After a sequence of unplanned beam dump that were unsurprisingly all caused by disturbances on the power grid, there was an interesting dump this morning, which was caused by the internal dump trigger.
To make sure the beam energy is disposed of safely, there is a dump system. There is a separate system for each beam. If there is any reason to dump the beams (either because the operator wants to, or because there is something wrong), the beam is directed to a massive block of carbon by the "dump kicker magnets" that bend the beam.
There is an opening in the beam, the "abort gap" to allow switching the beam without destroying the dump kicker. So, it is very important that the dump kicker switches on at exactly the right moment. It is not possible to synchronize this externally, because the risk of something going wrong is too high (for example, the protons go fast than any signal in any wire...)
Therefore, the control system of the dump kicker has its own synchronization system that keeps track of the abort gap.
And now assume for a moment that this synchronization system fails... So the only option is to dump the beam as soon as something suspicious happens even before anything really goes wrong.
So that control system has a "hair trigger", and that is what cause the beam dump this morning. A small wobble in the beam, that wasn't harmful on itself, caused the system to decide "better safe than sorry" and dump the beam.
For even more details, see https://cds.cern.ch/record/927410/files/ab-2006-007.pdf
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