Abstract A retarded field electron diffraction spectrometer is disclosed which includes an electron gun for directing substantially monoenergetic electrons onto the surface to be examined of a target to produce scattered electrons from such surface. A spherical retarding grid structure is concentrically disposed of the target in the space between the target electrode and a concentric spherical fluorescent screen. A retarding potential applied to the retarding grid permits only those target scattered electrons having a potential greater than the potential of the retarding electrode to reach the fluorescent screen. The retarding grid electrode has grid openings defining electron passageways having a characteristic diameter less than three times the characteristic length thereof to improve the uniformity of the retarding field. A spherical shield grid electrode is concentrically disposed of and has a radius within the range of 0.3 to 0.8 of that of the retarding grid to enhance the resolution of the spectrometer.
The apparatus of claim 1 wherein said means forming a curved grid structure is a retarding grid electrode having grid openings defining electron passageways therethrough with characteristic diameters less than three times the characteristic lengths thereof whereby the retarding field potential is made substantially uniform across the electron passageways through said retarding grid for enhancing the resolution of the spectrometer.
Claim 2
Dependent Claim
39 words
The apparatus of claim 2 wherein said retarding field grid electrode comprises a pair of concentrically disposed grids with the spacing between said retarding field grids being substantially greater than the characteristic diameter of the apertures in said grids.
Claim 3
Dependent Claim
69 words
The apparatus of claim 1 wherein said means for directing a stream of monoenergetic electrons onto the surface of the target includes an elongated conductive tube for containing an electron gun assembly, said tube projecting radially through aligned apertures in said screen and retarding grid electrode structures toward the target, and the inner end of said gun tube terminating substantially at the inner concave surface of said retarding grid.