Focused high‐intensity proton beam from a lithium source by using an E×B stigmatic selector

This article describes the design and operation of a system that produces a high‐intensity proton beam. The system consists of a lithium proton source and an E×B stigmatic selector that produces a stigmatic proton beam at the mass focus. The protons are produced by bombarding electrons against a lithium surface. These protons are accelerated toward a special tilted‐pole Wien filter (stigmatic selector), which eliminates astigmatism in the proton beam at the mass focus. The stigmatic E×B selector was also tested with electron beams, and their astigmatism was also eliminated. A classical E×B Wien filter with parallel poles (astigmatic selector) was used for comparison. The experimental spectral curves of both the proton current and the electron current, each using both types of selectors, are shown.