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X-ray Astronomy Lee Yacobi Selected Topics in Astrophysics July 9

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Outline Optics Refraction Optics Reflection Optics Grazing Incidence Spectral Grating Detection Proportional Detectors Micro Calorimeter

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Refractive Optics

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For Air: less than 1m

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Reflective Optics

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Reflective system is a possible solution Reflectivity follow Fresnel Equation ! Only very small incidence angles can contribute Only the upper edge of the paraboloid relevant

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Parabolic mirror is good for focusing Additional hyperbolic mirror create an image Wolter Type I Telescope: Primary parabolic reflector Secondary hyperbolic reflector (small angles) Several concentric (nested) mirrors increase collecting area Chandra setup

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Spectroscopy The ability of recognize the photon wavelength A spectrum worth a thousand pictures First spectra achieved by a proportional detector Gas chamber Output signal prop to photon energy Low energy resolution

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Diffraction Grating

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Detection Gas Chamber proportional detector Gas particle went through photo-ionization The ion is accelerated by the voltage between anode to cathode Collisions generate more ions which arrives to the cathode The detected current is proportional to the photon energy Scintillation proportional detector A solid state crystal is ionized by a photon The energy transfer into impurities in the crystal by electron-hole pairs The recombination emit light in the UV The amount of light is proportional to photon energy

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Detection

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Semi-Conductor MicroCalorimeter Array of silicon pixel at ~0.1K Single photon energy is transformed into heat through phonons Resistance changed fast with temperature (Thermistor)

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Detection SuperConducting MicroCalorimeter SuperConducting thin layer array (at ~1mK) Single photon energy is transformed into heat The phase transition into a conducting material is detected Temperature sensitivity is at microKelvin Energy resolution is up to 2.5 eV (@0.3-7KeV) 300X300micron pixel size (smaller has better spectral resolution)