A method of making a grid

An accelerator grid for a particle accelerator is formed by providing a single piece of copper to form a block as illustrated. This can either be machined from a single sheet or can be formed by electro-depositing copper on a stainless steel master from which it is subsequently removed. The grooves and the inlet and outlet plenum chambers are filled with a very low melting point alloy e.g. of bismuth, lead, tin and cadmium. After machining the surface flat a further layer of copper is deposited over the surface so as to enclose the cavities filled with the alloy. The apertures are then drilled and finally the alloy is removed by melting. In use a potential difference is applied between a source of ions to be accelerated and the illustrated grid so as to accelerate the ions towards the latter. Some of the ions pass through the apertures and others are incident on the grid. The resulting heat is removed by a coolant such as water which is forced through the ducts. (author)