Device for analyzing a surface layer by means of ion scattering

Claim 1

In a cylindrical analyzer for charged particles back scattered from a target on the axis of said analyzer, said analyzer including inner and outer concentric electrically conductive tubular electrodes, the inner of said electrodes having longitudinally spaced annular entrance and exit slots for back scattered charged particles, a radial-electric field between said electrodes permitting back scattered charged particles having only a predetermined energy to exit through said exit slot to detector means therefor, the improvement comprising a passageway from the exterior of said analyzer to the interior thereof for cooperation with a primary mono-energetic ion beam source external thereto and deflection means within said analyzer to direct a primary mono-energetic ion beam through said passageway and along the axis of said analyzer for collision with the target on the axis thereof, said passageway comprising: at least two conductive radially aligned longitudinal walls between but spaced from said inner and outer electrodes and defining an acute sector shaped space therebetween, said inner and outer electrodes being absent from at least a portion of the boundary of said sector shaped space to form a passageway from the exterior of said analyzer to the interior thereof, said longitudinal walls being held at a potential between the potentials of said inner and outer electrodes.