High Speed Optical Imaging Photon Counting Microchannel Plate Detectors for Astronomical and Space Sensing Applications Oswald Siegmund, John Vallerga, Barry Welsh, Jason McPhate, Anton Tremsin, Space Sciences Laboratory, U.C. Berkeley ABSTRACT Cross delay line and cross strip high resolution position encoding readouts have the capability of being able to independently record the accurate time of each detected photon event without compromising the imaging performance. This is important for time dependent UV-Visible applications in ground based and space astronomy, biology, night- time reconnaissance and time of flight instruments. We have developed sealed tube microchannel plate cross strip (18 mm) and cross delay line (25 mm) anode detectors with visible light photocathodes. These have high spatial resolution, are capable of high counting rates and provide extended lifetimes. High-speed electronics for the cross strip readout have been developed and accommodate > 5 MHz random photon rates, and we have demonstrated time tagging of events with ~1ns accuracy. Spatial resolutions of < 30 μm with excellent image linearity have been achieved in tests of an 18 mm cross strip anode sealed tube detector. The 25 mm cross delay line sealed tube has been commissioned on the South African Large Telescope 10m telescope and performed a variety of high time resolution observations of transient and time-variable astronomical sources. Keywords: Microchannel plate, photon counting, imaging, timing 1. INTRODUCTION In recent years we have implemented a variety of high-resolution, photon-counting Microchannel plate (MCP) detectors in space instrumentation for satellite (FUSE [1], GALEX [2], IMAGE [3], SOHO [4], HST-COS [5]), rocket, and shuttle payloads as well as sensors for ground based astronomy, reconnaissance and biology. These detectors satisfy the imaging and timing demands of applications including astronomy of transient and time-variable sources [6], Earth atmospheric imaging and spectroscopy for real time space weather monitoring, biological single-molecule fluorescence lifetime imaging microscopy [7], airborne and space situational awareness, and optical night-time reconnaissance [8]. Our recent work on high performance photon counting imaging readouts has enabled significant advancements over previous detector systems used for these applications. We have developed Cross-Strip (XS) and Cross-Delay-Line (XDL) event position encoding anodes, and have integrated them into detector systems with readout electronics. Sealed tube MCP detectors with formats of 18mm (XS) (Fig. 1) and 25mm (XDL) (Fig. 2), with visible light sensitive photocathodes have been built and are currently being used for biological fluorescence lifetime imaging microscopy [9], and ground based high time resolution astronomy [6] respectively. Using the XS sealed tube detector and a new generation of event encoding electronics we can achieve high spatial resolution (< 30 μm FWHM) with self triggered ~1 ns event timing accuracy at up to ~10 MHz event rates. Our installation and astronomical commissioning of one of these detectors at the South African Astronomical Observatory (SAAO), South African Large Telescope (SALT) 10m telescope has enabled us to observe a number of transient and time-variable sources. Our photometer is positioned in an auxiliary instrument port of the SALT. This is a stand-alone instrument that includes our detector system with two filter wheels (neutral density and U, B, V), an iris, and all the control modules necessary to operate the system. This instrument gives us access to the southern sky with significant sensitivity and unprecedented time resolution (microsecond). High time resolution astronomy is still in its infancy, such that high cadence observations of the variable visible wavelength emission from cataclysmic variables, short period pulsars, M-dwarf flares, low mass X-ray binaries, flickering from black-holes in AGN, stellar occultations of solar system planets and high precision timing of transiting extra-solar planets are all topics of potential interest to the astronomical community. During two weeks of initial observations a large range of these objects were observed, including high time resolution observations of cataclysmic variables, pulsars, and flare stars. 2. SEALED TUBE DETECTOR SYSTEMS 2.1 Cross Delay Line Anode Detectors The cross delay line (XDL) anode is a relatively coarse (~1 mm period) multi-layer metal and ceramic pattern on an alumina substrate (Fig. 3). On one surface of the substrate a conductor is fabricated as a serpentine approximately 0.5 mm wide. Then sets of insulating and conducting fingers are applied in the orthogonal direction such that 50 % of the