High Performance Cryogenic X-ray Spectrometer for Chemical Analysis of Dilute Samples

Many critically important biological processes ¿ such as oxygen production during photosynthesis, nitrogen fixation, biogenic hydrogen production, and the evolution of the bioavailability of heavy metal contaminants ¿ are associated with changes in the oxidation state of metal ions. The most effective technique for studying the chemistry of these dilute systems is synchrotron-based, fluorescence-detected, X-ray absorption spectroscopy (XAS), which is typically performed at such DOE facilities as the Stanford Synchrotron Radiation Laboratory and the Lawrence Berkeley Laboratory Advanced Light Source. This project will develop a prototype X-ray spectrometer that will incorporate a high-efficiency, high-rate, high-resolution, superconducting X-ray detector that is cooled to its operating temperature by a user-friendly and economical cryostat. The first goal is to develop a new generation of superconducting tunnel junctions (STJs), with absorber materials and device geometry optimized to improve energy resolution, reduce spectral artifacts, and increase quantum efficiency for increased sensitivity and dynamic range. The second goal is to develop a self-contained helium-3 sorption cryostat that will be compact, nonmagnetic, reliable, economical, and easy to operate. Commercial Applications and other Benefits as described by the awardee: The Advanced Detector Group at Lawrence Livermore National Laboratory routinely receives more requests than they can accommodate for collaborations by scientists who want to exploit the unique capabilities of their superconducting spectrometer. This project addresses this deficiency by enabling the first commercial supply of STJ detectors and affordable cryostats. The estimated market for X-ray detectors is on the order of 100 million dollars annually. Improved STJ detectors also may have applications in scanning electron beam nano-analysis tools for the integrated circuit industry.