Construction and characteristics of a 340 MeV electron synchrotron magnet

Following an outline of the original specification of the magnet, its construction is described in detail. An abridged description of the magnet power supply is given. The characteristics of the magnet as revealed by comprehensive magnetic measurements are recorded, with a brief outline of the measuring techniques used. The quantities measured include the betatron orbit radius, the azimuthal variations of the guiding field at injection and as acceleration proceeds, and the field exponent n and its variation with azimuth. Measurements of many of these quantities were taken over a wide range of magnet excitation, and they led to a choice of the quartercycle of the magnet waveform to be used for acceleration, and of the value to which the magnet excitation should be reduced for the initial attempt to produce a beam. An attempt is made to explain qualitatively some rather obscure aspects of the magnet´s behaviour at the commencement of its operating cycle.