A new method of improving the acceleration voltage stability of Van de Graaff accelerators

The relative energy stability of Van de Graaff type ion accelerators is typically limited to some 10^-4. An inexpensive possibility to improve this situation was developed at the Forschungszentrum Dresden-Rossendorf. The method refers to the relatively stable periodic pattern of the acceleration voltage fluctuation in such accelerators. Future values of that fluctuation can be predicted with a high degree of certainty and can taken into account in the belt generator control in spite of the belt convolution caused fundamental reaction delay. The microcontroller based implementation of a ‘‘predictive fluctuation compensation’’ improves the relative acceleration voltage short time stability by a factor of 3–6 to well below 10^-4.