X-ray polarization measurement of the Beamline 4B7 of Beijing synchrotron radiation facility using a PET crystal Jia-Min Yang a,Ã , Xin-Shi Gan a,c , Ming-Qi Cui b , Yang Zhao a , Tuo Zhu a , Yi-Dong Zhao b , Li-Juan Sun b , Lei Zheng b , Fen Yan b , Zhi-Min Hu a , Min-Xi Wei a , Ji-Yan Zhang a , Rong-qing Yi a a Research Center of Leaser Fusion, Chinese Academy of Engineering Physics, P.O. Box 919-986, Mianyang 621900, China b Institute of High Energy Physics, Chinese Academy of Science, Beijing 100049, China c School of Physical Science and Technology, Sichuan University, Chengdu 610065, China article info Article history: Received 31 July 2009 Received in revised form 26 December 2009 Accepted 26 December 2009 Available online 11 January 2010 Keywords: X-ray polarization Synchrotron radiation Crystal abstract An experimental method has been developed to measure the X-ray polarization of the Beamline 4B7 on Beijing Synchrotron Radiation Facility in the X-ray energy range 2100–5600 eV by using a PET crystal diagnostic system and rotating the system around the incident X-ray beam by 901. The experimental results show that the measured X-ray polarization is more than 0.88 in the photon energy range 2100–3600 eV with maximum of 0.99 at 2707.3 eV, and quickly decreases to about 0.38 at 4719.2 eV with photon energy increasing from 3600 to 4719.2 eV, then it keeps almost constant as the photon energy increases further to 5600 eV. & 2010 Elsevier B.V. All rights reserved. 1. Introduction Polarized X-rays have been applied in many experiments, such as X-ray magnet circular dichroism [1,2], spin-polarization photoelectron diffraction [3], X-ray Faraday effect [4], diffracted magneto-optic Kerr effect [5], X-ray phase retarder [6] and auger electron emission spectroscopy, etc. Due to its high brilliance and unique polarization property synchrotron radiation (SR) has been extensively used in studies in the fields of biology, chemistry, physics and material science [7]. In some of these studies, the polarization of the X-rays is a basic parameter. Therefore, accurate measurement of polarization of X-rays from beamlines of synchrotron radiation facilities is important. In the soft X-ray region, various multilayer polarization elements have been well developed to measure the X-ray polarization. Using Mo/Si multilayer mirrors as the polarizer and the analyzer Kimura et al. [8] measured the polarization of 12.8 nm SR emitted from a helical undulator and monochromatized by a grating monochromator at the Photon Factory. Dhez [9] measured the degrees of linear polarization of SR for the ACO storage ring at 30.4 and 15.4 nm separately using a Hf/Si multilayer polarizer and a Nb/Si multilayer polarizer. In China, Sun et al. [10] used Cr/C multilayer to study the polarization characteristics of the Beamline 3W1B of Beijing Synchrotron Radiation Facility (BSRF), which covers the energy range 100–1500 eV, and Zhu [11] has also studied the beamline theoretically and experimentally. However, the interface roughness and/or inter-diffusion in the multilayer structure and the surface roughness of the substrate significantly influence its optical properties such as reflectivity. These optical and structural errors result in the degradation of the polarizing performance of the multilayer-type polarization elements [12].Therefore, multilayer is not suitable as polarization element in the kilo-electron-volt X-ray region. In the energy region from approximately 2.6 keV to several 10 keV, crystal-type polarization elements such as silicon and diamond perfect crystals in Bragg and Laue geometry have been developed [6,13] and utilized for X-ray polarization studies [1,14]. For example, the polarization of X-rays emitted from bound–bound transitions in a highly ionized He-like ion was measured with a curved Ge crystal for Bragg angles about 451 [15]. Shlyaptseva et al. [16,17] studied the polarization properties of dielectronic satellite lines of Li- and Be-like Fe ions excited by an electron beam using a LiF crystal. Wang et al. [18] developed a polarized spectrometer with PET crystals to measure the X-ray polarization spectrum from laser-produced plasmas. However, these polarized spectrometers use two crystals in two directions perpendicular each other. Therefore, each crystal measured the X-ray spectrum in one direction and the spectra in two directions were assumed to be same because the X-ray source emits in 2p solid angle. As the divergence of synchrotron radiation is very small the polarization of the synchrotron radiation can not be measured using these polarized spectrometers. ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A 0168-9002/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2009.12.076 Ã Corresponding author. E-mail address: yjm70018@my-public.sc.cninfo.net (J.-M. Yang). Nuclear Instruments and Methods in Physics Research A 615 (2010) 100–104