A ‘‘scalable model’’ test bed using a reduced version of an ITER beam source has to allow tests of not only the source, but all the important aspects of the system at levels that make scaling to a full injector credible. The performance required from such a test bed has been carefully considered, and the European Community (EC) version of a test bed and beam source is described. The ‘‘engineering’’ of this design has been entered into in sufficient depth to allow all the problem areas to be identified, and solutions proposed.