IPAC2011 - List of Authors (Jan, J.C.)

Paper	Title	Page
WEPO020	Magnetic Field Inspection and Analysis of Multipole Lattice Magnets using a Rotating-coil Measurement System*	2442
	J.C. Jan, C.-H. Chang, Y.L. Chu, T.Y. Chung, C.-S. Hwang, C.Y. Kuo, F.-Y. Lin NSRRC, Hsinchu, Taiwan
	A precise rotating-coil measurement system (RCS) was constructed to characterize the field quality and field center of multipole lattice magnets of Taiwan Photon Source (TPS). The mechanical center of magnets is determined by the two references of the magnet-feet and the RCS system is used to characterize the field center. The location of the magnetic field center is quantitatively accurate to better than 20 micro-meter in the horizontal direction; the granite support height of the RCS system is accurate within 5 micro-meter after artificial polishing. The measurement reproducibility of the field center was better than 10 micro-meter when the magnets were reinstalled. The relative accuracy of the multipoles components is better than 2×10^-5. This paper reports the details of the bench construction and the unit composition. The field center with RCS measurement will be compared and discussed with the 3D-coordinate-measuring machine. The multipole errors obtained from RCS will be compared with a Hall-probe measurement system.

THPC168	Field Error Correction for a Superconducting Undulator	3290
	S. Chunjarean PAL, Pohang, Kyungbuk, Republic of Korea C.-S. Hwang, J.C. Jan NSRRC, Hsinchu, Taiwan H. Wiedemann SLAC, Menlo Park, California, USA
	To reach higher photon energies in the region of soft or hard x-rays with high photon beam brightness in low energy storage rings, superconducting undulators with very short period length and high magnetic field strength are required. Because undulator radiation comes in a line spectrum, photons up to the 7th harmonic are desired. The photon brightness in such harmonics is strongly dependent on perfect periodicity of the magnetic field. Such imperfections also appear in conventional permanent material undulators, which can be corrected by well developed and efficient shimming. Unfortunately, this method cannot be applied to superconducting undulators. Therefore, we present a new approach to field corrections by modification of the magnetic field saturation in each pole. In this paper it is shown that this approach can reduce not only the magnetic field error but also greatly improves phase errors from period to period. The proposed method works quite local with only small perturbations in neighboring poles. The tenability is preserved for most of the field excitations and is reduced only at extreme parameters.

Paper

Title

Page

Magnetic Field Inspection and Analysis of Multipole Lattice Magnets using a Rotating-coil Measurement System*

2442

J.C. Jan, C.-H. Chang, Y.L. Chu, T.Y. Chung, C.-S. Hwang, C.Y. Kuo, F.-Y. Lin
NSRRC, Hsinchu, Taiwan

A precise rotating-coil measurement system (RCS) was constructed to characterize the field quality and field center of multipole lattice magnets of Taiwan Photon Source (TPS). The mechanical center of magnets is determined by the two references of the magnet-feet and the RCS system is used to characterize the field center. The location of the magnetic field center is quantitatively accurate to better than 20 micro-meter in the horizontal direction; the granite support height of the RCS system is accurate within 5 micro-meter after artificial polishing. The measurement reproducibility of the field center was better than 10 micro-meter when the magnets were reinstalled. The relative accuracy of the multipoles components is better than 2×10^-5. This paper reports the details of the bench construction and the unit composition. The field center with RCS measurement will be compared and discussed with the 3D-coordinate-measuring machine. The multipole errors obtained from RCS will be compared with a Hall-probe measurement system.

THPC168

Field Error Correction for a Superconducting Undulator

3290

S. Chunjarean
PAL, Pohang, Kyungbuk, Republic of Korea
C.-S. Hwang, J.C. Jan
NSRRC, Hsinchu, Taiwan
H. Wiedemann
SLAC, Menlo Park, California, USA

To reach higher photon energies in the region of soft or hard x-rays with high photon beam brightness in low energy storage rings, superconducting undulators with very short period length and high magnetic field strength are required. Because undulator radiation comes in a line spectrum, photons up to the 7th harmonic are desired. The photon brightness in such harmonics is strongly dependent on perfect periodicity of the magnetic field. Such imperfections also appear in conventional permanent material undulators, which can be corrected by well developed and efficient shimming. Unfortunately, this method cannot be applied to superconducting undulators. Therefore, we present a new approach to field corrections by modification of the magnetic field saturation in each pole. In this paper it is shown that this approach can reduce not only the magnetic field error but also greatly improves phase errors from period to period. The proposed method works quite local with only small perturbations in neighboring poles. The tenability is preserved for most of the field excitations and is reduced only at extreme parameters.