Electronic Noise Research Articles

Dual-Source Photon-Counting Computed Tomography-Part I: Clinical Overview of Cardiac CT and Coronary CT Angiography Applications.

The photon-counting detector (PCD) is a new computed tomography detector technology (photon-counting computed tomography, PCCT) that provides substantial benefits for cardiac and coronary artery imaging. Compared with conventional CT, PCCT has multi-energy capability, increased spatial resolution and soft tissue contrast with near-null electronic noise, reduced radiation exposure, and optimization of the use of contrast agents. This new technology promises to overcome several limitations of traditional cardiac and coronary CT angiography (CCT/CCTA) including reduction in blooming artifacts in heavy calcified coronary plaques or beam-hardening artifacts in patients with coronary stents, and a more precise assessment of the degree of stenosis and plaque characteristic thanks to its better spatial resolution. Another potential application of PCCT is the use of a double-contrast agent to characterize myocardial tissue. In this current overview of the existing PCCT literature, we describe the strengths, limitations, recent applications, and promising developments of employing PCCT technology in CCT.

Low-frequency noise in β-(AlxGa1−x)2O3 Schottky barrier diodes

We report on the low-frequency electronic noise in β-(AlxGa1−x)2O3 Schottky barrier diodes. The noise spectral density reveals 1/f dependence, characteristic of the flicker noise, with superimposed Lorentzian bulges at the intermediate current levels (f is the frequency). The normalized noise spectral density in such diodes was determined to be on the order of 10−12 cm2/Hz (f = 10 Hz) at 1 A/cm2 current density. At the intermediate current regime, we observed the random telegraph signal noise, correlated with the appearance of Lorentzian bulges in the noise spectrum. The random telegraph signal noise was attributed to the defects near the Schottky barrier. The defects can affect the local electric field and the potential barrier and, correspondingly, impact the electric current. The obtained results help in understanding the noise in Schottky barrier diodes made of ultra-wide bandgap semiconductors and can be used for the material and device quality assessment.

New Inogranic Scintillators’ Application in the Electromagnetic Calorimetry in High-Energy Physics

Scintillation crystals Gd3Al2Ga3O12 (GAGG) are an excellent candidate for application in ionizing-radiation detectors because of their high radiation resistance, density and light yield. These crystals can be used in combination with lead tungstate (PbWO4 or PWO) crystals for the development of a new generation of electromagnetic calorimeter with advanced spatial and energy resolutions in a broad energy range. PWO crystals enable the accurate detection of high-energy photons, while GAGG crystals provide the possibility of precisely measuring photon energies, down to a few MeV. Different options for a composite electromagnetic calorimeter based on PWO and GAGG crystals are considered to optimize spatial and energy resolutions in a broad energy range (from 1 MeV to 100 GeV). In particular, different lengths of the GAGG section of the calorimeter are considered, from 0.5 to 10 cm. The separation of signals from photons and hadrons is also taken into consideration through the study of shower shape in the calorimeter. The optimization is based on Geant4 simulations, considering light collection as well as the use of different photodetectors and electronic noise. Simulations are verified with light yield measurements of GAGG samples obtained using radioactive sources and test beam measurements of the prototype of the PWO-based Photon Spectrometer of the ALICE experiment at CERN.

Representing noise: stacked plots and the contrasting diplomatic ambitions of radio astronomy and post-punk.

Sketched in 1979 by graphic designer Peter Saville, the record sleeve of Joy Division's Unknown Pleasures seemingly popularized one of the most celebrated radio-astronomical images: the 'stacked plot' of radio signals from a pulsar. However, the sleeve's designer did not have this promotion in mind. Instead, he deliberately muddled the message it originally conveyed in a typical post-punk act of artistic sabotage. In reconstructing the historical events associated with this subversive effort, this essay explores how, after its adoption as an imaging device utilized in radio astronomy, the stacked plot gave representation to the diplomacy agendas of two distinct groups. The post-punk reworking of the stacked plot exemplified the ambition of this artistic movement to attack the images associated with social conventions and norms by amplifying their 'semantic noise', and, in so doing, seeking to negotiate a social space for those sharing these subversive goals. Conversely, radio astronomers used the stacked plot to display the presence of interfering radio transmitters in the frequencies exclusively allocated to astronomical research, thus advocating the removal of this electronic noise in the context of international telecommunication negotiations. The article thus shows how the representation of different types of noise through similar images shaped contrasting ambitions in the separate domains of science diplomacy and everyday diplomacy.

TDCpix pixel detector ASIC with 100 ps time stamping

The TDCpix pixel read-out ASIC contains 1800 pixels arranged in 40 columns and 45 rows with the dimension of 300μm x 300μm. Each pixel contains a preamplifier and shaper circuit with a dynamic range of 0.8 to 10 fC and a rise time of 5 ns, followed by a Leading-Edge discriminator with Time-over-Threshold correction. The discriminator outputs of each pixel are connected to time-to-digital converters (TDC) measuring the time when the input signal has exceeded the threshold and the pulse width with a binning of 97 ps. The electronics noise of pre-amplifier/shaper is 170 e− or 2.7 mV rms with a gain of 65 mV/fC. The jitter of the entire processing chain for an electrical input signal of 2.4 fC is lower than 60 ps rms. The ASIC has been designed to work in radiated environments of 6 * 104 Gray per year and 2 x 1014 1 MeV neutron equivalent cm−2.

Multicharacteristics Arc Model and Autocorrelation-Algorithm Based Arc Fault Detector for DC Microgrid

DC microgrids contribute to the increasing penetration of renewable energies. However, a DC arc fault will lead to malfunctions and even fire hazards in a DC microgrid. To ensure the safe and efficient operation of a DC microgrid, the characteristics of DC arc faults should be determined, and a reliable arc-fault detection technique is required. Nevertheless, it is difficult to investigate the DC arc faults in a practical system. Thus, an accurate and reliable arc model for simulation research of arc faults is significant. Since a DC microgrid has numerous branches, the existing arc models cannot express the complex and random characteristics of potential arc faults. Besides, the detection points need to be determined for the appropriate installation of arc fault detectors. Furthermore, the arc features may be ambiguous and affected by the environmental noise and power electronics noise leading to nuisance tripping to arc detectors. In this paper, a multi-characteristics arc model is established based on the volt-ampere, current sag, and power spectral characteristics of arc faults. According to the frequency domain features of arc faults and interaction effects between different branches, the arc-detection-point selection principle is formed. A non-invasive arc fault detector based on magnetic-field sensing and autocorrelation algorithm is developed. It can avoid the effects of periodic environmental noise and power electronics noise by comparing the correlation between arc features in periods. The experimental results verify that the arc faults can be detected with high accuracy by installing the autocorrelation-algorithm-based arc detector at detection points selected by the arc-detection-point selection principle in a DC microgrid.

Wavelet Transform Technique Applied to Satellite Image Denoising

Satellite images either digital or analog must have certain elements that are accidentally introduced during the processing of capturing as a result of weather or system sensor known as electronic noise. However, several attempts and advances have been made by academicians, industries and intelligent security agencies to remove this noise. It has been a nagging problem in the area of computer vision, image processing and artificial intelligence to denoise satellite images and noise removal is among the significant components in satellite image analysis. The aim of this research work was to denoise the satellite image of Sambisa forest using the wavelet transform technique. Satellite images of Sambisa forest captured by Landsat satellite in 2007, 2013, 2014, 2019 and 2021 respectively with their associated Geo-referenced 11.2503° N Longitude and 13.4167° E Latitude were downloaded from the United States Geological Survey (USGS) website. The images are acquired as Zipped Geo-referenced Tagged Image File Format (GeoTIFF). Color Composite bands of natural colors (bands 2, 3 and 4) are combined using the ArcGIS software and RGB image were obtained. Wavelet transforms denoising technique was used to filter noise from the images, which was implemented using the wdenoise2() function in MATLAB 2021.

Regularization techniques for 3D surface reconstruction from four quadrant backscattered electron detector images

In scanning electron microscopy (SEM), a four quadrants backscattered electron detector (FQBSD) provides signals that can be combined to obtain a tridimensional reconstruction of the surface. The main challenge of the reconstruction operation consists of integrating the gradient field obtained as the normalized signal difference from each pair of opposite quadrants. Owing to the presence of electronic noise that eventually turns into image noise, a least square integration approach has been widely adopted for surface reconstruction. In the present work, we demonstrate the possibility of adopting regularization techniques (Tichonov’s and Dirichlet’s) to the surface reconstruction from FQBSD images to reduce the distortions due to sensitivity variations amongst the detector quadrants or an imprecise alignment of the FQBSD with the gun axis. This allows for a substantial improvement in the 3D surface reconstruction quality in terms of resolution and reduction of artifacts. These procedures have been experimentally validated on AISI 316L stainless steel polished surfaces with hardness indentation and on laser-patterned aluminum and silicon samples showing promising results.

Analysis of interstrip capacitance of p+n MCz Si microstrip detector using TCAD simulation combining surface and bulk damage effects by mixed irradiation

Interstrip capacitance plays a crucial role on the detector electronic noise performance at the readout electrode of the irradiated detectors in the harsh radiation environment of the high luminosity Large Hadron Collider experiments. The major challenge is to optimize the design of the detector to get the low interstrip capacitance in the real ‘mixed’ irradiation environment of the experiment. A few of experimental studies have been performed within CERN RDD0 collaboration on the n-MCz Si detectors to extract the microscopic parameters for the surface and bulk damage effects especially by mixed irradiations in the detectors. The results on the microscopic parameters are fed into ATLAS TCAD commercial simulation program to compare the experimental data and simulation result. A very good agreement has been recorded between the data and simulation result. In this paper, the microscopic model parameters are used to investigate the effects of mixed irradiation up to a fluence of 8.82× 1014 neq./cm2 on the interstrip capacitance in n-MCz 〈100〉 silicon microstrip detectors. The results are discussed in detail using electric field distribution, electron concentration profile in the irradiated detectors for the different metal overhang width, and an optimized p+n-MCz Si microstrip design is proposed for the future collider experiment.

Breathable MOFs Layer on Atomically Grown 2D SnS2 for Stable and Selective Surface Activation.

2D transition metal dichalcogenides (TMDs) have significant research interests in various novel applications due to their intriguing physicochemical properties. Notably, one of the 2D TMDs, SnS2 , has superior chemiresistive sensing properties, including a planar crystal structure, a large surface-to-volume ratio, and a low electronic noise. However, the long-term stability of SnS2 in humid conditions remains a critical shortcoming towards a significant degradation of sensitivity. Herein, it is demonstrated that the subsequent self-assembly of zeolite imidazolate framework (ZIF-8) can be achieved in situ growing on SnS2 nanoflakes as the homogeneous porous materials. ZIF-8 layer on SnS2 allows the selective diffusion of target gas species, while effectively preventing the SnS2 from severe oxidative degradation. Molecular modeling such as molecular dynamic simulation and DFT calculation, further supports the mechanism of sensing stability and selectivity. From the results, the in situ grown ZIF-8 porous membrane on 2D materials corroborates the generalizable strategy for durable and reliable high-performance electronic applications of 2D materials.

Theoretical comparison and optimization of cadmium telluride and gallium arsenide photon-counting detectors for contrast-enhanced spectral mammography.

Most photon-counting detectors (PCDs) being developed use cadmium telluride (CdTe), which has nonoptimal characteristic x-ray emission with energies in the range used for breast imaging. New PCD using a gallium arsenide (GaAs) has been developed. Since GaAs has characteristic x-rays lower in energy than those of CdTe, it is hypothesized that this new PCD might be beneficial for spectral x-ray breast imaging. We performed simulations using realistic mammography x-ray spectra with both CdTe and GaAs PCDs. Five different experiments were conducted, each comparing the performance of CdTe and GaAs: (1) sensitivity of iodine quantification to charge cloud size and electronic noise, (2) effect of photon spectrum on iodine quantification, (3) effect of varying the number of energy bins, (4) a dose analysis to assess any possible dose reduction from using either detector, and (5) spectral performance of ideal CdTe and GaAs PCDs. For each study, 3 sets of 5000 noise realizations were used to calculate the Cramer-Rao lower bound (CRLB) of iodine quantification. For all spectra studied, GaAs gave a lower CRLB for iodine quantification, with 10 of the 12 spectra showing a statistically significant difference ( ). The photon energy spectrum that optimized iodine detection for both detector materials was the 40 kVp beam with 2-mm Al filtration, which produced CRLBs of and for CdTe and GaAs, respectively, when using five energy bins. GaAs is a promising detector material for contrast-enhanced spectral mammography that offers better spectral performance than CdTe.

High-field 1/f noise in hBN-encapsulated graphene transistors

$1/f$ electronic noise is a conductance fluctuation, expressed in terms of a mobility ``$\ensuremath{\alpha}$-noise'' by Hooge and Kleinpenning. Understanding this noise in graphene is key for high-performance electronics. Early investigations pointed out a deviation from the standard Hooge formula, with the free-carrier density substituted by a constant density ${n}_{\mathrm{\ensuremath{\Delta}}}\ensuremath{\sim}{10}^{12}\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$. Here we investigate hBN-encapsulated graphene transistors where high mobility gives access to the velocity-saturation regime. We show that $\ensuremath{\alpha}$-noise is still accounted for by the Hooge formula on substituting conductance by differential conductance $G$, resulting in a bell-shaped dependence of flicker noise with bias voltage. The same analysis holds in the Zener regime at even larger bias, with two main differences. The first one is a strong enhancement of the Hooge parameter reflecting the hundred-times larger coupling of interband excitations to the hyperbolic phonon-polariton (HPhP) modes of the midinfrared Reststrahlen (RS) bands of hBN, which is supported by microwave noise thermometry measurements. The second is an exponential suppression of this coupling at large fields, which we attribute to decoherence effects. The phenomenology of $1/f$ noise in graphene supports a quantum-coherent bremsstrahlung interpretation of $\ensuremath{\alpha}$-noise.

Objectively measured infant and toddler screen time: Findings from a prospective study

ObjectiveScreen time guidelines recommend no screens under two years due to the potential negative impacts on development. While current reports suggest many children exceed this, research relies on parent reports of their children's screen exposure. We objectively assess screen exposure during the first two years and how it differs by maternal education and gender. MethodsThis Australian prospective cohort study used speech recognition technology to understand young children's screen exposure over an average day. Data collection occurred every six months when children were 6, 12, 18 and, 24 months old (n = 207). The technology provided automated counts of children's exposure to electronic noise. Audio segments were then coded as screen exposure. Prevalence of screen exposure was quantified, and differences between demographics examined. ResultsAt six months, children were exposed to an average of 1hr, 16 min (SD = 1hr, 36 min) of screens per day, increasing to an average of 2 h, 28 min (SD = 2 h, 4 min) by 24-months. Some children at six months were exposed to more than 3 h of screen time per day. Inequalities in exposure were evident as early as six months. Children from higher educated families were exposed to 1hr,43 min fewer screens per day, 95%CI (-2hr, 13 min, -1hr, 11 min) compared to lower educated households, with this difference remaining consistent as children age. Girls were exposed to an additional 12 min of screens 95%CI (−20 min, 44 min) per day compared to boys at six months, but this difference reduced to only 5 min by 24-months. ConclusionUsing an objective measure of screen exposure, many families exceed screen time guidelines, the extent increasing with child's age. Furthermore, substantial differences between maternal education groups emerge as young as six months old. This highlights the need for education and supports for parents around screen use in the early years, balanced within the realities of modern life.

Clinical applications of photon counting detector CT.

The X-ray detector is a fundamental component of a CT system that determines the image quality and dose efficiency. Until the approval of the first clinical photon-counting-detector (PCD) system in 2021, all clinical CT scanners used scintillating detectors, which do not capture information about individual photons in the two-step detection process. In contrast, PCDs use a one-step process whereby X-ray energy is converted directly into an electrical signal. This preserves information about individual photons such that the numbers of X-ray in different energy ranges can be counted. Primary advantages of PCDs include the absence of electronic noise, improved radiation dose efficiency, increased iodine signal and the ability to use lower doses of iodinated contrast material, and better spatial resolution. PCDs with more than one energy threshold can sort the detected photons into two or more energy bins, making energy-resolved information available for all acquisitions. This allows for material classification or quantitation tasks to be performed in conjunction with high spatial resolution, and in the case of dual-source CT, high pitch, or high temporal resolution acquisitions. Some of the most promising applications of PCD-CT involve imaging of anatomy where exquisite spatial resolution adds clinical value. These include imaging of the inner ear, bones, small blood vessels, heart, and lung. This review describes the clinical benefits observed to date and future directions for this technical advance in CT imaging. KEY POINTS: • Beneficial characteristics of photon-counting detectors include the absence of electronic noise, increased iodine signal-to-noise ratio, improved spatial resolution, and full-time multi-energy imaging. • Promising applications of PCD-CT involve imaging of anatomy where exquisite spatial resolution adds clinical value and applications requiring multi-energy data simultaneous with high spatial and/or temporal resolution. • Future applications of PCD-CT technology may include extremely high spatial resolution tasks, such as the detection of breast micro-calcifications, and quantitative imaging of native tissue types and novel contrast agents.

The technical development of photon-counting detector CT.

Since 1971 and Hounsfield's first CT system, clinical CT systems have used scintillating energy-integrating detectors (EIDs) that use a two-step detection process. First, the X-ray energy is converted into visible light, and second, the visible light is converted to electronic signals. An alternative, one-step, direct X-ray conversion process using energy-resolving, photon-counting detectors (PCDs) has been studied in detail and early clinical benefits reported using investigational PCD-CT systems. Subsequently, the first clinical PCD-CT system was commercially introduced in 2021. Relative to EIDs, PCDs offer better spatial resolution, higher contrast-to-noise ratio, elimination of electronic noise, improved dose efficiency, and routine multi-energy imaging. In this review article, we provide a technical introduction to the use of PCDs for CT imaging and describe their benefits, limitations, and potential technical improvements. We discuss different implementations of PCD-CT ranging from small-animal systems to whole-body clinical scanners and summarize the imaging benefits of PCDs reported using preclinical and clinical systems. KEY POINTS: • Energy-resolving, photon-counting-detector CT is an important advance in CT technology. • Relative to current energy-integrating scintillating detectors, energy-resolving, photon-counting-detector CT offers improved spatial resolution, improved contrast-to-noise ratio, elimination of electronic noise, increased radiation and iodine dose efficiency, and simultaneous multi-energy imaging. • High-spatial-resolution, multi-energy imaging using energy-resolving, photon-counting-detector CT has been used in investigations into new imaging approaches, including multi-contrast imaging.

Timing resolution in double-sided silicon photon-counting computed tomography detectors.

Our purpose is to investigate the timing resolution in edge-on silicon strip detectors for photon-counting spectral computed tomography. Today, the timing for detection of individual x-rays is not measured, but in the future, timing information can be valuable to accurately reconstruct the interactions caused by each primary photon. We assume a pixel size of and a detector with double-sided readout with low-noise CMOS electronics for pulse processing for every pixel on each side. Due to the electrode width in relation to the wafer thickness, the induced current signals are largely dominated by charge movement close to the collecting electrodes. By employing double-sided readout electrodes, at least two signals are generated for each interaction. By comparing the timing of the induced current pulses, the time of the interaction can be determined and used to identify interactions that originate from the same incident photon. Using a Monte Carlo simulation of photon interactions in combination with a charge transport model, we evaluate the performance of estimating the time of the interaction for different interaction positions. Our simulations indicate that a time resolution of 1ns can be achieved with a noise level of 0.5keV. In a detector with no electronic noise, the corresponding time resolution is . Time resolution in edge-on silicon strip CT detectors can potentially be used to increase the signal-to-noise-ratio and energy resolution by helping in identifying Compton scattered photons in the detector.

The Improved X-ray Detector (iXRD) on Sharjah-Sat-1, design principles, tests and ground calibration

The iXRD is the primary science payload on Sharjah-Sat-1, a 3U CubeSat expected to be launched in Q4, 2022. Its main scientific goal is monitoring bright hard X-ray sources and transients in 20 - 200 keV band. The iXRD consists of a CdZnTe crystal (6.45 cm2 area, 5 mm thickness), a Tungsten collimator with square holes with an opening angle of 4.26∘, readout and control electronics and power supply circuitry, a back-shield and mechanical structures. Some of the design elements of iXRD have been inherited from the XRD on BeEagleSat with significant improvements in terms of collecting area, X-ray background and electronic noise. In this article, the design of the iXRD is discussed in detail taking into account mechanical, electronic, control software and data handling aspects. Its expected performance is determined after ground calibration. Depending on the pixel size, the energy resolution is 4 - 7 keV at 60 keV and the minimum detectable energy is 19 - 23 keV.

Low-frequency noise in ZrS3 van der Waals semiconductor nanoribbons

We report the results of the investigation of low-frequency electronic noise in ZrS3 van der Waals semiconductor nanoribbons. The test structures were of the back-gated field-effect-transistor type with a normally off n-channel and an on-to-off ratio of up to four orders of magnitude. The current–voltage transfer characteristics revealed significant hysteresis owing to the presence of deep levels. The noise in ZrS3 nanoribbons had spectral density SI ∼ 1/fγ (f is the frequency) with γ = 1.3–1.4 within the whole range of the drain and gate bias voltages. We used light illumination to establish that the noise is due to generation–recombination, owing to the presence of deep levels, and determined the energies of the defects that act as the carrier trapping centers in ZrS3 nanoribbons.

Sensitivity Enhancement and Random Telegraph Noise in Magnetic Tunnel Junctions with Compensated Anisotropy

We demonstrate the manipulation of perpendicular magnetic anisotropy (PMA) in magnetic tunnel junctions (MTJs) by varying the layer stacks and temperature. PMA is tuned to compensate the shape anisotropy, giving a nonhysteretic magnetic response, a noteworthy sensitivity enhancement, and a field detectability of $1.8\phantom{\rule{0.25em}{0ex}}\mathrm{nT}/\sqrt{\mathrm{Hz}}$ at 100 kHz. Such a method is further exemplified in multiple MTJs, providing a solution to obtain desired sensitivities and operating temperatures. Additionally, the electronic noise of this MTJ is revealed as a random telegraph noise (RTN) due to a generation-recombination process. The observed voltage-dependent RTN could potentially be applied to true random number generators.

High event rate analysis technique for the dual-axis duo-lateral position-sensitive silicon detectors of FAUST

The dual-axis duo-lateral (DADL) position-sensitive silicon detector was developed to obtain precise position and energy information for detected charged particles. The Forward Array Using Silicon Technology (FAUST) is currently equipped with 68 DADL detectors backed by CsI(Tl) scintillators for the study of charged particle correlations in heavy-ion collisions where precise position and energy information is essential. When conventional signal processing electronics were used for the DADL detectors, a position dependence of the measured energy as well as distortions in the calculated particle positions were observed. In previous work, waveforms from the detector after preamplification were studied to better understand the features that give rise to these distortions; therein, a waveform analysis technique was developed to improve the energy resolution and linearity in position reconstruction. However, the reading and writing of waveforms for an entire detector array limits data collection rates and adds significant burden in data storage and analysis speed. In this work, the integrators of a Struck SIS3316 ADC were utilized to process 228Th source data to develop and optimize a new analysis method that captures the benefits of the waveform analysis technique while circumventing the waveform writing requirement. This integrator method – capable of 59keV (FWHM) energy resolution – was used in the collection of 35 MeV/nucleon 28Si + 12C collision data using FAUST to investigate exotic decays of highly excited highly deformed nuclei. In this data, a position resolution of 0.4mm (FWHM) was obtained for 25MeV α-particles; for α-particles near this energy that originate from 8Be ground state decays, a 8Be ground state width of 30keV (FWHM) was obtained. The impact of the energy-dependent DADL position resolution emergent from electronic noise on the quality of excited state measurement was modeled and compared to the experimental data.