Electron Source Research Articles

Exploring the Potential of a Thermionic LaB6 Virtual Source Mode Electron Gun for a High Angular Current Density and a Narrow Energy Distribution.

To date, lanthanum hexaboride (LaB6) thermionic electron sources have not been able fully to capitalize on their inherent potential, resulting in an ambiguous position within the application area. Although they exhibit higher brightness compared with a tungsten filament source, they still fall short of the performance of Schottky electron sources. This study aims to explore the capabilities of the LaB6 electron source under different operating conditions to bridge the gap, ultimately to realize its untapped potential. Simulations in virtual source mode indicated enhanced beam brightness and a reduced beam half-angle with an increase the extraction voltage, promising up to tenfold times higher beam brightness compared with the crossover mode. The energy distribution measured using a prelens retarding field energy analyzer revealed an energy distribution of 0.55 eV and a high angular current density of 33 mA/sr in the virtual source mode. Therefore, the virtual source mode of LaB6 can provide a narrow energy distribution akin to that of a ZrO/W Schottky electron gun (1600 K) while having an angular current density over 2,000 times higher. In addition, the stability of the virtual source mode is ±0.022%, while that of the crossover mode is ±0.138%.

FACTORS ASSOCIATED WITH UNDERGRADUATE STUDENTS’ SUBJECT SELECTION IN BANGLADESH

Subject selection is a critical decision for undergraduate students as it has a significant impact on their personal development and future careers. A mixed method approach was used to investigate the decision-making process and the factors that influence subject selection of undergraduate students at Khulna University. Quantitative data were collected from 300 participants using an online survey questionnaire, and qualitative data was gathered from four focus group discussions. The study found that in selecting academic subjects, students typically go through nine steps: identifying desire subjects; anxiety about desired subjects; seeking information from sources; assessing the influence of sources; comparing and depending on sources; understanding own motivations; comparison between subjects; making a decision; and conducting post-decision evaluations. The quantitative results show that family members and teachers were the most influential factors in choosing academic subjects. Additionally, students mentioned that they relied on a variety of human and electronic sources to gather information during their decision-making process. They relied on human sources like senior students and friends for better understanding regarding future career of a subject. They also used electronic sources like Google search, social media, and university websites in enhancing their information-gathering process. The qualitative findings suggest that in the process of selecting major students often experience mental stress due to a lack of information about desired subjects, challenges in getting preferred subject, and the pressure from families to take their preferred subject. The study offers a systematic understanding of the factors and decision-makers that shape the subject selection process of undergraduate students.

Subcycle surface electron emission driven by strong-field terahertz waveforms

The advent of intense terahertz (THz) sources opened a new era when the demonstration of the acceleration and manipulation of free electrons by THz pulses became within reach. THz-field-driven electron emission was predicted to be confined to a single burst due to the single-cycle waveform. Here we demonstrate the confinement of single-cycle THz-waveform-driven electron emission to one of the two half cycles from a solid surface emitter. Either the leading or the trailing half cycle was active, controlled by reversing the field polarity. THz-driven single-burst surface electron emission sources, which do not rely on field-enhancement structures, will impact the development of THz-powered electron acceleration and manipulation devices, all-THz compact electron sources, THz waveguides and telecommunication, THz-field-based measurement techniques and solid-state devices.

Music Therapy as a Collaborative Tool in the Recovery of Substance Use Disorder (SUD) Patients

Music is considered worldwide as both a verbal and non-verbal tool because it influences an individual’s emotions, positively impacting their mood, individuality, and self-confidence, among other aspects. In the context of pharmacological treatments for substance dependence, the practices of Music Therapy are included and are considered a valuable tool to assist in the recovery of these patients. Music provides emotional and mental support during the detoxification and withdrawal processes experienced by individuals who develop substance-induced disorders. It is a complementary therapy that helps the patient express themselves, contributing to improvements in the sensory and motor experiences of the participants. In other words, it allows the individual’s subjectivity to re-emerge, enabling them to reconnect with themselves and with society. The literature demonstrates that drug addiction is a millennia-old phenomenon that affected approximately 11.2 million people around the world in 2020. Additionally, there has been an increase in consumption among young people, with rates growing by 26% compared to those recorded in 2012. This review article, prepared using the bibliographic research technique, aims to demonstrate the effectiveness of Music Therapy in the treatment and support of patients with substance use disorders. Based on the literature selected from electronic sources, it was found that Music Therapy, as an additional treatment alongside pharmacological approaches, significantly contributes to the recovery of individuals with substance-induced disorders.

Boosting Oxygen Reduction through Microenvironment Modulation to Enhance Mass Transportation

Electroreduction of oxygen driven by renewable electricity holds significant promise for the sustainable production of value‐added hydrogen peroxide (H2O2). While water is a desirable source of protons and electrons for this reaction, its low gas solubility often limits the transportation of gas molecules and consequently leads to large concentration overpotential, resulting in unsatisfactory energy efficiencies. Herein, a facile and effective strategy to promote the 2e− oxygen reduction reaction (ORR) through microenvironment modulation is presented. In this work, it is specifically aimed to facilitate oxygen transportation at the reaction interface, particularly at high rates. To achieve this, hydrophobic polytetrafluoroethylene (PTFE) particles are introduced into a catalyst layer containing amino‐group‐functionalized carbon nanotube (CNT‐NH2) as the ORR catalyst for H2O2 production. As a result, the PTFE‐modified CNT‐NH2‐based gas‐diffusion electrode (GDE) substantially improves ORR activity. At 100 mA cm−2, the PTFE‐modified CNT‐NH2 achieves a high cathodic energy efficiency of 92%, 1.5 times higher than the pristine CNT‐NH2‐based GDE (63%). Detailed kinetic analysis reveals that this enhanced ORR performance is indeed due to the enhanced oxygen transportation induced by the persistent hydrophobic microenvironment created by the PTFE‐modified catalyst layer, reducing the concentration overpotential during ORR.

Comparison of calibration coefficients for a vinten ionization chamber simulated using four Monte Carlo methods

The Vinten 671 ionization chamber (VIC) was modelled using Monte Carlo (MC) programs EGSnrc, Penelope, and TOPAS. Several national measurement institutes have VICs with well-characterized response relationships and have measured calibration coefficients for many radionuclides. Twelve radionuclides with various decay emissions were assessed as well as 14 monoenergetic photon sources and 10 monoenergetic electron sources. Calibration coefficients were calculated based on the energy deposited in the simulated VIC nitrogen gas volume and compared to experimental values from the literature.

Coherent ultrafast photoemission from a single quantized state of a one-dimensional emitter.

Femtosecond laser-driven photoemission source provides an unprecedented femtosecond-resolved electron probe not only for atomic-scale ultrafast characterization but also for free-electron radiation sources. However, for conventional metallic electron source, intense lasers may induce a considerable broadening of emitting energy level, which results in large energy spread (>600 milli-electron volts) and thus limits the spatiotemporal resolution of electron probe. Here, we demonstrate the coherent ultrafast photoemission from a single quantized energy level of a carbon nanotube. Its one-dimensional body can provide a sharp quantized electronic excited state, while its zero-dimensional tip can provide a quantized energy level act as a narrow photoemission channel. Coherent resonant tunneling electron emission is evidenced by a negative differential resistance effect and a field-driven Stark splitting effect. The estimated energy spread is ~57 milli-electron volts, which suggests that the proposed carbon nanotube electron source may promote electron probe simultaneously with subangstrom spatial resolution and femtosecond temporal resolution.

Assessment of Knowledge and attitude towards Stroke among the UAE population during the COVID-19 pandemic: A cross-sectional study.

Background: Despite significant advancements in healthcare, the burden of stroke continues to rise in the developed world, especially during the COVID-19 pandemic. Association between COVID-19 infection and stroke is well established. Factors identified for the delay in presentation and management include a lack of awareness regarding stroke. We aimed to assess the general public knowledge and attitudes on stroke and stroke risk factors in the United Arab Emirates during the COVID-19 pandemic. Methods: A cross-sectional study was conducted between September 2021 and January 2022 among adults≥ 18 years old. Participants completed a self-administered questionnaire on sociodemographic characteristics and stroke knowledge and attitudes. Knowledge and attitude scores were calculated based on the number of correct responses. Linear regression analysis was performed to determine the factors related to knowledge and attitude towards stroke. Results: Of the 500 respondents, 69.4% were females, 53.4% were aged between 18 and 25, and nearly half were students (48.4%). The mean knowledge score was 13.66 (range 2-24). Hypertension (69%), smoking (63.2%), stress (56.4%) obesity/overweight (54.4%), and heart disease (53.6%) were identified as risk factors. Overall, the knowledge of signs/symptoms was suboptimal. The mean attitude score was 4.41 (range, 1-6); 70.2% would call an ambulance if someone were having a stroke. A monthly income of 11,000-50,000 AED and being a student were associated with positive knowledge. Being a non-health worker and lacking access to electronic media sources were associated with worse attitudes. Conclusion: Overall, we identified poor knowledge and suboptimal attitudes toward stroke. These findings reflect the need for effective public health approaches to improve stroke awareness, knowledge, and attitudes for effective prevention in the community. Presently, this is of utmost necessity, given the increased occurrence of stroke and its severity among COVID-19 patients.

Construction of sp2/sp3 Hybrid Carbon Thin Layers on Silicon Substrates Using Nonequilibrium Excitation Reaction Fields.

The authors have developed a crystal growth process that utilizes electron beams from field emission (FE) to grow materials bottom-up by a method other than the transfer of thermal energy. In this study, highly crystalline single-walled carbon nanotubes were used as a field emission electron source. Electron beams with high resolution energy emitted from the source were irradiated onto acetylene gas as a nonequilibrium reaction field to induce acetylene dissociation. The generated carbon ions were then irradiated onto a [100] silicon substrate, resulting in the irradiation of the silicon substrate surface with graphene. Moreover, the crystal growth of sp2/sp3 hybrid carbon thin layers, which is different from the crystal structures of graphite, diamond, and diamond-like carbon, proceeded on the surface of the silicon substrate. Carbon layers on periodic crystal structures whose growth depends at least on the morphology of the substrate are formed through bridging with the binding site of the substrate. The authors have succeeded in developing a nonthermal technique of crystal bridging between different elements. The substrate on which the carbon layer is formed is not limited to silicon; other substrates with various crystal structures and periodicities are expected to be used.

Characterization of a circular arc electron source for a self-neutralizing air-breathing plasma thruster

The paper presents an enhanced version of an arc electron source designed for air ionization applications in a self-neutralizing air-breathing plasma thruster. The arc electron source is specifically suited for the air-breathing plasma thruster, as it allows precise control of mean electron energy levels. This paper focuses on the ionization aspects of air-breathing thrusters through the development of axially magnetized arc electron sources. The sources consist of a circular and coaxial configuration of a metallic arc plasma source coupled with a positively biased grid to extract electrons and control mean electron energy. The average mean electron energy of electrons in the arc electron source is regulated by adjusting the bias voltage of the grid within the range of 0 V – 300 V. To investigate the behavior of ion current density and electron density concerning pressure and mean electron energy, the current probe and magnetic filter were utilized. It was demonstrated that the circular electron source leads to enhanced ionization of airflow by achieving plasma densities greater than 1018 m−3. By utilizing a high-speed camera for the circular arc electron source, the arc spot was seen to move azimuthally due to the magnetic field. Furthermore, scanning electron microscopy and a conductance measurement system were employed for the coaxial arc electron source to examine the deposition and conductance of the electron extraction grid. While the grid underwent deposition of about 600 microns, the conductance was observed to increase/saturate with time and bias voltage, indicating an electrically “self-healing material”.

A coupled piezo-triboelectric nanogenerator based on the electrification of biaxially oriented polyethylene terephthalate food packaging films

This study reports that biaxially oriented silica-filled polyethylene terephthalate (BOPET) films used worldwide as food packaging materials combine unique dual electrification properties that enable the effective conversion of mechanical energy into electricity. The electricity output depends on the physical contact and separation of the polymeric matrix and triboelectric pair material with different affinities for electrons on its surface. To exploit the dual piezoelectric and triboelectric electrification of the films materials, a hybrid piezoelectric triboelectric nanogenerator energy harvester using this film as an electron source was assembled and tested. When BOPET film is paired with polyvinylidene fluoride (PVDF) nanofibre network, which due to the electronegativity difference gained electrons, the performance of the nanogenerator to the output open-circuit increases voltage values above 305 V, and the short-circuit current density and charge density to 12 ± 1μAcm−2 and 37 ± 2μCm−2, respectively. Further, underlaying the PVDF tribo-contact layer by a dielectric low permittivity spunbond non-woven polypropylene raises the performance of the nanogenerator more than doubled (624 V) with corresponding densities of 61 ± 7μAcm−2 and 101 ± 4μCm−2.

The study of channeled vacuum GaAs photocathodes for enhanced electron emission properties

In this paper, we design and analyze the channeled vacuum photocathodes with novel structures towards low operating temperature, high current density, and miniaturized cathode electron sources. We simulate the characteristics of the electron emission of the channeled vacuum GaAs photocathodes in detail with the commercial CST software. Simulation results indicate that the emission current of the photocathode can increase with the optimal gate and anode voltage choices, and the emission efficiency can reach up to 63.4 %. Using this optimized structure as the benchmark, the quantum efficiency and emission efficiency are also investigated. Furthermore, we have altered the channel morphology, i.e., with the curved vacuum channel structures, to enhance the current density. We have found that the emission current density can increase significantly and reach up to 2.68 times of the regular rectangular channel. The simulation results can lay the foundation for the development of new type of micro-structured GaAs photocathodes.

Flat ball topology basics multi‐transceivers 100 km/2.5 Tbps gigabit‐ethernet PON architecture for energy efficiency in data centers

AbstractExisting electronic data sources desire high‐power requisites, in order to obtain a large bandwidth, minimum power dissipation and low latency in networks. In this instance, a gigabit ethernet passive optical network (GEPON) architecture based on a dynamic Flat Ball topology incorporating multi‐transceivers to minimize network energy consumption via passive devices along with bandwidth reconfiguration potential and low latency is reported in this paper. The proposed architecture connected with 200 nodes exhibits 26 as well as 40 dB total loss in uplink as well as downlink considerably, compared to Sirius and Sandwich tree. Also, Flat ball GEPON architecture permits 9 and 10 dBm energy saving in downlink as well as uplink, respectively, than conventional GEPON architecture at 1 ms delay. The proposed architecture with 50 Erlang load allows energy ratio of 39% in downlink and 37% in uplink, at 25 × 100 Gbps traffic rate for 55 nodes. Besides this, the faithful fiber range of 100 km considering fiber no‐linearities and impairments can be obtained successfully. The architecture can be bordered with 1:64 splitting ratio with 35 ms in downlink as well as 31 ms in uplink transmission delay at bit error rate of 10−3. Additionally, on comparing the proposed topology with existing architectures depict its superiority with minimal implementation cost, low‐power dissipation, less traffic delay as well as high scalability and high flexibility.

Serpentinization as the source of energy, electrons, organics, catalysts, nutrients and pH gradients for the origin of LUCA and life.

Serpentinization in hydrothermal vents is central to some autotrophic theories for the origin of life because it generates compartments, reductants, catalysts and gradients. During the process of serpentinization, water circulates through hydrothermal systems in the crust where it oxidizes Fe (II) in ultramafic minerals to generate Fe (III) minerals and H2. Molecular hydrogen can, in turn, serve as a freely diffusible source of electrons for the reduction of CO2 to organic compounds, provided that suitable catalysts are present. Using catalysts that are naturally synthesized in hydrothermal vents during serpentinization H2 reduces CO2 to formate, acetate, pyruvate, and methane. These compounds represent the backbone of microbial carbon and energy metabolism in acetogens and methanogens, strictly anaerobic chemolithoautotrophs that use the acetyl-CoA pathway of CO2 fixation and that inhabit serpentinizing environments today. Serpentinization generates reduced carbon, nitrogen and - as newer findings suggest - reduced phosphorous compounds that were likely conducive to the origins process. In addition, it gives rise to inorganic microcompartments and proton gradients of the right polarity and of sufficient magnitude to support chemiosmotic ATP synthesis by the rotor-stator ATP synthase. This would help to explain why the principle of chemiosmotic energy harnessing is more conserved (older) than the machinery to generate ion gradients via pumping coupled to exergonic chemical reactions, which in the case of acetogens and methanogens involve H2-dependent CO2 reduction. Serpentinizing systems exist in terrestrial and deep ocean environments. On the early Earth they were probably more abundant than today. There is evidence that serpentinization once occurred on Mars and is likely still occurring on Saturn's icy moon Enceladus, providing a perspective on serpentinization as a source of reductants, catalysts and chemical disequilibrium for life on other worlds.

Design, manufacturing, evaluation, and performance of a 3D-printed, custom-made nozzle for laser wakefield acceleration experiments.

Laser WakeField Acceleration (LWFA) is extensively used as a high-energy electron source, with electrons achieving energies up to the GeV level. The produced electron beam characteristics depend strongly on the gas density profile. When the gaseous target is a gas jet, the gas density profile is affected by parameters, such as the nozzle geometry, the gas used, and the backing pressure applied to the gas valve. An electron source based on the LWFA mechanism has recently been developed at the Institute of Plasma Physics and Lasers. To improve controllability over the electron source, we developed a set of 3D-printed nozzles suitable for creating different gas density profiles according to the experimental necessities. Here, we present a study of the design, manufacturing, evaluation, and performance of a 3D-printed nozzle intended for LWFA experiments.

Protection for AC transmission line between DFIG wind farm and MMC station

The characteristics of power electronic controlled sources are reflected at both ends of the AC line applied to the integration of long-distance wind farms into the MMC-HVDC converter station, and the fault characteristics of the system have undergone fundamental changes. For the doubly-fed wind power AC transmission line with a modular multilevel converter, the short-circuit current characteristics provided by the power supply at both ends of the line lead to the inadaptability of longitudinal differential protection. In view of the significant difference in the complexity of the short-circuit current component provided by the doubly-fed wind power and the converter at both ends of the AC transmission line, a line pilot protection idea based on the complexity of the current component is proposed. The complexity of the current component is characterized by singular entropy theory, and then the singular entropy algorithm and its scheme for pilot protection are constructed. A refined electromagnetic transient model of MMC-HVDC for doubly-fed wind farms is built in PSCAD for simulation verification. The simulation results show that the proposed method can quickly and reliably identify various types of internal and external faults, and solve the problem of incorrect action of traditional protection in this scenario. In addition, the scheme is not affected by fault type, location, or transition resistance.

Ambient greenness, access to local green spaces, and subsequent mental health: a 10-year longitudinal dynamic panel study of 2·3 million adults in Wales

Living in greener areas, or close to green and blue spaces (GBS; eg, parks, lakes, or beaches), is associated with better mental health, but longitudinal evidence when GBS exposures precede outcomes is less available. We aimed to analyse the effect of living in or moving to areas with more green space or better access to GBS on subsequent adult mental health over time, while explicitly considering health inequalities. A cohort of the people in Wales, UK (≥16 years; n=2 341 591) was constructed from electronic health record data sources from Jan 1, 2008 to Oct 31, 2019, comprising 19 141 896 person-years of follow-up. Household ambient greenness (Enhanced Vegetation Index [EVI]), access to GBS (counts, distance to nearest), and common mental health disorders (CMD, based on a validated algorithm combining current diagnoses or symptoms of anxiety or depression [treated or untreated in the preceding 1-year period], or treatment of historical diagnoses from before the current cohort [up to 8 years previously, to 2000], where diagnosis preceded treatment) were record-linked. Cumulative exposure values were created for each adult, censoring for CMD, migration out of Wales, death, or end of cohort. Exposure and CMD associations were evaluated using multivariate logistic regression, stratified by area-level deprivation. After adjustment, exposure to greater ambient greenness over time (+0·1 increased EVI on a 0-1 scale) was associated with lower odds of subsequent CMD (adjusted odds ratio 0·80, 95% CI 0·80-0·81), where CMD was based on a combination of current diagnoses or symptoms (treated or untreated in the preceding 1-year period), or treatments. Ten percentile points more access to GBS was associated with lower odds of a later CMD (0·93, 0·93-0·93). Every additional 360 m to the nearest GBS was associated with higher odds of CMD (1·05, 1·04-1·05). We found that positive effects of GBS on mental health appeared to be greater in more deprived quintiles. Ambient exposure is associated with the greatest reduced risk of CMD, particularly for those who live in deprived communities. These findings support authorities responsible for GBS, who are attempting to engage planners and policy makers, to ensure GBS meets residents' needs. National Institute for Health and Care Research Public Health Research programme.

Circus Arts in Content Service Systems

The aim of this paper is to identify scientific content and compilations related to circus arts available in subscription databases and in renowned and free academic information systems. After providing terminological definitions for circus and circus arts, the article describes the search strategies applied and the issues which emerged during the searches, and then introduces quantitative results, thereby also identifying the major periodicals and the most often referenced articles of the topic. The analysis provides useful input for representatives of other arts related to circus arts (e.g., performing arts, theatre arts, visual arts, musical arts) and of other academic fields (e.g., literary studies, history, media science); but first of all, it serves as an unparalleled library information service guide for navigating between electronic information sources.

Optical measurement of the work function and the field reduction factor of metallic needle tips.

Quintessential parameters for needle tip-based electron sources are the work function, the tip apex radius, and the field reduction factor. They determine the static emission properties and strongly influence laser-triggered photoemission experiments at these needle tips. We present a simple method based on photoemission with two different commonly available continuous-wave laser diodes to determine both parameters in situ. We demonstrate our technique at tungsten needle tips. In a first application, use the method to in situ monitor changes of the emitter caused by illumination with strong femtosecond laser pulses. After illumination, we observe an increase in the work function caused by laser-induced changes to the apex of the tip. These changes are reversible upon field evaporation and are accompanied by a change in the spatial electron emission distribution. We believe that this simple in situ work function determination technique is applicable to any metal and in many experimental settings.

Atomically smooth films of CsSb: A chemically robust visible light photocathode

Alkali antimonide semiconductor photocathodes provide a promising platform for the generation of high-brightness electron beams, which are necessary for the development of cutting-edge probes, including x-ray free electron lasers and ultrafast electron diffraction. Nonetheless, to harness the intrinsic brightness limits in these compounds, extrinsic degrading factors, including surface roughness and contamination, must be overcome. By exploring the growth of CsxSb thin films monitored by in situ electron diffraction, the conditions to reproducibly synthesize atomically smooth films of CsSb on 3C–SiC (100) and graphene-coated TiO2 (110) substrates are identified, and detailed structural, morphological, and electronic characterization is presented. These films combine high quantum efficiency in the visible (up to 1.2% at 400 nm), an easily accessible photoemission threshold of 566 nm, low surface roughness (down to 600 pm on a 1 μm scale), and a robustness against oxidation up to 15 times greater than Cs3Sb. These properties lead us to suggest that CsSb has the potential to operate as an alternative to Cs3Sb in electron source applications where the demands of the vacuum environment might otherwise preclude the use of traditional alkali antimonides.