Emitter Source Research Articles

Multicolor Emission in Indium-Doped Amorphous Boron Nitride Integrated on Silicon for Self-Biased and High-Speed Photodetection.

Boron nitride (BN), as an emergent wide-bandgap material, is gaining considerable attention as a solid-state deep ultraviolet source and quantum emitter from the ultraviolet to the near-infrared spectral ranges. However, studies of the defect structure of BN and efforts at scalable BN emitters in photonic devices are limited. Controlling the BN doping is of particular interest in view of the light emission of defects. Here, it is demonstrated for the first time that doping amorphous BN (a-BN) with indium (In) shows luminescence spectra tuning from blue to red light, and only 765 nm (1.63 eV) light is dominant when more In content is introduced. The visible light emission is found to be the transition between the defect center of InN (a substitutional In of nitrogen) and ONVB (a substitutional oxygen with an adjacent boron vacancy). While ONVB is identified experimentally in accordance with previous theoretical assumptions, and is optically accessible with a zero-phonon line (ZPL) of about 1.63 eV with increasing In proportion. Moreover, the heterogeneous integration of synthesized In-doped a-BN in silicon platforms is demonstrated by the realization of a 700-1000 nm broadband photodetector. These devices operate self-biased at room temperature and show a high photoresponsivity of ∼1.5 A/W (at 980 nm with -2 V bias), a quick response time of ∼90 μs, and a detectivity of 1.02 × 109 cm·Hz1/2/W. This work fundamentally contributes to establishing infrared detection by doping a-BN materials in heterojunctions with Si, at the forefront of infrared optoelectronics.

Enhancing radiative sky cooling performance by employing crossed compound parabolic concentrating configurations

Achieving superior radiative sky cooling (RC) performance in practical applications is challenging due to its cooling power is easily compromised by unwanted thermal energy influxes, including solar heat gain and thermal radiation from nearby warm objects. To address this issue, the present work introduces the integration of affiliated crossed compound parabolic concentrators (CPC) as a means to effectively mitigate this thermal burden. Through the development of a comprehensive mathematical framework that characterizes the heat exchange between the RC emitter and different environmental heat sources, the cooling performance of the novel crossed CPC-RC module is evaluated and compared with other RC configurations. The results show that due to its excellent capability to shield unfavourable heat inflows from large zenith angles, the crossed CPC-RC module shows the potential to reach a cooling power density of 99.50 W/m2 at noon, outperforming the flat-RC and 2D CPC-RC modules by 5.1% and 41.7%, respectively. Furthermore, key parameters optimization and the cooling performance assessment throughout a typical summer day is carried out to demonstrate the superiority of the crossed CPC structure in boosting cooling capacity, particularly the cooling benefits throughout the day, thereby offering a promising solution to better align with the cooling demands of buildings.

Modelling Backward Trajectories of Air Masses for Identifying Sources of Particulate Matter Originating from Coal Combustion in a Combined Heat and Power Plant

The paper analyzes the processes of emission and dispersion of particulate contaminants from a large point source emitter: a hard coal-fired power plant. Reference is made to the European Green Deal and its main objective of reducing anthropogenic particulate and greenhouse gas emissions. CHPP, Krakow Combined Heat and Power Plant, Poland, as described in the article, has a strong impact on the mechanisms that shape the microclimatic factors of the Krakow agglomeration. This combined heat and power plant provides heat and electricity for the city, while simultaneously emitting significant amounts of suspended particulate matter into the atmosphere. Due to the adverse impact of non-conventional energy sources on the natural environment and the increasing effects of climate warming, radical changes need to be implemented. The HYSPLIT (Hybrid Single-Particles Lagrangian Integrated Trajectories) model was used to track the movement of contaminated air masses. A 5-day episode of increased hourly concentrations of PM2.5 particulate matter contamination was selected to analyze the backward trajectories of air mass displacement. From 15 August 2022 to 19 August 2022, high 24-h particulate matter concentrations were recorded, measuring around 20 µg/m3. The HYSPLIT model, a unique tool in the precise identification of point sources of pollution and their impact on the air quality of the region, was used to analyze the influx of polluted air masses. A 5-day episode of increased hourly concentrations of PM2.5 pollutants was selected for the study, with values of approximately 20 µg/m3. It was found that low-pressure systems over the North Atlantic brought wet and variable weather conditions, while high-pressure systems in southern and eastern Europe, including Poland, provided stable and dry weather conditions. The simulation results were verified by analyzing synoptic maps of the study area. The image of the displacement of contaminated air masses obtained from the HYSPLIT model was found to be consistent with the synoptic maps, confirming the accuracy of the applied model. This means that the HYSPLIT model can be used to create maps of contaminant dispersion directions. Consequently, it was confirmed that modeling using the HYSPLIT model is an effective method for predicting the displacement directions of particulate contamination originating from coal combustion in a combined heat and power plant. Identifying circulation patterns and front zones during episodes of increased contaminant concentrations is strategic for effective weather monitoring, air quality management, and alerting the public to episodes of increased health risk in a large agglomeration.

Enhanced terahertz radiation directivity via a conical horn antenna from on-chip spintronic emitters.

A circular waveguide-fed conical horn antenna is fabricated using two-photon lithography (TPL) and integrated with a spintronic terahertz radiation emitter source to provide enhanced radiation directivity. In comparison to the bare terahertz radiation source, incorporating the antenna permits a spectral density gain up to 20.5 dB. The antenna has a smaller footprint and operates at higher frequencies than other reported conical horns, thereby demonstrating the potential of two-photon lithography for the fabrication of terahertz structures for on-chip applications. The use of two-photon lithography for the fabrication of terahertz antennas is anticipated to support the development of technologies operating above 1 THz for broadband, next-generation wireless free-space communications.

Identification of complex system radar emitter source based on one-dimensional convolutional neural network

Abstract With the continuous innovation of radar technology, the signal modulation of radar emitter sources has become more complex, which makes their identification face more challenges. We propose a method based on a one-dimensional convolutional neural network for the identification of complex system radar emitter sources and conduct an experiment on eight radar emitter sources with similar parameters and complex inter-pulse modulation. The identification accuracy reaches 88.24%.

Offset integrity reduces environmental risk: Using lessons from biodiversity and carbon offsetting to inform water quality offsetting in the catchments of the Great Barrier Reef

Environmental offsetting has been developed as a mechanism to facilitate the benefits from economic development while avoiding or minimizing environmental harm. This is achieved by compensating for environmental impacts at one location by generating equivalent environmental improvements elsewhere. However, experience with biodiversity and carbon offsetting indicates it can be difficult to ensure the integrity of offsets. Under recent legislation in the catchments of the Great Barrier Reef (GBR), Australia, it is mandatory for water quality emissions from new or expanded point source development to be offset by reducing pollution elsewhere, frequently through reducing non-point source pollution (NPSP). Therefore, informed by experience with biodiversity and carbon offsetting, we summarised sources of uncertainty in NPSP reduction that would influence water quality offset integrity; estimated the maximum potential demand for water quality offsets from sewage treatment plants, the largest point source emitter of total nitrogen (TN) in the GBR catchments, between 2018 and 2050; and discussed the implications of both on the ability of offsetting to counterbalance the impact of economic development in catchments where nitrogen loads have a large influence on the health of important GBR ecosystems. The catchments surrounding the population centres of Cairns and Mackay had both a potentially high future demand for nitrogen water quality offsets and nitrogen loads with a strong influence on the health of the GBR. Consequently, any low integrity water quality offsets in these catchments could jeopardise progress toward the water quality improvements needed to ensure the continued health of the GBR. Water quality offsetting has numerous strengths as a policy instrument however substantial uncertainties remain related to environmental outcomes. Until further research can reduce these uncertainties, water quality offsets that are implemented near increased point source emissions and have a high certainty of effectiveness may provide a balance between scientific rigour and policy workability.

Topologically influenced terahertz emission in Co2MnGa with a large anomalous Hall effect

The terahertz (THz) spectral zone is one of the most exciting but least explored domains of the electromagnetic spectrum. To extend the applicability of THz waves, the present objective is to develop an efficient, compact, durable, and low-cost THz emitter source. A spintronic THz emitter consisting of a ferromagnetic/nonmagnetic bilayer heterostructure is a promising innovation that can provide an alternative solution/replacement for conventional THz emitters. To further develop these spin-based THz emitters, we demonstrate an efficient and strong THz emission from a single layer of Co2MnGa with a large anomalous Hall effect (AHE) influenced by its Weyl semimetallic nature. Strong correlations among the THz emission, AHE, and chemical ordering of the full Heusler crystal structures for Co2MnGa are shown. Based on proper structural and chemical design, the topological nature of this material facilitates systematic optimization. Our initial findings provide a new design concept for the topological influences on spin-based THz emitters, and these emitters are expected to facilitate the further development of the intriguing Weyl physics.

All-optical source size and emittance measurements of laser-accelerated electron beams

Novel schemes for generating ultralow emittance electron beams have been developed in past years and promise compact particle sources with excellent beam quality suitable for future high-energy physics experiments and free-electron lasers. Recent theoretical work has proposed a laser-based method capable of resolving emittances in the sub 0.1 mm mrad regime by modulating the electron phase space ponderomotively. Here we present the first experimental demonstration of this scheme using a laser wakefield accelerator. The observed emittance and source size are consistent with published values. We also show calculations demonstrating that tight bounds on the upper limit for emittance and source size can be derived from the “laser-grating” method even in the presence of low signal to noise and uncertainty in laser-grating parameters. Published by the American Physical Society 2024

Time-of-flight estimation in acoustic pyrometry: sensitivity to pulse characteristics

Acoustic pyrometry is a non-intrusive measurement technique that may have several applications in turbomachinery. This methodology estimates the gas temperature by measuring the time of flight of an acoustic wave moving through a medium. It can be accomplished by placing a sound source (emitter) and a set of microphones (receivers) on opposite sides of a section. The emitter generates a sound pulse, and the receivers detect it. Since the emitter-receiver distances are known and fixed, the average temperatures of the paths traversed by the acoustic pulse can be computed by estimating the time-of-flight through deconvolution techniques. However, despite the straightforward principle, an acoustic wave suffers a variation of amplitude when propagating within a medium because of energy losses and ambient noise. Hence, time-of-flight estimation becomes a critical task, especially when considering high-frequency waves or short distances between sensors. It is then fundamental to select proper acoustic waves to maximise the cross-correlation between the signals of the emitter-receiver couples, thus improving the accuracy of the time-of-flight measurements and, consequently, the estimation of the spatial temperature distribution within a specific area. This study is a preliminary investigation, based on a modelling approach, to estimate the impact of different acoustic waves on the accuracy of the time-of-flight measurement. The results of this analysis will be useful to design and setup an acoustic pyrometry application.

Development of a Novel Spherical Light-Based Positioning Sensor in Solar Tracking.

Tracking of the sun, which increases the efficiency of solar energy production systems, has shown considerable development in recent years. This development has been achieved by custom-positioned light sensors, image cameras, sensorless chronological systems and intelligent controller supported systems or by synergetic use of these systems. This study contributes to this research area with a novel spherical-based sensor which measures spherical light source emittance and localizes the light source. This sensor was built by using miniature light sensors placed on a spherical shaped three-dimensional printed body with data acquisition electronic circuitry. Besides the developed sensor data acquisition embedded software, preprocessing and filtering processes were conducted on these measured data. In the study, the outputs of Moving Average, Savitzky-Golay, and Median filters were used for the localization of the light source. The center of gravity for each filter used was determined as a point, and the location of the light source was determined. The spherical sensor system obtained by this study is applicable for various solar tracking methods. The approach of the study also shows that this measurement system is applicable for obtaining the position of local light sources such as the ones placed on mobile or cooperative robots.

Development of CCUS clusters in Croatia

Carbon Capture and Storage is a concept that is not yet fully implemented largely because of the high costs. Clustering of industrial stakeholders is imposed as a measure for cost reduction. All relevant emitters, possible transport routes, including existing gas pipeline corridors, and their geographic location in relation to potential storage locations are assessed in this paper. Site availability and CO2 storage capacity are examined, summarizing all study results gathered under the Strategy CCUS project. The CO2 enhanced oil recovery is being studied for CO2 storage rather than extra oil recovery. As logical choices, three clusters were recognized. Only less expensive, onshore injection was taken in consideration for assessment of early (economic) feasibility in the Adriatic, Central, and Eastern clusters. Because of the shorter distance between CO2 emitters and injection sites, the Eastern and Central clusters are being investigated in more detail, despite the fact that the largest point source emitter is in the Adriatic region. Because of small number of point source CO2 emitters and huge theoretical storage capacity, further research is needed to better assess the storage capacities as well as possibilities for development of cross-border projects. Based on previous research (particularly regarding the emitters), the number of facilities (fewer facilities, with more concentrated emissions), and the availability of storage objects, the Eastern cluster is recommended to be further studied as the next stage of Carbon Capture, Utilization and Storage cluster research and development in Croatia and nearby cross-border regions.

The synchrotron radiation source PETRA III and its future ultra-low-emittance upgrade PETRA IV

PETRA III at DESY is one of the brightest synchrotron radiation sources worldwide. It serves a broad international multidisciplinary user community from academia to industry at currently 25 specialised beamlines. With a storage-ring energy of 6 GeV, it provides mainly hard to high-energy X-rays for versatile experiments in a very broad range of scientific fields. It is ideally suited for an upgrade to the ultra-low emittance source PETRA IV, owing to its large circumference of 2304 m. With a targeted storage ring emittance of 20 times 5,textrm{pm}^{2},textrm{rad}^{2}, PETRA IV will reach spectral brightnesses two to three orders of magnitude higher than today. The unique beam parameters will make PETRA IV the ultimate in situ 3D microscope for biological, chemical, and physical processes helping to address key questions in health, energy, mobility, information technology, and earth and environment.

Possibilities at the Polar beamline with APS-U

The Polar beamline will make use of the small emittance of the new APS-U storage ring and will offer extremely brilliant and coherent beam of variable polarization in the hard x-ray range. Tailored optics and experimental equipment will enable high spatial resolution dichroic spectroscopy, reflectivity and diffraction in combination with extreme pressures, low temperatures and high magnetic fields. Dichroic direct and ptychographic imaging of magnetic structures is being developed and will make use of the largely enhanced coherence of the low emittance source. We present an overview of the planned instrumentation and the upcoming new exciting possibilities.

Simulation study of a simultaneous beta–gamma-ray detection using a 3-layer phoswich detector and Monte Carlo methods

Combination of two or three dissimilar scintillator materials as a radiation detector has found major role in environmental radiation monitoring. In this paper, a three-layer Phoswich detector including BC-400, YAG, and CsI was designed to efficiently discriminate gamma-ray in the beta events up to 3.2 MeV using a simple rise-time discrimination method. MCNPX Monte Carlo code was used to obtain interaction probability of beta and gamma-rays as well as optimum thicknesses of the layers in the designing process. The optical transport of the system was simulated by GEANT4. In this regard, the pulses from simultaneous beta-gamma emitter sources were detected and discriminated based on pulse's rise-time so that the minimum number of gamma-ray contaminating events was observed in the beta spectrum. The results showed that using the proposed configuration and the method, output pulses with a rise-time shorter than 9 ns have been successfully detected as a beta particle while those with rising time longer than 15 ns have been identified as gamma-ray events. Overall results revealed that using the proposed system, an individual spectrum of beta particles or gamma-rays can be recorded from a simultaneous beta-gamma emitter source that minimizes contribution of the other radiation.

Comparative study on atomically heterogeneous surface with conical arrays of field emitters generated using plasma based low-energy ion beams

A comparative study of the field emission properties of conical arrays of atomically heterogeneous, self-organized, micro–submicro–nanodimensional structures, irradiated at normal incidence by high flux of 2 keV argon (flux=6.47×1015cm−2s−1) and krypton ions (flux=4.81×1015cm−2s−1) on copper substrates, without employing any external seeding, is presented. The variation in surface structural growths with ion beam fluence is investigated using scanning electron, atomic force, and transmission electron microscopy. The exposed surfaces are atomically heterogeneous due to the presence of embedded argon and krypton ions in the interstitial layers (≈nm) as observed from the x-ray photoelectron spectroscopy analysis. Kelvin probe force microscopy is employed to analyze the variation in local work function caused by surface deformities and implantation of inert gaseous ions. The conical arrays are naturally selected field emitter sources, and their field enhancement factor is calculated from the Fowler–Nordheim equations. The argon ion treated substrate at a fluence of 4.85×1018cm−2 gives rise to uniformly distributed structures and has a low turn-on voltage of 2.76 kV with an electron emission current of 0.58 nA. Among the krypton ion irradiated substrates, the sample irradiated at the highest fluence of 5.12×1018cm−2 produces self-organized conical arrays having uniform dimension, orientation, distribution, and even a higher electron emission current of 0.81 nA with a lower turn-on voltage of 2.12 kV. Thus, it may be concluded that krypton ion irradiation provides better generation of naturally selected arrays of field emitters.

Concurrent 8. Presentation for: Create a new carbon capture and storage (CCS) industry – unlock Australian CO

Presented on Tuesday 17 May: Session 8 Carbon capture and storage (CCS) is central to a clean energy transition. According to the UN’s IPCC and IEA, CCS needs to attain a global CO2 reduction capacity of ~4 billion tonnes per annum by 2050 to achieve Paris Agreement targets. To date, only 27 large-scale CCS facilities are operating worldwide, totalling 36.6 million tonnes per annum of CO2 reduction. Massive number of new projects are needed. Australia has a potential CO2 storage capacity of 434 billion tonnes, with 316 billion tonnes (73%) residing in offshore oil and gas fields and aquifers. A key constraint to unlock this potential is that the CO2 storage sites and emitter sources are not necessarily located close by. Since CCS projects considered to date in Australia use pipeline transportation, this limits the number of developments to those that have the emission sources and storage sites in proximity. By utilising the Floating CCS Hub development concept, which includes CO2 carriers and floating CCS hub facilities, CCS can be provided to a broader range of emission sources. The transportation cost using CO2 carriers is not as sensitive to transport distance as pipelines, which have a linear relationship between distance and cost. In addition, the CO2 carriers costs are reducing substantially as technology allows for CO2 to be transported in lower pressure states enabling larger parcel sizes, and manufacturing efficiencies further reducing costs. CO2 carriers and CCS hub facilities minimise development constraints related to pipeline distances and land use, and enable replicability and scalability for multiple CCS projects. To access the presentation click the link on the right. To read the full paper click here

Two-dimensional wavefront characterization of adaptable corrective optics and Kirkpatrick-Baez mirror system using ptychography.

Aberrations introduced during fabrication degrade the performance of X-ray optics and their ability to achieve diffraction limited focusing. Corrective optics can counteract these errors by introducing wavefront perturbations prior to the optic which cancel out the distortions. Here we demonstrate two-dimensional wavefront correction of an aberrated Kirkpatrick-Baez mirror pair using adaptable refractive structures. The resulting two-dimensional wavefront is measured using hard X-ray ptychography to recover the complex probe wavefield with high spatial resolution and model the optical performance under coherent conditions. The optical performance including the beam caustic, focal profile and wavefront error is examined before and after correction with both mirrors found to be diffraction limited after correcting. The results will be applicable to a wide variety of high numerical aperture X-ray optics aiming to achieve diffraction limited focussing using low emittance sources.

Create a new carbon capture and storage (CCS) industry – unlock Australian CO

Carbon capture and storage (CCS) is central to a clean energy transition. According to the UN’s IPCC and IEA, CCS needs to attain a global CO2 reduction capacity of ~4 billion tonnes per annum by 2050 to achieve Paris Agreement targets. To date, only 27 large-scale CCS facilities are operating worldwide, totalling 36.6 million tonnes per annum of CO2 reduction. Massive number of new projects are needed. Australia has a potential CO2 storage capacity of 434 billion tonnes, with 316 billion tonnes (73%) residing in offshore oil and gas fields and aquifers. A key constraint to unlock this potential is that the CO2 storage sites and emitter sources are not necessarily located close by. Since CCS projects considered to date in Australia use pipeline transportation, this limits the number of developments to those that have the emission sources and storage sites in proximity. By utilising the Floating CCS Hub development concept, which includes CO2 carriers and floating CCS hub facilities, CCS can be provided to a broader range of emission sources. The transportation cost using CO2 carriers is not as sensitive to transport distance as pipelines, which have a linear relationship between distance and cost. In addition, the CO2 carriers costs are reducing substantially as technology allows for CO2 to be transported in lower pressure states enabling larger parcel sizes, and manufacturing efficiencies further reducing costs. CO2 carriers and CCS hub facilities minimise development constraints related to pipeline distances and land use, and enable replicability and scalability for multiple CCS projects.

An Ultrasound-Guided Hemispherical Phased Array for Microbubble-Mediated Ultrasound Therapy.

To develop a low-cost magnetic resonance imaging (MRI)-free transcranial focused ultrasound (FUS) system for microbubble-mediated therapy. A 128-element 11 MHz array for skull localization was integrated within a 256-module multi-frequency (306/612/1224 kHz) dual-mode phased array. The system's transcranial transmit and receive performance was evaluated with ex-vivo human skullcaps using phase aberration corrections calculated from computed tomography (CT)-based simulations via ultrasound-based (USCT) and landmark-based (LMCT) registrations, and a gold-standard fixed source emitter (FSE)-based method. Displacement and rotation registration errors of 1.4 ± 0.4 mm and 2.1 ± 0.2 ° were obtained using USCT, resulting in sub-millimeter transmit targeting errors driven at 306 kHz (0.9 ± 0.2 mm) and 612 kHz (0.9 ± 0.3 mm), and source localization errors of 1.0 ± 0.3 mm and 0.6 ± 0.2 mm at receive frequencies of 306 kHz and 612 kHz, respectively (mean ± SD). Similar errors were obtained using LMCT and no significant differences between these two approaches were found on either transmit (p = 0.64/0.99) or receive (p = 0.45/0.36) at 306 kHz/612kHz. During volumetric multi-point exposures, approximately 70% and 60% of the transmit frames in which microbubble activity was detected via FSE were recovered using USCT when imaging at the second-harmonic and half-harmonic, respectively, compared to 60% and 69% using LMCT. This low-cost ultrasound-guided transcranial FUS system affords USCT skull registration with accuracy comparable to LMCT methods. Such systems have great potential to advance the adoption of microbubble-mediated FUS brain therapy by improving access to the technology.

Status and perspectives of the PETALO project

PETALO (Positron Emission Tof Apparatus with Liquid xenOn) is a novel concept for positron emission tomography scanners, which uses liquid xenon as a scintillation medium and silicon photomultipliers as a readout. The large scintillation yield and the fast scintillation time of liquid xenon, as well as its scalability, makes it an excellent candidate for PET scanners with time-of-flight measurements, especially for total-body machines. A first prototype of PETALO, devoted to demonstrate the potential of the concept, measuring the energy and time resolution and to test technical solutions for a complete ring is fully operational. The prototype consists of an aluminum box filled with liquid xenon, with two arrays of SiPMs on opposite sides facing the xenon. A β+ emitter source generating 511-keV pairs of gammas is placed in a central port and the SiPMs record the scintillation light produced by the gamma interactions, allowing for the reconstruction of the position, the energy and the time of the interactions.