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Space Research Centre Silicon Carbide X-Ray detectors for Planetary Exploration Dr. John E. Lees University of Leicester 8 th International Conference on Position Sensitive Detectors September 2008
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Space Research Centre Introduction Limitations of silicon based detectors for planetary exploration cooling radiation damage Search for other materials – wide band gap GaAs Diamond Silicon Carbide SiC imaging arrays Collaboration with University of Newcastle
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Space Research Centre Ideal requirements for X-ray detectors Photon counting Imaging Good timing resolution High spatial resolution Solar blind – not sensitive to visible light High quantum efficiency High dynamic range Low background Radiation hard Energy resolution XX SiC
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Space Research Centre Semi-Transparent SiC Schottky Diode LHS: A 280 m 2 Schottky contact and gold bond pad RHS: Die layout with a range of diode sizes 1.0x10 -3 cm -2 1.81x10 -3 cm -2 4.93x10 -4 cm -2 400 m
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Space Research Centre STSSD structure 20 m epitaxial layer on a 370 m substrate Semi-transparent Schottky contact. 3 nm Ti / 12 nm Ni 25 nm thermally grown SiO 2 4nm Cr / 200nm Au 5 nm Cr / 250nm Au4nmCr/100nmNi Ohmic Contact n 4H-SiC n + 4H-SiC Lees et al., Nucl. Inst. Meth A 578 (2007) 266-234
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Space Research Centre Improving the Low Energy Response K-shell emission lines of elements: Na (Z=11, E=1.04 keV) to Zn (Z=30, E=8.64 keV) STSSD has an 18nm thick electrode
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Space Research Centre Planetary Exploration GeneralMulti-spectral: X-rays/UV/Optical/Infra-red Imaging pixel arrays EnvironmentRadiation environment Shielding Radiation hard electronics Operating temperatures SpacecraftMass Power Cost
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Space Research Centre Some current and planned planetary missions MercuryMessenger and BepiColombo VenusVenus Express and Venus Climate Orbiter MarsMars Reconnaissance Orbiter, Mars Express, ExoMars SaturnCassini-Huygens and Tandem JupiterJUNO and Laplace
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Space Research Centre Jupiter X-rays (Chandra) FUV (HST)
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Space Research Centre Auroral Processes Precipitation of energetic ions and electrons along field lines from the planetary magnetosphere into the atmosphere produces emissions in IR, visible, UV, and X-ray wavelengths Table shows typical values for the magnetised planets PlanetEarthJupiterSaturnUranusNeptune Electron input power (GW) 10 1000 100 10 1 UV output (GW) 1 100 10 1 0.1 X-ray brem output (MW) 1 100 10 1 0.1
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Space Research Centre Radiation environment Alessandro Atzei and Peter Falkner, ESA technical note, SCI-AP/2004/TN-085/AA
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Space Research Centre Radiation environment Comparison between ONERA-full (D&G + GIRE + Salammbô) and ESA ref. D&G at an equatorial distance of 3 Rj from Jupiter centre
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Space Research Centre Irradiation of STSSDs Phase 1 - irradiation at Paul Scherrer Institut 63 MeV protons Total fluence 1x10 11 cm -2 Phase 2 - irradiation at Theodor Svedberg Laboratory 50 MeV. Total fluence ~1 x 10 13 protons cm-2.
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Space Research Centre STSSD Radiation Tolerance I-V measurements
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Space Research Centre STSSD Radiation Tolerance 55 Fe X-ray spectra
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Space Research Centre STSSD Radiation Tolerance 109 Cd X-ray spectra
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Space Research Centre Next Steps Material characterisation Improve electronics better energy resolution Extend radiation fluences Protons, neutrons, electrons and X-ray/gamma-ray Modelling New device structures
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Space Research Centre Acknowledgements Nigel BannisterUniversity of Leicester David Bassford Emma Bunce Stan Cowley George Fraser Mark Sims Dean Talboys Chris Whitford Alton HorsfallUniversity of Newcastle
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