An air-cooled gradient resistor column for the KFUPM 350 kV ion accelerator

An air-cooled gradient resistor column has been designed and implemented for the KFUPM 350 kV ion accelerator. The air-cooled column overcomes operational limitations on the acceleration voltages obtained with the old water-cooled column and improves on reliability and maintainability. The new column consists of five sections, each having sixteen 8 MΩ 15 W resistors connected in a series-parallel combination. Corona shields defining equipotential circular planes have been incorporated to maintain a uniform potential difference across the column sections. In order to protect the gradient column and accelerator tube against arcing, spark gaps are provided on each corona shield. The new column has been tested over the full range of 0–320 kV across the accelerator tube for extended durations without arcing. Both electrical and mechanical aspects of the new design are discussed, measurement techniques used during installation and testing are described, and performance data are given.