Number 241 (Story #1), September 22, 1995 by Phillip F. Schewe and Ben Stein ELECTRON BALLS: Hans Dehmelt and his colleagues at the University of Washington have imprisoned a tiny spherical drop of 1000 electrons in an atom trap. Such a miniature single- component plasma (consisting of only negative charges without any positive charges) acts like a pointlike object with an electrical charge and mass 1000 times that of an ordinary electron. Dehmelt (206-324-2018) won a Nobel Prize for his pioneering work with atom traps and has in the past monitored single electrons and positrons for months at a time. The most serious limitation to the precision of measurements of the electron's magnetism in this "geonium" atom (an "atom" consisting of the single electron and the trap, or, in a wider sense, the whole world) is the presence of a small unknown perturbation, namely the interaction between the electron and its image charge (a sort of mirror image of itself) that it induces in the electrodes of the trap. The perturbation was too small to measure for a single electron, but became detectable in the case of the 1000-electron drop. The kilo-e, as the Washington scientists refer to their electron ball, may be useful in other research areas, such as plasma physics. (Richard Mittleman et al., 9 Oct., Physical Review Letters; journalists can obtain copies from AIP at physnews@aip.org)