Noise on the UCN is usually observed as increasing error counts on the UCN communications statistics page.
Noise predominantly on one UCN cableIf the noise is appearing on only one UCN cable (A or B), then this is most likely caused by loose UCN connections on boards or taps. Tightening all the connectors related to the particular cable usually resolves the problem.
If noise is still present, then it could be due to faulty UCN interface cards in the NIM or APMM/HPMM, faulty taps or faults in the UCN cables themselves. There is no real short cut here - the only realistic approach is to systematically replace the various components connected to the UCN cable in question.
It can be quite difficult to track down noise problems, as the following examples may illustrate:
Noise present on both UCN cablesWhere the noise is present on both A and B UCN cables, the noise is most likely due to the cable's proximity to high voltage machinery or cabling.
In the event that the noise has arisen recently, it may be worth checking if there are any new devices in the plant which could be causing the noise.
While the noise usually appears near the noise source, the diagnostic displays do not reveal the actual node location. A high noise count at a particular node may, however, reveal the closest position to the noise source.
At one site, for example, the noise was due the location of the UCN cables relative to a high voltage piece of equipment. It was necessary to shield the UCN cables with steel wire armour, ensuring that the cable shield was grounded. Eventually, it was also necessary to install additional electrostatic shielding around the cables.