Characteristics of the Synchrotron Radiation of Fourth-Generation Storage Rings
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Characteristics of the Synchrotron Radiation of Fourth-Generation Storage Rings Jinjoo Ko Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea and Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
Bonghun Oh, Seunghwan Shin and Jaeyu Lee∗ Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea
Gyeongsu Jang and Moohyun Yoon Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea (Received 8 January 2020; revised 28 February 2020; accepted 28 February 2020) Fourth-generation storage rings (4GSR) based on multi-bend achromat (MBA) lattices promise to deliver stable X-ray beams with higher brightness and coherence than existing third-generation light sources. The basic ingredient in achieving higher brightness is a further reduction of the electron beam emittance in storage rings dedicated to light sources. These 4GSR lattices can lead to 1 to 2 orders of magnitude reductions in the beam emittance by employing a MBA, where many dipoles per cell are used to keep the dispersion function low inside the dipoles. Moreover, these low emittance beams are transported to the beam-line through the insertion device or center-bend, which is a permanent magnet with a 2 T magnetic field. In this paper, we will introduce the characteristics of the synchrotron radiation of 4GSR compared to present third-generation sources, PLS-II. Keywords: Fourth-generation storage rings, Synchrotron radiation, Source distribution DOI: 10.3938/jkps.77.363
I. INTRODUCTION Electron storage rings are the most promising and powerful sources of high-brightness X-ray photon beams these days. Their capabilities have been improved remarkably by realizing the multiple-bend achromat (MBA) lattice [1–5]. The beam emittance characterizing the machine performance decreases to a few tens of picometers. Many projects for the new storage ring, which adopts a MBA lattice, are ongoing worldwide. However, not much effort has been made to analyze the synchrotron radiation performances of low-emittance storage rings. The performance of a light source is defined by many parameters. Among them, we have three important characteristics of synchrotron radiation: the total flux, the brilliance (or brightness), and the transverse coherence, which are directly related to the number of photons to be actually delivered to the sample. In addition, the photon distribution at the source point based on the Wigner function represents the source dispersion in the horizon∗ E-mail:
tal and vertical phase-space. We are studying a variety of lattices for the fourthgeneration storage ring (4GSR). Among them, this paper presents the synchrotron radiation characteristics based on a lattice with an electron energy of 4 GeV and a natural emittance of 58 pm-rad. We also compare them to current third-generation storage ring, PLS-II, for various light sources. We optimize the betatron function and the insertion device (ID) parameters in search of be
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