Locating the magnetic center of the SSC CDM using a temporary quadrupole field

The SSC dipole magnets must be very accurately aligned for the accelerator to work correctly. To align the magnets one must accurately know the center of the magnetic field. However, locating the center is difficult because of the extreme uniformity of the dipole field. A technique has been developed to determine the magnetic center of the SSC dipole magnet under ambient test conditions. This technique involves flowing current in the upper half of the coils in the direction opposite to the current in the lower half. This is done using a temporary lead connected to the splice joining the two coil halves and two matched power supplies. The resulting field is primarily skew quadrupole and has high field gradients which allow the center to be accurately located. The viability of this method has been verified by analysis using Taylor series expansion of the resulting magnetic field. Analysis has also verified that off-the-shelf power supplies have low enough mismatch to be used in this technique. The analytical results have been verified through the test of a short dipole magnet at the Brookhaven National Laboratory