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Electron beams produced in RF linear accelerators will naturally be modulated at the RF frequency. Here we report measurements of the RF harmonic content of a 21.6 MeV electron beam coasting in air, as well as the RF harmonic content of x-rays produced from that electron beam, and the effects of these modulated electron and x-ray beams on several fast detection systems. The RF fundamental and its higher harmonics were found to be impressed onto the x-rays generated from the electron beam, and the response of an RF waveguide to passage of the modulated x-ray signal indicated that this harmonic content was also impressed onto the secondary electrons produced by the passage of the x-rays through the waveguide. An unexpected, interference-like effect was observed, which was particularly prominent in the case of the waveguide when struck by the modulated x-rays. The participation of secondary electrons produced by passage of the x-rays through the x-ray converter upstream of the waveguide was ruled out as a significant contributor to this effect. [ABSTRACT FROM AUTHOR] more...

We demonstrate the application of low-temperature cathodoluminescence (CL) with high lateral, depth, and spectral resolution to determine both the lateral (i.e., perpendicular to the incident primary electron beam) and axial (i.e., parallel to the electron beam) diffusion length of excitons in semiconductor materials. The lateral diffusion length in GaN is investigated by the decrease of the GaN-related luminescence signal when approaching an interface to Ga(In)N based quantum well stripes. The axial diffusion length in GaN is evaluated from a comparison of the results of depth-resolved CL spectroscopy (DRCLS) measurements with predictions from Monte Carlo simulations on the size and shape of the excitation volume. The lateral diffusion length was found to be (95 ± 40) nm for nominally undoped GaN, and the axial exciton diffusion length was determined to be (150625) nm. The application of the DRCLS method is also presented on a semipolar (11̄22) sample, resulting in a value of (70 ± 10) nm in p-type GaN. [ABSTRACT FROM AUTHOR] more...

We propose a method to produce valley-polarized electron beams using a bilayer graphene npn junction. By analyzing the transmission properties of electrons through the junction with zigzag interface in the presence of trigonal warping, we observe that there exist a range of incident energies and barrier heights in which transmitted electrons are well polarized and collimated. From this observation and by performing numerical simulations, it is demonstrated that valley-dependent electronic currents with nearly perfect polarization can be generated. We also show that the peak-to-peak separation angle between the polarized currents is tunable either by incident energy or by barrier height each of which is controlled by using top and back gate voltages. The results can be used for constructing an electron beam splitter to produce valley-polarized currents. [ABSTRACT FROM AUTHOR] more...

In this paper, the finite-element method (FEM) is applied for an exact solution of the dispersion of hybrid electromagnetic waves excited in a novel combined elliptical waveguide. This special configuration is included of an elliptical metallic waveguide filled with a dielectric material, whereas two axial hollows with circular cross section have been created in it. A hollow is placed in one of focuses of the elliptical waveguide and second hollow is located in another focus or shifted from it. Two straight relativistic electron beams with the same currents and velocities in opposite directions are injected inside the hollows. Here, we apply an accurate approach in which the electromagnetic fields described by the FEM and satisfies boundary conditions at the interfaces of different regions. Then, the time growth rate of slow waves amplified by the electron beam is numerically calculated. The excited waves are in microwave range. The effects of accelerating voltage and current density of electron beams, and geometrical parameters such as radius and location of electron beam, on the frequency spectra, the growth rate, and profiles of axial electric and magnetic fields of excited slow waves are studied. Our research shows, the novel waveguide studied in this paper is superior to other waveguide structures in wave amplification with applying minimum input electrical power. [ABSTRACT FROM AUTHOR] more...

We provide here a comprehensive exposition of a novel dispersion engineering framework for high-power electron-beam-driven devices based on multiple degenerate eigenwave synchronization in slow-wave structures (SWSs). These degenerate eigenwaves, related to an exceptional point of degeneracy (EPD) in the parameter space of the SWSs, lead to an enhanced interaction with the electron beam associated with a vanishing group velocity, which depends on the EPD order. Therefore, a “supersynchronous” mechanism based on multiple degenerate eigenwaves, associated with any order of EPD, provides advantages in terms of power generation efficiency at microwave frequencies, millimeter-wave frequencies, and terahertz frequencies. We present a physical description of EPDs in SWSs using a generalized Pierce theory developed for multimodal interaction. We show unique characteristics related to EPDs in “hot” (coupled with the electron beam) SWSs with third- and fourth-order EPDs for the sake of demonstration, but this can be extended to any order of degeneracy. We demonstrate advantages of the proposed regimes compared to conventional single-mode high-power devices such as backward-wave oscillators and traveling-wave tube amplifiers. In addition to that we show a possibility of high-power oscillators at millimeter-wave and terahertz frequencies based on a fourth-order EPD. In particular, we demonstrate a degenerate band-edge oscillator at 638 GHz based on particle-in-cell simulations. Apart from the examples provided herein, the concept of EPD can be used to design a wide variety of devices including gyrotrons, free electron lasers, and high-power isolators. [ABSTRACT FROM AUTHOR] more...

Fishbone-type oscillations with poloidal and toroidal mode numbers m = 1, n = 1 have been observed during lower hybrid current drive (LHCD) in the Alcator C-Mod tokamak. At relatively high plasma density and collisionality, the driving mechanism appears to be the nonresonant destabilization of an m/n = 1/1 MHD resistive internal kink mode by the pressure of the suprathermal electrons produced by the LHCD rather than a wave-particle resonance between the mode and the fast electrons. Direct measurements of the fast electrons are consistent with nonresonant destabilization and saturation. The effects of the 1/1 mode kink displacement on the LHCD deposition and fast electron concentration lead to nonresonant saturation mechanisms that may also contribute to the saturation of resonant lower hybrid fishbones. [ABSTRACT FROM AUTHOR] more...

The accuracy of the electron stopping powers of elements and compounds is of great importance to medical dosimetry, radiation therapy, and radiation transport simulations. This paper summarises the commissioning of a new high purity Germanium (HPGe) detector and presents a feasibility study confirming the suitability of a method to determine electron stopping power data. A high-efficiency, HPGe detector was commissioned and found to match the manufacturer's performance specifications. A simple experiment was designed to obtain spectra acquired from a Sr-90/Y-90 radioactive check source with varying thicknesses of absorber (Al and Cu foils) placed between the source and the detector. The entire experimental arrangement was simulated using the EGSnrc radiation transport system. The Monte Carlo model of the detector accurately replicated the detector response to electrons and a quantitative analysis showed that the difference between the simulated and measured spectra was less than 1.5%, using the standard tabulated ICRU 37 stopping power data for the simulations. Based on the experiment with the low-energy Sr-90/Y-90 source, it is anticipated that this method can be used with a well-characterized quasi-monoenergetic electron beam, as available from a research linear accelerated to yield accurate measurements to validate current tabulated stopping power data. [ABSTRACT FROM AUTHOR] more...

Crosslinking and chain scission occur simultaneously during irradiation of polymers and influence their properties in an opposite way. To characterize the radiation-induced changes and evaluate how they influence the performance of the polymer, quantification of these reactions is crucial. In this work, the effect of styrene-butadiene rubber (SBR) radiation curing with doses ranging from 25 kGy to 200 kGy, at room temperature and air atmosphere was investigated. The Charlesby-Pinner and Charlesby-Rosiak equations were used to characterize the curing process. Only the Charlesby-Rosiak equation gave good linear representation of the data and allowed to obtain the parameters, which characterize the irradiated SBR system: (i) gel dose, (ii) ratio between chain scission and crosslinking, and (iii) radiation yields of crosslinking and chain scission. These parameters showed that SBR is quite resistant to ionizing radiation, where crosslinking predominates over chain scission. The effect of irradiation on in-rubber properties is discussed. An increase in radiation dose resulted in change of tensile strength, elongation at break, mechanical modules, hardness, glass transition temperature and thermo-oxidative stability. Freezing point depression experiments were also conducted. The depression of the solvent freezing temperature in swollen polymer gels provided information on polymer network and mesh size, staying in agreement with the crosslink density values. [ABSTRACT FROM AUTHOR] more...

Abstract: Purpose: To investigate the accuracy of the dosimetry of radiation fields produced by small ELEKTA cone collimators used for stereotactic radiosurgery treatments (SRS) using commercially available detectors EBT3 GafchromicTM film, IBA Stereotactic diode (SFD), and the recently developed detector DUO, which is a monolithic silicon orthogonal linear diode array detector. Methods: These three detectors were used for the measurement of beam profiles, output factors, and percentage depth dose for SRS cone collimators with cone sizes ranging from 5 to 50 mm diameter. The measurements were performed at 10 cm depth and 90 cm SSD. Results: The SRS cone beam profiles measured with DUO, EBT3 film, and IBA SFD agreed well, results being in agreement within ±0.5 mm in the FWHM, and ±0.7 mm in the penumbra region. The output factor measured by DUO with 0.5 mm air gap above agrees within ±1% with EBT3. The OF measured by IBA SFD (corrected for the over‐response) agreed with both EBT3 and DUO within ±2%. All three detectors agree within ±2% for PDD measurements for all SRS cones. Conclusions: The characteristics of the ELEKTA SRS cone collimator have been evaluated by using a monolithic silicon high spatial resolution detector DUO, EBT3, and IBA SFD diode. The DUO detector is suitable for fast real‐time quality assurance dosimetry in small radiation fields typical for SRS/SRT. This has been demonstrated by its good agreement of measured doses with EBT 3 films. [ABSTRACT FROM AUTHOR] more...

Abstract: A novel phantomless, EPID‐based method of measuring the beam focal spot offset of a linear accelerator was proposed and validated for Varian machines. In this method, one set of jaws and the MLC were utilized to form a symmetric field and then a 180o collimator rotation was utilized to determine the radiation isocenter defined by the jaws and the MLC, respectively. The difference between these two isocentres is directly correlated with the beam focal spot offset of the linear accelerator. In the current work, the method has been considered for Elekta linacs. An Elekta linac with the Agility® head does not have two set of jaws, therefore, a modified method is presented making use of one set of diaphragms, the MLC and a full 360o collimator rotation. The modified method has been tested on two Elekta Synergy® linacs with Agility® heads and independently validated. A practical guide with instructions and a MATLAB® code is attached for easy implementation. [ABSTRACT FROM AUTHOR] more...

Abstract: Purpose: This study evaluated a new electron collimation system design for Elekta 6–20 MeV beams, which should reduce applicator weights by 25%–30%. Such reductions, as great as 3.9 kg for the largest applicator, should result in considerably easier handling by members of the radiotherapy team. Methods: Prototype 10 × 10 and 20 × 20‐cm2 applicators, used to measure weight, in‐field flatness, and out‐of‐field leakage dose, were constructed according to the previously published design with two minor modifications: (a) rather than tungsten, lead was used for trimmer material; and (b) continuous trimmer outer‐edge bevel was approximated by three steps. Because of lead plate softness, a 0.32‐cm aluminum plate replaced the equivalent lead thickness on the trimmer's downstream surface for structural support. Models of all applicators (6 × 6–25 × 25 cm2) with these modifications were inserted into a Monte Carlo (MC) model for dose calculations using 7, 13, and 20 MeV beams. Planar dose distributions were measured and calculated at 1‐ and 2‐cm water depths to evaluate in‐field beam flatness and out‐of‐field leakage dose. Results: Prototype 10 × 10 and 20 × 20‐cm2 applicator measurements agreed with calculated weights, in‐field flatness, and out‐of‐field leakage doses for 7, 13, and 20 MeV beams. Also, MC dose calculations showed that all applicators (6 × 6–25 × 25 cm2) and 7, 13, and 20 MeV beams met our stringent in‐field flatness specifications (±3% major axes; ±4% diagonals) and IEC out‐of‐field leakage dose specifications. Conclusions: Our results validated the new electron collimating system design for Elekta 6–20 MeV electron beams, which could serve as basis for a new clinical electron collimating system with significantly reduced applicator weights. [ABSTRACT FROM AUTHOR] more...

Nowadays, laser wakefield acceleration is considered to be one of the perspective methods for GeV electron beam production. The combination of laser accelerated electrons and Compton backscattering of a probe light beam opens the possibility of creating the tabletop source of a femtosecond light beam in x-ray and gamma ranges. The project is aimed at creating a laser-driven Compton light source in ILP SB RAS in collaboration with BINP SB RAS. Production of 1–10 pC electron beams in sub-ps time range duration with energies up to 100 MeV is expected to be a result of the first stage of the project. Since the energy of electrons does not exceed 100 MeV, it allows the use of the Faraday cup (FC) with reasonable dimensions, instead of the commonly used integrating current transformer. The geometry of the FC has been optimized taking into account beam stopping simulation as well as a low capacity requirement. Simulation of high-frequency properties of the entire system was carried out. The system has been tested at the VEPP-5 electron linac. The results of developing and testing this FC are presented. [ABSTRACT FROM AUTHOR] more...

A novel experimental setup has been implemented to provide accurate electron scattering cross sections from molecules at low and intermediate impact energies (1-300 eV) by measuring the attenuation of a magnetically confined linear electron beam from a molecular target. High-resolution electron energy is achieved through confinement in a magnetic gas trap where electrons are cooled by successive collisions with N2. Additionally, we developed and present a method to correct systematic errors arising from energy and angular resolution limitations. The accuracy of the entire measurement procedure is validated by comparing the N2 total scattering cross section in the considered energy range with benchmark values available in the literature. [ABSTRACT FROM AUTHOR] more...

The influence of heat input in electron beam (EB) process on microstructure, mechanical properties, and pitting corrosion resistance of duplex stainless steel (DSS) welded interface was investigated. The rapid cooling in EB welding resulted in insufficient austenite formation. The austenite mainly consisted of grain boundary austenite and intragranular austenite, and there was abundant Cr 2 N precipitation in the ferrite. The Ni, Mo, and Si segregation indicated that the dendritic solidification was primarily ferrite in the weld. The weld exhibited higher hardness, lower toughness, and poorer pitting corrosion resistance than the base metal. The impact fractures of the welds were dominated by the transgranular cleavage failure of the ferrite. The ferrite was selectively attacked because of its lower pitting resistance equivalent number than that of austenite. The Cr 2 N precipitation accelerated the pitting corrosion. In summary, the optimised heat input slightly increased the austenite content, reduced the segregation degree and ferrite texture intensity, decreased the hardness, and improved the toughness and pitting corrosion resistance. However, the effects were limited. Furthermore, optimising the heat input could not suppress the Cr 2 N precipitation. Taking into full consideration the microstructure and properties, a heat input of 0.46 kJ/mm is recommended for the EB welding of DSS. [ABSTRACT FROM AUTHOR] more...

Uniaxial anisotropic near-zero metamaterials have been utilized to design 2-D apertures with beamwidth control and directivity enhancement. Theoretical study shows that the two principal plane beamwidth of an aperture can be significantly reduced, both independently and simultaneously. With two proposed simplified loading models as a transitional structure, the 3-D bulk metamaterials are eventually reduced to 2-D metasurfaces with an array of metallic inclusions. In the design procedure, a critical equivalence between 2-D metasurfaces and 3-D metamaterial slabs with a specific thickness is discussed and validated. Measured results of the fabricated prototypes have demonstrated that a final aperture design loaded with low-profile electric LC and split-ring resonator metasurfaces has a substantial beamwidth reduction on both principal planes and a 4.32 dBi gain enhancement around the operating frequency. [ABSTRACT FROM PUBLISHER] more...

High-resolution imaging of electron beam–sensitive materials is one of the most difficult applications of transmission electron microscopy (TEM). The challenges are manifold, including the acquisition of images with extremely low beam doses, the time-constrained search for crystal zone axes, the precise image alignment, and the accurate determination of the defocus value. We develop a suite of methods to fulfill these requirements and acquire atomic-resolution TEM images of several metal organic frameworks that are generally recognized as highly sensitive to electron beams. The high image resolution allows us to identify individual metal atomic columns, various types of surface termination, and benzene rings in the organic linkers. We also apply our methods to other electron beam–sensitive materials, including the organic-inorganic hybrid perovskite CH3NH3PbBr3. [ABSTRACT FROM AUTHOR] more...

The OLYMPUS experiment measured the cross-section ratio of positron–proton elastic scattering relative to electron–proton elastic scattering to look for evidence of hard two-photon exchange. To make this measurement, the experiment alternated between electron beam and positron beam running modes, with the relative integrated luminosities of the two running modes providing the crucial normalization. For this reason, OLYMPUS had several redundant luminosity monitoring systems, including a pair of electromagnetic calorimeters positioned downstream from the target to detect symmetric Møller and Bhabha scattering from atomic electrons in the hydrogen gas target. Though this system was designed to monitor the rate of events with single Møller/Bhabha interactions, we found that a more accurate determination of relative luminosity could be made by additionally considering the rate of events with both a Møller/Bhabha interaction and a concurrent elastic e p interaction. This method was improved by small corrections for the variance of the current within bunches in the storage ring and for the probability of three interactions occurring within a bunch. After accounting for systematic effects, we estimate that the method is accurate in determining the relative luminosity to within 0.36%. This precise technique can be employed in future electron–proton and positron–proton scattering experiments to monitor relative luminosity between different running modes. [ABSTRACT FROM AUTHOR] more...

Many shellfish-borne viral outbreaks have been reported in East Asia, where abalone is predominantly eaten raw. This study investigated the effects of electron beam (e-beam) irradiation (1–10 kGy) on the inactivation of murine norovirus-1 (MNV-1), as a surrogate of human norovirus (NoV). The cell culture lysate of MNV-1 and abalone meat and viscera were irradiated with e-beam (1, 3, 5, 7, and 10 kGy). The titer of MNV-1 significantly ( p < 0.05) decreased by 0.38–2.18, 0.31–1.45 and 0.41–1.56 log 10 PFU/mL in the suspension, abalone meat, and abalone viscera, respectively, as the dose of e-beam irradiation increased. However, all Hunter colors, five sensory attributes and four textures parameter not significantly ( p > 0.05) different in abalone after e-beam irradiation. D-values were calculated using first-order model and corresponded to 3.92, 6.26, and 5.23 kGy in the suspension, abalone meat, and abalone viscera, respectively. There were no significant changes in food qualities of pH, moisture contents and TBARS levels. Thus, e-beam can be used as an effective and useful non-thermal treatment to reduce MNV-1 in abalone. We suggest using a dose of e-beam irradiation >6.26 kGy to achieve 90% log 10 reduction of MNV-1 in abalone without deleterious changes of food qualities. [ABSTRACT FROM AUTHOR] more...

We have used deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) to characterize the electrically active point defects introduced in n -type gallium arsenide by electron beam exposure prior to Schottky metallization. The GaAs crystals were exposed to incident electrons at sub-threshold energies which are deemed low and insufficient to form defects through ion solid interactions. DLTS revealed a set of electron traps different from those commonly observed in n -GaAs after particle irradiation. These different signatures from the same radiation type suggest that different mechanisms are responsible for defect formation in the two electron irradiation processes. An analysis of the conditions under which the defects were formed was done to distil a number of possible defect formation mechanisms using the experimental evidence obtained. [ABSTRACT FROM AUTHOR] more...

In this work we use the one-dimensional free electron laser (FEL) model to define necessary parameters of an electron beam to produce self amplified spontaneous emission (SASE) in an ion channel laser (ICL) undulator. Limits and constraints on beam parameters are given, based on theoretical argument and numerical simulations results using the Architect hybrid code. [ABSTRACT FROM AUTHOR] more...

Anomalous wave effects and stimulated charged particle fluxes were registered during 40 kHz-modulated electron beam injection in active space experiment carried out in a double satellite system. To explain these effects, the beam-plasma instability for a two-wave longitudinal interaction has been considered. The growth of instability depends on the frequency and wavenumber detunings between these longitudinal waves one of them is a slow beam mode with negative or zero wave energy defined near the linear stability boundary. [ABSTRACT FROM AUTHOR] more...

Dosimetric properties of the borosilicate glasses (SiO 2 –B 2 O 3 –Al 2 O 3 –CaO–Na 2 O type) doped with Eu 2 O 3 , Gd 2 O 3 and CeO 2 rare earth oxides were investigated as potential materials for e-beam radiation dose measurement purposes. Glasses were prepared by classical melt-quench methodology with varying concentration of rare earth metal oxides from 0.5% to 1.5%. Linear electron accelerator was used for irradiation (17 ns or 4 μs duration pulsed mode). For lower dose range investigated (up to 900 Gy) all samples studied exhibit good dosimetric response vs. dose absorbed, whereas for higher dose range (up to 30 kGy), only materials doped with 0.5% and 1.5% of Gd 2 O 3 , as well as 0.5% CeO 2 doped glasses were able to provide reproducible dosimetric response. Significant dose sensitivity variation was observed for all investigated glasses, which was dependent both on the rare earth metal concentration and the dose rate of radiation used for signal generation. For irradiated 0.5% Eu 2 O 3 , Gd 2 O 3 and CeO 2 doped glasses spectrally-resolved thermoluminescence measurements were performed. Results suggest different traps formation and stabilization mechanisms for each dopant, indicating Eu 3+ →Eu 2+ ions reduction with simultaneous traps number consumption, glass network modification and traps stabilization for Gd 2 O 3 doped glass and direct reduction of Ce 4+ →Ce 3+ with simultaneous glass network disruption and increasing number of low energy traps. All investigated glass samples can be considered as potential dosimetric materials for electron beam delivered dose within the dose range up to 900 Gy and with some limitations, regarding higher doses up to 15 kGy. [ABSTRACT FROM AUTHOR] more...

A retarding field energy analyzer (RFEA) designed specifically for high energy pulsed electron beam measurements is described in this work. By proper design of the entrance grid, attenuation grid, and beam collector, this RFEA is capable of determining the time-resolved energy distribution of high energy pulsed electron beams normally generated under "soft vacuum" environment. The performance of the RFEA is validated by multiple tests of the leakage current, attenuation coefficient, and response time. The test results show that the retarding potential in the RFEA can go up to the same voltage as the electron beam source, which is 20 kV for the maximum in this work. Additionally, an attenuation coefficient of 4.2 is obtained in the RFEA while the percent difference of the rise time of the electron beam pulse before and after attenuation is lower than 10%. When compared with a reference source, the percent difference of the RFEA response time is less than 10% for fall times greater than 35 ns. Finally, the test results of the 10 kV pseudospark-based pulsed electron beam currents collected under varying retarding potentials are presented in this paper. [ABSTRACT FROM AUTHOR] more...

This paper presents a device intended for diagnostics of electron beams and the results obtained with this device. The device comprises a rotating double probe operating in conjunction with an automated probe signal collection and processing system. This provides for measuring and estimating the electron beam characteristics such as radius, current density, power density, convergence angle, and brightness. [ABSTRACT FROM AUTHOR] more...

Computer simulation of irradiation process of various materials with electron beam (EB) can be applied to correct and control the performances of radiation processing installations. Electron beam energy measurements methods are described in the international standards. The obtained results of measurements can be extended by implementation computational dosimetry. Authors have developed the computational method for determination of EB energy on the base of two-parametric fitting of semi-empirical model for the depth dose distribution initiated by mono-energetic electron beam. The analysis of number experiments show that described method can effectively consider random displacements arising from the use of aluminum wedge with a continuous strip of dosimetric film and minimize the magnitude uncertainty value of the electron energy evaluation, calculated from the experimental data. Two-parametric fitting method is proposed for determination of the electron beam model parameters. These model parameters are as follow: E 0 – energy mono-energetic and mono-directional electron source, X 0 – the thickness of the aluminum layer, located in front of irradiated object. That allows obtain baseline data related to the characteristic of the electron beam, which can be later on applied for computer modeling of the irradiation process. Model parameters which are defined in the international standards (like E p – the most probably energy and R p – practical range) can be linked with characteristics of two-parametric model ( E 0 , X 0 ), which allows to simulate the electron irradiation process. The obtained data from semi-empirical model were checked together with the set of experimental results. The proposed two-parametric model for electron beam energy evaluation and estimation of accuracy for computational dosimetry methods on the base of developed model are discussed. [ABSTRACT FROM AUTHOR] more...

The paper reports results of the recent experimental studies of pulsed electron beams and soft X-rays in plasma-focus (PF) experiments carried out within a modified PF-360U facility at the NCBJ, Poland. Particular attention was focused on time-resolved measurements of the fast electron beams by means of two different magnetic analyzers, which could record electrons of energy ranging from about 41 keV to about 715 keV in several (6 or 8) measuring channels. For discharges performed with the pure deuterium filling, many strong electron signals were recorded in all the measuring channels. Those signals were well correlated with the first hard X-ray pulse detected by an external scintillation neutron-counter. In some of the analyzer channels, electron spikes (lasting about dozens of nanoseconds) and appearing in different instants after the current peculiarity (so-called current dip) were also recorded. For several discharges, fast ion beams, which were emitted along the z-axis and recorded with nuclear track detectors, were also investigated. Those measurements confirmed a multibeam character of the ion emission. The time-integrated soft X-ray images, which were taken side-on by means of a pinhole camera and sensitive X-ray films, showed the appearance of some filamentary structures and so-called hot spots. The application of small amounts of admixtures of different heavy noble gases, i.e. of argon (4.8% volumetric), krypton (1.6% volumetric), or xenon (0.8% volumetric), decreased intensity of the recorded electron beams, but increased intensity of the soft X-ray emission and showed more distinct and numerous hot spots. The recorded electron spikes have been explained as signals produced by quasi-mono-energetic microbeams emitted from tiny sources (probably plasma diodes), which can be formed near the observed hot spots. [ABSTRACT FROM AUTHOR] more...

We report on the results of analysis of propagation of an electron beam from a plasma-filled diode in the absence of the metal anode between the regions of beam generation and transportation. The diode parameters are 160 kA, 400 kV, and 50 GW. At a distance exceeding 10 cm behind the generation region, a beam current of 100 kA to the target and an energy density of 20 J/cm are attained for the beam cross-sectional area of about 200 cm. The possibility of varying the beam current and energy density by changing the distance to the target is demonstrated. [ABSTRACT FROM AUTHOR] more...

Experimental investigations have been conducted for the nonlinear dynamical response of a parametrically excited clamped–clamped beam with a central magneto-rheological elastomer (MRE) patch. Experiments have been conducted when the MRE patch was in the absence or presence of an external magnetic field, when the system was parametrically excited either near the fundamental resonance or in the vicinity of the principal parametric resonance; frequency–responses and acceleration-responses were constructed. An electrodynamic shaker parametrically excited each system and the corresponding displacement of the centre of the beam was measured. It has been found that at the fundamental resonance, each system (in the absence or presence of a magnetic field) displays linear behaviour with an internal resonance ; however, at the principal parametric resonance a strong softening-type nonlinearity was observed when there was no externally applied magnetic field to the MRE patch—with increasing magnetic field applied to the MRE patch, the principal parametric resonance displayed a weaker nonlinear behaviour. It has been shown that the MRE patch in the absence or presence of an externally applied magnetic field has a substantial quantitative and qualitative effect on the nonlinear dynamical behaviour of the parametrically excited systems. [ABSTRACT FROM AUTHOR] more...

This paper presents an unsupervised de-blurring technique that enhances the spatial resolution of electron beam (EB) diagnostic instruments. The inherent degradation in EB diagnosis waveforms is modeled using the convolution between the EB current distribution and the sensor characteristic function. Due to the use of various sensors, the diagnosis results are device dependent. Sensor inaccuracy has a detrimental effect on the deconvolution-based restoration of the ground truth signal. In this research this adverse effect is mitigated by an accurate sensor's Point Spread Function (PSF) derivation, which allows the successful restoration of waveforms. As approximate size of the sensor is known, a probability distribution is assigned to the expected interval of PSF features in the frequency domain, which increases the accuracy of the PSF analysis. By deploying this method, sensor inaccuracies are considered in the dynamic PSF formation, hence providing a promising consistency to the restoration. Restoration is performed with Wiener inverse filter and blind-deconvolution and results are compared with the ground truth pulses, obtained using a sensitive sensor (18um diameter). Experimental results confirm that the purposed method delivers a universal device independent measurement, facilitates instrument production, and EB characterization. [ABSTRACT FROM AUTHOR] more...

Protons and neutrons constitute the building blocks of normal matter but despite long investigation we still remain far from understanding the intricacies and mysteries of their inner structure. Jefferson Lab's primary mission is to expand our knowledge of the universe by studying the emergence of nucleons and nuclei and their interactions from the properties and dynamics of quarks and gluons in Quantum Chromo Dynamics (QCD). [ABSTRACT FROM PUBLISHER] more...

In recent years, small-field electron beams have been used for the treatment of superficial lesions, which requires small circular fields. However, when using very small electron fields, some significant dosimetric problems may occur. In this study, dose distributions and outputs of circular fields with dimensions of 5 cm and smaller, for nominal energies of 6, 9, and 15 MeV from the Siemens ONCOR Linac, were measured and compared with data from a treatment planning system using the pencil-beam algorithm in electron beam calculations. All dose distribution measurements were performed using the Gafchromic EBT film; these measurements were compared with data that were obtained from the Computerized Medical Systems (CMS) XiO treatment planning system (TPS), using the gamma-index method in the PTW VeriSoft software program. Output measurements were performed using the Gafchromic EBT film, an Advanced Markus ion chamber, and thermoluminescent dosimetry (TLD). Although the pencil-beam algorithm is used to model electron beams in many clinics, there is no substantial amount of detailed information in the literature about its use. As the field size decreased, the point of maximum dose moved closer to the surface. Output factors were consistent; differences from the values obtained from the TPS were, at maximum, 42% for 6 and 15 MeV and 32% for 9 MeV. When the dose distributions from the TPS were compared with the measurements from the Gafchromic EBT films, it was observed that the results were consistent for 2-cm diameter and larger fields, but the outputs for fields of 1-cm diameter and smaller were not consistent. In CMS XiO TPS, calculated using the pencil-beam algorithm, the dose distributions of electron treatment fields that were created with circular cutout of a 1-cm diameter were not appropriate for patient treatment and the pencil-beam algorithm is not convenient for monitor unit (MU) calculations in electron dosimetry. [ABSTRACT FROM AUTHOR] more...

An experimental method to determine the beam spot size and the acid diffusion length of a positive chemically amplified electron-beam resist (p-CAR) is proposed. This method is applied to a reference p-CAR with a Vistec VB6 electron beam at 100 kV and with a MAPPER tool at 5 kV. Beam spot size characterization is based on the width measurement of a single line exposure. This procedure is applied to two specific dose ranges. In the first one, the chemical mechanism occurring in the exposed resist is dominated by acid catalytic deprotection of a partially protected polymer (standard process). In the second dose range, the chemistry is governed by the cross-linking mechanism due to the intentional overdose of the p-CAR, leading to a polarity inversion. The authors assume that comparing the results obtained with the standard and the cross-linked p-CAR enables the determination of the acid diffusion length of the p-CAR process. This hypothesis was verified with measurements performed with a nonchemically amplified process. A relationship between the best exposure latitudes achieved at 5 and 100 kV and the minimum spot sizes determined with the present method is observed with very high resolution grating exposures. In this work, a suitable method is proposed for fine resist process characterization. [ABSTRACT FROM AUTHOR] more...

Radiation-beam technologies applied for modifying, including those with alloying of surfaces, provide necessary topography of surface, its activation, improvement of adhesion properties, required structure and chemical composition of the surface. These characteristics are further determining in diffusion welding, brazing and deposition of coatings. In the work the low-energy high-current electron beams and high-energy plasma flows for modifying and alloying of the joined surfaces of steels and heat-resistant alloys were used. These types of surface treatment belong to the radiation-beam technologies. The treatment was carried out using low-energy high-current electron beams in vacuum 10-2 Pa in the installation SOLO of the Institute of High Current Electronics of the SB RAS, and also high-energy plasma flows using magnetic plasma compressor of a compact geometry of the Belarusian State University at the pressure of hydrogen and nitrogen of 3.102 Pa, and welding and brazing were performed in the installation UDSV-DT in vacuum of 10-2 Pa or super-high vacuum universal technological complex VVU-1D in vacuum of 10-5 Pa. Independently of metals being investigated the formation of sub-microcrystalline structure, presence of high density of dislocations (up to 1011 cm-2), appearance of stresses of the 3rd kind, being the evidence of immense increase in level of energy accumulated in modified layer, are characteristic for all the modified layers. The surfaces of heat-resistant nickel alloys were alloyed by zirconium and hafnium, which are the most challenging depressants of nickel brazing alloys. For this purpose the layers of alloying element of 1-3 μm thickness was deposited on the surface using method of ion-plasma spraying and then the surface layer was remelted using low-energy high-current electron beams and high-energy plasma flows. The investigations of processes of formation of modified and alloyed surfaces showed the possibility of efficient control of structure and composition of the modified layer. Diffusion welding in a solid state and with a melting interlayer provides the high quality of joints, which can be confirmed by the structures and mechanical properties of joints. The application of radiation-beam technologies allows expanding the capabilities of joining metals and hardening the materials. [ABSTRACT FROM AUTHOR] more...

Analysis of quadrupole focusing lattices for high-frequency traveling-wave tubes is presented. This paper is motivated by recent work performed at the Naval Research Laboratory which demonstrated an advantageous case for strong focusing employing a Halbach quadrupole lattice. Using realistic permanent magnet quadrupole (PMQ) field cancellation, the advantage of using PMQ to transport higher current densities than a permanent periodic magnet disappears, while other advantages for employing quadrupole focusing remain. [ABSTRACT FROM AUTHOR] more...

In this paper, the cold-fluid model theory of an intense sheet electron beam is developed to investigate the diocotron instability during its transport in a uniform magnetic field. The model shows that if the magnetic field strength and the beam filling factor are increased separately, the diocotron instability will be suppressed, which extends the sheet-beam transport distance effectively. To verify the above conclusion, a set of complicated instruments, the electron beam measuring and analyzing system (EBMAS), was developed to measure the beam cross section, beam current density, and the 3-D trajectory. The sheet electron beam transport process in a uniform magnetic field with its diocotron instability is investigated on the basis of EBMAS measurements. The measured results agree very well with theoretical calculation and numerical simulation. A sheet-electron-beam tube based on a uniform magnetic field was then manufactured to drive a future W-band sheet-beam klystron (WSBK). Tuning the sheet-beam parameters over a broad range, including a cathode voltage range of 20–82 kV, current range of 0.5–4.27 A, and with a beam cross section of about 10 mm $\times\,$ 0.5 mm, the experimental beam transmission rate is above 98% through a beam tunnel of 100 mm in length. [ABSTRACT FROM AUTHOR] more...

Abstract: Two-photon absorption of 1560nm light was used to generate polarized electron beams from unstrained GaAs photocathodes of varying thickness: 625μm, 0.32μm, and 0.18μm. For each photocathode, the degree of spin polarization of the photoemitted beam was less than 50%, contradicting earlier predictions based on simple quantum mechanical selection rules for spherically-symmetric systems but consistent with the more sophisticated model of Bhat et al. (Phys. Rev. B 71 (2005) 035209). Polarization via two-photon absorption was the highest from the thinnest photocathode sample and comparable to that obtained via one-photon absorption (using 778nm light), with values 40.3±1.0% and 42.6±1.0%, respectively. [Copyright &y& Elsevier] more...

In this paper, we observe the interaction of the electromagnetic wave with high-speed electrons arising from the corona and spark discharges in the cavity. With the low level of the high-speed electron in the cavity, the initial frequency set by the cavity is being split mainly into a lower and higher frequency in comparison to the initial frequency. With the high level of the high-speed electron in the cavity, the system yields a good microwave generation in air at the single frequency, even at low voltages. The high level of the high-speed electrons is due to the corona discharges that are producing in situ generated electron beams on the helix, which is made of copper wire that is 1.25 mm in diameter. Two models are presented to account for the waveform of the radiation and its FFT. [ABSTRACT FROM PUBLISHER] more...

This paper presents new experimental data on the generation of runaway electron beams and X-rays in repetitively pulsed discharges in helium and air with an inhomogeneous electric field. Both negative and positive voltage pulses of duration 1–5 ns and amplitude in the incident wave up to 18 kV were applied to a “tube-to-plane” gap at a pulse repetition frequency of up to 1 kHz. It is shown that at a helium pressure of several and tens of torrs, whatever the polarity of the main voltage pulse, an electron beam is generated on arrival of reflected negative voltage pulses in the gap. X-rays were detected over a wide pressure range of helium and air, including atmospheric pressure. The breakdown of atmospheric-pressure air gaps with a special cathode design at a rate of voltage rise of 10^14~V/s was studied with subnanosecond and picosecond time resolution. At a voltage amplitude higher than 100 kV, a fast electron beam in atmospheric-pressure air was detected in the space downstream of the cathode, which was made of thin wires arranged parallel to a thin flat foil. The current of the fast electron beam downstream of the cathode depended strongly on the anode material. [ABSTRACT FROM AUTHOR] more...

We present investigation of the influence of cascade emission to the formation of spectra from plasma created by electron beam ion trap (EBIT) in electron trapping mode. It has been shown that cascade emission can play an important role in the formation of spectra from the EBIT plasma. Process of the cascade emission takes place when ion having cycloidal orbit leaves electron beam where coronal approximation is applicable. Thus both processes – excitation from ground or metastable levels and cascade emission – take part in the population of levels. Demonstration is based on the investigation of W 13 + spectra. The present investigation helps to resolve long-standing discrepancies; in particular, the present structure of W 13 + spectra is in good agreement with measurements on electron beam ion trap. Lines in the experimental spectra are identified as 4 f 13 5 s 5 p → 4 f 13 5 s 2 and 4 f 12 5 s 5 p 2 → 4 f 12 5 s 2 5 p transitions from Dirac-Fock-Slater calculations. [ABSTRACT FROM AUTHOR] more...

The initial Kapitza-Dirac effect for crossing energetic electron beams with laser beams had been generalized for quantum modulation of the electrons. The recent developments provide advanced insights with the initial experimental facts, where consequences are leading to results about non-resonant laser interaction with condensed media including nonlinearities with applications to quantum 1/f noise theory in electronic devices. [ABSTRACT FROM AUTHOR] more...

A novel scanning electron microscope (SEM)-based method for making localised measurements of DC capacitance in a moderately insulating electroceramic, based on the decay of a locally injected current, is presented. A sample of BiFeO, with a room temperature conductivity of the order of 70 MΩm was used as a model system. Measurements were made with the aid of two closely-spaced surface micro-electrodes, each 80 μm square. During the measurement the SEM beam impinged on one electrode, while the other was used to measure the specimen current. The specimen current decay profile was characterised after blanking the incident electron beam, allowing the decay time constant to be established. Specimen currents in the range 0.1-10 nA were used. The potential difference between the electrodes was also measured as a function of beam conditions, so that the local resistance and capacitance could be established. A local capacitance of the order of 10 F was measured between the electrodes. The capacitance was found to depend on the magnitude of the initial current and is interpreted in terms of the behaviour of a space-charge layer formed below the electrodes. [ABSTRACT FROM AUTHOR] more...

Traditionally process plasmas are often studied and monitored by optical emission spectroscopy. Here, the authors compare experimental measurements from a secondary electron beam excitation and direct process plasma excitation to discuss and illustrate its distinctiveness in the study of process plasmas. They present results that show excitations of etch process effluents in a SF6 discharge and endpoint detection capabilities in dark plasma process conditions. In SF6 discharges, a band around 300 nm, not visible in process emission, is observed and it can serve as a good indicator of etch product emission during polysilicon etches. Based on prior work reported in literature the authors believe this band is due to SiF4 gas phase species. [ABSTRACT FROM AUTHOR] more...

We report on the measurement and computer simulation of the divergence of fast electrons generated in an ultraintense laser-plasma interaction (LPl) and the subsequent propagation in a nonrefluxing target. We show that, at Iλ2 of 1020 Wcm-2 μm2, the time-integrated electron beam full divergence angle is (60 ± 5)°. However, our time-resolved 2D particle-in-cell simulations show the initial beam divergence to be much smaller ≤30°). Our simulations show the divergence to monotonically increase with time, reaching a final value of (68 ± 7)° after the passage of the laser pulse, consistent with the experimental time-integrated measurements. By revealing the time-dependent nature of the LPI, we find that a substantial fraction of the laser energy (∼7%) is transported up to 100 μm with a divergence of 32°. [ABSTRACT FROM AUTHOR] more...

Abstract: The measurement and analysis of high power electron beam during its formation and transmission are the basic scientific problems and key techniques for the development of high performance microwave vacuum electron devices, which are widely used in the fields of military weapon, microwave system and scientific instruments. In this paper, the dynamic parameters measurement and analysis system being built in Institute of Electronics, Chinese Academy of Sciences (IECAS) recently are introduced. The instrument are designed to determine the cross-section, the current density, and the energy resolution of the high power electron beam during its formation and transmission process, which are available both for the electron gun and the electron optics system respectively. Then the three dimension trajectory images of the electron beam can be rebuilt and display with computer controlled data acquisition and processing system easily. Thus, much more complicated structures are considered and solved completely to achieve its detection and analysis, such as big chamber with 10-6Pa high vacuum system, the controlled detector movement system in axis direction with distance of 600mm inside the vacuum chamber, the electron beam energy analysis system with high resolution of 0.5%, and the electron beam cross-section and density detector using the YAG: Ce crystal and CCD imaging system et al. At present, the key parts of the instrument have been finished, the cross-section experiment of the electron beam have been performed successfully. Hereafter, the instrument will be used to measure and analyze the electron beam with the electron gun and electron optics system for the single beam and multiple beam klystron, gyrotron, sheet beam device, and traveling wave tube etc. thoroughly. [Copyright &y& Elsevier] more...

Abstract: A new plunger device for Recoil-Distance Doppler Shift and Time-Differential Recoil-In-Vacuum measurements has been developed at the CSNSM in collaboration with the IPN Orsay. It is conceived to be easily adapted to different experimental setups and facilities, in particular to the future radioactive beam facility Spiral2. An electronic feedback system keeping the distance between target and stopper foils constant, imperative for precision measurements of short lifetimes, was also developed. The plunger device was commissioned with an experiment performed at the IPN Orsay Tandem accelerator laboratory using the Orgam germanium detector array. Excited states in 76Kr were populated using the reaction 45Sc(35Cl,2p2n)76Kr. The lifetime of the state was determined to 4.3(6)ps, in accordance with previous measurement, confirming the functionality of the new plunger device. The commissioning experiment showed in particular that the electronic feed back system works as foreseen. [Copyright &y& Elsevier] more...

Abstract: MIRRORCLE is a tabletop synchrotron light source being investigated within an EC funded project named LABSYNC. To evaluate the potential of this novel x-ray source for medical imaging applications, a set of measurements was performed at the MIRRORCLE factory in Japan. In particular, the aim of this work was to characterize the proposed compact x-ray source by determining different parameters, such as the intensity of the broad spectra produced with thin wire targets, the size of the focal spot and its distribution. The average electron-beam impact current on wire targets was calculated by several methods and it was demonstrated to be in the range . By comparing these values with data available for conventional x-ray tubes, the current needed to achieve the same fluence as in a standard diagnostic examination was estimated to be about 0.1–0.5mA. Finally, results from the measurements of the electron-beam impact cross-section on the target suggested that the diameter of the electron beam circulating in the storage ring is about 6mm. [Copyright &y& Elsevier] more...