Today marked the end of the combined running (using the entire detector as it would be for recording collisions data) of the ATLAS detector for 2008. Unfortunately the running didn’t include any time with collisions this year, but as you can see in the image, we have still been recording tons of data recently. The blue line is the sum of all the events recorded by ATLAS in days since September 13. “Events” are just snapshots taken at one moment by the detector.
The last few weeks were devoted to getting as much high quality cosmic-ray data recorded as possible, while the detector was still “all in one piece”. Over the next few months, there will still be data recorded, but more often with a few pieces at a time, and usually some piece off for maintenance at any moment.
The data that was just recorded will be analyzed for the next few months to calibrate the detector and get ready for collisions in 2009. The total number of events recorded in the last 44 days was 216 million. That works out to about 57 events recorded per second, every second of the day, for 44 days straight. Each event is a megabyte or so, so we are talking hundreds of terabytes of data written out. You can also see, it wasn’t a constant 57 events per second. There was a week where about half the total data was recorded that was much faster during some special running to accumulate data for the inner detector calibration.
Tags: ATLAS
Apologies for what maybe a nonsensical question. If each event records approx 1mb of data, what does that data consist of? Is it all parts of the detector returns bundled up as 1 packet of data? Does each part get analysed or will all 216 events be analysed in one big run? Thank you in advance for taking the time to reply.
PS Thank you also for this blog as it gives me a chance to glimpse into a world I would not otherwise be able to see.
Hi Mark,
Yes, that 1MB is the total file, which is composed of information from all the different parts of the ATLAS detector, usually information like how much energy was recorded in each of the different detector elements. Depending on the configuration, the file size could be much bigger, if we write out extra information for debugging purposes.
Individual physicists might only actually be interested in part of that total MB or so, and in only some of the 216 million events. The great thing about ATLAS is that it is a multi-purpose detector which allows lots of different research questions to be addressed simultaneously, and different people will be interested in different data that is reecorded.
What type of a computer(s) are you using to collect and store all of this information? And on the other end what are you backing it up to? You made a salesperson very, very happy.