A FAST DIRECT ENCODING POSITION-SENSITIVE DETECTOR

POSITION-SENSITIVE DETECTORS (PSDS) ARE WIDELY USED FOR CHARGED PARTICLE AND PHOTON SPECTROSCOPY AS WELL AS IN IMAGING APPLICATIONS. THE DETECTORS PRESENTLY AVAILABLE HAVE ADEQUATE LATERAL RESOLUTION, BUT CONSTRAIN RESEARCHERS TO RELATIVELY LOW PARTICLE COUNT RATES COMPARED TO SINGLE CHANNEL PULSE COUNTING DETECTORS. THE OBJECTIVE OF PHASE I IS TO EVALUATE THE FEASIBILITY OF A DIRECT ENCODING PSD WITH256X256 PIXEL LATERAL RESOLUTION AND LESS THAN 10 NSEC PULSEPAIR RESOLUTION. THE BASIC APPROACH IS TO FOLLOW THE CUSTOMARY DUAL MICROCHANNEL PLATE (MCP) WITH A STACK OF MCPS, EACH SURFACE OF WHICH IS PATTERNED WITH TWO INTERDIGITATED ELECTRODES. THE ELECTRODE PAIRS HAVE SUCCESSIVELY FINER PATTERNS, AND EACH IS CONNECTED TO A COMPARATOR CIRCUIT. AS A CHARGE BURST TRAVERSES THE STACK, IT ENCOUNTERS AT EACH SURFACE ONE ELECTRODE OF THE PAIR, DETERMINING ONE DIGIT OF A GRAY BINARY CODE. EACH MCP RESTORES LOST CHARGE, AND THE BURST FINALLY STRIKES A COLLECTION PLATE, PROVIDING A STROBE PULSE TO READ OUT THE COMPARATORS. FOR 2(N) PIXELS, ONLY N COMPARATORS AND N/2 MCPS ARE REQUIRED. THE PULSE PAIR RESOLUTION IS EXPECTED TOBE SET LARGELY BY THE SPEED OF THE COMPARATORS. FEASIBILITYWILL BE DEMONSTRATED BY CONSTRUCTING AND TESTING AN 8X8 PIXEL, 50 NSEC (DIGITAL LOGIC) PSD.