CONDUCT SIMULTANEOUS ULTRASONIC INTERFEROMETRY AND SYNCHROTRON X-RADIATION MEASUREMENTS ON TRANSITION METALS AND LANTHANIDES TO ASSESS THEIR THERMODYNAMIC AND MECHANICAL PROPERTIES AT HIGH PRESSURE AND HIGH TEMPERATURE. THESE MEASUREMENTS ALLOW US TO DERIVE EQUATIONS OF STATE, PHASE TRANSITIONS, YIELD STRENGTH, ELASTIC BULK AND SHEAR MODULI AND THEIR PRESSURE AND TEMPERATURE DERIVATIVES, WHICH NOT ONLY PROVIDE A MORE COMPLETE COVERAGE OF THERMODYNAMIC PROPERTIES THAN INDIVIDUAL METHODS CURRENTLY IN USE, BUT ALSO YIELD A HIGH DEGREE OF SELF-CONSISTENCY AND ACCURACY IN THE DERIVED THERMODYNAMIC PARAMETERS. A NEWLY DEVELOPED METHOD WILL BE USED TO DETERMINE MACROSCOPIC STRESS AND YIELD STRENGTH, WHICH WILL PROVIDE CRUCIAL HIGH PRESSURE STRENGTH DATA TO COMPLEMENT HIGH STRAIN RATE RESULTS FROM SHOCK WAVE STUDIES. IN ADDITION, MEASUREMENTS ON SINGLE CRYSTALS ALLOW FOR THE DETERMINATION OF ELASTIC ANISOTROPY AND EXPLORATION OF NONLINEAR ELASTICITY. THE TECHNIQUES DEVELOPED IN THIS PROJECT WILL PROVIDE TRANSFERABLE KNOWLEDGE FOR SSP RESEARCH ON HIGH-Z ACTINIDES WHEN COMBINED WITH HIGH PENETRATION AND HIGH Q RANGE NEUTRON SOURCE IN THE FUTURE.