Magnetic measurements of large aperture superconducting quadrupole magnets for TJNAF´s High Momentum Spectrometer

The results of the field mapping measurements of Thomas Jefferson National Accelerator Facility´s three large aperture, cold iron, laminated yoke superconducting quadrupole magnets for the High Momentum Spectrometer will be presented. These magnets were mapped using a rotating coil assembly housed within a G-10 drum. A description of the apparatus and technique used to map the magnets over an excitation range of 0 to 2 Tesla will be described. This method of mapping provides for an almost real time measurement of field strength, effective field length, field gradient, transfer function and the determination of symmetry planes. The hysteresis loop and affects of eddy currents will be shown. A comparison of the measured field values with calculated values will also be given.