Nuclear Techniques ›› 2016, Vol. 39 ›› Issue (5): 50102-050102.doi: 10.11889/j.0253-3219.2016.hjs.39.050102


Study on the vertical emittance for the SSRF Phase II project

LI Changliang1,2, TIAN Shunqiang1, ZHANG Wenzhi1   

  1. 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2016-02-25 Revised:2016-03-20 Online:2016-05-10 Published:2016-05-12
  • Supported by:

    Supported by the Maintenance and Upgrade Foundation of SSRF(No.1173000212)


Background: The spectral brightness is an important parameter for the synchrotron radiation light source. It is intimately associated with beam current, horizontal emittance and vertical emittance. The beam current is limited by collective effects and the horizontal emittance is decided by the lattice structure, which has almost been fixed in a machine. Reducing the vertical emittance to improve the brightness is a simple and feasible method. Other benefits such as the increase of transverse coherence and the reduction of vertical spot size can be obtained in reducing the vertical emittance. Purpose: The aim is to study the sensitivity of the vertical emittance to magnetic alignment errors and correct the vertical emittance for the Shanghai Synchrotron Radiation Facility(SSRF) Phase II project. Methods: Singular values decomposition(SVD) is used to correct the vertical closed orbit distortion(COD). Sixty skew quadrupole magnets are utilized to correct the emittance coupling with gradient descent algorithm. Results: An approximate mean of 0.06-mm vertical COD is obtained after orbit correction. The emittance coupling of each seed can be corrected below 0.5% by using 60 skew quadrupole magnets. Conclusion: If the alignment tolerances of all magnets in the SSRF Phase II project are the same as those in the currently operational SSRF storage ring, the vertical emittance is primarily determined by vertical misalignments of the sextupole magnets, and the emittance coupling can be corrected below 0.5% by using 60 skew quadrupole magnets.

Key words: SSRF Phase II project, Magnetic alignment errors, Vertical emittance, Coupling correction

CLC Number: 

  • TL594