WE PROPOSE TO DEVELOP APERIODIC MULTILAYER COATINGS HAVING HIGH REFLECTANCE AT NORMAL INCIDENCE OVER A BROAD SPECTRAL BAND IN THE EXTREME ULTRAVIOLET (EUV) FOR SPECTROSCOPY OF THE SOLAR ATMOSPHERE. THE SPECTRAL REGION FROM APPROXIMATELY 17 NM TO 35 NM CONTAINS A NUMBER OF SCIENTIFICALLY IMPORTANT EMISSION LINES EMANATING FROM THE SOLAR CORONA AND TRANSITION REGION. THE REALIZATION OF BROADBAND EUV MULTILAYER COATINGS HAVING HIGH REFLECTANCE OVER ALL OR PART OF THIS BAND WILL ENABLE THE CONSTRUCTION OF HIGH-RESOLUTION SPECTROMETERS BASED ON NORMAL-INCIDENCE GRATINGS HAVING WIDE WAVELENGTH COVERAGE AND SENSITIVITY THAT IS SUFFICIENT TO SUPPORT THE EXPOSURE TIMES AND CADENCES NEEDED FOR FUTURE NASA SOLAR PHYSICS AND SPACE WEATHER MISSIONS. THE HINODE/EIS INSTRUMENT TARGETED THE SPECTRAL BAND FROM 25 NM TO 29 NM USING A NORMAL-INCIDENCE GRATING COATED WITH A PERIODIC SI/MO MULTILAYER. APERIODIC COATINGS DEVELOPED IN RECENT YEARS CAN NOW BE DESIGNED TO PROVIDE HIGH REFLECTANCE OVER A MUCH WIDER RANGE OF WAVELENGTHS. FURTHERMORE NEWLY DEVELOPED MG- AND AL-BASED MULTILAYER COATINGS HAVE BEEN DEMONSTRATED TO HAVE SIGNIFICANTLY HIGHER REFLECTANCE THAN SI/ MO MULTILAYERS IN THIS SPECTRAL REGION. WE THUS PROPOSE TO DEVELOP NEW MG- AND AL-BASED APERIODIC MULTILAYERS HAVING NEARLY FLAT RESPONSE OVER A MUCH WIDER WAVELENGTH BAND THAN CAN BE CAPTURED USING PERIODIC MULTILAYERS THEREBY ENABLING SIGNIFICANT INCREASES IN WAVELENGTH COVERAGE IN FUTURE SPECTROSCOPY INSTRUMENTS. THE PROPOSED RESEARCH WILL FOCUS ON SEVERAL NEW MG- AND AL-BASED MULTILAYER MATERIAL SYSTEMS THAT HAVE BEEN DEVELOPED OVER THE PAST DECADE INCLUDING THE THREE-MATERIAL SYSTEMS ZR/CO/MG SIC/MO/AL AND B4C/MO/AL. GOOD EUV PERFORMANCE AND STABILITY HAVE BEEN DEMONSTRATED ALREADY WITH PERIODIC (I.E. NARROW-BAND) COATINGS COMPRISING EACH OF THESE MATERIAL COMBINATIONS. WE WILL DEVELOP APERIODIC BROAD-BAND COATINGS USING THE SAME MATERIAL COMBINATIONS FOLLOWING A SYSTEMATIC EXPERIMENTAL WORK PLAN. CANDIDATE COATINGS WILL BE DEPOSITED BY MAGNETRON SPUTTERING AND COATING MICROSTRUCTURE STRESS ROUGHNESS EUV REFLECTANCE STABILITY AND OTHER RELEVANT PROPERTIES WILL BE FULLY CHARACTERIZED. THE EXPERIMENTAL WORK WILL BE CONDUCTED USING ESTABLISHED FACILITIES AND METHODS AND A SYSTEMATIC ITERATIVE APPROACH WILL BE FOLLOWED TO OPTIMIZE COATING PERFORMANCE. THE ANTICIPATED OUTCOME OF THE PROPOSED RESEARCH IS THE REALIZATION OF NEW BROAD-BAND MULTILAYER COATINGS OPERATING IN THE 17 35 NM BAND THAT WILL ENABLE THE CONSTRUCTION OF HIGH RESOLUTION SPECTROSCOPY INSTRUMENTS TARGETING THIS REGION OF THE EUV IN SUPPORT OF FUTURE NASA MISSIONS.