  With advances in accelerator science and technology in the recent decades,
the accelerator community has focused on the development of next-generation
light sources, for example the diffraction-limited storage rings (DLSRs), which
requires precision control of the electron beam energy and betatron tunes. This
work is aimed at understanding magnet hysteresis effects on the electron beam
energy and lattice focusing in the circular accelerators, and developing new
methods to gain better control of these effects. In this paper, we will report
our recent experimental study of the magnetic hysteresis effects and their
impacts on the Duke storage ring lattice using the transverse feedback based
precision tune measurement system. The major magnet hysteresis effects
associated with magnet normalization and lattice ramping are carefully studied
to determine an effective procedure for lattice preparation while maintaining a
high degree of reproducibility of lattice focusing. The local hysteresis
effects are also studied by measuring the betatron tune shifts resulted from
adjusting the setting of a quadrupole. A new technique has been developed to
precisely recover the focusing strength of the quadrupole by returning it to a
proper setting to overcome the local hysteresis effect.
