In the γ-ray Cherenkov Astronomy framework mirror coating plays a crucial role in defining the light response of the telescope. We carried out a study for new mirror coating solutions with both a numerical simulation software and a vacuum chamber for small sample production. In this article, we present a new mirror coating solution consisting of a 28-layer interferometric SiO 2 -TiO 2 -HfO 2 design deposited on a glass substrate, whose average reflectance is above 90% for normally incident light in the wavelength range between 300 and 550 nm.

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After the shutdown of the Hubble Space Telescope in a few years, new astronomical missions for the ultraviolet (UV) wavelength range between 91 and 300 nm with improved optics and detectors will be necessary. This fact drives our development of solar blind photon counting microchannel plate (MCP) UV detectors with high quantum efficiency, high spatial resolution, and low power readout electronics. We plan to use a cross-strip anode (XSA), which has a high spatial resolution and additionally allows a low gain operation of the MCPs which leads to an increased lifetime of the MCPs compared to detectors with other anode types. The main difficulty in implementing an XSA in a detector for space applications is the need for a (pre-) amplifier, a shaper, and an ADC for each of the strips, which means large power consumption and spatial requirements. The solution we are studying is the application of the so-called Beetle chip. This allows for an implementation of a readout electronics for an XSA with a power consumption of less then 10 W. For the tests of our readout electronics prototype, and for the burn-in of the MCPs, we recently finished a setup in a vacuum chamber that is similar to the configuration in the final detector. We present a brief overview of our detector design and details of the readout electronics setup as well as details of the setup in our vacuum chamber.

Observations of ultraviolet light is the key to understand high temperature processes in the universe like hot plasma, accretion processes or illuminated protoplanetary discs around UV sources. Furthermore these observation contribute to major cosmological questions, like the distribution of baryonic matter or the formation of the milky way, as pointed out by Gomez de Castro et al. 1 Driven by the idea to participate in the Russian World Space Observatory we started to develop a position sensitive micro channel plate detector (MCP) for spectroscopy in the range of 160 nm to 300 nm. Although we are not part of this project we still build a MCP detector prototype. In this paper we will present the general design of the detector and mainly focus on the aspect of our photocathode, while the electronics will be explained in more detail in the paper "Characterisation of low power readout electronics for a UV microchannel plate detector with cross-strip readout" (Paper number 9144-116) by Marc Pfeifer.Keywords: micro channel plate detector, caesium telluride photocathodes THE MCP DETECTORS DESIGNThe Institute of Astronomy and Astrophysics Tübingen has a long tradition in developing ultraviolet sensitive detectors and based on the heritage of the 1990's flight of ORFEUS we develop a position sensitive, solarblind, photon counting micro channel plate detector. Even if there is an ongoing progress in the development of CCD detectors for all wavelengths, they are victims of their high performance in the optical band, which generates a high noise compared to the desired UV band. By using solar-blind photocathodes our MCP detector avoids this problem and doesn't need extensive shielding or additional filters for a low signal-to-noise-ratio which, in combination with their fast readout, makes such a detector still leading in ultraviolet spectroscopy. Working principleDepending on the field of use, there are two concepts for MCP detectors, either a sealed detector with a semitransparent photocathode coated on an entrance window or an open-faced detector with an opaque photocathode directly on the micro channel plates. As the MCPs work with high voltage in the range of several thousand volts, they need to be operated under vacuum conditions with a pressure below 1 × 10 −5 mbar to avoid damage by accelerated particles. Therefore open-faced detectors only work in space, while sealed detectors can be operated everywhere, also in non-astronomical fields. Furthermore the photocathodes degrade under oxygen exposure, 2 so they need to be stored under vacuum conditions (or inert gas), which complicates the use of open-faced detectors, as they need a sealed envelope until the detector is in space. As shown in fig. 1 and fig. 2 any incoming photon that hits the photocathode, releases an electron which is accelerated towards the micro channel plates, where it creates an avalanche of additional electrons. Depending on the MCP configuration and applied voltage a gain factor of 1 × 10 5 to 1 × 10 7 is achieved. This electron cloud hits a cha...