Distribution Of High-energy Electrons Research Articles

Synthetic consortium of Ganoderma lucidum and Lactobacillus plantarum for enhanced natural products biosynthesis

Microbial coculture holds immense promise for biomanufacturing. Herein, we designed a synthetic consortium of G. lucidum and L. plantarum for enhanced natural product biosynthesis. The spatio-temporal alignment of the strains revealed an implicit disposition for transient and long-term mutualistic co-existence in the shared environment. The consortium assembly and biomass growth were driven by an intuitive toggle-switching of carbon/nitrogen sources and TOR signaling. Extracellular electron transfer propelled by redox shuttles facilitated the distribution of high-energy electrons and enhanced the consortium's robustness. The ROS-scavenging activity of antioxidant enzymes maintained the cells' viability via intracellular ROS removal. The CAT, GPX, and APX enzymes catalyzed the reduction of H2O2 to H2O and O2, thereby protecting the cells against the toxic effects of ROS. Small-signaling molecules stimulated the biosynthesis of bioactive natural products in the coculture. Over-expression of target genes further enhanced ganoderic acids and exopolysaccharides bioproduction in the coculture system. The study provides insight into the physicochemical and molecular forces that drive cooperative interaction and stimulate natural product biosynthesis in G. lucidum and L. planatarum consortium.

Development of Soft X-ray Stereo Imaging System for Time-evolution Measurement of High-energy Electron Distribution

Development of Soft X-ray Stereo Imaging System for Time-evolution Measurement of High-energy Electron Distribution

Double-filter high-resolution soft x-ray tomographic diagnostic for investigating electron acceleration in TS-6 reconnection merging experiments.

An innovative tangential-view soft x-ray (SXR) tomographic imaging measurement was developed on the TS-6 spherical tokamak merging device as a key diagnostic for investigating the mechanism of electron acceleration. In order to measure SXR with different energy ranges, two micro-channel plates (MCPs) are, respectively, installed in two vacuum chambers, which are equipped with different filters. Especially designed lenses and fiber bundles serve as an optical system to transfer images from phosphor plates of MCPs to a high speed imaging system. This design also enables us to simultaneously measure two images appearing on phosphor plates of MCPs by just one high speed imaging system. The temporal and spatial resolution of this diagnostic can be up to 5 µs and 4mm, respectively, at present. The tomographic method based on the Phillips-Tikhonov regularization is employed to reconstruct line-integrated images into the local emissivity of SXR, which reflects the spatial distribution of high-energy electrons. Owing to this diagnostic, we successfully measured SXR emitted from the downstream region of magnetic reconnection in TS-6 merging experiments for the first time. The energy range of SXR turned out to be higher than 100eV but lower than 400eV.

Suzaku observations of Jovian diffuse hard X-ray emission

Abstract We report on results of systematic analyses of the entire three X-ray data sets of Jupiter taken by Suzaku in 2006, 2012, and 2014. Jovian diffuse hard X-ray emission was discovered by Suzaku in 2006 when the solar activity went toward its minimum. The diffuse emission was spatially consistent with the Jovian inner magnetosphere and was spectrally fitted with a flat power-law function suggesting non-thermal emission. Thus, a scenario in which ultra-relativistic (tens of MeV) electrons in the Jovian inner magnetosphere inverse-Comptonize solar visible photons into X-ray bands has been hypothetically proposed. We focused on the dependence of the Jovian diffuse hard X-ray emission on the solar activity to verify this scenario. The solar activity in 2012 and 2014 was around the maximum of the 24th solar cycle. By combining the imaging and spectral analyses for the three data sets, we successfully separated the contribution of the diffuse emission from the emission of Jupiter’s body (i.e., the aurora and disk emission). The 1–5 keV luminosity of the diffuse emission has been stable and did not vary significantly, and did not simply depend on the solar activity, which is also known to affect the high-energy electron distribution in the Jovian inner magnetosphere scarcely. The luminosity of the body emission both in 0.2–1 and 1–5 keV, in contrast, probably depended on the solar activity and varied by a factor of 2–5. These results strongly supported the inverse-Compton scattering scenario by the ultra-relativistic electrons. In this paper, we estimate spatial and spectral distributions of the inverse-Compton scattering X-rays by Jovian magnetospheric high-energy electrons with reference to the Divine–Garrett model and found a possible agreement in an inner region (≲10 RJ) for the X-ray observations.

Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

ABSTRACT We report the analysis of simultaneous multiwavelength data of the high-energy-peaked blazar RGB J0710 + 591 from the Large Area X-ray Proportional Counters, Soft X-ray focusing Telescope, and Ultraviolet Imaging Telescope (UVIT) instruments onboard AstroSat. The wide band X-ray spectrum (0.35–30 keV) is modelled as synchrotron emission from a non-thermal distribution of high-energy electrons. The spectrum is unusually curved, with a curvature parameter βp ∼ 6.4 for a log parabola particle distribution, or a high-energy spectral index p2 > 4.5 for a broken power-law distribution. The spectrum shows more curvature than an earlier quasi-simultaneous analysis of Swift–XRT/NuSTAR data where the parameters were βp ∼ 2.2 or p2 ∼ 4. It has long been known that a power-law electron distribution can be produced from a region where particles are accelerated under Fermi process and the radiative losses in acceleration site decide the maximum attainable Lorentz factor, γmax. Consequently, this quantity decides the energy at which the spectrum curves steeply. We show that such a distribution provides a more natural explanation for the AstroSat data as well as the earlier XRT/NuSTAR observation, making this as the first well-constrained determination of the photon energy corresponding to γmax. This in turn provides an estimate of the acceleration time-scale as a function of magnetic field and Doppler factor. The UVIT observations are consistent with earlier optical/UV measurements and reconfirm that they plausibly correspond to a different radiative component than the one responsible for the X-ray emission.

Suzaku observation of Jupiter’s X-rays around solar maximum

Abstract We report on results of imaging and spectral studies of X-ray emission from Jupiter observed by Suzaku. In 2006, Suzaku found diffuse X-ray emission in 1–5 keV associated with Jovian inner radiation belts. It has been suggested that the emission is caused by the inverse-Compton scattering by ultra-relativistic electrons (∼50 MeV) in Jupiter’s magnetosphere. To confirm the existence of this emission and to understand its relation to the solar activity, we conducted an additional Suzaku observation in 2014 around the maximum of the 24th solar cycle. As a result, we successfully found the diffuse emission around Jupiter in 1–5 keV again, and also found point-like emission in 0.4–1 keV. The luminosity of the point-like emission, which was probably composed of solar X-ray scattering, charge exchange, or auroral bremsstrahlung emission, increased by a factor of ∼5 with respect to the findings from 2006, most likely due to an increase of the solar activity. The diffuse emission spectrum in the 1–5 keV band was well-fitted with a flat power-law function (Γ = 1.4 ± 0.1) as in the past observation, which supported the inverse-Compton scattering hypothesis. However, its spatial distribution changed from ∼12 × 4 Jovian radius (Rj) to ∼20 × 7 Rj. The luminosity of the diffuse emission increased by the smaller factor of ∼3. This indicates that the diffuse emission is not simply responding to the solar activity, which is also known to cause little effect on the distribution of high-energy electrons around Jupiter. Further sensitive study of the spatial and spectral distributions of the diffuse hard X-ray emission is important to understand how high-energy particles are accelerated in Jupiter’s magnetosphere.

Electron Acceleration in Middle-age Shell-type γ-Ray Supernova Remnants

Abstract Over the past decade, γ-ray observations of supernova remnants (SNRs) and accurate cosmic-ray (CR) spectral measurements have significantly advanced our understanding of particle acceleration in SNRs. In combination with multiwavelength observations of a large sample of SNRs, it has been proposed that the highest energy particles are mostly accelerated in young remnants, and the maximum energy that middle-age and old SNRs can accelerate particles to decreases rapidly with the decrease in shock speed. If SNRs dominate the CR flux observed at Earth, a large number of particles need to be accelerated in old SNRs for the soft CR spectrum even though they cannot produce very high-energy CRs. With radio, X-ray, and γ-ray observations of seven middle-age shell-type SNRs, we derive the distribution of high-energy electrons trapped in these remnants via a simple one-zone leptonic emission model and find that their spectral evolution is consistent with such a scenario. In particular, we find that particle acceleration by shocks in middle-age SNRs with age t can be described by a unified model with the maximum energy decreasing as t −3.1 and the number of GeV electrons increasing as t 2.5 in the absence of escape from SNRs.

Accelerated electrons for in situ peak intensity monitoring of tightly focused femtosecond laser radiation at high intensities

A simple technique for diagnosing the peak intensity of a tightly focused high-power femtosecond laser beam is proposed. The method is based on tracking the angular distribution of electrons directly accelerated in the waist of linearly polarized tightly focused radiation. Field ionization of a low density (<1016 cm−3) gas (e.g. helium) creates electrons, which are accelerated by the electromagnetic field and leave the focal area with relativistic residual energy. Three dimensional simulations utilizing the particle-in-cell code and test particle method revealed that the maximum of angular distribution of high energy electrons shifts to the beam axis with increase in the peak laser intensity. Hence, the peak laser intensity may be well evaluated by detecting a direction of the flux of large momentum particles. The experimentally measured angular characteristics of electrons accelerated in the caustic region of tightly focused ∼1 TW laser radiation with an estimated vacuum peak intensity above 1019 W cm−2 have shown reasonable agreement with the numerical simulations. Shot-to-shot variation of the pulse energy leads to deviations in the particles angular distribution, opening the opportunity to control the focusing quality in situ, in each laser shot.

Generation of runaway electrons during the initial stage of the T-10 tokamak plasma discharge

The formation of runaway electron beams in the initial stage of discharge is one of the characteristic features of fusion facilities with magnetic plasma confinement, such as tokamaks. They are generated due to the presence of the high electric fields and strong plasma-wall interaction in plasma. The runaway electrons produced during the breakdown stage also remain in the plasma in the quasistationary stage of the discharge. Studies carried out at the T-10 tokamak show that the electron energy and the heat flux density can reach 5–10 MeV and 1–3 GW/m2, respectively. Thus, the interaction with electrons causes erosion and damage to the limiter surface. In this article, the energy distribution of high-energy electrons formed in the initial stage of plasma discharge in the T-10 tokamak during the formation of runaway electron beams in a strong longitudinal magnetic field was studied. The effect of the plasma density and MHD perturbations on the generation and acceleration of runaway electrons was revealed. The energy distributions of runaway electrons were estimated for different stages of the plasma discharge development.

Microwave and Hard X-Ray Observations of the 2017 September 10 Solar Limb Flare

Abstract We report the first science results from the newly completed Expanded Owens Valley Solar Array (EOVSA), which obtained excellent microwave (MW) imaging spectroscopy observations of SOL2017-09-10, a classic partially occulted solar limb flare associated with an erupting flux rope. This event is also well-covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in hard X-rays (HXRs). We present an overview of this event focusing on MW and HXR data, both associated with high-energy nonthermal electrons, and we discuss them within the context of the flare geometry and evolution revealed by extreme ultraviolet observations from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory. The EOVSA and RHESSI data reveal the evolving spatial and energy distribution of high-energy electrons throughout the entire flaring region. The results suggest that the MW and HXR sources largely arise from a common nonthermal electron population, although the MW imaging spectroscopy provides information over a much larger volume of the corona.

Impulsive radio and hard X-ray emission from an M-class flare

Context. Impulsive radio and hard X-ray emission from large solar flares are usually attributed to a hard distribution of high-energy electrons accelerated in the energy dissipation process of magnetic reconnection. Aims. We report the detection of impulsive radio and hard X-ray emissions produced by a population of energetic electrons with a very soft distribution in an M-class flare: SOL2015-08-27T05:45 . Methods. The absence of impulsive emission at 34 GHz and hard X-ray emission above 50 keV and the presence of distinct impulsive emission at 17 GHz and lower frequencies and in the 25–50 keV X-ray band imply a very soft distribution of energetic electrons producing the impulsive radio emission via the gyro-synchrotron process, and impulsive X-rays via bremsstrahlung. Results. The spectrum of the impulsive hard X-ray emission can be fitted equally well with a power-law model with an index of ∼6.5 or a super-hot thermal model with a temperature as high as 100 MK. Imaging observations in the extreme-UV and X-ray bands and extrapolation of the magnetic field structure using a nonlinear force-free model show that energetic electrons trapped in coronal loops are responsible for these impulsive emissions. Conclusions. Since the index of the power-law model is nearly constant during the impulsive phase, the power-law distribution or the super-hot component should be produced by a bulk energization process such as the Fermi and betatron acceleration of collapsing magnetic loops.

Direct conversion of β-decay energy into electrical energy

A comparison of the efficiencies of the power supplies produced based on the β-radiation sources has been carried out. The factors decreasing the efficiency of the device have been revealed. The results of the experimental studies and calculations of the efficiency of the direct energy conversion of Ni-63 β-radiation into electrical energy using silicon p–i–n diodes are presented. An expression for the open-circuit voltage of the convertor taking into account the distribution of high-energy electrons in the space charge region (SCR) of the p–i–n diode has been obtained. The ways of optimizing the convertor’s parameters due to improvements in the diode production technology and optimization of the thicknesses of the active emitter layer and i-region of the semiconductor convertor have been indicated.

Optimization of the parameters of power sources excited by β-radiation

The experimental results and calculations of the efficiency of the energy conversion of Ni-63 β-radiation sources to electricity using silicon p–i–n diodes are presented. All calculations are performed taking into account the energy distribution of β-electrons. An expression for the converter open-circuit voltage is derived taking into account the distribution of high-energy electrons in the space-charge region of the p–i–n diode. Ways of optimizing the converter parameters by improving the technology of diodes and optimizing the emitter active layer and i-region thicknesses of the semiconductor converter are shown. The distribution of the conversion losses to the source and radiation detector and the losses to high-energy electron entry into the semiconductor is calculated. Experimental values of the conversion efficiency of 0.4–0.7% are in good agreement with the calculated parameters.

Energy distribution of fast electrons accelerated by high intensity laser pulse depending on laser pulse duration

The dependence of high-energy electron generation on the pulse duration of a high intensity LFEX laser was experimentally investigated. The LFEX laser (λ = 1.054 and intensity = 2.5 – 3 x 1018 W/cm2) pulses were focused on a 1 mm3 gold cubic block after reducing the intensities of the foot pulse and pedestal by using a plasma mirror. The full width at half maximum (FWHM) duration of the intense laser pulse could be set to either 1.2 ps or 4 ps by temporally stacking four beams of the LFEX laser, for which the slope temperature of the high-energy electron distribution was 0.7 MeV and 1.4 MeV, respectively. The slope temperature increment cannot be explained without considering pulse duration effects on fast electron generation.

Nonproportionality of Scintillator Detectors. V. Comparing the Gamma and Electron Response

This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators SrI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (Eu), GYGAG(Ce) and CsI(Na).

Two-dimensional quasi-double-layers in two-electron-temperature, current-free plasmas

The expansion of a plasma with two disparate electron populations into vacuum and channeled by a divergent magnetic nozzle is analyzed with an axisymmetric model. The purpose is to study the formation and two-dimensional shape of a current-free double-layer in the case when the electric potential steepening can still be treated within the quasineutral approximation. The properties of this quasi-double-layer are investigated in terms of the relative fraction of the high-energy electron population, its radial distribution when injected into the nozzle, and the geometry and intensity of the applied magnetic field. The two-dimensional double layer presents a curved shape, which is dependent on the natural curvature of the equipotential lines in a magnetically expanded plasma and the particular radial distribution of high-energy electrons at injection. The double layer curvature increases the higher the nozzle divergence is, the lower the magnetic strength is, and the more peripherally hot electrons are injected. A central application of the study is the operation of a helicon plasma thruster in space. To this respect, it is shown that the curvature of the double layer does not increment the thrust, it does not modify appreciably the downstream divergence of the plasma beam, but it increases the magnetic-to-pressure thrust ratio. The present study does not attempt to cover current-free double layers involving plasmas with multiple populations of positive ions.

On the reconstruction of the energy distribution of electrons accelerated in solar flares

A technique for reconstructing energy spectra of electrons accelerated in solar flares is suggested that is based on the rigorous solution of the inverse problem considering their X-ray bremsstrahlung. Model calculations are made for various spectra, and it is proved that this technique makes it possible to find the electron energy distribution in real flare events. The energy distribution of high-energy electrons accelerated in the solar flare observed on July 26, 2002, is reconstructed. It is shown that the hard X-ray spectrum of the flare may result from the bremsstrahlung of three groups of high-energy electrons.

Study on density distribution of high-energy electrons in pulsed corona discharge

In this study, the radial profile of the overall emission intensity of the second positive system (C 3 Π u→B 3 Π g) emitted from the positive pulse corona discharge of N 2 and air in a line-cylinder reactor was successfully recorded against a severe electromagnetic pulse interference coming from the corona discharge at room temperature and 1 atm. The relation between the density distributions of the high-energy electron (whose energy is higher than 11.03 eV and enough to excite N 2 to its C 3 Π u state from the ground state) and the emission profiles is studied with the aid of a reaction radiation rate analysis method. By the relation, it is found that the radial distribution of the high-energy electron decreases nonlinearly with the radial distance from the reactor axis and increases directly with the discharge voltage for any sampling apertures. These experimental results would be helpful to establish the molecule reaction dynamics model of pulsed corona discharge deSO 2/deNO x and optimize the power supply and reactor.

Density distribution of high energy electrons in pulsed corona discharge of NO+N 2 mixture

Emission spectroscopy of the high-voltage pulsed positive corona discharge in a line-cylinder reactor is used to investigate the high-energy electron density distribution in the discharge gap. The relative overall emission intensity spatial distribution profile of the A 2Σ +→X 2Π transition of NO is successfully recorded against a severe electromagnetic pulse interference coming from the corona discharge at one atmosphere. The spectroscopic investigation shows that the high-energy electron density in the discharge has a nonlinearly decline in the radial distribution. When varying the discharge voltage, the absolute emission intensity of NO is different but the radial distribution profile is similar. If an oxygen flow was introduced into the discharge reactor, the emission intensity of NO decreases tremendously and, therefore, the high-energy electron density decreases reasonably.

Cosmic‐Ray Electrons in Groups and Clusters of Galaxies: Primary and Secondary Populations from a Numerical Cosmological Simulation

We investigate the generation and distribution of high-energy electrons in the cosmic structure environment and their observational consequences by carrying out the first cosmological simulation that includes directly cosmic-ray (CR) particles. Starting from cosmological initial conditions, in addition to the gas and dark matter related quantities, we follow the evolution of CR electrons (primary and secondary) and CR ions along with a passive magnetic field. CR ions and primary electrons are injected in accordance with the thermal leakage model and accelerated in the test-particle limit of diffusive shock acceleration at shocks associated with large-scale structure formation. Secondary electrons are continuously generated through p-p inelastic collisions of the CR ions with the thermal nuclei of the intergalactic medium. The evolution of the CR electrons accounts for spatial transport, adiabatic expansion/compression, and losses due to Coulomb collisions, bremsstrahlung, synchrotron and inverse-Compton emission. The magnetic field is seeded at shocks according to the Biermann battery model, and thereafter amplified by shear flow and gas compression. We compute the emission due to the inverse-Compton scattering of the simulated primary and secondary electrons off cosmic microwave background photons and compare it with the published values of the detected radiation excesses in the hard X-ray and extreme-ultraviolet wavebands. We find that the few instances of detection of hard X-ray radiation excess could be explained in the framework of IC emission from primary electrons in clusters characterized by high accretion/merger activity. On the other hand, with the only exception of measured flux from the Coma Cluster by Bowyer, Berghoefer & Korpela, both primary and secondary CR electrons associated with the cosmic structure formation account at most for a small fraction of the radiation excess detected in the extreme-ultraviolet waveband. Next, we calculate the synchrotron emission after normalizing the magnetic field strength so that for a Coma-like cluster the volume-averaged B21/2 3 ?G. Our results indicate that the synchrotron emission from the secondary CR electrons reproduces several general properties observed in radio halos. These include the recently found P1.4 GHz versus TX relationship, the morphology and polarization of the emitting region, and, to some extent, even the spectral index. In addition, radio synchrotron emission from primary electrons turns out to be large enough to power extended regions of radio emission, resembling radio relics observed at the outskirts of clusters. Once again we find a striking resemblance between the general properties of morphology, polarization, and spectral index of our synthetic maps and those of reported in the literature.