A Rotating Coil Apparatus with Sub-micrometer Magnetic Center….pdfVIP

SLAC–PUB–11473 December 2005 A Rotating Coil Apparatus with Sub-micrometer Magnetic Center * Measurement Stability Cherrill M. Spencer, Scott D. Anderson, David R. Jensen. Zachary R. Wolf Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 Abstract A rotating double coil apparatus has been designed and built so that the relative magnetic center change of a quadrupole is measured to an uncertainty smaller than 0.02 micrometers (=micron, µm) for a single measurement. Furthermore, repeated measurements over about an hour vary by less than 0.1 µm and by less than 1 µm for periods of 24 hrs or longer. Correlation analyses of long data runs show that the magnet center measurement is sensitive to mechanical effects, such as vibration and rotating part wear, as well as to environmental effects, such as temperature and relative humidity. Evolving apparatus design has minimized mechanical noise and environmental isolation has reduced the effects of the surrounding environment so that sub-micron level measurement uncertainties and micron level stability have been achieved for multi-day measurement periods. Apparatus design evolution will be described in detail and correlation data taken on water-cooled electromagnet and adjustable permanent quadrupoles, which are about 350 mm in overall length, will be shown. These