The Advanced Photon Source (APS) particle accumulator ring (PAR) has dual rf systems: a CW-mode fundamental rf system (RF1) operating at 9.77 MHz that accumulates multiple linac pulses into a 0.8-ns bunch, and a 12th harmonic rf (RF12) that compresses the bunch length further to 0.34 ns for injection into the booster. The RF12 capture process is critical for optimal performance of the PAR. We investigated the effects of beam loading during the RF12 capture and bunch length compression processes with both spectrum analysis and streak camera imaging. Based on these observations, a new timing scheme for the RF12 tuner and power control was implemented, which has substantially improved the performance of the PAR. We report our observation, the new timing scheme, and beam parameters after optimization.

A 352-MHz fast-ferrite rf cavity tuner, manufactured by Advanced Ferrite Technology, was high-power tested on a single-cell copper rf cavity at the Advanced Photon Source. These tests measured the fast-ferrite tuner performance in terms of power handling capability, tuning bandwidth, tuning speed, stability, and rf losses. The test system comprises a single-cell copper rf cavity fitted with two identical coupling loops, one for input rf power and the other for coupling the fast-ferrite tuner to the cavity fields. The fast-ferrite tuner rf circuit consists of a cavity coupling loop, a 6-1/8” EIA coaxial line system with directional couplers, and an adjustable 360 º mechanical phase shifter in series with the fast-ferrite tuner. A bipolar DC bias supply, controlled by a low-level rf cavity tuning loop consisting of an rf phase detector and a PID amplifier, is used to provide a variable bias current to the tuner ferrite material to maintain the test cavity at resonance. Losses in the fast-ferrite tuner are calculated from cooling water calorimetry. Test data will be presented.

Abstract The,Advanced ,Photon ,Source ,(APS) particle accumulator ring (PAR) has dual rf systems: a CW-mode fundamental,rf system,(RF1) operating at 9.77 MHz that accumulates multiple linac pulses into a 0.8-ns bunch, and a12, harmonic ,rf (RF12) that compresses ,the bunch length further to 0.34 ns for injection into the booster. The RF12 capture process is critical for optimal performance ofthe PAR. We investigated the effects of beam ,loading during the RF12 capture and bunch ,length compression processes with both spectrum analysis and streak camera imaging. Based on these observations, a new timing scheme,for the RF12 tuner and ,power ,control was implemented, which has substantially improved the performance of the PAR. We report our observation, the new timing scheme, and beam parameters after optimization.

A 352-MHz fast-ferrite tuner, manufactured by Advanced Ferrite Technology, was tested on a single-cell rf cavity at the Advanced Photon Source. Low-power rf testing was performed on the tuner-cavity combination to evaluate tuning range, bandwidth, stability, and compatibility with existing Advanced Photon Source low-level rf hardware. The test system comprises a single-cell copper rf cavity, a bipolar DC bias supply for the ferrite tuner, a water flow and temperature metering and interlock system, and a low-level rf cavity tuning loop consisting of an rf phase detector and a PID amplifier. Test data will be presented.

A parallel-klystron topology has been designed and tested at the Advanced Photon Source to supply rf power to the 7-GeV storage ring rf cavities. The rf power output of two 1.1-MW, 352-MHz rf stations is combined utilizing a 3-dB/90-degree hybrid. The two outputs of the hybrid then supply rf power to two sectors of storage-ring cavities. Feedback control loops maintain the proper output phase and amplitude from each rf station at the combining hybrid input ports so that the correct power balance and phase relationship is maintained between the two sectors of storage ring cavities. Downstream mechanical phase shifters correct for phase changes when only one of the two rf stations is used in single-ended mode. EPICS is utilized to monitor and control the parallel-klystron system

An analog RF gap voltage regulation system has been designed and built at Argonne National Laboratory to maintain constant total storage ring RF gap voltage, independent of beam loading and cavity tuning effects. The design uses feedback control of the klystron mod-anode voltage to vary the amount of RF power fed to the storage ring cavities. The system consists of two independent feedback loops, each regulating the combined RF gap voltages of eight storage ring cavities by varying the output power of either one or two RF stations, depending on the mode of operation. It provides full operator control and permissive logic to permit feedback control of the RF system output power only if proper conditions are met. The feedback system uses envelope-detected cavity field probe outputs as the feedback signal. Two different methods of combining the individual field probe signals were used to generate a relative DC level representing one-half of the total storage ring RF voltage, an envelope-detected vector sum of the field probe RF signals, and the DC sum of individual field probe envelope detector outputs. The merits of both methods are discussed. The klystron high-voltage power supply (HVPS) units are fitted with an analog interface for external control of the mod-anode voltage level, using a four-quadrant analog multiplier to modulate the HVPS mod-anode voltage regulator set-point in response to feedback system commands