The IUCF cooler ring betatron tune modulation system

To meet accelerator physics studies requirements for high-frequency modulation of a synchrotron quadrupole field, a modulation system was developed to allow accurate field control inside the vacuum chamber for frequencies up to 3 kHz. Limitations in directly modulating the DC bias current supply led to the motivation for a specialized system. The system consists of a computer-controlled function generator, a 300-V pk-pk/800 mA pk-pk power amplifier, a quadrupole field pickup coil, and an AC isolation subsystem to restrict modulation to a single quadrupole. The power amplifier may be run in constant AC current mode, constant external AC field mode. Responses of the laminated iron quadrupole and stainless steel beampipe to such modulation are discussed. Interconnection of the various system elements (multiwinding quadrupoles and DC bias supplies) required an AC isolation subsystem. This subsystem synthesizes a high AC impedance while maintaining negligible DC insertion impedance, minimizing DC power losses and isolation component physical size. System performance and typical beam responses are summarized.<>