Techniques for measurement of dipole endfields with a rigid integrating coil

The endfield is often one of the most critical regions in conventional accelerator magnets. While the magnetic field structure of dipole ends can be complicated, it can be well described by a few parameters which include the effective magnetic length, L_eff, and the integrated harmonics. Both of these parameters can be measured using a rigid coil which measures ∫Bdl in the endfield region as a function of insertion depth z and transverse displacement x. We employ a data analysis technique which uses these measurements to remove body field contributions to the end field integral, resulting in the effective integrated endfield shape. A least squares polynomial fit is then used to estimate the harmonic coefficients up to decapole. We also present the technique for measuring L_eff as a function of magnet current. These measurement techniques were successfully used in a study to finalize the design of the endpacks for the Fermilab Main Injector Dipole. The techniques are sufficiently general to be useful for other applications, such as the testing of the SSC Medium Energy Booster endpacks