DYNODE MATERIAL STUDIES FOR A NOVEL TWO DIMENSIONAL ELECTRON MULTIPLIER

THE PHOTOMULTIPLIER TUBE (PMT). CONSISTING OF A PHOTOCATHODE AND A DYNODE BASED ELECTRON MULTIPLIER (EM), IS AN IMPORTANT ELECTRO-OPTIC DEVICE IN A VARIETY OF RADIATION MEASUREMENTS. IT IS A VERSATILE AND SENSITIVE DETECTOR WITH LOW NOISE AND FAST RESPONSE TIME. THE EM DYNODE STRUCTURES, HOWEVER, PRECLUDE FINE GRAIN, TWO-DIMENSIONAL (2-D) POSITION SENSITIVITY USING CONVENTIONAL DESIGNS. MESH DYNODES HAVE BEEN DEVELOPED TO ADDRESS THIS ISSUE BUT, DUE TO LATERAL SPREADING OF THE ELECTRON AVALANCHE BETWEEN STAGES, ARE STILL TYPICALLY LIMITED TO 1-2 MM IN POSITION RESOLUTION. THIS PROJECT PROPOSES A NOVEL EM DESIGN THAT SHOULD ACHIEVE RESOLUTIONS OF 100 UM OR LESS WHILE PRESERVING THE BENEFITS OF THE CLASSICAL DYNODE STRUCTURE. OTHER BENEFITS INCLUDE: COUNT RATES UP TO 10(7)/SEC PER (100UM)(2) PIXEL, IMPROVED TIMING RESOLUTION, ESSENTIAL GAIN INDEPENDENCE OF AXIAL MAGNETIC FIELD, AND THE POSSIBILITY OF ACTIVE AREAS UP TO 20 CM IN DIAMETER. PHASE I WILL FOCUS ON DYNODE MATERIAL IDENTIFICATION AND SELECTRION, WHICH IS THE KEY ELEMENT IN THE NEW GEOMETRY. SUCCESS IN THIS PROJECT WILL PROVIDE THE NECESSARY BASIS FOR DEVELOPING A 2-D ELECTRON MULTIPLYING STRUCTURE THAT WOULD HAVE A WIDE RANGE OF INSTRUMENTATION APPLICATIONS.