The High-Voltage Electrostatic Generator at the Atomic Energy Research Establishment

A 5-MV electrostatic generator of the pressurized Van de Graaff type is described. The basis of the design follows that of a recent machine built in America, and the factors leading to this design are discussed. The gas pressure chosen was up to 400 lb/in2, and the size of the pressure tank is approximately 16 ft long by 6 ft diameter. Details of the construction are given, and the results of trials are reported. The rated output of 300 ¿A was obtained and a maximum open-circuit voltage of just over 5 MV. This required the use of nitrogen-CCl2F2 mixture as insulating gas and the subdivision of the air-gap between the 30-in terminal and the pressure-vessel wall by the use of electrode shields. Using pure nitrogen and no shields the maximum voltage was little more than 2 MV. With positive terminal polarity, gas pressure in excess of 200 lb/in2 gave no improvement in open-circuit voltage. The voltage stability of the generator is discussed.