In the scope of the Facility for Antiproton and Ion Research (FAIR) project, several new synchrotrons and storage rings will be built. The existing heavy-ion synchrotron SIS18 has to be upgraded to serve as an injector for the FAIR accelerators. All this imposes new requirements on the low-level rf (LLRF) systems. These requirements include fast ramping modes, arbitrary ion species, and complex beam manipulations such as dual-harmonic operation, bunch merging/splitting, barrier bucket operation, or bunch compression. In order to fulfill these tasks, a completely new and unique system architecture has been developed since 2002, and the system is now used in SIS18 operation. The presentation of this novel system architecture is the purpose of this paper. We first describe the requirements and the design of the LLRF system. Afterwards, some key components and key interfaces of the system are summarized followed by a discussion of technological aspects. Finally, we present some beam experiment results that were obtained using the new LLRF system.
Influence of the rf excitation in a capacitively coupled filamentless broad ion beam source with radial electrode configuration on the ion beam properties has been examined. Ion energy distribution was measured by use of a retarding field energy analyzer connected to a computer controlled data acquisition system. Influence of working conditions on the average ion energy and on the ion energy spread in the beam is described. Energy spread has typical values between 8 and 25 eV. Average ion energy can change due to variations of ion source working conditions (at constant extraction voltages) up to 60 eV. Increase of both the average ion energy and ion energy spread is observed with increasing rf power coupled to the plasma (20–100 W). This correlates to the increasing amplitude of plasma floating potential oscillation. Average ion energy decreases with increasing magnetic induction (0–75 mT) and with increasing pressure in the vacuum chamber (2×10−4–1.8×10−3 mbar) due to decreasing cathode oscillation amplitudes. Average ion energy decreases with increasing distance from the broad beam axis because of chromatical and spherical aberrations of the source extraction optics. Multiple peaks in the ion energy spectrum are observed. Their occurrence can be explained by charge exchange effects in the rf oscillating plasma sheath.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.