Lawrence Berkeley National Laboratory

The MAX IV facility includes two storage rings operated at 1.5 GeV and 3 GeV. Both rings make use of a 100 MHz RF system and are designed to operate with a uniform multibunch fill pattern aswell as employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. Recently, a discussion on timing modes at the MAX IV storage rings has been initiated by the user community. This implies operating the rings with other fill patterns than the originally planned multibunch mode and therefore detailed studies of the performance of the harmonic cavities are of interest. This paper presents bunch length measurements at the 100 MHz MAX II storage ring for uniform fill patterns. The purpose of the measurements was to evaluate the employed measurement method and simulation codes for future studies of fill patterns in the MAX IV storage rings.