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Keywords:Large-area picosecond photodetectors (LAPPD) Time of flight detector Glass capillary array (GCA) Microchannel plate (MCP) Atomic layer deposition (ALD) a b s t r a c tWe present a progress update on plans to establish pilot production and commercialization of Large Area (400 cm 2 ) Picosecond Photodetector (LAPPD ™ ). Steps being taken to commercialize this MCP and LAPPD ™ technology and begin tile pilot production are presented including (1) the manufacture of 203 mm  203 mm borosilicate glass capillary arrays (GCAs), (2) optimization of MCP performance and creation of an ALD coating facility to manufacture MCPs and (3) design, construction and commissioning of UHV tile integration and sealing facility to produce LAPPDs. Taken together these plans provide a "pathway toward commercialization".& 2014 Elsevier B.V. All rights reserved. LAPPDThe Large Area Picosecond Photodetector (LAPPD ™ ) is a microchannel plate (MCP) based photodetector, capable of imaging, and having both high spatial and temporal resolution in a vacuum package with an active area of 400 cm 2 . LAPPD ™ are characterized by a uniquely simple design based upon an all-glass vacuum package comprised of top and bottom plates and square sidewall, each made of borosilicate float glass, depicted in Fig. 1.Key design features of the LAPPD include: (a) an internal chevron pair stack of "next generation" MCPs produced by applying resistive and emissive coatings to borosilicate glass capillary array (GCA) substrates; (b) a modular all-glass detector package with conductive RF microstrips passing through a glass frit seal that hermetically bonds the side walls to the bottom anode plate while allowing electrical contact to the interior of the device; eliminating the need for metal electrical pins penetrating the evacuated detector package; (c) resistively coated spacers that function as high voltage (HV) dividers to distribute voltage across the MCP chevron stack, eliminating the need for separate electrical leads contacting the tops and bottoms of both MCPs; and (d) RF stripline anodes applied to the bottom plate with an analog bandwidth above 1.5 GHz for good spatial and temporal resolution [1]. MCP based photodetectorsMCP's consists of millions of conductive glass capillaries (4-25 mm in diameter) fused together and sliced into a thin plate [2]. Each capillary or channel works as an independent secondary-electron multiplier. Single electrons that hit a pore on one side of the plate convert into large bunches of electrons that cascade from the other side [3], with typical amplification from a pair of plates of 10 7 . Fig. 2 (left) shows a large area glass capillary array (GCA) consisting of millions of 20 mm diameter pores with an overall size of 203 mm  203 mm  1.2 mm with an aspect ratio¼60:1, bias angle of 81, and open area ratio of 60%. Atomic Layer Deposition (ALD) techniques are used to apply resistive and emissive coatings, converting the GCA into a high performance MCP. A high voltage is applied across the top and bottom surfaces of the...

The technique of atomic layer deposition (ALD) has enabled the development of alternative glass microchannel plates (MCPs) with independently tunable resistive and emissive layers, resulting in excellent thickness uniformity across the large area (20 × 20 cm), high aspect ratio (60:1 L/d) glass substrates. Furthermore, the use of ALD to deposit functional layers allows the optimal substrate material to be selected, such as borosilicate glass, which has many benefits compared to the lead-oxide glass used in conventional MCPs, including increased stability and lifetime, low background noise, mechanical robustness, and larger area (at present up to 400 cm2). Resistively stable, high gain MCPs are demonstrated due to the deposition of uniform ALD resistive and emissive layers on alternative glass microcapillary substrates. The MCP performance characteristics reported include increased stability and lifetime, low background noise (0.04 events cm−2 s−1), and low gain variation (±5%).

A new method of fabricating microchannel plates has been investigated, employing microcapillary arrays of borosilicate glass that are deposited with resistive and secondary emissive layers using atomic layer deposition. Microchannel plates of this kind have been made in sizes from 33 mm to 200 mm, with pore sizes of 40 µm and 20 µm, pore length to diameter ratios of 60:1, bias angles of 8°, and open areas from 60% to 83%. Tests with single MCPs and MCP pairs have been done and show good imaging quality, gain comparable to conventional MCPs, low background rates (~ 0.085 events sec -1 cm -2 ), fast pulse response, and good ageing characteristics. The quantum efficiency for bare and alkali halide coated MCPs is similar to conventional MCPs, and we have also been able to deposit opaque GaN(Mg) cathodes directly onto these MCPs.

Manufacturing plans for "next generation" microchannel plates (MCPs) and the technical advantages enabled by this evolving technology are presented. The Large Area Picosecond Photodetector (LAPPD) is an MCP based photodetector, capable of imaging, with high spatial and temporal resolution in a hermetic package with an active area of 400 square centimeters. A key component of LAPPD is a chevron pair of large area (20 x 20 cm) MCPs. The manufacture of these large-area high performance MCPs has been enabled by the convergence of two technological breakthroughs. The first is the ability to produce large blocks of hollow, micronsized glass capillary arrays (GCAs) developed by Incom Inc. The Incom process is based on the use of an etchless "hollow-core" approach in the glass drawing process, eliminating the need to remove core material by chemical etching. The arrays are fabricated as large blocks that can be sliced to form large area wafers, without regard to the conventional limits of L/d (capillary length / pore diameter). Moreover, the glass used in these GCAs is physically more robust, does not have a tendency to warp, and has low levels of radioactive isotopes resulting in low dark noise. The second breakthrough is the advent of atomic layer deposition (ALD) coating methods and materials to functionalize GCAs to impart the necessary resistive and secondary emission properties suitable for large area detector applications. Recent results demonstrating the high performance, uniformity, and long term stability of the current MCP product are presented.