Suppression of Amplitude dependent closest tune approach and first tests of the ADT as an AC-dipole (MD 1412)

The amplitude detuning has been observed to decrease significantly as the horizontal and vertical tunes are approaching each other. The measured tune split (Qₓ −Qᵧ) versus amplitude was several times bigger than what can be explained with linear coupling during the non-linear MD in 2012 [1]. This effect is potentially harmful since it might cause a loss of Landau damping, hence giving rise to instabilities. In this MD we validated the findings in the MD from 2012 and demonstrated the possibility to mitigate this effect through having opposite polarity of the focusing and defocusing octupoles (MOD and MOF). The amplitude dependent dependent closest tune approach was also measured with the AC-dipole and gave unexpected results. A first test of using the ADT as an AC-dipole was also performed.