UPGRADE OF LOW LEVEL RF FEEDBACK SYSTEM FOR PLS STORAGE RING

摘要

The upgrade of the low-level RF feedback system for the PLS storage ring is now in progress, which will be finished in Dec. 2001. The previous system has single loop of amplitude and phase control each, which stabilizes the variations due to the klystron high voltage power supply. And the VME for the RF system measures the cavity gap voltage and compares with the setting voltage, and gives a control signal to the amplitude loop, which causes a large variation of the gap voltage. The new system employs two pairs of amplitude and phase control loops. One is for the variation of the klystron high voltage power supply, called the inner loop, which is a fast loop with the bandwidth of about 1 kHz. The other is for the gap voltage and phase variation in the RF cavity, which is a slow loop with the bandwidth of about 100 Hz. The new system incorporates MM type modules, which enable the easy maintenance of each module, and provides a large number of diagnostic points for the RF and control signal monitoring. In this paper the detailed description of the new system will be described together with the performance test results.