Timing Modes for the MAX IV Storage Rings

Abstract: The MAX IV facility includes two storage rings, operated at 1.5 and 3 GeV energy, for the purpose of producing high-brilliance synchrotron radiation for users. The 1.5 GeV ring replaces the previous MAX II and MAX III storage rings as a source of UV and soft X-rays, whereas the 3 GeV ring is optimized for hard X-rays. The 3 GeV ring is the first of a new generation of synchrotron light storagerings which employs multibend achromat lattices to achieve ultralow emittancesof a few hundred pm rad or below. Both rings were designed to operate with a uniform, multibunch fill pattern utilizing a 100 MHz RF system, resulting in a light repetition rate of 100 MHz. However, the MAX IV user community has initiated a discussion about timing modes at the rings and several research areas have been identified that require kHz - few MHz repetition rates. At many synchrotron light storage rings this is currently achieved by operating fill patterns with gaps of sufficient length for beamline choppers or gated detectors. This is not favorable for the MAX IV storage rings since they employ passive harmonic cavities to damp instabilities, increase Touschek lifetime, reduce heating of vacuum components and conserve the emittance at high bunch charge by lengthening the electron bunches. Studies at other storage rings have shown that fill patterns with gaps reduce the achievable bunch lengtheningand can drastically decrease the effectiveness of the harmonic cavities. This is of special concern for ultralow emittance rings since they have more demanding constraints to achieve stable beam, sufficient Touschek lifetime, acceptable heat load and low emittance at high bunch charge. This thesis presents research conducted to study possibilities of serving timing users that demand other light repetition rates than provided by the RF system at the MAX IV storage rings andother similar machines. Operation with fill patterns with gaps are studied as well as two methods, Pulse Picking by Resonant Excitation (PPRE) and Pseudo-Single-Bunch (PSB), that have the potential to serve timing and high-brilliance users simultaneously without requiring gaps in the fill pattern.