Comparing simulations and test data of a radiation damaged charge-coupled device for the Euclid mission

The visible imager instrument on board the Euclid mission is a weak-lensing experiment that depends on very precise shape measurements of distant galaxies obtained by a large charge-coupled device (CCD) array. Due to the harsh radiative environment outside the Earth’s atmosphere, it is anticipated that the CCDs over the mission lifetime will be degraded to an extent that these measurements will be possible only through the correction of radiation damage effects. We have therefore created a Monte Carlo model that simulates the physical processes taking place when transferring signals through a radiation-damaged CCD. The software is based on Shockley–Read–Hall theory and is made to mimic the physical properties in the CCD as closely as possible. The code runs on a single electrode level and takes the three-dimensional trap position, potential structure of the pixel, and multilevel clocking into account. A key element of the model is that it also takes device specific simulations of electron density as a direct input, thereby avoiding making any analytical assumptions about the size and density of the charge cloud. This paper illustrates how test data and simulated data can be compared in order to further our understanding of the positions and properties of the individual radiation-induced traps

Pyxel 1.0: an open source Python framework for detector and end-to-end instrument simulation

Detector modeling is becoming more and more critical for the development of new instruments in scientific space missions and ground-based experiments. Modeling tools are often developed from scratch by each individual project and not necessarily shared for reuse by a wider community. To foster knowledge transfer, reusability, and reliability in the instrumentation community, we developed Pyxel, a framework for the simulation of scientific detectors and instruments. Pyxel is an open-source and collaborative project, based on Python, developed as an easy-to-use tool that can host and pipeline any kind of detector effect model. Recently, Pyxel has achieved a new milestone: the public release and launch of version 1.0, which simplified third-party contributions and improved ease of use even further. Since its launch, Pyxel has been experiencing a growing user community and is being used to simulate a variety of detectors. We give a tour of Pyxel’s version 1.0 changes and new features, including a new interface, parallel computing, and new detectors and models. We continue with an example of using Pyxel as a tool for model optimization and calibration. Finally, we describe an example of how Pyxel and its features can be used to develop a full-scale end-to-end instrument simulator

Electro-optical characterization of a CMOS image sensor optimized for soft x-ray astronomy

CIS221-X is a prototype complementary metal-oxide-semiconductor (CMOS) image sensor, optimized for soft x-ray astronomy and developed for the proposed ESA Transient High Energy Sky and Early Universe Surveyor (THESEUS) mission. The sensor features 40 μm pitch square pixels built on a 35 μm thick, high-resistivity epitaxial silicon that is fully depleted by reverse substrate bias. Backside illumination processing has been used to achieve high x-ray quantum efficiency, and an optical light-blocking filter has been applied to mitigate the influence of stray light. A comprehensive electro-optical characterization of CIS221-X has been completed. The median readout noise is 3.3 e− RMS with 90% of pixels reporting a value − RMS. At −40 ° C, the dark current is 12.4 ± 0.06 e− / pixel / s. The pixel photo-response is linear to within 1% for 0.3 to 5 keV photons (82 to 1370 e−) with 80 % quantum efficiency. With the exception of dark current, these results either meet or outperform the requirements for the THESEUS mission, strongly supporting the consideration of CMOS technology for soft x-ray astronomy