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Directly deposited optical-blocking filters for single-photon x-ray imaging spectroscopy

Published in:
J. Astron. Telesc. Instrum. Syst., Vol. 3, No. 3 (2017), 036001.

Summary

Directly deposited optical-blocking filters (DD OBFs) have the potential to improve filter performance and lower risk and cost for future x-ray imaging spectroscopy missions. However, they have not been fully characterized on high-performance charge coupled devices (CCDs). This paper reports the results of DD OBFs processed on high-performance photon-counting CCDs. It is found that CCD performance is not degraded by deposition of such filters. X-ray and optical transmission through the OBF is characterized and found to match theoretical expectation. Light-leaks through pinholes and the side and back surfaces are found to lower the optical extinction ratio; various coating processes are developed to resolve these issues.
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Summary

Directly deposited optical-blocking filters (DD OBFs) have the potential to improve filter performance and lower risk and cost for future x-ray imaging spectroscopy missions. However, they have not been fully characterized on high-performance charge coupled devices (CCDs). This paper reports the results of DD OBFs processed on high-performance photon-counting CCDs...

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Development of CCDs for REXIS on OSIRIS-REx

Summary

The Regolith x-ray Imaging Spectrometer (REXIS) is a coded-aperture soft x-ray imaging instrument on the OSIRIS-REx spacecraft to be launched in 2016. The spacecraft will fly to and orbit the near-Earth asteroid Bennu, while REXIS maps the elemental distribution on the asteroid using x-ray fluorescence. The detector consists of a 2x2 array of back-illuminated 1kX1k frame transfer CCDs with a flight heritage to Suzaku and Chandra. The back surface has a thing p+-doped layer deposited by molecular-beam epitaxy (MBE) for maximum quantum efficiency and energy resolution at low x-ray energies. The CCDs also feature an integrated optical-blocking filter (OBF) to suppress visible and near-infrared light. The OBF is an aluminum film deposited directly on the CCD back surface and is mechanically more robust and less absorptive of x-rays than the conventional free-standing aluminum-coated polymer films. The CCDs have charge transfer inefficiencies of less than 10^-6, and dark current of le-/pixel/second at the REXIS operating temperature of -60 degrees C. The resulting spectral resolution is 115 eV at 2 KeV. The extinction ratio of the filter is ~10^12 at 625 nm.
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Summary

The Regolith x-ray Imaging Spectrometer (REXIS) is a coded-aperture soft x-ray imaging instrument on the OSIRIS-REx spacecraft to be launched in 2016. The spacecraft will fly to and orbit the near-Earth asteroid Bennu, while REXIS maps the elemental distribution on the asteroid using x-ray fluorescence. The detector consists of a...

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Broadband (200-1000 nm) back-illuminated ccd imagers

Summary

Improved and stable blue/UV quantum efficiency has been demonstrated on 2Kx4K imagers using molecular-beam epitaxy to create a thin doped layer on the back surface. Quantum efficiency data on thick (40-50 pm) imagers with single and dual-layer anti-reflection coatings is presented that demonstrates high and broadband response. Measurements of the optical point-spread response show the devices to be fully depleted with good response across a broad spectrum, but interesting features appear in the near-IR as a result of deeply penetrating light being scattered off the surface structure of the CCD.
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Summary

Improved and stable blue/UV quantum efficiency has been demonstrated on 2Kx4K imagers using molecular-beam epitaxy to create a thin doped layer on the back surface. Quantum efficiency data on thick (40-50 pm) imagers with single and dual-layer anti-reflection coatings is presented that demonstrates high and broadband response. Measurements of the...

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