Toward fast, low-noise charge-coupled devices for Lynx

Abstract

Lynx requires large-format x-ray imaging detectors with performance at least as good as the best current-generation devices but with much higher readout rates. We are investigating an advanced chargecoupled device (CCD) detector architecture under development at MIT Lincoln Laboratory for use in the Lynx high-definition x-ray imager and x-ray grating spectrometer instruments. This architecture features a CMOScompatible detector integrated with parallel CMOS signal processing chains. Fast, low-noise amplifiers and highly parallel signal processing provide the high frame rates required. CMOS-compatibility of the CCD enables low-power charge transfer and signal processing. We report on the performance of CMOS-compatible test CCDs read at pixel rates up to 5.0 Mpix s −1 (50 times faster than Chandra ACIS CCDs), with transfer clock swings as low as 1.0-V peak-to-peak (power/gate-area comparable to ACIS CCDs at 100 times the parallel transfer rate). We measure read noise of 4.6 electrons RMS at 2.5 MHz and x-ray spectral resolution better than 150-eV full-width at half maximum at 5.9 keV for single-pixel events. We report charge transfer efficiency measurements and demonstrate that buried channel trough implants as narrow as 0.8 μm are effective in improving charge transfer performance. We find that the charge transfer efficiency of these devices drops significantly as detector temperature is reduced from ∼ − 30°C to −60°C. We point out the potential of previously demonstrated curved-detector fabrication technology for simplifying the design of the Lynx high-definition imager. We discuss the expected detector radiation tolerance at these relatively high transfer rates. Finally, we note that the high pixel "aspect ratio" (depletion depth: pixel size ≈9∶1) of our test devices is similar to that expected for Lynx detectors and discuss implications of this geometry for x-ray performance and noise requirements. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Lynx X-Ray Observatory: an overview

“…X-ray mirror technologies that were studied in detail by the Lynx team included silicon meta-shell optics developed by GSFC, 4 fullshell optics developed by Brera (INAF/Brera) and Marshall Spaceflight Center (MSFC), 5,6 and adjustable segmented optics developed by the SAO. 7,8 Similarly, multiple technologies were studied for the large-scale active sensor pixel array, dubbed the high-definition x-ray imager (HDXI) [9][10][11][12] and for the XGS. 13,14 The Lynx x-ray microcalorimeter (LXM) [15][16][17][18][19][20][21] is singular but has elements that have multiple candidate technologies.…”

“…HDXI detector candidate technologies are described in detail in this paper and elsewhere in the literature. [9][10][11][12] These detectors will be able to provide a low-noise, wide FOV, high-count rate capability (8000 ct s −1 ) option and will be able to support the high-angular resolution required by Lynx with ∼0.3 arc sec pixels. Key requirements for Lynx and ATHENA APS arrays compared to Chandra's ACIS-I array are summarized in Table 2.…”

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

“…12 We have been developing advanced CCDs for use in Lynx. 13 CCDs are one of three types of imaging sensor, along with hybrid 14,15 and monolithic 16 CMOS active pixel detectors, considered for this mission. Our work, which also has potential applications in probe-class, Explorer and small missions, has focused on demonstrating fast, low-noise output amplifiers, low-power charge-transfer clocking, and development of appropriate application specific circuits.…”

Development and characterization of a fast and low noise readout for the next generation X-ray CCDs

“…Most of the requirements are also met with the proven technology of X-ray CCDs, with the aforementioned of exception of readout speed. Recently, however, papers [14,15,16] have reported significant progress in the development of low power, high speed X-ray CCDs. In particular, MIT Lincoln laboratory (MIT-LL) is developing CCDs with fast, low-noise on-chip amplifiers and gate electrodes formed with a single-level polysilicon process that enable low power operation of the CCDs.…”

“…Stanford University is collaborating with MIT and MIT-LL to develop fast readout electronics to characterize these CCDs and optimize their noise performance. A detailed overview of the CCDs can be found in [14,15,16]. Here we describe the readout module designed to run the CCDs at high readout speeds, and discuss the spectroscopic and noise performance.…”