Alternating-Gradient Focusing and Related Properties of Conventional Convergent Lens Focusing

Iii research on guidance of light waves for communication we are considering use of a sequence of lenses of alternately convergent and divergent types. For example, a guidance system using tubular thermal gas lenses might employ continuous flow of gas through a tube whose walls are alternately warmer and cooler than the gas within. Thus, the mechanism used to cause the focusing may have the alternating character, and the question comes to the fore -- how well can one focus with such a structure as compared to the use of a sequence of all-convergent lenses? Alternating-gradient focusing has previously been used on electron beams 1 and 011 particle accelerators. 2 The present study discovered an error in the previous determination of stability conditions and revealed some little known but interesting properties of alternating-gradient focusing. A comparison is made with conventional focusing using all-convergent lenses.