Parallax Research, Inc. proposes to develop an Ultra-High Vacuum Compatible Wavelength Dispersive X-ray Spectrometer for use on Field Emission Scanning Electron Microscopes, Transmission Electron Microscopes, Auger Spectroscopy Systems, and X-ray Photo-electron Spectroscopy Systems. We propose to build on Parallax's designs of innovative parallel beam x-ray spectrometers and incorporate new types of detectors, drive systems and internal components that offer UHV compatibility. This system will be capable of operating at energies from 100 to 10,000 eV, will feature various scanning techniques, will have the high Peak to Background ratios of WDS, and the very high energy resolution of WDS spectrometers. We propose to investigate novel fixed detector systems along with novel detector/x-ray optic combinations that will enable UHV compatibility. COMMERCIAL APPLICATIONS: There are now many FESEM systems being sold each year and we expect this to be the largest commercial market for this UHV WDS. Although Parallax Research, Inc. has managed to obtain approval from one FESEM manufacturer to place the LEXS spectrometer on its instruments, others are still very skeptical of WDS due to the use of proportional counters with thin windows. This UHV compatible system would dispel those concerns and result in many sales that are now lost. Every year we have several inquiries about the use of LEXS on Auger or XPS systems and we have to decline because the LEXS is not UHV compatible. Although this is not a large market, the incremental cost of a UHV WDS is reasonable compared to the total cost of an Auger or XPS system as it would significantly increase these systems capabilities. Full development of the UHV WDS must be covered by internal Parallax Research, Inc. IR&D funds because the market is too small to interest larger companies. Once the prototype is built, development of the first sales version will be covered by internal Parallax funds with subsequent units covered by previous sales as we have done with LEXS