BNL, Upton, Long Island, New York
Throughout RHIC Run-9 (polarized protons) and Run-10 (gold), numerous modifications to the Baseband Tune (BBQ) system were made. Hardware and software improvements resulted in improved resolution and control, allowing the system to overcome challenges from competing 60 Hz mains harmonics, other spectral content, and other beam issues. Test points from the Analog Front End (AFE) were added and connected to diagnostics that allow us to view signals, such as frequency spectra on a Sr785 dynamic signal analyzer, in real time. Also, additional data can now be logged using a National Instruments DAQ. Development time using tune feedback to obtain full-energy beams at RHIC has been significantly reduced from many ramps over a few weeks, to just a few ramps over several hours. For many years BBQ was an expert-only system, but the many improvements allowed BBQ to finally be handed over to the Operations Staff for routine control.
BNL, Upton, Long Island, New York
A new microwave link has been developed for the longitudinal stochastic cooling system, replacing the fiber optic link used for the transmission of the beam signal from the pickup to the kicker. This new link reduces the pickup to kicker delay from 2/3 of a turn to 1/6 of a turn, which greatly improves the phase margin of the system and allows operation at higher frequencies. The microwave link also introduces phase modulation on the transmitted signal due to variations in the local oscillators and time of flight. A phase locked loop tracks a pilot tone generated at a frequency outside the bandwidth of the cooling system. Information from the PLL is used to calculate real-time corrections to the cooling system at a 10 kHz rate. The design of the pilot tone system is discussed and results from commissioning are described.
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.