same: to have our subdetector, the last one installed, be as ready as the rest of ATLAS when data finally arrives next year!

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Take the Helm, Mr. Chekov

Monday, October 20th, 2008

Seth on Pixel Data Aquisition shiftAuthor’s note: This entry is mostly for my mother. If it happens to amuse anyone else, this is purely by coincidence. Also, there is no need to leave comments informing me that I’m an enormous nerd; I have noticed.

It’s true, life here at CERN is pretty much like Star Trek, or at least it looks that way sometimes. After training last month, and some very hectic shifts earlier this month, I’ve finally had a chance to get a picture of myself at the Pixel Detector operation station in the ATLAS control room. I have lots of screens with technical information in front of me, and the front of the room has a full seven projection screens.

Driving the Pixel Detector is not exactly like driving the USS Enterprise, of course. Where they have a navigator and a helmsman helmsperson, we have a shifter who does Detector Control and one who does Data Acquisition. (I do the latter, although I plan eventually to qualify for both so I can operate the whole thing when everything is very stable.) While they do things like “pivot at warp 2” or “reroute auxilliary power through the main deflector dish to produce a tachyon pulse,” we are more likely to “disable a Read Out Driver to re-enter ATLAS combined running” or “consult the data quality shifter about low statistics in the ID cosmic data stream.” The Pixel Detector has a Shift Leader, who’s sort of like the captain, but they’re only around some of the time if nothing exciting is happening. And of course the Pixel shifters are part of a much larger shift crew, which dwarfs the number of people it apparently takes to operate a starship.

Ok, it’s not that much like Star Trek after all, but — dare I say it? — it’s actually cooler, because it’s real.

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First ATLAS Pixel Tracks!

Sunday, September 14th, 2008

I’m on my 18th hour on training shift since Saturday morning, getting in as much time in the control room as I can, and it’s been a very exciting time. One of my colleagues has just discovered that, last night, we recorded the first cosmic ray tracks in the ATLAS pixel detector!

First ATLAS Pixel Detector Track!

This is very exciting news for us; we’re working right up to the wire to make sure our pixel detector is able to run stably along with the rest of the detector. Collisions are coming soon soon soon!

Update (Sept 15): In response to two excellent questions in the comments, I wrote in a little more detail what you’re looking at in the picture. I figure the explanations might as well go in the entry:

1. What’s the perspective? Where’s the LHC?

You’re looking at the inner part of the ATLAS detector, which is wrapped around one of the collision points of the LHC. The large image in the upper left is a cross-section of the detector; the white dot in the very center is where the LHC beam pipe is. The image along the bottom shows the same tracks from the side; the LHC beam pipe isn’t shown, but it would run horizontally (along the Y’ = 0 cm line).

2. What do the dot colors mean? What’s the line?

All the dots are the actual points at which we have a signal from our detector. The red dots represent the signal that we think was left by a charged particle when it passed through, and the red line is the path we think that particle took (i.e. the “track”). The green dots are also signals in the detector, but we think they’re random firings in our electronics, because we can’t make any tracks out of them.

It may look like a lot of electronic noise, because there are more hits from random firings than from the track. But remember that there were only one or two tracks to be found, whereas we have over eighty million pixels in our detector. Thus the fraction of noisy pixels was actually quite small, and certainly didn’t interfere with finding the track. We also have a list of especially noisy pixels that we can “mask” (i.e. ignore), which will bring down the noise by quite a lot but which we haven’t begun to use yet.

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Night and Day

Friday, September 12th, 2008

It’s Saturday morning, and I’m up at 6 AM again for my fourth training shift in eight days.  I’m tired.  I’ve not only being dealing with getting up very early, but also with staying up late: on Wednesday, I was the “live from the control room” connection for a San Francisco Bay Area party to celebrate the start of the LHC.  The party was in the evening there, which meant the middle of the night here, and so for me, Circulation Day stretched from 9 AM until 6 AM the following morning, when I finally left work.  That made for a very abbreviated Thursday, because I had a shift yesterday (Friday) at 7 AM as well.

Anyway, I’ve actually had it easy with the shifts so far, because training shifts are all day shifts.  I’m (probably) almost done with them though, and ready to start running the station on my own. (There are experts on call if something happens that I’ve never seen, thankfully!)  I’ve just been asked to submit my shift availability for October, and here it is:

Seth's shift availability for October

Green means I’m willing to take a shift at that time, red means I can’t; the horizontal axis is the 31 days of the month, while the three vertical entries are the 7-3 day shift, the 3-11 evening shift, and the 11-7 night shift.  There are two things you should note:

  1. You can probably guess which weekend I’m meeting a friend in Zagreb, Croatia.
  2. I’m willing to take as many night shifts as day shifts — which means that I can be put on as many night shifts as the shift scheduler thinks is reasonable.  Three or four nights in a row is not unusual as all.

Fortunately, as a new shifter I’ll still be on the day shift for a bit, so I at least won’t be waking the experts up when I screw up and have to call them.  But there’s work to be done, and I have to be willing to work (almost) all the time.  And you know what?  I’m thrilled to be doing it.

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first CMS beam event

Wednesday, September 10th, 2008

This morning, at about 9:55 CERN time, the LHC beam was dumped on a
collimator just upstream of CMS. This is when we first saw for the
first time the beam activity in the detector, a picture is attached.

What you see is the debris of the beam particles hitting the collimators. The resulting shower then produced a lot of activity in our hadron calorimeter (blue) and some hits in our muon system (small green rectangles). And all of those dirty messy particle showers from three different angles, which is why we have three different figures for the same events. The inner detector was turned off due to the beam still being very unstable and it can actually be damaged easily by randomly flying particles.

I am so excited! I am currently in the CERN media center where things are buzzing with journalists from all over the world! Before I forget to brag about the fact that the google home page is LHC themed today!

First CMS beam event

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Wednesday Expectations

Sunday, September 7th, 2008

First beam is quickly approaching. For ATLAS. Actually several other experiments have already seen beam (it is hinted that CMS will see something today). But as ATLAS is the last experiment on the ring, it means that we have to wait until the 10th. It is annoying being the last on the ring sometimes.

For the 10th, the beam is only a single beam, so there will be no collisions. But it is still exciting all the same. And what can we expect to see in the detector with single beam? Two things.

One is ‘beam halo’ events. These are muons which have left the beam core and are moving along side the beam. The other is ‘beam gas interactions’ which are when one of the protons in the beam collides with some other particle in the beam pipe (the beam pipe is under vacuum but no vacuum is perfect). Even with these two types of events, we don’t expect to see a lot of hits in the detector. But even a few hits tells us a lot. Single beam is also very useful to help us establish our timing. This means determining when to read-out our electronics relative to when the beam bunch enters the detector. In other words, we won’t be sitting around, bored come Wednesday.

Someone once asked me what ATLAS planned to celebrate with. And the answer is… Champagne, of course. We even have it prepped and ready to go in control room (as seen here). The label reads ‘Break in case of collisions’. Not a problem.

Atlas celebrate

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Training Shift Liveblog

Thursday, September 4th, 2008

It may be bedtime back in the United States, but here in Geneva it’s six in the morning, and I’ve just dragged myself out of bed.  That’s because I have a “day” shift, which for some bizarre reason begins at 7AM; thus I’ll have to leave my apartment in downtown Geneva in complete darkness.  This is actually only a training shift, but I’m still very excited; I’ve spent a long time writing various analysis software, and it will be exciting to really get my hands on the detector!

I was actually in the control room for a few hours yesterday evening, watching one of the first times our pixel detector has been integrated with the whole “combined run,” and hoping to see a track.  It was very crowded then; we’ll see how things look at 7 AM.

(more…)

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The It Date

Thursday, August 14th, 2008

Since I have been blogging for close to a year now, let’s summarize my topics.

In the control room, taking cosmics data
In the control room again taking cosmics data
Crazy athletic adventure
Control room, More cosmics
Control room, yet again
Control room, still
Control room, yes still
More crazy athletic adventures
Control room
Control room
Control room, what am I still doing here?
Euro Cup
Euro Cup
Euro Cup
Euro Cup
Euro Cup
Euro cup over, banished to control room again
Control room
Control room. Again
Control room. Again. Again.

So… I spend a lot of time in the control room. If you haven’t noticed. And needless to say I am in the control room while writing this. This comes as no surprise.

September 10th. This is the new ‘it’ date. On this day, single beam will run around the ring (and through ATLAS) for the first time. And every reporter on the planet will be there. Many of them in the ATLAS control room (which is why I am strategically staking claim on my control room chair now).

Now don’t get me wrong, I cannot WAIT for beam. The 10th can’t come soon enough. But after long days I tell myself, ‘you think you spend a lot of time in the control room now… wait until there is beam’…. But although I do love sleep. And although the prospect of getting sleep is pretty dim for the months of September, October and November, you couldn’t pay me enough to leave the control room. Not now. Not with first beam in our grasp.

So is it September 10th yet?
.
.
.
.
How about now?

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Getting Ready

Friday, July 18th, 2008

The most feared/longed for date on ATLAS right now is August 11th. This is the day where we have to be out of the cavern. It is feared for people who are still completing the last of the detector installation, longed for by everyone (including those still doing installation) because it means beam is coming.

And only a few short weeks after the cavern closure, we can expect single beam (only one circulating beam with no collisions). And only a few short weeks after that, we can expect colliding beams.

So will ATLAS be ready? I find that I am asked this question more and more with each passing day. And the answer is…. Yes. Now if you ask me whether or not the calorimeters will be ready, the answer is a very definite yes! The calorimeters right now are in really good shape. Everything is installed, everything is powered, everything is being read-out.

It makes me so happy to say that.  When I started on ATLAS two years ago, Tile had problems with its power supplies. So we had essentially no supplies. And we needed 256.  We weren’t officially in the ‘panic’ state at that point, but we were certainly in the ‘very concerned’ state.

And now fast-forward less than two years. We are fully powered. With the exception of only a few Tile cells (0.4% for the exact count), all of our electronics are ready to go. Not that we don’t have things to still work on (I mean it is friday night and I am yet again still in the control room) but we are sitting pretty. And that is a really, really good feeling.

So beam-people. Is the beam ready yet?

How about now?

.

.

.

.

Now?

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Sometimes, Nothing Works

Tuesday, July 1st, 2008

ATLAS control room - nothing workingThis past Sunday, I signed up for an ATLAS pixel detector monitoring shift. Since the pixel detector isn’t actually running right now, the purpose of the shift was to test the path from the data aquisition system to the charts and graphs that we’ll actually look at, while the detector is running, to make sure everything is working. My title as a shifter was, according to the official schedule, a “non-expert,” which is entirely accurate—but another part of the purpose of the shift was for me to learn.

You can see my station in the picture at right, but you’ll notice that I’m not there. That’s because everything is broken, and an expert is trying to fix it, which is how everything was for my entire shift.

It wasn’t the monitoring per se that was broken, so there wasn’t much to be done in terms of understanding it, but I was able to learn a few things, especially about the bits and pieces that were broken. Maybe next time, I’ll see the same problem, and know what to do without calling in an expert quite so quickly; more likely, of course, I’ll see a completely new problem, but sometimes experience like this is the only way to learn.

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