Use of a slit feedback system based on a proportional-integral controller to improve long- and short-term voltage stability during microbeam experiments

Abstract

We developed a terminal voltage stabilization system (TVSS) to improve the high-voltage properties of the Dynamitron accelerator in microbeam experiments. However, a voltage deviation of ca. 1 Hz increased gradually over time because of power variation in the oscillation tube. The deviation was caused by feedback phase delay and the low sensitivity of the generating voltage meter (GVM). By optimizing the feedback parameters, the voltage deviation was greatly reduced, even when old oscillation tubes were used. The optimum parameters were strongly dependent on tube conditions. By combining gain-adjustable proportional-integral (PI) and proportional (P) circuits in the feedback system, the parameters can be changed, even during accelerator operation, and remain adjustable over a long period. The low sensitivity of the GVM prohibits voltage regulation at [Formula: see text][Formula: see text]100 V. We developed a slit feedback system to compensate for this weakness. The voltage ripple became ca. [Formula: see text] at [Formula: see text][Formula: see text]1 Hz even using old oscillation tubes. Although the ripple [Formula: see text][Formula: see text]1 Hz was difficult to validate because of vibration of the high-voltage terminal, the ripple at [Formula: see text][Formula: see text]10 Hz was greatly reduced with use of this mode. The modified TVSS is now used routinely during microbeam experiments.