Installation of a pre-injection ion source-Z/M analyser system on the 5.5 MV Van de Graaff accelerator at Trombay

Abstract

A pre-injection ion source-Z/M analyzer has been installed in the 5.5 MV Van de Graaff accelerator at Bhabha Atomic Research Centre, Bombay, India and an extensive study of the factors which influence the optimum performance of the system with respect to the yield of doubly charged helium ions, was carried out utilising the ³He⁺⁺ ion beam which avoids the complications arising out of the H₂⁺ component. A suitable rf oscillator was developed utilising two 6146 tubes which can withstand the high pressure inside the tank. The performance of the accelerator with this system reduced the electron loading of the accelerating tube by a factor of two. A beam of 160 nA of He⁺⁺ ions accelerated to an energy equivalent to twice the terminal voltage has been used for some experiments. An improvement in the performance of the accelerator has also been observed in terms of the ease of operation at higher dome voltage and larger amounts of the conventional beam currents.