Large diameter (1ndash;2.5 mm) Tungsten filaments are now commonly found in plasma sources used on highhyphen;power neutral injectors. In many cases problems have arisen in trying to remove or replace the filaments as the component parts of the filament chuck are found to diffusion bond together. This can cause severe difficulties in the necessary routine replacement of such filaments. This paper describes a series of tests carried out with systems used in the plasma sources of the JET neutral injectors in order to find methods of eliminating this problem. A design of filament stem and connector, both elegant and simple, is described which completely avoids the problem. Also, it is shown that the use of dissimilar metals and/or antiseizure agents are effective in preventing the diffusion bonding of the filament chuck components.
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