Paper 
Title 
Page 
WEPO020 
Magnetic Field Inspection and Analysis of Multipole Lattice Magnets using a Rotatingcoil 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 rotatingcoil 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 magnetfeet 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 micrometer in the horizontal direction; the granite support height of the RCS system is accurate within 5 micrometer after artificial polishing. The measurement reproducibility of the field center was better than 10 micrometer 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 3Dcoordinatemeasuring machine. The multipole errors obtained from RCS will be compared with a Hallprobe 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 xrays 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.



THPC175 
Spectral Analysis of Arbitrary Strength Parameter for Various Insertion Devices 
3311 

 S.D. Chen, T.M. Uen
NCTU, Hsinchu, Taiwan
 C.S. Hwang
NSRRC, Hsinchu, Taiwan



An insertion device (ID) with medium strength parameter was hard to be defined as a wiggler or an undulator. Usually, this kind of ID was classified according to the user’s definition and to select the spectrum calculation formula of wiggler or undulator. The spectrum calculation formula for wiggler or undulator is quite difference and consequently obtain a big different flux density by using the same strength parameter. So, it is no way that the spectrum calculation of them is consistent. Therefore, a universal formula will be developed for the spectrum analysis for the different kinds of insertion devices that is with large different strength parameter (deflection parameter). Consequently, a modified spectrum calculation formula of ID with medium strength parameter was studied by reviewing the difference of existing spectrum formulas. The familiar formula of calculating undulator spectrum was modified and can be used on ID with arbitrary strength parameter. The algorithm of formula modification was described. Some relative issue, like the effect of phase error and energy spread, and taper undulator were also discussed herein.



THPC176 
Progress in Insertion Devices for TPS in Phase I 
3314 

 C.H. Chang, C.H. Chang, J.C. Huang, C.S. Hwang, C.K. Yang
NSRRC, Hsinchu, Taiwan



Taiwan Photon Source (TPS) with beam energy 3 GeV and beam current 500 mA is a thirdgeneration synchrotron radiation facility of medium energy. In the initial commissioning stage of TPS, the machine will be equipped with ten insertion devices (ID) and serve seven beamlines in phase I. Of these, three long straight sections configured as a doubleminimum betay function lattice design with minimized beam influence of emittance are used for the installation of a pair of insertion devices in a straight section, two undulators of APPLEII type and four invacuum undulators (IU), to produce great brilliance and coherent Xrays with great flux. The details of these insertion devices are explained herein.



THPC177 
Field Correction Results from NSRRC Elliptically Polarized Undulator 46 
3317 

 J.C. Huang, C.H. Chang, C.S. Hwang, C. JunTune, F.Y. Lin
NSRRC, Hsinchu, Taiwan



Elliptically polarized undulator (EPU) is a common insertion device to use in storage ring in order to provide circular polarization. The field correction is an essential step for EPU construction, and it can prevent the photon flux reduction from idea case and electron beam trajectory and exit angle from EPU. The conventional field correction method is tedious works and strongly based on experiences. An initial state of NSRRC EPU46 has phase error over 40 degrees, and many difficulties on field correction to reduce the phase error under 5 degrees. This paper will describe the detailed magnetic field correction process and practical results from in NSRRC EPU.


