Thermal Electron Research Articles

Performance evaluation of different types of surfactants to inhibit clay swelling during chemical enhanced oil recovery

AbstractIn most cases, sandstone reservoirs contain clay particles. When a fluid with low salt content is injected into the reservoir, clay particles swell, and the rock's permeability decreases. Since surfactant flooding with water that has lower salinity than formation water is used to improve oil recovery, this study examines the swelling inhibitive strength of various surfactants. The study investigates the effect of surfactants on clay swelling inhibition through linear swelling and sedimentation experiments which showed that cetyl trimethyl ammonium bromide (CTAB) inhibits clay swelling. The optimum CTAB concentration was found to be 1 wt.%. However, sodium dodecyl sulphate (SDS) and Triton X‐100 (TX‐100) did not inhibit clay swelling. Sandpack experiments confirmed that CTAB prevented clay swelling and sandpack permeability reduction, while SDS and TX‐100 did not. The injection pressure results for the different surfactants were as follows: CTAB—39 psi, SDS—203 psi, TX‐100—223 psi, deionized water (DW)—324 psi, and KCl—78 psi. The mechanism of surfactant performance in affecting clay swelling was investigated based on thermal gravimetric analysis (TGA), zeta potential, and scanning electron microscope (SEM) images. The results showed that CTAB compensates for the surface charge of clays through a cation exchange mechanism. The amount of absorbed water for clays modified with CTAB was lower than that for other surfactants. The SEM images confirmed that the CTAB‐modified clays were larger and did not disintegrate during dispersion; however, in other cases, the particle size was smaller.

Runaway electron mitigation with pulsed localized vertical magnetic field perturbation in ADITYA tokamak

To reduce the risk of severe damage to the vessel and inner peripherals of any tokamak and its safe operation, a robust technique for the mitigation of runaway electrons (REs) is required. The REs in ADITYA tokamak are effectively mitigated by an application of local vertical magnetic field (LVF) perturbation. The LVF perturbation is applied using a pair of electromagnetic coils placed at the top and bottom of the ADITYA vacuum vessel in a Helmholtz configuration at one toroidal location. Powered by a capacitor bank power supply, these coils can produce a localized vertical magnetic field at the plasma center in the range of ∼150 G–260 G for a variable duration of 5–20 ms. The LVF pulse is first applied at the breakdown/current-ramp phase, where the REs are generated in the discharges initiated by the conventional ohmic breakdown in ADITYA. With the application of LVF pulse the REs are significantly reduced as indicated by the reduction in the REs generated hard x-ray flux. It has been observed that to extract the REs efficiently, an LVF pulse of magnitude at least ∼1% of the toroidal magnetic field with a minimum duration of ∼5 ms should be applied. The LVF perturbation is applied at different times into the discharge, i.e. during the breakdown/current ramp-up phase and current flat-top phase. The REs are significantly reduced in all the phases and improved discharge consistency. The LVF acts as an error field and a short-pulse of the LVF influences the REs more in comparison to the thermal electrons due to the faster velocities of the REs.

Thermal and morphological properties of polyhydroxyalkanoate/ nanosilver composite

Conventional plastic can lead to endless pollution as it took millions of years to be disposed of, hence an alternative to using biodegradable plastic replacing regular everyday plastic has highly participated. Polyhydroxyalkanoates (PHA) have the characteristics of a biodegradable plastic however, it exhibits low heat distortion temperature. The objective of this research is to investigate the effect of nanosilver additions on the thermal properties of the PHA composite and its morphology behavior. Initially,4 wt/v of PHA was dissolved into 30mL dichloromethane at room temperature. After that, the nanosilver particle was added with 10mL dichloromethane and it was ultrasonicated at 10 minutes. Ultrasonicated nanosilver in dichloromethane mixture was mixed with PHA in dichloromethane for 20 minutes using a magnetic stirrer. Then, thin polymeric films with a thickness of 10 µm were obtained by the solution casting method. The obtained films were then carefully dried at room temperature for 24 hours. These steps were repeated with the addition of 0.25 wt% and 0.5wt% nanosilver suspension in dichloromethane to PHA solution. The thermal properties and morphology analysis of PHA/nanosilver composite will be investigated using thermal gravimetric analysis(TGA) and field emission scanning electron microscopy (FESEM). Based on thermal properties, PHA/0.5wt% nanosilver has shown a lower onset temperature compared to the pure PHA. This indicates that PHA/0.5wt% nanosilver has a slower degradation rate and higher thermal stability. In conclusion, nanosilver has greatly improved PHA properties into promising biodegradable plastics.

Distance of PSR B0458+46 indicated by FAST H i absorption observations

ABSTRACT The pulsar B0458+46 was previously believed to have a distance of about 1.3 kpc and to be associated with a nearby supernova remnant, SNR HB9 (G160.9+2.6). We observe the neutral hydrogen (H i) absorption spectrum of PSR B0458+46 by using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), and detect two absorption lines at radial velocities of VLSR = −7.7 and −28.1 km s−1. Based on the Galactic rotation curve with a modification factor correcting for the systematic stream in the Galactic anticentre region, we derive the kinematic distance of the farther absorption cloud, which is found to be located $2.7^{+0.9}_{-0.8}$ kpc away, just beyond the Perseus Arm. We also obtain a direct distance estimation of the farther absorption cloud as being $2.3_{-0.7}^{+1.1}$ kpc, based on a comparison of the velocity with the H i emission in the Perseus and Outer Arms that was well-defined by recently measured parallax tracers. As a result, we conclude that PSR B0458+46 should be located beyond the Perseus Arm, with a lower limit for the distance at 2.7 kpc, and therefore not associated with SNR HB9. The doubled distance indicates a deficiency of thermal electrons in the immediate outer Galaxy, with a much less density than current models predict. Additionally, we detect a new high-velocity H i cloud in the direction of this pulsar.

An Experimental Study of Dislocation Dynamics in GaN.

The dynamics of dislocations introduced through indentation or scratching at room temperature into a few GaN layers that were grown using the HVPE, MOCVD and ELOG methods and had different dislocation densities were studied via the electron-beam-induced current and cathodoluminescence methods. The effects of thermal annealing and electron beam irradiation on dislocation generation and multiplication were investigated. It is shown that the Peierls barrier for dislocation glide in GaN is essentially lower than 1 eV; thus, it is mobile even at room temperature. It is shown that the mobility of a dislocation in the state-of-the-art GaN is not entirely determined by its intrinsic properties. Rather, two mechanisms may work simultaneously: overcoming the Peierls barrier and overcoming localized obstacles. The role of threading dislocations as effective obstacles for basal plane dislocation glide is demonstrated. It is shown that under low-energy electron beam irradiation, the activation energy for the dislocation glide decreases to a few tens of meV. Therefore, under e-beam irradiation, the dislocation movement is mainly controlled by overcoming localized obstacles.

Insight-HXMT Detections of Hard X-Ray Tails in Scorpius X-1

Using the observations of the high-energy detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 from 2017 to 2020, we search for hard X-ray tails in the X-ray spectra in ∼30–200 keV. The hard X-ray tails are found throughout the Z-track on the hardness–intensity diagram, and the detected hard X-ray tails become hard and weak from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra of Insight-HXMT between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows a high-energy cutoff, implying a hot corona in it, but the high-energy cutoff is not seen in the hard X-ray spectrum of Sco X-1. From fitting the broadband spectrum of Sco X-1 in ∼2–200 keV, it is proposed that the hard X-ray tails in the HB and NB can be explained by the overall Comptonization COMPTB model, suggesting that the hard X-ray tails could have resulted from the Comptonization of the photons from the neutron star (NS) surface by the thermal electrons in the region between the NS and the disk and the energetic electrons in the freefall toward the NS in the converging flow onto the NS. However, this model cannot be responsible for the hard X-ray tails in the FB. Further study on the FB hard X-ray tails is needed.

RAIKOU (来光): A General Relativistic, Multiwavelength Radiative Transfer Code

We present a general relativistic radiative transfer code RAIKOU (来光) for multiwavlength studies of spectra and images including the black hole shadows around Kerr black holes. Important radiative processes in hot plasmas around black holes, i.e., (cyclo-)synchrotron, bremsstrahlung emission/absorption, and Compton/inverse-Compton scattering, are incorporated. The Maxwell–Jüttner and single/broken power-law electron distribution functions are implemented to calculate the radiative transfer via both thermal and nonthermal electrons. Two calculation algorithms are implemented for studies of the images and broadband spectra. An observer-to-emitter ray-tracing algorithm, which inversely solves the radiative transfer equation from the observer screen to emitting plasmas, is suitable for an efficient calculations of the images, e.g., the black hole shadows observed by the Event Horizon Telescope, and spectra without Compton effects. On the other hand, an emitter-to-observer Monte Carlo algorithm, by which photons are transported with a Monte Carlo method including the effects of Compton/inverse-Compton scatterings, enables us to compute multiwavelength spectra, with their energy bands broadly ranging from radio to very high energy gamma-ray. The X-ray black hole shadows, which are formed via synchrotron emission and inverse-Compton scattering processes and will be observed in the future X-ray interferometry missions, can be also computed with this algorithm. The code is generally applicable to accretion flows around Kerr black holes with relativistic jets and winds/coronae with various mass accretion rates (i.e., radiatively inefficient accretion flows, super-Eddington accretion flows, and others). We demonstrate an application of the code to a radiatively inefficient accretion flow onto a supermassive black hole.

Preparation and characterization of tea polyphenol composite microspheres encapsulated using sodium alginate and crosslinked starch

As promising regulators of human health, tea polyphenols (TP) possess the ability to alleviate intestinal dysbiosis and restore balance in the co-metabolic processes of host-intestinal flora. However, these polyphenols are sensitive to potential destruction throughout the digestive process, limiting their ultimate bioavailability. To facilitate controlled TP release within the gastrointestinal tract, TP-loaded composite microspheres were prepared using sodium alginate (SA) and crosslinked corn starch (CP). The prepared microspheres were characterized via Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter synchronous thermal analyzer (DSC-TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The properties of these microspheres were additionally examined through swelling assays, in vitro simulated release assays, and in vitro batch fermentation experiments. The outcome revealed that the prepared SA-crosslinked porous starch TP microspheres (CPMS) exhibited a significantly improved TP loading capacity (430.26 ± 16.71 mg/g). In vitro release assays demonstrated that the levels of TP release from CPMS in simulated colon fluid (325.05 ± 3.97 mg/mL) were significantly higher than that in simulated gastric fluid. In summary, the CPMS microspheres prepared herein can effectively achieve an improved TP loading, while exhibiting pH-responsive properties, and can effectively regulate the homeostatic balance of the intestinal microbiota.

Performance Study of Graphene Oxide as an Antierosion Coating for Ornamental and Heritage Dolostone

AbstractConcern for the perpetuation of stone monuments is deeply ingrained in humans; however, despite the attempts made in this field, there is still a great deal of effort needed to bring about advancements in the conservation of ornamental stone. Erosive agents, such as rain, extreme temperatures, and chemical and biological agents, threaten our stone heritage and gradually wear away buildings, sculptures, and other monuments found all around the world. Limestone and dolostone have been widely used throughout history, given their ease of extraction and workability. Nevertheless, these properties make them particularly vulnerable to the aforementioned erosive agents, for which the main solution at present is costly and time‐consuming restoration. Given the scarcity of effective and durable agents to prevent the deterioration of ornamental and heritage stones, and as graphene oxide (GO) has recently shown impressive effectiveness for this task, this work will further explore the viability of GO as a protective coating for monumental dolostone. For this purpose, GO is sprayed over dolostone surfaces by water dispersion with no adjuvants. The coating performance is assessed in terms of thermal stress, optical inspection (structured light 3D scanner), colorimetry, leachate analysis, and electron microscopy. The main results show that spray‐coated GO over stone surfaces creates a highly protective and durable barrier without altering their aesthetic qualities.

Preparation and characterization of Li2TiO3 ceramic pebbles by modification of the water‐based sol–gel method

AbstractLi2TiO3 is considered as one of the best candidates for breeding materials. This article adopted a modification water‐based sol–gel method to synthesize nano‐Li2TiO3 powders, which overcomes the poor phase purity, coarse grain, and inferior crushing strength described in the previous literature. In this paper, the thermal effect of the precursor, the crystal phase, and the morphology of the powders were characterized by thermogravimetric analysis/differential thermal analysis (TG/DTA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The nano‐structured Li2TiO3 powders with good dispersion and an average particle size of 20–50 nm were successfully synthesized at 600°C by controlling PH and hydrolysis rate. Moreover, the phase transition temperature for the monoclinic phase β‐Li2TiO3 was as low as 600°C, which is lower than 750°C using the traditional solid‐state method. Meanwhile, the morphology, porosity, crushing load, and thermal conductivity of ceramic pebbles are characterized systematically by using scanning electron microscope (SEM), mercury injection meter, compression strength equipment, and laser scattering method, respectively. Experimental results showed that the Li2TiO3 ceramic pebbles with a sphericity of .98, crush load of 48.4 N, and relative density of 90.03 % were successfully prepared at 1050°C for 2 h. This method will provide new guidance for the preparation of tritium breeders.

Fabrication of a colorimetric sensor using acetic acid-capped drug-mediated copper oxide nanoparticles for nitrite biosensing in processed food

Nitrite (NO2−) and nitrate (NO3−) are frequently used in cured meat products as preservatives, as they give a better taste and work well in color fixation. As a key possible carcinogen, excessive dietary consumption of NO2− in cured meat products would be bad for health. Herein, copper oxide nanoparticles (CuO NPs) were synthesized using the drug Augmentin as a reducing and capping agent. The desired synthesis of CuO NPs was confirmed by various characterization techniques, including UV–visible spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, thermal gravimetric analysis, X-ray diffraction, and scanning electron microscopy. The new approach of drug-mediated acetic acid-capped CuO NPs was developed for simple colorimetric detection of nitrite ions in a mimic solution of processed food. The color of the detection system changes from brown to yellow with the increase in the concentration of NO2− and has been observed with the naked eye. The selectivity of the NO2− detection system by the UV–visible spectrum and the naked eye is compared to other ions, such as Br−, I−, Cl−1, PO4−3, CO32−, and SO42−. The platform was successfully employed for the determination of nitrite in real samples. Moreover, this probe can be used for the sensitive detection of NO2− with a linear range of 1 × 10−8 to 2.40 × 10−6 M, a detection limit of 2.69 × 10−7 M, a limit of quantification 8.9 × 10−7 M, and a regression coefficient (R2) of 0.997. Our results suggest that this sensor can be used for on-site analysis and quantification as well as in the fields of disease diagnosis, environmental monitoring, and food safety.

Titanium nitrides as novel reactants for in-situ synthesis of TiB2-based composites with improved properties

A novel in-situ reactive approach based on the reactions among TiN, aluminum and boron has been developed to synthesize TiB 2 -based composites including TiB 2 - h BN (TB) and TiB 2 - h BN-AlN (TBA). Fully dense ceramics with fine-grained microstructure were successfully obtained via spark plasma sintering at 1850 °C/60 MPa/5 min. Microstructure analysis suggests h BN flakes were homogenously distributed in the TiB 2 matrix. For AlN, however, they were elongated into plate-like grains during sintering, in which lots of defects in terms of stacking faults and twinning structures were observed. The mechanical and thermophysical properties of as-sintered ceramics were comprehensively investigated and compared. Incorporating AlN significantly improved the flexure strength, hardness, fracture toughness and thermal conductivity of TiB 2 - h BN ceramics. The electrical conductivity of TB (3.06 × 10 6 S/m) is larger than that of TBA (2.35 × 10 6 S/m) at room temperature, but the value (6 × 10 5 S/m) was lower than that of TBA (6.9 × 10 5 S/m) at 1173 K. Based on the measurement of electrical and thermal conductivity, electron and phonon contributions to thermal conductivities of TB and TBA were calculated and their temperature dependences were illustrated.

Cell Responses to Calcium- and Protein-Conditioned Titanium: An In Vitro Study.

Dental implants have become the leading choice for patients who lose teeth; however, dental implantation is challenged by peri-implant infections. Here, calcium-doped titanium was fabricated by the combinational use of thermal evaporation and electron beam evaporation in a vacuum; then, the material was immersed in a calcium-free phosphate-buffered saline solution containing human plasma fibrinogen and incubated at 37 °C for 1 h, creating calcium- and protein-conditioned titanium. The titanium contained 12.8 ± 1.8 at.% of calcium, which made the material more hydrophilic. Calcium release by the material during protein conditioning was able to change the conformation of the adsorbed fibrinogen, which acted against the colonization of peri-implantitis-associated pathogens (Streptococcus mutans, UA 159, and Porphyromonas gingivalis, ATCC 33277), while supporting the adhesion and growth of human gingival fibroblasts (hGFs). The present study confirms that the combination of calcium-doping and fibrinogen-conditioning is a promising pathway to meeting the clinical demand for suppressing peri-implantitis.

E–H transitions in Ar/O2 and Ar/Cl2 inductively coupled plasmas: Antenna geometry and operating conditions

Electronegative inductively coupled plasmas (ICPs) are used for conductor etching in the microelectronics industry for semiconductor fabrication. Pulsing of the antenna power and bias voltages provides additional control for optimizing plasma–surface interactions. However, pulsed ICPs are susceptible to capacitive-to-inductive mode transitions at the onset of the power pulse due to there being low electron densities at the end of the prior afterglow. The capacitive (E) to inductive (H) mode transition is sensitive to the spatial configuration of the plasma at the end of the prior afterglow, circuit (matchbox) settings, operating conditions, and reactor configurations, including antenna geometry. In this paper, we discuss results from a computational investigation of E–H transitions in pulsed ICPs sustained in Ar/Cl2 and Ar/O2 gas mixtures while varying operating conditions, including gas mixture, pulse repetition frequency, duty cycle of the power pulse, and antenna geometry. Pulsed ICPs sustained in Ar/Cl2 mixtures are prone to significant E–H transitions due to thermal dissociative attachment reactions with Cl2 during the afterglow which reduce pre-pulse electron densities. These abrupt E–H transitions launch electrostatic waves from the formation of a sheath at the boundaries of the plasma and under the antenna in particular. The smoother E–H transitions observed for Ar/O2 mixture results from the higher electron density at the start of the power pulse due to the lack of thermal electron attaching reactions to O2. Ion energy and angular distributions (IEADs) incident onto the wafer and the dielectric window under the antenna are discussed. The shape of the antenna influences the severity of the E–H transition and the IEADs, with antennas having larger surface areas facing the plasma producing larger capacitive coupling. Validation of the model is performed by comparison of computed electron densities with experimental measurements.

Strong Nonideal Electric Fields and Energy Dissipation Observed by MMS within Field-Aligned Current Layers in the Plasma Sheet of the Earth’s Magnetotail

We report the MMS observations of the intense spikes of field-aligned current (FAC) produced by magnetic reconnection at the plasma sheet (PS) field lines. The MMS was located tailward of a near-Earth X-line and the most intense spike of FAC with an electric current density of ∼70 nA/m2 was observed near the magnetic separatrix. The FAC structures located deeper in the PS were strongly filamented and consisted of several spikes with a thickness of ∼(1–2)ρe (ρe is the gyroradius of thermal electrons). We found that the FAC in these structures was carried by unmagnetized thermal and suprathermal electron populations (≥ 1 keV), which were ∼(20–80)% of the entire electron population. Strong nonideal electric fields up to ∼100 mV/m were detected in the FAC spike near the magnetic separatrix. The generation of these fields was mainly due to the anomalous resistivity, possibly caused by the electrostatic fluctuations. As a result, a significant energy dissipation of up to 1.3 nW/m3 occurred within the electron-scale FAC structure, which caused an increase in the electron temperature by a factor of two compared with that outside the FAC. Thus, MMS observations demonstrate that during the interval of the active X-line, the outer part of the PS consists of multiple electron-scale FAC layers/filaments in which a significant energy exchange between electrons and fields occurs. To investigate the stability of these filaments and estimate their lifetime, additional observations and theoretical studies are needed.

Relativistic analysis of upper hybrid wave propagation and trapping

We investigate the impact of relativistic effects on upper hybrid (UH) waves in plasmas with thermal electrons, particularly focusing on modifications of the conditions under which UH wave trapping and related low-threshold parametric decay instabilities (PDIs) may occur. A moderately relativistic (MR) dispersion relation for UH waves, valid for electron temperatures up to 25 keV and wave frequencies up to twice the electron cyclotron frequency, is obtained from previous results and shown to reduce to the warm non-relativistic result commonly used for PDI studies at low electron temperatures. The conditions under which MR UH waves propagate are then determined and compared with warm and cold plasma theory, showing a general increase in the electron density and background magnetic field strength at which the UH resonance occurs for finite electron temperatures. We next investigate the impact of the MR corrections on the possibility of UH wave trapping for X-mode electron cyclotron resonance heated (ECRH) plasmas at the ASDEX Upgrade tokamak and scaled versions of the ASDEX Upgrade parameters with core electron temperatures resembling those expected in ITER X-mode ECRH plasmas. The MR UH wave trapping conditions are virtually unchanged for ASDEX Upgrade relative to warm theory, due to the low electron temperatures, while potentially important differences between warm and MR theory exist for ITER-like core electron temperatures; cold theory is found to be insufficient in both cases. Finally, the MR dispersion relation is shown to qualitatively reproduce the PDI thresholds from warm theory for previously studied ASDEX Upgrade cases.

Phase relations in heat treated sodium borosilicate glasses

Sodium borosilicate glasses are processed to porous glasses as well as to Vycor™ type glasses via phase separation and selective leaching. Both materials consist mainly of SiO2. Thermal treatment inducing phase separation is crucial for microstructure development. Sodium borosilicate glasses with molar compositions of 8Na2O.21B2O3.71SiO2 and 8Na2O.28B2O3.64 SiO2 were melted, rapidly cooled and investigated by thermal analysis and scanning electron microscopy. The glasses were thermally treated for 120 h at 630 to 730°C, and then leached, first for 72 h in 0·1 M HCl at 60°C, and subsequently for 4 h in 0·5 M NaOH at 30°C. X-ray fluorescence was applied to characterise the chemical compositions. Microstructure development was first analysed by differential thermal analysis and dilatometry, and the pore structure was characterised by Hg porosimetry and N2 adsorption. Heat treated glasses were then analysed by low voltage scanning electron microscopy, combined in one case with chemical analysis by energy dispersive x-ray analysis. The results are discussed with respect to phase relations. After long term heat treatment, at least three phases exist in two independent metastable two-phase equilibria on different size and time scales.

Preparation and electrochemical stability of Co-doped La1.5Sr0.5Ni1−xCoxO4+δ cathode materials

A series of Co-doped La1.5Sr0.5Ni1−xCoxO4+δ cathode materials (x =0, 0.2, 0.4 and 0.6) were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), coefficient of thermal expansion (CTE) measurement and scanning electron microscope (SEM). The results suggest that all La1.5Sr0.5Ni1−xCoxO4+δ samples have a single pure phase with the perovskite-like structure and the doping with the Co element can increase the CTE value. Using La1.5Sr0.5Ni1−xCoxO4+δ as the cathode materials in the solid oxide fuel cell (SOFC), their electrical conductivity and electrochemical impedance spectroscopy were measured. The results indicate that the conductivity increases with the increase of Co doping amount and the La1.5Sr0.5Ni0.6Co0.4O4+δ sample with x = 0.4 displays the highest conductivity of 51.21 S/cm at 800 °C; however, a higher content of Co (x > 0.4) leads to a decrease of the conductivity. In addition, La1.5Sr0.5N0.6Co0.4O4+δ exhibits the lowest polarization resistance of 4.180 Ω·cm2 in electrochemical impedance spectrum at 700 °C, displaying its excellent electrochemical properties as the cathode materials.

A novel high-current, high-resolution, low-kinetic-energy electron source for inverse photoemission spectroscopy

A high-current electron source for inverse photoemission spectroscopy is described. The source comprises a thermal cathode electron emission system, an electrostatic deflector-monochromator, and a lens system for variable kinetic energy (1.6–20 eV) at the target. When scaled to the energy resolution, the electron current is an order of magnitude higher than that of previously described electron sources developed in the context of electron energy loss spectroscopy. Surprisingly, the experimentally measured energy resolution turned out to be significantly better than calculated by standard programs, which include the electron–electron repulsion in the continuum approximation. The achieved currents are also significantly higher than predicted. We attribute this “inverse Boersch-effect” to a mechanism of velocity selection in the forward direction by binary electron–electron collisions.

Two-step Acceleration of Energetic Electrons at Magnetic Flux Ropes during Turbulent Reconnection

Energetic electrons have been frequently observed during magnetic reconnection in the magnetotail. The acceleration process of the energetic electrons is not fully understood. In this paper, we select for a detailed study a case of energetic electron acceleration from the earlier reported interval of turbulent magnetic reconnection in Earth’s magnetotail observed by the Magnetospheric Multiscale mission. We use the first-order Taylor expansion method to reconstruct the magnetic topology of electron acceleration sites from the data. We find that the energetic electron fluxes increase inside the flux rope forming in front of the magnetic pileup region. We show that the energetic electrons are produced by a two-step process where two different acceleration mechanisms are successively operating outside and inside the flux rope. First, the thermal electrons are energized in the field-aligned direction inside the magnetic pileup region owing to the Fermi mechanism forming a cigar-like distribution. Second, those energized electrons are further accelerated predominately antiparallel to the magnetic field direction by a parallel electric field inside the flux rope. Our findings provide information for a better understanding of the generation of energetic electrons during turbulent reconnection process.