HIGH ENERGY DENSITY SCIENCE (HEDS), THE STUDY OF MATTER AT EXTREME TEMPERATURES AND PRESSURES FOUND INSIDE STARS AND PLANETS, IS CENTRAL TO THE SCIENCE-BASED APPROACH TO STOCKPILE STEWARDSHIP. POWERFUL LASERS ARE A KEY TOOL FOR BOTH GENERATING AND PROBING MATTER AT ULTRA-HIGH ENERGY DENSITIES WITH EXQUISITE PRECISION, ALLOWING THE EXTREME CONDITIONS ENCOUNTERED IN NUCLEAR WEAPONS TO BE REPLICATED AND DIAGNOSED IN THE LABORATORY. ADVANCED XRAY SOURCES ARE AN ENDURING NEED OF THE STOCKPILE STEWARDSHIP PROGRAM (SSP), BOTH FOR LABORATORY HEDS EXPERIMENTS AND FOR SURVEILLANCE IMAGING OF WEAPON SUBSYSTEMS. LASER-DRIVEN X-RAYS UNIQUELY ENABLE TAILORABLE, HIGH-RESOLUTION AND MULTI-LINE-OF-SIGHT TOMOGRAPHY OF DENSE, HIGHLYENERGIZED MATTER. NEW LASER TECHNOLOGY HAS RECENTLY LED TO THE DEVELOPMENT OF TABLETOP LASERDRIVEN PLASMA-BASED ELECTRON ACCELERATORS THAT ARE DRAMATICALLY SMALLER AND CHEAPER THAN THEIR CONVENTIONAL RADIO-FREQUENCY COUNTERPARTS. THESE COMPACT ACCELERATORS UNDERLIE A VERSATILE ARRAY OF NEW X-RAY SOURCES WITH PULSE DURATIONS MEASURED IN FEMTOSECONDS AND SOURCES SIZES MEASURED IN MICROMETERS. THESE NOVEL X-RAY SOURCES OFFER AS-YET-UNEXPLORED POTENTIAL FOR NONDESTRUCTIVELY PROBING HIGH-ENERGY-DENSITY MATTER WITH UNPRECEDENTED RESOLUTION, AND THUS FOR PRECISE MONITORING OF THE STOCKPILE.