4 ms·

Generally you would fill the machine, then circulate beam "stable", until it wears out (loose luminosity), then dump the remaining, and start again. This is cal

by Create 15y ago

Generally you would fill the machine, then circulate beam "stable", until it wears out (loose luminosity), then dump the remaining, and start again. This is called a fill, and can last several hours. A fill has several runs, some experiments automatically change runs every hour. A run is generally with a given filter (trigger) setting/detector configuration. You would run 24/7, but due to the filling cycle, waiting for ramping up and stable beam etc. will give you "idle" overhead. Furthermore, you are "lucky" to reach flat top stable beam: magnets can quench, power supplies will trip etc. giving unscheduled downtime. Then there is scheduled downtime (like just recently), which can last years :) So all in all, you would get a few dozen weeks of real operations a year, which would include some stable beam (if you aren't into beam gas studies or cosmics).

AretNCarlsen 15y ago
Do you know what the actual average uptime has been per operation? I have never seen that number.
- Create 15y ago
  To be fair, the metric for benchmarking is delivered/recorded luminosity. The machine delivers, and the detector records. It is this efficiency that funding agencies are shown in the periodic reports. Strictly speaking, (down)time can be "irrelevant", in the sense, that with higher luminosity you get more data (LHC can catchup on Tevatron easy). You can have 5 nine uptime, with 1 bunch circulating, or lots of bunches of particles (the beam is not continuous, it comes in trains of particles). So one thing is, that you also go for as many bunches as possible... But the periodical reports are on cdsweb, because of the public funding agencies ie. for the machine itself, setting an upper boundary: "Downtime statistics over the 2010 run" -- Chamonix 2011 Workshop on LHC Performance, Chamonix, France, 24 - 28 Jan 2011, pp.70-74. Then the DAQ of your experiment of choice comes on top of this...

by Create 15y ago

AretNCarlsen 15y ago

Do you know what the actual average uptime has been per operation? I have never seen that number.

Create 15y ago
To be fair, the metric for benchmarking is delivered/recorded luminosity. The machine delivers, and the detector records. It is this efficiency that funding agencies are shown in the periodic reports. Strictly speaking, (down)time can be "irrelevant", in the sense, that with higher luminosity you get more data (LHC can catchup on Tevatron easy). You can have 5 nine uptime, with 1 bunch circulating, or lots of bunches of particles (the beam is not continuous, it comes in trains of particles). So one thing is, that you also go for as many bunches as possible... But the periodical reports are on cdsweb, because of the public funding agencies ie. for the machine itself, setting an upper boundary: "Downtime statistics over the 2010 run" -- Chamonix 2011 Workshop on LHC Performance, Chamonix, France, 24 - 28 Jan 2011, pp.70-74. Then the DAQ of your experiment of choice comes on top of this...