A SOFT X-RAY INTERFEROMETER FOR THE MEASUREMENT OF MATERIAL OPTICAL CONSTANTS

SOFT X-RAY INTERFEROMETRY WILL DIRECTLY MEASURE THE REAL PART OF A MATERIAL'S INDEX OF REFRACTION, SATISFYING A GROWING NEED FOR ACCURATE OPTICAL CONSTANTS IN THE 8-100 A REGION. AS SYNCHROTON SOURCES IN THIS X-RAY RANGE HAVE BECOME WIDELY AVAILABLE, COMMERCIAL RESEARCH HAS MOVED INTO SOFT X-RAY MIRROR DEVELOPMENT, X-RAY LITHOGRAPHY, AND SPECTROSCOPY. BOTH THE DIRECT REDUCTION OF DATA AND THE FABRICATION OF X-RAY OPTICAL TOOLS FOR THIS RESEARCH REQUIREA DETAILED KNOWLEDGE OF SPECIFIC MATERIAL INDICES OF REFRACTION AT VARIOUS WAVELENGTHS. PRESENT INACCURACIES IN THE REAL PART OF THE INDEX OF REFRACTION HAVE, FOR INSTANCE LIMITED THE USEFULNESS OF NORMAL INCIDENCE MULTILAYER X-RAY MIRRORS. ONE CANNOT RELIABLY DESIGN LAYER THICKNESS TO OVERLAP PEAK MIRROR REFLECTIVITY WITH DESIRED X-RAY LINE SPECTRA. TWO DESIGN CONCEPTS WILL BE EVALUATED IN THIS PROPOSAL FOR A SOFT X-RAY INTERFEROMETER. THE FIRST DESIGN IS BASED UPON OUR EXPERIENCE AT KMS FUSION WITH X-RAY TRANSMISSION GRATINGS. THE GRATINGS WIIL PERFORM LIKE A CRYSTAL IN LAUE GEOMETRY, SPLITTING AND REMERGING THE X-RAY WAVEFRONT. THE SECOND DESIGN IS MORE CONVENTIONAL, BASED UPON A FRESNEL MIRROR INTERFEROMETER. WE WILL CALCULATE AND ANALYZE THE PERFORMANCE CHARACTERISTICS OF THESE TWO INSTRUMENTS, BASED UPON THE SPATIAL COHERENCE REQUIREMENTS THEY IMPOSE UPON THE SOFT X-RAY SOURCE. THE BETTER CONCEPT WILL BE CHOSEN AND DESIGNED FOR APPLICATION ON EITHER OUR KMSF SOFT X-RAY CALIBRATION FACILITY OR ON A SYNCHROTON RADIATION SOURCE. MEASURED OPTICAL CONSTANTS WILL THEN BE COMPARED DURING PHASE II TO THE MOST RECENT SUB-KEV X-RAY TABULATIONS.