Abstract

We have developed a method to image a beam of neutral atoms (chiefly usable for alkalis) that is essentially an extension to two dimensions of the usual hot wire method of detection. The beam of neutral atoms first passes through a a highly transparent, positively charged grid and then impinges on a heated grid of electroformed nickel with lower transparency and at ground potential. Atoms with ionization potential less than the work function of Ni that strike the heated grid are ionized at its surface and are then pushed through it by the 250-V/cm field produced by the voltage on the first grid. The ions are then accelerated through ~700 V to a pair of multichannel plates (MCPs) ~3 mm away where the single charged ion signal is amplified. The output electrons from the MCPs are accelerated by 1.7 kV to a phosphor screen ~3 mm away that glows when the electrons strike it. The phosphor screen is viewed by a TV camera whose output goes to a frame processor in a PC. The system has been used for studying transverse laser cooling (optical collimation) of a Rb beam done with diode lasers.

© 1989 Optical Society of America