Soft X-ray performance of an optimised charge-coupled device for astronomy

Buggey, T. W.; Randall, G.; Parsons, S.; Jones, L. S.; DeCaire, A. L.; Arnold, T.; Hetherington, O.; Holland, A. D. and Hall, D. J. (2024). Soft X-ray performance of an optimised charge-coupled device for astronomy. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1066, article no. 169636.

DOI: https://doi.org/10.1016/j.nima.2024.169636

Abstract

For the upcoming European Space agency (ESA)/Chinese Academy of Sciences (CAS) SMILE mission, launching in 2025, large-format soft X-ray optimised CCDs have been manufactured by Teledyne e2v, named the CCD370. The CCDs are approximately 8 cm × 8 cm and are comprised of 4510 × 4510 18 μm pitch pixels, with a store shield covering approximately 1/7th of the active imaging area to facilitate frame-transfer operation mode. To optimise quantum efficiency within the soft X-ray energy band, the device is 16 μm thick, back illuminated, and has an additional back surface passivation process. The focal plane of the soft X-ray imager (SXI) on the SMILE spacecraft will be comprised of 2 CCD370s, operating with 6 × 6 on-chip binning to mitigate against CTI-induced charge transfer losses and charge spreading throughout the 3-year mission lifetime.

As part of the pre-flight testing and calibration, a CCD370 was characterised at the PTB beamline at the BESSY 2 synchrotron in Berlin, and key metrics such as quantum efficiency and energy resolution in the 0.2–1.8 keV energy band were assessed. The quantum efficiency measurements show expected performance within specification for the instrument, and also match a transmission-layer QE model. The energy resolution is 68 ± 2 eV FWHM @ 1.2 keV, which is an improvement over the current generation of X-ray telescopes such as XMM-Newton, Chandra, and the Swift X-ray Telescope. Although competing technologies such as DEPFETs and scientific CMOS image sensors now have similar performance to CCDs, the performance shown here can still easily satisfy requirements for novel X-ray instruments, and can still be useful in future astronomy missions given the rich heritage, high technology-readiness-level, and maturity of the technology.

Plain Language Summary

The energy resolution and quantum efficiency (QE) of an optimised CCD for soft X-ray astronomy was measured at the BESSY 2 synchrotron at the PTB beamline. The QE measurements show expected performance within specification for the instrument, and also match a transmission-layer model. The energy resolution is 68 ± 2 eV FWHM @ 1.2 keV, which is an improvement over the current generation of X-ray telescopes such as XMM-Newton, Chandra, and the Swift X-ray Telescope.

Viewing alternatives

Metrics

Item Actions

Export

You can export this page using these formats Digital Object Identifier - DOI