The Development of Anodic Aluminum Oxide Based Micro-channel Plate for Large-area Photo-detector
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The Development of Anodic Aluminum Oxide Based Micro-channel Plate for Large-area Photo-detector Seon Woo Lee1, Qing Peng2, Anil U. Mane2, Jeffrey W. Elam2, Karen Byrum1, Henry Frisch1,3 and Hau Wang4 1 High Energy Physics Division, Argonne National Laboratory, Argonne, IL, 60439, U.S.A. 2 Energy Systems Division, Argonne National Laboratory, Argonne, IL, 60439, U.S.A. 3 High Energy Physics, Enrico Fermi Institute, University of Chicago, Chicago, IL, 60637, U.S.A. 4 Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, U.S.A. ABSTRACT Anodized Aluminum Oxide (AAO) based micro-channel plates (MCP) are fabricated in order to develop economical large-area photodetectors. Commercially available glass capillary array has a limitation to reach channel diameter below ~10 microns. However, smaller channel diameter is desired for better spatial and fast timing resolution. AAO based MCP is a good candidate to produce channel diameter less than 10 um by taking advantage of the nano-scale intrinsic pores during etching process. In this study, various channel diameters are fabricated with use of lithographic patterning techniques and wet etching; and characterized with optical, atomic force, and scanning electron microscopies. The channel diameter, channel length and related aspect ratio, as well as the open area are varied in order to maximize the MCP photon amplification. INTRODUCTION Photo-detector based on photomultiplier tube (PMT) is indeed a remarkable device with extreme sensitivity, high gain and high quantum efficiency [1]. However, conventional PMT has multiple discrete dynodes for secondary electron amplification. Assembly of discrete parts is expensive and not easy to build up for a large-scale device. Microchannel plate (MCP) is a plane device composed of delicately fabricated micron-size channel array. When the channel inner walls are coated with material that enhances the secondary electron emission, each channel behaves as an individual PMT and the MCP serves as a relatively large area photomultiplier device [2-5]. Conceptually, an array of MCPs will constitute a truly large area detector desired for high energy physics and astrophysics application. The main show stopper is the cost of MCP. Therefore, there is a need to develop large area and economical MCPs. Figure 1(a) shows a schematic drawing of a MCP based PMT. Short channel length of MCP gives markedly fast timing resolution and micron-scale pore diameters result in high spatial resolution [6]. Commercially available MCP amplification stage is made of glass capillary that is fabricated by drawing glass fibers, slicing and etching hollow fiber cores chemically. However, glass capillary MCP has technical limitation to make smaller channel diameters. The possible range of optical fiber diameter is from 2 to 40 microns [7]. As the fiber diameter decreases, the fabrication becomes more difficult and the cost becomes more expensive. In addition to its high cost, the mechanical strength is also a concern for large-scale device application.
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