X-ray microprobe characterization of materials: the case for undulators on advanced storage rings

The unique properties of X rays offer many advantages over electrons and other charged particles for the microcharacterization of materials. X rays are more efficient in exciting characteristic X-ray fluorescence and produce higher fluorescent signals to backgrounds than obtained with electrons. Detectable limits for X rays are a few parts per billion and are 10-3 to 10-5 less than for electrons. Energy deposition in the sample by X rays is 10-3 to 10-4 less than for electrons for the same detectable concentration. High-brightness storage rings, especially in the 6 GeV class with undulators, will be approximately 103 brighter in the X-ray energy range from 5 keV to 35 keV than existing storage rings and provide for X-ray microprobes that are as bright as the most advanced electron probes. Such X-ray microprobes will produce unprecedented low levels of detection in diffraction, EXAFS, Auger, and photoelectron spectroscopies for both chemical characterization and elemental identification. These major improvements in microcharacterization capabilities will have wide-ranging ramifications not only in materials science but also in physics, chemistry, geochemistry, biology, and medicine