Effect of tune modulation on the dynamic aperture of HIRFL-CSRm

The tune modulation due to power supply ripple of magnets has a strong destabilizing effects on non-linear motion. In order to investigate this effect on the dynamic aperture of HIRFL-CSRm, a tracking study was done. The impacts of quadrupole power supply ripple were modelled by modulating the linear Betatron oscillation tunes and the dynamic aperture was calculated through tracking particle one million turns in HIRFL-CSRm lattice. It turned out that the dynamic aperture decreased roughly linearly with the amplitude of the tune modulation. The dependence of the dynamic aperture on the frequency of the modulation was also studied, but it was relatively weak.