Beam Source Research Articles

Multiscale characterization of polymer electrolyte fuel cells elucidated by quantum beam analysis

Abstract Polymer electrolyte fuel cells (PEFCs) offer promising alternatives to conventional gasoline engines in automobiles and have been commercialized over the past decade. This progress can be attributed to state-of-the-art materials with high performance, long-term durability, and robust manufacturing technologies. The multiscale hierarchical structure inherent in PEFCs facilitates the transfer of protons, electrons, oxygen, and water. As various phenomena in PEFCs occur at different scales, multiscale analysis, including quantum beam analysis, is of great interest for materials development and for understanding the processes that take place in PEFCs. In particular, advancements in this field have enabled the further tailoring of properties in a controlled manner and the design of nanostructures processing superior material properties. Additionally, the expansion of quantum beam sources has facilitated the study of manufacturing protocols. This review presents the achievements in the use of synchrotron x-ray and neutron sources in the field of PEFCs, while also addressing remaining issues for the widespread commercialization of fuel cell electric vehicles.

Study of Lighting Design for Interior Spaces

Due to the continuous progress of lighting fixture technology, people's requirements for commercial space design are also rising, and the comfortable, convenient, artistic, and technological combination of space is more and more emphasized by designers. The author has collected a large amount of visual subjective evaluation data through actual investigation and experimentation and conducted extensive and in-depth research on the light source's low radiation, luminous flux, luminous intensity, illuminance, luminance, color temperature, color deviation, color tolerance, beam angle, and maintenance coefficient. This paper takes the lighting quality parameters as the benchmark, analyzes the formal aesthetic relationship between commercial space and lighting design, and has a certain reference value for both lighting workers and academic research.

A study of hollow-cathode electron beam source surface flashover discharge and suppression

As surface flashover discharge limits the performance of hollow-cathode electron beam sources, this work systematically investigates the surface flashover discharge in the hollow-cathode discharge process based on electrostatic field simulations. Experimental research is conducted on designing and investigating hollow cathode discharge cavities featuring structures to prevent surface flashover, both single- and multi-gap. Theoretical analysis found that the vacuum surface flashover discharge will cause an abnormal breakdown phenomenon along the wall of the insulating sleeve. The surface flashover, once formed, would develop dramatically, thus suppressing the formation of hollow-cathode discharge and becoming the main form of discharge. To eliminate the abnormal flashover breakdown, an effective suppression structure is designed regarding the triple point of the surface flashover. Through the special design, the triple points in the corners are always hidden by recessing the corner of the insulator in a notch. Moreover, corrugated structures along the insulating surface are studied, and the proper rectangular slots are designed in the inner insulating surface. The experimental results also indicate that after adopting the insulation scheme, the breakdown voltage of the discharge cavity and its working stability are greatly improved.

Correlation of source parameters and beam properties in the early operation of the full size ITER negative ion beam source

One of the requirements of Heating and current drive Neutral Beam injectors for ITER is a beam homogeneity greater than 90%, to achieve an optimal beam transmission while keeping the heat load consistently low on the acceleration electrodes. The large size and complexity of ITER negative ion source play a key role in determining the homogeneity of the negative ion current of each of the 1280 beamlets and their divergence, and it is studied in the full-scale prototype source SPIDER. In this work the plasma properties are studied by spectroscopic and electrostatic measurements in the drivers, where the plasma is generated, and in the expansion region, where the plasma drifts and negative ions are produced, and they are correlated with the properties of the beam. The non-homogeneous plasma density profile is related to the non-homogeneous availability of negative ions along the beam vertical profile, with and without cesium evaporation. Visible tomography, a technique capable of characterizing isolated beamlet properties, is used to study the beam’s dependence on plasma uniformity along the entire beam profile. Using these tools, it has been demonstrated how an increase in plasma density is linked to an improvement in beam homogeneity. The latter has been directly correlated with plasma homogeneity. The magnetic filter field and biases of the plasma grid and bias plate are responsible for the variation in plasma density and its homogeneity. Non-uniformities in the plasma’s top/bottom and left/right distributions have been studied and partially addressed experimentally. The first issue was resolved by adjusting the radio-frequency power supplied to the plasma in different vertical regions, while the second issue was addressed by reversing the direction of the magnetic filter field and increasing the plasma density.

A study of pulsed high voltage driven hollow-cathode electron beam sources through synchronous optical trigger

In this study, a pulsed, high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure, low cost, and easy triggering. To validate the new design, the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details, respectively. The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge, which provides a new solution for the realization of a high-frequency, high-energy electron beam source. The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A, which indicates the pulsed power mode significantly improves the electron beam performance. Besides, increasing the capacitance significantly affects the high-current, lower-energy electron beam more than the high-energy electron beam.

Prime number factorization with light beams carrying orbital angular momentum

We point out a link between orbital angular momentum (OAM) carrying light beams and number theory. The established link makes it possible to formulate and implement a simple and ultrafast protocol for prime number factorization by employing OAM endowed beams that are modulated by a prime number sieve. We are able to differentiate factors from non-factors of a number by simply measuring the on-axis intensity of light in the rear focal plane of a thin lens focusing on a source beam. The proposed protocol solely relies on the periodicity of the OAM phase distribution, and hence, it is applicable to fully as well as partially coherent fields of any frequency and physical nature—from optical or x-ray to matter waves—endowed with OAM. Our experimental results are in excellent agreement with our theory. We anticipate that our protocol will trigger new developments in optical cryptography and information processing with OAM beams.

Generation Mechanism and Beaming of Jovian nKOM From 3D Numerical Modeling of Juno/Waves Observations

AbstractThe narrowband kilometric radiation (nKOM) is a Jovian low‐frequency radio component identified as a plasma emission produced in the region of the Io plasma torus. Measurements from the Waves instrument onboard the Juno spacecraft permitted to establish the distribution of nKOM occurrence and intensity as a function of frequency and latitude. We have developed a 3D geometrical model that can simulate at large scale the plasma emissions occurrence observed by a spacecraft based on an internal Jovian magnetic field model and a diffusive equilibrium model of the plasma density in Jupiter's inner magnetosphere. With this model, we propose a new method to discriminate the generation mechanism, wave mode, beaming and radio source location of plasma emissions. Here, this method is applied to the study of the nKOM observed from all latitudes by the Juno/Waves experiment to identify which conditions reasonably reproduce the observed occurrence distribution versus frequency and latitude. The results allow us to exclude the two main nKOM models published so far, and to show that the emission is produced at the local plasma frequency and then beamed anti‐parallel to the local density gradient into free space. We also propose that depending on its latitude, Juno observes two distinct kinds of nKOM: the low frequency nKOM in ordinary mode at high latitudes, and the high frequency nKOM on extraordinary mode at low latitudes. Both radio source locations are found to be distributed near the centrifugal equator ranging from the outer edge to the inner edge of the Io plasma torus.

A tool for beam optics design and its application on the VEGA transport line at ELI-NP

The Variable Energy Gamma (VEGA) System, currently under construction at Extreme Light Infrastructure-Nuclear Physics (ELI-NP), is a storage ring-based gamma beam source that aims to provide gamma-ray beams with a variable energy range from 1 MeV to 19.5 MeV to the users. The electron beam transport line has been designed to connect the linear accelerator and the storage ring in the VEGA electron beam system. Considering the geometrical constraints in the accelerator halls and the location of the injection point at the storage ring, the trajectory of the electron beam in the transport line has to first ascend by a 36-degree dog-leg elevation to align with a plane parallel to the storage ring, undergo a 180-degree horizontal turn, and then descend by 36 degrees vertically to reach the injection point at the storage ring. In this paper, we introduce a beam optics tool implemented for the beam optics design and fine-matching in the electron beam transport line. The design of the VEGA transport line including the layout and lattice design, is also described. The tool has been applied to the beam optics design and optimization, utilizing tracking simulations and beam matching for the VEGA transport line lattice. Furthermore, the tool's potential application to similar lattice designs is also discussed.

Synthesis of Robust Full Poincaré Polarization States via Spatial Coherence Engineering

The full Poincaré (FP) beam, encompassing all possible polarization states in its beam cross-section, has demonstrated advantages in various applications. However, conventional FP beams are typically considered as spatially fully coherent, rendering them sensitive to disturbances in the propagation path and susceptible to speckle effects. In this work, we propose an alternative approach to synthesize the optical beam with a FP polarization state through the spatial coherence engineering of a partially coherent beam. In this process, the FP polarization state is initially encoded into the spatial coherence structure of the beam source. We demonstrate that during the encoding process, the vector nature of the beam transitions from the FP polarization state to the spatial coherence structure of the source. However, during the propagation of the partially coherent beam, the vectorness reverts to the polarization state, resulting in the re-emergence of the encoded FP polarization in the output plane. We illustrate that the synthesized FP polarization state, achieved through spatial coherence engineering, is highly robust against obstructions in the propagation path. Furthermore, we examine the effect of the spatial coherence area of the beam on the quality of the recovered FP polarization state. The findings of this work can have valuable applications in optical trapping and optical imaging in complex environments.

Degree of paraxiality of radially polarized twisted multi-Gaussian Schell-model beams.

The degree of paraxiality (DOP) of a radially polarized twisted multi-Gaussian Schell-model (RPT MGSM) beam is discussed, and the influence of the source parameters on its DOP is studied. It is shown that the parameters of the beam source, including the boundary characteristic, the beam waist width, the coherence width of the source correlation, and the twist factor, have a significant impact on the DOP of the RPT MGSM beam. To explain the behaviors of the DOP, the far-field divergence angle of this beam is also discussed.

Direct Observation of Sub-Poissonian Temporal Statistics in a Continuous Free-Electron Beam with Subpicosecond Resolution.

We present a novel method to measure the arrival time statistics of continuous electron beams with subpicosecond resolution, based on the combination of an rf deflection cavity and fast single electron imaging. We observe Poissonian statistics within time bins from 100 to 2ns and increasingly pronounced sub-Poissonian statistics as the time bin decreases from 2ps to 340fs. This 2D streak camera, in principle, enables femtosecond-level arrival time measurements, paving the way to observing Pauli blocking effects in electron beams and thus serving as an essential diagnostic tool toward degenerate electron beam sources for free-electron quantum optics.

Optical force propelled by metamaterial surface waves excitation: pushing and tractor beam sources

Theoretical research on opto–mechanical interactions at sub–wavelength levels using surface waves (SWs) excitation has a great impact in both the academic knowledge and practical realm. In this letter we have revealed that the dynamic characteristics of the SWs excited along a metamaterial boundary, such as its forward or backward propagation nature, provide a direct demonstration about the direction of action of the optical force exerted on a dielectric nano–particle. In particular, by using a rigorous electromagnetic formalism based in the second Green identity, we have modeled the scattering problem of a Gaussian beam impinging on a metamaterial plane surface with a sub–wavelength localized defect. We have shown that depending on the nature of the excited SW, dielectric nano–particles placed near the surface can be pushed away or towards the localized defect. We believe that this work unveils the potential implementation of sub–wavelength defects as sources of pushing or pulling optical forces.

Gas gains over 104 and optimisation using 55Fe X-rays in low pressure SF6 with a novel Multi-Mesh ThGEM for directional dark matter searches

The Negative Ion Drift (NID) gas SF6 has favourable properties for track reconstruction in directional Dark Matter (DM) searches utilising low pressure gaseous Time Projection Chambers (TPCs). However, the electronegative nature of the gas means that it is more difficult to achieve significant gas gains with regular Thick Gaseous Electron Multipliers (ThGEMs). Typically, the maximum attainable gas gain in SF6 and other Negative Ion (NI) gas mixtures, previously achieved with an 55Fe X-ray source or electron beam, is on the order of 103 [1,2,3,4]; whereas electron drift gases like CF4 and similar mixtures are readily capable of reaching gas gains on the order of 104 or greater [5,9,7,8,6]. In this paper, a novel two stage Multi-Mesh ThGEM (MMThGEM) structure is presented. The MMThGEM was used to amplify charge liberated by an 55Fe X-ray source in 40 Torr of SF6. By expanding on previously demonstrated results [10], the device was pushed to its sparking limit and stable gas gains up to ˜50000 were observed. The device was further optimised by varying the field strengths of both the collection and transfer regions in isolation. Following this optimisation procedure, the device was able to produce a maximum stable gas gain of ˜90000. These results demonstrate an order of magnitude improvement in gain with the NID gas over previously reported values and ultimately benefits the sensitivity of a NITPC to low energy recoils in the context of a directional DM search.

In Situ Synchrotron Investigations of Beam Diameter Influence on Vapor Capillary Formation during Laser Beam Welding of Copper Alloy with a Blue Laser Beam Source

Laser beam welding as a reliable tool for high-precision joining of batteries or microelectronics is more and more the choice for achieving reproducible results in production processes. In addition to a high automation capability, the precise control of the energy deposition into the material plays an important role, especially when highly reflective materials, such as copper or aluminum, must be welded together. Alongside the use of highly brilliant fiber lasers in the near-infrared range with a focal diameter of a few tens of micrometers, diode lasers in the wavelength range of 445 nm are increasingly being used. Here, beam diameters of a few hundred micrometers can be achieved. With a wavelength of 445 nm, the absorptivity in copper can be increased by more than a factor of 10 compared to a near-infrared laser beam sources in solid state at room temperature. This paper presents the in situ X-ray observation of laser welding processes on CuSn6 with a laser beam source with a wavelength of 445 nm using synchrotron radiation at DESY Petra III Beamline P07 EH4 in Hamburg, Germany. For the experiments, the laser radiation was focused via two separate optics to focal diameters of 362 µm and 609 µm. To characterize the dynamics of the vapor capillaries depending on the different focal diameters dF, the parameters were varied with respect to laser power PL and feed rate v. For the investigations, a synchrotron beam of 2 × 2 mm2 in size with a photon energy of 89 keV was used, and the material samples were analyzed by means of phase-contrast videography to show the boundaries between solid, liquid, and gaseous material phases. The results of this paper show the welding depths achieved and how the geometry of the vapor capillary behaves by changing the focal diameter, laser power and feed rate.

Experimental characterization of the optical klystron effect to measure the intrinsic energy spread of high-brightness electron beams

The intrinsic energy spread of electron beams needs to be measured to characterize and optimize high-brightness electron beam sources such as those driving x-ray free-electron lasers (FELs). We demonstrate the use of the optical klystron effect as a precise and high-resolution method to measure the electron beam energy spread. The optical klystron setup consists of undulator modules and magnetic chicanes placed between them. The energy spread is found by measuring the radiation power produced in the undulators as a function of the chicanes’ strengths. High resolution and simplicity are the advantages of this approach, in contrast to the standard method, which measures the longitudinal phase space of the electron beam with a transverse deflector. The demonstration was performed at Athos, the soft x-ray FEL beamline of SwissFEL, for which we measured energy spreads below 1 MeV at a central beam energy of 3.4 GeV. We have verified the consistency of the method for different parameters (radiation wavelengths, undulator polarization configurations, and electron bunch durations) and we have benchmarked it against the standard measurement approach using a transverse deflector. Our results confirm the optical klystron as a valid approach to measure the electron beam energy spread. The method can be especially useful to reconstruct low energy spread values, where the conventional approach may be resolution limited, such as in ultra high-brightness radiofrequency photoinjectors or plasma sources, or when transverse deflectors are not available. Published by the American Physical Society 2024

Continuous cold rubidium atomic beam with enhanced flux and tunable velocity.

We present a cold atomic beam source based on a two-dimensional (2D)+ magneto-optical trap (MOT), capable of generating a continuous cold beam of 87Rb atoms with a flux up to 4.3 × 109 s-1, a mean velocity of 10.96(2.20) m/s, and a transverse temperature of 16.90(1.56) µK. Investigating the influence of high cooling laser intensity, we observe a significant population loss of atoms to hyperfine-level dark states. To account for this, we employ a multiple hyperfine level model to calculate the cooling efficiency associated with the population in dark states, subsequently modifying the scattering force. Simulations of beam flux at different cooling and repumping laser intensities using the modified scattering force are in agreement with experimental results. Optimizing repumping and cooling intensities enhances the flux by 50%. The influence of phase modulation on both the pushing and cooling lasers is experimentally studied, revealing that the mean velocity of cold atoms can be tuned from 9.5 m/s to 14.6 m/s with a phase-modulated pushing laser. The versatility of this continuous beam source, featuring high flux, controlled velocity, and narrow transverse temperature, renders it valuable for applications in atom interferometers and clocks, ultimately enhancing bandwidth, sensitivity, and signal contrast in these devices.

Divergence angle consideration in energy spread measurement for high-quality relativistic electron beam in laser wakefield acceleration

The thorough exploration of the transverse quality represented by divergence angle has been lacking yet in the energy spread measurement of the relativistic electron beam for laser wakefield acceleration (LWFA). In this work, we fill this gap by numerical simulations based on the experimental data, which indicate that in a C-shape magnet, magnetic field possesses the beam focusing effect, considering that the divergence angle will result in an increase in the full width at half maxima (FWHM) of the electron density distribution in a uniformly isotropic manner, while the length-to-width ratio decreases. This indicates that the energy spread obtained from the electron deflection distance is smaller than the actual value, regardless of the divergence angle. A promising and efficient way to accurately correct the value is presented by considering the divergence angle (for instance, for an electron beam with a length-to-width ratio of 1.12, the energy spread correct from 1.2% to 1.5%), providing a reference for developing the high-quality electron beam source.

Effect of metal impurities on the adsorption energy of cesium and work function of the cesiated Mo (0 0 1) surface

Based on the DFT method, the effects of copper and tungsten impurities present in the negative ion source of neutral beams on the cesiated surface were studied, including their effects on the adsorption energy of cesium on the surface and the surface work function. The results indicate that copper impurities significantly increase the average adsorption energy of cesium, whereas tungsten has limited enhancement on the average adsorption energy of cesium and may even reduce it. The work function calculations show that, at cesium coverages below 4/16 θ, copper impurities cause a significant increase in the work function. However, at cesium coverages above 6/16 θ, high-coverage copper impurities lead to a further decrease in the work function, causing the cesium coverage corresponding to the lowest work function to shift towards higher cesium coverage. Under any tungsten impurity and cesium coverage, tungsten impurities can significantly increase the surface work function, with the maximum increase reaching 0.50 eV. The dipole moment density analysis shows that in most cases, impurities significantly reduce the dipole moment density of the cesiated surface, except when the coverage of cesium and copper impurities is above 6/16 θ. The charge transfer results show that the copper impurity layer has more positive charge compared to the tungsten impurity layer, which significantly affects the dipole moment density of the surface system. In addition, adsorbed atoms cause electrons in the molybdenum atomic layer to migrate to the surface, resulting in the molybdenum substrate having a pronounced negative dipole moment.

A receiver intensity for Super Lorentz Gaussian beam (SLG) propagation via the moderate turbulent atmosphere using a novelty mathematical model

Abstract First of all, the beam propagation of Super Lorentz Gaussian (SLG) profile is propagated via space, the recent research dealt extensively with the investigation of the propagation of SLG in a level of specified atmospheric. In a turbulent atmosphere of intensity and receiver field, models were derived from a new mathematical expression of intensity and analyzed. Also, to find the power scintillation indicators for the SLG beam in a random turbulence of receiver plane. The equations are obtained for the average receiver-aperture. The new beam of SLG systems generated a modified model when compared with the receiver-aperture averaging. When we revisions the parameters, firstly is started the factor source size, this affected the profile for the power propagation and the analysis proved that the average of the aperture is affected by increasing the distance of propagation length. The enhancement of the average power of the aperture effect reliably with the source size of the initial beam source depends on several factors, including the structure constant, the beam order and static value of source size. Finally, the target of this article is detected a novel of mathematical expression of the receiver intensity is applied in the system of optical communications.

Tailored laser beam shapes for welding of copper using green laser radiation

AbstractThe rapid development of laser beam sources and adapted welding technologies in recent years lead to an increased use of laser welding techniques in automated production nowadays. Especially its precision and local energy input are key features for joining applications in electric vehicle components, where joints have to meet both mechanical and electrical requirements as current-carrying connections. However, the copper materials used are difficult to weld due to their physical properties, making a stable process with fewest seam imperfections only feasible within a limited process window. Recently available beam sources emitting visible laser radiation have proven to overcome the low absorptivity at process start, but spattering is still a prone defect significantly affecting process efficiency and quality. Literature approaches for modifying the energy input point to laser beam shaping as a method for reducing process imperfections, which, however, has not been extensively researched in copper processing using green laser radiation.Thus, this study investigates the influence of a shaped intensity profile for visible laser radiation created with a reflective diffractive optical element in laser beam welding with laser powers up to 3 kW. A characterization of the process dynamics is performed by use of high-speed imaging, and metallographic analysis is used to elaborate benefits of the applied beam shapes. With beam shaping, an enlarged heat conduction welding regime and an advantageous seam shape are found. Furthermore, a decrease in spatter formation during deep penetration welding is detected for the elliptical beam profile, which correlates with an oscillation movement of the capillary.