Number 29 (Story #5), April 11, 1991 by Phillip F. Schewe and Ben Stein SYNCHROTRON LIGHT SOURCES now under construction will greatly expand research performed with x-ray photons. Using wigglers or undulators, these new facilities maximize the synchrotron radiation shed by accelerated electrons or positrons. The European Synchrotron Radiation Facility (to be finished by 1994) in Grenoble, France, using 6-GeV electrons, will produce radiation that peaks at a wavelength of 0.86 angstroms. At the Advanced Photon Source at Argonne National Lab (scheduled for completion in 1995) positrons at an energy of 7 GeV will provide x rays in the energy range 4-40 keV. The price of the APS is $456 million, comparable to that of the ESRF. The third hard x-ray machine under construction is the Japanese SPring-8, which uses 8-GeV electrons; it will be completed in 1998. (Physics Today, April 1991.)