Monoenergetic Cs⁺ source with increased brightness

Sequential absorption of two laser photons converts a Cs atomic beam into a "cold" Cs+ ion beam, i.e., a beam with minimal random kinetic energy [Appl. Phys. Lett. 36, 495 (1980)]. Improvements have now increased the spectral brightness by 2.7×104 times, i.e., to 2.7 A/cm 2 sr eV, and have thereby made this source practical for ion microscopy and similar experiments requiring high-brightness beams with minimal energy spread.