DIFFERENTIAL PHASE ACOUSTIC MICROSCOPY FOR MICRO-NDE

WE PROPOSE TO UNDERTAKE A PROGRAM TO DEVELOP THE ACOUSTIC COUNTERPART OF THE NOMARSKI DIFFERENTIAL PHASE CONTRAST OPTICAL MICROSCOPE. SUCH A SYSTEM IS PARTICULARLY USEFUL FOR NDE IMAGING AND CHARACTERIZING MINUTE VARIATIONS IN THE ELASTIC PROPERTIES OF SPECIMENS WITH HIGH LATERAL RESOLUTION. STRESS PATTERNS IN SOLIDS, ION-IMPLANTED SEMICONDUCTORS, TITANIUM:TITANIUM DIFFUSION BONDS, GRAINS IN SOLIDS, AND COMPOSITES ARE EXAMPLE SAMPLES TO BE CHARACTERIZED WITH SUCH A MICROSCOPE. DURING THIS PROGRAM WE WOULD LIKE TO DEMONSTRATE A DIFFERENTIAL PHASE MICROSCOPE AT 50 MHZ (RESOLUTION OF 30 MU M). A DUAL-BEAM ACOUSTIC LENS PROVIDES TWO ADJACENT ACOUSTIC FOCI; THE PHASE DIFFERENCE BETWEEN THE SIGNALS RECEIVED FROM THESE TWO FOCI WILL RESULT IN THE IMAGE CONTRAST. DURING PHASE I WE WILL (I) IDENTIFY THE SAMPLES OF INTEREST TO NASA; (II) FABRICATE TWO DUAL-BEAM LENSES FOR SURFACE AND SUBSURFACE IMAGING; (III) DEVELOP THE ELECTRONICS FOR DRIVING THE DUAL-BEAM LENSES AND FOR PHASE SENSITIVE DETECTION; AND (IV)PERFORM SURFACE AND SUBSURFACE DIFFERENTIAL PHASE IMAGING AT 50 MHZ. DURING PHASE II WE EXPECT TO EXTEND THE FREQUENCY TO 300 MHZAND ANTICIPATE A LATERAL RESOLUTION OF 5 MU M. FOR PHASE III WE INTEND TO SEEK FUNDING FROM COMMERCIAL MANUFACTURERS OF ACOUSTIC MICROSCOPES FOR A 1 GHZ SYSTEM.