Method for increasing the aperture of space focusing lenses

There are limitations in the aperture achievable from the use of molecular beam space focusing lenses. It is shown that by a system of lenses in series (or by a lens with varying strength along its axis) the aperture can be made substantially larger than in the case of a single lens. A method for the design of such a system is given. The use of this method to design a collimator is presented. More powerful lens systems can enhance the sensitivity, signal-to-noise ratio, and resolution of maser beam, molecular beam resonance, and state selecting scattering apparatus that commonly employ these lenses.