WE PROPOSE A COMPREHENSIVE EXPERIMENTAL RESEARCH PROGRAM WHOSE TWO MAIN GOALS ARE (A) TO IMPROVE THE PERFORMANCE OF HARD XRAY MULTILAYER COATINGS AND (B) TO DEVELOP A HIGH-THROUGHPUT METHOD TO CORRECT MID-FREQUENCY SURFACE ERRORS IN THIN-SHELL MIRROR SUBSTRATES. ACHIEVING THESE GOALS WILL ENABLE THE COST-EFFECTIVE CONSTRUCTION OF LIGHT-WEIGHT HIGHLY-NESTED X-RAY TELESCOPES HAVING GREATER OBSERVATIONAL SENSITIVITY WIDER ENERGY COVERAGE AND HIGHER ANGULAR RESOLUTION THAN CAN BE ACHIEVED AT PRESENT. THE REALIZATIONOF THIS TECHNOLOGY WILL THUS BENEFIT THE DEVELOPMENT OF A VARIETY OF EXPLORER-CLASS NASA X-RAY ASTRONOMY MISSIONS NOW BEING FORMULATED FOR BOTH THE SOFT AND HARD X-RAY BANDS AND WILL ENABLE THE CONSTRUCTION OF FUTURE FACILITY-CLASS X-RAY MISSIONS THAT WILL REQUIRE BOTH HIGH SENSITIVITY AND HIGH RESOLUTION. BUILDING ON THE SUCCESS OF OUR PREVIOUS APRA-FUNDED RESEARCH WE PLAN TO INVESTIGATE NEW THIN-FILM GROWTH TECHNIQUES NEW MATERIALS AND NEW APERIODIC COATING DESIGNS IN ORDER TO DEVELOP NEW HARD X-RAY MULTILAYERSTHAT HAVE HIGHER X-RAY REFLECTANCE WIDER ENERGY RESPONSE LOWER FILM STRESS AND GOOD STABILITY AND THAT CAN BE PRODUCED MORE QUICKLY AT REDUCED COST. ADDITIONALLY WE PROPOSE TO BUILD UPON OUR EXTENSIVE EXPERIENCE IN SUB-NM FILM-THICKNESS CONTROL USING VELOCITY MODULATION AND MASKED DEPOSITION TECHNIQUES AND IN THE RECENT DEVELOPMENT OF LOW-ROUGHNESS LOW-STRESS FILMS GROWN BY REACTIVE SPUTTERING IN ORDER TO DEVELOP NEW METHODS FOR CORRECTING MID-FREQUENCY SURFACE ERRORS IN THIN-SHELL MIRROR SUBSTRATESUSING BOTH DIFFERENTIAL DEPOSITION AND ION-BEAM FIGURING EITHER ALONE OR IN COMBINATION. THESE TWO SURFACE-CORRECTION TECHNIQUES ALREADY BEING USED FOR SUB-NM FIGURING OF PRECISION OPTICS IN A VARIETY OF DISCIPLINES INCLUDING DIFFRACTION-LIMITED EUV LITHOGRAPHY ANDSYNCHROTRON APPLICATIONS REQUIRING SUB-MICRON FOCUSING ARE IDEALLY SUITED FOR CONTROLLING MM-SCALE SURFACE ERRORS IN THE THIN-SHELL SUBSTRATES USED FOR ASTRONOMICAL X-RAY TELESCOPES. IN ORDER TO ACHIEVE HIGH-THROUGHPUT PROCESSING USING THESE TECHNIQUES WE PROPOSE TO DEVELOP A NOVEL APPROACH USING AN ELECTRONICALLY-ACTUATED APERTURE MECHANISM TO ACTIVELY CONTROL THE SHAPE OF A LONG RECTANGULAR MM-SCALE BEAM OF ADATOM OR IONS AS THE SUBSTRATE MOVES PAST AT CONSTANT VELOCITY THEREBY ENABLING EFFICIENT TWO-DIMENSIONAL FIGURE CORRECTION OF MULTIPLE SHELLS SIMULTANEOUSLY.