Electron-multiplying Charge-coupled Device Research Articles

Bernoulli generalized likelihood ratio test for signal detection from photon counting images

Because exoplanets are extremely dim, an electron multiplying charge-coupled device operating in photon counting (PC) mode is necessary to reduce the detector noise level and enable their detection. Typically, PC images are added together as a co-added image before processing. We present a signal detection and estimation technique that works directly with individual PC images. The method is based on the generalized likelihood ratio test (GLRT) and uses a Bernoulli distribution between PC images. The Bernoulli distribution is derived from a stochastic model for the detector, which accurately represents its noise characteristics. We show that our technique outperforms a previously used GLRT method that relies on co-added images under a Gaussian noise assumption and two detection algorithms based on signal-to-noise ratio. Furthermore, our method provides the maximum likelihood estimate of exoplanet intensity and background intensity while doing detection. It can be applied online, so it is possible to stop observations once a specified threshold is reached, providing confidence for the existence (or absence) of planets. As a result, the observation time is efficiently used. In addition to the observation time, the analysis of detection performance introduced in the paper also gives quantitative guidance on the choice of imaging parameters, such as the threshold. Lastly, though our work focuses on the example of detecting point source, the framework is widely applicable.

Fast-ion Dα spectroscopy diagnostic at KSTAR.

A fast-ion Dα (FIDA) diagnostics system was installed for core and edge measurements on KSTAR. This system has two tangential FIDA arrays that cover both blue- and redshifted Dα lines (cold: 656.09nm) in active views along the neutral beam 1A centerline. The spectral band is 647-662.5nm, and it covers the Doppler shift of the emission from the maximum energy of the neutral beam (100 keV). A curved filter strip with a motorized stage adequately prevents saturation of the electron multiplying charge-coupled device signal by the cold Dα line from the plasma edge. From comparisons of the measured spectra and FIDASIM modeling code, the FIDA spectra are well matched quantitatively. Moreover, the first measurements show that the FIDA radiance agrees with the neutron rate in the time trace during external heating and perturbation. In addition, responses are observed in the core FIDA radiance during the edge-localized mode cycle.

Low-Light Photodetectors for Fluorescence Microscopy

Over the years, fluorescence microscopy has evolved and has become a necessary element of life science studies. Microscopy has elucidated biological processes in live cells and organisms, and also enabled tracking of biomolecules in real time. Development of highly sensitive photodetectors and light sources, in addition to the evolution of various illumination methods and fluorophores, has helped microscopy acquire single-molecule fluorescence sensitivity, enabling single-molecule fluorescence imaging and detection. Low-light photodetectors used in microscopy are classified into two categories: point photodetectors and wide-field photodetectors. Although point photodetectors, notably photomultiplier tubes (PMTs), have been commonly used in laser scanning microscopy (LSM) with a confocal illumination setup, wide-field photodetectors, such as electron-multiplying charge-coupled devices (EMCCDs) and scientific complementary metal-oxide-semiconductor (sCMOS) cameras have been used in fluorescence imaging. This review focuses on the former low-light point photodetectors and presents their fluorescence microscopy applications and recent progress. These photodetectors include conventional PMTs, single photon avalanche diodes (SPADs), hybrid photodetectors (HPDs), in addition to newly emerging photodetectors, such as silicon photomultipliers (SiPMs) (also known as multi-pixel photon counters (MPPCs)) and superconducting nanowire single photon detectors (SSPDs). In particular, this review shows distinctive features of HPD and application of HPD to wide-field single-molecule fluorescence detection.

Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 ± 2.2 μmFWHM with a zoom range of 5 ×. Also, the spatial resolution for the plutonium dioxide particle was 302.7 ± 4.6 µmFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha–beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.

Proton-induced traps in electron multiplying charge-coupled devices

Charge-coupled device (CCD)-based technologies exposed to high-energy radiation are susceptible to the formation of stable defects within the charge transfer channel that defer signal to subsequent pixels and limit the lifetime of the detector. Performance degradation due to these defects depends upon the interplay between the clock timings used to operate the device and the properties of defects introduced by irradiation. Characterization of both the type and number of post-irradiation defects makes it possible to minimize charge loss though the appropriate selection of clock timings for a given operating temperature. This technique has the potential to increase nominal mission lifetimes by several years for CCD-based instruments and is of particular significance to electron multiplying charge-coupled devices (EMCCDs) for photon counting applications where the effect of charge traps on low signal levels is expected to be most severe. We present a study of charge traps within CCDs, specifically within EMCCDs irradiated at room temperature to proton fluences up to and including 1.45 × 1010 p + / cm2 (74 MeV). Defects are characterized through the “single-trap pumping” technique, with clocking schemes specifically designed for the 2-phase pixel architecture of the EMCCD. Five dominant trap species are thought to be introduced by the irradiation, the Si-E center, Si-A center, double and single acceptor charge states of the silicon divacancy (VV − − , VV − ), and an as yet unidentified defect referred to here as the Si-U center (the “unknown” trap). Energy-level and cross-section values are presented that allow inference of the defect landscape for a range of proton fluences and operating temperatures. While the study focuses specifically on EMCCDs, in more general terms, the results for trap properties are interpreted as being applicable to all CCD types following irradiation and can serve as a foundation for future charge loss correction and optimization techniques.

Detectivity optimization to measure ultraweak light fluxes using an EM-CCD as binary photon counter array

For a wide range of purposes, one faces the challenge to detect light from extremely faint and spatially extended sources. In such cases, detector noises dominate over the photon noise of the source, and quantum detectors in photon counting mode are generally the best option. Here, we combine a statistical model with an in-depth analysis of detector noises and calibration experiments, and we show that visible light can be detected with an electron-multiplying charge-coupled devices (EM-CCD) with a signal-to-noise ratio (SNR) of 3 for fluxes less than 30,{text{photon}},{text{s}}^{ - 1} ,{text{cm}}^{ - 2}. For green photons, this corresponds to 12 aW {text{cm}}^{ - 2} ≈ 9{ } times 10^{ - 11} lux, i.e. 15 orders of magnitude less than typical daylight. The strong nonlinearity of the SNR with the sampling time leads to a dynamic range of detection of 4 orders of magnitude. To detect possibly varying light fluxes, we operate in conditions of maximal detectivity {mathcal{D}} rather than maximal SNR. Given the quantum efficiency QEleft( lambda right) of the detector, we find { mathcal{D}} = 0.015,{text{photon}}^{ - 1} ,{text{s}}^{1/2} ,{text{cm}}, and a non-negligible sensitivity to blackbody radiation for T > 50 °C. This work should help design highly sensitive luminescence detection methods and develop experiments to explore dynamic phenomena involving ultra-weak luminescence in biology, chemistry, and material sciences.

Measurement and optimization of clock-induced charge in electron multiplying charge-coupled devices

Electron multiplying charge-coupled devices (EMCCDs) are a variant of standard CCD technology capable of single-optical photon counting at MHz pixel readout rates. For photon counting, thermal dark signal and clock-induced charge (CIC) are the dominant source of noise and must be minimized to reduce the likelihood of coincident events. Thermal dark signal is reduced to low levels through cooling or operation in inverted mode (pinning). However, mitigation of CIC requires precise tuning of both parallel and serial clock waveforms. Here, we present a detailed study of CIC within Teledyne-e2v EMCCDs with a goal of better understanding the physical mechanisms that dominate CIC production in both noninverted and inverted mode operations (IMO). Measurements are presented as a function of parallel and serial clock timings, clock amplitudes, and device temperature. The effects of radiation damage and annealing are also discussed. A widely accepted view is that CIC is signal generated through impact ionization of energetic holes as the clock phase is driven high. While this explanation holds for IMO, we propose that the majority of CIC generated in noninverted mode is in fact due to a secondary effect of light emission from hot carriers. The information from this study is then used to optimize CIC on Teledyne e2v CCD201s operating at 1-MHz pixel rate in NIMO. For the CCD201, we obtained total CIC levels as low as 6.9 × 10 − 4 e − / pix / frame with ≥90 % detective quantum efficiency. We conclude with proposals to further reduce CIC based upon modifications to clocking schemes and device architecture.

Double Image Polarimeter—Ultra Fast: Simultaneous Three-color (BV R) Polarimeter with Electron-multiplying Charge-coupled Devices

Abstract We describe a new instrument capable of high-precision (10−5) polarimetric observations simultaneously in three passbands (BVR). The instrument utilizes electron-multiplying charge-coupled device (EM CCD) cameras for high efficiency and fast image readout. The key features of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i) the optical design with high throughput and inherent stability; (ii) great versatility, which makes the instrument optimally suitable for observations of bright and faint targets; and (iii) a control system, which allows the use of the polarimeter remotely. Examples are given of the first results obtained from high signal-to-noise observations of bright nearby stars and of fainter sources such as X-ray binaries in their quiescent states.

Analysis of the EMCCD point-source response using x-rays

Electron Multiplying Charge Coupled Devices, EMCCD are used as x-ray detectors. The NSLS-II Soft Inelastic x-ray Scattering (SIX) beam line has two EMCCDs for x-ray detection in the spectrometer arm. The spectrometer with high resolving power disperses x-rays vertically. The x-ray vertical position on the sensor plane is related to its energy. This allows for very accurate x-ray energy measurements through x-ray coordinates. X-rays interact with silicon and create a number of electron–hole pairs proportional to the x-ray energy. Electrons drift and diffuse toward pixel gates and are collected there. The diffused electrons form a charge cloud distributed over several neighboring pixels. This charge sharing enables coordinate measurements with accuracy better than the pixel pitch. The charge distribution shape has to be taken into account to achieve ultimate accuracy in coordinate measurements. In this paper, we present a method of the charge distribution shape analysis and demonstrate its applications.The drift and diffusion of electrons from the point of generation to pixel gates results in the bell-shaped electron cloud usually approximated by Gaussian shape. The number of electrons collected under a pixel is proportional to the shape function integral. These electron packets get transferred to the sense node of the output amplifier. The transfer process could introduce distortions to the original charge distribution. For example, during transfers, electrons in the packet could be exposed to traps if they are present in the sensor. The trapping and later the release processes distort the apparent shape of the charge distribution. Therefore, deviations of the charge distribution shape from the originally symmetrical form can indicate the presence of trap centers in the sensor and can be used for sensor diagnostics.

Cherenkov Luminescence Imaging for Assessment of Radioactive Plaque Position in Brachytherapy of Uveal Melanoma: An In Vivo Feasibility Study.

PurposeTo study the feasibility of using Cherenkov luminescence imaging (CLI) to evaluate and document ruthenium-106 plaque position during brachytherapy of uveal melanoma.MethodsRuthenium-106 decays by emitting high-energy beta particles. When the electrons pass through the eye, Cherenkov radiation generates a faint light that can be captured by highly sensitive cameras. Patients undergoing ruthenium-106 plaque brachytherapy for posteriorly located choroidal melanoma were examined by CLI, which was performed in complete darkness with an electron multiplying charged-coupled device camera mounted on a fundus camera modified for long exposures.ResultsTen patients with tumors ranging from 5.8 to 13.0 mm in largest basal diameter and 2.0 to 4.6 mm in height were included. The plaques had an activity between 0.035 and 0.089 MBq/mm2 at the time of examination (1–4 days after implantation). CLI revealed the actual plaque position by displaying a circular area of light in the fundus corresponding with the plaque area. The Cherenkov light surrounded the tumor as a halo, which showed some asymmetry when the plaque was slightly displaced. The light intensity correlated positively with plaque activity and negatively with tumor pigmentation. Exposure times between 30 and 60 seconds were required to display the plaque position and delineate the tumor area. The long exposures made it difficult to maintain stable eye fixation and optimal image quality.ConclusionsCLI is a novel method to assess and document ruthenium-106 plaque position in brachytherapy for uveal melanoma.Translational RelevanceOcular CLI may provide relevant radiation data during and after implantation of radioactive plaques, thus improving the accuracy of episcleral brachytherapy.

Abstract B08: High-resolution positron emission microscopy of patient-derived tumor organoids

Abstract Tumor organoids are self-organizing three-dimensional tumor models grown in vitro from patient-derived tumor tissue. They closely recapitulate the structural and functional microenvironment of solid tumors. Rapid translation of biomedical information from preclinical models to patients requires imaging biomarkers that span the full scale of tumor models. However, a key limitation is that, unlike human patients or preclinical mouse models, the tiny organoids are incompatible with the suite of radiologic tools used in oncology clinics. Here, we present 18F-fluorodeoxyglucose positron-emission microscopy (FDG-PEM), a radioluminescence-based technique for imaging glucose metabolism in patient-derived tumor organoids with spatial resolution 100-fold better than that of clinical positron emission tomography (PET). Tumor organoids derived from head-and-neck cancer patients were imaged to reveal metabolic maps that, in combination with brightfield imaging, functionally mirror the PET/CT images from the clinic. Tumor organoids were fed with FDG and mounted on a thin CdWO4 scintillator plate. Scintillator flashes were directly imaged by a single-photon-sensitivity electron-multiplying charge-coupled devices (EMCCD) camera. The EMCCD signal was calibrated with known radioactivity of FDG for accurate quantification of PEM images. Dual-modality PEM/fluorescence imaging found that FDG uptake occurred mainly in the viable region of tumor organoids and was more specific than staining by 2-NBDG, a fluorescent glucose mimetic. The influx rate constant (Ki) of FDG into the tumor organoids was calculated and found to be similar to the patient tumor from which the organoids were grown. This positive correlation of FDG influx between patient and organoid tumor suggests that PEM can be a preclinical tool to bridge the gap between laboratory and clinical cancer imaging. Finally, organoids treated with cisplatin displayed a dose-dependent decrease in the metabolic activity, while organoids derived from cisplatin-resistant patients retained high metabolic activity despite cisplatin treatment. Our results suggest that PEM imaging of patient-derived organoids could be used to predict individual patient response to different treatments to provide a more personalized approach to cancer care. Citation Format: Syamantak Khan, June Ho Shin, Ning Cheng, Calvin Kuo, John Sunwoo, Guillem Pratx. High-resolution positron emission microscopy of patient-derived tumor organoids [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr B08.

Photon-counting 3D integral imaging with less than a single photon per pixel on average using a statistical model of the EM-CCD camera

We investigate photon-counting 3D integral imaging (PCII) with an electron multiplying charged-coupled device (EM-CCD) camera using dedicated statistical models. Using conventional integral imaging reconstruction methods with this camera in photon-counting conditions may result in degraded reconstructed image quality if multiple photons are detected simultaneously in a given pixel. We propose an estimation method derived from the photon detection statistical model of the EM-CCD to address the problems caused by multiple photons detected at the same pixel and provide improved 3D reconstructions. We also present a simplified version of this statistical method that can be used under the correct conditions. The imaging performance of these methods is evaluated on experimental data by the peak signal-to-noise ratio and the structural similarity index measure. The experiments demonstrate that 3D integral imaging substantially outperforms 2D imaging in degraded conditions. Furthermore, we achieve imaging in photon-counting conditions where, on average, less than a single photon per pixel is detected by the camera. To the best of our knowledge, this is the first report of PCII with the EM-CCD camera employing its statistical model in 3D reconstruction of PCII.

Transcription Factors and DNA Play Hide and Seek.

Transcription factors (TFs) bind to specific DNA motifs to regulate the expression of target genes. To reach their binding sites, TFs diffuse in 3D and perform local motions such as 1D sliding, hopping, or intersegmental transfer. TF-DNA interactions depend on multiple parameters, such as the chromatin environment, TF partitioning into distinct subcellular regions, and cooperativity with other DNA-binding proteins. In this review, how current understanding of the search process has initially been shaped by prokaryotic studies is discussed, as well as what is known about the parameters regulating TF search efficiency in the context of the complex eukaryotic chromatin landscape.

Single grain infrared photoluminescence (IRPL) measurements of feldspars for dating

Existing infrared photoluminescence (IRPL) systems have used pulsed infrared stimulation (~830 nm) and measured IRPL emission (at 880 or 955 nm) using time resolved data collection with photomultipliers. Breakthrough of the infrared stimulation light overwhelms the IRPL, but the delayed emission during the laser-off period has been used instead.This paper describes a system for measurement of the IRPL signal from single sand-sized grains of feldspar. The attachment uses an electron-multiplying charge-coupled device (EMCCD) imaging system, and has two innovations that make it possible to use such a detector to obtain IRPL data. First, the optical detection system has been designed to minimise stray light and maximise the efficiency with which filters reject the stimulation light. This acts to reduce, but not eliminate, the breakthrough. Second, by placing the sample to be measured in a clearly defined sample grid, the spatial resolution provided by the EMCCD has been used to differentiate between regions of the image where IRPL is emitted and adjacent regions where only breakthrough is expected. This allows quantification of the breakthrough and effective subtraction to isolate the IRPL signal from the grains of interest.The attachment has been used to measure IRPL from single sand-sized grains of feldspar from an aeolian dune from New Zealand. A 1W UV LED (365 nm) is also added to the system and this is effective at resetting the IRPL signal, permitting a single aliquot regenerative dose (SAR) protocol to be used to measure equivalent dose (De). Measurement of a known laboratory dose (104 Gy) demonstrates the reproducibility of the attachment, with no overdispersion observed in the resulting single grain De values. The recovered dose is within 10% of the given dose. The natural IRPL signal yields De values from single grains with low overdispersion (22%) and giving a weighted mean value (103 ± 5.8 Gy) that is consistent with that obtained using post-IR IRSL measurements (105 ± 3.8 Gy). The attachment described here provides IRPL measurements on single grains suitable for exploring the potential of this novel and exciting signal for dating geological sediments.

Quantum yield estimation for an electron-multiplying charge-coupled device from photon counting test data

Electron-multiplying charge-coupled devices (EMCCDs) allow for subelectron effective read noise and thus for imaging at extremely low flux levels. In the ultraviolet, quantum yield creates an additional source of stochastic gain variation, which can be difficult to quantify using existing techniques. We propose a method for measuring the quantum yield gain of these devices, independent of existing methods, using images that are part of the existing test regimen for new EMCCDs. With this method, we were able to recover the quantum yield used to create simulated images within an accuracy of ∼5 % and the method provided consistent results with test images after only minor modifications. However, the measured quantum yield remains anomalously low, consistent with other measurements on Teledyne-e2v devices. We hypothesize that this discrepancy is due to lateral transfer of secondary electrons between pixels at the surface explained by the band structure and crystal geometry of typical silicon wafers used in array detector manufacture.

Small-animal 360-deg fluorescence diffuse optical tomography using structural prior information from ultrasound imaging

.We demonstrate dual modality of free-space fluorescence diffuse optical tomography (FDOT) and handheld ultrasound (US) imaging to reveal both functional and structural information in small animals. FDOT is a noninvasive method for examining the fluorophore inside an object from the light distribution of the surface. In FDOT, a 660-nm continuous wave diode laser was used as an excitation source and an electron-multiplying charge-coupled device (EMCCD) was used for fluorescence data acquisition. Both the laser and EMCCD were mounted on a 360-deg rotation gantry for the transmission optical data collection. The structural information is obtained from a 6- to 17-MHz handheld US linear transducer by single-side access and conducts in the reconstruction as soft priors. The rotation ranges from 0 deg to 360 deg; different rotation degrees, object positions, and parameters were determined for comparison. Both phantom and tissue phantom results demonstrate that fluorophore distribution can be recovered accurately and quantitatively using this imaging system. Finally, an animal study confirms that the system can extract a dual-modality image, validating its feasibility for further in vivo experiments. In all experiments, the error and standard deviation decrease as the rotation degree is increased and the error was reduced to 10% when the rotation degree was increased over 135 deg.

Improving sensitivity and imaging depth of ultrasound-switchable fluorescence via an EMCCD-gain-controlled system and a liposome-based contrast agent.

The ultrasound-switchable fluorescence (USF) technique was recently developed to achieve high-resolution fluorescence imaging in centimeters-deep tissue. This study introduced strategies to significantly improve imaging sensitivity and depth using an electron multiplying charge-coupled device (EMCCD) camera-based USF imaging system and a newly developed USF contrast agent of indocyanine green (ICG)-encapsulated liposomes. For a quantitative study, a phantom of a sub-millimeter silicone tube embedded in centimeter-thick chicken breast tissue was adopted in this study as a model. The synthesized ICG-liposome was characterized and compared with the previously reported ICG-nanogel. The exposure of the EMCCD camera was controlled via the MATLAB (The MathWorks, Inc. USA), instead of an external hardware trigger. The stability of the electron multiplying (EM) gain of the EMCCD camera was compared between two trigger modes: the MATLAB trigger mode and the external hardware trigger mode. The signal-to-noise ratio (SNR) of the USF imaging with different EM gain in various thick tissue was studied. The hydrodynamic size of the ICG-liposome was ~181 nm. The ICG-liposome had a sharper temperature switching curve and a better USF performance than the previously reported ICG-nanogel. The EM gain was more stable in MATLAB trigger mode than the external hardware trigger mode. Although, as usual, the SNR decreased quickly with the increase of the tissue thickness, the proposed strategies improved the SNR and the imaging depth significantly by adopting the novel contrast agent and controlling the EM gain. We successfully imaged the sub-millimeter silicone tube with an inner diameter of 0.76 mm and an outer diameter of 1.65 mm in 5.5 cm-thick chicken breast tissue using 808 nm excitation light with a low intensity of 28.35 mW/cm2, the improved EMCCD camera-based USF imaging system and the novel ICG-liposomes.

A new method for measuring the meteor mass index: application to the 2018 Draconid meteor shower outburst

Context.Several authors predicted an outburst of the Draconid meteor shower in 2018, but with an uncertain level of activity.Aims.Optical meteor observations were used to derive the population and mass indices, flux, and radiant positions of Draconid meteors.Methods.We performed 90 min of multi-station observations after the predicted peak of activity using highly sensitive Electron Multiplying Charge Coupled Device cameras. The data calibration is discussed in detail. A novel maximum likelihood estimation method was developed to compute the population and mass index with robust error estimation. We applied the method to observed Draconids and used the values to derive the flux. Meteor trajectories were computed and compared to predicted radiant positions from meteoroid ejection models.Results.We find a mass index of 1.74 ± 0.18 in the 30 min bin after the predicted peak, and 2.32 ± 0.27 in the subsequent 60 min. The location and the dispersion of the radiant are a good match to modeled values, but there is an offset of 0.4° in solar longitude.

ARIADNE—A novel optical LArTPC: technical design report and initial characterisation using a secondary beam from the CERN PS and cosmic muons

ARIADNE is a 1-ton (330 kg fiducial mass) dual-phase liquid argon (LAr) time projection chamber (TPC) featuring a novel optical readout. Four electron-multiplying charge-coupled device (EMCCD) cameras are mounted externally, and these capture the secondary scintillation light produced in the holes of a thick electron gas multiplier (THGEM) . Track reconstruction using this novel readout approach is demonstrated. Optical readout has the potential to be a cost effective alternative to charge readout in future LArTPCs. In this paper, the technical design of the detector is detailed. Results of mixed particle detection using a secondary beam from the CERN PS (representing the first ever optical images of argon interactions in a dual-phase LArTPC at a beamline) and cosmic muon detection at the University of Liverpool are also presented.

Measuring system for testing electrical parameters of EMCCDs of various formats

This article describes the developed equipment that allows measuring the photoelectrical parameters of multielement photodetectors, specifically various formats of EMCCD (electron multiplying charge-coupled device) chips. The authors present the measuring techniques and test results on dark currents, output amplifier sensitivity, charge transfer efficiency, charge capacity and other parameters. The studies were conducted, both on the wafer and in the body, on samples of the following formats: 576×288, 640×512, 768×576, 1024×1024, and 1280×1024.