Hybrid Detector Research Articles

Conceptual design of TUPI (Timepix4-based Ultra-fast Photon Imaging) detector's hardware

TUPI (Timepix4-based Ultra-fast Photon Imaging) is the new family of direct conversion and vacuum-compatible hybrid detectors under design at Sirius, the Brazilian 4th generation light source. Based on the Timepix4 Application Specific Integrated Circuit (ASIC), it targets different kinds of experiments, such as tomography and spectrometry, and will be used in multiple bioimaging beamlines of Orion, Brazil's Biosafety Level 4 (BSL4) Laboratory project. Also, it will cover a wide energy range (5 to 45 keV) by using different sensors materials (Si, GaAs, CdTe, etc.). Designed in a modular approach to ensure scalability for constructing larger active areas in a compact form, each TUPI module will be composed by a set of 3x side-by-side Timepix4 ASICs to provide a sensitive area of approximately 74×28 mm2 (1344×512 pixels of 55 μm pitch), streaming up to 44 kfps through up to 48×10.24 Gbps optical links directly connected to a Data Acquisition (DAQ) system.

A Hybrid Deep Learning Framework for OFDM with Index Modulation Under Uncertain Channel Conditions

Index modulation (IM) is considered a promising approach for fifth-generation wireless systems due to its spectral efficiency and reduced complexity compared to conventional modulation techniques. However, IM faces difficulties in environments with unpredictable channel conditions, particularly in accurately detecting index values and dynamically adjusting index assignments. Deep learning (DL) offers a potential solution by improving detection performance and resilience through the learning of intricate patterns in varying channel conditions. In this paper, we introduce a robust detection method based on a hybrid DL (HDL) model designed specifically for orthogonal frequency-division multiplexing with IM (OFDM-IM) in challenging channel environments. Our proposed HDL detector leverages a one-dimensional convolutional neural network (1D-CNN) for feature extraction, followed by a bidirectional long short-term memory (Bi-LSTM) network to capture temporal dependencies. Before feeding data into the network, the channel matrix and received signals are preprocessed using domain-specific knowledge. We evaluate the bit error rate (BER) performance of the proposed model using different optimizers and equalizers, then compare it with other models. Moreover, we evaluate the throughput and spectral efficiency across varying SNR levels. Simulation results demonstrate that the proposed hybrid detector surpasses traditional and other DL-based detectors in terms of performance, underscoring its effectiveness for OFDM-IM under uncertain channel conditions.

Design and characterization of a hybrid PET detector with DOI capability.

Monolithic or semi-monolithic detectors are attractive for positron emission tomography (PET) scanners with depth-of-interaction (DOI) capability. However, they often require complicated calibrations to determine the interaction positions of gamma photons. We introduce a novel hybrid detector design that combines pixelated and semi-monolithic elements to achieve DOI capability while simplifying the calibrations for positioning. A prototype detector with eight hybrid lutetium-yttrium oxyorthosilicate (LYSO)layers having dimensions of 25.8×12.9×15mm3 was constructed. The energy-weighted and energy-squared weighted averages were used for estimating the x- (pixelated direction) and y-positions (non-pixelated direction). Pseudo-pixels were defined as discrete areas on the flood image based on the crystal look-up table (LUT). The intrinsic spatial resolutions in the pixelated and non-pixelated directions were measured. The ratio of the maximum to the sum of the multipixel photon counter (MPPC) signals was used to estimate the DOI positions. The coincidence timing resolution (CTR) was measured using the average and energy-weighted average of the earliest n time stamps. Two energy windows of 250-700 and 400-600keV were applied for the measurements. The pattern of the flood images showed discrete event clusters, demonstrating that simple calibrations for determining the x- and y-positions of events could be achieved. Under 400-600keV energy window, the average intrinsic spatial resolutions were 1.15 and 1.34mm for the pixelated and non-pixelated directions; the average DOI resolution of the second row of pseudo-pixels was 5.1mm in full width at half maximum (FWHM); when using the energy-weighted average of the earliest four-time stamps, the best CTR of 350ps was achieved. Applying a broader energy window of 250-700keV only slightly degrades the DOI resolution while maintaining the intrinsic resolution; the best CTR degrades to 410ps. The proposed hybrid detector concept was verified, and a prototype detector showed high performance for 3D positioning and timing resolution. The novel detector concept shows promise for preclinical and clinical PET scanners with DOI capability.

A Hybrid Approach for Image Acquisition Methods Based on Feature-Based Image Registration.

This paper presents a novel hybrid approach to feature detection designed specifically for enhancing Feature-Based Image Registration (FBIR). Through an extensive evaluation involving state-of-the-art feature detectors such as BRISK, FAST, ORB, Harris, MinEigen, and MSER, the proposed hybrid detector demonstrates superior performance in terms of keypoint detection accuracy and computational efficiency. Three image acquisition methods (i.e., rotation, scene-to-model, and scaling transformations) are considered in the comparison. Applied across a diverse set of remote-sensing images, the proposed hybrid approach has shown marked improvements in match points and match rates, proving its effectiveness in handling varied and complex imaging conditions typical in satellite and aerial imagery. The experimental results have consistently indicated that the hybrid detector outperforms conventional methods, establishing it as a valuable tool for advanced image registration tasks.

BiF-DETR:Remote sensing object detection based on Bidirectional information fusion

Remote Sensing Object Detection(RSOD) is a fundamental task in the field of remote sensing image processing. The complexity of the background, the diversity of object scales and the locality limitation of Convolutional Neural Network (CNN) present specific challenges for RSOD. In this paper, an innovative hybrid detector, Bidirectional Information Fusion DEtection TRansformer (BiF-DETR), is proposed to mitigate the above issues. Specifically, BiF-DETR takes anchor-free detection network, CenterNet, as the baseline, designs the feature extraction backbone in parallel, extracts the local feature details using CNNs, and obtains the global information and long-term dependencies using Transformer branch. A Bidirectional Information Fusion (BIF) module is elaborately designed to reduce the semantic differences between different styles of feature maps through multi-level iterative information interactions, fully utilizing the complementary advantages of different detectors. Additionally, Coordination Attention(CA), is introduced to enables the detection network to focus on the saliency information of small objects. To address diversity insufficiency of remote sensing images in the training stage, Cascade Mixture Data Augmentation (CMDA), is designed to improve the robustness and generalization ability of the model. Comparative experiments with other cutting-edge methods are conducted on the publicly available DOTA and NWPU VHR-10 datasets. The experimental results reveal that the performance of proposed method is state-of-the-art, with mAP reaching 77.43% and 94.75%, respectively, far exceeding the other 25 competitive methods.

Design, fabrication and testing of Al/p-Si Schottky and pn junctions for radiation studies

Strip and pixels sensors, fabricated on high resistivity silicon substrate, normally of p-type, are used in detectors for High Energy Physics (HEP) typically in a hybrid detector assembly. Furthermore, and owing to their inherent advantages over hybrid sensors, Monolithic Active Pixel Sensors (MAPS) fabricated in CMOS technology have been increasingly implemented in HEP experiments. In all cases, their use in higher radiation areas (HL-LHC and beyond) will require options to improve their radiation hardness and time resolution. These aspects demand a deep understanding of their radiation damage and reliable models to predict their behaviours at high fluences. As a first step, we fabricated several Schottky and n-on-p diodes, to allow a comparison of results and provide a backup solution for test devices, on 6 or 4-inch p-type silicon wafers with 50 μm epitaxial thickness and of doping concentration as they are normally used in HEP detectors and CMOS MAPS devices. In this paper, details of the design and fabrication process, along with test results of the fabricated devices before irradiation, will be provided. Additional test results on irradiated devices will be provided in subsequent publications.

Cosmic-ray physics at the South Pole

The geographic South Pole provides unique opportunities to study cosmic particles in the Southern Hemisphere. It represents an optimal location to deploy large-scale neutrino telescopes in the deep Antarctic ice, such as AMANDA or IceCube. In both cases, the presence of an array, constructed to observe extensive air showers, enables hybrid measurements of cosmic rays. While additional neutron monitors can provide information on solar cosmic rays, large detector arrays, like SPASE or IceTop, allow for precise measurements of cosmic rays with energies above several 100TeV. In coincidence with the signals recorded in the deep ice, which are mostly due to the high-energy muons produced in air showers, this hybrid detector setup provides important information about the nature of cosmic rays.In this review, we will discuss the historical motivation and developments towards measurements of cosmic rays at the geographic South Pole and highlight recent results reported by the IceCube Collaboration. We will emphasize the important contributions by Thomas K. Gaisser and his colleagues that ultimately led to the rich Antarctic research program which today provides crucial insights into cosmic-ray physics.

Optimal hybrid layout of point and open‐path gas detectors in process facilities of natural gas stations

AbstractBecause open‐path gas detectors offer superior technical performance, leakage monitoring systems tend to use a hybrid layout of point and open‐path gas detectors. However, most research on the optimized layout of leakage monitoring has focused only on point gas detectors. In this paper, an optimization model for a hybrid layout of point and open‐path gas detectors was proposed considering the cost–benefit ratio and detection time. As the measured value of an open‐path gas detector is an integral concentration, a monitor line in the simulation was calculated via the approximate rectangle method. The results showed that the use of a multiobjective gas detector layout considering the cost–benefit ratio and an improved non‐dominated sorting genetic algorithm (NSGA‐II) could optimize the layout of hybrid detectors. The hybrid layout was analyzed in a case study of process facilities at a natural gas station. As the number of detectors increased (safety investment), the proportion of open‐path gas detectors increased, improving both leakage monitoring performance and the cost–benefit ratio. Additionally, the layout of the point gas detectors was analyzed. A comparison of objective function values for detection time showed the superiority of the hybrid layout in our research.

Resolving soft X-ray photons with a high-rate hybrid pixel detector

Due to their high frame rates and dynamic range, large area coverage, and high signal-to-noise ratio, hybrid silicon pixel detectors are an established standard for photon science applications at X-ray energies between 2 keV and 20 keV. These properties also make hybrid detectors interesting for experiments with soft X-rays between 200 eV and 2 keV. In this energy range, however, standard hybrid detectors are limited by the quantum efficiency of the sensor and the noise of the readout electronics. These limitations can be overcome by utilizing inverse Low-Gain Avalanche Diode (iLGAD) sensors with an optimized X-ray entrance window. We have developed and characterized a prototype soft X-ray iLGAD sensor bonded to the charge integrating 75 µm pixel JUNGFRAU chip. Cooled to −22°C, the system multiplication factor of the signal generated by an impinging photon is ≥ 11. With this gain, the effective equivalent noise charge of the system is ≤5.5 electrons root-mean-square at a 5 µs integration time. We show that by cooling the system below −50°C, single photon resolution at 200 eV becomes feasible with a signal-to-noise ratio better than 5.

Quantum random number generation based on phase reconstruction.

Quantum random number generator (QRNG) utilizes the intrinsic randomness of quantum systems to generate completely unpredictable and genuine random numbers, finding wide applications across many fields. QRNGs relying on the phase noise of a laser have attracted considerable attention due to their straightforward system architecture and high random number generation rates. However, traditional phase noise QRNGs suffer from a 50% loss of quantum entropy during the randomness extraction process. In this paper, we propose a phase-reconstruction quantum random number generation scheme, in which the phase noise of a laser is reconstructed by simultaneously measuring the orthogonal quadratures of the light field using balanced detectors. This enables direct discretization of uniform phase noise, and the min-entropy can achieve a value of 1. Furthermore, our approach exhibits inherent robustness against the classical phase fluctuations of the unbalanced interferometer, eliminating the need for active compensation. Finally, we conducted experimental validation using commercial optical hybrid and balanced detectors, achieving a random number generation rate of 1.96 Gbps at a sampling rate of 200 MSa/s.

The SparkPix-S ASIC for the sparsified readout of 1 MHz frame-rate X-ray cameras at LCLS-II: pixel design and simulation results

Exploiting the “sparse” nature of the information in XPCS (X-ray Photon Correlation Spectroscopy) and XSVS (Speckle Visibility Spectroscopy) experiments, we present the SparkPix-S, a 3-sides buttable Application Specific Integrated Circuit (ASIC) based on a sparsified readout strategy for large-format hybrid detectors. The SparkPix-S architecture, based on the successful ePix family, will be composed as follows: a front-end 2-D matrix of 384×352 square pixels with 50 µm pitch is arranged to match the dimensions of a PIN Si-sensor matrix; charge readout, signal shaping and amplitude discrimination is performed at pixel-level, by means of a low-power (<18 µW) analog processor, which, in case of an event, negotiates access to an analog bus placed every other column; on the chip periphery (balcony), the information on each bus is digitized by an array of successive approximation analog-to-digital converters (SAR-ADCs) running at 10 Msps; on the digital back-end the global logic will generate the output data stream using low-voltage differential signalling (LVDS).A first prototype of the SparkPix-S, with a reduced matrix size of 96×96 pixels, is currently under production on a 130 nm CMOS technology. Simulated performance results show an equivalent noise charge <60 el. r.m.s. at 1 MHz repetition rate, with a maximum input energy of 60 keV and capability to discriminate charge signals with equivalent energy as low as 900 eV.

Characterization of iLGADs using soft X-rays

Experiments at synchrotron radiation sources and X-ray Free-Electron Lasers in the soft X-ray energy range (250 eV–2 keV) stand to benefit from the adaptation of the hybrid silicon detector technology for low energy photons. Inverse Low Gain Avalanche Diode (iLGAD) sensors provide an internal gain, enhancing the signal-to-noise ratio and allowing single photon detection below 1 keV using hybrid detectors. In addition, an optimization of the entrance window of these sensors enhances their quantum efficiency (QE).In this work, the QE and the gain of a batch of different iLGAD diodes with optimized entrance windows were characterized using soft X-rays at the Surface/Interface:Microscopy beamline of the Swiss Light Source synchrotron. Above 250 eV, the QE is larger than 55% for all sensor variations, while the charge collection efficiency is close to 100%. The average gain depends on the gain layer design of the iLGADs and increases with photon energy. A fitting procedure is introduced to extract the multiplication factor as a function of the absorption depth of X-ray photons inside the sensors. In particular, the multiplication factors for electron- and hole-triggered avalanches are estimated, corresponding to photon absorption beyond or before the gain layer, respectively.

Integration and first operation of the Gotthard-II detector at European XFEL

Gotthard-II (G-II) is a 1-D silicon microstrip hybrid detector developed by the Paul Scherrer Institut within the framework of a collaboration agreement with the European XFEL. The ASIC features a dynamic gain switching architecture, in order to cope with the luminosity of European XFEL, and a 12-bit analog-to-digital converter with a sampling/conversion rate of more than 18 MS/s as well as a Static random-access memory, making it capable of matching the European XFEL pulse train structure, thus acquiring up to 2700 images at 4.5 MHz per burst. The sensor’s strip pitch can be either of 50 μm or 25 μm , for a total of 1280 or 2560 output channels per detector, respectively, with a spectral sensitivity that allows either X-ray detection (optimized in the 5–20 keV range) or visible light detection. Its exceptionally good compliance with the European XFEL beam conditions will make G-II the most widely employed detector across the facility, with a total of 29 modules of different flavors that will be installed in scientific instruments and beam diagnostic setups. Although the detector will be predominantly used for spectroscopic measurements it will have a variety of other applications, including X-ray diffraction/emission/absorption experiments, relative pulse arrival time monitoring (of fundamental importance for pump–probe experiments), spectral diagnostics, and beam quality monitoring, with the possibility for the detector itself to generate a veto patterns for the large area MHz framerate pixel detectors employed at the scientific instruments, such as AGIPD, LPD and DSSC. In this paper, an overview of G-II detector technology and its usage at the European XFEL will be presented; the focus will then move on towards the process of detector integration in the European XFEL control system, data acquisition, and data correction infrastructure, highlighting its challenges. Finally, an overview of the first results obtained at scientific instruments will be given.

Highlights from the Telescope Array Experiment

The Telescope Array (TA) is the largest hybrid cosmic ray detector in the Northern Hemisphere, which observes primary particles in the energy range from 2 PeV to 100 EeV. The main TA detector consists of 507 plastic scintillation counters on a 1.2-km spacing square grid and fluorescence detectors at three stations overlooking the sky above the surface detector array. The TA Low energy Extension (TALE) detector, which consists of ten fluorescence telescopes, and 80 infill surface detectors with 400m and 600 m spacing, has continued to provide stable observations since its construction completion in 2018. The TAx4, a plan to quadruple the detection area of TA is also ongoing. About half of the planned surface detectors have been deployed, and the current TAx4 continues to operate stably as a hybrid detector. I review the present status of the TA experiment and the recent results on the cosmic-ray anisotropy, mass composition and energy spectrum.

TAIGA - An advanced hybrid detector complex for astroparticle physics and high energy gamma-ray astronomy

The physical motivations, present status, main results in study of cosmic rays and in the field of gamma-ray astronomy as well future plans of the TAIGA-1 (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented. The TAIGA observatory addresses ground-based gamma-ray astronomy and astroparticle physics at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV. The pilot TAIGA-1 complex is located in the Tunka valley, ~50 km west from the southern tip of the lake Baikal.

Simulation of the Response of a Hybrid Detector Based on Scintillation Optical Fibers and an Emulsion Chamber

Simulation of the Response of a Hybrid Detector Based on Scintillation Optical Fibers and an Emulsion Chamber

A 64k pixel CMOS-DEPFET module for the soft X-rays DSSC imager operating at MHz-frame rates

The 64k pixel DEPFET module is the key sensitive component of the DEPFET Sensor with Signal Compression (DSSC), a large area 2D hybrid detector for capturing and measuring soft X-rays at the European XFEL. The final 1-megapixel camera has to detect photons with energies between 250,text{eV} and 6,text{keV}, and must provide a peak frame rate of 4.5,text{MHz} to cope with the unique bunch structure of the European XFEL. This work summarizes the functionalities and properties of the first modules assembled with full-format CMOS-DEPFET arrays, featuring 512,times ,128 hexagonally-shaped pixels with a side length of 136 μm. The pixel sensors utilize the DEPFET technology to realize an extremely low input capacitance for excellent energy resolution and, at the same time, an intrinsic capability of signal compression without any gain switching. Each pixel of the readout ASIC includes a DEPFET-bias current cancellation circuitry, a trapezoidal-shaping filter, a 9-bit ADC and a 800-word long digital memory. The trimming, calibration and final characterization were performed in a laboratory test-bench at DESY. All detector features are assessed at 18,^{circ }text{C}. An outstanding equivalent noise charge of 9.8e−rms is achieved at 1.1-MHz frame rate and gain of 26.8 Analog-to-Digital Unit per keV (,text {ADU}/text{keV}). At 4.5,text{MHz} and 3.1,,text {ADU}/text{keV}, a noise of 25.5 e−rms and a dynamic range of 26,text{k}text {e}^{-} are obtained. The highest dynamic range of 1.345,text{M}text {e}^{-} is reached at 2.25,text{MHz} and 1.6,text {ADU}/text{keV}. These values can fulfill the specification of the DSSC project.

Photon counting-energy integrating hybrid flat panel detector systems for image-guided interventions: an experimental proof-of-concept

Objective. Current C-arm x-ray systems equipped with scintillator-based flat panel detectors (FPDs) lack sufficient low-contrast detectability and spectral, high-resolution capabilities much desired for certain interventional procedures. Semiconductor-based direct-conversion photon counting detectors (PCDs) offer these imaging capabilities, although the cost of full field-of-view (FOV) PCD is still too high at the moment. The purpose of this work was to present a hybrid photon counting-energy integrating FPD design as a cost-effective solution to high-quality interventional imaging. Approach. In the proposed hybrid detector design, the central scintillator and thin-film transistor elements in the FPD are replaced with a semiconductor PCD module to upgrade the imaging capabilities of the C-arm system while preserving the full FOV coverage. The central PCD module can be used for high-quality 2D and 3D region-of-interest imaging with improved spatial- and temporal-resolution as well as spectral resolving capability. An experimental proof-of-concept was conducted using a 30 × 2.5 cm2 CdTe PCD and a 40 × 30 cm2 CsI(Tl)-aSi(H) FPD. Main results. Phantom and in vivo animal studies show (1) improved visualization of small stent wires in both 2D and 3D images due to the better spatial resolution of the PCD; (2) dual-energy angiography imaging capability by using the spectral PCD; (3) better conspicuity of small peripheral iodinated vessels (contrast-to-noise ratio improvement range: (29%, 151%)); (4) the central PCD outputs can be fused seamlessly with the surrounding scintillator detector outputs to provide full field imaging: A post-processing chain was developed by leveraging the PCD’s spectral information to match the image contrast of the PCD images to the surrounding scintillator detector, followed by spatial filtering of the PCD image to match noise texture and spatial resolution. Significance. The hybrid FPD design provides a cost-effective option to upgrade C-arm systems with spectral and ultra-high resolution capabilities without interfering with the clinical need for full FOV imaging.

Enhancing Photoresponse of GaAs-Based Photodetector by Plasmon Grating Structures

Nanostructured metal–semiconductor-metal photodetectors (MSM-PDs) can assist in future high-speed communication devices for achieving high responsivity characteristics. However, such devices suffer from low responsivity due to low absorption, and the large band gap limits its detection range. Herein, we propose a GaAs-based photodetector with enhanced photoresponse by plasmonic Au-GaAs grating structure. The design of a grating structure on the surface of n-GaAs can excite a plasmon mode to enhance the photoelectric performance of photodetectors. Consequently, under 795 nm incident light irradiation, the grating hybrid detector exhibits a nearly 4.2-fold increase in photocurrent compared to the bare GaAs device. The enhanced absorption can be up to 99% and a specific responsivity of 240 mA/W is realized. These results can thus provide a potential scheme to fabricate high-performance GaAs detector for numerous applications.

The energy spectrum of cosmic rays measured by the Telescope Array using 10 years of fluorescence detector data

The Telescope Array (TA) Cosmic Ray Observatory is the largest cosmic ray detector in the northern hemisphere. TA was built to study ultra-high-energy cosmic rays (UHECRs), cosmic rays with energies above 1018eV. TA is a hybrid detector, employing two distinct detection methods: a surface detector array and a set of fluorescence telescopes. We will present a measurement of the cosmic ray energy spectrum for energies above 1017.5eV using only the fluorescence telescopes. A novel weather classification scheme using machine learning was used to select data parts with good weather to ensure the quality of the fluorescence data. The data from the Black Rock Mesa (BRM) and Long Ridge (LR) fluorescence telescope sites were analyzed separately in monocular mode, with the calculated fluxes combined into a single spectrum. The 10-year monocular combined cosmic ray energy spectrum is observed to be in excellent agreement with previous measurements from the northern hemisphere. We present fits of the combined spectrum to a series of broken power law models. The thrice-broken power law was observed to be the best fit considering the Poisson deviance per degrees of freedom. The three breaks suggest an additional feature of the spectrum between the previously observed Ankle feature at 1018.7eV and the GZK suppression at 1019.8eV.