Beamline magnet polarity indication

Abstract

The “Convention on MICE Beam Line Magnet Polarities” (MICE Note 198) defines the electrical input needed for the correct magnetic performance of each magnet, and identifies “positive” and “negative” terminals at the magnets and hence associates the labels “positive” and “negative” (and associated colouring) with the cables. This can result in "positive" cables having to be connected to the negative terminal on the power supply (and vice versa), which was not accepted by the electricians. It would seem preferable to have the cables labelled using a scheme that does NOT directly incorporate (or imply) the words “positive” and “negative”, or the associated colours of red and black. Beyond this, the aim here is neither to contradict nor supersede MICE Note 198. The aim is a scheme that makes it straightforward to open a cabinet in the MICE Hall and confirm that the wiring is correct with a simple visual check. This is achieved by i) labelling one set of leads at the magnet end with the word "reference"; and ii) labelling one set of leads at the supply end with the word "beamline". Then: At the MAGNETS: The “reference” leads are permanently connected to the “positive” terminal At the SUPPLIES: If the “beamline” leads are connected to the positive output, have a “positive beamline” If the “beamline” leads are connected to the negative output, have a “negative beamline”.