SBIR-STTR Award

X-ray absorption spectroscopy (xas) using synchrotron radiation is being developed as a unique tool for study of structure for a range of materials including materials containing low-z elements: b, c, and n. Xas, the fluorescence yield near edge spectroscopy (fynes) in particular, requires a significant reduction in the ratio of scattered to fluorescent radiation emerging from the sample. Unfortunately, just above an absorption edge the fluorescent and elastically scattered photons have similar energies and can not be electronically discriminated in the proportional detector. Recent studies indicate that for improved photon collection in fynse, it is key to use a focusing multilayer mirror analyzer. Photons arrive at near-normal incidence, are energy analyzed, reflected, and focused onto the detector. The multilayer's modest reflectivity will be offset by its large area, ability to concentrate flux and to discriminate between fluorescent and scattered light. Based upon our experience in design and fabrication of multilayer mirrors, including high performance normal incidence focusing mirrors with 2d=3641a, we believe that by the selection of optimum layer materials and sputtering parameters, it is possible to reach normal incidence reflectivity of about 10% just about the cka line. We also believe it is possible to design a curved mirror with a solid angle of collection of more than 10% of the radiation with the multilayer d-spacing changing across the mirror to meet the following condition: disinoi=const(0i)., Where di is the variable d-spacing and 0i is the variable angle of incidence.

X-ray absorption spectroscopy (XAS) is a unique toolfor the study of materials containing light elements whensynchrotron radiation is used as an excitation source. If XAS canbe extended to provide analysis of carbon, nitrogen and oxygen itwould be possible to obtain structural information from a muchbroader range of materials. For fluorescence yield near edgespectroscopy (FYNES), a promising new type of XAS, it isextremely important to reduce the ratio of scattered tofluorescent radiation emerging from the sample. Unfortunately,proportional detectors can not discriminate between fluorescentand elastically scattered photons near an absorption edge becausetheir energies are so similar. This is why a focusing multilayermirror analyzer is so important for this application. It providesa significant improvement in photon collection and, like amonochromator, selectively rejects unwanted scattered radiation.During Phase I we demonstrated a reflectivity improvement at C-Kaof greater than two times the previous state-of-the-art, and thedesign and coating of spherical mirrors with a collectionefficiency of more than 10%. Our calculations and experimentsindicate that additional significant improvements in multilayerperformance at C-Ka, N-Ka, and O-Ka are possible. In Phase II wepropose the development of multilayer coatings with substantialreflectivities at the carbon, nitrogen and oxygen K lines andoptical designs for collecting greater than 10% of the radiationemitted in 2s steradians from the sample.Potential commercial applications of the research:Successfulcompletion of Phase II would lead to the development of newmicroprobe attachments for electron microscopes and X-rayspectrometers which have improved sensitivity and flexibility foranalysis of light elements. Focusing multilayer collectors ofthis type would have an immediate market at synchrotronfacilities and analytical equipment suppliers throughout the world and a future potential market in X-ray imaging microscopes and projection Lithography systems.