Magnetic Field Measurements of the DESY II Magnets

A new method has been developed for the precise magnetic field measurements in ac magnets. The technique has been applied to the DESY II dipoles and quadrupoles. Movable coils of various lengths are used, and voltage induced by the ac excitatition is compensated by reference coil. A fast ADC triggered at different levels of magnet current converts the output of a low drift analogue integrator. Measurement and data handling are microprocessor controlled. The data are sent to the computer centre for analysis and storage. From there the results and a graphic display are sent back to a local interactive terminal for qualitative online checking.