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When high-energy electrons from scanning transmission electron microscope (STEM) are interacting with the liquid, the vast majority of the chemical reactions that are observed are induced by the radiolysis breakdown of the liquid molecules.
The transfer of a high-intensity laser pulse energy to a high-energy electron beam via the direct laser acceleration mechanism is shown to be significantly enhanced through control of the plasma density gradient. Experiments performed using the OMEGA EP facility's high-intensity beams altered the plasma density and gradients by changing the Mach number and the angle of the gas-jet nozzle to the laser axis. When a long density gradient at the rear of the target is used, the total high-energy electron number measured was enhanced by 4.5 times compared to a shorter rear gradient. Complementary two-dimensional simulations, which follow the laser field evolution and the corresponding electron dynamics, strongly support the key trends observed in the experiment. The effect is twofold, the long density gradient provides the longest acceleration distance while it minimizes the formation of the sheath field as the electron beam exits into the vacuum. This study shows the importance of tailoring the plasma density.
High-energy electron scattering is a clean, precise probe for measurements of hadronic and nuclear structure and plays a key role in understanding the role of high-momentum nucleons (and quarks) in nuclei. Jefferson Lab has dramatically expanded our knowledge of the high-momentum nucleons generated by short-range correlations, providing sufficient insight to model much of their impact on nuclear structure in neutron stars and in low- to medium-energy scattering observables, including neutrino oscillation measurements. These short-range correlations also seem related to the modification of the quark distributions in nuclei, and efforts to improve our understanding of the internal structure of these short-distance and high-momentum configurations in nuclei will provide important input on a wide range of high-energy observables.
Among the many effects that occur in beam-beam electron-positron collisions at TeV energies, emission of hard synchrotron radiation, or beamstrahlung, has special importance. Beamstrahlung determines the energy spectrum of the most energetic electrons, positrons, and photons and supplies the initial condition for the calculation of all other QED processes. In this paper, we show that the description of beamstrahlung simplifies in the limit of large quantum parameter $Υ$, which is realized in 10 TeV collider designs. The beamstrahlung spectra for electrons and photons are given in terms of universal functions. We supply approximations to these functions that will be useful for more general studies of the beam-beam interaction at very high energies.
Abstract Laser wakefield accelerators commonly produce on-axis, low-divergence, high-energy electron beams. However, a high charge, annular shaped beam can be trapped outside the bubble and accelerated to high energies. Here we present a parametric study on the production of low-energy-spread, ultra-relativistic electron ring beams in a two-stage gas cell. Ring-shaped beams with energies higher than 750 MeV are observed simultaneously with on axis, continuously injected electrons. Often multiple ring shaped beams with different energies are produced and parametric studies to control the generation and properties of these structures were conducted. Particle tracking and particle-in-cell simulations are used to determine properties of these beams and investigate how they are formed and trapped outside the bubble by the wake produced by on-axis injected electrons. These unusual femtosecond duration, high-charge, high-energy, ring electron beams may find use in beam driven plasma wakefield accelerators and radiation sources.
This work presents an alternative method to conventional III-V substrate recycling methods via growth of NaCl on nearly-lattice matched GaAs (001) substrates. Reflection high energy electron diffraction and transmission electron microscopy confirm an epitaxial relationship between the NaCl layers and the underlying GaAs. If the sample is heated too much prior to GaAs deposition, the NaCl fully desorbs from the surface. The quality of the deposition of GaAs on NaCl ranges from amorphous at low temperature to polycrystalline at intermediate temperatures. Exposure to electron beams during growth results in larger and (001) textured grains. The substrate is separated from the GaAs film in seconds via submersion in water, revealing a substrate surface comparable to the original.
To explore the confinement of high-energy ions above the space charge limit, we have developed a hybrid magnetic and electrostatic confinement device called an Orbitron. The Orbitron is a crossed-field device combining aspects of magnetic mirrors, magnetrons, and orbital ion traps. Ions are confined in orbits around a high-voltage cathode with co-rotating electrons confined by a relatively weak magnetic field. Experimental and computational investigations focus on reaching ion densities above the space charge limit through the co-confinement of electrons. The experimental apparatus and suite of diagnostics are being developed to measure the critical parameters, such as plasma density, particle energy, and fusion rate for high-energy, non-thermal plasma conditions in the Orbitron. Initial results from experimental and computational efforts have revealed the need for cathode voltages on the order of 100–300 kV, leading to the development of a custom high voltage, ultra-high vacuum bushing rated for 300 kV.
The photon flux resulting from high-energy electron beam interactions with high-field systems, such as those found in the upcoming FACET-II experiments at the SLAC National Accelerator Laboratory, yields deep insight into the electron beam’s underlying dynamics during the interaction. However, extracting this information is an intricate process. To demonstrate how to approach this challenge using modern methods, this paper utilizes simulated data that models plasma wakefield acceleration-derived betatron radiation in experiments to determine reliable methods of reconstructing key beam and beam-plasma interaction properties. For betatron radiation measurements, translating the observed 200 keV to 30 MeV photon double-differential energy-angle spectra obtained from an advanced Compton spectrometer requires testing multiple methods to optimize the pipeline from its response to incident electron beam information. The paper compares maximum likelihood estimation and machine learning to refine the translation of photon spectra into precise electron beam metrics, such as spot size, energy, and emittance, enhancing the understanding of beam behavior within these dense, high-field environments. We also introduce machine learning and the expected maximization algorithm to reconstruct the primary photon spectrum, employing a multilayer neural network for regression analysis of the energy and angle spectra. With appropriate modifications, the advanced methods reproduce relevant incident beam parameters with high accuracy, even for beam sizes in the <10 μm range. This capacity is critical to understanding intense beam propagation and its optimization in plasma.
The objective of this project is to develop the Direct E-Beam Synthesis (DEBS) process that uses high-energy electron beams (E-Beam) to break chemical bonds. This allows the production of valuable chemicals, such as acetic acid, methanol, and carbon monoxide, at relatively low severity (pressure near one atmosphere and temperatures <150°C) from near-pure CO 2 captured from a pulverized coal-fired power plant and methane, imported as natural gas. Creating such valuable products will offset the cost of carbon capture and storage. Through this project, we have designed, constructed, and operated an E-Beam reactor to examine the feasibility of performing dry reforming reaction without a catalyst using only DEBS. We have verified the production of syngas with 1:1 H2:CO ratio and calculated that the energy cost for conversion is about 5.2 eV/molecule of product for dry reforming reaction which is similar to the energy cost for conversion using conventional thermochemical conversion but under significantly milder conditions (room temperature and atmospheric pressure). We have performed a technoeconomic analysis (TEA) to estimate the total capital requirement and the cost of production for a 99.4 MMSCFD syngas production plant via non-catalytic Direct E-Beam Synthesis (DEBS) technology utilizing a high-energy electron beam (E-Beam) accelerator. No assumption is made for syngas utilization downstream, and the incoming reactants are pure CO 2 from carbon capture (assumed to be at zero cost) and natural gas. The Total As-Spent Cost (TASC) was calculated to be $\$242.5$ million, resulting in a levelized cost of syngas (LCOS) of $\$175.84$/tonne (metric) at a natural gas price of $\$6.24$/MMBTU1. The cost of syngas is primarily determined by the price of natural gas. If the cost of the CO 2 feedstock is assumed to be non-zero, then the price of the CO 2 feed also heavily influences the levelized cost of syngas. The potential impact on the cost of electricity from syngas revenue is significant. Following DOE NETL’s guidance, a lifecycle analysis (LCA) was conducted to compare the cradle-to-gate life cycle emissions of GTI Energy’s novel Direct E-Beam Synthesis (DEBS) process that produces syngas via the reaction of methane and carbon dioxide to the emissions of a state-of-the-art Steam Methane Reforming (SMR) process that also produces syngas via the reaction of methane and steam. The DEBS process results in less GHG emissions than SMR (with CO product as the basis of comparison). openLCA was used for the LCA and the results show that the total global warming potential (GWP) of DEBS is 0.981 kg CO 2 e per kg CO product, while the SMR process has a global warming potential of 2.573 kg CO 2 e per kg CO product. The ratio of the GWP of the proposed product system to the comparison product system is 0.381. This percent change is 61.9% lower GWP than SMR.
he Electron-Ion Collider (EIC) is a new, innovative, large-scale particle accelerator conceived by U.S. nuclear physicists over two decades and planned for construction at Brookhaven National Laboratory on Long Island, New York by the U.S. Department of Energy in the 2020s. The EIC will study protons, neutrons and atomic nuclei with the most powerful electron microscope ever built, in terms of its unique versatility of resolving power and intensity. The resolution and intensity is achieved by colliding high-energy electrons with high-energy protons or (a range of different) ion beams. The EIC provides the capability of colliding beams of polarized electrons with polarized beams of light ions, and this all at high intensity. The EIC was established as the highest priority for new construction in the 2015 US Nuclear Physics Long Range Plan, was favorably endorsed by a committee established by the National Academy of Sciences in 2018 to assess the science case. In December 2019, the EIC was granted Critical Design Zero by the US Department of Energy, which launched the EIC as an official project of the US government
The electron-ion collider (EIC), to be constructed at Brookhaven National Laboratory, will collide polarized high-energy electron beams with hadron beams, achieving luminosities of up to 1.0 × 10 34 cm −2 s −1 in the center-of-mass energy range of 20–140 GeV. To reach such high luminosity, the EIC will employ small, flat beams at the interaction point. According to the design of the EIC hadron storage ring (HSR), hadron beams with a large transverse emittance ratio of 11:1 will be generated at the injection energy using an electron cooling technique and then accelerated to high energies for collisions. Accelerating hadron beams with such a large emittance ratio had never been demonstrated elsewhere—until our recent beam experiment at the relativistic heavy ion collider (RHIC). In this experiment, we successfully generated a large transverse emittance ratio of 13:1 with a gold-ion beam at 31 GeV/nucleon using stochastic cooling. We then accelerated this beam, with a transverse emittance ratio of 11:1, from 31 to 100 GeV/nucleon. Thanks to RHIC’s high-performance orbit, tune, and decoupling feedback systems, the large emittance ratio was well maintained throughout the 5-min-long acceleration process. This experiment fully validated the EIC/HSR design assumptions—namely, that large-emittance-ratio hadron beams can be generated at injection energy and then accelerated to high energies for collisions.
Structural stability of MoS 2 nanosheets were in-situ investigated from selected area electron diffraction. The nano-sheets were stable at low-energy electron irradiation (80 keV) while degraded under high-energy electron irradiation (120 keV).
We investigate the structural and magnetic properties of La 0.7 Sr 0.3 CrO 3 /La 0.7 Sr 0.3 MnO 3 (LSMO) heterostructures grown on (001)-oriented MgO by molecular beam epitaxy. Due to the large film-substrate lattice mismatch, strain relaxation is found to occur within the first 2–3 unit cells (uc) of the film as evidenced by reflection high energy electron diffraction and high-resolution synchrotron x-ray reciprocal space mapping. Furthermore, we find that the presence of the LSCO spacer and capping layers leads to ferromagnetism in ultra-thin LSMO layers with thicknesses of the order of 2 uc with the magnetic easy axis oriented in the film plane. Net magnetic moments of 1.4 and 2.4 μ B /Mn are measured for (2 uc LSCO/2 uc LSMO) and (2 uc LSCO/4 uc LSMO) superlattices, respectively, by superconducting quantum interference device magnetometry. The effective magnetic anisotropy of the relaxed (2 uc LSCO/4 uc LSMO) heterostructure is found to be an order of magnitude higher than bulk LSMO highlighting the critical role of interfacial interactions in tuning magnetic anisotropy at complex oxide interfaces.
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Silicon polymorphs with exotic electronic and optical properties have recently attracted significant attention due to their wide range of useful band gap characteristics. They are typically formed by static high-pressure techniques, which limits the crystal structures that can be made. This constitutes a major obstacle to study these polymorphs and their incorporation into existing technology. Approaches have attempted to address this shortcoming through using dynamic conditions and chemical precursor materials. Here, we report on an approach to create unusual crystal structures deep in the bulk of a silicon crystal by irradiating it with a laser pulse at ultrarelativistic intensity of up to 7.5 × 10 19 W/ c m 2 . Laser-generated electrons with MeV energy swiftly penetrate the target with speed close to the speed of light and deposit their energy into a large volume across the whole thickness of the sample. The relativistic electron current creates, via branching propagation and ionization, high-energy-density conditions for thermodynamically nonequilibrium phase transformation paths into new crystal polymorphs. X-ray microdiffraction and synchrotron x-ray diffraction analyses indicate, along with conventional dc-Si, the presence of exotic silicon structures in the bulk of the laser intact target volume. These structures are identified as body-centered bc8-Si, rhombohedral r8-Si, hexagonal-diamond hd-Si, and the tetragonal Si-VIII, all phases of Si that have previously been made through static techniques. Additionally, simple-tetragonal st12-Si and body-centered tetragonal bt8-Si were observed along with signatures of not yet identified diffraction spots. Both st12-Si and bt8-Si have only been observed in ultrafast laser microexplosion conditions at much lower laser intensity ∼ 10 14 W/ c m 2 and within a micron-thin surface layer. The findings here are supported by direct observation of nanoparticles with high-resolution transmission electron microscopy and corresponding fast Fourier transform analysis of their interatomic distances. The presented analyses of absorbed laser energy, generation of the MeV electron current, and deposition of energy across the whole target thickness provide a solid basis for drawing the conclusion that the observed silicon polymorphs were produced because of laser-generated high-energy electrons fast-penetrating deeply into the bulk of silicon. In contrast to solid-solid transformations, the plasma-solid transitions offer a paradigm for the creation of exotic, high-energy density materials inside the bulk of the sample by using laser pulses at relativistic intensities. Published by the American Physical Society 2024
Supersonic gas jets produced by converging-diverging (C-D) nozzles are commonly used as targets for laser-plasma acceleration (LPA) experiments. A major point of interest for these targets is the gas density at the region of interaction where the laser ionizes the gas plume to create a plasma, providing the acceleration structure. Tuning the density profiles at this interaction region is crucial to LPA optimization. A "flat-top" density profile is desired at this line of interaction to control laser propagation and high energy electron acceleration, while a short high-density profile is often preferred for acceleration of lower-energy tightly-focused laser-plasma interactions. A particular design parameter of interest is the curvature of the nozzle's diverging section. We examine three nozzle designs with different curvatures: the concave "bell", straight conical and convex "trumpet" nozzles. We demonstrate that, at mm-scale distances from the nozzle exit, the trumpet and straight nozzles, if optimized, produce "flat-top" density profiles whereas the bell nozzle creates focused regions of gas with higher densities. An optimization procedure for the trumpet nozzle is derived and compared to the straight nozzle optimization process. We find that the trumpet nozzle, by providing an extra parameter of control through its curvature, is more versatile for creating flat-top profiles and its optimization procedure is more refined compared to the straight nozzle and the straight nozzle optimization process. Furthermore, we present results for different nozzle designs from computational fluid dynamics (CFD) simulations performed with the program ANSYS Fluent and verify them experimentally using neutral density interferometry.
Recent success of Low Energy RHIC Electron Cooler (LEReC) opened a road for development of high energy electron coolers based on non-magnetized electron bunches accelerated by RF cavities. Electrons in such coolers can have velocity distribution with various unequal horizontal, vertical and longitudinal velocity spreads. In this paper we revisit a formula of friction force in non-magnetized cooling and derive a number of useful expressions for different limiting cases.
Dissipative capillary discharges form plasma channels which allow for high power laser guiding, enabling efficient electron acceleration in a laser wakefield accelerator. However, at the low plasma densities required to produce high-energy electrons, in order to avoid capillary wall damage, high power lasers need a tighter transverse confinement that cannot be achieved by the capillary discharge powered by Ohmic heating alone. The introduction of an additional laser for heating of the plasma leads to deeper and narrower plasma channels. Here we investigate the formation of laser-heated axially uniform plasma channels. Here, we show that a high degree of longitudinal uniformity can be achieved despite significant evolution of the heater laser during its propagation through the channel.