IPAC2011 - List of Authors (Boergermann, F.-J.)

Paper	Title	Page
THPC157	Hot-/Cold-Side Characterization of Asymmetric Undulator Magnets	3257
	F.-J. Börgermann Vacuumschmelze GmbH & Co. KG, Hanau, Germany S. Marks LBNL, Berkeley, California, USA
	The homogeneity of permanent magnets for use in undulators is dominantly described by small variations in remanence (±1%) and magnetic angles (±1°). The definition and measurement of the so-called hot-/cold-side-effect has proven to be useful as characterization of higher order variations of the local field components. It is measured by a Hall probe at a distance of the half gap width from both magnet pole-surfaces. Typical results for a batch of magnets lie in a range of about ±2% or less. For symmetrical permanent magnet geometries, the distribution is symmetric about the value of zero. In a batch of magnets for a new EPU at LBNL, however, we found an asymmetric distribution of the hot-/cold-side-effect. This asymmetry is attributed to the geometrically asymmetric cut-outs inside the magnets used for fixture on the aluminum keepers. We present a theoretical model which can predict this asymmetric influence on the hot-/cold-side-effect resulting from these small geometric asymmetries. The method may also be used to pre-calculate corrected specification values for the near-field results for future undulator magnets.

Paper

Title

Page

Hot-/Cold-Side Characterization of Asymmetric Undulator Magnets

3257

F.-J. Börgermann
Vacuumschmelze GmbH & Co. KG, Hanau, Germany
S. Marks
LBNL, Berkeley, California, USA

The homogeneity of permanent magnets for use in undulators is dominantly described by small variations in remanence (±1%) and magnetic angles (±1°). The definition and measurement of the so-called hot-/cold-side-effect has proven to be useful as characterization of higher order variations of the local field components. It is measured by a Hall probe at a distance of the half gap width from both magnet pole-surfaces. Typical results for a batch of magnets lie in a range of about ±2% or less. For symmetrical permanent magnet geometries, the distribution is symmetric about the value of zero. In a batch of magnets for a new EPU at LBNL, however, we found an asymmetric distribution of the hot-/cold-side-effect. This asymmetry is attributed to the geometrically asymmetric cut-outs inside the magnets used for fixture on the aluminum keepers. We present a theoretical model which can predict this asymmetric influence on the hot-/cold-side-effect resulting from these small geometric asymmetries. The method may also be used to pre-calculate corrected specification values for the near-field results for future undulator magnets.