A Study on Characteristics of Photon Beam in Electron Storage Rings

Abstract

In this dissertation we investigate the photon-beam stability of the Pohang Light Source II (PLS-II), a third-generation synchrotron-radiation source that has been in operation since 2013, and characteristics of a photon beam from the fourth-generation storage ring (4GSR), a nearly diffraction-limited storage ring in which the natural emittance is lower than 100 pm-rad which is two order of magnitude smaller than that of the existing third-generation synchrotron-radiation source. In PLS-II, during a user operation period the stability of the photon-beam trans verse position was achieved to less than 1 µm rms in the beamline front-end, where the photon-beam position monitor (PBPM) is installed. To avoid large heat load due to a photon beam from the elliptically polarized undulator, a new type of PBPM was designed and developed recently. At the same time the calibration method has also been improved. The resulting performance of this new PBPM is described in detail. Recently the Pohang Accelerator Laboratory proposed a new design of the Korea 4GSR that has the electron-beam energy of 4 GeV, the natural emittance of 58 pm-rad, and the circumference of 800 m. We studied properties of the photon beam from the designed 4GSR and preservation of coherence through beamline optical elements. Results of this study provide essential information for designing future beamlines as well as planning experiments with Korea-4GSR.