UFO

[pjotertje]

Can someone explain to me what exactly is a UFO in the LHC?

example UFO in pt 8

[Kasuha]

It's an event when beam losses suddenly quickly raise and quickly disappear again in one place, the whole event is usually very short. Some time ago they were causing many unexpected beam dumps. It is not certain what is causing it (hence UFO) but the working hypothesis is they're microscopic dust particles falling through beam trajectory.

[PhilG]

The number of dumps due to UFOs (Unidentified Falling Objects) has increased dramatically since they got to 1092 bunches. It is the most common cause of beam dumps now. http://lhc-commissioning.web.cern.ch/lh ... une11.pptx

Is this just due to the higher intensity or did someone tap the beam pipe?

Previously they reduced the number of such dumps by increasing the dump thresholds. Can that be done again or is it too dangerous?

[PhilG]

Morning report says they changed some UFO monitoring levels.
If only all the problems could be fixed so easily

[jmc2000]

Morning report says they changed some UFO monitoring levels.
If only all the problems could be fixed so easily

I think the problems makes it more interesting. They don't understand why emittance is a such problem after a long fill, and they think that ufos are microscopic dust particles so god knows how they're going to sort that one out. I'd prefer these problems compared to such trivial matters as a power supply going down or a communication problem.