High-intensity Electron Beam Research Articles

Design and development of vacuum system for electron beam powder bed fusion process

A vacuum system is one of the crucial components of the Electron Beam-Powder Bed Fusion Process (EB-PBF). It ensures the generation of a high-intensity electron beam. This paper presents a vacuum system design for the EB-PBF process. The work chamber and EB gun chamber have been designed and verified using ANSYS workbench for stress, strain, and deformation limits and found satisfactory. The analytical calculations have been performed for all the pumps, considering the various gas loads during the process. After the design, the vacuum system has been fabricated and tested for its stability, ultimate vacuum, and leak rate. The helium leak test results show that all the joints have a leak rate better than 1 × 10−8 mbar l/s. Further, the analytical results of each pump have been compared with experimental results and found almost in line with the theoretical results. The results show that a pressure lower than 1 × 10−5 mbar and 5 × 10−6 mbar can be achieved in the work chamber and EB gun chamber in less than 23 min and 10 min respectively. The chamber was evacuated multiple times and found that the chamber could still hold pressure better than 1 × 10−2 mbar after 48 h.

From bremsstrahlung to channeling radiation a promising way for positron generation

For a long time the necessity of having intense positron beams to get a high rate of events with fixed targets as with e+e− collisions, led to conventional positron sources using high energy and high intensity electron beams generating bremsstrahlung photons in thick high Z targets. The inconveniences for such scheme, heat load and large emittance, are underlined. Alternative ways aiming to provide a high number of photons impinging on rather thin conversion targets have been developed: they are using magnetic undulators, laser Compton backscattering and channeling radiation in axially oriented crystals. A brief description of these methods is given. However, the emphasis is put here on the channeling radiation. The advantages of channeling radiation, described by M.Kumakhov and others, were confirmed by many simulations and experiments. We are reporting, hereafter, on two schemes: positron all-crystal converters involving thick crystals where photon radiation and e+e− pair creation are occurring in the crystal and hybrid sources where the two functions are separated. With the hybrid scheme, including a thin crystal-radiator and a thick amorphous-converter, the heat load and the local deposited energy density can be lowered. Simulations and experiments related to these two schemes are reported. Further developments concerning the converter, granular instead of bulk, are providing additional advantages. The promising, already gathered results led to consider these kinds of positron sources for future e-e+ colliders. More physicists, from different laboratories, concerned by the studies on positron sources are now contributing in this field.

Effects of a High-Intensity Electron Beam on Antibiotic in Aqueous Solution

Effects of a High-Intensity Electron Beam on Antibiotic in Aqueous Solution

Concept of Very-Asymmetric lepton Collider for dark matter search

Accelerator-based searches for dark matter are aiming for high sensitivity and need an experimental setup with high luminosity. This field of research is often called intensity frontier physics. One of the best motivated portals of interaction between dark matter and ordinary matter is a dark photon which could be observed as a resonance in the invariant mass of the decay products. Electron–positron collisions are known to be the cleanest interaction for such a study. In this paper we propose a scheme for a collider which allows for a luminosity of a few orders of magnitude higher than could be obtained in a conventional symmetric collider and with a few times higher accessible mass than is possible using a positron beam and a fixed target approach. The key concept is based on asymmetric energies: a high-energy circulating positron beam and a low-energy high-intensity electron beam, and optimization of the beam interaction region. We present here a configuration of a collision region of 10 MeV electron and 4 GeV positron beams.

Coupling Design of Combined Function Bending Magnet and High Current Electron Beam for 100 kW Irradiation Accelerator

RF system is one of the key components of a 2 GeV, 6 MW high power fixed field alternating gradient (FFAG) accelerator being designed at China Institute of Atomic Energy (CIAE). In order to verify the design principle and the engineering feasibility, a scaled-down RF cavity is under construction, which can also be used as the main accelerating cavity for a 100 kW electron irradiation accelerator. By the deflections of several 180 degrees bending magnets, the electrons emitted from the electron gun can pass the cavity for multiple times. Due to the limited length of the cavity, the deflection radius should be as small as possible to ensure more acceleration times and consequently higher beam power, which will make the fringe field effect of the bending magnet be a problem. In addition, the bending magnet should provide beam focusing in both the radial and axial directions of the beam and keep the beam envelope stable during the whole acceleration process. Based on the above reasons, the parameters of the combined function bending magnet, such as the pole face rotations (Liu, 1994), magnetic field gradient and shielding distance, have a great influence on the beam dynamics behavior in the accelerator, which bring great difficulty to the design of the combined function bending magnet. In this paper, the coupling design of the bending magnet with focusing function and the high intensity electron beam for this 100 kW irradiation accelerator will be illustrated in detail.

Lanthanoid-doped quaternary garnets as phosphors for high brightness cathodoluminescence-based light sources

Gadolinium-yttrium- aluminum-gallium garnets (GYAGG) doped and codoped with Eu, Tb, and Ce were manufactured as ceramics to develop long-wavelength phosphors for high-brightness white light sources based on cathodoluminescence (CL). The CL light yield (LY) of Tb-doped ceramics at high-intensity electron beam excitation is shown to be more than twice as high as that of the conventional phosphor YAG:Ce, whereas codoping with Eu to redshift the chromaticity results in reducing the LY approximately to the level of YAG:Ce. The LY might be substantially improved by using a mix of Tb- and Eu-doped GYGAG powders instead of a single codoped GYGAG to produce ceramic phosphor. The high LY is explained by favorable contribution of Gd sublattice in excitation transfer to activator ions. Chromaticity of phosphors GYGAG:Tb, Eu can be tuned in a wide range by varying the ratio of Tb to Eu concentration. They are radiation resistant and stabile in the temperature range from 300 to 450 K.

Oxidation behavior of TiCr and TiMo alloys formed by low-energy pulsed electron beam impact

The titanium-based alloys with 2–3 at.% of chromium (TiCr) and molybdenum (TiMo) were produced on the top of titanium samples by means of the high-intense pulsed electron beam impact on the titanium with preliminary deposited Cr and Mo coatings. The TiCr and TiMo alloys were subjected to oxidation in open air atmosphere at temperature 600 °C. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-disperse X-ray microanalysis (EDX) were used for structure and elemental composition determination in the samples. The analysis of oxygen depth profiles showed the increase in oxygen penetration depth in the case of TiCr alloy in comparable to pure titanium. The oxygen concentration corresponding to stoichiometry of the oxide phase TiO2 was found on the depth equaled to the thickness of the TiCr alloy that shows the enhancement of the diffusion of oxygen in the modified layer. The diffusion of oxygen at the temperature of 600 °C is enhanced by decomposition of the solid solutions based on bcc β-Ti phase with free chromium and molybdenum atoms releasing. The free molybdenum atoms take part in the stabilization of TiO2 anatase phase while the free chromium atoms form intermetallic compound TiCr2 preventing the sample from oxidation.

Experimental Tests of CW Resonance Accelerator With 7.5 MeV High Intensity Electron Beam

Experimental Tests of CW Resonance Accelerator With 7.5 MeV High Intensity Electron Beam

Operation and characterization of a windowless gas jet target in high-intensity electron beams

A cryogenic supersonic gas jet target was developed for the MAGIX experiment at the high-intensity electron accelerator MESA. It will be operated as an internal, windowless target in the energy-recovering recirculation arc of the accelerator with different target gases, e.g., hydrogen, deuterium, helium, oxygen, argon, or xenon. Detailed studies have been carried out at the existing A1 multi-spectrometer facility at the electron accelerator MAMI. This paper focuses on the developed handling procedures and diagnostic tools, and on the performance of the gas jet target under beam conditions. Considering the special features of this type of target, it proves to be well suited for a new generation of high-precision electron scattering experiments at high-intensity electron accelerators.

Modification of high-entropy alloy AlCoCrFeNi by electron beam treatment

In this study, a high-entropy alloy (HEA) of Al–Co–Cr–Fe–Ni system was fabricated via wire-arc additive manufacturing technology (WAAM) in the atmosphere of pure Ar followed by high-intensity electron beam treatment. SEM, TEM, and X-ray diffraction methods were used to characterize the manufactured material's microstructure. The HEA has the following composition: Al (36.5 at. %), Ni (33.7 at. %), Fe (16.4 at. %), Cr (8,6 at. %) and Co (4.9 at. %). The obtained material without electron beam treatment has a polycrystalline structure with a grain size of 4–15 μm. Bulks of grains are enriched in Al and Ni, while grain boundaries contain Cr and Fe. Co is quasi-uniformly distributed in the crystal lattice of the manufactured HEA. The ultimate material strength in testing for compression depends on production mode and varies within the interval from 652 to 1899 MPa. The HEA wear parameter amounts to 1.4∙10−4 mm3/N∙m, friction coefficient - 0.65. In testings for tension, the material failure occurred by the mechanism of intragrain cleavage. The formation of brittle cracks along boundaries and in grain boundary junctions, i.e. in sites containing the inclusions of second phases, is revealed. The HEA's irradiation by a pulsed electron beam with the energy density of 10–30 J/cm2 (pulse duration 200 μs, number of pulses 3) results in material homogenization, decreased crystal lattice microdistortions, and an increase in sizes of coherent scattering regions. High-velocity crystallization of the molten surface layer of HEA samples is accompanied by columnar structure formation having a submicro-nanocrystalline structure.

The Effect of High-Intensity Electron Beam on the Crystal Structure, Phase Composition, and Properties of Al–Si Alloys with Different Silicon Content

The study deals with the element–phase composition, microstructure evolution, crystal-lattice parameter, and microdistortions as well as the size of the coherent scattering region in the Al–10.65Si–2.11Cu and Al–5.39Si–1.33Cu alloys irradiated with the high-intensity electron beam. As revealed by the methods of x-ray phase analysis, the principal phases in untreated alloys are the aluminium-based solid solution, silicon, intermetallics, and Fe2Al9Si2 phase. In addition, the Cu9Al4 phase is detected in Al–10.65Si–2.11Cu alloy. Processing alloys with the pulsed electron beam induces the transformation of lattice parameters of Al–10.65Si–2.11Cu (aluminium-based solid solution) and Al–5.39Si–1.33Cu (Al1 and Al2 phases). The reason for the crystal-lattice parameter change in the Al–10.65Si–2.11Cu and Al–5.39Si–1.33Cu alloys is suggested to be the changing concentration of alloying elements in the solid solution of these phases. As established, if a density of electron beam is of 30 and 50 J/cm2, the silicon and intermetallic compounds dissolve in the modified layer. The state-of-the-art methods of the physical materials science made possible to establish the formation of a layer with a nanocrystalline structure of the cell-type crystallization because of the material surface irradiation. The thickness of a modified layer depends on the parameters of the electron-beam treatment and reaches maximum of 90 µm at the energy density of 50 J/cm2. According to the transmission (TEM) and scanning (SEM) electron microscopy data, the silicon particles occupy the cell boundaries. Such changes in the structural and phase states of the materials response on their mechanical characteristics. To characterize the surface properties, the microhardness, wear parameter, and friction coefficient values are determined directly on the irradiated surface for all modification variants. As shown, the irradiation of the material surface with an intensive electron beam increases wear resistance and microhardness of the Al–10.65Si–2.11Cu and Al–5.39Si–1.33Cu alloys.

Electron dynamics for high-intensity hollow electron beams

Hollow Electron Lenses (HEL) will be installed at the High Luminosity Large Hadron Collider to provide a continuous and controlled depletion of beam halo particles by interaction with a superimposed hollow electron beam, of intensity as high as 5 A, and radii 1.1–2.2 mm for 7 TeV LHC operations. In this paper, issues related to the propagation of high intensity hollow electron beams are discussed and the simulations of the electron beam dynamics with feedback to the HEL design are presented. The main results are the rise of the electron beam accelerating voltage from 10 kV, as in the initial proposal, to 15 kV and the validation of the 5 T magnetic field at the main solenoids as being sufficient to guarantee a stable electron beam.

Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC)

Electrons lenses produce a high-intensity electron beam and have a variety of applications to circular hadron accelerators. Electron beams of different transverse cross sections and distributions may be designed, depending on the desired application, and they are produced and steered along the orbit of the hadron beam, overlapping with it for typical distances of a few meters before being deflected away and disposed of. Hollow electron beams find applications to high-intensity beam collimation for machines like the CERN Large Hadron Collider (LHC). Such devices can be integrated in a collimation system to improve the halo-cleaning performance through an active control of the halo dynamics: the annular distribution of the electrons excites resonantly the beam tails surrounding the beam core, while the core itself remains unperturbed, as ideally it only “sees” the field-free “hole” in the electron distribution. Hollow electron lenses are part of the upgrade baseline of the High-Luminosity project of the LHC (HL-LHC) and will be installed in the machine during a long shutdown in 2025–2027 to mitigate effects from beam losses so to improve the collimation system performance. This paper describes the hollow electron lens project within the HL-LHC collimation upgrade.

Application of a drift compensation low-level radio frequency system based on time-multiplexing pick-up/reference signals.

The high accuracy, low drift low-level radio frequency (LLRF) system is essential for the long-term stability of the accelerator RF and the acquirement of low emittance, high intensity electron beams. A time-multiplexing pick-up/reference signal based LLRF system is proposed to deal with the component temperature related phase drift and has been deployed and applied at the Xi'an Gamma-ray Light Source (XGLS) injector. The long term dual-receiver out-of-loop stability experiments with a continuous wave laser based phase reference distribution system (PRDS) show that the LLRF system can achieve ∼40 fs Root-Mean-Square (rms) phase accuracy and 51 fs/52 fs peak-peak drift (in 7 days/17 h with the high power RF system, respectively) while the reference phase varies both ∼30 ps. An ∼4 h beam-based experiment has also been conducted to evaluate the overall performance of the whole XGLS timing and synchronization system, which shows that the PRDS, LLRF system, high power RF system, and laser oscillator laser-RF synchronization system can keep long-term phase stability.

Fatigue-Induced Evolution of AISI 310S Steel Microstructure after Electron Beam Treatment.

Research was carried out to explore the effect of pulsed electron beam irradiation on the behavior of structure and phase state in AISI 310S steel exposed to high-cycle fatigue. A 2.2 times increase in the fatigue life of samples irradiated by electron beams was revealed. The outcomes of scanning and transmission electron microscopic studies suggest the most probable reason for the fracture of steel samples irradiated by a high-intensity electron beam to be microcraters originating on a treated surface and acting as stress risers initiating the propagation of microcracks. The irradiation with a pulsed electron beam causes extremely fast melting of the surface. As a result of the subsequent rapid crystallization, a polycrystalline structure nearly twice as small as an average grain in the untreated steel is formed. Since a surface layer crystallizes rapidly, crystallization cells ranging from 120 to 170 nm develop in the volume of grains. The fatigue testing is shown to be associated with a martensite transformation γ ⇒ ε in the surface layer. One option to intensify a fatigue life increase of the steel in focus is supposed to be the neutralization of crater-forming on a surface treated by electron beams.

Liquid-phase boriding of high-chromium steel

Using the methods of modern physical materials science, structuralphase states and tribological properties of 12Kh18N10T steel, subjected to electroexplosive alloying with titanium and boron and subsequent electron-beam processing in various modes depending on electron beam energy density, exposure pulse duration and their quantity have been analyzed. It has been established that electroexplosive alloying of steel with titanium and boron leads to formation of surface layer with multiphase submicro-nanocrystalline structure, characterized by presence of micropores, microcracks, and microcraters. Complex processing, combining electroexplosive alloying and subsequent irradiation with high-intensity pulsed electron beam, leads to formation of 60 μm thick multiphase submicro-nanocrystalline surface layer. It is shown that phase composition of surface layer of steel is determined by mass ratio of titanium and boron during electroexplosive alloying. Microhardness of modified layer is defined by relative mass fraction of titanium borides in surface layer and can be more than 18 times higher than microhardness of steel in its initial state (before electroexplosive alloying). Modes of complex processing have been determined at which surface layer containing exclusively titanium borides and intermetallic compounds based on titanium and iron is formed. The maximum (approximately 82 % by weight) titanium boride content is observed when steel is processed at regime with the highest mass of boron powder in the sample (mB = 87.5 mg; mTi /mB = 5.202). With decrease in mass of boron powder, relative content of borides in surface layer of steel decreases. It was found that integrated processing of steel is accompanied by sevenfold increase in microhardness of surface layer, wear resistance of steel increases by more than nine times.

CALIBRATION OF A SHOWER LEAD-SCINTILLATION SPECTROMETER BY COSMIC RADIATION

The results of calibration by cosmic muons of a shower lead-scintillation spectrometer of the sandwich type designed to work in high-intensity photon and electron beams with an energy of 0.1 - 1.0 GeV are presented. It was found that the relative energy resolution of the spectrometer depends on the angle of entry of cosmic muons into the spectrometer in the vertical plane and does not depend on the angle of entry in the horizontal plane. The relative energy resolution of the spectrometer was 16%. Placing an additional lead-scintillation assembly in front of the spectrometer improved the relative energy resolution of the spectrometer to 9%.

Study thermodynamic assessment of the B-C and B-Si binary systems with swift heavy ions and high intense electron beam irradiation at the low temperature

B4C and B6Si samples have been irradiated by using swift heavy ions and high intense electron beam. Ion irradiation of the samples was carried at the different electron fluences [Formula: see text], [Formula: see text] and [Formula: see text] cm[Formula: see text] ion/cm2, and energy of ions flux 167 MeV. Also, the samples were irradiated with high energy electron beams at the linear electronic accelerator at different electron fluencies up to [Formula: see text] cm[Formula: see text] and energy of electron beams 2.5 MeV and current density of electron beams [Formula: see text]s. The unirradiation and irradiation of the thermodynamic kinetics of samples at low-temperature change with a differential mechanism. In the DSC curves, at the low temperature for unirradiation and irradiation, boron carbide and boron silicide samples do not undergo phase transition. But at the [Formula: see text] K temperature range, the thermodynamic mechanism of ions and electron beam irradiation are very difficult and measuring the temperature of conductivity, thermal conductivity, calibration factor, specific heat capacity becomes more complicated.

Thermophysical behavior of boron nitride and boron trioxide ceramics compounds with high energy electron fluence and swift heavy ion irradiated

We report differential scanning calorimetry (DSC) studies of boron nitride and boron trioxide compounds under different irradiation conditions. In the present work, boron nitride (h-BN) (purity of 99.8% and density of 2.29 g/cm3) and boron trioxide (B2O3) (purity of 99.5% and density of 3.10 g/cm3) samples were irradiated by using high intense electron beam and swift heavy ions irradiation. Electron beam irradiation of the samples was carried out at the different electron fluence of 4.16 × 1016, 1.20 × 1017 and 1.03 × 1018 cm−2 with energy of 2.5 MeV. Whereas the swift heavy ion irradiation of the samples was carried out using 132Xe ions with energy of 167 MeV/u at the different fluence of 5 × 1012, 5 × 1013 and 3.83 × 1014 ion/cm2. The thermal parameter changes with a differential mechanism under different irradiation conditions were investigated. In the DSC curves at the low temperature for initial and irradiation samples do not undergo phase transitions. However, at the 100 ≤ T ≤ 300 K temperature range widely changed the mechanism of the heat flow rate, specific heat capacity and thermodynamic functions in the boron nitride and boron trioxide samples is a more completed. In addition, for each of irradiation fluences, the calculated thermodynamic functions and specific heat capacity was found to increase from 0.002 J/g‧K to 0.08 J/g‧K as the irradiation electron fluence increased. For swift heavy ion irradiation, the specific heat capacity was found to increase from 0.005 J/g‧K to 0.06 J/g‧K. The results have revealed that there was a thermodynamic change.

A versatile and compact high-intensity electron beam for multi-kGy irradiation in nano- or micro-electronic devices

A compact low-energy and high-intensity electron source for material aging applications is presented. A laser-induced plasma moves inside a 30 kV diode and produces a 5 MW electron beam at the anode location. The corresponding dose that can be deposited into silicon or gallium samples is estimated to be 25 kGy per laser shot. The dose profile strongly depends on the cathode voltage and can be adjusted from 100 nm to 1 μm. With this versatile source, a path is opened to study micro- or nano-electronic components under high irradiation, without the standard radioprotection issues.