Closely spaced, aligned grids in vacuum tubes

Closely spaced, fine-mesh, double grid systems were tested in a parallel-plane arrangement for their electrical and electron-optical properties. The grids maintain adequate control of heavy currents with virtually negligible interception. The scattering introduced by the combined grid system is quite low and decreases with closeness of cathode and grid spacings, fineness of mesh, and increase of current. Similar results can be achieved with a single grid coated on the cathode side with a thin insulating layer.