ULTRAFAST DIAMOND FILM PHOTOCONDUCTIVE DETECTOR

OVER THE PAST DECADE STUDIES HAVE INDICATED THAT IT IS POSSIBLE TO UTILIZE THE ULTRAFAST (PICOSECOND) RESPONSE TIMEOF A PHOTOCONDUCTOR TO DETECT AND TIME RESOLVE THE RAPID VARIATIONS OF LIGHT FROM A RAPIDLY CHANGING SOURCE SUCH AS APULSED LASER, A LASER FUSION EXPERIMENT, A DIRECTED ENERGY WEAPON OR A NUCLEAR WEAPONS EXPLOSION. IN ADDITION TO THE RAPID TEMPORAL EVOLUTION OF THE LIGHT OUTPUT FROM SUCH SOURCES, THE INTENSITY USUALLY VARIES OVER AN EXTREMELY WIDERANGE REQUIRING A DETECTOR THAT NOT ONLY HAS A ULTRASHORT RESPONSE TIME, BUT ALSO HAS A HIGH, YET CONSTANT, SENSITIVITY. THE PHOTO-CONDUCTIVE RADIATION DETECTOR IS SIMPLE IN CONCEPT AND DESIGN COMPARED TO CONVENTIONAL RADIATION DETECTORS. THE MOST HEAVILY STUDIED PHOTOCONDUCTORS FOR RADIATION DETECTION APPLICATIONS HAVE BEEN SEMI-INSULATING SILICON, GALLIUM-ARSENIDE, AND INDIUM-PHOSPHIDE. THE MAIN LIMITATIONS OF THESE MATERIALS ARE THEIR LOW RADIATION RESISTANCE, LOW LEVELS OF MAXIMUM DCBIAS AND THERMAL RUNAWAY EFFECTS AT INCIDENT LIGHT INTENSITIES, DUE TO THEIR RELATIVELY LOW THERMAL CONDUCTIVITIES AND SMALL BANDGAPS. IN ORDER TO CIRCUMVENT THESE PROBLEMS, IT IS NECESSARY TO CONSIDER SEMICONDUCTING MATERIALS WITH WIDER BANDGAPS AND LARGE DIELECTRIC STRENGTHSTHAT CAN SUPPORT HIGHER VOLTAGES. ONE OF THE MOST INTERESTING CANDIDATE PHOTOCONDUCTING MATERIALS IS DIAMOND BECAUSE OF ITS OVERWHELMINGLY SUPERIOR PHYSICAL PROPERTIES. IN THIS PROGRAM, THE PHOTOCONDUCTIVE RESPONSE OF DIAMOND FILMS GROWN BY PLASMA ASSISTED CHEMICAL VAPOR DEPOSITION IS BEING INVESTIGATED, AND EDITOR POTENTIAL FOR ULTRAFAST PHOTOCONDUCTIVITY RADIATION DETECTION APPLICATIONS IS BEING ASSESSED. WHEN SUCCESSFULLY DEVELOPED, ULTRAFAST RADIATION REDUCTION TECHNOLOGY WOULD HAVE APPLICATION IN NUCLEAR WEAPONS TESTING, AS WELL AS LASER DRIVEN FUSION SYSTEMS AND SPACEBORNE SURVEILLANCE SYSTEMS. THIS TECHNOLOGY COULD LEAD TO DEVELOPMENTS HIGH SPEED SWITCHING FOR PULSED LASER POWER SUPPLIES, AND PULSED MICROWAVE GENERATORS.