BNL, Upton, Long Island, New York
Two most widely used BPM systems (manufactured by Bergoz and Instrumentation Technologies) implement switching technique to eliminate drifts caused by change in a channel gain. High stability is achieved by an alternative routing of signals from all pick-up electrodes through the same chain. In this paper we propose a different approach of separating signals in the frequency domain, which is based on advances of digital signal processing allowing identical gains for the separate frequencies. Experimental set-up and results are presented. Practical realization of the beam position monitors is also discussed.
DESY, Hamburg
PETRA III is a high brilliant synchrotron light-source operating at 6GeV. The commissioning of the machine began in April 2009 *. In the first months of operation the Machine Protection System (MPS) ran on basic requirements to protect absorbers and vacuum chambers in the damping wiggler section and the undulator section against synchrotron light. Therefore several alarms distributed along the machine are identified and within 100us a dump command is created. The beam is dumped within 300us by switching of the rf system **. Prior the first user runs different improvements increasing the reliability and availability are planned and partly implemented in the MPS. This paper presents first commissioning results of the system and gives an overview of these new implementations as well as a more detailed discussion of some alarm conditions and the dump procedure. Additionally some key aspects of the Temperature Interlock as one major alarm-deliverer are described.
KEK, Ibaraki
Button-type beam position monitors for SuperKEKB rings have been designed. The RF characteristics such as beam response, trapped modes or wake functions have been simulated using 3-D E-M codes such as GdfidL and HFSS. The estimated instability threshold from the trapped modes was much higher than the radiation damping time. The prototype units have been tested in the prototype-antechambers installed in KEKB and KEK-PF BT line. The mechanical reliability and the beam responses are also reported.
BNL, Upton, Long Island, New York
A diffraction-limited storage ring like NSLS2 sets more stringent beam stability requirements. Due to resistive wall impedance and fast-ion effect, transverse instabilities will happen at low current (~15 mA). An active transverse feedback system has been designed to cure the betatron oscillations. The system will have a <200 us damping rate at 50 0mA to suppress the fast-ion instability, which is severe in the vertical plane due to small beam size.