Detector Structure Research Articles

Millimeter-Wave Response of All Metal-Organic Deposited YBCO Transition Edge Bolometer

We report on the response of a monolithic high $\mathrm{T_{c}}$ transition-edge bolometer to about 3 mmWave for the first time. The detector structure consisting of 400-nm $\mathrm{YBa_{2}Cu_{3}O_{7-x}}$ (YBCO) film on buffered yttria stabilized zirconia substrate without any coupled antenna, shows bolometric type responsivity to the 3-mmWave radiation at its transition temperature. The YBCO thin film and $\mathrm{Ce_{0.9}La_{0.1}O_{2}}$ buffer layer are both fabricated by the metal-organic deposition method. The meander line pattern of the bolometer is designed for obtaining maximum absorption and responsivity possible when the polarized radiation of the source is aligned with the pattern. Meander lines are 50 micrometers wide and 1.5-mm long. We have measured amplitude and phase of the response versus modulation frequency of the detector to the linearly polarized 95-GHz source, and the detector was biased at five distinct temperatures at the transition corresponding to five different electrical conductivities of the YBCO film. When the meander lines of the device are parallel to the incident beam polarization, the YBCO pattern is speculated to act as a dissipative antenna resulting in higher absorption leading to high magnitude of the response as observed. The results from the measured phase of the response versus modulation frequency are also in agreement with the discussed absorbed mechanism. The absorption of the YBCO pattern is also measured to depend on the electrical conductivity of the YBCO film and our results show that there is an optimum electrical conductivity for having maximum absorption for this detector. Simulation results for this structure confirm the experiments showing that at electrical conductivity value of $\mathrm{1.33\times 10^{5}}$ S/m we have the maximum absorption for our device. These observations promise design of versatile THz and millimeter-wave detectors with potential for applications in medical and security imaging.

Design and Simulation of 3-D CdTe Pillar Detectors

In this article, a proposed 3-D cadmium telluride (CdTe) detector structure is presented and investigated. The electrical performance of the proposed structure is studied using 3-D TCAD simulations. The obtained results could be considered as a proof of concept for the feasibility of the performance of the presented detector under different operating conditions. For the proposed structure, the collection time is found to be about 1.3 ns at 15 V. The fast and hard response of the structure makes it suitable for high energy beams detection. The very low leakage current, which is about 16 pA at 16 V, allows the application of high bias voltages. Higher bias voltages (up to 16 V) may be required to decrease the proposed CdTe detector collection time without affecting its quality. Although the proposed detector structure is more appropriate to be biased at high voltages, these voltage values are still more less than those required in 2-D detectors. Based on this study, the proposed 3-D CdTe detector can be recommended for future high-energy physics and medical applications.

Desarrollo de Técnicas de Muongrafía para Estudios Densitométricos de Objetos de Importancia Estratégica

La muongrafía es una técnica de prospección no destructiva que permite la determinación de la estructura interna de grandes estructuras tanto naturales como artificiales, por ejemplo volcanes. Esto es posible al construir una imagen con base en la absorción diferencial del flujo direccional de muones atmosféricos producto de la interacción de rayos cósmicos con la atmósfera. Este trabajo doctoral es desarrollado con el propósito principal de aportar en el avance de la muongrafía como técnica de prospección en Geofísica. El trabajo se compone de dos lineas de trabajo, una experimental y una teórica. La experimental se basa en el desarrollo de un prototipo de detector de astropartículas con base en centelladores plásticos y fotomultiplicadores, para esto se usa una electrónica de adquisición desarrollada para el proyecto AMIGA en el Observatorio Pierre Auger y materiales centelladores de plástico. La segunda linea de trabajo trata del estudio del detector y las estructuras de investigación a través de simulaciones computacionales y modelos teóricos. Durante los dos primeros años se completaron los créditos de cursos solicitados por el doctorado, Ademas se trabajó en el estudio de la respuesta de la electrónica, los pulsos, técnicas de análisis de datos y el acople de fotomultiplicadores con los centelladores. Gracias a esto se avanzo en el desarrollo del prototipo y se investigo la posibilidad de incrementar la resolución espacial a través de la detección sincrónica usando electrónicas conectadas al mismo centellador. Actualmente iniciamos el trabajo en los modelos computacionales, estamos estudiando e investigando con respecto a los candidatos a objetos de estudio, destacando el volcán Copahue, volcán Peteroa y la posibilidad de realizar mediciones bajo tierra.

Cover Picture

Cryo‐electron diffraction tomography (Cryo‐EDT) has been developed to determine the crystal structures of covalent organic frameworks (COFs) and their host‐guest interaction at the atomic precision, whose crystals are only submicron‐sized, organic, porous, and dynamic. The keys of 3D electron diffraction (3D‐ED) techniques are low‐dose beam, sample cryo‐handling, fast data collection, sensitive detector, and direct space structure solution. We envision the development of COF chemistry will be propelled by such powerful 3D‐ED techniques for a better understanding at the molecular level and correlation of structures to chemicophysical properties. More details are discussed in the article by Zhang et al. on page 1153—1166.image

Study of Schottky barrier detectors based on a high quality 4H-SiC epitaxial layer with different thickness

Schottky barrier detectors based on a high-quality 4H-SiC epitaxial layer with varied thickness up to 70 μm were studied. The detectors had front-side circular Ni/Au Schottky contacts and a back-side full-area Ti/Pt/Au ohmic contact. Current-voltage characteristics in the reverse and forward directions of prepared detector structures were measured. The typical reverse current of the detector structure was below 50 pA at room temperature. The Schottky barrier height, series resistance and ideality factor were evaluated from the forward part of the current-voltage characteristics, and they were 1.3 eV, 1.33, and 638 Ω, respectively. Capacitance-voltage measurement of the detectors up to 600 Vwas also realized. This provided data to calculate the depletion width, concentration profile and barrier height. The lowest doping concentration of about 7 × 1013 cm−3 was determined. The spectrometric performance of the Schottky barrier detector structures was analyzed using an α-particle radioisotope source. The detector structures demonstrated a high energy resolution below 20 keV in the full width at half maximum for 5.5 MeV α-particles.

High-precision spot positioning algorithm based on four-quadrant detector

Inherent errors and random errors are consisting in four-quadrant detector when used for azimuth measurement. Many spot fitting algorithms are proposed to solve the inherent errors caused by the structure of the four-quadrant detector itself, which can reduce the errors in a way. In order to further improve the spot positioning accuracy and eliminate the influence caused by random errors such as background light and thermal noise, we first perform Kalman filtering on the output of the four quadrants when we perform experiments to calibrate parameters. Build an experimental platform, and experimentally verify that the Kalman filtering of the output of the four quadrants before bringing in the spot positioning algorithm can improve the accuracy of the composite fitting algorithm, thereby improving the positioning accuracy.

New method for estimating detector efficiency for charged particles with Diamond Light Source

Detector prototypes are commonly characterised in testbeams, either using charged particles or X-rays. Charged particles are used to quantify detector performance in terms of absolute efficiency, while X-rays can provide additional information about the detector structure. This paper presents an alternative approach to calculating charged particle efficiencies, using the results of an X-ray testbeam of the mini-MALTA CMOS prototype at Diamond Light Source, and additional laboratory measurements. Results are presented for an unirradiated and an irradiated sample and compared to the results of charged particle testbeams at SPS and ELSA. The extrapolated efficiencies are in agreement with the measured values. Additionally, the extrapolated efficiency maps provide more insight about the location of the pixel inefficiencies, due to the better spatial resolution of the X-ray testbeam.

Solar interference test for flame detectors based on natural lighting

In order to evaluate the anti-interference performance of the flame detector applied to the environment with possible solar interference, the feasibility of standardized test method for solar interference of flame detectors is researched in this paper. According to the characteristics such as structure, use place and installation mode of flame detector, the radiation model and illuminance model of solar interference are constructed. Through statistical analysis of photo-climatic data of regional representative cities, the severity level of the solar interference that reflecting national lighting conditions is summarized and classified. On this basis, data analysis of natural lighting resources of 8 typical cities in China is carried out. Combined with natural lighting test schemes, the feasibility of the solar interference test for flame detectors is analyzed, and relevant conclusions are drawn.

Design, electrical properties and fabrication method study of a novel 3D-Compound-Shell-Electrode silicon detector

In this work, a novel three-dimensional (3D) structure of silicon detector: 3D-Compound-Shell-Electrode detector (3DCSED), based on the 3D-Trench-Electrode detector and 3D-Open-Shell-Electrode detector (3DOSED), is proposed. In a 3DCSED, an open trench electrode will be etched about 10% of the detector thickness from the bottom side of the detector to meet the close trench electrode etched about 90% of the detector thickness from the top side. This not only makes the unit structure stable in the fabrication process, but also improves the detection efficiency through the optimization of the electrode structure compared to the conventional 3D-Trench-Electrode detector. In order to optimize the 3DCSED structure, it is important to study 3DCSED’s electrical properties by full 3D technology computer-aided design (TCAD) simulations. From the electric field distribution results, detector charge collection efficiency has been simulated and optimized by incorporating charge trapping caused by irradiation. Due to the highly doped trench walls, each pixel cell is electrically isolated to ensure a uniform electric field distribution. However, each pixel cell is physically connected to its neighboring cells, therefore also connected to the Si substrate, through the small portion of broken electrodes in the 3DOSED bulk (about 10% of the detector thickness from the bottom side of the detector). Furthermore, current–voltage (I–V) characteristics and full depletion voltage have been analyzed to study the detector’s properties. We also propose a method to fabricate the 3DCSED. In this method, the deep etching is processed by Deep Reacting Ion Etching (DRIE) or laser with respective processing procedures.

Structure optimization of the silicon detector: A novel three-dimensional trench detector

In this study, a novel three-dimensional trench detector structure was proposed. The detector structure includes trench electrodes and columnar electrodes. The columnar electrodes are distributed in the middle, the middle of the sides, and the four corners of the cross section of the substrate. A cross-shaped electrode is etched from top to bottom, and a polygonal trench electrode is etched from bottom to top; the bottom of the cross-shaped electrode abuts the top of the polygonal electrode. Electrical characteristics of the novel detector are simulated by Technology Computer Aided Design simulation, and we can obtain that this design reduces the area of the bottom low electric field, optimizes the electric field, and reduces the mutual interference between the cells.

Influence of the CdZnTe Substrate Thickness on the Response of HgCdTe Detectors Under Irradiation: Modeling of the Substrate Luminescence

The most extensively used infrared (IR) detectors in astrophysics are based on mercury cadmium telluride (MCT) technology: the MCT light-sensitive layer is grown on a cadmium zinc telluride (CZT) substrate. When launched on a satellite, these detectors are subjected to ionizing radiation from cosmic rays or solar flares (mainly protons) which degrade the detector performance. Indeed, an elevation of the detector background was noted under irradiation, which is believed to be associated with the luminescence of the CZT substrate. Complete removal of the substrate eliminates the problem, but it is a challenging step in the fabrication process. A deeper understanding of the response of IR detectors under irradiation, when the substrate is fully removed, will enable the optimization of substrate design for high-performance space-based scientific imaging. Here, the first results of proton irradiation modeling in MCT detectors, including energy deposition in the CZT substrate, are presented. The estimation of image pollution relies on GEANT4 (GEometry ANd Tracking 4) Monte Carlo simulations as well as analytical and numerical calculations of carrier transport inside the detector structure. In particular, recombination processes in the CZT substrate are taken into account to model the luminescence effect induced by proton irradiation. According to this model, considering published material properties, the diffusion of the carriers generated inside the CZT substrate toward the MCT layer is the main source of pollution. As the substrate thickness increases, more pixels are impacted by a proton impact on the IR. Consequently, depending on the targeted application, either partial or complete removal may be chosen.

Design of a MAPS readout electronics prototype for BESIII inner tracker

The spatial resolution and the reconstruction efficiency of the main drift chamber of the Beijing Spectrometer III has degraded after more than nine years of operation. An improved new inner drift chamber has been constructed to replace the old chamber in case of the radiation damage. A monolithic active pixel sensor (MAPS) based detector prototype is selected as one of the prototype schemes for the inner chamber upgrade. Design a set of MAPS readout electronics system for the inner drift chamber upgrade. This system can verify the function and performance of the selected MAPS chip and discover the matters needing attention when designing large-scale detectors. The electronics system design is composed of three parts. The first part is flexible printed circuit boards (PCBs) assembled with the MAPS chips. The second part is digital readout boards, which are connected to the flexible PCBs via FPGA mezzanine card cables. The digital readout board realizes the configuration of the MAPS chip register, receives and processes the data output by the MAPS chip, and transfers the processed data to the DAQ device. The third part includes a readout control board and two fan-out boards that used to separately fan out the trigger signal and the start signal to all the digital readout boards. A MAPS readout electronics system consisting of five MAPS based detector prototypes is designed. The system can work stably under the electron beam experimental conditions with a frequency up to 2 kHz and energy ranging from 1 to 5 GeV. The system detection efficiency of the electron beam is $$\sim 95\%$$, and the spatial resolution is $$\sim 5.3\, \upmu \hbox {m}$$ at electron energies of 1 GeV. The design of the electronics system meets the requirements for verifying the performance of the MAPS chips and the technical feasibility of the detector structure.

Investigation of Copper-Less Gas Electron Multiplier Detectors Responses to Soft X-rays.

In this paper, we report on the systematic study of different variants of X-ray detectors based on Gas Electron Multiplier (GEM) technology using modified GEM foils with greatly reduced amount of copper. The main goal of this study was understanding the performance of such detectors applied in X-Ray Fluorescence (XRF) elemental analysis. Reduction of the amount of copper in the detector structure is crucial for suppression of XRF background from copper, but one has to ensure that key detector parameters are not affected by such modification. The tested detector variants include detectors with different types of copper-less GEM foils, which have been manufactured starting from standard copper-clad foils and removing partially the copper layer in additional post-processing steps. The results are analyzed and discussed with a particular focus on the energy resolution, uniformity of gas gain and energy resolution across the detector area, and on the long-term stability of the gas gain. Long-term stability tests performed for selected detectors do not indicate for any accelerated aging of the copper-less detectors compared to standard detectors using copper-clad GEM foils. The presented results lead us to conclude that the copper-less GEM detectors are promising devices to suppress the XRF background.

A Note on Implementation Methodologies of Deep Learning-Based Signal Detection for Conventional MIMO Transmitters

Baek et al. proposed a deep learning-based signal detector for conventional MIMO systems, which is a pioneering work of applying artificial intelligence into wireless communications. Although this work works well under static fading channels, it is worth notable that it fails to work under block-fading channels. In particular, the detection BER under block-fading channels is around 0.5 even in the high regime of SNR. To explain this unexpected result, we provide some simple yet efficient theoretical analysis, which clearly verifies that the proposed detector cannot decouple the phases between the channel parameters and transmitted signals and hence it fails to detect the transmitted signals under block-fading channels. The results in this paper can help understand and improve the detector. In particular, the detector structure should incorporate the channel state information for the application under block-fading channels.

Large area BM@N GEM detectors

Baryonic Matter at Nuclotron (BM@N) is a fixed target experiment at the NICA accelerator complex in JINR aimed to study nuclear matter in relativistic heavy ion collisions. Detectors based on Gas Electron Multipliers (GEM) are used for the central tracking system of the BM@N experiment, which is located inside the BM@N analyzing magnet. The structure of the GEM detectors and the results of study of their characteristics are presented. The performance of seven GEM detectors integrated into the BM@N experimental setup and data acquisition system is briefly reviewed.

Recent Developments of Amorphous Selenium-Based X-Ray Detectors: A Review

Amorphous selenium (a-Se) is a photoconductive material that has been intensively investigated from its early application in xerography to its present application in flat panel X-ray imagers. It can be deposited up to a few millimeters thick over a large area. Its high vapor pressure yields uniform coverage in novel device structures for low-cost and large-area applications. The evidence of avalanche multiplication in a-Se and application of a-Se in high-gain avalanche rushing photoconductor video-tubes goes back to the early 1980s. Over the past decade there has been increasing research interest in novel detector structures and integration of a-Se with new materials to leverage the avalanche properties. We summarize some of the shortcomings of a-Se such as low charge carrier mobility, low charge conversion efficiency, depth dependence, and high dark current at high electric fields. We then highlight recent developments in a-Se-based devices to address these shortcomings and enable picosecond timing performance and high detection efficiency.

Simulations of X-ray conversion into primary electrons in GEM-based detector

The paper presents the results of simulations of the interaction of X-rays of different discrete energies (1–25 keV) with the structure of the GEM chamber. The simulations were performed using Geant4 software. This program allowed taking into account phenomena such as the emission of photoelectrons, Auger electrons and fluorescence X-rays. As a result, the energy distributions of primary electrons formed in the absorption region of the detector (drift gap) were obtained. The distributions of primary electrons, which are the source of electron avalanches in the detector under study, are directly responsible for the distribution of pulses on the detector reading anode. Some measurements were also performed, confirming the compatibility of simulated spectra and experimental ones. The main conclusion from the simulation is the need to eliminate copper from the detector structure, especially from GEM foils and from the reading electrode, if there is an intension to record X-rays with energies above 9 keV . An observable parasitic contribution to the spectrum recorded by the detector is also given by several other materials.

Influence of Internal Structure of Semiconductor Detector on Spectrum of X-Rays Induced by Tritium Beta Rays

Nondestructive measurement of tritium (T) content in solid materials is important for safe and cost-effective disposal of contaminated wastes, and beta-ray induced X-ray spectrometry (BIXS) has been developed for this purpose. A common way to obtain depth profiles of T in solids using BIXS is to perform simulation of X-ray spectra for assumed depth profiles and find a profile giving the best agreement with observation. A detailed understanding of attenuation of low-energy X-rays (≤18.6 keV) by detector components such as a window material is required for interpretation of measured spectra and simulation. In this study, BIXS spectra of a tungsten reference sample with known T depth profile were measured using two different semiconductor detectors and simulated using the Monte Carlo simulation toolkit Geant4. In the low-energy region (<2 keV), the difference in internal structure resulted in a noticeable difference in the BIXS spectra. The disagreement between the measured and the simulated spectra was also significant at <2 keV. Nevertheless, at >2 keV, the BIXS spectra were insensitive to the internal structure of the detector, and the simulated spectra agreed well with the measured ones. The mechanism underlying the difference in the low-energy region was discussed.

Startup characteristics of a multi-evaporator cryogenic loop heat pipe

With the rapid development of space exploration technology, the traditional point-to-point heat transfer methods cannot fulfill the heat dissipation requirements of multi- and large-array detectors. Loop heat pipe is an effective and efficient two-phase heat transfer device that has played a significant role in spacecraft for the thermal control system. In addition, it has high heat transfer efficiency, long heat transfer distance, heat switch characteristics, and pipeline flexibility. However, higher requirements are proposed for space thermal control. We need to design and handle more complicated detector structures, heat dissipation from scattered distribution, and heat dissipation of large area array. In this work, a heterotypic loop heat pipe has been investigated to solve the heat dissipation issue of a multi-point distributed heat source. A multi-evaporator loop heat pipe (MeLHP) in low temperature is designed and manufactured, via connecting three evaporators in parallel with gas coupling method. The pipelines are arranged asymmetrically as required. The working temperature is set to 170 K while ethane has been used as a working fluid. A series of experiments are conducted to study the start-up characteristics of the prototype. Different heating methods and various charging ratios are compared with a single evaporator loop heat pipe, where the MeLHP prototype is explored variously in the process of cooling and start-up. Initially, a start-up experiment of a single evaporator loop heat pipe is carried out. As we know, the loop heat pipe (LHP) research is relatively mature, so all the conditions of LHP are adopted for the startup characteristics of MeLHP’s. It is found that every single evaporator of MeLHP has similar performance to that of LHP. Later, we employ different experimental conditions on the evaporators such as various charging ratios and different heating methods. The temperature fluctuation and heat sharing characteristics are compressively analyzed from the comparison of temperature curves at different working conditions. Finally, the experimental process is verified from the nice comparison of single evaporator temperature change and cooling rate of each case. In addition, we observe that evaporators in each loop of MeLHP are highly uniform compared to that of a single evaporator loop heat pipe, during the start-up process. So, MeLHP can start under the condition of single evaporator heating and multiple evaporators heating as well. When a single evaporator heating process takes place in MeLHP, the unheated evaporators share the heat via the influence of gas coupling from the heated evaporators. So, this process simultaneously starts three evaporators; the initial state of working fluid would influence the temperature of each evaporator during cooling, while the heat exchange of gas coupling effectively inhibits the effect of evaporators’ temperature. The structure of gas coupling effectively shares the heating load among all evaporators. Different charging ratios affect the start-up process of MeLHP. Compared to the charging ratio of LHP (0.6), the results of MeLHP are consistent with LHP at a charging ratio of 0.7. So, the fluid charging ratio of MeLHP should be appropriately increased to obtain an equivalent performance to that of a single loop heat pipe. Our experiments have verified the start-up feasibility of a multi-evaporator loop heat pipe with parallel gas coupling, revealed the law of cooling, and the start-up process, which is highly significant for the promotion and application of MeLHP.

A CNN-LSTM Network for Augmenting Target Detection in Real Maritime Wide Area Surveillance Radar Data

Typical radar detectors exploit only a small proportion of the valuable information contained in radar reflections, i.e. magnitude and Doppler. A neural network-based approach for augmenting traditional radar detector structures using machine learning (ML) is proposed in this paper. Specifically, the network is designed to augment target detection in the field of maritime wide area surveillance for non-coherent data. A combination network consisting of a convolutional neural network (CNN) to extract spatial features and a long short-term memory (LSTM) for extracting temporal patterns in the spatial features is proposed. The network augments the detector structure by blanking out regions of the frame which are classified as not containing a target, thus reducing false alarms. The network is tested on data containing four marine targets collected by a ground-based radar. The data set was chosen because it contains strong sea clutter returns. When ML is used, the receiver operating characteristic (ROC) curves are shifted to lower probability of false alarm (PFA). A Kalman filter tracker was applied to the ML-augmented and baseline detections, and it was shown that ML-augmented detections produced similar tracks at lower PFA. The feature discovering capability of the network is analyzed through a series of tests, and the argument is made that the CNN-LSTM network presented in this work demonstrates the ability to improve the detection performance by exploiting spatial and temporal information in the data.