A SILICON DRIFT PHOTODIODE FOR SCINTILLATION SPECTROSCOPY

SCINTILLATION DETECTORS HAVE REMAINED THE LEADING TYPE OF DETECTOR IN MANY AREAS OF NUCLEAR PHYSICS. ALTHOUGH IMPROVEMENTS IN SCINTILLATOR CYYSTAL TECHNOLOGY HAVE EXTENDED THE UTILITY OF SCINTILLATOR-BASED SYSTEMS, SERIOUS DEFICIENCIES IN THE OPTICAL DETECTORS USED WITH THE SCINTILLATOR CRYSTALS ARE LIMITING THE FULL POTENTIAL OF THIS DETECTOR TECHNOLOGY. CONVENTIONAL SCINTILLATION SYSTEMS USE PHOTOMULTIPLIER TUBES OR SILICON P-TYPE-INTRINSIC-N-TYPE PHOTODIODES AS OPTICAL DETECTORS. UNFORTUNATELY, BOTH OPTICAL DETECTOR SYSTEMS HAVE SERIOUS DEFICIENCIES IN TERMS OF QUANTUM EFFICIENCY AND SIGNAL-TO-NOISE RATIO. RECENTLY, IT HAS BEEN DEMONSTRATED THAT SILICON DRIFT PHOTODIODES CAN BE MADE WITH VERY LOW NOISE, AND IT HAS BEEN SUGGESTED THAT THESE DEVICES MAY BE QUITE USEFUL AS SCINTILLATION PHOTODETECTORS. THE PHASE I WORK IS PRODUCING SILICON DRIFT PHOTODIODES THAT ARE DERIVATIVES OF DEVICES PRESENTLY BEING DEVELOPED FOR APPLICATIONS IN OTHER DISCIPLINES (E.G., HIGH ENERGY PHYSICS); THEIR QUANTUM EFFICIENCY IS BEING OPTIMIZED AT BLUE-GREEN (400 TO 550 NM) WAVELENGTHS BY PERFORMING AN "OPTIMIZED" SERIES OF P+ DIFFUSIONS TO THE FRONT (LIGHT-SENSITIVE) SURFACE OF THE DEVICE.