Wavelength dispersive spectrometers (WDS) are widely used in both scanning electron microscopes and scanning transmission electron microscopes for x-ray elemental analysis and mapping. The WDS systems are typically used to detect x-rays in the 100 eV - 2000 eV energy range, for chemical analysis of elements Be through P. Despite the excellent energy resolution of the WDS systems, they rely on gas flow proportional counters for detection of x-rays from the diffractor, which pose a serious problem in terms of the compatibility with the ultra-high vacuum (UHV) of the microscope. For the detection of very low energy x-rays, the gas proportional counter must have an extremely thin entrance window, which is permeable to the gas in the proportional counter, such that the proportional counter gas slowly leaks into the UHV chamber of the microscope. The newer generation field emission microscopes will not be able to tolerate the gas from the proportional counter leaking into the UHV of the microscope. In this project, we propose to develop a high performance solid state x-ray detector that will be compatible with the UHV environment, and will offer a more reliable, low cost alternative to replace the gas proportional counters in electron microscopes. COMMERCIAL APPLICATIONS: The commercial market for improved WDS detectors to replace the gas proportional counters on electron microscopes is as large as the market for the electron microscopes themselves. There are 1000's of electron microscopes sold each year, by companies such as Hitachi, JEOL, and LEO, as well as smaller microscope companies. In addition, the new WDS detectors to be developed here can be inserted as replacements for existing gas proportional counters in current electron microscopes already in use. Radiant Detector Technologies already has the production and marketing capabilities to commercialize this as a product, and will invest its own internal money, as well as seek outside investment money if necessary, to bring this product to the market. Radiant Detectors has experience commercializing radiation detector products, as is demonstrated by our successful sales and marketing of our VortexTM and Radiant200TM detector products (see also www.radiantdetectors.com)