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X-Ray detection techniques and the BepiColombo-MIXS instrument

X-Ray detection techniques and the BepiColombo-MIXS instrument. David Rothery, Dept of Earth & Environmental Sciences D.A.Rothery@open.ac.uk. Direction of MPO motion. Solar Coronal Primary X-ray Flux. X-ray fluorescent and backscattered flux.

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X-Ray detection techniques and the BepiColombo-MIXS instrument

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  1. X-Ray detection techniques and the BepiColombo-MIXS instrument David Rothery, Dept of Earth & Environmental Sciences D.A.Rothery@open.ac.uk

  2. Direction of MPO motion Solar Coronal Primary X-ray Flux X-ray fluorescent and backscattered flux Planetary X-ray Remote Sensing : BepiColombo MIXS (2013)

  3. Fluorescent X-rays reveal: Elemental composition to a depth of a few mm for low atomic number elements (eg Mg) and for L-shell emission lines of heavier elements For heavier elements, K-shell emission (higher energy) increases the sampling depth to tens of mm • X-ray spectroscopy is complementary to: • gamma-ray and neutron spectroscopy (MGNS) low spatial resolutionmeasurements of a few elements to depths of 10 cm • Optical and IR spectroscopy (Simbio-Sys, MERTIS) sensitive to • mineralogy (cation-oxygen bonds) to depths of tens of mm

  4. MIXS – Mercury Imaging X-ray Spectrometer PI George Fraser, University of Leicester Two devices: MIXS-C (Collimator) MIXS-T (Telescope)

  5. MIXS-C 10.4 degree FOV, optimised to provide the largest X-ray throughput at all energies for all solar states. Pixel size 70 km at periherm, 270 km at apoherm. MIXS-T 1.1 degree FOV, angular resolution <9 arcmin. Spatial resolution < 1 km at periherm, 4 km at apoherm But achievable only during solar flares. FOVs/pixels will be binned when signal is low. Effective spatial resolution will vary according to solar activity and will differ between elements.

  6. Microchannel plate (MCP) optics, differently configured for MIXS-C and MIXS-T

  7. MIXS-C

  8. MIXS-T (Wolter type I optic)

  9. Identical focal plane assemblies for MIXS-C and MIXS-T. 64 x 64 array of Macropixel DEPFET detectors, measuring X-rays 0.5-7.5 keV

  10. Energy resolution (will degrade because of radiation damage):100 eV at 1 keV at start of orbital tour <200 eV after one year at Mercury MIXS-C at apoherm, 209s dwell-time

  11. Best feasible MIXS-T resolutionSimulated mapping of Fe abundance Assume brightness is proportional to albedo Assume albedo at 750 nm is proportional to FeO concentration Assume FeO content is proportional to Fe concentration Assume Si concentration is ~homogenous Assume brightness is proportional to albedo Assume albedo at 750 nm is proportional to FeO concentration Assume FeO content is proportional to Fe concentration Assume Si concentration is ~homogenous 100 km

  12. Calibration issues It is vital to know the intensity of the solar X-ray illumination, hence close collaboration with SIXS (Solar Intensity X-ray Spectrometer) Roughness, grain size, packing density, incidence angle, emission angle? Experimental results under review (Näränen et al.)

  13. X-rays and Mercury’s magnetosphere – D. Talboys and E. Bunce • X-rays may be generated in Mercury’s magnetosphere and by electron and ion precipitation onto the surface • Currently there is little understanding of these processes at Mercury • Emission processes may provide insight into • magnetospheric phenomena • Magnetosphere-exosphere-surface system • Surface composition (particluarly at the poles and on the night side of the planet) • Theoretical investigations based on experience with X-ray emission processes and the magnetospheres of Earth other planets are beginning at Leicester

  14. Dynamic processes in Mercury’s magnetosphere such as: Dayside magnetic reconnection phenomena (or Flux Transfer Events, FTEs) ULF wave activity Extremely rapid substorm activity (few tens of seconds). (MIXS-T spatial resolution could be useful here) Any of these could produce X-rays at the surface (or even in the exosphere) by means of precipitation and/or acceleration of electrons and/or ions in large scale current systems associated with solar wind-magnetosphere-exosphere-surface coupling Lots of scope for collaboration with HEWG members

  15. Optics (focus tests) MIXS T res could be needed for substorm, structure Add telescope tubes after slide 4 Cfrp carbon fibre reinforced polymer

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