Electron Energy Spectrum Research Articles

The impact of an extreme solar event on the middle atmosphere: a case study

Abstract. A possible impact of an extreme solar particle event (ESPE) on the middle atmosphere is studied for present-day climate and geomagnetic conditions. We consider an ESPE with an occurrence probability of about 1 per millennium. In addition, we assume that the ESPE is followed by an extreme geomagnetic storm (GMS), and we compare the contribution of the two extreme events. The strongest known and best-documented ESPE of 774/5 CE is taken as a reference example and established estimates of the corresponding ionization rates are applied. The ionization rates due to the energetic particle precipitation (EPP) during an extreme GMS are upscaled from analyzed distributions of electron energy spectra of observed GMSs. The consecutive buildup of NOx and HOx by ionization is modeled in the high-top 3D chemistry circulation model KArlsruhe SImulation Model of the middle Atmosphere (KASIMA), using specified dynamics from ERA-Interim analyses up to the stratopause. A specific dynamical situation was chosen that includes an elevated stratosphere event during January and maximizes the vertical coupling between the northern polar mesosphere–lower thermosphere region and the stratosphere; it therefore allows us to estimate a maximum possible impact. The particle event initially produces about 65 Gmol of NOy, with 25 Gmol of excess NOy even after 1 year. The related ozone loss reaches up to 50 % in the upper stratosphere during the first weeks after the event and slowly descends to the mid-stratosphere. After about 1 year, 20 % ozone loss is still observed in the northern stratosphere. The GMS causes strong ozone reduction in the mesosphere but plays only a minor role in the reduction in total ozone. In the Southern Hemisphere (SH), the long-lived NOy in the polar stratosphere, which is produced almost solely by the ESPE, is transported into the Antarctic polar vortex, where it experiences strong denitrification into the troposphere. For this special case, we estimate a NO3 washout that could produce a measurable signal in ice cores. The reduction in total ozone causes an increase of the UV erythema dose of less than 5 %, which maximizes in spring for northern latitudes of 30∘ and in summer for northern latitudes of about 60∘.

Dissection of DNA damage and repair pathways in live cells by femtosecond laser microirradiation and free-electron modeling

Understanding and predicting the outcome of the interaction of light with DNA has a significant impact on the study of DNA repair and radiotherapy. We report on a combination of femtosecond pulsed laser microirradiation at different wavelengths, quantitative imaging, and numerical modeling that yields a comprehensive picture of photon-mediated and free-electron-mediated DNA damage pathways in live cells. Laser irradiation was performed under highly standardized conditions at four wavelengths between 515 nm and 1,030 nm, enabling to study two-photon photochemical and free-electron-mediated DNA damage in situ. We quantitatively assessed cyclobutane pyrimidine dimer (CPD) and γH2AX-specific immunofluorescence signals to calibrate the damage threshold dose at these wavelengths and performed a comparative analysis of the recruitment of DNA repair factors xeroderma pigmentosum complementation group C (XPC) and Nijmegen breakage syndrome 1 (Nbs1). Our results show that two-photon-induced photochemical CPD generation dominates at 515 nm, while electron-mediated damage dominates at wavelengths ≥620 nm. The recruitment analysis revealed a cross talk between nucleotide excision and homologous recombination DNA repair pathways at 515 nm. Numerical simulations predicted electron densities and electron energy spectra, which govern the yield functions of a variety of direct electron-mediated DNA damage pathways and of indirect damage by •OH radicals resulting from laser and electron interactions with water. Combining these data with information on free electron-DNA interactions gained in artificial systems, we provide a conceptual framework for the interpretation of the wavelength dependence of laser-induced DNA damage that may guide the selection of irradiation parameters in studies and applications that require the selective induction of DNA lesions.

Isolated CuO and medium strong acid on CuO/Nb2O5-H catalyst for efficient enhancement of triethylamine selective catalytic oxidation

The selective catalytic oxidation (SCO) of triethylamine (TEA) to harmless N2, CO2, and H2O is an appropriate elimination technology. It is necessary to develop the catalysts capable of working under mild condition and with excellent N2 selectivity for this reaction. In this article, the CuO/Nb2O5-H catalysts with various loadings were characterized and employed for the SCO of TEA. The 15 %CuO/Nb2O5-H demonstrated the most noticeable catalytic performance. At 220 °C, the conversion of TEA reached 100.0 %, and the selectivity of N2 was 96.0 %. XPS, UV–vis results demonstrated the presence of isolated CuO species in the catalyst and auger electron energy spectra proved the content of Cu2+ species over 85 %. Pyridine-IR and NH3-TPD demonstrated the presence of a substantial number of acidic sites in Nb2O5-H. Based on the in-situ DRIFTs results, the adsorption of TEA on the acidic sites of Nb2O5-H at low temperature is considered as the initial step in the process, followed by C-N bond activation, cleavage, and adsorption of the -NH* intermediates. The -NH* was oxidized to N2 by highly dispersed copper oxide species on the catalyst surface at 220 °C.

The Study on Heat Treatment Microstructure and Properties of Extruded Al-Mg-Si-Mn-Cr-Zr Alloy

In order to obtain a high-strength Al-Mg-Si aluminum alloy with a tensile strength of more than 400MPa, a trace amount of Zr is added to the 6082 aluminum alloy to obtain an Al-1.0Mg-1.05Si-0.55Mn-0.15Cr-0.045Zr alloy. The mechanical properties and microstructure of the extruded Al-1.0Mg-1.05Si-0.55Mn-0.15Cr-0.045Zr alloy were studied by tensile performance test, metallography, scanning electron microscope (SEM), transmission electron microscope (TEM), electron backscatter diffraction (EBSD) observation and energy spectrum analysis. The results show that, after 545°C×2h+170°C×8h heat treatment, the alloy has the best mechanical properties. The tensile strength, yield strength and elongation at break reached 423MPa, 402MPa and 14%, respectively. The alloy strengthening mechanism is mainly due to the large number of dispersed needle-like β′ phases, sub-micron α-Al(MnCrFe)Si phases, α-Al(MnFe)Si phases and micron-level α-Al(MnCrFe)Si phases precipitated inside the grains and grain boundaries. The alloy precipitates sub-micron α-Al(MnCrFe)Si phase, α-Al(MnFe)Si phase and micron-level α-Al(MnCrFe)Si phase. After the alloy is treated at 545°C×2h+170°C×8h, a large number of dispersed needle-like β″ precipitations are uniformly precipitated in the inside the grains respectively. These precipitations can improve the strength of the material. The average grain size of the alloy is 7.41μm, and a bimodal grain structure composed of low-angle grain boundaries and high-angle grain boundaries is formed.

Electron energy spectrum of the non-concentric spherical core-shell quantum dot

It was suggested the model of the spherical core-shell quantum dot with shifted core from common center. In the paper the effective mass approximation has been used and the Schrödinger equation has been solved by using the plane wave method. The electron energy spectra have been defined as a function of the both core radius and shell radius in the case of shifted core from the spherical center. Also, the dependence of the electron energy spectrum on the core/shell position has been calculated. The splitting of electron energy levels has been analyzed in the cases of different core position. That is why electron energy transitions will be different in comparison to the case of a no-shifted core.

Identification and reconstruction of low-energy electrons in the ProtoDUNE-SP detector

Measurements of electrons from νe interactions are crucial for the Deep Underground Neutrino Experiment (DUNE) neutrino oscillation program, as well as searches for physics beyond the standard model, supernova neutrino detection, and solar neutrino measurements. This article describes the selection and reconstruction of low-energy (Michel) electrons in the ProtoDUNE-SP detector. ProtoDUNE-SP is one of the prototypes for the DUNE far detector, built and operated at CERN as a charged particle test beam experiment. A sample of low-energy electrons produced by the decay of cosmic muons is selected with a purity of 95%. This sample is used to calibrate the low-energy electron energy scale with two techniques. An electron energy calibration based on a cosmic ray muon sample uses calibration constants derived from measured and simulated cosmic ray muon events. Another calibration technique makes use of the theoretically well-understood Michel electron energy spectrum to convert reconstructed charge to electron energy. In addition, the effects of detector response to low-energy electron energy scale and its resolution including readout electronics threshold effects are quantified. Finally, the relation between the theoretical and reconstructed low-energy electron energy spectra is derived, and the energy resolution is characterized. The low-energy electron selection presented here accounts for about 75% of the total electron deposited energy. After the addition of lost energy using a Monte Carlo simulation, the energy resolution improves from about 40% to 25% at 50 MeV. These results are used to validate the expected capabilities of the DUNE far detector to reconstruct low-energy electrons.3 MoreReceived 3 November 2022Accepted 27 April 2023DOI:https://doi.org/10.1103/PhysRevD.107.092012Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle interactionsPhysical SystemsElectronsLeptonsMuonsNeutrinosPositronsTechniquesMonte Carlo methodsNeutrino detectorsParticle acceleratorsParticle data analysisParticle decaysParticle detectorsParticles & Fields

Simulation study on physical parameters ruling unipolar resistance switching of sputter-deposited silicon oxide film on Si substrate

This paper performs Monte Carlo simulations to elucidate the physical parameters that rule the unipolar switching process in sputter-deposited Si oxide films, where the metal/sputter-deposited Si oxide film/Si substrate stack structure is assumed. Simulation parameters are based on the results of experiments performed in parallel. Generations of simple bond breaking, oxygen vacancies, metallic Si sites, and E″ centers are implemented in the simulation algorithm, where various chemical parameters are used to control bonding conditions. In this study, the impact of hole injection from the Si substrate on the switching operation is also discussed. All-positive voltage stress mode for both the electroforming process (or set process) and the reset process and all-negative voltage stress mode for both the electroforming process (or set process) and the reset process are compared in detail as to their effect on the film’s degradation process.The comparison of the two different stress modes reveals that the positive stress mode does not yield devices with stable, repeatable switching. On the other hand, the negative stress mode results in stable, repeatable switching. It is strongly suggested that the difference stems from the physical asymmetry of the electrode materials; that is, the energy spectra of electrons injected from the Si substrate has a wide range in the all-positive stress mode and the energy transfer efficiency from electrons injected from Si substrate to the atomic bonding sites is small due to the large tunnel probability, which does not result in the successful switching of the Si oxide film. The role of hole injection from the n-Si substrate on the negative-stress-mode switching process is also discussed. These new findings should contribute to the design methodology of such resistance switching devices.

Efficient coupling between free electrons and the supermode of a silicon slot waveguide.

Laser light can modulate the kinetic energy spectrum of free electrons and induce extremely high acceleration gradients, which are instrumental to electron microscopy and electron acceleration, respectively. We present a design scheme for a silicon photonic slot waveguide which hosts a supermode to interact with free electrons. The efficiency of this interaction relies on the coupling strength per photon along the interaction length. We predict an optimum value of 0.4266, resulting in the maximum energy gain of 28.27 keV for an optical pulse energy of only 0.22 nJ and duration 1 ps. The acceleration gradient is 1.05 GeV/m, which is lower than the maximum imposed by the damage threshold of Si waveguides. Our scheme shows how the coupling efficiency and energy gain can be maximized without maximizing the acceleration gradient. It highlights the potential of silicon photonics technology in hosting electron-photon interactions with direct applications in free-electron acceleration, radiation sources, and quantum information science.

Cd113 β -decay spectrum and gA quenching using spectral moments

We present an alternative analysis of the $^{113}\mathrm{Cd}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay electron energy spectrum in terms of spectral moments ${\ensuremath{\mu}}_{n}$, corresponding to the averaged values of $n\mathrm{th}$ powers of the $\ensuremath{\beta}$ particle energy. The zeroth moment ${\ensuremath{\mu}}_{0}$ is related to the decay rate, while higher moments ${\ensuremath{\mu}}_{n}$ are related to the spectrum shape. The here advocated spectral-moment method (SMM) allows for a complementary understanding of previous results, obtained using the so-called spectrum-shape method (SSM) and its revised version, in terms of two free parameters: $r={g}_{\mathrm{A}}/{g}_{\mathrm{V}}$ (the ratio of axial-vector to vector couplings) and $s$ (the small vectorlike relativistic nuclear matrix element, $s$-NME). We present numerical results for three different nuclear models with the conserved vector current hypothesis (CVC) assumption of ${g}_{\mathrm{V}}=1$. We show that most of the spectral information can be captured by the first few moments, which are simple quadratic forms (conic sections) in the $(r,\phantom{\rule{0.16em}{0ex}}s)$ plane: An ellipse for $n=0$ and hyperbolas for $n\ensuremath{\ge}1$, all being nearly degenerate as a result of cancellations among nuclear matrix elements. The intersections of these curves, as obtained by equating theoretical and experimental values of ${\ensuremath{\mu}}_{n}$, identify the favored values of $(r,\phantom{\rule{0.16em}{0ex}}s)$ at a glance, without performing detailed fits. In particular, we find that values around $r\ensuremath{\approx}1$ and $s\ensuremath{\approx}1.6$ are consistently favored in each nuclear model, confirming the evidence for ${g}_{\mathrm{A}}$ quenching in $^{113}\mathrm{Cd}$, and shedding light on the role of the $s$-NME. We briefly discuss future applications of the SMM to other forbidden $\ensuremath{\beta}$-decay spectra sensitive to ${g}_{\mathrm{A}}$.

Effects of Coupling Action of Load and Temperature on the Lubricity of Coke Powder

By introducing the coke powder into the friction pair, the effects of load and temperature on the lubricity of coke powder at the frictional interface are studied. Before the test, the microcrystalline structures of coke powder at different temperatures are characterized by X-ray diffraction (XRD). After the test, the friction surfaces are observed by electron microscope and energy spectrum, the oxide compositions of friction surface are characterized by XRD, and the lubrication mechanism of coke powder is investigated. The results show that at RT (room temperature), as the load increases, the forming of the powder layer gradually deteriorates. When the load is 5 MPa, at a low temperature, the powder layer is thicker, and the coke powder exhibits better lubricity. In contrast, at a high temperature, affected by the temperature, the lubricity of coke powder declines, and the friction coefficient is higher.

Genesis of thunderstorm ground enhancements

Proceeding from a stormy day of 22 September 2022, when 7 thunderstorm ground enhancements occurred (TGEs, 3 of them very large), we perform an analysis of the most important conditions, on which depend the origination of the large particle fluxes in the thunderous atmosphere. Among these conditions are the near-surface electric field (NSEF), graupel fall, and lightning activity. We estimate the intensity of the largest particle flux of 1,25 mln gamma rays hitting each square meter of surface on Aragats with energy spectra extended up to 70 MeV. Only one TGE from 7 meets the conditions to recover the electron energy spectrum; the fraction of electrons with energies above 10 MeV relative to the gamma ray flux reaches 45%. By carefully examining the graupel fall, we demonstrate that the lower dipole, which accelerates electrons, is formed by the main negative and lower positively charged regions. The lower dipole decays with a graupel fall that coincides with TGE terminations (usually by a lightning flash).

On the electron spin and spectrum energy problems within the Fock many temporal and Feynman proper time paradigms

The quantum electron spin structure and the photon dressed electron energy spectrum problem are reanalyzed in the framework of the Fock many-temporal parameter approach. There is analyzed the spin structure and its dependence on the symmetry properties of the related representations of the basic Clifford algebra, generated by creation-annihilation operators. The self-interaction phenomenon is discussed within the quantum renormalized Lorenz constraint on a suitably reduced Fock space. The electron energy spectrum is analyzed within the many-temporal Fock and Feynman proper time paradigms.

Statistical study of type III bursts and associated HXR emissions

Context. Flare-accelerated electrons may produce closely temporarily related hard X-ray (HXR) emission while interacting with the dense solar atmosphere and radio type III bursts when propagating from the low corona to the interplanetary medium. The link between these emissions has been studied in previous studies. We present here new results on the correlation between the number and spectrum of HXR-producing electrons and the type III characteristics (flux, starting frequency). Aims. The aim of this study is to extend the results from previous statistical studies of radio type III bursts and associated HXR emissions: in particular, to determine what kind of correlation, if any, exists between the HXR-emitting electron numbers and the radio flux, as well as whether any correlations between the electron numbers or energy spectra are deduced from associated HXR emissions and type III starting (stopping) frequencies. Methods. This study is based on thirteen years of data between 2002 and 2014. We shortlisted ≃200 events with a close temporal association between HXR emissions and radio type III bursts in the 450–150 MHz range. We used X-ray flare observations from RHESSI and Fermi/GBM to calculate the number of electrons giving rise to the observed X-ray flux and observations from the Nançay Radioheliograph to calculate the peak radio flux at different frequencies in the 450–150 MHz range. Under the assumption of thick-target emissions, the number of HXR-producing electrons and their energy spectra were computed. The correlation between electron numbers, power-law indices, and the peak radio fluxes at different frequencies were analysed as well as potential correlations between the electron numbers and starting frequency of the radio burst. Bootstrap analysis for the correlation coefficients was performed to quantify the statistical significance of the fit. Results. The correlation between the number of HXR electrons and the peak flux of the type III emission decreases with increasing frequency. This correlation is larger when considering the electron number above 20 keV rather than the electron number above 10 keV. A weak anti-correlation is also found between the absolute value of the electron spectral index and the peak radio flux at 228 MHz. A rough correlation is found between the HXR-producing electron number above 20 keV and the type III starting frequency. This correlation is smaller if the electron number above 10 keV is considered. All the results are discussed in the framework of results from previous studies and in the context of numerical simulations of bump-in-tail instabilities and subsequent radio emissions.

Diagnosis of fast electron transport by coherent transition radiation

Transport of fast electrons in overdense plasmas is of key importance in high energy density physics. However, it is challenging to diagnose the fast electron transport in experiments. In this article, we study coherent transition radiation (CTR) generated by fast electrons on the back surface of the target by using 2D and 3D first-principle particle-in-cell (PIC) simulations. In our simulations, aluminum targets of 2.7 g cc−1 are simulated in two different situations by using a newly developed high order implicit PIC code. Comparing realistic simulations containing collision and ionization effects, artificial simulations without taking collision and ionization effects into account significantly underestimate the energy loss of electron beams when transporting in the target, which fail to describe the complete characteristics of CTR produced by electron beams on the back surface of the target. Realistic simulations indicate the diameter of CTR increases when the thickness of the target is increased. This is attributed to synergetic energy losses of high flux fast electrons due to Ohm heating and colliding drags, which appear quite significant even when the thickness of the solid target only differs by micrometers. Especially, when the diagnosing position is fixed, we find that the intensity distribution of the CTR is also a function of time, with the diameter increased with time. As the diameter of CTR is related to the speed of electrons passing through the back surface of the target, our finding may be used as a new tool to diagnose the electron energy spectra near the surface of solid density plasmas.

Breeding, Biosorption Characteristics, and Mechanism of a Lead-Resistant Strain.

To effectively carry out the bioremediation of a Pb2+ polluted environment, a lead-tolerant strain named D1 was screened from the activated sludge of a factory in Hefei, and its lead removal in a solution with Pb2+ concentration of 200 mg/L could reach 91% under optimal culture conditions. Morphological observation and 16S rRNA gene sequencing were used to identify D1 accurately, and its cultural characteristics and lead removal mechanism were also preliminarily studied. The results showed that the D1 strain was preliminarily identified as the Sphingobacterium mizutaii strain. The experiments conducted via orthogonal test showed that the optimal conditions for the growth of strain D1 were pH 7, inoculum volume 6%, 35 °C, and rotational speed 150 r/min. According to the results of scanning electron microscopy and energy spectrum analysis before and after the D1 exposure to lead, it is believed that the lead removal mechanism of D1 is surface adsorption. The Fourier transform infrared spectroscopy (FTIR) results revealed that multiple functional groups on the surface of the bacterial cells are involved in the Pb adsorption process. In conclusion, the D1 strain has excellent application prospects in the bioremediation of lead-contaminated environments.

The influence of CO2 partial pressure on the stability of dawsonite-based on water-rock physical experiment and numerical simulation

Dawsonite has the potential to serve as a significant mineral for carbon sequestration in geological storage, and its stability in the reservoir is determined by intricate fluid-rock interactions. Thus, it is crucial to elucidate the mechanism that influences the stability of dawsonite. In this study, a natural dawsonite-bearing sandstone in Dongying Sag was utilized for CO2–H2O-Rock interaction experiments and TOUGHREACT numerical simulations at varying CO2 pressures. Additionally, the CO2 fugacity value acting on the sandstone in the reactor experiment was corrected using thermodynamic analysis. By systematically analyzing the dissolution response and elemental composition evolution of dawsonite through techniques such as scanning electron microscopy observation and energy spectrum analysis, X-ray diffraction analysis, hydrochemical analysis, and dawsonite stability indicator parameters, the influence mode on the stability of dawsonite was clarified. The atomic ratio of dawsonite in each experimental group (between Al:O = 1:3 and Al:O = 1:2) suggested that gibbsite and boehmite were formed after the dissolution of dawsonite under high CO2 pressure. When pCO2≤7.3 MPa or pCO2＞8.3 MPa, increasing the CO2 pressure could enhance the thermal stability of dawsonite and inhibit its decomposition. However, when pCO2 was between 7.3 MPa and 8.3 MPa, the reaction equilibrium was disrupted, and a considerable amount of dawsonite was dissolved and transformed into new minerals. Both physical experimentation and numerical simulation indicated that dawsonite achieved a stable state at pCO2 = 7.3 MPa and 120 °C.

Study on Mechanism of Influence of Microstructure on Combustion Characteristics of Mine Conveyor Belt

ABSTRACT The disaster regularity of conveyor belt fire has always been the focus of mine fire prevention and control. In order to study the pyrolysis and combustion characteristics of different types of conveyor belts, the BET model was used to calculate the specific surface area and pore size distribution of conveyor belts. Various chemical bonds or functional groups contained in different types of conveyor belts were tested by infrared spectrum, and the structural parameters of infrared spectrum were calculated by split-peak fitting, so as to quantitatively analyze the change rule of the content of each active functional group. The microscopic morphology and element information of different types of conveyor belts were systematically studied by means of scanning electron microscope and energy spectrum analysis, which laid the foundation for the pyrolysis and combustion experiments of conveyor belts. The experimental results show that the order of specific surface area and average pore size is NFR>SC>PVC>PVG; The degree of hydroxyl oxidation of NFR and lignite samples is higher, and the degree of fat branching of NFR and PVG samples is higher, indicating that the samples have less soluble organic matter and loose structure; SC and NFR powder have similar internal space structure, but NFR conveyor belt has more hole structure than SC conveyor belt; The biggest difference between conveyor belt and lignite is the existence of Cl element. The derivative of Cl element can be considered as an early warning indicator of conveyor belt combustion.

Electron states in metalized ultrathin film crystals and their thermodynamic behavior

The dispersion law of electron in ultrathin crystalline metal-like film structures was found and analyzed using the method of two-time and temperature-dependent Green’s functions. Unlike unbounded (bulk) structures of the same crystallographic composition, the energy spectra of electrons in the film is strictly discrete, have two gaps and the narrower range of electron energies. Also, the conditions for the appearance and existence of localized electronic states as a function of boundary parameters were investigated. The probability of finding electrons in localized states is higher at more perturbed film boundaries. The electronic contribution to specific heat and entropy depends linearly on temperature, as in bulk structures, but with a different slope coefficient, so it follows that the electronic gas in films is a less ordered system and is closer to the equilibrium state than the same in bulk structures. These results could provide an explanation for the experimental facts about the stronger superconducting properties of ultrathin thin films.

Particle-in-Cell Modeling of Omega Experiments on Ablation of Plasmas

The large electric fields due to charge separation generated by a laser pulse propagating in a plasma can accelerate the electrons to very high energies. The hydrodynamics models that are based on the local thermodynamic equilibrium assuming a Maxwellian distribution of velocities cannot describe the evolution of groups of hot electrons of different energy ranges and kinetic particle-in-cell (PIC) simulations are required. The SMILEI PIC code is used to investigate the generation of hot electrons in plasmas produced by laser pulses in the Omega extended performance (EP) experiments. In 2-D PIC simulation using SMILEI code, a Gaussian-shaped laser pulse of 100-ps duration with the intensity of 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{15}$</tex-math> </inline-formula> W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$</tex-math> </inline-formula> and a wavelength of 351 nm impinges onto a plasma with the electron density and temperature profiles. The electromagnetic field, electron, and total energies of a plasma as a function of time are evaluated. The evolution of number density, electromagnetic fields, and energy spectra of electrons is studied. The time evolution of hot electrons in a plasma is investigated. These PIC results provide insights into the contribution and importance of the kinetic effects in the expansion dynamics of ablated plasmas, thereby helping to analyze and explain the Omega experimental data and computational fluid dynamics results.

Monte Carlo modelling and validation of the elekta synergy medical linear accelerator equipped with radiosurgical cones

Monte Carlo simulations of medical linear accelerator heads help in visualizing the energy spectrum and angular spread of photons and electrons, energy deposition, and scattering from each of the head components. Hence, the purpose of this study was to validate the Monte Carlo model of the Elekta synergy medical linear accelerator equipped with stereotactic radio surgical connical collimators. For this, the Elekta synergy medical linear accelerator was modelled using the EGSnrc Monte Carlo code. The model results were validated using the measured data. The primary electron beam parameters, beam size, and energy were tuned to match the measured data; a dose profile with a field size of 40 × 40 cm2 and percentage depth dose with a field size of 10 × 10 cm2 were matched during tuning. The validation of the modelled data with the measurement results was performed using gamma analysis, point dose, and field size comparisons. For small radiation fields, relative output factors were also compared. The gamma analysis revealed good agreement between the Monte Carlo modeling results and the measured data. A gamma pass rate of more than 95% was obtained for field sizes of 40 × 40 cm2 to 2 × 2 cm2 with gamma criteria of 1% and 1 mm for the dose difference (DD) and distance to agreement (DTA), respectively; this gamma pass rate was more than 98% for the corresponding values of 2% and 2 mm for the DD and DTA, respectively. A gamma pass rate of more than 99% was obtained for a percentage depth dose with 1 mm and 1% criteria. The field size was also in good agreement with the measurement results, and the maximum deviation observed was 1.1%. The stereotactic cone field also passed this analysis with a gamma pass rate of more than 98% for dose profiles and 99% for the percentage depth dose. The small field output factor exhibited a deviation of 4.3%, 3.4%, and 1.9% for field sizes of 5 mm, 7.5 mm, and 10 mm, respectively. Thus, the Monte Carlo model of the Elekta Linear accelerator was successfully validated. The validation of radio surgical cones passed the analysis in terms of the dose profiles and percentage depth dose. The small field relative output factors exhibited deviations of up to 4.3%, and to resolve this, detector-specific and field-specific correction factors must be derived.