Author: Streun, A.
Paper Title Page
Use of Reverse Bending Magnets in MBA Lattices  
  • A. Streun
    PSI, Villigen PSI, Switzerland
  Including reverse bending magnets further reduces the equilibrium emittance of multi-bend achromat (MBA) lattices through decoupling of dispersion and horizontal beta function. This coupling is a shortcoming of the classical theoretical minimum emittance (TME) cell preventing it from reaching lowest emittance at realistic, moderate focusing conditions. Rather small deflection angles of the reverse bends, in the order of 10% of the unit cell bending angle, are usually sufficient, and realized through down-feed by displacing the horizontally focusing quadrupoles of the unit cell by a small amount towards the storage ring inside. Reverse bends are indispensable in particular to enable emittance reduction from dipoles with longitudinal field variation, since these require very small dispersion at the central region of highest field strength. In past decades reverse bends were employed occasionally for isochronous lattices or to enhance damping. Now they are becoming an integral component of low emittance MBA lattices.  
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