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To facilitate high-sensitivity soft X-ray magnetic circular dichroism experiments, a dynamic local bump system has been developed at the SRRC storage ring. This system was devised to vary dynamically the vertical slope of the electron beam in a bending magnet, producing, in the electron orbit plane, soft X-rays with an alternating elliptical polarization. The local bump was created by using two pairs of vertical correctors located on each side of the bending magnet. The bump strength coef®cient was obtained both from calculated estimation and from measured beam-response matrices. Control electronics for proper bump strength settings were designed to incorporate the existing orbitcorrector function. A corresponding graphic user interface was implemented so that the bump amplitude could be easily adjusted. The performance of this system is presented. Disturbance on the stored electron beam orbit was observed whilē ipping the corrector polarity during EPBM (elliptical polarization from bending magnets) operation. A local feedback loop, developed to eliminate such disturbance on other beamlines, is also described.

The mechanism of beam loss and radiation hot spots at the Taiwan Light Source (TLS) and Taiwan Photon Source (TPS) are studied using various types of beam loss monitors (BLMs). The performance of readout devices and the system integration are also presented in this paper. At the TLS, the high beam loss spots downstream of the superconducting wigglers comes from the vertical aperture limit. The highest radiation is detected after the injection section and comes mainly from X-rays generated by the superconducting wavelength shifter installed between the 3rd and 4th kickers. At the Taiwan Photon Source, the high radiation spots are located before the second bending magnet and straight section because there are photon absorbers nearby to contain synchrotron radiation. In order to enhance the sensitivity to beam loss, 1-mm thick lead is used to shield synchrotron radiation to the BLM. The beam loss coming from scattering occurs downstream of the following bending magnet in a poor vacuum region for inelastic scattering and after vertical aperture limitation for elastic scattering. During routine operation in which the beam loss mainly comes from intra beam scattering during decay period, the beam loss pattern varies with the gap and phase of the insertion devices especially for the narrowest gaps. These BLMs are used to adjust skew-quads or sextupoles to minimize the beam loss for maximum beam lifetime. The precise beam energy of the TPS is also calibrated using spin-depolarization in which the beam losses are detected by scintillation detectors. The energy stability during continuous routine operation can be kept to within 10−5 by radio frequency adjustments and fast orbit feedback.

Nonlinear beam dynamics experiments were conducted at the Taiwan Light Source (TLS) of the Synchrotron Radiation Research Center (SRRC). We employed a turn-by-turn BPM system to obtain nonlinear dynamics of the excited bunched beam. Extracted nonlinear parameters are compared with the simulation results.