Development of MOS CCDs for the next generation of X-ray observatories

Abstract

The new millennium will see the launch of the next generation of X-ray observatories. As well as more specialised cryogenic detectors, observatories such as XEUS and Constellation-X will require large arrays of medium spectral resolution detectors, covering large focal planes with a good response over the 0.1–15 keV energy range. The MOS CCD that has been developed for the XMM, ASCA, ASTRO-E and AXAF observatories, with its proven record as an imaging X-ray spectrometer, will be the ideal detector for this role. In this paper we present the state-of-the-art performance being achieved using the XMM/EPIC CCDs and consider further developments that will be build upon existing technologies to ensure the CCD will meet the needs of the future observatories. In particular we discuss: comparisons of CCD surface design, i.e. back illuminated versus open electrode versus thinned electrode: improving high-energy quantum efficiency via the use of fully depleted or extreme depleted silicon: faster readout (>1 MHz) with multiple low-noise amplifiers (<5 electrons rms) and further enhancement of the radiation hardness of CCDs, including 3-D modelling of the charge transfer process.