Detector Modelling Workshop 2021 (DeMo)

14 Jun 2021, 12:55 → 16 Jun 2021, 18:10 Europe/Zurich

Online

Benoit Serra (ESO), Elizabeth George (ESO), Frederic Lemmel (ESA), Matej Arko (ESA), Thibaut Prod'homme (European Space Agency)

 

About the workshop

The Detector Modelling workshop aims to bring together the community of scientists and engineers who are interested in modelling of detector effects for astronomy. The workshop will be held online on 14th-16th June 2021 in the afternoons (CET).

The workshop is being organised by the Pyxel detector simulation framework developers based at ESO and ESA. The days are organised around blocks of  contributed talks from the community covering a range of topics related to detector modelling as well as tutorial sections on using Pyxel. 

Attendance is open to all, and early career scientists who may be interested in getting involved in Pyxel are especially encouraged to attend. Have you worked on any aspect of detector modelling? Register for DeMo, submit an abstract if you'd like to present your work, and join us for a few afternoons of discussion and exchange on this exciting topic.

Pyxel website

 

Monday, 14 June

Welcome and Introduction

Convener: Benoit Serra (ESO)

1 Welcome and Logistics

Welcome and logistics for the DeMo 2021 Online Workshop.

Speaker: Thibaut Prod'homme (European Space Agency)

20210614-demo2021-intro.pdf

2 Introduction to the Detector Modelling Workshop

Detector modelling serves many purposes from highly technical physics-based simulations to gain deep understanding of detector properites to phenomenological models to approximate detector behaviour in order to calibrate science data or perform systems-level tradeoffs. As the science goals of the astronomy community become ever more ambitious and require unprecedented levels of accuracy, the ability to understand, simulate, and correct for a range of detector effects is now required. But the level of detail in simulation depends on the use case for the simulation. During this conference you will hear from experts working in all areas of detector modelling and learn about different resources for modelling detectors, many of which are open-source and freely available.

Speaker: Elizabeth George (ESO)

20210614_Intro_to_conference_for_online_archiving.pdf

Optical/IR Instrument simulators 1

Convener: Frederic Lemmel (ESA)

3 How we simulate Euclid

Euclid is an ESA mission to map the geometry of the Universe and better understand the dark matter and dark energy properties in the universe. The mission will investigate the distance-redshift relationship and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies. To explore these two scientific probes, the 1 meter telescope is equipped with two instruments: a wide field imager in the optical (half a square degree), and a spectro-imager in the near infrared. In preparation for survey data after launch, image simulations are used to evaluate the impact of instrument characteristics and support the development of analysis pipelines. In combination with cosmological simulations, they enable an end-to-end performance analysis from an input cosmology to reconstructed cosmological parameters.
We will shortly present the work of the simulation group and then focus on the simulation of the space telescope's two instruments.

Speakers: Patrick Hudelot (CNRS), Dr Gregor Seidel (MPIA)

2021_06_DeMo2021_gregor_seidel.pdf

Demo2021.pdf

4 MicadoWISE: integrating the ScopeSIM simulator with processing and archive prototypes for MICADO

New instruments, such as MICADO, the Multi-AO Imaging Camera for Deep Observations on the ELT, the Extremely Large Telescope, require the instrument hardware and the data processing software to be designed in tandem to maximize the desired performance.

MicadoWISE integrates the ScopeSIM simulator with the data processing and archive prototypes for MICADO to efficiently validate that our science goals can be met with the design of both the hardware and the software.

Properties of the detector (and instrument, telescope, observatory, or atmosphere) can be varied to test the limits of the data processing software; thereby giving an objective measure of whether the hardware and software design is satisfactory.

Speaker: Hugo Buddelmeijer

DeMo2021-HB-ScopeSIM-MicadoWISE.20210614.pdf

Hugo Buddelmeijer - ScopeSIM + MicadoWISE google slides

Hugo Buddelmeijer - ScopeSIM + MicadoWISE repository

5 Detector Effects Simulation For CSST

The China Space Station Telescope (CSST) will be a major component of the China Manned Space Station after it be launched around 2024. Data processing system and observation/image simulation for CSST have started their development works. The image simulation system has designed an overall framework which supports different aspects of simulation including celestial sources like galaxies/stars, telescope and PSF field, camera module and detector effects, and so on. For detector effects, it has considered QE, PRNU, dark current, 16 channel readout and noises, bias, gain, dark and hot pixels/columns, brighter-fatter effect, electron diffusion, CTE, saturation and blooming, etc. These effects are added in a phenomenological way (currently), and almost all of the parameters are based on specifications. As we are close to the qualification model test experiment, more details can be witnessed and parameters be confirmed.

Speaker: Xianmin Meng (NAOC)

Detector_Effects_Simulation_For_CSST_MXM_20210712.pdf

14:35 Screen-free Coffee break

Detector Measurements/Models 1

Convener: Bradley Kelman (OU)

6 C3TM: Charge transfer model for radiation damaged CCDs

The radiation environment outside the Earth’s magnetosphere is an issue for most space-based detectors. Highly energetic particles from the Sun can damage Charge-Coupled Devices (CCDs) by creating defects in their silicon lattice. These defects are able to trap electrons during the read out of the CCD and thus create a smearing effect that is detrimental to the scientific data.

The Centre for Electronic Imaging (CEI) CCD Charge Transfer Model (C3TM) has been created to simulate the physical processes taking place when transferring signal through a radiation damaged CCD. C3TM is a Monte Carlo model based on Shockley-Read-Hall theory, and mimics the physical properties in the CCD as closely as possible. To avoid making any analytical assumptions about the size and density of the charge cloud, the model takes device specific simulations of electron density as a direct input. It runs on a single electrode level and each trap can be specified with emission time constant, emission and capture cross sections, and three-dimensional positional information. The model is therefore also able to simulate multi-level clocking and other complex clocking schemes, such as trap pumping.

The C3TM will deliver input to the radiation correction efforts for the VISual instrument on ESA’s Euclid mission, however, the code has been made such that it can be easily be adapted to detectors for other instruments. I will present some of the results that C3TM has produced and will show how laboratory data and simulated data can be compared to further our understanding of the positions and properties of individual radiation-induced traps, and how they affect space-borne CCD performance.

Speaker: Dr Jesper Skottfelt (Open University)

Jesper-Skottfelt_C3TM-DeMo_Workshop-2021.pdf

7 Modelling the interference in infrared detector arrays

The constructive and destructive interference of infrared light in detector arrays, used in both ground-based and space-based infrared astronomical instruments, is a complex and impactful systematic to characterise. For broadband imaging the interference can enlarge the instrument point spread function significantly, while for medium-to-high resolution spectroscopy it can introduce a large amplitude modulation on the spectral baseline, which is unresolved in low-resolution spectrometers. Correction of this effect has usually consisted of empirical corrections using tailored observations of calibration lamps and celestial standards, resulting in a significant investment in operation time as well as a higher mission cost. Despite the effect manifesting in complex ways, it is possible to model it using as input the physical properties of the detector-constituting layers. This can provide an initial estimate for the magnitude of the systematic effect, as well as allow to better understand the optical behaviour of the detector-plus-instrument system as a whole. As part of my research I have modelled the interference in the detector arrays of the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). This work has shed light on a list of seemingly unrelated calibration issues, which turned out to be facets of the same underlying phenomenon. In hindsight, the availability of a generic tool to model the interference in the detector layers would have had a non-negligible impact on the optical design of MIRI. Future generation infrared instruments can benefit greatly from a better understanding of the interaction between infrared light and detector structures; we can use the knowledge gained over decades of infrared instrumentation to provide to the community the necessary tools to address this important issue.

Speaker: Dr Ioannis Argyriou (KU Leuven Association)

DetectorModelingPresentation_IoannisArgyriou.pdf

8 HxRGprocc: Modelling non-linearity of H2RG detector in HPF

HxRGprocc is a general open source tool we built to simulate as well as reduce HxRG up-the-ramp data. In this talk, I shall mainly focus on the empirical models we developed to fit the pixel by pixel non-linearity curves of the H2RG detector pixels in the Habitable zone Planet finder spectrograph which uses a 1.7 micron H2RG detector. I shall also talk about the other features in HxRGprocc, which is now currently used for reducing up-the-ramp data in multiple instruments.

Speaker: Joe Ninan (The Pennsylvania State University)

HxRGproc Non linearty modeling in HxRG.pdf

16:05 Screen-free Coffee break

Introducing Pyxel

Conveners: Benoit Serra (ESO), Frederic Lemmel (ESA), Matej Arko (ESA)

9 Pyxel: the collaborative detection simulation framework

Pyxel is a novel python tool for end-to-end detection chain simulation i.e. from detector optical effects to readout electronics effects. It is an easy-to-use framework to host and pipeline any detector effect model. It is suited for simulating both Charge-Coupled Devices, CMOS Image Sensors and Mercury Cadmium Telluride hybridized arrays. It is conceived as a collaborative tool to promote reusability, knowledge transfer, and reliability in the instrumentation community. We will provide a demonstration of Pyxel’s basic principles, describe newly added capabilities and the main models already implemented, and give examples of more advanced applications.

Speaker: Thibaut Prod'homme (European Space Agency)

20210614-demo2021-pyxel-v1.pdf

10 Pyxel Tutorial - Part 1

In the first tutorial session on Pyxel we present all the necessary information needed to start working with the tool. We give a simple demonstration of the Pyxel's single mode using Pyxel tutorial notebooks and see how the configuration file is structured. We apply a number of implemented models to a single image and check the outputs. In the end we provide a guide for on how to add a new model to the framework.

Speakers: Frederic Lemmel (ESA), Matej Arko (ESA), Benoit Serra (ESO)

20210614_Pyxel-Tutorials-Intro.pdf

Tuesday, 15 June

X-ray Instrument Simulators

Convener: Thibaut Prod'homme (European Space Agency)

11 Introducing X-DECIMO, a Python package for detector simulation emphasizing 2D X-ray detectors

The X-DECIMO tool is being used and further developed at ESRF to model and simulate the full detection and signal processing chain of current and future X-ray detectors for synchrotron radiation applications. This tool is a modular Python package in which the specific detectors are modeled and built by plugging and connecting together individual components. The generation of X-rays as well as the core and first part of the simulation is based on Monte Carlo techniques. The detection chain is completed when needed with additional modules for further processing of the Monte Carlo results to include, for instance, detector calibration corrections or to proceed on-the-fly with the analysis of the simulation results.
The presentation will introduce briefly the purpose, overall concept and implementation of X-DECIMO and and some technical choices that could be potentially interesting for the audience. It will also briefly present examples of how this tool is being used to evaluate in advance and support the development at ESRF of a new generation of 2D X-ray detectors.

Speaker: Pablo Fajardo (ESRF)

DeMo_workshop_2021_XDECIMO.pdf

12 SIXTE: a generic X-ray instrument simulation toolkit

We present the SImulation of X-ray TElescopes (SIXTE) software package, a generic, mission-independent Monte Carlo simulation toolkit for X-ray astronomical instrumentation. The package is based on a modular approach for the source definition, the description of the optics, and the detector type such that new missions can be easily implemented. The targets to be simulated are stored in a flexible input format called SIMPUT. Based on this source definition, a sample of photons is produced and then propagated through the optics. In order to model the detection process, the software toolkit contains modules for various detector types, ranging from proportional counter and Si-based detectors, to more complex descriptions like TES devices. The implementation of characteristic detector effects and a detailed modeling of the read-out process allow for representative simulations and therefore enable the analysis of characteristic features, such as for example pile-up, and their impact on observations. Dedicated and detailed instrument simulators like "xifusim" are used to create specific input data to allow for very detailed instrument simulations, while at the same time being fast enough to simulate long observations without requiring extensive computing resources. In order to demonstrate the capabilities of the simulation software, we present a selection of representative applications, including the all-sky survey of eROSITA, a study of pile-up effects comparing the currently operating XMM-Newton with the planned Athena-WFI instrument, and a galaxy cluster simulation with the micro-calorimeter Athena X-IFU.

Speaker: Thomas Dauser (Universität Erlangen-Nürnberg (FAU))

dauser_sixte.pdf

13 The Athena X-IFU instrument simulator xifusim

We present the instrument simulator $\texttt{xifusim}$ developed for the X-ray Integral Field Unit (X-IFU), an X-ray microcalorimeter aboard the planned ESA mission $\textit{Athena}$. The goal of the X-IFU is to perform spatially resolved spectroscopy from 0.2 to 12 keV over a field of view of 5' equivalent diameter, with a spectral resolution of 2.5 eV up to 7 keV on 5" pixels.

The main purpose of $\texttt{xifusim}$ is to be a performance study tool to reach these goals and to provide input for higher level simulators such as the SIXTE simulation toolkit. As such, it aims to be an accurate representation of the entire instrument, starting from a full numerical simulation of the Transition-Edge Sensor array receiving impact photons. Its output signal is then propagated through the entire readout chain, including multiplexing, amplification and digital readout. The final output consists of triggered records, which can be post-processed to reconstruct the photon energies.

In the code, the readout chain itself is separated into individual, modular blocks with several possible models for each, allowing the simulation of different readout schemes or models of varying physical accuracy at the expense of runtime. New models are implemented as necessary to enable studies of the overall readout chain. Such studies are also facilitated by fine-grained control of the simulation output, including the internal state of intermediate simulation blocks. Additional interfaces to manipulate certain internal parameters during a run also allow the simulation of readout chain characterization measurements, environmental drifts and certain kinds of crosstalk.

Speaker: Christian Kirsch (FAU Erlangen-Nürnberg)

DeMo_xifusim.pdf

14:15 Screen-free Coffee break

Optical/IR instrument simulators 2

Convener: Elizabeth George (ESO)

14 PlatoSim

We present the PLATO simulator (PlatoSim). PlatoSim is a state-of-the-art software simulator that generates realistic observations for EAS's upcoming medium-class space mission "PLATO". The mission will gather high-precision (ppm-level) photometric time series using CCDs, with the primary objective to detect and characterize exoplanets. We provide a concise description of the different building blocks that make up the simulator framework. This includes the attitude stability of the spacecraft, the characteristics of the optics and the CCD, and astrophysical noise sources. Examples of this that will be discussed include the platform jitter, telescope drift, a realistic position-dependent point-spread-function, natural and mechanical vignetting, particle contamination, field distortion, charge-transfer inefficiency, the brighter-fatter-effect, polarisation, open shutter smearing, full-well saturation, readout noise, etc. We discuss the implementation of these and future features and their respective computational performance challenges that are needed to assess ppm-level photometry.

Speaker: Dries Seynaeve (KU Leuven Association)

PlatoSimDeMo.pdf

15 Modeling JWST detectors in the Pandeia Engine

The Pandeia Engine is the computational core of the JWST Exposure Time Calculator. Where most exposure time calculators operate on the spectrum and flux of a source, the Pandeia Engine is a fully 3D exposure time calculator, considering the spatial component of the observation, and allowing for multiple sources. The Pandeia Engine generates a scene at the pixel level, and derives its results by conducting flux extraction of the resulting synthetic image in a manner analogous to post-observation data processing. While it is not a simulator, and ignores many complexities in the interests of simplicity and calculation time, it does take into account multiple detector effects in pursuit of scientifically useful exposure time estimates. In my talk, I will describe how the Pandeia Engine constructs scenes and then represents them as synthetic JWST detector images.

Speaker: Dr Adric Riedel (STScI)

Pandeia DeMo Presentation.pdf

16 PhoSim: A Tool to Simulate Astronomical Images

We describe the Photon Simulator (PhoSim), a code to simulate detailed astronomical images. PhoSim follows photons from astronomical sources, through the atmosphere and interactions with telescope optics, and converts as electrons in detectors. PhoSim uses the appropriate photon interactions and describes the atmosphere by hydrodynamics descriptions, telescope optics by elasticity theory, and detectors by electrostatics. PhoSim uses novel Monte Carlo algorithms and efficient multithreaded enabling images to be produced as fast as conventional parametric approaches. We highlight some recent work in PhoSim detector physics where electrostatic descriptions are used to reproduce charge diffusion, chromatic effects, edge distortion, sub-linear variance, intensity-dependent diffusion, tree rings, and cosmic rays. PhoSim is flexible, has extensive documentation, and can be used for a variety of telescopes and laboratory configurations.

Speaker: John Peterson (Purdue University)

phosim_peterson_demo_2021.pdf

17 Science data simulations for SPHEREx, NASA's all-sky near-infrared spectral survey

SPHEREx is a NASA Astrophysics Explorer mission to produce a near-infrared all-sky spectrophotometric survey. The 2-year mission will measure spectra of every 6-arcsecond pixel on the sky between 0.75 and 5 microns at spectral resolution varying between R=35 and 130. SPHEREx’s instrument is based on a 30-cm off-axis telescope feeding six Teledyne H2RG detectors behind linear variable filters. The mission is optimized to address three science themes: 1. Inflation in the early Universe through large scale structure, 2. the history of galaxy formation by measuring spectra of the extragalactic background fluctuations, and 3. the inventory of biogenic ices in our own galaxy by surveying ice spectral absorption features towards stars.

To help define mission requirements, define error budgets, and develop science data pipeline software, the SPHEREx Science Team has created a Sky Simulator software package to generate realistic simulated data products incorporating diffuse and compact sky signals, and applying effects introduced by the instrument to create simulated realizations of the unique data products that SPHEREx will create. This talk will present the overall approach and structure of the Sky Simulator software, how it has been used within the mission, and the next steps.

Speaker: Brendan Crill (Jet Propulsion Laboratory / California Institute of Technology)

SPHEREx_Sky_Simulator_Crill.pdf

16:10 Screen-free Coffee break

Pyxel hands-on

Conveners: Benoit Serra (ESO), Frederic Lemmel (ESA), Matej Arko (ESA)

18 Pyxel Tutorial - Part 2

In the second Pyxel tutorial session we take a deeper look into the three advanced modes of using Pyxel through different Jupyter notebook examples. The three modes are: parametric for running the pipeline multiple times looping over a range of parameters, dynamic for simulating time-dependent effects, and calibration for optimizing models or detector parameters to fit target data sets.

Speakers: Matej Arko (ESA), Benoit Serra (ESO), Frederic Lemmel (ESA)

Wednesday, 16 June

Detector Measurements/Models 2

Convener: Elizabeth George (ESO)

19 Model of HgCdTe SWIR integration ramp for constant flux integration and persistence current

For low flux Short Wave Infrared detection in astronomy, focal plane arrays are usually based on an HgCdTe detection layer flip-chipped onto a Silicon ROIC. To meet the low noise specification on these detectors, Source Follower per Detector (SFD) pixel architecture is maximizing the conversion gain, thus reducing the ROIC noise. However, this architecture gives intrinsically a non-linear conversion from accumulated charge to measured voltage during the integration. This non-linearity can be tedious to calibrate and leads to uncertainties on the estimated detected flux.
We propose a physical model to estimate such integration ramp from the initial voltage to its saturation. Applied on measurements performed on imagers manufactured at CEA and Lynred, we discuss on this approximation uncertainties and the way to constrain its physical parameters.
Based on this SFD pixel ramp modeling for a constant flux, we also address the persistence issue that plagues IR detectors for astronomy. The traditional hypothesis used to explain this phenomenon is based on trapping/emission processes from deep level defects in the space charge region (SCR) of the diode. Inspired from Deep Level Transiant Spectroscopy (DLTS) formalism, we developed a physical model describing trap emission current from the SCR of the diode in a SFD pixel. Reporting on point defect and extended defect, we found that this model can describe low persistence signal. However, the trap density has to be close to the doping density to account for higher persistence amplitude. This implies that the N region of the diode would be compensated, which is an extreme scenario out of the scope of this model.

Speaker: Mr Titouan LE GOFF (CEA Leti)

DeMo_LeGoff - SFD current and persistance modelisation.pdf

20 An Automated Algorithm for Persistence Correction in an Operational Environment

Persistence is the effect whereby a remnant signal from a previous exposure is imprinted on a subsequent image. This effect has long been known to affect HgCdTe near-infrared detectors and, if severe, the persistence artefacts can last several hours or even days, rendering subsequent observations nearly useless. Historically, ESO has addressed persistence by strongly limiting the exposure levels of its detectors and hoping that this limit is never accidentally exceeded. However, in the era of the ELT this simple approach is no longer viable.
Using the detector characterisation provided by the ESO Detector Group, we are developing an automated routine that computes a persistence map for each science exposure. With an in-depth understanding of the detector’s unique persistence characteristics, our routine maps the accumulated trapped charges and their subsequent decay through the exposure history, prior to any given science image.
The intent is to make each persistence map available from the ESO archive as an associated calibration attached to each science exposure. In this way, we have converted the measurements, and models of individual detector effects to a practical procedure that can significantly reduce the impact of detector effects on science instruments.

Speaker: Dr Mark Neeser (ESO)

DeMo_Persistence_MNeeser.pdf

21 Tearing and mitigation in the LSST Focal Plane

In the baseline operating mode, flat-field images taken with the 16-channel, 16 Mpix Teledyne-e2v CCD sensors of the LSST camera exhibit tearing, and other related effects caused by lateral distortions in the sensor drift field. These particular distortions are explained by the non-uniform distribution of holes in the channel stops between sensor columns, which has been modelled. After assembly of the full focal plane, we have tested several mitigation strategies, with some practical limitations due to our sensors and readout electronics. Our results highlight additional effects originating at the boundaries of the image area.

Speaker: Dr Claire Juramy-Gilles (LPNHE / IN2P3 / CNRS)

Tearing_DeMo2021.pdf

14:15 Screen-free Coffee break

Particles and Radiation Modelling

Convener: Thibaut Prod'homme (European Space Agency)

22 Allpix Squared - Silicon Detector Monte Carlo Simulations for Particle Physics and Beyond

Allpix Squared is a versatile, open-source simulation framework for silicon pixel detectors. Its goal is to ease the implementation of detailed simulations for both single sensors and more complex setups with multiple detectors. While originally created for silicon detectors in high-energy physics, it is capable of simulating a wide range of detector types for various application scenarios, e.g. through its interface to Geant4 to describe the interaction of particles with matter, and the different algorithms for charge transport and digitization. The simulation chain is arranged with the help of intuitive configuration files and an extensible system of modules, which implement the individual simulation steps. Detailed electric field maps imported from TCAD simulations can be used to precisely model the drift behavior of the charge carriers, bringing a new level of realsim to the Monte Carlo simulation of particle detectors.

Recently, Allpix Squared has seen major improvements to its core framework to take full advantage of multi- and many-core processor architectures for simulating events fully parallel. Furthermore, new physics models such as charge carrier recombination have been introduced, further extending the application range. This contribution provides an overview of the framework and its components, highlighting the versatility and recent developments.

Speaker: Simon Spannagel (Deutsches Elektronen-Synchrotron (DE))

2021-06-16-ESA-ESO-DeMo_Worksop-APSQ.pdf

23 CosmiX and beyond - Simulating particle tracks in image sensors and microelectronics

In this talk, the CosmiX cosmic ray model will be presented, and in general the Monte Carlo simulations of ionizing particle tracks in image sensors, as well as in microelectronics will be discussed.

Speaker: Mr David Lucsanyi (CERN)

David-Lucsanyi-CosmiX-G4SEE-DeMo.pdf

24 Modelling of proton irradiation induced luminescence of CdZnTe substrate in HgCdTe detectors

The French Alternative Energies and Atomic Energy Commission (CEA) is deeply implied in the development of ALFA (Astronomical Large Format Arrays), a 2048x2048 short-wave infrared (SWIR) detector array with a 15 µm pixel pitch and a cutoff wavelength of 2.1 µm. The development is mainly funded by the European Space Agency (ESA), for the future space missions, and by the French national research agency. Since ALFA is dedicated to space applications, it has to be hardened against radiation effects. It is therefore essential to understand the effects of space radiations on these IR detectors. In particular, in addition to the study of energy deposition directly into the HgCdTe sensitive layer, it is mandatory to address the effects of particles energy deposition first in the CdZnTe substrate for detector structures where the substrate is not completely removed.
Here we present the model we have developed describing luminescence induced by proton energy deposition in the CdZnTe substrate of HgCdTe infrared detectors for space applications. The estimation of image pollution is performed with the use of GEANT4 Monte Carlo simulation and both analytical and numerical calculations of carrier diffusion inside the detector. Recombination processes are taken into account to modelled luminescence effect induced by proton irradiation.
Luminescence experiments and ellipsometry measurements are used as input parameters to model the response of the detector under irradiation. Simulated images have been confronted with real images acquired with real detectors during an irradiation campaign. During this experiment two detectors with different substrate thicknesses, 50 µm and 800 µm, have been irradiated with 62 MeV protons. The simulations are in good agreement with the results of the experiment, which validates the model we have developed. The comparison of the model with the experience will also be presented.

Speaker: Thibault PICHON (CEA)

Demo2021_Pichon_vf.pdf

15:45 Screen-free Coffee break

Detector Measurements/Models 3

Convener: Bradley Kelman (OU)

25 Variation of Inter-pixel Capacitance in H4RG Detector

Inter-pixel capacitance (IPC) is an important parameter which needs to be measured accurately so that the required corrections can be applied to the measured conversion gain and hence all the derived detector performance characteristics. Different methods such as auto-correlation, absolute capacitance, hot-pixel, cosmic ray hits or single-pixel reset methods can be used to measure the inter-pixel capacitance of a detector. However, these methods measure the average IPC over the array or do not show if there are any variations in the IPC along the columns or the rows of the detector. A robust method has been used at ESO on a H4RG detector to determine if any variation of IPC across the array by implementing multiple column / row resets. We find the IPC indeed show variation across the array and the measured IPC is also dependent on readout / reset method employed. In addition, the glue voids at pixel level presents ice-crystal shaped filament features as they have a different gain and coupling to their neighboring pixels. The complex behavior of IPC would need to be taken into account in the detector modelling so that its effect on science can be assessed. This talk will present the measurement method used and the IPC results from an engineering H4RG-15 detector.

Speaker: Dr Naidu Bezawada (ESO)

DeMo2021_Spatial_variation_of_IPC_NaiduBezawada.pdf

26 Non-linear effects in H4RG-10 detectors

The Nancy Grace Roman Telescope is an upcoming NASA observatory that will investigate the origins of cosmic acceleration using weak gravitational lensing (WL). WL induces percent-level distortions in galaxy shapes, and accurate WL measurements are highly sensitive to the point-spread function (PSF). Thus, it is essential to characterize detector effects, particularly nonlinear behaviors that may impact the PSF such as the brighter-fatter effect (BFE). The non-destructive readout capability of the H4RG-10 detectors enables correlation measurements on flat field data not only between pixels but also between time frames. I will describe how we recently measured and modelled correlations in flat field data (from Goddard's Detector Characterization Laboratory) for candidate flight detectors and discuss the path toward calibration of Roman data.

Speaker: Dr Ami Choi (OSU)

AmiChoi_DeMo_16June2021.pdf

27 Modeling the e-APD SAPHIRA/C-RED ONE camera at a low flux level

We implemented an electron avalanche photodiode (e-APD) in the MIRC-X instrument, which is an upgrade of the six-telescope near-infrared imager MIRC, at the CHARA array. This technology improves the sensitivity of near-infrared interferometry.

We aim to characterize a near-infrared C-RED ONE camera from First Light Imaging (FLI) using an e-APD from Leonardo (previously SELEX).

We first used the classical mean-variance analysis to measure the system gain and the amplification gain. We then developed a physical model of the statistical distribution of the camera output signal. This model is based on multiple convolutions of the Poisson statistic, the intrinsic avalanche gain distribution, and the observed distribution of the background signal. At a low flux level, this model independently constrains the incident illumination level, the total gain, and the excess noise factor of the amplification.

We measure a total transmission of $48\pm3\%$ including the cold filter and the Quantum Efficiency.
We measure a system gain of 0.49 ADU/e, a readout noise of $10$ ADU, and amplification gains as high as 200. These results are consistent between the two methods and therefore validate our modeling approach. The measured excess noise factor based on the modeling is $1.47\pm0.03$, with no obvious dependency with flux level or amplification gain.

The presented model allows the characteristics of the e-APD array to be measured at a low flux level independently of a preexisting calibration. With $<0.3$\,electron equivalent readout noise at kilohertz frame rates, we confirm the revolutionary performances of the camera with respect to the PICNIC or HAWAII technologies. However, the measured excess noise factor is significantly higher than what is claimed in the literature ($<$1.25), and explains why counting multiple photons remains challenging with this camera.

Speaker: Cyprien Lanthermann (CHARA - Georgia State University)

DeMo2021.pdf

Conference Closing Remarks

Conveners: Benoit Serra (ESO), Elizabeth George (ESO), Frederic Lemmel (ESA), Matej Arko (ESA), Thibaut Prod'homme (European Space Agency)

28 Conference Closing Remarks

Summary and wrap-up of DeMo 2021, closing remarks, and open-floor for any remaining questions.

Speakers: Benoit Serra (ESO), Elizabeth George (ESO), Frederic Lemmel (ESA), Matej Arko (ESA), Thibaut Prod'homme (European Space Agency)

20210616_Pyxel-Closing-Remarks.pdf