Electron conductivity model for dense plasmas

International Nuclear Information System (INIS)

Lee, Y.T.; More, R.M.

1984-01-01

An electron conductivity model for dense plasmas is described which gives a consistent and complete set of transport coefficients including not only electrical conductivity and thermal conductivity, but also thermoelectric power, and Hall, Nernst, Ettinghausen, and Leduc--Righi coefficients. The model is useful for simulating plasma experiments with strong magnetic fields. The coefficients apply over a wide range of plasma temperature and density and are expressed in a computationally simple form. Different formulas are used for the electron relaxation time in plasma, liquid, and solid phases. Comparisons with recent calculations and available experimental measurement show the model gives results which are sufficiently accurate for many practical applications

Monoenergetic electron parameters in a spheroid bubble model

International Nuclear Information System (INIS)

Sattarian, H.; Rahmatallahpur, Sh.; Tohidi, T.

2013-01-01

A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived. The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately, especially at the relativistic region. The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model. The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons ΔE/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions. As a result, the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model. (physics of gases, plasmas, and electric discharges)

Models for the transport of low energy electrons in water and the yield of hydrated electrons at early times

International Nuclear Information System (INIS)

Brenner, D.J.; Miller, J.H.; Ritchie, R.H.; Bichsel, H.

1985-01-01

An insulator model with four experimental energy bands was used to fit the optical properties of liquid water and to extend these data to non-zero momentum transfer. Inelastic mean free paths derived from this dielectric response function provided the basic information necessary to degrade high energy electrons to the subexcitation energy domain. Two approaches for the transport of subexcitation electrons were investigated. (i) Gas phase cross sections were used to degrade subexcitation electrons to thermal energy and the thermalization lengths were scaled to unit density. (ii) Thermalization lengths were estimated by age-diffusion theory with a stopping power deduced from the data on liquid water and transport cross sections derived from elastic scattering in water vapor. Theoretical ranges were compared to recent experimental results. A stochastic model was used to calculate the rapid diffusion and reaction of hydrated electrons with other radiolysis products. The sensitivity of the calculated yields to the model assumptions and comparison with experimental data are discussed

Simulation model for electron irradiated IGZO thin film transistors

Science.gov (United States)

Dayananda, G. K.; Shantharama Rai, C.; Jayarama, A.; Kim, Hyun Jae

2018-02-01

An efficient drain current simulation model for the electron irradiation effect on the electrical parameters of amorphous In-Ga-Zn-O (IGZO) thin-film transistors is developed. The model is developed based on the specifications such as gate capacitance, channel length, channel width, flat band voltage etc. Electrical parameters of un-irradiated IGZO samples were simulated and compared with the experimental parameters and 1 kGy electron irradiated parameters. The effect of electron irradiation on the IGZO sample was analysed by developing a mathematical model.

An experimental electronic model for a neuronal cell

International Nuclear Information System (INIS)

Campos-Cantón, I; Martel-Gallegos, G; Rangel-López, A; Vertiz-Hérnandez, A; Zarazúa, S

2014-01-01

Over the last two decades, the study of information transmission in living beings has acquired great relevance, because it regulates and conducts the functioning of all of the organs in the body. In information transmission pathways, the neuron plays an important role in that it receives, transmits, and processes electrical signals from different parts of the human body; these signals are transmitted as electrical impulses called action potentials, and they transmit information from one neuron to another. In this work, and with the aim of developing experiments for teaching biological processes, we implemented an electronic circuit of the neuron cell device and its mathematical model based on piecewise linear functions. (paper)

Two-parametric model of electron beam in computational dosimetry for radiation processing

International Nuclear Information System (INIS)

Lazurik, V.M.; Lazurik, V.T.; Popov, G.; Zimek, Z.

2016-01-01

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

Experimental Investigation of Runaway Electron Generation in Textor

NARCIS (Netherlands)

R. Jaspers,; Finken, K.H.; Mank, G.; Hoenen, F.; Boedo, J. A.; Cardozo, N. J. L.; Schüller, F. C.

1993-01-01

An experimental study of the generation of runaway electrons in TEXTOR has been performed. From the infrared synchrotron radiation emitted by relativistic electrons, the number of runaway electrons can be obtained as a function of time. In low density discharges (n(e)BAR < 1 X 10(19) m-3)

USign--a security enhanced electronic consent model.

Science.gov (United States)

Li, Yanyan; Xie, Mengjun; Bian, Jiang

2014-01-01

Electronic consent becomes increasingly popular in the healthcare sector given the many benefits it provides. However, security concerns, e.g., how to verify the identity of a person who is remotely accessing the electronic consent system in a secure and user-friendly manner, also arise along with the popularity of electronic consent. Unfortunately, existing electronic consent systems do not pay sufficient attention to those issues. They mainly rely on conventional password based authentication to verify the identity of an electronic consent user, which is far from being sufficient given that identity theft threat is real and significant in reality. In this paper, we present a security enhanced electronic consent model called USign. USign enhances the identity protection and authentication for electronic consent systems by leveraging handwritten signatures everyone is familiar with and mobile computing technologies that are becoming ubiquitous. We developed a prototype of USign and conducted preliminary evaluation on accuracy and usability of signature verification. Our experimental results show the feasibility of the proposed model.

Comparison of experimental slant electron content and IRI model for moderate solar activity conditions

International Nuclear Information System (INIS)

Cabrera, M.A.; Ezquer, R.G.; Mosert, M.; Jadur, C.A.

2002-01-01

The International Reference Ionosphere model only gives the vertical electron content (VTEC). In this paper the slant electron content (SEC) for the ATS 6 satellite - Palehua (21.4 deg. N, 201.9 deg. E) radio signal path for a middle solar activity year is calculated. To this end, IRI model is used to obtain the electron density at different points of the signal path. Equinoxes and solstices are considered. Measurements obtained with Faraday rotation technique at Palehua are compared with the modelled values. Although overestimation was observed for night hours, the results show good SEC predictions for several hours at period of maximum ionisation, suggesting that would be possible to model the STEC using IRI. (author)

Modeling laser-driven electron acceleration using WARP with Fourier decomposition

Energy Technology Data Exchange (ETDEWEB)

Lee, P., E-mail: patrick.lee@u-psud.fr [LPGP, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France); Audet, T.L. [LPGP, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France); Lehe, R.; Vay, J.-L. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Maynard, G.; Cros, B. [LPGP, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)

2016-09-01

WARP is used with the recent implementation of the Fourier decomposition algorithm to model laser-driven electron acceleration in plasmas. Simulations were carried out to analyze the experimental results obtained on ionization-induced injection in a gas cell. The simulated results are in good agreement with the experimental ones, confirming the ability of the code to take into account the physics of electron injection and reduce calculation time. We present a detailed analysis of the laser propagation, the plasma wave generation and the electron beam dynamics.

Prediction Model for Relativistic Electrons at Geostationary Orbit

Science.gov (United States)

Khazanov, George V.; Lyatsky, Wladislaw

2008-01-01

We developed a new prediction model for forecasting relativistic (greater than 2MeV) electrons, which provides a VERY HIGH correlation between predicted and actually measured electron fluxes at geostationary orbit. This model implies the multi-step particle acceleration and is based on numerical integrating two linked continuity equations for primarily accelerated particles and relativistic electrons. The model includes a source and losses, and used solar wind data as only input parameters. We used the coupling function which is a best-fit combination of solar wind/interplanetary magnetic field parameters, responsible for the generation of geomagnetic activity, as a source. The loss function was derived from experimental data. We tested the model for four year period 2004-2007. The correlation coefficient between predicted and actual values of the electron fluxes for whole four year period as well as for each of these years is stable and incredibly high (about 0.9). The high and stable correlation between the computed and actual electron fluxes shows that the reliable forecasting these electrons at geostationary orbit is possible.

Experimental core electron density of cubic boron nitride

DEFF Research Database (Denmark)

Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse

as well as experimental result. The redistribution of electron density will, if not accounted for, result in increased thermal parameters. It is estimated that 1.7-2 electrons is transferred from boron to nitrogen. [1]: N. Bindzus, T. Straasø, N. Wahlberg, J. Becker, L. Bjerg, N. Lock, A.-C. Dippel, and B......Experimental core electron density of cubic boron nitride Nanna Wahlberg*, Niels Bindzus*, Lasse Bjerg*, Jacob Becker*, and Bo B. Iversen* *Aarhus University, Department of Chemistry, CMC, Langelandsgade 140, 8000 Århus, Denmark The resent progress in powder diffraction provides data of quality...... obtained. The displacement parameters reported here are significantly lower than those previously reported, stressing the importance of an adequate description of the core density. The charge transfer from boron to nitrogen clearly affects the inner electron density, which is evident from theoretical...

Experimental determination of the electron-avalanche and the electron-ion recombination coefficient

NARCIS (Netherlands)

Ernst, G.J.; Boer, A.G.

1980-01-01

The electron-ion recombination coefficient γ and the avalanche coefficient δ = (α − a) · vd, where α and a are the ionizat ion and attachment coefficients respectively and vd the drift velocity of the electrons, have been experimentally determined in a self-sustained CO2-laser system (1:1:3 mixture)

Effect of electron beam radiations on anxiety in experimental animal models

International Nuclear Information System (INIS)

Deepa, B; Suchetha Kumari; Sanjeev, Ganesh; Rao, Satheesh

2013-01-01

Exposures to ionizing radiation have been an inevitable part of the environment. This type of radiation can disrupt atoms, creating positive and negative charged particles, and cause biological harm. Ionizing radiation includes X-rays, gamma rays, alpha particles, beta particles and neutrons. They have the potential to cause both beneficial and harmful effects. There are concerns about these radiations as they are widely used in hospitals for treatment and diagnosis of various diseases. The present work was designed to test the effect of whole body electron beam radiation on anxiety in mice using the Elevated plus maze and Light dark arena, the commonly used models for assessing anxiety in rodents. Mice were irradiated with three different doses (2 Gy, 4 Gy and 6 Gy) of electron beam radiations. Statistical analysis revealed that whole body irradiation of the moderate dose range (2-6 Gy) of electron beam leads to a significant (p<0.001) anxiogenic activity in irradiated mice. Electron beam induced anxiety can be due to radiation induced reactive oxygen species in brain. (author)

Experimental evidence of nitrous acid formation in the electron beam treatment of flue gas

International Nuclear Information System (INIS)

Maetzing, H.; Namba, H.; Tokunaga, O.

1994-01-01

In the Electron Beam Dry Scrubbing (EBDS) process, flue gas from fossil fuel burning power plants is irradiated with accelerated (300-800 keV) electrons. Thereby, nitrogen oxide (NO x ) and sulfur dioxide (SO 2 ) traces are transformed into nitric and sulfuric acids, respectively, which are converted into particulate ammonium nitrate and sulfate upon the addition of ammonia. The powdery product can be filtered from the main gas stream and can be sold as agricultural fertilizer. A lot of experimental investigations have been performed on the EBDS process and computer models have been developed to interpret the experimental results and to predict economic improvements. According to the model calculations, substantial amounts of intermediate nitrous acid (HNO 2 ) are formed in the electron beam treatment of flue gas. The first experimental investigation about the formation of nitrous acid in an irradiated mixture of NO in synthetic air has been undertaken. Under these conditions, aerosol formation is avoided. UV spectra of the irradiated gas were recorded in the wavelength range λ = 345-375 nm. Both NO 2 and HNO 2 have characteristic absorption bands in this wavelength range. Calibration spectra of NO 2 were subtracted from the sample spectra. The remaining absorption bands can clearly be assigned to nitrous acid. The concentration of nitrous acid was determined by differential optical absorption. It was found lower than the model prediction. The importance of nitrous acid formation in the EBDS process needs to be clarified. (author)

A new theoretical model for scattering of electrons by molecules. 1

International Nuclear Information System (INIS)

Peixoto, E.M.A.; Mu-tao, L.; Nogueira, J.C.

1975-01-01

A new theoretical model for electron-molecule scattering is suggested. The e-H 2 scattering is studied and the superiority of the new model over the commonly used Independent Atom Model (IAM) is demonstrated. Comparing theoretical and experimental data for 40keV electrons scattered by H 2 utilizing the new model, its validity is proved, while Partial Wave and First Born calculations, employing the Independent Atom Model, strongly deviated from the experiment [pt

Off-axis and inline electron holography: Experimental comparison

International Nuclear Information System (INIS)

Latychevskaia, Tatiana; Formanek, Petr; Koch, C.T.; Lubk, Axel

2010-01-01

Electron holography is a very powerful technique for mapping static electric and magnetic potentials down to atomic resolution. While electron holography is commonly considered synonymous with its off-axis variant in the high energy electron microscopy community, inline electron holography is widely applied in low-energy electron microscopy, where the realization of the off-axis setup is still an experimental challenge. This paper demonstrates that both inline and off-axis holography may be used to recover amplitude and phase shift of the very same object, in our example latex spheres of 90 and 200 nm in diameter, producing very similar results, provided the object does not charge under the electron beam.

Experimental and theoretical electron-scattering cross-section data for dichloromethane

Science.gov (United States)

Krupa, K.; Lange, E.; Blanco, F.; Barbosa, A. S.; Pastega, D. F.; Sanchez, S. d'A.; Bettega, M. H. F.; García, G.; Limão-Vieira, P.; Ferreira da Silva, F.

2018-04-01

We report on a combination of experimental and theoretical investigations into the elastic differential cross sections (DCSs) and integral cross sections for electron interactions with dichloromethane, C H2C l2 , in the incident electron energy over the 7.0-30 eV range. Elastic electron-scattering cross-section calculations have been performed within the framework of the Schwinger multichannel method implemented with pseudopotentials (SMCPP), and the independent-atom model with screening-corrected additivity rule including interference-effects correction (IAM-SCAR+I). The present elastic DCSs have been found to agree reasonably well with the results of IAM-SCAR+I calculations above 20 eV and also with the SMC calculations below 30 eV. Although some discrepancies were found for 7 eV, the agreement between the two theoretical methodologies is remarkable as the electron-impact energy increases. Calculated elastic DCSs are also reported up to 10000 eV for scattering angles from 0° to 180° together with total cross section within the IAM-SCAR+I framework.

Experimental Observation of a Current-Driven Instability in a Neutral Electron-Positron Beam

Science.gov (United States)

Warwick, J.; Dzelzainis, T.; Dieckmann, M. E.; Schumaker, W.; Doria, D.; Romagnani, L.; Poder, K.; Cole, J. M.; Alejo, A.; Yeung, M.; Krushelnick, K.; Mangles, S. P. D.; Najmudin, Z.; Reville, B.; Samarin, G. M.; Symes, D. D.; Thomas, A. G. R.; Borghesi, M.; Sarri, G.

2017-11-01

We report on the first experimental observation of a current-driven instability developing in a quasineutral matter-antimatter beam. Strong magnetic fields (≥1 T ) are measured, via means of a proton radiography technique, after the propagation of a neutral electron-positron beam through a background electron-ion plasma. The experimentally determined equipartition parameter of ɛB≈10-3 is typical of values inferred from models of astrophysical gamma-ray bursts, in which the relativistic flows are also expected to be pair dominated. The data, supported by particle-in-cell simulations and simple analytical estimates, indicate that these magnetic fields persist in the background plasma for thousands of inverse plasma frequencies. The existence of such long-lived magnetic fields can be related to analog astrophysical systems, such as those prevalent in lepton-dominated jets.

Low dose CT simulation using experimental noise model

Energy Technology Data Exchange (ETDEWEB)

Nakanishi, Satori; Zamyatin, Alexander A. [Toshiba Medical Systems Corporation, Tochigi, Otawarashi (Japan); Silver, Michael D. [Toshiba Medical Research Institute, Vernon Hills, IL (United States)

2011-07-01

We suggest a method to obtain system noise model experimentally without relying on assumptions on statistical distribution of the noise; also, knowledge of DAS gain and electronic noise level are not required. Evaluation with ultra-low dose CT data (5 mAs) shows good match between simulated and real data noise. (orig.)

Enhanced angular overlap model for nonmetallic f -electron systems

Science.gov (United States)

Gajek, Z.

2005-07-01

An efficient method of interpretation of the crystal field effect in nonmetallic f -electron systems, the enhanced angular overlap model (EAOM), is presented. The method is established on the ground of perturbation expansion of the effective Hamiltonian for localized electrons and first-principles calculations related to available experimental data. The series of actinide compounds AO2 , oxychalcogenides AOX , and dichalcogenides UX2 where X=S ,Se,Te and A=U ,Np serve as probes of the effectiveness of the proposed method. An idea is to enhance the usual angular overlap model with ab initio calculations of those contributions to the crystal field potential, which cannot be represented by the usual angular overlap model (AOM). The enhancement leads to an improved fitting and makes the approach intrinsically coherent. In addition, the ab initio calculations of the main, AOM-consistent part of the crystal field potential allows one to fix the material-specific relations for the EAOM parameters in the effective Hamiltonian. Consequently, the electronic structure interpretation based on EAOM can be extended to systems of the lowest point symmetries or/and deficient experimental data. Several examples illustrating the promising capabilities of EAOM are given.

Numerical model of the plasma formation at electron beam welding

Energy Technology Data Exchange (ETDEWEB)

Trushnikov, D. N., E-mail: trdimitr@yandex.ru [The Department for Applied Physics, Perm National Research Polytechnic University, Perm 614990 (Russian Federation); The Department for Welding Production and Technology of Constructional Materials, Perm National Research Polytechnic University, Perm 614990 (Russian Federation); Mladenov, G. M., E-mail: gmmladenov@abv.bg [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Shose, 1784 Sofia (Bulgaria); Technology Centre of Electron Beam and Plasma Technologies and Techniques, 68-70 Vrania, ap.10, Banishora, 1309 Sofia (Bulgaria)

2015-01-07

The model of plasma formation in the keyhole in liquid metal as well as above the electron beam welding zone is described. The model is based on solution of two equations for the density of electrons and the mean electron energy. The mass transfer of heavy plasma particles (neutral atoms, excited atoms, and ions) is taken into account in the analysis by the diffusion equation for a multicomponent mixture. The electrostatic field is calculated using the Poisson equation. Thermionic electron emission is calculated for the keyhole wall. The ionization intensity of the vapors due to beam electrons and high-energy secondary and backscattered electrons is calibrated using the plasma parameters when there is no polarized collector electrode above the welding zone. The calculated data are in good agreement with experimental data. Results for the plasma parameters for excitation of a non-independent discharge are given. It is shown that there is a need to take into account the effect of a strong electric field near the keyhole walls on electron emission (the Schottky effect) in the calculation of the current for a non-independent discharge (hot cathode gas discharge). The calculated electron drift velocities are much bigger than the velocity at which current instabilities arise. This confirms the hypothesis for ion-acoustic instabilities, observed experimentally in previous research.

Experimental Observation of a Current-Driven Instability in a Neutral Electron-Positron Beam.

Science.gov (United States)

Warwick, J; Dzelzainis, T; Dieckmann, M E; Schumaker, W; Doria, D; Romagnani, L; Poder, K; Cole, J M; Alejo, A; Yeung, M; Krushelnick, K; Mangles, S P D; Najmudin, Z; Reville, B; Samarin, G M; Symes, D D; Thomas, A G R; Borghesi, M; Sarri, G

2017-11-03

We report on the first experimental observation of a current-driven instability developing in a quasineutral matter-antimatter beam. Strong magnetic fields (≥1  T) are measured, via means of a proton radiography technique, after the propagation of a neutral electron-positron beam through a background electron-ion plasma. The experimentally determined equipartition parameter of ε_{B}≈10^{-3} is typical of values inferred from models of astrophysical gamma-ray bursts, in which the relativistic flows are also expected to be pair dominated. The data, supported by particle-in-cell simulations and simple analytical estimates, indicate that these magnetic fields persist in the background plasma for thousands of inverse plasma frequencies. The existence of such long-lived magnetic fields can be related to analog astrophysical systems, such as those prevalent in lepton-dominated jets.

Engine modeling and control modeling and electronic management of internal combustion engines

CERN Document Server

Isermann, Rolf

2014-01-01

The increasing demands for internal combustion engines with regard to fuel consumption, emissions and driveability lead to more actuators, sensors and complex control functions. A systematic implementation of the electronic control systems requires mathematical models from basic design through simulation to calibration. The book treats physically-based as well as models based experimentally on test benches for gasoline (spark ignition) and diesel (compression ignition) engines and uses them for the design of the different control functions. The main topics are: - Development steps for engine control - Stationary and dynamic experimental modeling - Physical models of intake, combustion, mechanical system, turbocharger, exhaust, cooling, lubrication, drive train - Engine control structures, hardware, software, actuators, sensors, fuel supply, injection system, camshaft - Engine control methods, static and dynamic feedforward and feedback control, calibration and optimization, HiL, RCP, control software developm...

Experimental studies of VpxB electron linear accelerator

International Nuclear Information System (INIS)

Taura, T.; Onihashi, H.; Otsuka, K.; Nishida, Y.; Yugami, N.

1989-01-01

In order to demonstrate a new electron linear accelerator an electron beam is accelerated either in the conventional linear accelerator scheme or in the V p xB scheme in a same machine and higher energy gain of about 18 % is observed in the V p xB scheme as is expected from the designed values. The experimental results are compared with the numerical simulation to show reasonable agreement. (author)

Time-dependent approach to electron scattering and ionization in the s-wave model

International Nuclear Information System (INIS)

Ihra, W.; Draeger, M.; Handke, G.; Friedrich, H.

1995-01-01

The time-dependent Schroedinger equation is integrated for continuum states of two-electron atoms in the framework of the s-wave model, in which both electrons are restricted to having vanishing individual orbital angular momenta. The method is suitable for studying the time evolution of correlations in the two-electron wave functions and yields probabilities for elastic and inelastic electron scattering and for electron-impact ionization. The spin-averaged probabilities for electron-impact ionization of hydrogen in the s-wave model reproduce the shape of the experimentally observed integrated ionization cross section remarkably well for energies near and above the maximum

Modelling hot electron generation in short pulse target heating experiments

Directory of Open Access Journals (Sweden)

Sircombe N.J.

2013-11-01

Full Text Available Target heating experiments planned for the Orion laser facility, and electron beam driven fast ignition schemes, rely on the interaction of a short pulse high intensity laser with dense material to generate a flux of energetic electrons. It is essential that the characteristics of this electron source are well known in order to inform transport models in radiation hydrodynamics codes and allow effective evaluation of experimental results and forward modelling of future campaigns. We present results obtained with the particle in cell (PIC code EPOCH for realistic target and laser parameters, including first and second harmonic light. The hot electron distributions are characterised and their implications for onward transport and target heating are considered with the aid of the Monte-Carlo transport code THOR.

Modelling of non-thermal electron cyclotron emission during ECRH

International Nuclear Information System (INIS)

Tribaldos, V.; Krivenski, V.

1990-01-01

The existence of suprathermal electrons during Electron Cyclotron Resonance Heating experiments in tokamaks is today a well established fact. At low densities the creation of large non-thermal electron tails affects the temperature profile measurements obtained by 2 nd harmonic, X-mode, low-field side, electron cyclotron emission. At higher densities suprathermal electrons can be detected by high-field side emission. In electron cyclotron current drive experiments a high energy suprathermal tail, asymmetric in v, is observed. Non-Maxwellian electron distribution functions are also typically observed during lower-hybrid current drive experiments. Fast electrons have been observed during ionic heating by neutral beams as well. Two distinct approaches are currently used in the interpretation of the experimental results: simple analytical models which reproduce some of the expected non-Maxwellian characteristics of the electron distribution function are employed to get a qualitative picture of the phenomena; sophisticated numerical Fokker-Planck calculations give the electron distribution function from which the emission spectra are computed. No algorithm is known to solve the inverse problem, i.e. to compute the electron distribution function from the emitted spectra. The proposed methods all relay on the basic assumption that the electron distribution function has a given functional dependence on a limited number of free parameters, which are then 'measured' by best fitting the experimental results. Here we discuss the legitimacy of this procedure. (author) 7 refs., 5 figs

Experimental observation of exploding electron bubbles

International Nuclear Information System (INIS)

Classen, J.; Su, C.K.; Hall, S.C.; Pettersen, M.S.; Maris, H.J.

1996-01-01

Since free electrons form small voids in liquid helium they are expected to be preferred sites for nucleating macroscopic bubbles when the liquid is exposed to sufficiently large negative pressures. We have performed a series of cavitation experiments using focussed ultrasound where free electrons were introduced into the liquid by a radioactive source. The electron bubbles are found to explode at negative pressures significantly lower than those required for homogeneous nucleation. We present measurements of the thresholds for cavitation at electrons in the temperature range 1 - 4.5 K. Reasonable agreement with a simple model for the stability limit of the electron bubble is obtained. (author)

A kinetic model for runaway electrons in the ionosphere

Directory of Open Access Journals (Sweden)

G. Garcia

2006-09-01

Full Text Available Electrodynamic models and measurements with satellites and incoherent scatter radars predict large field aligned current densities on one side of the auroral arcs. Different authors and different kinds of studies (experimental or modeling agree that the current density can reach up to hundreds of µA/m2. This large current density could be the cause of many phenomena such as tall red rays or triggering of unstable ion acoustic waves. In the present paper, we consider the issue of electrons moving through an ionospheric gas of positive ions and neutrals under the influence of a static electric field. We develop a kinetic model of collisions including electrons/electrons, electrons/ions and electrons/neutrals collisions. We use a Fokker-Planck approach to describe binary collisions between charged particles with a long-range interaction. We present the essential elements of this collision operator: the Langevin equation for electrons/ions and electrons/electrons collisions and the Monte-Carlo and null collision methods for electrons/neutrals collisions. A computational example is given illustrating the approach to equilibrium and the impact of the different terms (electrons/electrons and electrons/ions collisions on the one hand and electrons/neutrals collisions on the other hand. Then, a parallel electric field is applied in a new sample run. In this run, the electrons move in the z direction parallel to the electric field. The first results show that all the electron distribution functions are non-Maxwellian. Furthermore, runaway electrons can carry a significant part of the total current density, up to 20% of the total current density.

Experimental Object-Oriented Modelling

DEFF Research Database (Denmark)

Hansen, Klaus Marius

through, e.g., technical prototyping and active user involvement. We introduce and examine “experimental object-oriented modelling” as the intersection of these practices. The contributions of this thesis are expected to be within three perspectives on models and modelling in experimental system...... development: Grounding We develop an empirically based conceptualization of modelling and use of models in system development projects characterized by a high degree of uncertainty in requirements and point to implications for tools and techniques for modelling in such a setting. Techniques We introduce......This thesis examines object-oriented modelling in experimental system development. Object-oriented modelling aims at representing concepts and phenomena of a problem domain in terms of classes and objects. Experimental system development seeks active experimentation in a system development project...

A theoretical model on surface electronic behavior: Strain effect

International Nuclear Information System (INIS)

Qin, W.G.; Shaw, D.

2009-01-01

Deformation from mechanical loading can affect surface electronic behavior. Surface deformation and electronic behavior can be quantitatively expressed using strain and work function, respectively, and their experimental relationship can be readily determined using the Kelvin probing technique. However, the theoretical correlation between work function and strain has been unclear. This study reports our theoretical exploration, for the first time, of the effect of strain on work function. We propose a simple electrostatic action model by considering the effect of a dislocation on work function of a one-dimensional lattice and further extend this model to the complex conditions for the effect of dislocation density. Based on this model, we established successfully a theoretical correlation between work function and strain.

Experimental Electron Cloud Studies in the CERN Proton Synchrotron

CERN Document Server

Mahner, E; Caspers, Friedhelm

2008-01-01

Indications for a beam-induced electron cloud build-up are observed since 2000 for the nominal LHC beam in the PS to SPS transfer line and during the last turns before ejection from the PS. A new electron cloud setup was designed, built, and installed in the PS. It contains shielded button-type pickups, a dipole magnet, a vacuum gauge, and a dedicated stripline electrode to experimentally verify the beneficial effect of electron cloud clearing electrodes. During the 2007 run, the electron cloud effect was also clearly observed in the PS and efficient electron cloud suppression has been obtained for negative and positive bias voltages on the clearing electrode. Here, we present electron cloud measurements with different filling patterns and bunch spacings in the PS.

A kinetic model for runaway electrons in the ionosphere

Directory of Open Access Journals (Sweden)

G. Garcia

2006-09-01

Full Text Available Electrodynamic models and measurements with satellites and incoherent scatter radars predict large field aligned current densities on one side of the auroral arcs. Different authors and different kinds of studies (experimental or modeling agree that the current density can reach up to hundreds of µA/m². This large current density could be the cause of many phenomena such as tall red rays or triggering of unstable ion acoustic waves. In the present paper, we consider the issue of electrons moving through an ionospheric gas of positive ions and neutrals under the influence of a static electric field. We develop a kinetic model of collisions including electrons/electrons, electrons/ions and electrons/neutrals collisions. We use a Fokker-Planck approach to describe binary collisions between charged particles with a long-range interaction. We present the essential elements of this collision operator: the Langevin equation for electrons/ions and electrons/electrons collisions and the Monte-Carlo and null collision methods for electrons/neutrals collisions. A computational example is given illustrating the approach to equilibrium and the impact of the different terms (electrons/electrons and electrons/ions collisions on the one hand and electrons/neutrals collisions on the other hand. Then, a parallel electric field is applied in a new sample run. In this run, the electrons move in the z direction parallel to the electric field. The first results show that all the electron distribution functions are non-Maxwellian. Furthermore, runaway electrons can carry a significant part of the total current density, up to 20% of the total current density.

Modeling power electronics and interfacing energy conversion systems

CERN Document Server

Simões, Marcelo Godoy

2017-01-01

Discusses the application of mathematical and engineering tools for modeling, simulation and control oriented for energy systems, power electronics and renewable energy. This book builds on the background knowledge of electrical circuits, control of dc/dc converters and inverters, energy conversion and power electronics. The book shows readers how to apply computational methods for multi-domain simulation of energy systems and power electronics engineering problems. Each chapter has a brief introduction on the theoretical background, a description of the problems to be solved, and objectives to be achieved. Block diagrams, electrical circuits, mathematical analysis or computer code are covered. Each chapter concludes with discussions on what should be learned, suggestions for further studies and even some experimental work.

Effect of Electron Seeding on Experimentally Measured Multipactor Discharge Threshold

Science.gov (United States)

Noland, Jonathan; Graves, Timothy; Lemon, Colby; Looper, Mark; Farkas, Alex

2012-10-01

Multipactor is a vacuum phenomenon in which electrons, moving in resonance with an externally applied electric field, impact material surfaces. If the number of secondary electrons created per primary electron impact averages more than unity, the resonant interaction can lead to an electron avalanche. Multipactor is a generally undesirable phenomenon, as it can cause local heating, absorb power, or cause detuning of RF circuits. In order to increase the probability of multipactor initiation, test facilities often employ various seeding sources such as radioactive sources (Cesium 137, Strontium 90), electron guns, or photon sources. Even with these sources, the voltage for multipactor initiation is not certain as parameters such as material type, RF pulse length, and device wall thickness can all affect seed electron flux and energy in critical gap regions, and hence the measured voltage threshold. This study investigates the effects of seed electron source type (e.g., photons versus beta particles), material type, gap size, and RF pulse length variation on multipactor threshold. In addition to the experimental work, GEANT4 simulations will be used to estimate the production rate of low energy electrons (< 5 keV) by high energy electrons and photons. A comparison of the experimental fluxes to the typical energetic photon and particle fluxes experienced by spacecraft in various orbits will also be made. Initial results indicate that for a simple, parallel plate device made of aluminum, there is no threshold variation (with seed electrons versus with no seed electrons) under continuous-wave RF exposure.

Numerical modelling and experimental study of liquid evaporation during gel formation

Science.gov (United States)

Pokusaev, B. G.; Khramtsov, D. P.

2017-11-01

Gels are promising materials in biotechnology and medicine as a medium for storing cells for bioprinting applications. Gel is a two-phase system consisting of solid medium and liquid phase. Understanding of a gel structure evolution and gel aging during liquid evaporation is a crucial step in developing new additive bioprinting technologies. A numerical and experimental study of liquid evaporation was performed. In experimental study an evaporation process of an agarose gel layer located on Petri dish was observed and mass difference was detected using electronic scales. Numerical model was based on a smoothed particle hydrodynamics method. Gel in a model was represented as a solid-liquid system and liquid evaporation was modelled due to capillary forces and heat transfer. Comparison of experimental data and numerical results demonstrated that model can adequately represent evaporation process in agarose gel.

A computer code package for Monte Carlo photon-electron transport simulation Comparisons with experimental benchmarks

International Nuclear Information System (INIS)

Popescu, Lucretiu M.

2000-01-01

A computer code package (PTSIM) for particle transport Monte Carlo simulation was developed using object oriented techniques of design and programming. A flexible system for simulation of coupled photon, electron transport, facilitating development of efficient simulation applications, was obtained. For photons: Compton and photo-electric effects, pair production and Rayleigh interactions are simulated, while for electrons, a class II condensed history scheme was considered, in which catastrophic interactions (Moeller electron-electron interaction, bremsstrahlung, etc.) are treated in detail and all other interactions with reduced individual effect on electron history are grouped together using continuous slowing down approximation and energy straggling theories. Electron angular straggling is simulated using Moliere theory or a mixed model in which scatters at large angles are treated as distinct events. Comparisons with experimentally benchmarks for electron transmission and bremsstrahlung emissions energy and angular spectra, and for dose calculations are presented

3D invariant embedding model for backscattering electrons applied to materials characterization

International Nuclear Information System (INIS)

Figueroa, C.; Nieva, N.; Heluani, S.P.

2007-01-01

In this work, the results of a 3D model used to describe the fraction of backscattered electrons, together with its energy and angular distributions, are reported. This 3D model is the result of improvements in the Invariant Embedding Approach to Microanalysis (IEAM). Comparisons with experiment show that the theoretical results follow the general trend of experimental data, when parameters (such as atomic number, energy of the impinging electrons and tilted angle) are changed

A combined experimental and analytical approach for interface fracture parameters of dissimilar materials in electronic packages

International Nuclear Information System (INIS)

Kay, N.R.; Ghosh, S.; Guven, I.; Madenci, E.

2006-01-01

This study concerns the development of a combined experimental and analytical technique to determine the critical values of fracture parameters for interfaces between dissimilar materials in electronic packages. This technique utilizes specimens from post-production electronic packages. The mechanical testing is performed inside a scanning electron microscope while the measurements are achieved by means of digital image correlation. The measured displacements around the crack tip are used as the boundary conditions for the analytical model to compute the energy release rate. The critical energy release rate values obtained from post-production package specimens are obtained to be lower than those laboratory specimens

Core-electron binding energies from self-consistent field molecular orbital theory using a mixture of all-electron real atoms and valence-electron model atoms

International Nuclear Information System (INIS)

Quinn, C.M.; Schwartz, M.E.

1981-01-01

The chemistry of large systems such as clusters may be readily investigated by valence-electron theories based on model potentials, but such an approach does not allow for the examination of core-electron binding energies which are commonly measured experimentally for such systems. Here we merge our previously developed Gaussian based valence-electron model potential theory with all-electron ab initio theory to allow for the calculation of core orbital binding energies when desired. For the atoms whose cores are to be examined, we use the real nuclear changes, all of the electrons, and the appropriate many-electron basis sets. For the rest of the system we use reduced nuclear charges, the Gaussian based model potentials, only the valence electrons, and appropriate valence-electron basis sets. Detailed results for neutral Al 2 are presented for the cases of all-electron, mixed real--model, and model--model SCF--MO calculations. Several different all-electron and valence electron calculations have been done to test the use of the model potential per se, as well as the effect of basis set choice. The results are in all cases in excellent agreement with one another. Based on these studies, a set of ''double-zeta'' valence and all-electron basis functions have been used for further SCF--MO studies on Al 3 , Al 4 , AlNO, and OAl 3 . For a variety of difference combinations of real and model atoms we find excellent agreement for relative total energies, orbital energies (both core and valence), and Mulliken atomic populations. Finally, direct core-hole-state ionic calculations are reported in detail for Al 2 and AlNO, and noted for Al 3 and Al 4 . Results for corresponding frozen-orbital energy differences, relaxed SCF--MO energy differences, and relaxation energies are in all cases in excellent agreement (never differing by more than 0.07 eV, usually by somewhat less). The study clearly demonstrates the accuracy of the mixed real--model theory

Student use of model-based reasoning when troubleshooting an electronic circuit

Science.gov (United States)

Lewandowski, Heather; Stetzer, Mackenzie; van de Bogart, Kevin; Dounas-Frazer, Dimitri

2016-03-01

Troubleshooting systems is an integral part of experimental physics in both research and educational settings. Accordingly, ability to troubleshoot is an important learning goal for undergraduate physics lab courses. We investigate students' model-based reasoning on a troubleshooting task using data collected in think-aloud interviews during which pairs of students from two institutions attempted to diagnose and repair a malfunctioning circuit. Our analysis scheme was informed by the Experimental Modeling Framework, which describes physicists' use of mathematical and conceptual models when reasoning about experimental systems. We show that system and subsystem models were crucial for the evaluation of repairs to the circuit and played an important role in some troubleshooting strategies. Finally, drawing on data from interviews with electronics instructors from a broad range of institution types, we outline recommendations for model-based approaches to teaching and learning troubleshooting skills.

Electron sputtering in the analytical electron microscope: Calculations and experimental data

International Nuclear Information System (INIS)

Zaluzec, N.J.; Mansfield, J.F.

1987-03-01

The environment of the electron microscope is particularly severe when one considers the energy deposited in a specimen during typical experimental conditions. Conventional imaging experiments tend to employ electron current densities ranging from ∼0.1 to 1 A/cm 2 while during microanalysis conditions probe current densities can range from 10 to values as high as 10 5 A/cm 2 . At 100 kV this corresponds to power densities from 100 Kilowatts/cm 2 to 10 4 Megawatts/cm 2 . These energy deposition rates can result in electron irradiation damage which can substantially alter the structure and composition of a specimen through either ionization damage in organics or by displacement damage in inorganics and/or combinations thereof. For the most part materials scientists operating an analytical electron microscope (AEM) in the 100 to 200 kV regime studying metallic and/or ceramic specimens have been spared the need to consider either of these effects as their specimens have tended to be sufficiently resilient. However, the advent of the new medium voltage microscopes operating in the 300 to 400 kV regime with high brightness guns and clean or ultrahigh vacuum systems has necessitated a reevaluation of the effects of higher voltage operation in light of the destructive nature of the electron beam particularly under microanalysis conditions

November 2013 Analysis of High Energy Electrons on the Japan Experimental Module (JEM: Kibo)

Science.gov (United States)

Badavi, Francis F.; Matsumoto, Haruhisa; Koga, Kiyokazu; Mertens, Christopher J.; Slaba, Tony C.; Norbury, John W.

2015-01-01

Albedo (precipitating/splash) electrons, created by galactic cosmic rays (GCR) interaction with the upper atmosphere move upwards away from the surface of the earth. In the past validation work these particles were often considered to have negligible contribution to astronaut radiation exposure on the International Space Station (ISS). Estimates of astronaut exposure based on the available Computer Aided Design (CAD) models of ISS consistently underestimated measurements onboard ISS when the contribution of albedo particles to exposure were neglected. Recent measurements of high energy electrons outside ISS Japan Experimental Module (JEM) using Exposed Facility (EF), Space Environment Data Acquisition Equipment - Attached Payload (SEDA-AP) and Standard DOse Monitor (SDOM), indicates the presence of high energy electrons at ISS altitude. In this presentation the status of these energetic electrons is reviewed and mechanism for the creation of these particles inside/outside South Atlantic Anomaly (SAA) region explained. In addition, limited dosimetric evaluation of these electrons at 600 MeV and 10 GeV is presented.

Hot electron transport modelling in fast ignition relevant targets with non-Spitzer resistivity

Energy Technology Data Exchange (ETDEWEB)

Chapman, D A; Hoarty, D J; Swatton, D J R [Plasma Physics Department, AWE, Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom); Hughes, S J, E-mail: david.chapman@awe.co.u [Computational Physics Group, AWE, Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom)

2010-08-01

The simple Lee-More model for electrical resistivity is implemented in the hybrid fast electron transport code THOR. The model is shown to reproduce experimental data across a wide range of temperatures using a small number of parameters. The effect of this model on the heating of simple Al targets by a short-pulse laser is studied and compared to the predictions of the classical Spitzer-Haerm resistivity. The model is then used in simulations of hot electron transport experiments using buried layer targets.

Modelling low energy electron and positron tracks in biologically relevant media

International Nuclear Information System (INIS)

Blanco, F.; Munoz, A.; Almeida, D.; Ferreira da Silva, F.; Limao-Vieira, P.; Fuss, M.C.; Sanz, A.G.; Garcia, G.

2013-01-01

This colloquium describes an approach to incorporate into radiation damage models the effect of low and intermediate energy (0-100 eV) electrons and positrons, slowing down in biologically relevant materials (water and representative biomolecules). The core of the modelling procedure is a C++ computing programme named 'Low Energy Particle Track Simulation (LEPTS)', which is compatible with available general purpose Monte Carlo packages. Input parameters are carefully selected from theoretical and experimental cross section data and energy loss distribution functions. Data sources used for this purpose are reviewed showing examples of electron and positron cross section and energy loss data for interactions with different media of increasing complexity: atoms, molecules, clusters and condense matter. Finally, we show how such a model can be used to develop an effective dosimetric tool at the molecular level (i.e. nanodosimetry). Recent experimental developments to study the fragmentation induced in biologically material by charge transfer from neutrals and negative ions are also included. (authors)

Model potential for electron scattering from rubidium

Energy Technology Data Exchange (ETDEWEB)

Gien, T.E. (Memorial Univ. of Newfoundland, St. John' s, NF (Canada). Dept. of Physics)

1992-11-28

An analytic model potential for the e[sup -]-Rb[sup +] system is generated from experimental data, using an iteration method. The potential obtained can reproduce rather accurately the energy levels of rubidium. We employed it in the calculation of elastic differential cross sections for electron (and positron) scatterings from rubidium in the conventional Glauber approximation. The differential cross sections calculated in the model potential approach are compared to those in the frozen-core approach, employing either the Clementi-Roetti or the Szasz-McGinn wavefunctions. The core correlation and polarization effects are found to significantly affect the cross section results. (author).

Model potential for electron scattering from rubidium

International Nuclear Information System (INIS)

Gien, T.E.

1992-01-01

An analytic model potential for the e - -Rb + system is generated from experimental data, using an iteration method. The potential obtained can reproduce rather accurately the energy levels of rubidium. We employed it in the calculation of elastic differential cross sections for electron (and positron) scatterings from rubidium in the conventional Glauber approximation. The differential cross sections calculated in the model potential approach are compared to those in the frozen-core approach, employing either the Clementi-Roetti or the Szasz-McGinn wavefunctions. The core correlation and polarization effects are found to significantly affect the cross section results. (author)

Experimental investigation of focusing and transport of heavy-current electron beams

International Nuclear Information System (INIS)

Baranchikov, E.I.; Gordeev, A.V.; Koba, Yu.V.; Korolev, V.D.; Pen'kina, V.S.; Rudakov, L.I.; Smirnov, V.P.; Sukhov, A.D.; Tarumov, E.Z.

The results of an experimental and theoretical study of beam transfer through transverse magnetic fields are outlined. The injection and transport of an annular relativistic electron beam due to a magnetic trap of acute-angle geometry are experimentally studied

Calculated fraction of an incident current pulse that will be accelerated by an electron linear accelerator and comparisons with experimental data

International Nuclear Information System (INIS)

Alsmiller, R.G. Jr.; Alsmiller, F.S.; Lewis, T.A.

1986-05-01

In a series of previous papers, calculated results obtained using a one-dimensional ballistic model were presented to aid in the design of a prebuncher for the Oak Ridge Electron Linear Accelerator. As part of this work, a model was developed to provide limits on the fraction of an incident current pulse that would be accelerated by the existing accelerator. In this paper experimental data on this fraction are presented and the validity of the model developed previously is tested by comparing calculated and experimental data. Part of the experimental data is used to fix the physical parameters in the model and then good agreement between the calculated results and the rest of the experimental data is obtained

Theoretical and experimental study of image formation in scanning transmission electron microscopy

International Nuclear Information System (INIS)

Prunier epouse Mory, Claudie

1985-01-01

This thesis contains a theoretical and experimental study of image formation in a dedicated scanning transmission electron microscope (STEM). Using a detailed description of the different optical elements between the field emission source and the specimen, one calculates the shape and size of the primary probe of electrons impinging on the sample. This modelization enables to estimate the spatial resolution in the different imaging or microanalytical modes. The influence of the specimen and the role of the various detectors are taken into account to calculate the point spread function of the instrument in STEM imaging modes. An experimental study of the characteristic properties of phase contrast bright field micrographs and incoherent dark field ones is performed by comparison of digitally recorded images in similar conditions. Spatial resolution, contrast and signal/noise ratio are assessed by correlation methods, Fourier analysis and statistical considerations; one can deduce the optimum focusing conditions. Limits such as the point resolution on quasi-atomic metallic clusters are determined and an analysis of the capabilities of signal mixing concludes this work. Applications are offered in various domains such as the visualisation of small metallic particles, biomolecules and unstained biological sections. (author) [fr

Experimental study of parametric dependence of electron-scale turbulence in a spherical tokamak

Energy Technology Data Exchange (ETDEWEB)

Ren, Y.; Guttenfelder, W.; Kaye, S. M.; Mazzucato, E.; Bell, R. E.; Diallo, A.; LeBlanc, B. P. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Domier, C. W.; Lee, K. C. [University of California at Davis, Davis, California 95616 (United States); Smith, D. R. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

2012-05-15

Electron-scale turbulence is predicted to drive anomalous electron thermal transport. However, experimental study of its relation with transport is still in its early stage. On the National Spherical Tokamak Experiment (NSTX), electron-scale density fluctuations are studied with a novel tangential microwave scattering system with high radial resolution of {+-}2 cm. Here, we report a study of parametric dependence of electron-scale turbulence in NSTX H-mode plasmas. The dependence on density gradient is studied through the observation of a large density gradient variation in the core induced by an edge localized mode (ELM) event, where we found the first clear experimental evidence of density gradient stabilization of electron-gyro scale turbulence in a fusion plasma. This observation, coupled with linear gyro-kinetic calculations, leads to the identification of the observed instability as toroidal electron temperature gradient (ETG) modes. It is observed that longer wavelength ETG modes, k{sub Up-Tack }{rho}{sub s} Less-Than-Or-Equivalent-To 10 ({rho}{sub s} is the ion gyroradius at electron temperature and k{sub Up-Tack} is the wavenumber perpendicular to local equilibrium magnetic field), are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in electron thermal diffusivity. Comparisons with nonlinear ETG gyrokinetic simulations show ETG turbulence may be able to explain the experimental electron heat flux observed before the ELM event. The collisionality dependence of electron-scale turbulence is also studied by systematically varying plasma current and toroidal field, so that electron gyroradius ({rho}{sub e}), electron beta ({beta}{sub e}), and safety factor (q{sub 95}) are kept approximately constant. More than a factor of two change in electron collisionality, {nu}{sub e}{sup *}, was achieved, and we found that the spectral power of electron-scale turbulence appears to increase as {nu}{sub e}{sup *} is

Experimental study on generation of large area uniform electron beam

International Nuclear Information System (INIS)

Tang Ying; Yi Aiping; Liu Jingru; Qian Hang; Huang Xin; Yu Li; Su Jiancang; Ding Zhenjie; Ding Yongzhong; Yu Jianguo

2007-01-01

In the experiment of gas laser pumped by electron beam, large area uniform electron beam is important to generate high efficiency laser output. The experimental study on generation of large area uniform electron beam with SPG-200 pulsed power generator is introduced. SPG-200 is an all-solid-state components pulsed power generator based on SOS, and its open voltage is more than 350 kV. The cathode have the area of 24 mm x 294 mm, and the anode-cathode(A-C)gap spacing is adjustable from 0 to 49 mm. The electron beam of cathode emission is transported to the laser chamber through the diode pressure foil, which sepa-rates the vacuum chamber from the laser chamber. Velvet and graphite cathodes are studied, each generates large area electron beam. The diode parameters are presented, and the uniformity of e-beam is diagnosed. The experimental results show that the diode voltage of the graphite cathode is 240-280 kV, and the diode current is 0.7-1.8 kA. The diode voltage of the velvet cathode is 200-250 kV, and the diode current is 1.5-1.7 kA. The uniformity of the velvet cathode emission is better than that of the graphite cathode. (authors)

Final Report for 'Modeling Electron Cloud Diagnostics for High-Intensity Proton Accelerators'

International Nuclear Information System (INIS)

Veitzer, Seth A.

2009-01-01

Electron clouds in accelerators such as the ILC degrade beam quality and limit operating efficiency. The need to mitigate electron clouds has a direct impact on the design and operation of these accelerators, translating into increased cost and reduced performance. Diagnostic techniques for measuring electron clouds in accelerating cavities are needed to provide an assessment of electron cloud evolution and mitigation. Accurate numerical modeling of these diagnostics is needed to validate the experimental techniques. In this Phase I, we developed detailed numerical models of microwave propagation through electron clouds in accelerating cavities with geometries relevant to existing and future high-intensity proton accelerators such as Project X and the ILC. Our numerical techniques and simulation results from the Phase I showed that there was a high probability of success in measuring both the evolution of electron clouds and the effects of non-uniform electron density distributions in Phase II.

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

International Nuclear Information System (INIS)

Huh, Sung-Ryul; Kim, Nam-Kyun; Jung, Bong-Ki; Chung, Kyoung-Jae; Hwang, Yong-Seok; Kim, Gon-Ho

2015-01-01

A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the bi-Maxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies

Empirical modeling of high-intensity electron beam interaction with materials

Science.gov (United States)

Koleva, E.; Tsonevska, Ts; Mladenov, G.

2018-03-01

The paper proposes an empirical modeling approach to the prediction followed by optimization of the exact shape of the cross-section of a welded seam, as obtained by electron beam welding. The approach takes into account the electron beam welding process parameters, namely, electron beam power, welding speed, and distances from the magnetic lens of the electron gun to the focus position of the beam and to the surface of the samples treated. The results are verified by comparison with experimental results for type 1H18NT stainless steel samples. The ranges considered of the beam power and the welding speed are 4.2 – 8.4 kW and 3.333 – 13.333 mm/s, respectively.

Experimental program for physics-of-failure modeling of electrolytic capacitors towards prognostics and health management

International Nuclear Information System (INIS)

Rana, Y.S.; Banerjee, Shantanab; Singh, Tej; Varde, P.V.

2017-01-01

Prognostics and Health Management (PHM) is a method used for predicting reliability of a component or system by assessing its current health and future operating conditions. A physics-of-failure (PoF)-based program on PHM for reliability prediction has been initiated at our institute. As part of the program, we aim at developing PoF-based models for degradation of electronic components and their experimental validation. In this direction, a database on existing PoF models for different electronic components has been prepared. We plan to experimentally determine the model constants and propose suitable methodology for PHM. Electrolytic capacitors are one of the most common passive components which find their applications in devices such as power supplies in aircrafts and printed circuit boards (PCBs) for regulation and protection of a nuclear reactor. Experimental studies have established that electrolytic capacitors degrade under electrical and thermal stress and tend to fail before their anticipated useful life at normal operating conditions. Equivalent series resistance (ESR) and capacitance (C) are the two main parameters used for monitoring health of such capacitors. In this paper, we present an experimental program for thermal and electrical overstress studies towards degradation models for electrolytic capacitors. (author)

A multi water bag model of drift kinetic electron plasma

International Nuclear Information System (INIS)

Morel, P.; Dreydemy Ghiro, F.; Berionni, V.; Gurcan, O.D.; Coulette, D.; Besse, N.

2014-01-01

A Multi Water Bag model is proposed for describing drift kinetic plasmas in a magnetized cylindrical geometry, relevant for various experimental devices, solar wind modeling... The Multi Water Bag (MWB) model is adapted to the description of a plasma with kinetic electrons as well as an arbitrary number of kinetic ions. This allows to describe the kinetic dynamics of the electrons, making possible the study of electron temperature gradient (ETG) modes, in addition to the effects of non adiabatic electrons on the ion temperature gradient (ITG) modes, that are of prime importance in the magnetized plasmas micro-turbulence [X. Garbet, Y. Idomura, L. Villard, T.H. Watanabe, Nucl. Fusion 50, 043002 (2010); J.A. Krommes, Ann. Rev. Fluid Mech. 44, 175 (2012)]. The MWB model is shown to link kinetic and fluid descriptions, depending on the number of bags considered. Linear stability of the ETG modes is presented and compared to the existing results regarding cylindrical ITG modes [P. Morel, E. Gravier, N. Besse, R. Klein, A. Ghizzo, P. Bertrand, W. Garbet, Ph. Ghendrih, V. Grandgirard, Y. Sarazin, Phys. Plasmas 14, 112109 (2007)]. (authors)

Model of spur processes in aqueous radiation chemistry including spur overlap and a novel initial hydrated electron distribution

International Nuclear Information System (INIS)

Short, D.R.

1980-01-01

Results are presented from computer calculations based upon an improved diffusion-kinetic model of the spur which includes a novel initial distribution for the hydrated electron and an approximate mathematical treatment of the overlap of spurs in three dimensions. Experimental data for the decay of the hydrated electron and hydroxyl radical before one in electron-pulse-irradated, solute-free and air-free water are fit wihtin experimental uncertainty by adjustment of the initial spatial distributions of spur intermediates and the average energy deposited in the spur. Using the same values of these parameters, the hydrated electron decay is computed for times from 1 ps 10 μs after the radiatio pulse. The results of such calcuations for various conditions of pulse dose and concentrations of scavengers of individual primary chemical species in the spur are compared with corresponding experimental data obtained predominantly from water and aqueous solutions irradiated with 10 to 15 MeV electron pulses. Very good agreement between calculated and experimental hydrated electron decay in pure water is observed for the entire time range studied when a pulse dose of approximately 7900 rads is modeled, but the calcuated and experimental curves are observed to deviate for times greater than 10 ns nanoseconds when low pulse doses and low scavenger concentrations are considered. It is shown that this deviation is experimental and calculated hydrated electron decay cannot be explained by assuming the presence of a hydrated electron scavenging impurity nor by employing a distribution of nearest neighbor interspur distances to refine the overlap approximation

Electron-plasmon model in the electron liquid theory

Directory of Open Access Journals (Sweden)

M.V.Vavrukh

2005-01-01

Full Text Available Here we propose an accurate approach to the description of the electron liquid model in the electron and plasmon terms. Our ideas in the present paper are close to the conception of the collective variables which was developed in the papers of Bohm and Pines. However we use another body of mathematics in the transition to the expanded space of variable particles and plasmons realized by the transition operator. It is evident that in the Random Phase Approximation (RPA, the model which consists of two interactive subsystems of electrons and plasmons is equivalent to the electron liquid model with Coulomb interaction.

Modelling of electron transport and of sawtooth activity in tokamaks

International Nuclear Information System (INIS)

Angioni, C.

2001-10-01

PRETOR. This code has been further extended and applied to the simulation of electron transport in TGV. In simulating the electron temperature profile of Ohmic sawtoothing plasmas, the proper description of the current density profile and the sawtooth activity play the dominant role and not the specific transport model, provided that a single parameter in the model is adjusted to match the global plasma performance. In TGV discharges with electron cyclotron heating (ECH), the behaviour of the electron temperature exhibits some characteristics which have been recently observed to be common to several tokamaks. In particular, with central heating the electron temperature profile is stiff outside the power deposition region, that is the gradient scale length is independent of the heating power and essentially constant along the minor radius. With off-axis heating, transport is strongly reduced in the central region of the plasma, whereas a steep increase of the heat conductivity is observed at the power deposition location. Although the semi-empirical Rebut-Lallia-Watkins (RLW) transport model does not involve a critical gradient scale length, as the experimental observations would suggest, rather a critical electron temperature gradient, we have shown that it allows simulations which reproduce the described experimental features with very good agreement. Due to the relatively low toroidal magnetic field of TCV, the experimental temperature gradient with ECH exceeds by far the threshold included in the model. It can thus be stated that the parametric dependence of the electron heat conductivity of this transport model is adequate to reproduce the electron transport for plasma parameters in the operation domain of TCV. PRETOR, interfaced with the experimental data and the code TORAY-GA for the computation of the ECH source, has hence been used as a reliable tool for transport analysis and planning of new experiments. This has contributed to the identification of an improved

Modelling high-resolution electron microscopy based on core-loss spectroscopy

International Nuclear Information System (INIS)

Allen, L.J.; Findlay, S.D.; Oxley, M.P.; Witte, C.; Zaluzec, N.J.

2006-01-01

There are a number of factors affecting the formation of images based on core-loss spectroscopy in high-resolution electron microscopy. We demonstrate unambiguously the need to use a full nonlocal description of the effective core-loss interaction for experimental results obtained from high angular resolution electron channelling electron spectroscopy. The implications of this model are investigated for atomic resolution scanning transmission electron microscopy. Simulations are used to demonstrate that core-loss spectroscopy images formed using fine probes proposed for future microscopes can result in images that do not correspond visually with the structure that has led to their formation. In this context, we also examine the effect of varying detector geometries. The importance of the contribution to core-loss spectroscopy images by dechannelled or diffusely scattered electrons is reiterated here

Modeling of electron-specimen interaction in scanning electron microscope for e-beam metrology and inspection: challenges and perspectives

Science.gov (United States)

Suzuki, Makoto; Kameda, Toshimasa; Doi, Ayumi; Borisov, Sergey; Babin, Sergey

2018-03-01

The interpretation of scanning electron microscopy (SEM) images of the latest semiconductor devices is not intuitive and requires comparison with computed images based on theoretical modeling and simulations. For quantitative image prediction and geometrical reconstruction of the specimen structure, the accuracy of the physical model is essential. In this paper, we review the current models of electron-solid interaction and discuss their accuracy. We perform the comparison of the simulated results with our experiments of SEM overlay of under-layer, grain imaging of copper interconnect, and hole bottom visualization by angular selective detectors, and show that our model well reproduces the experimental results. Remaining issues for quantitative simulation are also discussed, including the accuracy of the charge dynamics, treatment of beam skirt, and explosive increase in computing time.

Microstructure evolution during homogenization of Al–Mn–Fe–Si alloys: Modeling and experimental results

International Nuclear Information System (INIS)

Du, Q.; Poole, W.J.; Wells, M.A.; Parson, N.C.

2013-01-01

Microstructure evolution during the homogenization heat treatment of Al–Mn–Fe–Si, or AA3xxx, alloys has been investigated using a combination of modeling and experimental studies. The model is fully coupled to CALculation PHAse Diagram (CALPHAD) software and has explicitly taken into account the two different length scales for diffusion encountered in modeling the homogenization process. The model is able to predict the evolution of all the important microstructural features during homogenization, including the inhomogeneous spatial distribution of dispersoids and alloying elements in solution, the dispersoid number density and the size distribution, and the type and fraction of intergranular constituent particles. Experiments were conducted using four direct chill (DC) cast AA3xxx alloys subjected to various homogenization treatments. The resulting microstructures were then characterized using a range of characterization techniques, including optical and electron microscopy, electron micro probe analysis, field emission gun scanning electron microscopy, and electrical resistivity measurements. The model predictions have been compared with the experimental measurements to validate the model. Further, it has been demonstrated that the validated model is able to predict the effects of alloying elements (e.g. Si and Mn) on microstructure evolution. It is concluded that the model provides a time and cost effective tool in optimizing and designing industrial AA3xxx alloy chemistries and homogenization heat treatments

Many-electron model for multiple ionization in atomic collisions

International Nuclear Information System (INIS)

Archubi, C D; Montanari, C C; Miraglia, J E

2007-01-01

We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data

Many-electron model for multiple ionization in atomic collisions

Energy Technology Data Exchange (ETDEWEB)

Archubi, C D [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Montanari, C C [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Miraglia, J E [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina)

2007-03-14

We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.

An experimental and theoretical investigation into the excited electronic states of phenol

Energy Technology Data Exchange (ETDEWEB)

Jones, D. B.; Chiari, L. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Silva, G. B. da [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Universidade Federal de Mato Grosso, Barra do Garças, Mato Grosso (Brazil); Neves, R. F. C. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Departamento de Física, UFJF, Juiz de Fora, MG (Brazil); Instituto Federal do Sul de Minas Gerais, Campus Poços de Caldas, Minas Gerais (Brazil); Duque, H. V. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Departamento de Física, UFJF, Juiz de Fora, MG (Brazil); Oliveira, E. M. de; Lima, M. A. P. [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Lopes, M. C. A. [Departamento de Física, UFJF, Juiz de Fora, MG (Brazil); Costa, R. F. da [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580 Santo André, São Paulo (Brazil); Varella, M. T. do N. [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo (Brazil); Bettega, M. H. F. [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); and others

2014-08-21

We present experimental electron-energy loss spectra (EELS) that were measured at impact energies of 20 and 30 eV and at angles of 90° and 10°, respectively, with energy resolution ∼70 meV. EELS for 250 eV incident electron energy over a range of angles between 3° and 50° have also been measured at a moderate energy resolution (∼0.9 eV). The latter spectra were used to derive differential cross sections and generalised oscillator strengths (GOS) for the dipole-allowed electronic transitions, through normalization to data for elastic electron scattering from benzene. Theoretical calculations were performed using time-dependent density functional theory and single-excitation configuration interaction methods. These calculations were used to assign the experimentally measured spectra. Calculated optical oscillator strengths were also compared to those derived from the GOS data. This provides the first investigation of all singlet and triplet excited electronic states of phenol up to the first ionization potential.

Analytical modeling of electron energy loss spectroscopy of graphene: Ab initio study versus extended hydrodynamic model.

Science.gov (United States)

Djordjević, Tijana; Radović, Ivan; Despoja, Vito; Lyon, Keenan; Borka, Duško; Mišković, Zoran L

2018-01-01

We present an analytical modeling of the electron energy loss (EEL) spectroscopy data for free-standing graphene obtained by scanning transmission electron microscope. The probability density for energy loss of fast electrons traversing graphene under normal incidence is evaluated using an optical approximation based on the conductivity of graphene given in the local, i.e., frequency-dependent form derived by both a two-dimensional, two-fluid extended hydrodynamic (eHD) model and an ab initio method. We compare the results for the real and imaginary parts of the optical conductivity in graphene obtained by these two methods. The calculated probability density is directly compared with the EEL spectra from three independent experiments and we find very good agreement, especially in the case of the eHD model. Furthermore, we point out that the subtraction of the zero-loss peak from the experimental EEL spectra has a strong influence on the analytical model for the EEL spectroscopy data. Copyright © 2017 Elsevier B.V. All rights reserved.

Effective electron-electron and electron-phonon interactions in the Hubbard-Holstein model

International Nuclear Information System (INIS)

Aprea, G.; Di Castro, C.; Grilli, M. . E-mail marco.grilli@roma1.infn.it; Lorenzana, J.

2006-01-01

We investigate the interplay between the electron-electron and the electron-phonon interaction in the Hubbard-Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron-phonon effective coupling and, conversely, the effect of phonons in the effective electron-electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron-electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed

Simulation and experimental studies on electron cloud effects in particle accelerators

CERN Document Server

Romano, Annalisa; Cimino, Roberto; Iadarola, Giovanni; Rumolo, Giovanni

Electron Cloud (EC) effects represent a serious limitation for particle accelerators operating with intense beams of positively charged particles. This Master thesis work presents simulation and experimental studies on EC effects carried out in collaboration with the European Organization for Nuclear Research (CERN) in Geneva and with the INFN-LNF laboratories in Frascati. During the Long Shut- down 1 (LS1, 2013-2014), a new detector for EC measurements has been installed in one of the main magnets of the CERN Proton Synchrotron (PS) to study the EC formation in presence of a strong magnetic field. The aim is to develop a reli- able EC model of the PS vacuum chamber in order to identify possible limitation for the future high intensity and high brightness beams foreseen by Large Hadron Collider (LHC) Injectors Upgrade (LIU) project. Numerical simulations with the new PyECLOUD code were performed in order to quantify the expected signal at the detector under different beam conditions. The experimental activity...

Electron electric dipole moment in mirror fermion model with electroweak scale non-sterile right-handed neutrinos

Directory of Open Access Journals (Sweden)

Chia-Feng Chang

2018-03-01

Full Text Available The electric dipole moment of the electron is studied in detail in an extended mirror fermion model with the following unique features of (a right-handed neutrinos are non-sterile and have masses at the electroweak scale, and (b a horizontal symmetry of the tetrahedral group is used in the lepton and scalar sectors. We study the constraint on the parameter space of the model imposed by the latest ACME experimental limit on electron electric dipole moment. Other low energy experimental observables such as the anomalous magnetic dipole moment of the muon, charged lepton flavor violating processes like muon decays into electron plus photon and muon-to-electron conversion in titanium, gold and lead are also considered in our analysis for comparison. In addition to the well-known CP violating Dirac and Majorana phases in the neutrino mixing matrix, the dependence of additional phases of the new Yukawa couplings in the model is studied in detail for all these low energy observables.

Electron electric dipole moment in mirror fermion model with electroweak scale non-sterile right-handed neutrinos

Science.gov (United States)

Chang, Chia-Feng; Hung, P. Q.; Nugroho, Chrisna Setyo; Tran, Van Que; Yuan, Tzu-Chiang

2018-03-01

The electric dipole moment of the electron is studied in detail in an extended mirror fermion model with the following unique features of (a) right-handed neutrinos are non-sterile and have masses at the electroweak scale, and (b) a horizontal symmetry of the tetrahedral group is used in the lepton and scalar sectors. We study the constraint on the parameter space of the model imposed by the latest ACME experimental limit on electron electric dipole moment. Other low energy experimental observables such as the anomalous magnetic dipole moment of the muon, charged lepton flavor violating processes like muon decays into electron plus photon and muon-to-electron conversion in titanium, gold and lead are also considered in our analysis for comparison. In addition to the well-known CP violating Dirac and Majorana phases in the neutrino mixing matrix, the dependence of additional phases of the new Yukawa couplings in the model is studied in detail for all these low energy observables.

Numerical modelling of negative discharges in air with experimental validation

International Nuclear Information System (INIS)

Tran, T N; Golosnoy, I O; Lewin, P L; Georghiou, G E

2011-01-01

Axisymmetric finite element models have been developed for the simulation of negative discharges in air without and with the presence of dielectrics. The models are based on the hydrodynamic drift-diffusion approximation. A set of continuity equations accounting for the movement, generation and loss of charge carriers (electrons, positive and negative ions) is coupled with Poisson's equation to take into account the effect of space and surface charges on the electric field. The model of a negative corona discharge (without dielectric barriers) in a needle-plane geometry is analysed first. The results obtained show good agreement with experimental observations for various Trichel pulse characteristics. With dielectric barriers introduced into the discharge system, the surface discharge exhibits some similarities and differences to the corona case. The model studies the dynamics of volume charge generation, electric field variations and charge accumulation over the dielectric surface. The predicted surface charge density is consistent with experimental results obtained from the Pockels experiment in terms of distribution form and magnitude.

Experimental study of fast electron transport in dense plasmas

International Nuclear Information System (INIS)

Vaisseau, Xavier

2014-01-01

The framework of this PhD thesis is the inertial confinement fusion for energy production, in the context of the electron fast ignition scheme. The work consists in a characterization of the transport mechanisms of fast electrons, driven by intense laser pulses (10 19 - 10 20 W/cm 2 ) in both cold-solid and warm-dense matter. The first goal was to study the propagation of a fast electron beam, characterized by a current density ≥ 10 11 A/cm 2 , in aluminum targets initially heated close to the Fermi temperature by a counter-propagative planar shock. The planar compression geometry allowed us to discriminate the energy losses due to the resistive mechanisms from collisional ones by comparing solid and compressed targets of the same initial areal densities. We observed for the first time a significant increase of resistive energy losses in heated aluminum samples. The confrontation of the experimental data with the simulations, including a complete characterization of the electron source, of the target compression and of the fast electron transport, allowed us to study the time-evolution of the material resistivity. The estimated resistive electron stopping power in a warm-compressed target is of the same order as the collisional one. We studied the transport of the fast electrons generated in the interaction of a high-contrast laser pulse with a hollow copper cone, buried into a carbon layer, compressed by a counter-propagative planar shock. A X-ray imaging system allowed us to visualize the coupling of the laser pulse with the cone at different moments of the compression. This diagnostic, giving access to the fast electron spatial distribution, showed a fast electron generation in the entire volume of the cone for late times of compression, after shock breakout from the inner cone tip. For earlier times, the interaction at a high-contrast ensured that the source was contained within the cone tip, and the fast electron beam was collimated into the target depth by

The practical model of electron emission in the radioisotope battery by fast ions

International Nuclear Information System (INIS)

Erokhine, N.S.; Balebanov, V.M.

2003-01-01

Under the theoretical analysis of secondary-emission radioisotope source of current the estimate of energy spectrum F(E) of secondary electrons with energy E emitted from films is the important problem. This characteristic knowledge allows, in particular, studying the volt-ampere function, the dependence of electric power deposited in the load on the system parameters and so on. Since the rigorous calculations of energy spectrum F(E) are the complicated enough and labour-intensive there is necessity to elaborate the practical model which allows by the simple computer routine on the basis of generalized data (both experimental measurements and theoretical calculations) on the stopping powers and mean free path of suprathermal electrons to perform reliable express-estimates of the energy spectrum F(E) and the volt-ampere function I(V) for the concrete materials of battery emitter films. This paper devoted to description of of the practical model to calculate electron emission characteristics under the passage of fast ion fluxes from the radioisotope source through the battery emitter. The analytical approximations for the stopping power of emitter materials, the electron inelastic mean free path, the ion production of fast electrons and the probability for them to arrive the film surface are taken into account. In the cases of copper and gold films, the secondary electron escaping depth, the position of energy spectrum peak are considered in the dependence on surface potential barrier magnitude U. According to our calculations the energy spectrum peak shifted to higher electron energy under the U growth. The model described may be used for express estimates and computer simulations of fast alpha-particles and suprathermal electrons interactions with the solid state plasma of battery emitter films, to study the electron emission layer characteristics including the secondary electron escaping depth, to find the optimum conditions for excitation of nonequilibrium

Model-based Adjustment of Droplet Characteristic for 3D Electronic Printing

Directory of Open Access Journals (Sweden)

Lin Na

2017-01-01

Full Text Available The major challenge in 3D electronic printing is the print resolution and accuracy. In this paper, a typical mode - lumped element modeling method (LEM - is adopted to simulate the droplet jetting characteristic. This modeling method can quickly get the droplet velocity and volume with a high accuracy. Experimental results show that LEM has a simpler structure with the sufficient simulation and prediction accuracy.

Some consequences of a scale-breaking model in electron and neutrino deep inelastic scattering

International Nuclear Information System (INIS)

Fernandez Pacheco, A.; Grifols, J.A.; Schmidt, I.A.

1978-01-01

Electron and neutrino deep inelastic processes, extending a simple parton model explanation of the approach to scaling observed in electroproduction at large x are analyzed. The model is successful in fitting the present experimental data without any explicit effects from asymptotic freedom or new quarks. This model has a large q 2 behaviour which is quite different from that expected in asymptotic freedom (AF) theories and comparisons to data can be used to sharpen any experimental demonstration of AF effects. Of course, the model is consistent with AF and both effects could be present

Molecular dynamics simulations with electronic stopping can reproduce experimental sputtering yields of metals impacted by large cluster ions

Science.gov (United States)

Tian, Jiting; Zhou, Wei; Feng, Qijie; Zheng, Jian

2018-03-01

An unsolved problem in research of sputtering from metals induced by energetic large cluster ions is that molecular dynamics (MD) simulations often produce sputtering yields much higher than experimental results. Different from the previous simulations considering only elastic atomic interactions (nuclear stopping), here we incorporate inelastic electrons-atoms interactions (electronic stopping, ES) into MD simulations using a friction model. In this way we have simulated continuous 45° impacts of 10-20 keV C60 on a Ag(111) surface, and found that the calculated sputtering yields can be very close to the experimental results when the model parameter is appropriately assigned. Conversely, when we ignore the effect of ES, the yields are much higher, just like the previous studies. We further expand our research to the sputtering of Au induced by continuous keV C60 or Ar100 bombardments, and obtain quite similar results. Our study indicates that the gap between the experimental and the simulated sputtering yields is probably induced by the ignorance of ES in the simulations, and that a careful treatment of this issue is important for simulations of cluster-ion-induced sputtering, especially for those aiming to compare with experiments.

Isomer depletion as experimental evidence of nuclear excitation by electron capture

Science.gov (United States)

Chiara, C. J.; Carroll, J. J.; Carpenter, M. P.; Greene, J. P.; Hartley, D. J.; Janssens, R. V. F.; Lane, G. J.; Marsh, J. C.; Matters, D. A.; Polasik, M.; Rzadkiewicz, J.; Seweryniak, D.; Zhu, S.; Bottoni, S.; Hayes, A. B.; Karamian, S. A.

2018-02-01

The atomic nucleus and its electrons are often thought of as independent systems that are held together in the atom by their mutual attraction. Their interaction, however, leads to other important effects, such as providing an additional decay mode for excited nuclear states, whereby the nucleus releases energy by ejecting an atomic electron instead of by emitting a γ-ray. This ‘internal conversion’ has been known for about a hundred years and can be used to study nuclei and their interaction with their electrons. In the inverse process—nuclear excitation by electron capture (NEEC)—a free electron is captured into an atomic vacancy and can excite the nucleus to a higher-energy state, provided that the kinetic energy of the free electron plus the magnitude of its binding energy once captured matches the nuclear energy difference between the two states. NEEC was predicted in 1976 and has not hitherto been observed. Here we report evidence of NEEC in molybdenum-93 and determine the probability and cross-section for the process in a beam-based experimental scenario. Our results provide a standard for the assessment of theoretical models relevant to NEEC, which predict cross-sections that span many orders of magnitude. The greatest practical effect of the NEEC process may be on the survival of nuclei in stellar environments, in which it could excite isomers (that is, long-lived nuclear states) to shorter-lived states. Such excitations may reduce the abundance of the isotope after its production. This is an example of ‘isomer depletion’, which has been investigated previously through other reactions, but is used here to obtain evidence for NEEC.

A numerical model of the mirror electron cyclotron resonance MECR source

International Nuclear Information System (INIS)

Hellblom, G.

1986-03-01

Results from numerical modeling of a new type of ion source are presented. The plasma in this source is produced by electron cyclotron resonance in a strong conversion magnetic field. Experiments have shown that a well-defined plasma column, extended along the magnetic field (z-axis) can be produced. The electron temperature and the densities of the various plasma particles have been found to have a strong z-position dependence. With the numerical model, a simulation of the evolution of the composition of the plasma as a function of z is made. A qualitative agreement with experimental data can be obtained for certain parameter regimes. (author)

Modeling nitrogen plasmas produced by intense electron beams

Energy Technology Data Exchange (ETDEWEB)

Angus, J. R.; Swanekamp, S. B.; Schumer, J. W.; Hinshelwood, D. D. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Mosher, D.; Ottinger, P. F. [Independent contractors for NRL through Engility, Inc., Alexandria, Virginia 22314 (United States)

2016-05-15

A new gas–chemistry model is presented to treat the breakdown of a nitrogen gas with pressures on the order of 1 Torr from intense electron beams with current densities on the order of 10 kA/cm{sup 2} and pulse durations on the order of 100 ns. For these parameter regimes, the gas transitions from a weakly ionized molecular state to a strongly ionized atomic state on the time scale of the beam pulse. The model is coupled to a 0D–circuit model using the rigid–beam approximation that can be driven by specifying the time and spatial profiles of the beam pulse. Simulation results are in good agreement with experimental measurements of the line–integrated electron density from experiments done using the Gamble II generator at the Naval Research Laboratory. It is found that the species are mostly in the ground and metastable states during the atomic phase, but that ionization proceeds predominantly through thermal ionization of optically allowed states with excitation energies close to the ionization limit.

WEBEXPIR: Windowless target electron beam experimental irradiation

International Nuclear Information System (INIS)

Dierckx, Marc; Schuurmans, Paul; Heyse, Jan; Rosseel, Kris; Tichelen, Katrien Van; Nactergal, Benoit; Vandeplassche, Dirk; Aoust, Thierry; Abs, Michel; Guertin, Arnaud; Buhour, Jean-Michel; Cadiou, Arnaud; Abderrahim, Hamid Ait

2008-01-01

The windowless target electron beam experimental irradiation (WEBEXPIR) program was set-up as part of the MYRRHA/XT-ADS R and D effort on the spallation target design to investigate the interaction of a proton beam with a liquid lead-bismuth eutectic (LBE) free surface. In particular, possible free surface distortion or shockwave effects in nominal conditions and during sudden beam on/off transient situations, as well as possible enhanced evaporation were assessed. An experiment was conceived at the IBA TT-1000 Rhodotron, where a 7 MeV electron beam was used to simulate the high power deposition at the MYRRHA/XT-ADS LBE free surface. The geometry and the LBE flow characteristics in the WEBEXPIR set-up were made as representative as possible of the actual situation in the MYRRHA/XT-ADS spallation target. Irradiation experiments were carried out at beam currents of up to 10 mA, corresponding to 40 times the nominal beam current necessary to reproduce the MYRRHA/XT-ADS conditions. Preliminary analyses show that the WEBEXPIR free surface flow was not disturbed by the interaction with the electron beam and that vacuum conditions stayed well within the design specifications

Density response to central electron heating: theoretical investigations and experimental observations in ASDEX Upgrade

Science.gov (United States)

Angioni, C.; Peeters, A. G.; Garbet, X.; Manini, A.; Ryter, F.; ASDEX Upgrade Team

2004-08-01

Theory of ion temperature gradient (ITG) and trapped electron modes (TEMs) is applied to the study of particle transport in experimental conditions with central electron heating. It is shown that in the unstable domain of TEMs, the electron thermodiffusive flux is directed outwards. By means of such a flux, a mechanism is identified likely to account for density flattening with central electron heating. Theoretical predictions are compared with experimental observations in ASDEX Upgrade. A parameter domain (including L- and H-mode plasmas) is identified, in which flattening with central electron heating is observed in the experiments. In general, this domain turns out to be the same domain in which the dominant plasma instability is a TEM. On the contrary, the dominant instability is an ITG in plasmas whose density profile is not affected significantly by central electron heating. The flattening predicted by quasi-linear theory for low density L-mode plasmas is too small compared to the experimental observations. At very high density, even when the dominant instability is an ITG, electron heating can provide density flattening, via the coupling with the ion heat channel. In these conditions the anomalous diffusivity increases in response to the increased ion heat flux, while the large collisionality makes the anomalous pinch small and the Ware pinch important.

3D Printing of Plant Golgi Stacks from Their Electron Tomographic Models.

Science.gov (United States)

Mai, Keith Ka Ki; Kang, Madison J; Kang, Byung-Ho

2017-01-01

Three-dimensional (3D) printing is an effective tool for preparing tangible 3D models from computer visualizations to assist in scientific research and education. With the recent popularization of 3D printing processes, it is now possible for individual laboratories to convert their scientific data into a physical form suitable for presentation or teaching purposes. Electron tomography is an electron microscopy method by which 3D structures of subcellular organelles or macromolecular complexes are determined at nanometer-level resolutions. Electron tomography analyses have revealed the convoluted membrane architectures of Golgi stacks, chloroplasts, and mitochondria. But the intricacy of their 3D organizations is difficult to grasp from tomographic models illustrated on computer screens. Despite the rapid development of 3D printing technologies, production of organelle models based on experimental data with 3D printing has rarely been documented. In this chapter, we present a simple guide to creating 3D prints of electron tomographic models of plant Golgi stacks using the two most accessible 3D printing technologies.

Electron density measurement in an evolving plasma. Experimental devices

International Nuclear Information System (INIS)

Consoli, Terenzio; Dagai, Michel

1960-01-01

The experimental devices described here allow the electron density measurements in the 10 16 e/m 3 to 10 20 e/m 3 interval. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 1223-1225, sitting of 15 February 1960 [fr

Analog electronic model of the lobster pyloric central pattern generator

Energy Technology Data Exchange (ETDEWEB)

Volkovskii, A [Institute for Nonlinear Science, University of California San Diego, CA (United States); Brugioni, S [Institute for Nonlinear Science, University of California San Diego, CA (United States); Istituto Nazionale di Ottica Applicata Largo E. Fermi 6 50125 Florence (Italy); Levi, R [Institute for Nonlinear Science, University of California San Diego, CA (United States); Rabinovich, M [Institute for Nonlinear Science, University of California San Diego, CA (United States); Selverston, A [Institute for Nonlinear Science, University of California San Diego, CA (United States); Abarbane, H D I [Institute for Nonlinear Science, University of California San Diego, CA (United States)

2005-01-01

An electronic circuit intended to simulate the nonlinear dynamics of a simplified 3-cell model of the pyloric central pattern generator in California spiny lobster stomato gastric ganglion is presented. The model employs the synaptic phase locked loop (SPLL) concept where the frequency of oscillations of a postsynaptic cell is mainly controlled by the synaptic current which depends on the phase shift between the oscillations. The theoretical study showed that the system has a stable steady state with correct phase shifts between the oscillations and that this regime is stable when the frequency of the pacemaker cell is varied over a wide range. The main bifurcations in the system were studied analytically, in computer simulations, and in experiments with the electronic circuit. The experimental measurements are in good agreement with the expectations of the theoretical model.

Experimental study of fast electron transport in the framework of fast ignition for inertial fusion

International Nuclear Information System (INIS)

Vauzour, B.

2012-01-01

The framework of this PhD thesis is the validation of the fast ignition scheme for the nuclear fusion by inertial confinement. It consists in the experimental study of the various processes involved in fast electron beams propagation, produced by intense laser pulses (10 19 W.cm -2 ), through dense matter either solid or compressed. In this work we present the results of three experiments carried out on different laser facilities in order to generate fast electron beams in various conditions and study their propagation in different states of matter, from the cold solid to the warm and dense plasma.The first experiment was performed with a high intensity contrast on the UHI100 laser facility (CEA Saclay). The study of fast electron energy deposition inside thin aluminium targets highlights a strong target heating at shallow depths, where the collective effects are predominant, thus producing a steep temperature profile between front (300 eV) and rear (20 eV) sides over 20μm thickness. A numerical simulation of the experiment shows that this temperature gradient induces the formation of a shock wave, breaking through the rear side of the target and thus leading to increase the thermal emission. The experimental chronometry of the shock breakthrough allowed validating the model of the collective transport of electrons.Two other experiments were dedicated to the study of fast electron beam propagation inside compressed targets. In the first experiment on the LULI2000 laser facility, the plane compression geometry allowed to precisely dissociate the energy losses due to resistive effects from those due to the collisional ones. By comparing our experimental results with simulations, we observed a significative increase of the fast electron beam energy losses with the compression and the target heating to temperatures close to the Fermi temperature. The second experiment, performed in a cylindrical geometry, demonstrated a fast electron beam guiding phenomenon due to

Electron electric dipole moment in Inverse Seesaw models

Energy Technology Data Exchange (ETDEWEB)

Abada, Asmaa; Toma, Takashi [Laboratoire de Physique Théorique, CNRS, University Paris-Sud, Université Paris-Saclay,91405 Orsay (France)

2016-08-11

We consider the contribution of sterile neutrinos to the electric dipole moment of charged leptons in the most minimal realisation of the Inverse Seesaw mechanism, in which the Standard Model is extended by two right-handed neutrinos and two sterile fermion states. Our study shows that the two pairs of (heavy) pseudo-Dirac mass eigenstates can give significant contributions to the electron electric dipole moment, lying close to future experimental sensitivity if their masses are above the electroweak scale. The major contribution comes from two-loop diagrams with pseudo-Dirac neutrino states running in the loops. In our analysis we further discuss the possibility of having a successful leptogenesis in this framework, compatible with a large electron electric dipole moment.

Electron electric dipole moment in Inverse Seesaw models

International Nuclear Information System (INIS)

Abada, Asmaa; Toma, Takashi

2016-01-01

We consider the contribution of sterile neutrinos to the electric dipole moment of charged leptons in the most minimal realisation of the Inverse Seesaw mechanism, in which the Standard Model is extended by two right-handed neutrinos and two sterile fermion states. Our study shows that the two pairs of (heavy) pseudo-Dirac mass eigenstates can give significant contributions to the electron electric dipole moment, lying close to future experimental sensitivity if their masses are above the electroweak scale. The major contribution comes from two-loop diagrams with pseudo-Dirac neutrino states running in the loops. In our analysis we further discuss the possibility of having a successful leptogenesis in this framework, compatible with a large electron electric dipole moment.

Atomic holography with electrons and x-rays: Theoretical and experimental studies

International Nuclear Information System (INIS)

Len, P.M.

1997-06-01

Gabor first proposed holography in 1948 as a means to experimentally record the amplitude and phase of scattered wavefronts, relative to a direct unscattered wave, and to use such a open-quotes hologramclose quotes to directly image atomic structure. But imaging at atomic resolution has not yet been possible in the way he proposed. Much more recently, Szoeke in 1986 noted that photoexcited atoms can emit photoelectron of fluorescent x-ray wavefronts that are scattered by neighboring atoms, thus yielding the direct and scattered wavefronts as detected in the far field that can then be interpreted as holographic in nature. By now, several algorithms for directly reconstructing three-dimensional atomic images from electron holograms have been proposed (e.g. by Barton) and successfully tested against experiment and theory. Very recently, Tegze and Faigel, and Grog et al. have recorded experimental x-ray fluorescence holograms, and these are found to yield atomic images that are more free of the kinds of aberrations caused by the non-ideal emission or scattering of electrons. The basic principles of these holographic atomic imaging methods are reviewed, including illustrative applications of the reconstruction algorithms to both theoretical and experimental electron and x-ray holograms. The author also discusses the prospects and limitations of these newly emerging atomic structural probes

Experimental study and modelling of X-ray photo-triggering of a discharge for exciplex laser

International Nuclear Information System (INIS)

Louvet, Yolande

1986-01-01

As the excitation of the laser medium by using a photo-triggered discharge revealed to be more reliable that an excitation by pre-ionised discharge, this research thesis reports the use of such an excitation and the study of initiation mechanisms for discharges photo-triggered by X rays. The author first recalls the main characteristics of excimer and exciplex systems, and presents the principle of discharge photo-triggering. He presents the experimental set-up, and reports the use of an original method to characterise the X radiation. This method uses theoretical data related to Bremsstrahlung emission, and results are validated by experimental tests. Realistic data regarding X ray properties are introduced into the theoretical model which also takes X-ray-induced ionisation reactions and photo-electron energetic degradation into account. By using this model, the author determines the electron distribution function produced by the X pre-ionisation, and the resulting thermalized electron density [fr

Improved age-diffusion model for low-energy electron transport in solids. II. Application to secondary emission from aluminum

International Nuclear Information System (INIS)

Dubus, A.; Devooght, J.; Dehaes, J.C.

1987-01-01

The ''improved age-diffusion'' model for secondary-electron transport is applied to aluminum. Electron cross sections for inelastic collisions with the free-electron gas using the Lindhard dielectric function and for elastic collisions with the randomly distributed ionic cores are used in the calculations. The most important characteristics of backward secondary-electron emission induced by low-energy electrons on polycrystalline Al targets are calculated and compared to experimental results and to Monte Carlo calculations. The model appears to predict the electronic yield, the energy spectra, and the spatial dependence of secondary emission with reasonable accuracy

FIRST EXPERIMENTAL RESULTS FROM DEGAS, THE QUANTUM LIMITED BRIGHTNESS ELECTRON SOURCE

International Nuclear Information System (INIS)

Zolotorev, Max S.; Commins, Eugene D.; Oneill, James; Sannibale, Fernando; Tremsin, Anton; Wan, Weishi

2008-01-01

The construction of DEGAS (DEGenerate Advanced Source), a proof of principle for a quantum limited brightness electron source, has been completed at the Lawrence Berkeley National Laboratory. The commissioning and the characterization of this source, designed to generate coherent single electron 'bunches' with brightness approaching the quantum limit at a repetition rate of few MHz, has been started. In this paper the first experimental results are described

Unified model of secondary electron cascades in diamond

International Nuclear Information System (INIS)

Ziaja, Beata; London, Richard A.; Hajdu, Janos

2005-01-01

In this article we present a detailed and unified theoretical treatment of secondary electron cascades that follow the absorption of x-ray photons. A Monte Carlo model has been constructed that treats in detail the evolution of electron cascades induced by photoelectrons and by Auger electrons following inner shell ionizations. Detailed calculations are presented for cascades initiated by electron energies between 0.1 and 10 keV. The present article expands our earlier work [B. Ziaja, D. van der Spoel, A. Szoeke, and J. Hajdu, Phys. Rev. B 64, 214104 (2001), Phys. Rev. B 66, 024116 (2002)] by extending the primary energy range, by improving the treatment of secondary electrons, especially at low electron energies, by including ionization by holes, and by taking into account their coupling to the crystal lattice. The calculations describe the three-dimensional evolution of the electron cloud, and monitor the equivalent instantaneous temperature of the free electron gas as the system cools. The dissipation of the impact energy proceeds predominantly through the production of secondary electrons whose energies are comparable to the binding energies of the valence (40-50 eV) and of the core electrons (300 eV). The electron cloud generated by a 10 keV electron is strongly anisotropic in the early phases of the cascade (t≤1 fs). At later times, the sample is dominated by low energy electrons, and these are scattered more isotropically by atoms in the sample. Our results for the total number of secondary electrons agree with available experimental data, and show that the emission of secondary electrons approaches saturation within about 100 fs following the primary impact

Experimental and theoretical study of the electron cascade induced in a gas by laser light

International Nuclear Information System (INIS)

Louis-Jacquet, Michel.

1978-10-01

In a laser gas interaction experiment, first electrons created by multiphoton ionization of atoms gain sufficient energy in the laser E.M. wave to promote collisional ionization of other atoms. An experimental and theoretical study of the electron-neutral atom inverse bremsstrahlung process and the consecutive electron cascade is presented. The main basic idea is to create an initial electron population and to study its evolution versus the photon density. A Boltzman equation including several collision terms can describe such a plasma. The resolution by a general eigen values method shows that the electron density growth rate is inversely proportionnal to both neutral atom density and laser light illumination. Experimental conditions were defined in order to insure negligible secondary mechanisms (multiphoton ionization, diffusion, recombination, ...). Using a macroscopic description of the interaction, the growth rate can be deduced from the experimental results. Values are in a rather good agreement with the theoretical ones. Moreover evidence is given of influence of the excited atoms on the multiplication process [fr

First experimental results of the BNL inverse free electron laser accelerator

International Nuclear Information System (INIS)

Steenbergen, A. van; Gallardo, J.; Babzien, M.; Skaritka, J.; Wang, X.J.; Sandweiss, J.; Fang, J.M.; Qiu, X.

1996-10-01

A 40 MeV electron beam, using the inverse3e free-electron laser interaction, has been accelerated by ΔE/E = 2.5% over a distance of 0.47 m. The electrons interact with a 1--2 GW CO 2 laser beam bounded by a 2.8 mm ID sapphire circular waveguide in the presence of a tapered wiggler with Bmax ∼ 1 T and a period 2.89 cm ≤ λ w ≤ 3.14 cm. The experimental results of ΔE/E as a function of electron energy E, peak magnetic field Bw and laser power W 1 compare well with analytical and 1-D numerical simulations and permit scaling to higher laser power and electron energy

Automation of electron channeling investigations into crystals on the experimental stand

International Nuclear Information System (INIS)

Kolodin, L.G.; Kupchishin, A.A.; Bunegin, V.V.

1995-01-01

Automated control system of technological processes of the experimental stand is proposed for electron channeling investigation into crystals. The system is proposed for stand control automation and registration of corresponding radiations. There are four main parts in stand complex: Ehlu-6 type electron accelerator; forming and transporting system of electron beams; goniometer system; radiation detection system. Purposes of the automated system creation are following: - improvement of EhLU accelerator operating stability by of automation stabilization of its parameters; - quality improvement of electron beam monochromatization by of automation of monochromator electromagnet control; - simplification of crystal adjustment process relatively of primary electron beam and crystal transporting to the position by of goniometer automation control; - providing of automating collection and processing of data of physical experiments

Cluster dynamics modeling and experimental investigation of the effect of injected interstitials

Science.gov (United States)

Michaut, B.; Jourdan, T.; Malaplate, J.; Renault-Laborne, A.; Sefta, F.; Décamps, B.

2017-12-01

The effect of injected interstitials on loop and cavity microstructures is investigated experimentally and numerically for 304L austenitic stainless steel irradiated at 450 °C with 10 MeV Fe5+ ions up to about 100 dpa. A cluster dynamics model is parametrized on experimental results obtained by transmission electron microscopy (TEM) in a region where injected interstitials can be safely neglected. It is then used to model the damage profile and study the impact of self-ion injection. Results are compared to TEM observations on cross-sections of specimens. It is shown that injected interstitials have a significant effect on cavity density and mean size, even in the sink-dominated regime. To quantitatively match the experimental data in the self-ions injected area, a variation of some parameters is necessary. We propose that the fraction of freely migrating species may vary as a function of depth. Finally, we show that simple rate theory considerations do not seem to be valid for these experimental conditions.

Fabrication, characterization, and modeling of a biodegradable battery for transient electronics

Science.gov (United States)

Edupuganti, Vineet; Solanki, Raj

2016-12-01

Traditionally, emphasis has been placed on durable, long-lasting electronics. However, electronics that are meant to intentionally degrade over time can actually have significant practical applications. Biodegradable, or transient, electronics would open up opportunities in the field of medical implants, where the need for surgical removal of devices could be eliminated. Environmental sensors and, eventually, consumer electronics would also greatly benefit from this technology. An essential component of transient electronics is the battery, which serves as a biodegradable power source. This work involves the fabrication, characterization, and modeling of a magnesium-based biodegradable battery. Galvanostatic discharge tests show that an anode material of magnesium alloy AZ31 extends battery lifetime by over six times, as compared to pure magnesium. With AZ31, the maximum power and capacity of the fabricated device are 67 μW and 5.2 mAh, respectively, though the anode area is just 0.8 cm2. The development of an equivalent circuit model provided insight into the battery's behavior by extracting fitting parameters from experimental data. The model can accurately simulate device behavior, taking into account its intentional degradation. The size of the device and the power it produces are in accordance with typical levels for low-power transient systems.

Theoretical and experimental studies of runaway electrons in the TEXTOR tokamak

International Nuclear Information System (INIS)

Abdullaev, S.S.; Finken, K.H.; Wongrach, K.; Willi, O.

2016-01-01

Theoretical and experimental studies of runaway electrons in tokamaks and their mitigations, particularly the recent studies performed by a group of the Heinrich-Heine University Duesseldorf in collaboration with the Institute of Energy and Climate Research of the Research Centre (Forschungszentrum) of Juelich are reviewed. The main topics focus on (i) runaway generation mechanisms, (ii) runaway orbits in equilibrium plasma, (iii) transport in stochastic magnetic fields, (iv) diagnostics and investigations of transport of runaway electron and their losses in low density discharges (v) runaway electrons during plasma disruptions, and (vi) runaway mitigation methods. The development of runaway diagnostics enables the measurement of runaway electrons in both the centre and edge of the plasma. The diagnostics provide an absolute runaway energy resolved measurement, the radial decay length of runaway electrons and, the structure and dynamics of runaway electron beams. The new mechanism of runaway electron formation during plasma disruptions is discussed.

Theoretical and experimental studies of runaway electrons in the TEXTOR tokamak

Energy Technology Data Exchange (ETDEWEB)

Abdullaev, S.S.; Finken, K.H.; Wongrach, K.; Willi, O.

2016-07-01

Theoretical and experimental studies of runaway electrons in tokamaks and their mitigations, particularly the recent studies performed by a group of the Heinrich-Heine University Duesseldorf in collaboration with the Institute of Energy and Climate Research of the Research Centre (Forschungszentrum) of Juelich are reviewed. The main topics focus on (i) runaway generation mechanisms, (ii) runaway orbits in equilibrium plasma, (iii) transport in stochastic magnetic fields, (iv) diagnostics and investigations of transport of runaway electron and their losses in low density discharges (v) runaway electrons during plasma disruptions, and (vi) runaway mitigation methods. The development of runaway diagnostics enables the measurement of runaway electrons in both the centre and edge of the plasma. The diagnostics provide an absolute runaway energy resolved measurement, the radial decay length of runaway electrons and, the structure and dynamics of runaway electron beams. The new mechanism of runaway electron formation during plasma disruptions is discussed.

Determination of equilibrium electron temperature and times using an electron swarm model with BOLSIG+ calculated collision frequencies and rate coefficients

International Nuclear Information System (INIS)

Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei

2015-01-01

Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Important swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. We show that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections

Geometrical model for the electron

International Nuclear Information System (INIS)

El-Sherbini, T.M.

1985-07-01

A model for an electron of finite dimensions is proposed. This model disregards the concept of electronic charge and leads to Bohr's frequency formula for the hydrogen atom and to Maxwell's equations for electromagnetic fields. The stability of a free electron under the action of centrifugal and transverse forces is discussed. (author)

Experimental study of intensive electron beam scattering in melting channel

International Nuclear Information System (INIS)

Balagura, V.S.; Kurilko, V.I.; Safronov, B.G.

1988-01-01

Multiple scattering of an intensive electron beam at 28 keV energy passing through a melting channel in iron targets is experimentally studied. The dependence of scattering on the melting current value is established. The material density in the channel on the basis of the binary collision method is evaluated. It is shown that these density values are of three orders less than the estimations made on the basis of the data on energy losses of electrons in the channel. 6 refs.; 4 figs

Application of a distorted wave model to electron capture in atomic collisions

International Nuclear Information System (INIS)

Deco, G.R.; Martinez, A.E.; Rivarola, R.D.

1988-01-01

In this work, it is presented the CDW-EIS approximation applied to the description of processes of electron capture in ion-atom collisions. Differential and total cross sections are compared to results obtained by other theoretical models, as well as, to experimental data. (A.C.A.S.) [pt

Experimental investigation and thermodynamic modeling of the Ga–Zr system

Energy Technology Data Exchange (ETDEWEB)

Luo, Wei [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Liu, Shuhong, E-mail: shhliu@csu.edu.cn [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Tang, Ying [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Yin, Ming [Thermal Processing Technology Center, Illinois Institute of Technology (IIT), 10 West 32nd Street, Chicago, IL 60616 (United States); Sundman, Bosse [INSTN, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France); Du, Yong [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Nash, Philip [Thermal Processing Technology Center, Illinois Institute of Technology (IIT), 10 West 32nd Street, Chicago, IL 60616 (United States); Tao, Huijin [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China)

2014-02-25

Highlights: • Phase equilibria of the Ga–Zr system were investigated by experiment. • Δ{sub f}Hs for intermetallic compounds were computed via first–principles calculations. • The enthalpy of formation at 298 K for αGaZr was measured by calorimetry. • A set of self-consistent thermodynamic parameters was obtained. -- Abstract: Phase equilibria of the Ga–Zr system were investigated by experiment and thermodynamic modeling. In the experimental part, eleven alloys were prepared by melting the pure elements and annealed. Both the as-cast and annealed samples were analyzed by X-ray diffraction, optical microscopy, and scanning electron microscope. The annealed alloys were investigated by differential thermal analysis and electron probe microanalysis. In order to assist the thermodynamic modeling, the enthalpies of formation at 0 K for the GaZr{sub 2}, Ga{sub 3}Zr{sub 5}, Ga{sub 2}Zr{sub 3}, Ga{sub 4}Zr{sub 5}, αGaZr, Ga{sub 3}Zr{sub 2}, Ga{sub 5}Zr{sub 3}, Ga{sub 2}Zr and Ga{sub 3}Zr phases were computed via first-principles calculations. The enthalpy of formation at 298 K for the αGaZr was measured by high temperature reaction calorimetry. Based on the experimental phase diagram data from the present work and the literature as well as the present first-principles calculations, the Ga–Zr system was critically assessed by means of CALPHAD approach. The calculated phase diagram and thermodynamic properties agree well with the available experimental data.

Electron collisions in the trapped gyro-Landau fluid transport model

International Nuclear Information System (INIS)

Staebler, G. M.; Kinsey, J. E.

2010-01-01

Accurately modeling electron collisions in the trapped gyro-Landau fluid (TGLF) equations has been a major challenge. Insights gained from numerically solving the gyrokinetic equation have lead to a significant improvement of the low order TGLF model. The theoretical motivation and verification of this model with the velocity-space gyrokinetic code GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] will be presented. The improvement in the fidelity of TGLF to GYRO is shown to also lead to better prediction of experimental temperature profiles by TGLF for a dedicated collision frequency scan.

Energy deposition model for low-energy electrons (10-10 000 eV) in air

International Nuclear Information System (INIS)

Roldan, A.; Perez, J.M.; Williart, A.; Blanco, F.; Garcia, G.

2004-01-01

An energy deposition model for electrons in air that can be useful in microdosimetric applications is presented in this study. The model is based on a Monte Carlo simulation of the single electron scattering processes that can take place with the molecular constituents of the air in the energy range 10-10 000 eV. The input parameters for this procedure have been the electron scattering cross sections, both differential and integral. These parameters were calculated using a model potential method which describes the electron scattering with the molecular constituent of air. The reliability of the calculated integral cross section values has been evaluated by comparison with direct total electron scattering cross-section measurements performed by us in a transmission beam experiment. Experimental energy loss spectra for electrons in air have been used as probability distribution functions to define the electron energy loss in single collision events. The resulting model has been applied to simulate the electron transport through a gas cell containing air at different pressures and the results have been compared with those observed in the experiments. Finally, as an example of its applicability to dosimetric issues, the energy deposition of 10 000 eV by means of successive collisions in a free air chamber has been simulated

Experimental research of double-pulse linear induction electron accelerator

International Nuclear Information System (INIS)

Liao Shuqing; Cheng Cheng; Zheng Shuxin; Tang Chuanxiang; Lin Yuzheng; Jing Xiaobing; Mu Fan; Pan Haifeng

2009-01-01

The Mini-LIA is a double-pulse linear induction electron accelerator with megahertz repetition rates, which consists of a double-pulse power system, a thermal cathode electron gun, two induction cells, beam transportation systems and diagnosis systems, etc. Experiments of the Mini-LIA have been conducted. The double-pulse high voltage was obtained with several hundred nanosecond pulse intervals (i. e. megahertz repetition rate) and each pulse had an 80 kV amplitude with a FWHM of 80 ns. In the gap of the induction cell, the double-pulse accelerating electric field was measured via E-field probes, and the double-pulse electron beam with a current about 1.1 A has been obtained at the Mini-LIA exit. These experimental results show that the double-pulse high voltage with megahertz repetition rates can be generated by an insulation and junction system. And they also indicate that the induction cell with metglas as the ferromagnetic material and the LaB 6 thermal cathode electron gun suit the double-pulse operation with megahertz repetition rates. (authors)

Topside electron density: comparison of experimental and IRI model profiles during low solar activity period

International Nuclear Information System (INIS)

Alazo, K.; Coisson, P.; Radicella, S.M.

2003-01-01

The pattern of the topside electron density profiles is not yet very well represented by the IRI model. In this work the topside profiles obtained by the ISIS-2 satellite during low solar activity conditions are compared to those modeled by IRI. We take the quantitative parameter ε to measure the deviation of the model from the observed profiles. The results showed that the IRI overestimation of the topside profile is higher for low dip latitudes. The dispersion of the epsilon values is from 40 to 140%, more in equinoctial months and some lower for Winter. The best modeling is about 20% to 40% in middle and high latitudes of the North Hemisphere. (author)

Experimental study of the electron-atom Bremsstrahlung emission in an argon plasma jet

International Nuclear Information System (INIS)

Ranson, P.; Vallee, O.; Chapelle, J.

1977-01-01

Electron-neutral atom bremsstrahlung is studied between 0.4 μm and 5 μm in a decaying argon plasma jet; in visible and infra-red range, some discrepancies appear between experimental results and theoretical calculations of different authors (Geltman, Stallcop). In the infra-red, the discrepancy can be partly explained because theoretical elastic cross sections are higher than experimental values in the vicinity of the Ramsauer minimum. In the visible range, a very small amount of fast electrons due to superelastic and recombination collisions explain the observed discrepancy [fr

Modelling of electronic and vibrational properties of carbon nanostructures

Science.gov (United States)

Margine, Elena Roxana

The main goals of this dissertation work are the analysis and prediction of the properties of nanoscale carbon materials which hold great potential for nanotechnological applications such as strong conductive composites, field-effect transistors, diodes, rechargeable batteries, etc. Some of these exciting applications are already being actively developed, however their design via trial-and-error experimentation is often difficult and expensive. State-of-the-art simulation methods can be used as a powerful tool to streamline the path to practical implementations. In this thesis I use ab initio quantum-mechanical calculations to explore the response of nanoscale carbon materials to doping. A brief overview of the theoretical methods and of some basic concepts on carbon nanotubes are given in the first two chapters. In Chapter 3 we study the effect of doping in double-walled carbon nanotubes. These systems can be considered as nanoscale capacitors since they have two conducting (or semi-conducting) shells. The experimental work of our collaborators demonstrated for the first time that such a capacitor can be realized by the adsorption of bromine anions at the surface of the outer tube. Our theoretical analysis of the experimental results revealed that this quantum system, surprisingly, behaves exactly as the classical Faraday cage: the electric charge always resides on the outside surface of the conductor, even when the pristine tubes are not metallic. In Chapter 4 I present our findings on the phonon frequencies' response to electron doping in single-walled carbon nanotubes. It is well established that when graphite is doped with electrons, carbon-carbon bonds lengthen and all vibrational frequencies soften. However, in semiconducting carbon nanotubes, the frequency of one mode increases at low levels of alkali doping. Having carefully modelled the process with ab initio methods we conclude that the unusual behavior of the vibrational mode depends on which electronic

High-temperature experimental and thermodynamic modelling research on the pyrometallurgical processing of copper

Science.gov (United States)

Hidayat, Taufiq; Shishin, Denis; Decterov, Sergei A.; Hayes, Peter C.; Jak, Evgueni

2017-01-01

Uncertainty in the metal price and competition between producers mean that the daily operation of a smelter needs to target high recovery of valuable elements at low operating cost. Options for the improvement of the plant operation can be examined and decision making can be informed based on accurate information from laboratory experimentation coupled with predictions using advanced thermodynamic models. Integrated high-temperature experimental and thermodynamic modelling research on phase equilibria and thermodynamics of copper-containing systems have been undertaken at the Pyrometallurgy Innovation Centre (PYROSEARCH). The experimental phase equilibria studies involve high-temperature equilibration, rapid quenching and direct measurement of phase compositions using electron probe X-ray microanalysis (EPMA). The thermodynamic modelling deals with the development of accurate thermodynamic database built through critical evaluation of experimental data, selection of solution models, and optimization of models parameters. The database covers the Al-Ca-Cu-Fe-Mg-O-S-Si chemical system. The gas, slag, matte, liquid and solid metal phases, spinel solid solution as well as numerous solid oxide and sulphide phases are included. The database works within the FactSage software environment. Examples of phase equilibria data and thermodynamic models of selected systems, as well as possible implementation of the research outcomes to selected copper making processes are presented.

MATLAB/Simulink Pulse-Echo Ultrasound System Simulator Based on Experimentally Validated Models.

Science.gov (United States)

Kim, Taehoon; Shin, Sangmin; Lee, Hyongmin; Lee, Hyunsook; Kim, Heewon; Shin, Eunhee; Kim, Suhwan

2016-02-01

A flexible clinical ultrasound system must operate with different transducers, which have characteristic impulse responses and widely varying impedances. The impulse response determines the shape of the high-voltage pulse that is transmitted and the specifications of the front-end electronics that receive the echo; the impedance determines the specification of the matching network through which the transducer is connected. System-level optimization of these subsystems requires accurate modeling of pulse-echo (two-way) response, which in turn demands a unified simulation of the ultrasonics and electronics. In this paper, this is realized by combining MATLAB/Simulink models of the high-voltage transmitter, the transmission interface, the acoustic subsystem which includes wave propagation and reflection, the receiving interface, and the front-end receiver. To demonstrate the effectiveness of our simulator, the models are experimentally validated by comparing the simulation results with the measured data from a commercial ultrasound system. This simulator could be used to quickly provide system-level feedback for an optimized tuning of electronic design parameters.

Semantic modeling and structural synthesis of onboard electronics protection means as open information system

Science.gov (United States)

Zhevnerchuk, D. V.; Surkova, A. S.; Lomakina, L. S.; Golubev, A. S.

2018-05-01

The article describes the component representation approach and semantic models of on-board electronics protection from ionizing radiation of various nature. Semantic models are constructed, the feature of which is the representation of electronic elements, protection modules, sources of impact in the form of blocks with interfaces. The rules of logical inference and algorithms for synthesizing the object properties of the semantic network, imitating the interface between the components of the protection system and the sources of radiation, are developed. The results of the algorithm are considered using the example of radiation-resistant microcircuits 1645RU5U, 1645RT2U and the calculation and experimental method for estimating the durability of on-board electronics.

Distorted wave models applied to electron emission study in ion-atom collisions at intermediate and high energies

International Nuclear Information System (INIS)

Fainstein, P.D.

1989-01-01

The electron emission from different atoms induced by impact of multicharged bare ions at intermediate and high energies is studied. To perform these studies, the continuum distorted wave-eikonal initial state model is used. With this distorted wave model, analytical expressions are obtained for the transition amplitudes as a function of the transverse momentum transfer for hydrogen targets in an arbitrary initial state and for every any orbital of a multielectronic target represented as a linear combination of Slater type orbitals. With these expressions, the different cross sections which are compared with the experimental data available are numerically calculated. The results obtained for different targets and projectiles and the comparison with other theoretical models and experimental data allows to explain the electron emission spectra and to predict new effects which have not been measured so far. The results of the present work permit to view the ionization process as the evolution of the active electron in the combined field of the target and projectile nuclei. (Author) [es

Experimental and theoretical study of electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy

International Nuclear Information System (INIS)

Festa, Floriane

2013-01-01

Matter in extreme conditions belongs to Warm Dense Matter regime which lays between dense plasma regime and condensed matter. This regime is still not well known, indeed it is very complex to generate such plasma in the laboratory to get experimental data and validate models. The goal of this thesis is to study electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy. Experimentally aluminum has reached high densities and high temperatures, up to now unexplored. An X-ray source has also been generated to probe highly compressed aluminum. Two spectrometers have recorded aluminum absorption spectra and aluminum density and temperature conditions have been deduced thanks to optical diagnostics. Experimental spectra have been compared to ab initio spectra, calculated in the same conditions. The theoretical goal was to validate the calculation method in high densities and high temperatures regime with the study of K-edge absorption modifications. We also used absorption spectra to study the metal-non metal transition which takes place at low density (density ≤ solid density). This transition could be study with electronic structure modifications of the system. (author) [fr

Theoretical modeling of electron mobility in superfluid {sup 4}He

Energy Technology Data Exchange (ETDEWEB)

Aitken, Frédéric; Bonifaci, Nelly [G2ELab-GreEn-ER, Equipe MDE, 21 Avenue des Martyrs, CS 90624, 38031 Grenoble Cedex 1 (France); Haeften, Klaus von [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Eloranta, Jussi, E-mail: Jussi.Eloranta@csun.edu [Department of Chemistry and Biochemistry, California State University at Northridge, 18111 Nordhoff St., Northridge, California 91330 (United States)

2016-07-28

The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid {sup 4}He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed “exotic ion” data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ions are briefly discussed.

Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural

Science.gov (United States)

Jones, D. B.; Neves, R. F. C.; Lopes, M. C. A.; da Costa, R. F.; do N. Varella, M. T.; Bettega, M. H. F.; Lima, M. A. P.; García, G.; Limão-Vieira, P.; Brunger, M. J.

2016-03-01

We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (C5H4O2). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C5H4O2. The measurements were carried out at energies in the range 20-40 eV, and for scattered-electron angles between 10° and 90°. The energy resolution of those experiments was typically ˜80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6-50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail.

Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural

International Nuclear Information System (INIS)

Jones, D. B.; Neves, R. F. C.; Lopes, M. C. A.; Costa, R. F. da; Varella, M. T. do N; Bettega, M. H. F.; Lima, M. A. P.; García, G.

2016-01-01

We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (C 5 H 4 O 2 ). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C 5 H 4 O 2 . The measurements were carried out at energies in the range 20–40 eV, and for scattered-electron angles between 10° and 90°. The energy resolution of those experiments was typically ∼80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6–50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail.

A model for negative ion extraction and comparison of negative ion optics calculations to experimental results

International Nuclear Information System (INIS)

Pamela, J.

1990-10-01

Negative ion extraction is described by a model which includes electron diffusion across transverse magnetic fields in the sheath. This model allows a 2-Dimensional approximation of the problem. It is used to introduce electron space charge effects in a 2-D particle trajectory code, designed for negative ion optics calculations. Another physical effect, the stripping of negative ions on neutral gas atoms, has also been included in our model; it is found to play an important role in negative ion optics. The comparison with three sets of experimental data from very different negative ion accelerators, show that our model is able of accurate predictions

Experimental models of demyelination and remyelination.

Science.gov (United States)

Torre-Fuentes, L; Moreno-Jiménez, L; Pytel, V; Matías-Guiu, J A; Gómez-Pinedo, U; Matías-Guiu, J

2017-08-29

Experimental animal models constitute a useful tool to deepen our knowledge of central nervous system disorders. In the case of multiple sclerosis, however, there is no such specific model able to provide an overview of the disease; multiple models covering the different pathophysiological features of the disease are therefore necessary. We reviewed the different in vitro and in vivo experimental models used in multiple sclerosis research. Concerning in vitro models, we analysed cell cultures and slice models. As for in vivo models, we examined such models of autoimmunity and inflammation as experimental allergic encephalitis in different animals and virus-induced demyelinating diseases. Furthermore, we analysed models of demyelination and remyelination, including chemical lesions caused by cuprizone, lysolecithin, and ethidium bromide; zebrafish; and transgenic models. Experimental models provide a deeper understanding of the different pathogenic mechanisms involved in multiple sclerosis. Choosing one model or another depends on the specific aims of the study. Copyright © 2017 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

Electron distortion effects in quasi-eleastic electron scattering

International Nuclear Information System (INIS)

Jin, Yanhe.

1991-03-01

This report discusses the following topics: dirac single particle shell model; dirac free states in Coulomb and optical potentials; deep inelastic electron scattering; plane wave born approximation and Rosenbluth separation; analysis of the 40 Ca(e,e') experimental data; and analysis of the exclusive (e,e'p) experimental data

CDW-EIS model for single-electron capture in ion-atom collisions involving multielectronic targets

International Nuclear Information System (INIS)

Abufager, P N; MartInez, A E; Rivarola, R D; Fainstein, P D

2004-01-01

A generalization of the continuum distorted wave eikonal initial state (CDW-EIS) approximation, for the description of single-electron capture in ion-atom collisions involving multielectronic targets is presented. This approximation is developed within the framework of the independent electron model taking particular care of the representation of the bound and continuum target states. Total cross sections for single-electron capture from the K-shell of He, Ne and Ar noble gases by impact of bare ions are calculated. Present results are compared to previous CDW-EIS ones and to experimental data

Experimental studies of stable confined electron clouds using Gabor lenses

CERN Document Server

Meusel, O.; Glaeser, B.; Schulte, K.

2013-04-22

Based on the idea of D. Gabor [1] space charge lenses are under investigation to be a powerful focussing device for intense ion beams. A stable confined electron column is used to provide strong radially symmetric electrostatic focussing, e.g. for positively charged ion beams. The advantages of Gabor lenses are a mass independent focussing strength, space charge compensation of the ion beam and reduced magnetic or electric fields compared to conventional focussing devices. Collective phenomena of the electron cloud result in aberrations and emittance growth of the ion beam. The knowledge of the behaviour of the electron cloud prevents a decrease of the beam brilliance. Numerical models developed to describe the electron confinement and dynamics within a Gabor lens help to understand the interaction of the ion beam with the electron column and show the causes of non-neutral plasma instabilities. The diagnosis of the electron cloud properties helps to evaluate the numerical models and to investigate the influen...

ELECTRONIC SYSTEM FOR EXPERIMENTATION IN AC ELECTROGRAVIMETRY I: TECHNIQUE FUNDAMENTALS

Directory of Open Access Journals (Sweden)

Róbinson Torres

Full Text Available Basic fundamentals of AC electrogravimetry are introduced. Their main requirements and characteristics are detailed to establish the design of an electronic system that allows the appropriate extraction of data needed to determine the electrogravimetric transfer function (EGTF and electrochemical impedance (EI, in an experimental set-up for the AC electrogravimetry technique.

A classical model for the electron

International Nuclear Information System (INIS)

Visser, M.

1989-01-01

The construction of classical and semi-classical models for the electron has had a long and distinguished history. Such models are useful more for what they teach us about field theory than what they teach us about the electron. In this Letter I exhibit a classical model of the electron consisting of ordinary electromagnetism coupled with a self-interacting version of Newtonian gravity. The gravitational binding energy of the system balances the electrostatic energy in such a manner that the total rest mass of the electron is finite. (orig.)

Theoretical and experimental study on electron interactions with chlorobenzene: Shape resonances and differential cross sections

Energy Technology Data Exchange (ETDEWEB)

Barbosa, Alessandra Souza [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Varella, Márcio T. do N. [Instituto de Física, Universidade de São Paulo, Rua do Matão 1731, 05508-090 São Paulo, SP (Brazil); Sanchez, Sergio d’A.; Bettega, Márcio H. F., E-mail: bettega@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); Ameixa, João; Limão-Vieira, Paulo; Ferreira da Silva, Filipe [Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Blanco, Francisco [Departamento de Física Atómica, Molecular y Nuclear, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); and others

2016-08-28

In this work, we report theoretical and experimental cross sections for elastic scattering of electrons by chlorobenzene (ClB). The theoretical integral and differential cross sections (DCSs) were obtained with the Schwinger multichannel method implemented with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR). The calculations with the SMCPP method were done in the static-exchange (SE) approximation, for energies above 12 eV, and in the static-exchange plus polarization approximation, for energies up to 12 eV. The calculations with the IAM-SCAR method covered energies up to 500 eV. The experimental differential cross sections were obtained in the high resolution electron energy loss spectrometer VG-SEELS 400, in Lisbon, for electron energies from 8.0 eV to 50 eV and angular range from 7{sup ∘} to 110{sup ∘}. From the present theoretical integral cross section (ICS) we discuss the low-energy shape-resonances present in chlorobenzene and compare our computed resonance spectra with available electron transmission spectroscopy data present in the literature. Since there is no other work in the literature reporting differential cross sections for this molecule, we compare our theoretical and experimental DCSs with experimental data available for the parent molecule benzene.

A Monte-Carlo simulation of the behaviour of electron swarms in hydrogen using an anisotropic scattering model

International Nuclear Information System (INIS)

Blevin, H.A.; Fletcher, J.; Hunter, S.R.

1978-05-01

In a recent paper, a Monte-Carlo simulation of electron swarms in hydrogen using an isotropic scattering model was reported. In this previous work discrepancies between the predicted and measured electron transport parameters were observed. In this paper a far more realistic anisotropic scattering model is used. Good agreement between predicted and experimental data is observed and the simulation code has been used to calculate various parameters which are not directly measurable

Analytical local electron-electron interaction model potentials for atoms

International Nuclear Information System (INIS)

Neugebauer, Johannes; Reiher, Markus; Hinze, Juergen

2002-01-01

Analytical local potentials for modeling the electron-electron interaction in an atom reduce significantly the computational effort in electronic structure calculations. The development of such potentials has a long history, but some promising ideas have not yet been taken into account for further improvements. We determine a local electron-electron interaction potential akin to those suggested by Green et al. [Phys. Rev. 184, 1 (1969)], which are widely used in atom-ion scattering calculations, electron-capture processes, and electronic structure calculations. Generalized Yukawa-type model potentials are introduced. This leads, however, to shell-dependent local potentials, because the origin behavior of such potentials is different for different shells as has been explicated analytically [J. Neugebauer, M. Reiher, and J. Hinze, Phys. Rev. A 65, 032518 (2002)]. It is found that the parameters that characterize these local potentials can be interpolated and extrapolated reliably for different nuclear charges and different numbers of electrons. The analytical behavior of the corresponding localized Hartree-Fock potentials at the origin and at long distances is utilized in order to reduce the number of fit parameters. It turns out that the shell-dependent form of Green's potential, which we also derive, yields results of comparable accuracy using only one shell-dependent parameter

Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural

Energy Technology Data Exchange (ETDEWEB)

Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Neves, R. F. C. [Instituto Federal do Sul de Minas Gerais, Câmpus Poços de Caldas, Minas Gerais (Brazil); Departamento de Física, UFJF, Juiz de Fora, Minas Gerais 36036-900 (Brazil); Lopes, M. C. A. [Departamento de Física, UFJF, Juiz de Fora, Minas Gerais 36036-900 (Brazil); Costa, R. F. da [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, São Paulo 09210-580 (Brazil); Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, Campinas, São Paulo 13083-859 (Brazil); Varella, M. T. do N [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo (Brazil); Bettega, M. H. F. [Departamento de Física, Universidade Federal do Paraná, CP 19044, Curitiba, Paraná 81531-990 (Brazil); Lima, M. A. P., E-mail: maplima@ifi.unicamp.br [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, Campinas, São Paulo 13083-859 (Brazil); García, G. [Instituto de Física Fundamental, CSIC, Serrano 113-bis, 28006 Madrid (Spain); and others

2016-03-28

We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (C{sub 5}H{sub 4}O{sub 2}). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C{sub 5}H{sub 4}O{sub 2}. The measurements were carried out at energies in the range 20–40 eV, and for scattered-electron angles between 10° and 90°. The energy resolution of those experiments was typically ∼80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6–50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail.

Vlasov fluid model with electron pressure

International Nuclear Information System (INIS)

Gerwin, R.

1975-11-01

The Vlasov-ion, fluid-electron model of Freidberg for studying the linear stability of hot-ion pinch configurations is here extended to include electron pressure. Within the framework of an adiabatic electron-gas picture, it is shown that this model is still amenable to the numerical methods described by Lewis and Freidberg

Experimental study of electron temperature gradient influence on impurity turbulent transport in fusion plasmas

International Nuclear Information System (INIS)

Villegas, D.

2010-01-01

Understanding impurity transport is a key to an optimal regime for a future fusion device. In this thesis, the theoretical and experimental influence of the electron temperature gradient R/L Te on heavy impurity transport is analyzed both in Tore Supra and ASDEX Upgrade. The electron temperature profile is modified locally by heating the plasma with little ECRH power deposited at two different radii. Experimental results have been obtained with the impurity transport code (ITC) which has been completed with a genetic algorithm allowing to determine the transport coefficient profiles with more accuracy. Transport coefficient profiles obtained by a quasilinear gyrokinetic code named QuaLiKiz are consistent with the experimental ones despite experimental uncertainties on gradients. In the core dominated by electron modes, the lower R/L Te the lower the nickel diffusion coefficient. The latter tends linearly to the neoclassical level when the instability threshold is approached. The experimental threshold is in agreement with the one computed by QuaLiKiz. Further out, where the plasma is dominated by ITG, which are independent of R/L Te , both experimental and simulated results show no modification in the diffusion coefficient profile. Furthermore, the convection velocity profile is not modified. This is attributed to a very small contribution of the thermodiffusion (1/Z dependence) in the total convection. On ASDEX, the preliminary results, very different from the Tore Supra ones, show a internal transport barrier for impurities located at the same radius as the strong ECRH power deposit. (author) [fr

Improved age-diffusion model for low-energy electron transport in solids. I. Theory

International Nuclear Information System (INIS)

Devooght, J.; Dubus, A.; Dehaes, J.C.

1987-01-01

We have developed in this paper a semianalytical electron transport model designed for parametric studies of secondary-electron emission induced by low-energy electrons (keV range) and by fast light ions (100 keV range). The primary-particle transport is assumed to be known and to give rise to an internal electron source. The importance of the nearly isotropic elastic scattering in the secondary-electron energy range (50 eV) and the slowing-down process strongly reduce the influence of the anisotropy of the internal electron source, and the internal electron flux is nearly isotropic as is evidenced by the experimental results. The differential energy behavior of the inelastic scattering kernel is very complicated and the real kernel is replaced by a synthetic scattering kernel of which parameters are obtained by energy and angle moments conservation. Through a P 1 approximation and the use of the synthetic scattering kernel, the Boltzmann equation is approximated by a diffusion--slowing-down equation for the isotropic part of the internal electron flux. The energy-dependent partial reflection boundary condition reduces to a Neumann-Dirichlet boundary condition. An analytical expression for the Green's function of the diffusion--slowing-down equation with the surface boundary condition is obtained by means of approximations close to the age-diffusion theory and the model allows for transient conditions. Independently from the ''improved age-diffusion'' model, a correction formula is developed in order to take into account the backscattering of primary electrons for an incident-electron problem

Experimental design of high energy electron gun by means of scaling rules

International Nuclear Information System (INIS)

Wojcicki, S.

1996-01-01

The possibility of the design of a new family of electron guns by means of scaling theory of electron-optical devices (EOD) is presented. According to the theory, EOD with a relatively big space charge, as in high energy Pierce type electron guns used in technological equipment, generally cannot be scaled, because of their nonlinear space charge nature. Therefore, the scaling rules are applied here only to the anode zone of the gun, where the electron beam perveance is small, and the cathode lens of gun with considerable space charge remains unchanged. The procedure for scaling a 25 kV and 150 mA gun with cylindrical electron beam into a high voltage 75 kV and 150 mA electron system is given. An experimental investigation proved the high technological quality of a high voltage gun constructed according to the above conception. (author)

Environmental dose rate heterogeneity of beta radiation and its implications for luminescence dating: Monte Carlo modelling and experimental validation

DEFF Research Database (Denmark)

Nathan, R.P.; Thomas, P.J.; Jain, M.

2003-01-01

and identify the likely size of these effects on D-e distributions. The study employs the MCNP 4C Monte Carlo electron/photon transport model, supported by an experimental validation of the code in several case studies. We find good agreement between the experimental measurements and the Monte Carlo...

The energy-deposition model. Electron loss of heavy ions in collisions with neutral atoms at low and intermediate energies

International Nuclear Information System (INIS)

Shevelko, V.P.; Litsarev, M.S.; Kato, D.; Tawara, H.

2010-09-01

Single- and multiple-electron loss processes in collisions of heavy many-electron ions (positive and negative) in collisions with neutral atoms at low and intermediate energies are considered using the energy-deposition model. The DEPOSIT computer code, created earlier to calculate electron-loss cross sections at high projectile energies, is extended for low and intermediate energies. A description of a new version of DEPOSIT code is given, and the limits of validity for collision velocity in the model are discussed. Calculated electron-loss cross sections for heavy ions and atoms (N + , Ar + , Xe + , U + , U 28+ , W, W + , Ge - , Au - ), colliding with neutral atoms (He, Ne, Ar, W) are compared with available experimental and theoretical data at energies E > 10 keV/u. It is found that in most cases the agreement between experimental data and the present model is within a factor of 2. Combining results obtained by the DEPOSIT code at low and intermediate energies with those by the LOSS-R code at high energies (relativistic Born approximation), recommended electron-loss cross sections in a wide range of collision energy are presented. (author)

Self-consistent modeling of electron cyclotron resonance ion sources

International Nuclear Information System (INIS)

Girard, A.; Hitz, D.; Melin, G.; Serebrennikov, K.; Lecot, C.

2004-01-01

In order to predict the performances of electron cyclotron resonance ion source (ECRIS), it is necessary to perfectly model the different parts of these sources: (i) magnetic configuration; (ii) plasma characteristics; (iii) extraction system. The magnetic configuration is easily calculated via commercial codes; different codes also simulate the ion extraction, either in two dimension, or even in three dimension (to take into account the shape of the plasma at the extraction influenced by the hexapole). However the characteristics of the plasma are not always mastered. This article describes the self-consistent modeling of ECRIS: we have developed a code which takes into account the most important construction parameters: the size of the plasma (length, diameter), the mirror ratio and axial magnetic profile, whether a biased probe is installed or not. These input parameters are used to feed a self-consistent code, which calculates the characteristics of the plasma: electron density and energy, charge state distribution, plasma potential. The code is briefly described, and some of its most interesting results are presented. Comparisons are made between the calculations and the results obtained experimentally

Self-consistent modeling of electron cyclotron resonance ion sources

Science.gov (United States)

Girard, A.; Hitz, D.; Melin, G.; Serebrennikov, K.; Lécot, C.

2004-05-01

In order to predict the performances of electron cyclotron resonance ion source (ECRIS), it is necessary to perfectly model the different parts of these sources: (i) magnetic configuration; (ii) plasma characteristics; (iii) extraction system. The magnetic configuration is easily calculated via commercial codes; different codes also simulate the ion extraction, either in two dimension, or even in three dimension (to take into account the shape of the plasma at the extraction influenced by the hexapole). However the characteristics of the plasma are not always mastered. This article describes the self-consistent modeling of ECRIS: we have developed a code which takes into account the most important construction parameters: the size of the plasma (length, diameter), the mirror ratio and axial magnetic profile, whether a biased probe is installed or not. These input parameters are used to feed a self-consistent code, which calculates the characteristics of the plasma: electron density and energy, charge state distribution, plasma potential. The code is briefly described, and some of its most interesting results are presented. Comparisons are made between the calculations and the results obtained experimentally.

Modeling the process of interaction of 10 keV electrons with a plane dielectric surface

Science.gov (United States)

Vokhmyanina, Kristina; Sotnikova, Valentina; Sotnikov, Alexey; Kaplii, Anna; Nikulicheva, Tatyana; Kubankin, Alexandr; Kishin, Ivan

2018-05-01

The effect of guiding of charged particles by dielectric channels is of noticeable interest at the present time. The phenomenon is widely studied experimentally and theoretically but some points still need to be clarified. A previously developed model of interaction of fast electrons with dielectric surface at grazing incidence is used to study the independence of electron deflection on the value of electron beam current. The calculations were performed assuming a smooth dependence of the surface conductivity on the beam current in the 40-3000 nA range.

Experimental determination of spin-dependent electron density by joint refinement of X-ray and polarized neutron diffraction data.

Science.gov (United States)

Deutsch, Maxime; Claiser, Nicolas; Pillet, Sébastien; Chumakov, Yurii; Becker, Pierre; Gillet, Jean Michel; Gillon, Béatrice; Lecomte, Claude; Souhassou, Mohamed

2012-11-01

New crystallographic tools were developed to access a more precise description of the spin-dependent electron density of magnetic crystals. The method combines experimental information coming from high-resolution X-ray diffraction (XRD) and polarized neutron diffraction (PND) in a unified model. A new algorithm that allows for a simultaneous refinement of the charge- and spin-density parameters against XRD and PND data is described. The resulting software MOLLYNX is based on the well known Hansen-Coppens multipolar model, and makes it possible to differentiate the electron spins. This algorithm is validated and demonstrated with a molecular crystal formed by a bimetallic chain, MnCu(pba)(H(2)O)(3)·2H(2)O, for which XRD and PND data are available. The joint refinement provides a more detailed description of the spin density than the refinement from PND data alone.

Microscopy of electronic wave function

International Nuclear Information System (INIS)

Harb, M.

2010-01-01

This work of thesis aims to visualize, on a position sensitive detector, the spatial oscillations of slow electrons (∼ meV) emitted by a threshold photoionization in the presence of an external electric field. The interference figure obtained represents the square magnitude of electronic wavefunction. This fundamental work allows us to have access to the electronic dynamics and thus to highlight several quantum mechanisms that occur at the atomic scale (field Coulomb, electron/electron interaction..). Despite the presence an electronic core in Li atom, we have succeeded, experimentally and for the first time, in visualizing the wave function associated with the quasi-discrete Stark states coupled to the ionization continuum. Besides, using simulations of wave packet propagation, based on the 'Split-operator' method, we have conducted a comprehensive study of the H, Li and Cs atoms while revealing the significant effects of the Stark resonances. A very good agreement, on and off resonances, was obtained between simulated and experimental results. In addition, we have developed a generalized analytical model to understand deeply the function of VMI (Velocity-Map Imaging) spectrometer. This model is based on the paraxial approximation; it is based on matrix optics calculation by making an analogy between the electronic trajectory and the light beam. An excellent agreement was obtained between the model predictions and the experimental results. (author)

Model of twelve properties of a set of organic solvents with graph-theoretical and/or experimental parameters.

Science.gov (United States)

Pogliani, Lionello

2010-01-30

Twelve properties of a highly heterogeneous class of organic solvents have been modeled with a graph-theoretical molecular connectivity modified (MC) method, which allows to encode the core electrons and the hydrogen atoms. The graph-theoretical method uses the concepts of simple, general, and complete graphs, where these last types of graphs are used to encode the core electrons. The hydrogen atoms have been encoded by the aid of a graph-theoretical perturbation parameter, which contributes to the definition of the valence delta, delta(v), a key parameter in molecular connectivity studies. The model of the twelve properties done with a stepwise search algorithm is always satisfactory, and it allows to check the influence of the hydrogen content of the solvent molecules on the choice of the type of descriptor. A similar argument holds for the influence of the halogen atoms on the type of core electron representation. In some cases the molar mass, and in a minor way, special "ad hoc" parameters have been used to improve the model. A very good model of the surface tension could be obtained by the aid of five experimental parameters. A mixed model method based on experimental parameters plus molecular connectivity indices achieved, instead, to consistently improve the model quality of five properties. To underline is the importance of the boiling point temperatures as descriptors in these last two model methodologies. Copyright 2009 Wiley Periodicals, Inc.

Experimental Study of Electronic Quantum Interference, Photonic Crystal Cavity, Photonic Band Edge Effects for Optical Amplification

Science.gov (United States)

2016-01-26

AFRL-RV-PS- AFRL-RV-PS- TR-2016-0003 TR-2016-0003 EXPERIMENTAL STUDY OF ELECTRONIC QUANTUM INTERFERENCE , PHOTONIC CRYSTAL CAVITY, PHOTONIC BAND...EDGE EFFECTS FOR OPTICAL AMPLIFICATION Shawn-Yu Lin Rensselaer Polytechnic Institute 110 8th Street Troy, New York 12180 26 Jan 2016 Final Report...2014 – 11 Jan 2016 4. TITLE AND SUBTITLE Experimental Study of Electronic Quantum Interference , Photonic Crystal Cavity, Photonic Band Edge Effects

Windowless Electron Beam Experimental Irradiation WEBExplr

International Nuclear Information System (INIS)

Heyse, J.

2009-01-01

The design of the MYRRHA/XT-ADS, the European eXperimental Accelerator Driven System for the demonstration of Transmutation, includes a high power windowless spallation target operating with liquid LBE (Lead-Bismuth Eutectic) that will be irradiated with a 600 MeV proton beam at currents of up to 2.5 mA. When considering such a high power windowless target design, a number of questions need to be addressed, such as the stability of the free surface flow and its ability to remove the power deposited by the proton beam by forced convection, the compatibility of a large hot LBE reservoir with the beam line vacuum and the outgassing of the LBE in the spallation target circuit. These issues have been studied during previous experiments supported by numerical simulations. Another crucial point in the development of the spallation target is the demonstration of the safe and stable operation of the free LBE surface during irradiation with a high power proton beam. As a first step in this program, the WEBExpIr (Windowless target Electron Beam Experimental Irradiation) experiment was set up. The purpose of the WEBExpIr experiment was to investigate the influence of LBE surface heating caused by a charged particle beam in a situation representative of the MYRRHA/XT-ADS. More in particular, we wanted to assess possible free surface distortion or shockwave effects in nominal conditions and during sudden beam on/off transient situations, as well as possible enhanced evaporation

Nuclear clustering and the electron screening puzzle

Science.gov (United States)

Bertulani, C. A.; Spitaleri, C.

2018-01-01

Electron screening changes appreciably the magnitude of astrophysical nuclear reactions within stars. This effect is also observed in laboratory experiments on Earth, where atomic electrons are present in the nuclear targets. Theoretical models were developed over the past 30 years and experimental measurements have been carried out to study electron screening in thermonuclear reactions. None of the theoretical models were able to explain the high values of the experimentally determined screening potentials. We explore the possibility that the "electron screening puzzle" is due to nuclear clusterization and polarization e_ects in the fusion reactions. We will discuss the supporting arguments for this scenario.

Experimental and theoretical study of the signal electron motion in fully depleted silicon

International Nuclear Information System (INIS)

Kimmel, N.; Andritschke, R.; Hartmann, R.; Holl, P.; Meidinger, N.; Richter, R.; Strueder, L.

2010-01-01

Imaging spectrometers based on a fully depleted silicon substrate are sensitive over the whole device volume. Therefore, a high detection efficiency for X-rays of up to 20 keV is achieved. Our experimental method facilitates measurements of the detected signal pulse height in a pixel as a function of the photon conversion position in the pixel array. Further analysis of the measurements delivers the size of a signal electron cloud after its drift from the photon conversion position to the storage cells. These results can be used to reconstruct the conversion position of each detected X-ray photon. A reconstruction accuracy of 1μm can be achieved with a pixel size of 51μm. Complementary to the measurements, we have created a physical model of the signal electron collection process. The change of the drift mobility with the electric drift field strength in the detection volume is considered in order to correctly describe the drift speed of the charge cloud. The electric field values and the values of the charge density in the detector volume are delivered by numerical device simulations with the software package 'TeSCA'. Comparisons of the simulations with the measurements confirmed the correctness of the applied physical model. We have thus established a method which enables device designers to simulate the process of signal charge collection in future detector concepts.

Investigation of particle transport through the measurement of the electron source in the Texas Experimental Tokamak

International Nuclear Information System (INIS)

Klepper, C.C.

1985-01-01

The spatial distribution of the electron source was measured spectroscopically in the Texas Experimental Tokamak. The method used involves the measurement of the emissivity of the Balmer α and β lines of neutral hydrogen. Modeling of the corresponding atomic transitions provides a relation between the emissivities and the electron source from the ionization of neutrals. Toroidal distributions were obtained by means of a set of relatively calibrated photodiode amplifier-filter packages referred to as plasma light monitors. Such monitors were distributed toroidally, and attached primarily to radial ports. Specially constructed, absolutely calibrated monitors provided absolute calibration. A scanning, rotating mirror system provided in-out brightness profiles. A TV camera system, viewing the limiter through a tangential port, provided a qualitative description of the poloidal asymmetry. Such description was necessary for the inversion of the rotating mirror data. Using electron density profiles obtained by means of far-infrared interferometry, and integrating the electron sources, the global particle confinement time (tau/sub p/) was computed. Parameter scans were performed in ohmically heated plasmas, varying the toroidal field, the plasma current, the electron density, and the plasma position with respect to the center of the poloidal ring limiter. It was found that tau/sub p/ peaks for a critical density that is independent of the other parameters

Monte Carlo modeling of ion beam induced secondary electrons

Energy Technology Data Exchange (ETDEWEB)

Huh, U., E-mail: uhuh@vols.utk.edu [Biochemistry & Cellular & Molecular Biology, University of Tennessee, Knoxville, TN 37996-0840 (United States); Cho, W. [Electrical and Computer Engineering, University of Tennessee, Knoxville, TN 37996-2100 (United States); Joy, D.C. [Biochemistry & Cellular & Molecular Biology, University of Tennessee, Knoxville, TN 37996-0840 (United States); Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2016-09-15

Ion induced secondary electrons (iSE) can produce high-resolution images ranging from a few eV to 100 keV over a wide range of materials. The interpretation of such images requires knowledge of the secondary electron yields (iSE δ) for each of the elements and materials present and as a function of the incident beam energy. Experimental data for helium ions are currently limited to 40 elements and six compounds while other ions are not well represented. To overcome this limitation, we propose a simple procedure based on the comprehensive work of Berger et al. Here we show that between the energy range of 10–100 keV the Berger et al. data for elements and compounds can be accurately represented by a single universal curve. The agreement between the limited experimental data that is available and the predictive model is good, and has been found to provide reliable yield data for a wide range of elements and compounds. - Highlights: • The Universal ASTAR Yield Curve was derived from data recently published by NIST. • IONiSE incorporated with the Curve will predict iSE yield for elements and compounds. • This approach can also handle other ion beams by changing basic scattering profile.

Modeling of electron behaviors under microwave electric field in methane and air pre-mixture gas plasma assisted combustion

Science.gov (United States)

Akashi, Haruaki; Sasaki, K.; Yoshinaga, T.

2011-10-01

Recently, plasma-assisted combustion has been focused on for achieving more efficient combustion way of fossil fuels, reducing pollutants and so on. Shinohara et al has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power without increase of gas temperature. This suggests that electrons heated by microwave electric field assist the combustion. They also measured emission from 2nd Positive Band System (2nd PBS) of nitrogen during the irradiation. To clarify this mechanism, electron behavior under microwave power should be examined. To obtain electron transport parameters, electron Monte Carlo simulations in methane and air mixture gas have been done. A simple model has been developed to simulate inside the flame. To make this model simple, some assumptions are made. The electrons diffuse from the combustion plasma region. And the electrons quickly reach their equilibrium state. And it is found that the simulated emission from 2nd PBS agrees with the experimental result. Recently, plasma-assisted combustion has been focused on for achieving more efficient combustion way of fossil fuels, reducing pollutants and so on. Shinohara et al has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power without increase of gas temperature. This suggests that electrons heated by microwave electric field assist the combustion. They also measured emission from 2nd Positive Band System (2nd PBS) of nitrogen during the irradiation. To clarify this mechanism, electron behavior under microwave power should be examined. To obtain electron transport parameters, electron Monte Carlo simulations in methane and air mixture gas have been done. A simple model has been developed to simulate inside the flame. To make this model simple, some assumptions are made. The electrons diffuse from the combustion plasma region. And the electrons quickly reach their equilibrium state. And it is found

Experimental procedures to mitigate electron beam induced artifacts during in situ fluid imaging of nanomaterials

International Nuclear Information System (INIS)

Woehl, Taylor J.; Jungjohann, Katherine L.; Evans, James E.; Arslan, Ilke; Ristenpart, William D.; Browning, Nigel D.

2013-01-01

Scanning transmission electron microscopy of various fluid and hydrated nanomaterial samples has revealed multiple imaging artifacts and electron beam–fluid interactions. These phenomena include growth of crystals on the fluid stage windows, repulsion of particles from the irradiated area, bubble formation, and the loss of atomic information during prolonged imaging of individual nanoparticles. Here we provide a comprehensive review of these fluid stage artifacts, and we present new experimental evidence that sheds light on their origins in terms of experimental apparatus issues and indirect electron beam sample interactions with the fluid layer. A key finding is that many artifacts are a result of indirect electron beam interactions, such as production of reactive radicals in the water by radiolysis, and the associated crystal growth. The results presented here will provide a methodology for minimizing fluid stage imaging artifacts and acquiring quantitative in situ observations of nanomaterial behavior in a liquid environment

Experimental procedures to mitigate electron beam induced artifacts during in situ fluid imaging of nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Woehl, Taylor J., E-mail: tjwoehl@ucdavis.edu [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, CA 95616 (United States); Jungjohann, Katherine L. [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, CA 95616 (United States); Evans, James E. [Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616 (United States); Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Arslan, Ilke [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, CA 95616 (United States); Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Ristenpart, William D. [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, CA 95616 (United States); Department of Food Science and Technology, University of California, Davis, Davis, CA 95616 (United States); Browning, Nigel D. [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, CA 95616 (United States); Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616 (United States); Pacific Northwest National Laboratory, Richland, WA 99352 (United States)

2013-04-15

Scanning transmission electron microscopy of various fluid and hydrated nanomaterial samples has revealed multiple imaging artifacts and electron beam–fluid interactions. These phenomena include growth of crystals on the fluid stage windows, repulsion of particles from the irradiated area, bubble formation, and the loss of atomic information during prolonged imaging of individual nanoparticles. Here we provide a comprehensive review of these fluid stage artifacts, and we present new experimental evidence that sheds light on their origins in terms of experimental apparatus issues and indirect electron beam sample interactions with the fluid layer. A key finding is that many artifacts are a result of indirect electron beam interactions, such as production of reactive radicals in the water by radiolysis, and the associated crystal growth. The results presented here will provide a methodology for minimizing fluid stage imaging artifacts and acquiring quantitative in situ observations of nanomaterial behavior in a liquid environment.

Comparison of GEANT4 very low energy cross section models with experimental data in water

DEFF Research Database (Denmark)

Incerti, S; Ivanchenko, A; Karamitros, M

2010-01-01

The GEANT4 general-purpose Monte Carlo simulation toolkit is able to simulate physical interaction processes of electrons, hydrogen and helium atoms with charge states (H0, H+) and (He0, He+, He2+), respectively, in liquid water, the main component of biological systems, down to the electron volt...... of electromagnetic interactions within the GEANT4 toolkit framework (since GEANT4 version 9.3 beta). This work presents a quantitative comparison of these physics models with a collection of experimental data in water collected from the literature....

A model and computer code for the Monte Carlo simulation of relativistic electron and positron penetration through matter

International Nuclear Information System (INIS)

Ismail, M.; Liljequist, D.

1986-10-01

In the present model, the treatment of elastic scattering is based on the similarity of multiple scattering processes with equal transport mean free path /LAMBDA/sub(tr). Elastic scattering events are separated by an artificially enlarged mean free path. In such events, scattering is optionally performed either by means of a single, energy-dependent scattering angle, or by means of a scattering angle distribution of the same form as the screened Rutherford cross section, but with an artificial screening factor. The physically correct /LAMBDA/sub(tr) value is obtained by appropriate choice of scattering angle or screening factor, respectively. We find good agreement with experimental transmission and with energy loss distributions. The Rutherford-like model gives good agreement with experimental angular distribution even for the penetration of very thin layers. Treatment of electron energy loss is based on the partial CSDA method: energy losses W WMINSE are treated as discrete electron-electron or positron-electron scattering events. Similarly, for bremsstrahlung photon energies W WMINR are treated at discrete events. The sensitivity of the model to the parameters WMINSE and WMINR is studied. WMINR can, in practise, be made negligibly small, and WMINSE can without any excessive computer time be made as small as to give results in good agreement with experiment and with computations based on Landau theory of straggling. Using this model, we study some of the characteristic features of relativistic electron transmission, energy loss distributions, straggling, angular distributions and trajectories. (authors)

Current Analysis and Modeling of Fullerene Single-Electron Transistor at Room Temperature

Science.gov (United States)

Khadem Hosseini, Vahideh; Ahmadi, Mohammad Taghi; Afrang, Saeid; Ismail, Razali

2017-07-01

Single-electron transistors (SETs) are interesting electronic devices that have become key elements in modern nanoelectronic systems. SETs operate quickly because they use individual electrons, with the number transferred playing a key role in their switching behavior. However, rapid transmission of electrons can cause their accumulation at the island, affecting the I- V characteristic. Selection of fullerene as a nanoscale zero-dimensional material with high stability, and controllable size in the fabrication process, can overcome this charge accumulation issue and improve the reliability of SETs. Herein, the current in a fullerene SET is modeled and compared with experimental data for a silicon SET. Furthermore, a weaker Coulomb staircase and improved reliability are reported. Moreover, the applied gate voltage and fullerene diameter are found to be directly associated with the I- V curve, enabling the desired current to be achieved by controlling the fullerene diameter.

The electronic-commerce-oriented virtual merchandise model

Science.gov (United States)

Fang, Xiaocui; Lu, Dongming

2004-03-01

Electronic commerce has been the trend of commerce activities. Providing with Virtual Reality interface, electronic commerce has better expressing capacity and interaction means. But most of the applications of virtual reality technology in EC, 3D model is only the appearance description of merchandises. There is almost no information concerned with commerce information and interaction information. This resulted in disjunction of virtual model and commerce information. So we present Electronic Commerce oriented Virtual Merchandise Model (ECVMM), which combined a model with commerce information, interaction information and figure information of virtual merchandise. ECVMM with abundant information provides better support to information obtainment and communication in electronic commerce.

Multiscale modelling and experimentation of hydrogen embrittlement in aerospace materials

Science.gov (United States)

Jothi, Sathiskumar

Pulse plated nickel and nickel based superalloys have been used extensively in the Ariane 5 space launcher engines. Large structural Ariane 5 space launcher engine components such as combustion chambers with complex microstructures have usually been manufactured using electrodeposited nickel with advanced pulse plating techniques with smaller parts made of nickel based superalloys joined or welded to the structure to fabricate Ariane 5 space launcher engines. One of the major challenges in manufacturing these space launcher components using newly developed materials is a fundamental understanding of how different materials and microstructures react with hydrogen during welding which can lead to hydrogen induced cracking. The main objective of this research has been to examine and interpret the effects of microstructure on hydrogen diffusion and hydrogen embrittlement in (i) nickel based superalloy 718, (ii) established and (iii) newly developed grades of pulse plated nickel used in the Ariane 5 space launcher engine combustion chamber. Also, the effect of microstructures on hydrogen induced hot and cold cracking and weldability of three different grades of pulse plated nickel were investigated. Multiscale modelling and experimental methods have been used throughout. The effect of microstructure on hydrogen embrittlement was explored using an original multiscale numerical model (exploiting synthetic and real microstructures) and a wide range of material characterization techniques including scanning electron microscopy, 2D and 3D electron back scattering diffraction, in-situ and ex-situ hydrogen charged slow strain rate tests, thermal spectroscopy analysis and the Varestraint weldability test. This research shows that combined multiscale modelling and experimentation is required for a fundamental understanding of microstructural effects in hydrogen embrittlement in these materials. Methods to control the susceptibility to hydrogen induced hot and cold cracking and

Theoretical modeling of electronic transport in molecular devices

Science.gov (United States)

Piccinin, Simone

In this thesis a novel approach for simulating electronic transport in nanoscale structures is introduced. We consider an open quantum system (the electrons of structure) accelerated by an external electromotive force and dissipating energy through inelastic scattering with a heat bath (phonons) acting on the electrons. This method can be regarded as a quantum-mechanical extension of the semi-classical Boltzmann transport equation. We use periodic boundary conditions and employ Density Functional Theory to recast the many-particle problem in an effective single-particle mean-field problem. By explicitly treating the dissipation in the electrodes, the behavior of the potential is an outcome of our method, at variance with the scattering approaches based on the Landauer formalism. We study the self-consistent steady-state solution, analyzing the out-of-equilibrium electron distribution, the electrical characteristics, the behavior of the self-consistent potential and the density of states of the system. We apply the method to the study of electronic transport in several molecular devices, consisting of small organic molecules or atomic wires sandwiched between gold surfaces. For gold wires we recover the experimental evidence that transport in short wires is ballistic, independent of the length of the wire and with conductance of one quantum. In benzene-1,4-dithiol we find that the delocalization of the frontier orbitals of the molecule is responsible for the high value of conductance and that, by inserting methylene groups to decouple the sulfur atoms from the carbon ring, the current is reduced, in agreement with the experimental measurements. We study the effect a geometrical distortion in a molecular device, namely the relative rotation of the carbon rings in a biphenyl-4,4'-dithiol molecule. We find that the reduced coupling between pi orbitals of the rings induced by the rotation leads to a reduction of the conductance and that this behavior is captured by a

Band-structure-based collisional model for electronic excitations in ion-surface collisions

International Nuclear Information System (INIS)

Faraggi, M.N.; Gravielle, M.S.; Alducin, M.; Silkin, V.M.; Juaristi, J.I.

2005-01-01

Energy loss per unit path in grazing collisions with metal surfaces is studied by using the collisional and dielectric formalisms. Within both theories we make use of the band-structure-based (BSB) model to represent the surface interaction. The BSB approach is based on a model potential and provides a precise description of the one-electron states and the surface-induced potential. The method is applied to evaluate the energy lost by 100 keV protons impinging on aluminum surfaces at glancing angles. We found that when the realistic BSB description of the surface is used, the energy loss obtained from the collisional formalism agrees with the dielectric one, which includes not only binary but also plasmon excitations. The distance-dependent stopping power derived from the BSB model is in good agreement with available experimental data. We have also investigated the influence of the surface band structure in collisions with the Al(100) surface. Surface-state contributions to the energy loss and electron emission probability are analyzed

Diffusive and convective transport modelling from analysis of ECRH-stimulated electron heat wave propagation. [ECRH (Electron Cyclotron Resonance Heating)

Energy Technology Data Exchange (ETDEWEB)

Erckmann, V; Gasparino, U; Giannone, L. (Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)) (and others)

1992-01-01

ECRH power modulation experiments in toroidal devices offer the chance to analyze the electron heat transport more conclusively: the electron heat wave propagation can be observed by ECE (or SX) leading to radial profiles of electron temperature modulation amplitude and time delay (phase shift). Taking also the stationary power balance into account, the local electron heat transport can be modelled by a combination of diffusive and convective transport terms. This method is applied to ECRH discharges in the W7-AS stellarator (B=2.5T, R=2m, a[<=]18 cm) where the ECRH power deposition is highly localized. In W7-AS, the T[sub e] modulation profiles measured by a high resolution ECE system are the basis for the local transport analysis. As experimental errors limit the separation of diffusive and convective terms in the electron heat transport for central power deposition, also ECRH power modulation experiments with off-axis deposition and inward heat wave propagation were performed (with 70 GHz o-mode as well as with 140 GHz x-mode for increased absorption). Because collisional electron-ion coupling and radiative losses are only small, low density ECRH discharges are best candidates for estimating the electron heat flux from power balance. (author) 2 refs., 3 figs.

D-region electron density and effective recombination coefficients during twilight – experimental data and modelling during solar proton events

Directory of Open Access Journals (Sweden)

A. Osepian

2009-10-01

Full Text Available Accurate measurements of electron density in the lower D-region (below 70 km altitude are rarely made. This applies both with regard to measurements by ground-based facilities and by sounding rockets, and during both quiet conditions and conditions of energetic electron precipitation. Deep penetration into the atmosphere of high-energy solar proton fluxes (during solar proton events, SPE produces extra ionisation in the whole D-region, including the lower altitudes, which gives favourable conditions for accurate measurements using ground-based facilities. In this study we show that electron densities measured with two ground-based facilities at almost the same latitude but slightly different longitudes, provide a valuable tool for validation of model computations. The two techniques used are incoherent scatter of radio waves (by the EISCAT 224 MHz radar in Tromsø, Norway, 69.6° N, 19.3° E, and partial reflection of radio-waves (by the 2.8 MHz radar near Murmansk, Russia, 69.0° N, 35.7° E. Both radars give accurate electron density values during SPE, from heights 57–60 km and upward with the EISCAT radar and between 55–70 km with the partial reflection technique. Near noon, there is little difference in the solar zenith angle between the two locations and both methods give approximately the same values of electron density at the overlapping heights. During twilight, when the difference in solar zenith angles increases, electron density values diverge. When both radars are in night conditions (solar zenith angle >99° electron densities at the overlapping altitudes again become equal. We use the joint measurements to validate model computations of the ionospheric parameters f+, λ, αeff and their variations during solar proton events. These parameters are important characteristics of the lower ionosphere structure which cannot be determined by other methods.

An experimental assessment of methods used to compute secondary electron emission yield for tungsten and molybdenum electrodes based on exposure to Alcator C-Mod scrape-off layer plasmas

Science.gov (United States)

McCarthy, W.; LaBombard, B.; Brunner, D.; Kuang, A. Q.

2018-03-01

Plasma potentials computed from Langmuir probe data rely on a method to account for secondary electron emission (SEE) from the electrodes. However, significant variations exist among published models for SEE and the reported experimental parameters used to evaluate them. As a means to critically assess SEE computation methods, two of four tungsten electrodes on a Langmuir-Mach probe head were replaced with molybdenum and exposed to Alcator C-Mod boundary plasmas where electron temperatures exceed 50 eV and SEE becomes significant. In this situation, plasma potentials computed for either material should be identical—the SEE evaluation method should properly account for the differences in SEE yields. Of the six methods used to compute SEE, two are found to produce consistent results (Sternglass model with Bronstein experimental parameters and Young-Dekker model with Bronstein experimental parameters). In contrast, the method previously used for C-Mod data analysis (Sternglass model with Kollath parameters) was found to be inconsistent. We have since adopted Young-Dekker-Bronstein as the preferred method.

Experimental study of pulmonary thromboembolism ischemia-reperfusion injury in canine model

International Nuclear Information System (INIS)

Li Jianjun; Zhai Renyou; Zhang Dongpo; Huang Qiang; Yu Ping; Dai Dingke; Bao Na

2009-01-01

Objective: To establish a canine model of pulmonary thromboembolism ischemia- reperfusion injury (PTE IRI) that may be used for imaging study. Methods: Ten male and 10 female healthy mongrel canines with (18.6±0.8) kg/body weight, were used. A Swan-Ganz catheter was introduced into the right internal jugular vein via a preset percutaneous sheath using the Seldinger technique, and then was with further insertion the pulmonary artery. Balloon occlusion of the right inferior lobe pulmonary artery for 4 hours was followed by removing the catheter and ending with 4 hours of reperfusion. CT was performed before ischemia, 4 h after ischemia and 4 h after reperfusion. At last, dogs were killed and the bilateral inferior lung tissues were prepared for the examination by light and electronic microscopy. Results: All canine models were successfully developed pulmonary thromboembolism ischemia-reperfusion injury. The examination of CT, light and electron microscopy consistently indicated the presence of permeability pulmonary edema after reperfusion. Conclusions: A closed-chest canine model in vivo of pulmonary thromboembolism ischemia-reperfusion injury can be established with virtual pathophysiological process in human and be as well as for imaging experimental study. (authors)

Injury Based on Its Study in Experimental Models

Directory of Open Access Journals (Sweden)

M. Mendes-Braz

2012-01-01

Full Text Available The present review focuses on the numerous experimental models used to study the complexity of hepatic ischemia/reperfusion (I/R injury. Although experimental models of hepatic I/R injury represent a compromise between the clinical reality and experimental simplification, the clinical transfer of experimental results is problematic because of anatomical and physiological differences and the inevitable simplification of experimental work. In this review, the strengths and limitations of the various models of hepatic I/R are discussed. Several strategies to protect the liver from I/R injury have been developed in animal models and, some of these, might find their way into clinical practice. We also attempt to highlight the fact that the mechanisms responsible for hepatic I/R injury depend on the experimental model used, and therefore the therapeutic strategies also differ according to the model used. Thus, the choice of model must therefore be adapted to the clinical question being answered.

Modeling of Experimental Adsorption Isotherm Data

Directory of Open Access Journals (Sweden)

Xunjun Chen

2015-01-01

Full Text Available Adsorption is considered to be one of the most effective technologies widely used in global environmental protection areas. Modeling of experimental adsorption isotherm data is an essential way for predicting the mechanisms of adsorption, which will lead to an improvement in the area of adsorption science. In this paper, we employed three isotherm models, namely: Langmuir, Freundlich, and Dubinin-Radushkevich to correlate four sets of experimental adsorption isotherm data, which were obtained by batch tests in lab. The linearized and non-linearized isotherm models were compared and discussed. In order to determine the best fit isotherm model, the correlation coefficient (r2 and standard errors (S.E. for each parameter were used to evaluate the data. The modeling results showed that non-linear Langmuir model could fit the data better than others, with relatively higher r2 values and smaller S.E. The linear Langmuir model had the highest value of r2, however, the maximum adsorption capacities estimated from linear Langmuir model were deviated from the experimental data.

Mobile interstitial model and mobile electron model of mechano-induced luminescence in coloured alkali halide crystals

International Nuclear Information System (INIS)

Chandra, B.P.; Singh, Seema; Ojha, Bharti; Shrivastava, R.G.

1996-01-01

A theoretical study is made on the mobile interstitial and mobile electron models of mechano-induced luminescence in coloured alkali halide crystals. Equations derived indicate that the mechanoluminescence intensity should depend on several factors like strain rate, applied stress, temperature, density of F-centres and volume of crystal. The equations also involve the efficiency and decay time of mechanoluminescence. Results of mobile interstitial and mobile electron models are compared with the experimental observations, which indicated that the latter is more suitable as compared to the former. From the temperature dependence of ML, the energy gaps between the dislocation band and ground state of F-centre is calculated which are 0.08, 0.072 and 0.09 eV for KCl, KBr and NaCl crystals, respectively. The theory predicts that the decay of ML intensity is related to the process of stress relaxation in crystals. (author). 33 refs., 5 figs., 1 tab

Kinetic Adsorption Study of Silver Nanoparticles on Natural Zeolite: Experimental and Theoretical Models

Directory of Open Access Journals (Sweden)

Alvaro Ruíz-Baltazar

2015-12-01

Full Text Available In this research, the adsorption capacity of Ag nanoparticles on natural zeolite from Oaxaca is presented. In order to describe the adsorption mechanism of silver nanoparticles on zeolite, experimental adsorption models for Ag ions and Ag nanoparticles were carried out. These experimental data obtained by the atomic absorption spectrophotometry technique were compared with theoretical models such as Lagergren first-order, pseudo-second-order, Elovich, and intraparticle diffusion. Correlation factors R2 of the order of 0.99 were observed. Analysis by transmission electron microscopy describes the distribution of the silver nanoparticles on the zeolite outer surface. Additionally, a chemical characterization of the material was carried out through a dilution process with lithium metaborate. An average value of 9.3 in the Si/Al ratio was observed. Factors such as the adsorption behavior of the silver ions and the Si/Al ratio of the zeolite are very important to support the theoretical models and establish the adsorption mechanism of Ag nanoparticles on natural zeolite.

Numerical model of electron cyclotron resonance ion source

Directory of Open Access Journals (Sweden)

V. Mironov

2015-12-01

Full Text Available Important features of the electron cyclotron resonance ion source (ECRIS operation are accurately reproduced with a numerical code. The code uses the particle-in-cell technique to model the dynamics of ions in ECRIS plasma. It is shown that a gas dynamical ion confinement mechanism is sufficient to provide the ion production rates in ECRIS close to the experimentally observed values. Extracted ion currents are calculated and compared to the experiment for a few sources. Changes in the simulated extracted ion currents are obtained with varying the gas flow into the source chamber and the microwave power. Empirical scaling laws for ECRIS design are studied and the underlying physical effects are discussed.

Experimental model of the device for detection of nuclear cycle materials by photoneutron technology

International Nuclear Information System (INIS)

Bakalyarov, A.M.; Karetnikov, M.D.; Kozlov, K.N.; Lebedev, V.I.; Meleshko, E.A.; Obinyakov, B.A.; Ostashev, I.E.; Tupikin, N.A.; Yakovlev, G.V.

2007-01-01

The inherent complexity of sea container control makes them potentially dangerous for smuggling nuclear materials. The experts believe that only active technologies based on recording the products of induced radiation from sensitive materials might solve the problem. The paper reports on the experimental model of the device on the basis of the electron LINAC U-28 for detection of nuclear materials by photonuclear technology. The preliminary numerical optimization of output units (converter, filter, collimator) for shaping the bremsstrahlung was carried out. The setup of experimental device and initial results of recording the prompt and delayed fission products are discussed

Rapid model building of beta-sheets in electron-density maps.

Science.gov (United States)

Terwilliger, Thomas C

2010-03-01

A method for rapidly building beta-sheets into electron-density maps is presented. beta-Strands are identified as tubes of high density adjacent to and nearly parallel to other tubes of density. The alignment and direction of each strand are identified from the pattern of high density corresponding to carbonyl and C(beta) atoms along the strand averaged over all repeats present in the strand. The beta-strands obtained are then assembled into a single atomic model of the beta-sheet regions. The method was tested on a set of 42 experimental electron-density maps at resolutions ranging from 1.5 to 3.8 A. The beta-sheet regions were nearly completely built in all but two cases, the exceptions being one structure at 2.5 A resolution in which a third of the residues in beta-sheets were built and a structure at 3.8 A in which under 10% were built. The overall average r.m.s.d. of main-chain atoms in the residues built using this method compared with refined models of the structures was 1.5 A.

Experimental transmission electron microscopy studies and phenomenological model of bismuth-based superconducting compounds; Etudes experimentales par microscopie electronique en transmission et modele phenomenologique des composes supraconducteurs a base de bismuth

Energy Technology Data Exchange (ETDEWEB)

Elboussiri, Khalid

1991-09-26

The main part of this thesis is devoted to an experimental study by transmission electron microscopy of the different phases of the superconducting bismuth cuprates Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4}. In high resolution electron microscopy, the two types of incommensurate modulation realized in these compounds have been observed. A model of structure has been proposed from which the simulated images obtained are consistent with observations. The medium resolution images correlated with the electron diffraction data have revealed existence of a multi-soliton regime with latent lock in phases of commensurate periods between 4b and 10b. At last, a description of different phases of these compounds as a result of superstructures from a disordered perovskite type structure is proposed (author) [French] Le travail presente dans cette these consiste en une etude experimentale essentiellement par microscopie electronique en transmission des differentes phases supraconductrices presentes dans les composes appartenant a la famille des cuprates de bismuth Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4}. Les obsevations de microscopie electronique a haute resolution ont permis de mettre en evidence les differentes modulations incommensurables realisees dans ces composes. Un modele de structure est propose et a permis d'obtenir des images simulees compatibles avec les observations. D'autre part, les observations de microscopie electronique en moyenne resolution sur ces composes, combinees avec les resultats de diffraction electronique, ont montre l'existence d'un regime multisoliton associe a des phases de Lock-in latentes de parametres compris entre 4b et 10b. Enfin, une description des differentes phases de ces composes en terme de surstructures derivees de structure perovskite desordonnee est exposee. (auteur)

Experimental study of single-electron loss by Ar+ ions in rare-gas atoms

Science.gov (United States)

Reyes, P. G.; Castillo, F.; Martínez, H.

2001-04-01

Absolute differential and total cross sections for single-electron loss were measured for Ar+ ions on rare-gas atoms in the laboratory energy range of 1.5 to 5.0 keV. The electron loss cross sections for all the targets studied are found to be in the order of magnitude between 10-19 and 10-22 cm2, and show a monotonically increasing behaviour as a function of the incident energy. The behaviour of the total single-electron loss cross sections with the atomic target number, Zt, shows different dependences as the collision energy increases. In all cases the present results display experimental evidence of saturation in the single-electron loss cross section as the atomic number of the target increases.

RAMAN LIGHT SCATTERING IN PSEUDOSPIN-ELECTRON MODEL AT STRONG PSEUDOSPIN-ELECTRON INTERACTION

Directory of Open Access Journals (Sweden)

T.S.Mysakovych

2004-01-01

Full Text Available Anharmonic phonon contributions to Raman scattering in locally anharmonic crystal systems in the framework of the pseudospin-electron model with tunneling splitting of levels are investigated. The case of strong pseudospin-electron coupling is considered. Pseudospin and electron contributions to scattering are taken into account. Frequency dependences of Raman scattering intensity for different values of model parameters and for different polarization of scattering and incident light are investigated.

Teaching Chemistry with Electron Density Models

Science.gov (United States)

Shusterman, Gwendolyn P.; Shusterman, Alan J.

1997-07-01

Linus Pauling once said that a topic must satisfy two criteria before it can be taught to students. First, students must be able to assimilate the topic within a reasonable amount of time. Second, the topic must be relevant to the educational needs and interests of the students. Unfortunately, the standard general chemistry textbook presentation of "electronic structure theory", set as it is in the language of molecular orbitals, has a difficult time satisfying either criterion. Many of the quantum mechanical aspects of molecular orbitals are too difficult for most beginning students to appreciate, much less master, and the few applications that are presented in the typical textbook are too limited in scope to excite much student interest. This article describes a powerful new method for teaching students about electronic structure and its relevance to chemical phenomena. This method, which we have developed and used for several years in general chemistry (G.P.S.) and organic chemistry (A.J.S.) courses, relies on computer-generated three-dimensional models of electron density distributions, and largely satisfies Pauling's two criteria. Students find electron density models easy to understand and use, and because these models are easily applied to a broad range of topics, they successfully convey to students the importance of electronic structure. In addition, when students finally learn about orbital concepts they are better prepared because they already have a well-developed three-dimensional picture of electronic structure to fall back on. We note in this regard that the types of models we use have found widespread, rigorous application in chemical research (1, 2), so students who understand and use electron density models do not need to "unlearn" anything before progressing to more advanced theories.

Calculated and experimental low-loss electron energy loss spectra of dislocations in diamond and GaN

CERN Document Server

Jones, R; Gutiérrez-Sosa, A; Bangert, U; Heggie, M I; Blumenau, A T; Frauenheim, T; Briddon, P R

2002-01-01

First-principles calculations of electron energy loss (EEL) spectra for bulk GaN and diamond are compared with experimental spectra acquired with a scanning tunnelling electron microscope offering ultra-high-energy resolution in low-loss energy spectroscopy. The theoretical bulk low-loss EEL spectra, in the E sub g to 10 eV range, are in good agreement with experimental data. Spatially resolved spectra from dislocated regions in both materials are distinct from bulk spectra. The main effects are, however, confined to energy losses lying above the band edge. The calculated spectra for low-energy dislocations in diamond are consistent with the experimental observations, but difficulties remain in understanding the spectra of threading dislocations in GaN.

Ab-initio modeling of an iron laser-induced plasma: Comparison between theoretical and experimental atomic emission spectra

International Nuclear Information System (INIS)

Colgan, J.; Judge, E.J.; Kilcrease, D.P.; Barefield, J.E.

2014-01-01

We report on efforts to model the Fe emission spectrum generated from laser-induced breakdown spectroscopy (LIBS) measurements on samples of pure iron oxide (Fe 2 O 3 ). Our modeling efforts consist of several components. We begin with ab-initio atomic structure calculations performed by solving the Hartree–Fock equations for the neutral and singly ionized stages of Fe. Our energy levels are then adjusted to their experimentally known values. The atomic transition probabilities and atomic collision quantities are also computed in an ab-initio manner. We perform LTE or non-LTE calculations that generate level populations and, subsequently, an emission spectrum for the iron plasma for a range of electron temperatures and electron densities. Such calculations are then compared to the experimental spectrum. We regard our work as a preliminary modeling effort that ultimately strives towards the modeling of emission spectra from even more complex samples where less atomic data are available. - Highlights: • LIBS plasma of iron oxide • Ab-initio theoretical Modeling • Discussion of LTE versus non-LTE criteria and assessment • Boltzmann plots for Fe—determination of when LTE is a valid assumption • Emission spectra for Fe—comparison of theoretical modeling and measurement: good agreement obtained

Present status of the ETL electron linac and associated experimental facilities

International Nuclear Information System (INIS)

Tomimasu, T.

1983-01-01

The 500-MeV electron linac ''TELL'' is operated since Dec. 1980. The main features of TELL are high efficiency, high current - high power acceleration and economical beam sharing to four experimental rooms at the same time. The available beam current is 240 mA (--180 μA ) at 300 MeV at present. A pion channel ( QQDQ ) with solid angle larger than 0.15 sr is under construction. Research on establishing spectro-dosimetric standards of high energy - high intensity electrons, X-rays and pions are in progress. The 600-MeV storage ring ''TERAS'' is operated since Oct. 1981. The circumference is 31.45 m and lambdasub(p) is 22 A. The maximum stored current is 150 mA and 1/e lifetime is 1.5 hours at present. Studies on photometry and soft X ray standards, electronic materials and lithography technology are in progress using synchrotron radiation. (author)

Developing Argumentation Strategies in Electronic Dialogs: Is Modeling Effective?

Science.gov (United States)

Mayweg-Paus, Elisabeth; Macagno, Fabrizio; Kuhn, Deanna

2016-01-01

The study presented here examines how interacting with a more capable interlocutor influences use of argumentation strategies in electronic discourse. To address this question, 54 young adolescents participating in an intervention centered on electronic peer dialogs were randomly assigned to either an experimental or control condition. In both…

Angular momentum branching ratios for electron-induced ionization: Atomic and model calculations

International Nuclear Information System (INIS)

Mehl, M.J.; Einstein, T.L.

1987-01-01

We present calculations of the matrix elements for electron-induced ionization of core electrons of atoms. We use both self-consistent atomic potentials for accuracy and model potentials to gain physical insight. We pay particular attention to the angular momentum distribution of the two final-state electrons, especially when one of them lies near what would be the Fermi energy in a solid (i.e., as in an absorption fine-structure experiment). For nodeless core wave functions, in the dominant channel both final-state electrons have angular momentum one greater than that of the initial core state. For sufficiently deeply bound states, this first approximate selection rule holds until the incident electron energy exceeds the ionization threshold by at least 500 eV, i.e., over the experimentally relevant range. It is also possible to determine the angular momentum distribution of the final-state electron. The EXAFS-like electron tends to have angular momentum one greater than that of the initial core state, even in some cases where the first approximate selection rule does not hold. (EXAFS is extended x-ray-absorption fine structure.) The strongest trend is that the dipole component in a partial-wave expansion of the Coulomb interaction dominates the matrix element. In these studies, careful treatment of not just the core state but also the unbound states is crucial; we show that the conventional orthogonalized plane-wave approximation is inadequate, giving incorrect ordering of the channels. For model potentials with an adjustable screening length, low-lying bound resonances are found to play an important role

A Model for Electronic Good Governance in Electronic Learning Sector of Iran

Directory of Open Access Journals (Sweden)

Alireza Moghaddasi

2016-10-01

Full Text Available Despite the various models and frameworks on electronic good governance are introduced, the multiple dimensions model of electronic good governance in the field of e-Learning has not been reviewed this subject in a integrated, comprehensive, process-oriented and systematic model. In this article, in order to explain the process of electronic good governance, by a systematic review of the related literature and backgrounds, all factors were identified using meta-synthesis methodology. Then, based on grounded theory methodology and Strauss and Corbin paradigmatic approach, the open, axial and selective coding were conducted. In the following, by using survey method, we determined the importance and priority of all proposed factors. It was also indicated that this research was innovative in the fields of methodology, results and the proposed model which had not been considered in the previous researches. So that, the proposed model resolved the shortcomings of past researches and made it possible for the public sector, private and civil society organizations to consider the process of establishing electronic good governance in e-Learning sector in Iran as a dynamic process.

Analysis of operating model of electronic invoice colombian Colombian electronic billing analysis of the operational model

Directory of Open Access Journals (Sweden)

Sérgio Roberto da Silva

2016-06-01

Full Text Available Colombia has been one of the first countries to introduce electronic billing process on a voluntary basis, from a traditional to a digital version. In this context, the article analyzes the electronic billing process implemented in Colombia and the advantages. Methodological research is applied, qualitative, descriptive and documentary; where the regulatory framework and the conceptualization of the model is identified; the process of adoption of electronic billing is analyzed, and finally the advantages and disadvantages of its implementation is analyzed. The findings indicate that the model applied in Colombia to issue an electronic billing in sending and receiving process, is not complex, but it requires a small adequate infrastructure and trained personnel to reach all sectors, especially the micro and business which is the largest business network in the country.

Experimental tests of transport models using modulated ECH

International Nuclear Information System (INIS)

DeBoo, J.C.; Kinsey, J.E.; Bravenec, R.

1998-12-01

Both the dynamic and equilibrium thermal responses of an L-mode plasma to repetitive ECH heat pulses were measured and compared to predictions from several thermal transport models. While no model consistently agreed with all observations, the GLF23 model was most consistent with the perturbated electron and ion temperature responses for one of the cases studied which may indicate a key role played by electron modes in the core of these discharges. Generally, the IIF and MM models performed well for the perturbed electron response while the GLF23 and IFS/PPPL models agreed with the perturbed ion response for all three cases studied. No single model agreed well with the equilibrium temperature profiles measured

Multipurpose modular experimental station for the DiProI beamline of Fermi-Elettra free electron laser

Energy Technology Data Exchange (ETDEWEB)

Pedersoli, Emanuele; Capotondi, Flavio; Cocco, Daniele; Kaulich, Burkhard; Menk, Ralf H; Locatelli, Andrea; Mentes, Tevfik O; Spezzani, Carlo; Sandrin, Gilio; Bacescu, Daniel M; Kiskinova, Maya [Fermi, Elettra Sincrotrone Trieste, SS 14 - km 163.5, 34149 Basovizza, Trieste (Italy); Zangrando, Marco [Fermi, Elettra Sincrotrone Trieste, SS 14 - km 163.5, 34149 Basovizza, Trieste (Italy); IOM CNR, Laboratorio TASC, SS 14 - km 163.5, 34149 Basovizza, Trieste (Italy); Bajt, Sasa; Barthelmess, Miriam [Photon Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Barty, Anton; Schulz, Joachim; Gumprecht, Lars [Centre for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Chapman, Henry N [Centre for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); University of Hamburg, Notkestrasse 85, 22607 Hamburg (Germany); Nelson, A J; Frank, Matthias [Physical and Life Sciences, LLNL, 7000 East Avenue, Livermore, California 94550 (United States); others, and

2011-04-15

We present a compact modular apparatus with a flexible design that will be operated at the DiProI beamline of the Fermi-Elettra free electron laser (FEL) for performing static and time-resolved coherent diffraction imaging experiments, taking advantage of the full coherence and variable polarization of the short seeded FEL pulses. The apparatus has been assembled and the potential of the experimental setup is demonstrated by commissioning tests with coherent synchrotron radiation. This multipurpose experimental station will be open to general users after installation at the Fermi-Elettra free electron laser in 2011.

Multipurpose modular experimental station for the DiProI beamline of Fermi-Elettra free electron laser

International Nuclear Information System (INIS)

Pedersoli, Emanuele; Capotondi, Flavio; Cocco, Daniele; Kaulich, Burkhard; Menk, Ralf H.; Locatelli, Andrea; Mentes, Tevfik O.; Spezzani, Carlo; Sandrin, Gilio; Bacescu, Daniel M.; Kiskinova, Maya; Zangrando, Marco; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Schulz, Joachim; Gumprecht, Lars; Chapman, Henry N.; Nelson, A. J.; Frank, Matthias

2011-01-01

We present a compact modular apparatus with a flexible design that will be operated at the DiProI beamline of the Fermi-Elettra free electron laser (FEL) for performing static and time-resolved coherent diffraction imaging experiments, taking advantage of the full coherence and variable polarization of the short seeded FEL pulses. The apparatus has been assembled and the potential of the experimental setup is demonstrated by commissioning tests with coherent synchrotron radiation. This multipurpose experimental station will be open to general users after installation at the Fermi-Elettra free electron laser in 2011.

Developing Phenomena Models from Experimental Data

DEFF Research Database (Denmark)

Kristensen, Niels Rode; Madsen, Henrik; Jørgensen, Sten Bay

2003-01-01

A systematic approach for developing phenomena models from experimental data is presented. The approach is based on integrated application of stochastic differential equation (SDE) modelling and multivariate nonparametric regression, and it is shown how these techniques can be used to uncover...... unknown functionality behind various phenomena in first engineering principles models using experimental data. The proposed modelling approach has significant application potential, e.g. for determining unknown reaction kinetics in both chemical and biological processes. To illustrate the performance...... of the approach, a case study is presented, which shows how an appropriate phenomena model for the growth rate of biomass in a fed-batch bioreactor can be inferred from data....

Developing Phenomena Models from Experimental Data

DEFF Research Database (Denmark)

A systematic approach for developing phenomena models from experimental data is presented. The approach is based on integrated application of stochastic differential equation (SDE) modelling and multivariate nonparametric regression, and it is shown how these techniques can be used to uncover...... unknown functionality behind various phenomena in first engineering principles models using experimental data. The proposed modelling approach has significant application potential, e.g. for determining unknown reaction kinetics in both chemical and biological processes. To illustrate the performance...... of the approach, a case study is presented, which shows how an appropriate phenomena model for the growth rate of biomass in a fed-batch bioreactor can be inferred from data....

Effects of ageing conditions on the precipitates evolution, chromium depletion and intergranular corrosion susceptibility of AISI 316L: experimental and modeling results

Energy Technology Data Exchange (ETDEWEB)

Sahlaoui, H.; Makhlouf, K.; Sidhom, H.; Philibert, J

2004-05-15

Chromium carbides and intermetallic phases which form in industrial AISI 316L stainless steel during ageing for up to 80 000 h between 550 and 650 deg. C were identified by combining transmission electron microscopy (TEM) thin foil imaging and electron diffraction and used to establish the time-temperature-precipitation (TTP) diagram. Following the precipitation phenomena, the chemical changes in the grain boundary region were determined by energy-dispersive X-ray microprobe analysis using a scanning transmission electron microscope (STEM). From the experimentally determined chromium profiles the chromium depleted zones were quantified. The interactions between carbide precipitation involving chromium depletion and intergranular corrosion (IGC) were clearly visible from superposition of TTP diagrams and time-temperature-sensitization (TTS) diagrams obtained from ASTM standardized tests. In addition, an experimental criterion to sensitization-desensitization phenomenon was established. Moreover, an analytical model has been developed in this study and successfully validated to predict the profiles of chromium depleted zones. This model coupled with the previously described criterion provides TTS diagrams in good agreement with experimental results.

Effect of self-interstitial diffusion anisotropy in electron-irradiated zirconium: A cluster dynamics modeling

International Nuclear Information System (INIS)

Christien, F.; Barbu, A.

2005-01-01

A model based on the cluster dynamics approach was proposed in [A. Hardouin Duparc, C. Moingeon, N. Smetniansky-de-Grande, A. Barbu, J. Nucl. Mater. 302 (2002) 143] to describe point defect agglomeration in metals under irradiation. This model is restricted to materials where point defect diffusion is isotropic and is thus not applicable to anisotropic metals such as zirconium. Following the approach proposed by Woo [C.H. Woo, J. Nucl. Mater. 159 (1988) 237], we extended in this work the model to the case where self-interstitial atoms (SIA) diffusion is anisotropic. The model was then applied to the loop microstructure evolution of a zirconium thin foil irradiated with electrons in a high-voltage microscope. First, the inputs were validated by comparing the numerical results with Hellio et al. experimental results [C. Hellio, C.H. de Novion, L. Boulanger, J. Nucl. Mater. 159 (1988) 368]. Further calculations were made to evidence the effect of the thin foil orientation on the dislocation loop microstructure under irradiation. The result is that it is possible to reproduce for certain orientations the 'unexpected' vacancy loop growth experimentally observed in electron-irradiated zirconium [M. Griffiths, M.H. Loretto, R.E. Sallmann, J. Nucl. Mater. 115 (1983) 313; J. Nucl. Mater. 115 (1983) 323; Philos. Mag. A 49 (1984) 613]. This effect is directly linked to SIA diffusion anisotropy

Antioxidant Capacity: Experimental Determination by EPR Spectroscopy and Mathematical Modeling.

Science.gov (United States)

Polak, Justyna; Bartoszek, Mariola; Chorążewski, Mirosław

2015-07-22

A new method of determining antioxidant capacity based on a mathematical model is presented in this paper. The model was fitted to 1000 data points of electron paramagnetic resonance (EPR) spectroscopy measurements of various food product samples such as tea, wine, juice, and herbs with Trolox equivalent antioxidant capacity (TEAC) values from 20 to 2000 μmol TE/100 mL. The proposed mathematical equation allows for a determination of TEAC of food products based on a single EPR spectroscopy measurement. The model was tested on the basis of 80 EPR spectroscopy measurements of herbs, tea, coffee, and juice samples. The proposed model works for both strong and weak antioxidants (TEAC values from 21 to 2347 μmol TE/100 mL). The determination coefficient between TEAC values obtained experimentally and TEAC values calculated with proposed mathematical equation was found to be R(2) = 0.98. Therefore, the proposed new method of TEAC determination based on a mathematical model is a good alternative to the standard EPR method due to its being fast, accurate, inexpensive, and simple to perform.

Experimental and theoretical studies on X-ray induced secondary electron yields in Ti and TiO2

International Nuclear Information System (INIS)

Iyasu, Takeshi; Tamura, Keiji; Shimizu, Ryuichi; Vlaicu, Mihai Aurel; Yoshikawa, Hideki

2006-01-01

Generation of X-ray induced secondary electrons in Ti and TiO 2 was studied from both experimental and theoretical approaches, using X-ray photoelectron spectroscopy (XPS) attached to a synchrotron radiation facility and Monte Carlo simulation, respectively. The experiment revealed that the yields of secondary electrons induced by X-rays (electrons/photon) at photon energies to 4950 and 5000eV for Ti and TiO 2 are δ Ti (4950eV)=0.002 and δ Ti (5000eV)=0.014 while those for TiO 2 are δ TiO 2 (4950eV)=0.003 and δ TiO 2 (5000eV)=0.018. A novel approach to obtain the escape depth of secondary electrons has been proposed and applied to Ti and TiO 2 . The approach agreed very well with the experimental data reported so far. The Monte Carlo simulation predicted; δ Ti * (4950eV)=0.002 and δ Ti * (5000eV)=0.011 while δ TiO 2 * (4950eV)=0.003 and δ TiO 2 * (5000eV)=0.015. An experimental examination on the contribution of X-ray induced secondary electrons to photocatalysis in TiO 2 has also been proposed

Experimental efforts at NIST towards one-electron ions in circular Rydberg states

International Nuclear Information System (INIS)

Tan, Joseph N; Guise, Nicholas D; Brewer, Samuel M

2011-01-01

Experimental effort is underway at NIST to enable tests of theory with one-electron ions synthesized in circular Rydberg states from captured bare nuclei. Problematic effects that limit the accuracy of predicted energy levels for low-lying states are vanishingly small for high-angular-momentum (high-L) states; in particular, the nuclear size correction for high-L states is completely negligible for any foreseeable improvement of measurement precision. As an initial step towards realizing such states, highly charged ions are extracted from the NIST electron beam ion trap (EBIT) and steered through the electrodes of a Penning trap. The goal is to capture bare nuclei in the Penning trap for experiments to make one-electron atoms in circular Rydberg states with dipole (E1) transitions in the optical domain accessible to a frequency comb.

A systematic multiscale modeling and experimental approach to protect grain boundaries in magnesium alloys from corrosion

Energy Technology Data Exchange (ETDEWEB)

Horstemeyer, Mark R. [Mississippi State Univ., Mississippi State, MS (United States); Chaudhuri, Santanu [Univ. of Illinois, Urbana-Champaign, IL (United States)

2015-09-30

A multiscale modeling Internal State Variable (ISV) constitutive model was developed that captures the fundamental structure-property relationships. The macroscale ISV model used lower length scale simulations (Butler-Volmer and Electronics Structures results) in order to inform the ISVs at the macroscale. The chemomechanical ISV model was calibrated and validated from experiments with magnesium (Mg) alloys that were investigated under corrosive environments coupled with experimental electrochemical studies. Because the ISV chemomechanical model is physically based, it can be used for other material systems to predict corrosion behavior. As such, others can use the chemomechanical model for analyzing corrosion effects on their designs.

Modeling of beam-target interaction during pulsed electron beam ablation of graphite: Case of melting

Energy Technology Data Exchange (ETDEWEB)

Ali, Muddassir, E-mail: mx1_ali@laurentian.ca; Henda, Redhouane

2017-02-28

Highlights: • Modeling of ablation stage induced during pulsed electron beam ablation (PEBA). • Thermal model to describe heating, melting and vaporization of a graphite target. • Model results show good accordance with reported data in the literature. - Abstract: A one-dimensional thermal model based on a two-stage heat conduction equation is employed to investigate the ablation of graphite target during nanosecond pulsed electron beam ablation. This comprehensive model accounts for the complex physical phenomena comprised of target heating, melting and vaporization upon irradiation with a polyenergetic electron beam. Melting and vaporization effects induced during ablation are taken into account by introducing moving phase boundaries. Phase transition induced during ablation is considered through the temperature dependent thermodynamic properties of graphite. The effect of electron beam efficiency, power density, and accelerating voltage on ablation is analyzed. For an electron beam operating at an accelerating voltage of 15 kV and efficiency of 0.6, the model findings show that the target surface temperature can reach up to 7500 K at the end of the pulse. The surface begins to melt within 25 ns from the pulse start. For the same process conditions, the estimated ablation depth and ablated mass per unit area are about 0.60 μm and 1.05 μg/mm{sup 2}, respectively. Model results indicate that ablation takes place primarily in the regime of normal vaporization from the surface. The results obtained at an accelerating voltage of 15 kV and efficiency factor of 0.6 are satisfactorily in good accordance with available experimental data in the literature.

Thermal expansion model for multiphase electronic packaging materials

International Nuclear Information System (INIS)

Allred, B.E.; Warren, W.E.

1991-01-01

Control of thermal expansion is often necessary in the design and selection of electronic packages. In some instances, it is desirable to have a coefficient of thermal expansion intermediate between values readily attainable with single or two phase materials. The addition of a third phase in the form of fillers, whiskers, or fibers can be used to attain intermediate expansions. To help design the thermal expansion of multiphase materials for specific applications, a closed form model has been developed that accurately predicts the effective elastic properties of isotropic filled materials and transversely isotropic lamina. Properties of filled matrix materials are used as inputs to the lamina model to obtain the composite elastic properties as a function of the volume fraction of each phase. Hybrid composites with two or more fiber types are easily handled with this model. This paper reports that results for glass, quartz, and Kevlar fibers with beta-eucryptite filled polymer matrices show good agreement with experimental results for X, Y, and Z thermal expansion coefficients

Preionization electron density measurement by collecting electric charge

International Nuclear Information System (INIS)

Giordano, G.; Letardi, T.

1988-01-01

A method using electron collection for preionization-electron number density measurements is presented. A cathode-potential drop model is used to describe the measurement principle. There is good agreement between the model and the experimental result

Experimental investigation and numerical modelling of positive corona discharge: ozone generation

Energy Technology Data Exchange (ETDEWEB)

Yanallah, K; Castellanos, A [Departamento de Electronica y Electromagnetismo, Universidad de Sevilla (Spain); Pontiga, F; Fernandez-Rueda, A [Departamento de FIsica Aplicada II, Universidad de Sevilla (Spain)

2009-03-21

The spatial distribution of the species generated in a wire-cylinder positive corona discharge in pure oxygen has been computed using a plasma chemistry model that includes the most significant reactions between electrons, ions, atoms and molecules. The plasma chemistry model is included in the continuity equations of each species, which are coupled with Poisson's equation for the electric field and the energy conservation equation for the gas temperature. The current-voltage characteristic measured in the experiments has been used as an input data to the numerical simulation. The numerical model is able to reproduce the basic structure of the positive corona discharge and highlights the importance of Joule heating on ozone generation. The average ozone density has been computed as a function of current intensity and compared with the experimental measurements of ozone concentration determined by UV absorption spectroscopy.

Experimental investigation and numerical modelling of positive corona discharge: ozone generation

International Nuclear Information System (INIS)

Yanallah, K; Castellanos, A; Pontiga, F; Fernandez-Rueda, A

2009-01-01

The spatial distribution of the species generated in a wire-cylinder positive corona discharge in pure oxygen has been computed using a plasma chemistry model that includes the most significant reactions between electrons, ions, atoms and molecules. The plasma chemistry model is included in the continuity equations of each species, which are coupled with Poisson's equation for the electric field and the energy conservation equation for the gas temperature. The current-voltage characteristic measured in the experiments has been used as an input data to the numerical simulation. The numerical model is able to reproduce the basic structure of the positive corona discharge and highlights the importance of Joule heating on ozone generation. The average ozone density has been computed as a function of current intensity and compared with the experimental measurements of ozone concentration determined by UV absorption spectroscopy.

Experimental investigation and numerical modelling of positive corona discharge: ozone generation

Science.gov (United States)

Yanallah, K; Pontiga, F; Fernández-Rueda, A; Castellanos, A

2009-03-01

The spatial distribution of the species generated in a wire-cylinder positive corona discharge in pure oxygen has been computed using a plasma chemistry model that includes the most significant reactions between electrons, ions, atoms and molecules. The plasma chemistry model is included in the continuity equations of each species, which are coupled with Poisson's equation for the electric field and the energy conservation equation for the gas temperature. The current-voltage characteristic measured in the experiments has been used as an input data to the numerical simulation. The numerical model is able to reproduce the basic structure of the positive corona discharge and highlights the importance of Joule heating on ozone generation. The average ozone density has been computed as a function of current intensity and compared with the experimental measurements of ozone concentration determined by UV absorption spectroscopy.

Experimental investigations and modeling of a loop thermosyphon for cooling with zero electrical consumption

International Nuclear Information System (INIS)

Chehade, Ali; Louahlia-Gualous, Hasna; Le Masson, Stéphane; Lépinasse, Eric

2015-01-01

This paper presents an analytical model for a thermosyphon loop developed for cooling air inside a telecommunication cabinet. The proposed model is based on the combination of thermal and hydraulic management of two-phase flow in the loop. Experimental tests on a closed thermosyphon loop are conducted with different working fluids that could be used for electronic cooling. Correlations for condensation and evaporation heat transfer in the thermosyphon loop are proposed. They are used in the model to calculate condenser and evaporator thermal resistances in order to predict the cabinet operating temperature, the loop's mass flow rate and pressure drops. Furthermore, various figures of merit proposed in the previous works are evaluated in order to be used for selection of the best loop's working fluid. The comparative studies show that the present model well predicts the experimental data. The mean deviation between the predictions of the theoretical model with the measurements for operating temperature is about 6%. Besides, the model is used to define an optimal liquid and vapor lines diameters and the effect of the ambient temperature on the fluid's mass flow rate and pressure drop. - Highlights: • Modeling of thermosyphon loop for cooling telecommunication cabinet. • The cooling system operates with zero electrical consumption. • The new correlations are proposed for condensation and evaporation heat transfer. • FOM equation is defined for selecting the best working fluid. • The proposed model well predicts the experimental data and operating temperature

Modelling the line shape of very low energy peaks of positron beam induced secondary electrons measured using a time of flight spectrometer

International Nuclear Information System (INIS)

Fairchild, A J; Chirayath, V A; Gladen, R W; Chrysler, M D; Koymen, A R; Weiss, A H

2017-01-01

In this paper, we present results of numerical modelling of the University of Texas at Arlington’s time of flight positron annihilation induced Auger electron spectrometer (UTA TOF-PAES) using SIMION® 8.1 Ion and Electron Optics Simulator. The time of flight (TOF) spectrometer measures the energy of electrons emitted from the surface of a sample as a result of the interaction of low energy positrons with the sample surface. We have used SIMION® 8.1 to calculate the times of flight spectra of electrons leaving the sample surface with energies and angles dispersed according to distribution functions chosen to model the positron induced electron emission process and have thus obtained an estimate of the true electron energy distribution. The simulated TOF distribution was convolved with a Gaussian timing resolution function and compared to the experimental distribution. The broadening observed in the simulated TOF spectra was found to be consistent with that observed in the experimental secondary electron spectra of Cu generated as a result of positrons incident with energy 1.5 eV to 901 eV, when a timing resolution of 2.3 ns was assumed. (paper)

Modeling and Experimentation of New Thermoelectric Cooler–Thermoelectric Generator Module

Directory of Open Access Journals (Sweden)

Khaled Teffah

2018-03-01

Full Text Available In this work, a modeling and experimental study of a new thermoelectric cooler–thermoelectric generator (TEC-TEG module is investigated. The studied module is composed of TEC, TEG and total system heatsink, all connected thermally in series. An input voltage (1–5 V passes through the TEC where the electrons by means of Peltier effect entrain the heat from the upper side of the module to the lower one creating temperature difference; TEG plays the role of a partial heatsink for the TEC by transferring this waste heat to the total system heatsink and converting an amount of this heat into electricity by a phenomenon called Seebeck effect, of the thermoelectric modules. The performance of the TEG as partial heatsink of TEC at different input voltages is demonstrated theoretically using the modeling software COMSOL Multiphysics. Moreover, the experiment validates the simulation result which smooths the path for a new manufacturing thermoelectric cascade model for the cooling and the immediate electric power generation.

Experimental study for angular distribution of the hot electrons generated by femtosecond laser interaction with solid targets

International Nuclear Information System (INIS)

Cai, D.F.; Gu, Y.Q.; Zheng, Z.J.; Wen, T.S.; Chunyu, S.T.; Wang, Z.B.; Yang, X.D.

2003-01-01

The experimental results of angular distribution of hot electrons in the interaction of a 60 fs, 125 mJ, 800 nm, ∼10 17 W cm -2 laser pulse with Al targets are reported. Three obvious peaks of hot electrons emission have been observed, as there is a weak normal component of the laser electric field. These emission peaks are located in the directions of the specular reflection of the laser, the target normal, and the backreflection of the laser, respectively. In the case of the P-polarized laser pulse, which has a strong normal component of the laser electric field, the peak in the backreflection of the laser disappeared, and only two obvious peaks of hot electron emissions existed. It shows that the different directions of hot electrons emission are dominated by different absorption or acceleration mechanisms. The experimental result of the hot electrons energy spectrum at the target normal shows that the effective temperature of hot electrons is about 190 keV, which is consistent with a scaling law of the resonance absorption

The electrical resistivity of rough thin films: A model based on electron reflection at discrete step edges

Science.gov (United States)

Zhou, Tianji; Zheng, Pengyuan; Pandey, Sumeet C.; Sundararaman, Ravishankar; Gall, Daniel

2018-04-01

The effect of the surface roughness on the electrical resistivity of metallic thin films is described by electron reflection at discrete step edges. A Landauer formalism for incoherent scattering leads to a parameter-free expression for the resistivity contribution from surface mound-valley undulations that is additive to the resistivity associated with bulk and surface scattering. In the classical limit where the electron reflection probability matches the ratio of the step height h divided by the film thickness d, the additional resistivity Δρ = √{3 /2 } /(g0d) × ω/ξ, where g0 is the specific ballistic conductance and ω/ξ is the ratio of the root-mean-square surface roughness divided by the lateral correlation length of the surface morphology. First-principles non-equilibrium Green's function density functional theory transport simulations on 1-nm-thick Cu(001) layers validate the model, confirming that the electron reflection probability is equal to h/d and that the incoherent formalism matches the coherent scattering simulations for surface step separations ≥2 nm. Experimental confirmation is done using 4.5-52 nm thick epitaxial W(001) layers, where ω = 0.25-1.07 nm and ξ = 10.5-21.9 nm are varied by in situ annealing. Electron transport measurements at 77 and 295 K indicate a linear relationship between Δρ and ω/(ξd), confirming the model predictions. The model suggests a stronger resistivity size effect than predictions of existing models by Fuchs [Math. Proc. Cambridge Philos. Soc. 34, 100 (1938)], Sondheimer [Adv. Phys. 1, 1 (1952)], Rossnagel and Kuan [J. Vac. Sci. Technol., B 22, 240 (2004)], or Namba [Jpn. J. Appl. Phys., Part 1 9, 1326 (1970)]. It provides a quantitative explanation for the empirical parameters in these models and may explain the recently reported deviations of experimental resistivity values from these models.

Plasma electron losses in a multidipole plasma

International Nuclear Information System (INIS)

Haworth, M.D.

1983-01-01

The magnitude of the plasma electron cusp losses in a multidipole plasma device is determined by using a plasma electron heating technique. This method consists of suddenly generating approximately monoenergetic test electrons inside the multidipole plasma, which is in a steady-state equilibrium prior to the introduction of the test electrons. The Coulomb collisions between the test electrons and the plasma electrons result in heating the plasma electrons. The experimentally measured time evolution of the plasma electron temperature is compared with that predicted by a kinetic-theory model which calculates the time evolution of the test electron and the plasma electron distribution functions. The analytical solution of the plasma electron heating rate when the test electrons are first introduced into the plasma predicts that there is no dependence on ion mass. Experimental results in helium, neon, argon, and krypton multidipole plasmas confirm this prediction. The time-evolved solution of the kinetic equations must be solved numerically, and these results (when coupled with the experimental heating results) show that the plasma electron cusp-loss width is on the order of an electron Larmor radius

Modeling microwave/electron-cloud interaction

International Nuclear Information System (INIS)

Mattes, M; Sorolla, E; Zimmermann, F

2013-01-01

Starting from the separate codes BI-RME and ECLOUD or PyECLOUD, we are developing a novel joint simulation tool, which models the combined effect of a charged particle beam and of microwaves on an electron cloud. Possible applications include the degradation of microwave transmission in telecommunication satellites by electron clouds; the microwave-transmission techniques being used in particle accelerators for the purpose of electroncloud diagnostics; the microwave emission by the electron cloud itself in the presence of a magnetic field; and the possible suppression of electron-cloud formation in an accelerator by injecting microwaves of suitable amplitude and frequency. A few early simulation results are presented. (author)

Phase-Space Models of Solitary Electron Hoies

DEFF Research Database (Denmark)

Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans

1985-01-01

Two different phase-space models of solitary electron holes are investigated and compared with results from computer simulations of an actual laboratory experiment, carried out in a strongly magnetized, cylindrical plasma column. In the two models, the velocity distribution of the electrons...

Molecular modeling of interactions in electronic nose sensors for environmental monitoring

Science.gov (United States)

Shevade, A. V.; Ryan, M. A.; Homer, M. L.; Manfreda, A. M.; Yen, S. -P. S.; Zhou, H.; Manatt, K.

2002-01-01

We report a study aimed at understanding analyte interactions with sensors made from polymer-carbon black composite films. The sensors are used in an Electronic Nose (ENose) which is used for monitoring the breathing air quality in human habitats. The model mimics the experimental conditions of the composite film deposition and formation and was developed using molecular modeling and simulation tools. The Dreiding 2.21 Force Field was used for the polymer and analyte molecules while graphite parameters were assigned to the carbon black atoms. The polymer considered for this work is methyl vinyl ether / maleic acid copolymer. The target analytes include both inorganic (NH3) and organic (methanol) types of compound. Results indicate different composite-analyte interaction behavior.

PEMFC modeling and experimental validation

Energy Technology Data Exchange (ETDEWEB)

Vargas, J.V.C. [Federal University of Parana (UFPR), Curitiba, PR (Brazil). Dept. of Mechanical Engineering], E-mail: jvargas@demec.ufpr.br; Ordonez, J.C.; Martins, L.S. [Florida State University, Tallahassee, FL (United States). Center for Advanced Power Systems], Emails: ordonez@caps.fsu.edu, martins@caps.fsu.edu

2009-07-01

In this paper, a simplified and comprehensive PEMFC mathematical model introduced in previous studies is experimentally validated. Numerical results are obtained for an existing set of commercial unit PEM fuel cells. The model accounts for pressure drops in the gas channels, and for temperature gradients with respect to space in the flow direction, that are investigated by direct infrared imaging, showing that even at low current operation such gradients are present in fuel cell operation, and therefore should be considered by a PEMFC model, since large coolant flow rates are limited due to induced high pressure drops in the cooling channels. The computed polarization and power curves are directly compared to the experimentally measured ones with good qualitative and quantitative agreement. The combination of accuracy and low computational time allow for the future utilization of the model as a reliable tool for PEMFC simulation, control, design and optimization purposes. (author)

Experimental investigations of interaction of supercritical electron beams with plasma

International Nuclear Information System (INIS)

Chupikov, P.T.; Medvedev, D.V.; Onishchenko, I.N.; Panasenko, B.D.; Faehl, R.J.

2002-01-01

The first section of the collective ions acceleration based on simultaneous temporal and spatial modulation of relativistic electron beam (REB) was studied experimentally. The virtual cathode was originated in the electrodynamic structure consisting of two tubes with different diameters (jump of electrodynamics) by REB, produced in magnetically insulated diode. At plasma assistance the low-frequency oscillations of REB current and the low-frequency microwave radiation were obtained due to the virtual cathode periodical relaxation in the processes of charge compensation by ionized residual gas

Modeling Incoherent Electron Cloud Effects

International Nuclear Information System (INIS)

Vay, Jean-Luc; Benedetto, E.; Fischer, W.; Franchetti, G.; Ohmi, K.; Schulte, D.; Sonnad, K.; Tomas, R.; Vay, J.-L.; Zimmermann, F.; Rumolo, G.; Pivi, M.; Raubenheimer, T.

2007-01-01

Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and present results for a toy model of the SPS. In addition, we present evidence that for positron beams the interplay of incoherent electron-cloud effects and synchrotron radiation can lead to a significant increase in vertical equilibrium emittance. The magnitude of a few incoherent e+e- scattering processes is also estimated. Options for future code development are reviewed

Slow electron contribution to inelastic reflection anisotropy

International Nuclear Information System (INIS)

Podsvirov, O.A.; Kuznetsov, Yu.A.

1980-01-01

Investigated is electron contribution with low energy (up to 1 keV) to the anisotropy of electron inelastic reflection (IRE) from silicon monocrystal (111) within 12-50 keV energy range of primary electrons. Experimental data on IRE anisotropy are presented: delay curves for silicon monocrystal, permitting to separate electrons with the energy up to 1 keV, dependences of IRE anisotropy on the energy of primary electrons for the systems - monocrystalline silicon-amorphous silicon film and delay curves for such systems (film thickness varies from 20 to 2000 A). Suggested is a phenomenologic model, permitting to take into account the contribution of slow electrons to IRE anisotropy: it is supposed, that three groups of electrons take part in the formation of the latter: elastic and inelastic reflected electrons, slow electrons, excited by primary electrons and slow electrons, generated by the reverse flow of the scattered electrons. Contribution of electrons, different by origin, to IRE anisotropy is evaluated in accordance with the experimental data on the basis of this model. It is stated, that slow electrons constitute approximately one half of the IRE anisotropy value, the contribution of both groups of slow electrons being approximately equal

Experimental investigation of the generation of harmonic photons from the interaction of free electrons with intense laser radiation

International Nuclear Information System (INIS)

Englert, T.J.

1983-01-01

An experimental investigation of the generation of second harmonic photons through the interaction of free electrons with an intense laser beam has been performed. Second harmonic photons with a wavelength of 530nm generated from the interaction of free electrons with 1060nm photons from a neodymium-glass laser are implied by observing Doppler shifted photons with wavelengths of 490nm and 507nm. The observed photon wavelengths results from a Doppler shift of the laser photon wavelengths as viewed in the rest frame of the electrons combined with a Doppler shift of the second harmonic photons emitted from 1600eV and 500eV electrons. Comparison of experimental results with those predicted by cross sections, derived using classical and quantum electrodynamics, shows reasonable agreement with both theories. Although second harmonic photons are created, the dynamics of second harmonic photon generation (accelerated electron motion due to the electromagnetic field or actual two-photon interaction with the electron) cannot be resolved without further experiment

FTL Quantum Models of the Photon and the Electron

International Nuclear Information System (INIS)

Gauthier, Richard F.

2007-01-01

A photon is modeled by an uncharged superluminal quantum moving at 1.414c along an open 45-degree helical trajectory with radius R = λ/2π (where λ is the helical pitch or wavelength). A mostly superluminal spatial model of an electron is composed of a charged pointlike quantum circulating at an extremely high frequency ( 2.5 x 1020 hz) in a closed, double-looped hehcal trajectory whose helical pitch is one Compton wavelength h/mc. The quantum has energy and momentum but not rest mass, so its speed is not limited by c. sThe quantum's speed is superluminal 57% of the time and subluminal 43% of the time, passing through c twice in each trajectory cycle. The quantum's maximum speed in the electron's rest frame is 2.515c and its minimum speed is .707c. The electron model's helical trajectory parameters are selected to produce the electron's spin (ℎ/2π)/2 and approximate (without small QED corrections) magnetic moment e(ℎ/2π)/2m (the Bohr magneton μB) as well as its Dirac equation-related 'jittery motion' angular frequency 2mc2/(ℎ/2π), amplitude (ℎ/2π)/2mc and internal speed c. The two possible helicities of the electron model correspond to the electron and the positron. With these models, an electron is like a closed circulating photon. The electron's inertia is proposed to be related to the electron model's circulating internal Compton momentum mc. The internal superluminalily of the photon model, the internal superluminahty/subluminality of the electron model, and the proposed approach to the electron's inertia as ''momentum at rest'' within the electron, could be relevant to possible mechanisms of superluminal communication and transportation

Experimental realization of millimeter-wave amplification by a sheet beam free electron laser

International Nuclear Information System (INIS)

Zhang, Z.; Destler, W.W.; Granatstein, V.L.; Antonsen, T.M. Jr.; Levush, B.; Rodgers, J.; Cheng, S.

1994-01-01

We report an observation of millimeter-wave (94 GHz) amplification in a sheet beam, short period, planar wiggler, free electron laser amplifier. The observed gain is about 5 dB for a 530 keV, 4 A beam through a 54 cm wiggler. Wave energy absorption was also observed when the beam energy is off-resonance. Experimental results are in good agreement with numerical simulation. This amplifier configuration has potential for producing equally high output power but at relatively low voltage compared with longer period free electron lasers

Experimental Electron Density Distribution in Two Cocrystals of Betaines with p-Hydroxybenzoic Acid

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Agata Owczarzak

2018-03-01

Full Text Available Experimental determination of electron density distribution in crystals by means of high-resolution X-ray diffraction allows, among others, for studying the details of intra- and inter-molecular interactions. In case of co-crystals, this method may help in finding the conditions of creating such species. The results of such analysis for two co-crystals containing betaines, namely trigonelline (TRG: nicotinic acid N-methylbetaine, IUPAC name: 1-methylpyridinium-3-carboxylate and N-methylpiperidine betaine (MPB: 1-methylpiperidinium-1-yl-carboxylate with p-hydroxybenzoic acid (HBA are reported. TRG-HBA crystallizes as a hydrate. For both of the co-crystals, high-quality diffraction data were collected up to sinθ/λ = 1.13 Å−1. Hansen-Coppens multipolar model was then applied for modelling the electron density distribution and Atoms-In-Molecules approach was used for detailed analysis of interactions in crystals. A number of intermolecular interactions was identified, ranging from strong O-H···O hydrogen bonds through C-H···O to C-H···π and π···π interactions. Correlations between the geometrical characteristics of the contacts and the features of their critical points were analyzed in detail. Atomic charges show that in zwitterionic species there are regions of opposite charges, rather than charges that are localized on certain atoms. In case of MPB-HBA, a significant charge transfer between the components of co-crystal (0.5 e was found, as opposed to TRG-HBA, where all of the components are almost neutral.

Peculiarities of designing Holistic Electronic Government Services Integration Model

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Tadas Limba

2011-12-01

Full Text Available Purpos– the aim ok this paper is to develop a Holistic Electronic Government Services Integration Model which could ensure the efficient integration of electronic government services in the local self-government level.Methodolog– the following analyses have been carried out in thirkpaper: theoretical-systematic; normative and conceptual comparative analysis of the researcha A method of modeling has also been applied.Finding– the scientific work analyzes the improvement opportunities of the models of electronic government services and their application alternatives in Lithuanian municipalities. The newly developed model of electronic government services that has been designed basng on the principle of integrating online expert consultation is primarily targeted at improvement of inside processes’ changes of an organization. Practicing the application of that model in the local self-government level starting with improvement of inside processes of an organization should help adapt more accurately and efficiently to the changing needs of the society while providing electronic government services, thus establishing a higher public value.Practical implication– the practical novelty of work is reflected not only through the integration opportunities’ assessment of the principle of online expert consultation services into the theoretical models of electronic government services that have already been developed by the scientists, but also on the basis of this principle there has been created a “Holistic Electronic Government Services Integration Model” in accordance with “E-Diamond” model basis and its practical application realization with the design of “The project of implementing the principle of online expert consultation on the model of electronic government services” for the future investigations.Originalit– the systematic, comparative analysis of the models of electronic government services carried out in the scientific

Excess electrons in methanol clusters: Beyond the one-electron picture

Science.gov (United States)

Pohl, Gábor; Mones, Letif; Turi, László

2016-10-01

We performed a series of comparative quantum chemical calculations on various size negatively charged methanol clusters, ("separators=" CH 3 OH ) n - . The clusters are examined in their optimized geometries (n = 2-4), and in geometries taken from mixed quantum-classical molecular dynamics simulations at finite temperature (n = 2-128). These latter structures model potential electron binding sites in methanol clusters and in bulk methanol. In particular, we compute the vertical detachment energy (VDE) of an excess electron from increasing size methanol cluster anions using quantum chemical computations at various levels of theory including a one-electron pseudopotential model, several density functional theory (DFT) based methods, MP2 and coupled-cluster CCSD(T) calculations. The results suggest that at least four methanol molecules are needed to bind an excess electron on a hydrogen bonded methanol chain in a dipole bound state. Larger methanol clusters are able to form stronger interactions with an excess electron. The two simulated excess electron binding motifs in methanol clusters, interior and surface states, correlate well with distinct, experimentally found VDE tendencies with size. Interior states in a solvent cavity are stabilized significantly stronger than electron states on cluster surfaces. Although we find that all the examined quantum chemistry methods more or less overestimate the strength of the experimental excess electron stabilization, MP2, LC-BLYP, and BHandHLYP methods with diffuse basis sets provide a significantly better estimate of the VDE than traditional DFT methods (BLYP, B3LYP, X3LYP, PBE0). A comparison to the better performing many electron methods indicates that the examined one-electron pseudopotential can be reasonably used in simulations for systems of larger size.

Model Comparison for Electron Thermal Transport

Science.gov (United States)

Moses, Gregory; Chenhall, Jeffrey; Cao, Duc; Delettrez, Jacques

2015-11-01

Four electron thermal transport models are compared for their ability to accurately and efficiently model non-local behavior in ICF simulations. Goncharov's transport model has accurately predicted shock timing in implosion simulations but is computationally slow and limited to 1D. The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. uses multigroup diffusion to speed up the calculation. Chenhall has expanded upon the iSNB diffusion model to a higher order simplified P3 approximation and a Monte Carlo transport model, to bridge the gap between the iSNB and Goncharov models while maintaining computational efficiency. Comparisons of the above models for several test problems will be presented. This work was supported by Sandia National Laboratory - Albuquerque and the University of Rochester Laboratory for Laser Energetics.

Projectile electron loss in collisions of light charged ions with helium

International Nuclear Information System (INIS)

Yin Yong-Zhi; Chen Xi-Meng; Wang Yun

2014-01-01

We investigate the single-electron loss processes of light charged ions (Li 1+,2+ , C 2+,3+,5+ , and O 2+,3+ ) in collisions with helium. To better understand the experimental results, we propose a theoretical model to calculate the cross section of projectile electron loss. In this model, an ionization radius of the incident ion was defined under the classical over-barrier model, and we developed ''strings'' to explain the processes of projectile electron loss, which is similar with the molecular over-barrier model. Theoretical calculations are in good agreement with the experimental results for the cross section of single-electron loss and the ratio of double-to-single ionization of helium associated with one-electron loss. (atomic and molecular physics)

Experimental Search for a Heavy Electron

Science.gov (United States)

Boley, C. D.; Elias, J. E.; Friedman, J. I.; Hartmann, G. C.; Kendall, H. W.; Kirk, P.N.; Sogard, M. R.; Van Speybroeck, L. P.; de Pagter, J. K.

1967-09-01

A search for a heavy electron of the type considered by Low and Blackmon has been made by studying the inelastic scattering of 5 BeV electrons from hydrogen. The search was made over a range of values of the mass of the heavy electron from 100 t0 1300 MeV. No evidence for such a particle was observed. Upper limits on the production cross sections were determined and employed to deducelimits on the values of the electron-photon-heavy electron coupling constant in Low and Blackmon=s theory.

New experimental model for training in videosurgery Novo modelo experimental para treinamento em videocirurgia

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Danilo Malta Batista

2012-10-01

Full Text Available PURPOSE: To develop a new experimental model of lower cost for training in videosurgery. METHODS: This project was performed at the Nucleus of Experimental Surgery of the Bahiana School of Medicine and Public Health, based on previous models described in the literature and under the supervision of the full professor of Operative Technique and Experimental Surgery II. It was made a model cube-shaped, made of wood, with holes distributed in various locations, rubber stoppers for the holes and lined externally with carpet, and internally with laminate. RESULTS: The new experimental model is of low cost and reproduces quite faithfully several videosurgical procedures. CONCLUSION: Medical schools interested in the subject may adopt the new model for training in videosurgery without the need of high costs for making and using these models.OBJETIVO: Desenvolver um novo modelo experimental de baixo custo para treinamento em videocirurgia MÉTODOS: Este projeto foi conduzido no Núcleo de Cirurgia Experimental da Escola Bahiana de Medicina e Saúde Pública, baseado em modelos prévios descritos na literatura e sob a supervisão do professor titular de Técnica Operatória e Cirurgia Experimental II. Foi feito um modelo em formato de cubo, de madeira, com furos distribuídos em vários locais, tampas de borracha para os orifícios e forrado externamente com carpete e internamente com laminado. RESULTADOS: O novo modelo experimental desenvolvido é de baixo custo e reproduz de forma bastante fiel diversos procedimentos videocirúrgicos. CONCLUSÃO: Faculdades médicas interessadas no tema poderão adotar o novo modelo para o treinamento em videocirurgia sem que sejam necessários gastos elevados para a confecção e o uso desses modelos.

Lessons on electronic decoherence in molecules from exact modeling

Science.gov (United States)

Hu, Wenxiang; Gu, Bing; Franco, Ignacio

2018-04-01

Electronic decoherence processes in molecules and materials are usually thought and modeled via schemes for the system-bath evolution in which the bath is treated either implicitly or approximately. Here we present computations of the electronic decoherence dynamics of a model many-body molecular system described by the Su-Schrieffer-Heeger Hamiltonian with Hubbard electron-electron interactions using an exact method in which both electronic and nuclear degrees of freedom are taken into account explicitly and fully quantum mechanically. To represent the electron-nuclear Hamiltonian in matrix form and propagate the dynamics, the computations employ the Jordan-Wigner transformation for the fermionic creation/annihilation operators and the discrete variable representation for the nuclear operators. The simulations offer a standard for electronic decoherence that can be used to test approximations. They also provide a useful platform to answer fundamental questions about electronic decoherence that cannot be addressed through approximate or implicit schemes. Specifically, through simulations, we isolate basic mechanisms for electronic coherence loss and demonstrate that electronic decoherence is possible even for one-dimensional nuclear bath. Furthermore, we show that (i) decreasing the mass of the bath generally leads to faster electronic decoherence; (ii) electron-electron interactions strongly affect the electronic decoherence when the electron-nuclear dynamics is not pure-dephasing; (iii) classical bath models with initial conditions sampled from the Wigner distribution accurately capture the short-time electronic decoherence dynamics; (iv) model separable initial superpositions often used to understand decoherence after photoexcitation are only relevant in experiments that employ delta-like laser pulses to initiate the dynamics. These insights can be employed to interpret and properly model coherence phenomena in molecules.

Model based design of electronic throttle control

Science.gov (United States)

Cherian, Fenin; Ranjan, Ashish; Bhowmick, Pathikrit; Rammohan, A.

2017-11-01

With the advent of torque based Engine Management Systems, the precise control and robust performance of the throttle body becomes a key factor in the overall performance of the vehicle. Electronic Throttle Control provides benefits such as improved air-fuel ratio for improving the vehicle performance and lower exhausts emissions to meet the stringent emission norms. Modern vehicles facilitate various features such as Cruise Control, Traction Control, Electronic Stability Program and Pre-crash systems. These systems require control over engine power without driver intervention, which is not possible with conventional mechanical throttle system. Thus these systems are integrated to function with the electronic throttle control. However, due to inherent non-linearities in the throttle body, the control becomes a difficult task. In order to eliminate the influence of this hysteresis at the initial operation of the butterfly valve, a control to compensate the shortage must be added to the duty required for starting throttle operation when the initial operation is detected. Therefore, a lot of work is being done in this field to incorporate the various nonlinearities to achieve robust control. In our present work, the ETB was tested to verify the working of the system. Calibration of the TPS sensors was carried out in order to acquire accurate throttle opening angle. The response of the calibrated system was then plotted against a step input signal. A linear model of the ETB was prepared using Simulink and its response was compared with the experimental data to find out the initial deviation of the model from the actual system. To reduce this deviation, non-linearities from existing literature were introduced to the system and a response analysis was performed to check the deviation from the actual system. Based on this investigation, an introduction of a new nonlinearity parameter can be used in future to reduce the deviation further making the control of the ETB more

CALCULATION-EXPERIMENTAL METHOD OF RESEARCH IN A METALLIC CONDUCTOR WITH THE PULSE CURRENT OF ELECTRONIC WAVEPACKAGES AND DE BROGLIE ELECTRONIC HALF-WAVES

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M. I. Baranov

2016-12-01

Full Text Available Purpose. Development of calculation-experimental method for a discovery and study of electronic wavepackages (EWP and of de Broglie electronic half-waves in a metallic conductor with the pulse axial-flow current of high density. Methodology. Theoretical bases of the electrical engineering, bases of quantum physics, electrophysics bases of technique of high voltage and large pulsecurrents, and also bases of technique of measuring of permanent and variable electric value. Results. On the basis of generalization of results of research of features of the longitudinal wave periodic distributing of negatively charged transmitters of electric current of conductivity in the thin round continuous zincked steel wire offered and approved in the conditions of high-voltage laboratory method for a discovery and direct determination in him of geometrical parameters of «hot» and «cold» longitudinal areas quantized periodic longitudinal EWP and accordingly the mediated determination of values of the quantized lengths formative their de Broglie electronic half-waves. It is shown that results of close quantum mechanical calculations of EWP and quantized lengths λenz/2 of longitudinal de Broglie half-waves for the probed wire long l0 well comport with the results of the executed high temperature experiments on the powerful high-voltage generator of homopolar large pulse current of millisecond duration. Originality. First calculation-experimental a way the important for the theory of electricity fact of existence is set in a round metallic explorer with the impulsive axial-flow current of the quantized coherent de Broglie electronic half-waves, amplitudes of which at the quantum number of n=1,3,9 correspond the middles of «hot» longitudinal areas of EWP. Calculation quantum mechanical correlation of type of λenz/2=l0/n got experimental confirmation, in obedience to which on length of l0 conductor the integer of quantized electronic half-waves is always laid

Path-separated electron interferometry in a scanning transmission electron microscope

Science.gov (United States)

Yasin, Fehmi S.; Harvey, Tyler R.; Chess, Jordan J.; Pierce, Jordan S.; McMorran, Benjamin J.

2018-05-01

We report a path-separated electron interferometer within a scanning transmission electron microscope. In this setup, we use a nanofabricated grating as an amplitude-division beamsplitter to prepare multiple spatially separated, coherent electron probe beams. We achieve path separations of 30 nm. We pass the  +1 diffraction order probe through amorphous carbon while passing the 0th and  ‑1 orders through vacuum. The probes are then made to interfere via imaging optics, and we observe an interference pattern at the CCD detector with up to 39.7% fringe visibility. We show preliminary experimental results in which the interference pattern was recorded during a 1D scan of the diffracted probes across a test phase object. These results qualitatively agree with a modeled interference predicted by an independent measurement of the specimen thickness. This experimental design can potentially be applied to phase contrast imaging and fundamental physics experiments, such as an exploration of electron wave packet coherence length.

Multidimensional Quantum Mechanical Modeling of Electron Transfer and Electronic Coherence in Plant Cryptochromes: The Role of Initial Bath Conditions.

Science.gov (United States)

Mendive-Tapia, David; Mangaud, Etienne; Firmino, Thiago; de la Lande, Aurélien; Desouter-Lecomte, Michèle; Meyer, Hans-Dieter; Gatti, Fabien

2018-01-11

A multidimensional quantum mechanical protocol is used to describe the photoinduced electron transfer and electronic coherence in plant cryptochromes without any semiempirical, e.g., experimentally obtained, parameters. Starting from a two-level spin-boson Hamiltonian we look at the effect that the initial photoinduced nuclear bath distribution has on an intermediate step of this biological electron transfer cascade for two idealized cases. The first assumes a slow equilibration of the nuclear bath with respect to the previous electron transfer step that leads to an ultrafast decay with little temperature dependence; while the second assumes a prior fast bath equilibration on the donor potential energy surface leading to a much slower decay, which contrarily displays a high temperature dependence and a better agreement with previous theoretical and experimental results. Beyond Marcus and semiclassical pictures these results unravel the strong impact that the presence or not of equilibrium initial conditions has on the electronic population and coherence dynamics at the quantum dynamics level in this and conceivably in other biological electron transfer cascades.

Experimental study of single-electron loss by Ar{sup +} ions in rare-gas atoms

Energy Technology Data Exchange (ETDEWEB)

Reyes, P.G. [Facultad de Ciencias, UNAM, Coyoacan (Mexico); Castillo, F. [Instituto de Ciencias Nucleares, UNAM, Coyoacan (Mexico); Martinez, H. [Centro de Ciencias Fisicas, UNAM, Cuernavaca, Morelos (Mexico)]. E-mail: hm@fis.unam.mx

2001-04-28

Absolute differential and total cross sections for single-electron loss were measured for Ar{sup +} ions on rare-gas atoms in the laboratory energy range of 1.5 to 5.0 keV. The electron loss cross sections for all the targets studied are found to be in the order of magnitude between 10{sup -19} and 10{sup -22} cm{sup 2}, and show a monotonically increasing behaviour as a function of the incident energy. The behaviour of the total single-electron loss cross sections with the atomic target number, Z{sub t}, shows different dependences as the collision energy increases. In all cases the present results display experimental evidence of saturation in the single-electron loss cross section as the atomic number of the target increases. (author)

Angle selective backscattered electron contrast in the low-voltage scanning electron microscope: Simulation and experiment for polymers

Energy Technology Data Exchange (ETDEWEB)

Wan, Q., E-mail: qwan2@sheffield.ac.uk [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Masters, R.C. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Lidzey, D. [Department of Physics and Astronomy, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Abrams, K.J. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Dapor, M. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT-FBK) and Trento Institute for Fundamental Physics and Applications (TIFPA-INFN), via Sommarive 18, I-38123 Trento (Italy); Plenderleith, R.A. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Rimmer, S. [Department of Chemistry, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Claeyssens, F.; Rodenburg, C. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom)

2016-12-15

Recently developed detectors can deliver high resolution and high contrast images of nanostructured carbon based materials in low voltage scanning electron microscopes (LVSEM) with beam deceleration. Monte Carlo Simulations are also used to predict under which exact imaging conditions purely compositional contrast can be obtained and optimised. This allows the prediction of the electron signal intensity in angle selective conditions for back-scattered electron (BSE) imaging in LVSEM and compares it to experimental signals. Angle selective detection with a concentric back scattered (CBS) detector is considered in the model in the absence and presence of a deceleration field, respectively. The validity of the model prediction for both cases was tested experimentally for amorphous C and Cu and applied to complex nanostructured carbon based materials, namely a Poly(N-isopropylacrylamide)/Poly(ethylene glycol) Diacrylate (PNIPAM/PEGDA) semi-interpenetration network (IPN) and a Poly(3-hexylthiophene-2,5-diyl) (P3HT) film, to map nano-scale composition and crystallinity distribution by avoiding experimental imaging conditions that lead to a mixed topographical and compositional contrast - Highlights: • An optimised model for nano-scale analysis of beam sensitive materials by LVSEM. • Simulation and separation of composition and topography in a CBS detector. • Selective angle backscattered electron collection for mapping of polymers.

Angle selective backscattered electron contrast in the low-voltage scanning electron microscope: Simulation and experiment for polymers

International Nuclear Information System (INIS)

Wan, Q.; Masters, R.C.; Lidzey, D.; Abrams, K.J.; Dapor, M.; Plenderleith, R.A.; Rimmer, S.; Claeyssens, F.; Rodenburg, C.

2016-01-01

Recently developed detectors can deliver high resolution and high contrast images of nanostructured carbon based materials in low voltage scanning electron microscopes (LVSEM) with beam deceleration. Monte Carlo Simulations are also used to predict under which exact imaging conditions purely compositional contrast can be obtained and optimised. This allows the prediction of the electron signal intensity in angle selective conditions for back-scattered electron (BSE) imaging in LVSEM and compares it to experimental signals. Angle selective detection with a concentric back scattered (CBS) detector is considered in the model in the absence and presence of a deceleration field, respectively. The validity of the model prediction for both cases was tested experimentally for amorphous C and Cu and applied to complex nanostructured carbon based materials, namely a Poly(N-isopropylacrylamide)/Poly(ethylene glycol) Diacrylate (PNIPAM/PEGDA) semi-interpenetration network (IPN) and a Poly(3-hexylthiophene-2,5-diyl) (P3HT) film, to map nano-scale composition and crystallinity distribution by avoiding experimental imaging conditions that lead to a mixed topographical and compositional contrast - Highlights: • An optimised model for nano-scale analysis of beam sensitive materials by LVSEM. • Simulation and separation of composition and topography in a CBS detector. • Selective angle backscattered electron collection for mapping of polymers.

Stochastic model of the spinning electron

International Nuclear Information System (INIS)

Simaciu, I.; Borsos, Z.

2002-01-01

In Stochastic Electrodynamics (SED) it is demonstrated that electrostatic interaction is the result of the scattering of the Classical Zero-Point Field (CZPF) background by the charged particles. In such models, the electron is modelled as a two-dimensional oscillator, which interacts with the electric component of the CZPF background. The electron with spin is not only an electric monopole but also a magnetic dipole. The interaction of the spin electron with the CZPF background is not only electric but also magnetic. We calculate the scattering cross-section of magnetic dipole in the situation when a magnetic field, variable in time B arrow = B 0 arrow sin ωt, acts over the rigid magnetic dipole given by the symmetry of the model. The cross-section of a magnetic dipole σ m must be equal to the cross-section of an electric monopole σ e . This equality between σ m and σ e cross-sections is motivated, too, by the fact that, in the model of the two-dimensional oscillator, the electric charge q e has the motion speed c. (authors)

Optical model theory of elastic electron- and positron-atom scattering at intermediate energies

International Nuclear Information System (INIS)

Joachain, C.J.

1977-01-01

It is stated that the basic idea of the optical model theory is to enable analysis of the elastic scattering of a particle from a complex target by replacing the complicated interactions between the beam and the target by an optical potential, or pseudopotential, in which the incident particle moves. Once the optical potential is determined the original many-body elastic scattering problem reduces to a one-body situation. The resulting optical potential is, however, a very complicated operator, and the formal expressions obtained from first principles for the optical potential can only be evaluated approximately in a few simple cases, such as high energy elastic hadron-nucleus scattering, for the the optical potential can be expressed in terms of two-body hadron-nucleon amplitudes, and the non-relativistic elastic scattering of fast charged particles by atoms. The elastic scattering of an electron or positron by a neutral atom at intermediate energies is here considered. Exchange effects between the projectile and the atomic electrons are considered; also absorption and polarisation effects. Applications of the full-wave optical model have so far only been made to the elastic scattering of fast electrons and positrons by atomic H, He, Ne, and Ar. Agreements of the optical model results with absolute measurements of differential cross sections for electron scattering are very good, an agreement that improves as the energy increases, but deteriorates quickly as the incident energy becomes lower than 50 eV for atomic H or 100 eV for He. For more complex atoms the optical model calculations also appear very encouraging. With regard to positron-atom elastic scattering the optical model results for positron-He scattering differ markedly at small angles from the corresponding electron-He values. It would be interesting to have experimental angular distributions of positron-atom elastic scattering in order to check predictions of the optical model theory. (U.K.)

Inelastic interactions of swift electrons in solids

International Nuclear Information System (INIS)

Tung, C.J.; Ritchie, R.H.; Ashley, J.C.; Anderson, V.E.

1976-01-01

Theoretical calculations of electron mean free paths and electron slowing-down spectra in solids are described. These calculations involve (a) the use of an electron gas model to approximate the response of conduction band electrons in metals, (b) the application of a statistical model for the calculation of electron mean free paths in metals, (c) the development of an insulator model to describe valence band electrons in insulators and semiconductors, and (d) the use of data on atomic generalized oscillator strengths to describe the excitation of the ion cores. Exchange effects are included in the calculations through a semi-empirical procedure. Detailed results are presented for electron mean free paths in Ag, Au, Al, and Al 2 O 3 , and on the stopping power of Al and Al 2 O 3 , for electrons with energies at a few eV to 10 keV. The agreement of these calculations with experimental measurements is quite reasonable over a wide range of electron energies. A detailed description of the calculation of electron slowing-down spectra in solids is presented. Low energy electron slowing-down spectra of monoenergetic electron sources in Al and Al 2 O 3 are calculated. Calculations of electron slowing-down spectra in Al 2 O 3 are made using differential cross sections obtained employing an insulator model and from GOS functions for ion core electrons. Auger electron contributions to the slowing-down spectrum are discussed. Results for the slowing-down spectrum are compared with the experimental data measured by Birkhoff and coworkers. Generally good agreement is found over a wide range of electron energies

Vibrational and electronic spectra of 2-nitrobenzanthrone: An experimental and computational study

Science.gov (United States)

Onchoke, Kefa K.; Chaudhry, Saad N.; Ojeda, Jorge J.

2016-01-01

The environmental pollutant 2-nitrobenzanthrone (2-NBA) poses human health hazards, and is formed by atmospheric reactions of NOX gases with atmospheric particulates. Though its mutagenic effects have been studied in biological systems, its comprehensive spectroscopic experimental data are scarce. Thus, vibrational and optical spectroscopic analysis (UV-Vis, and fluorescence) of 2-NBA was studied using both experimental and density functional theory employing B3LYP method with 6-311 + G(d,p) basis set. The scaled theoretical vibrational frequencies show good agreement to experiment to within 5 cm- 1 and NBA, respectively. On the basis of normal coordinate analysis complete assignments of harmonic experimental infrared and Raman bands are made. The influence of the nitro group substitution upon the benzanthrone structure and symmetric CH vibrations, and electronic spectra is noted. This study is useful for the development of spectroscopy-mutagenicity relationships in nitrated polycyclic aromatic hydrocarbons.

Composition quantification of electron-transparent samples by backscattered electron imaging in scanning electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Müller, E., E-mail: erich.mueller@kit.edu; Gerthsen, D.

2017-02-15

The contrast of backscattered electron (BSE) images in scanning electron microscopy (SEM) depends on material parameters which can be exploited for composition quantification if some information on the material system is available. As an example, the In-concentration in thin In{sub x}Ga{sub 1−x}As layers embedded in a GaAs matrix is analyzed in this work. The spatial resolution of the technique is improved by using thin electron-transparent specimens instead of bulk samples. Although the BSEs are detected in a comparably small angular range by an annular semiconductor detector, the image intensity can be evaluated to determine the composition and local thickness of the specimen. The measured intensities are calibrated within one single image to eliminate the influence of the detection and amplification system. Quantification is performed by comparison of experimental and calculated data. Instead of using time-consuming Monte-Carlo simulations, an analytical model is applied for BSE-intensity calculations which considers single electron scattering and electron diffusion. - Highlights: • Sample thickness and composition are quantified by backscattered electron imaging. • A thin sample is used to achieve spatial resolution of few nanometers. • Calculations are carried out with a time-saving electron diffusion model. • Small differences in atomic number and density detected at low electron energies.

Design and experimental results of a new electron gun using a magnetic multipole plasma generator

International Nuclear Information System (INIS)

Tanaka, S.; Yokoyama, K.; Akiba, M.; Araki, M.; Dairaku, M.; Inoue, T.; Mizuno, M.; Okumura, Y.; Ohara, Y.; Seki, M.; Watanabe, K.

1991-01-01

A new electron gun utilizing a magnetic multipole plasma generator was designed and fabricated as the heat source of the high heat flux test facility, called JEBIS (JAERI electron beam irradiation stand). By changing the acceleration grids, this electron gun is able to produce a pencil to a sheetlike electron beams up to 4 A at 100 keV for 1 ms to continuous mode. In this electron gun, magnetic lens system is not adopted to focus the electron beam, but the space charge neutralization effect by the beam plasma produced downstream of the electron gun is utilized to prevent the blow-up of the electron beam. In addition, high permeability metal is embedded in the first and the second grids to magnetically shield the earth field and the stray field from the beam bending magnet. It was experimentally demonstrated that wide range of heat flux from 0.2 MW/m 2 to over 2000 MW/m 2 can be realized at the test sample position about 1.7 m downstream of the electron gun

Kinetic electron model for plasma thruster plumes

Science.gov (United States)

Merino, Mario; Mauriño, Javier; Ahedo, Eduardo

2018-03-01

A paraxial model of an unmagnetized, collisionless plasma plume expanding into vacuum is presented. Electrons are treated kinetically, relying on the adiabatic invariance of their radial action integral for the integration of Vlasov's equation, whereas ions are treated as a cold species. The quasi-2D plasma density, self-consistent electric potential, and electron pressure, temperature, and heat fluxes are analyzed. In particular, the model yields the collisionless cooling of electrons, which differs from the Boltzmann relation and the simple polytropic laws usually employed in fluid and hybrid PIC/fluid plume codes.

The HKS model for electron production in liquid water by light ions

International Nuclear Information System (INIS)

Bernal, M.A.; Liendo, J.A.

2006-01-01

The HKS model developed to determine ionization cross sections (ICS) for the interaction of non-relativistic ions with matter, is used for 0.5 MeV protons impinging on liquid water and some inconsistencies between the single (SDCS) and double (DDCS) differential cross section values predicted by the formalism are found. To overcome this problem, new SDCS and DDCS formulas are determined analytically by use of the transition probabilities published by Hansen and Kocbach [J.P. Hansen, L. Kocbach, J. Phys. B 22 (1989) L71]. The new cross section expressions applied to the 0.5 MeV proton on liquid water case, give perfectly consistent SDCS and DDCS values. Furthermore, SDCS and DDCS values predicted from the new formulas for ionization of liquid water by protons (0.5-4.2 MeV/u) and alpha particles (0.3-0.5 MeV/u) are compared with corresponding experimental cross section values reported in the literature for water vapor ionization. Despite of the simplicity of the HKS model, accurate secondary electron energy distributions can be obtained, even for electron energies as low as 10 eV. Although the same accuracy cannot be achieved for electron angular distributions, the HKS formalism can still be used when these distributions are not critical

Monte-Carlo simulations of secondary electron emission from CsI, induced by 1-10 keV X-rays and electrons

International Nuclear Information System (INIS)

Akkerman, A.; Gibrekhterman, A.; Breskin, A.; Chechik, R.

1992-05-01

A model for electron transport and emission in CsI is proposed. It is based on theoretically calculated microscopic cross-sections for electron interaction with the nuclear and the electronic components of the solid. A Monte Carlo program based on this model was developed to simulate secondary electron emission induced by X-rays and electrons in the energy range of 1 to 10 keV. The calculated secondary emission yields agree with existing experimental data. The model provides all necessary characteristics for the design of radiation detectors based on secondary electron emission. It can be expanded to higher incident energies and other alkali halides. (author)

Band electron spectrum and thermodynamic properties of the pseudospin-electron model with tunneling splitting of levels

Directory of Open Access Journals (Sweden)

O.Ya.Farenyuk

2006-01-01

Full Text Available The pseudospin-electron model with tunneling splitting of levels is considered. Generalization of dynamic mean-field method for systems with correlated hopping was applied to the investigation of the model. Electron spectra, electron concentrations, average values of pseudospins and grand canonical potential were calculated within the alloy-analogy approximation. Electron spectrum and dependencies of the electron concentrations on chemical potential were obtained. It was shown that in the alloy-analogy approximation, the model possesses the first order phase transition to ferromagnetic state with the change of chemical potential and the second order phase transition with the change of temperature.

Heavy component of spent nuclear fuel: Efficiency of model-substance ionization by electron-induced discharge

Energy Technology Data Exchange (ETDEWEB)

Antonov, N. N., E-mail: antonovnickola@gmail.com; Gavrikov, A. V.; Samokhin, A. A.; Smirnov, V. P. [Russian Academy of Sciences, High Energy Density Research Center, Joint Institute for High Temperatures (Russian Federation)

2016-12-15

The method of plasma separation of spent nuclear fuel can be tested with a model substance which has to be transformed from the condensed to plasma state. For this purpose, electron-induced discharge in lead vapor injected into the interelectrode gap is simulated using the kinetic approach. The ionization efficiency, the electrostatic-potential distribution, and those of the ion and electron densities in the discharge gap are derived as functions of the discharge-current density and concentration of the vapor of the model substance. Given a discharge-current density of 3.5 A/cm{sup 2} and a lead-vapor concentration of 2 × 10{sup 12} cm{sup –3}, the simulated ionization efficiency proves to be nearly 60%. The discharge in lead vapor is also investigated experimentally.

Modelling concentration-analgesia relationships for morphine to evaluate experimental pain models

DEFF Research Database (Denmark)

Sverrisdóttir, Eva; Foster, David John Richard; Upton, Richard Neil

2015-01-01

The aim of this study was to develop population pharmacokinetic-pharmacodynamic models for morphine in experimental pain induced by skin heat and muscle pressure, and to evaluate the experimental pain models with regard to assessment of morphine pharmacodynamics. In a randomized, double......-blind, placebo-controlled, crossover study, 39 healthy volunteers received an oral dose of 30 mg morphine hydrochloride or placebo. Non-linear mixed effects modelling was used to describe the plasma concentrations of morphine and metabolites, and the analgesic effect of morphine on experimental pain in skin...... and muscle. Baseline pain metrics varied between individuals and occasions, and were described with interindividual and interoccasion variability. Placebo-response did not change with time. For both pain metrics, morphine effect was proportional to baseline pain and was described with a linear model...

Simple model of electron beam initiated dielectric breakdown

International Nuclear Information System (INIS)

Beers, B.L.; Daniell, R.E.; Delmer, T.N.

1985-01-01

A steady state model that describes the internal charge distribution of a planar dielectric sample exposed to a uniform electron beam was developed. The model includes the effects of charge deposition and ionization of the beam, separate trap-modulated mobilities for electrons and holes, electron-hole recombination, and pair production by drifting thermal electrons. If the incident beam current is greater than a certain critical value (which depends on sample thickness as well as other sample properties), the steady state solution is non-physical

Electron Cloud Buildup Characterization Using Shielded Pickup Measurements and Custom Modeling Code at CESRTA

CERN Document Server

Crittenden, James A

2013-01-01

The Cornell Electron Storage Ring Test Accelerator experimental program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of small holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to the physical phenomena determining cloud buildup such as the photoelectron produ...

Modelling properties of hard x-rays generated by the interaction between relativistic electrons and very intense laser beams

International Nuclear Information System (INIS)

Popa, Alexandru

2009-01-01

In a previous paper we presented a calculation model for high harmonic generation by relativistic Thomson scattering of the electromagnetic radiation by free electrons. In this paper we present a similar model for the calculation of the energies of hard x-rays (20- 200 keV) resulted from the interaction between relativistic electrons (20-100 MeV) and very intense laser beams. Starting from the relativistic equations of motion of an electron in the electromagnetic field we show that the Lienard-Wiechert equation leads to electromagnetic waves whose frequencies are in the domain of hard x-rays. When the relativistic parameter of the laser beam is greater than unity, the model predicts the existence of harmonics of the above frequencies. Our theoretical values are in good agreement with experimental values of the x-ray energies from the literature and predict accurately their angular distribution.

Electron Microscopic Changes of Rabbit Retina after Chromovitrectomy Using Combined Dyes (Experimental Study

Directory of Open Access Journals (Sweden)

B. M. Aznabaev

2018-01-01

Full Text Available Purpose: to evaluate on experimental model electron-microscopic changes of rabbit retina after staining of the posterior eye segmentwith combined dyes based on Trypan blue and Brilliant blue G for the assessment of their safety. Methods. The study was performed onChinchilla breed rabbits. Combined dyes based on Trypan blue and Brilliant blue were used: MembraneBlue-Dual (DORC, Netherlandsand “Staining solution for ophthalmic surgery” (JCS “Optimedservis”, Russia. Standard three-port vitrectomy technique was used. After vitreous removal dyes were injected in vitreous cavity and exposed for 10 seconds and then removed. The vitreous cavity was filled by a balanced salt solution. An electron-microscopic evaluation was performed on 5, 14 and 30 days after surgery. Eyes were enucleated in 20 minutes after animal was killed by air embolization. Intact eyes were used as a control, all samples were prepared in same сonditions. The damage of the retina architectonics and the presence of intracellular inclusions were evaluated. Results. The staged character of pathomorphological changes was revealed. On the 5th day moderate edema and hydropic dystrophy of neurons were registered. On the 14th day, there was no negative dynamics. On day 30, the signs of edema and dystrophy of neurons practically disappeared, which may indicate a fundamental reversibility of the registered changes. Conclusion. Investigated dyes for staining intraocular structures based on Trypan blue and Brilliant blue did not cause significant histomorphological changes and toxic effects on retinal cell structures. Detected electron microscopic changes were insignificant, had reversible character and could be mostly caused by a surgical injury.

Electron emission resulting from fast ion impact on thin metal foils: Implications of these data for development of track structure models

Energy Technology Data Exchange (ETDEWEB)

DuBois, R.D.; Drexler, C.G.

1993-04-01

Experimental information useful in improving and testing theoretical models of energy deposition and redistribution in particle-condensed phase media is discussed. An overview of information available from previous, and ongoing, studies of the electron emission from thin foils is presented and the need for doubly differential electron energy and angular distribution data stressed. Existing data are used to demonstrate that precisely known, and controllable, surface and bulk conditions of the condensed-phase media are required for experimental studies of this type. Work in progress and improvements planned for future studies at the Pacific Northwest Laboratory are outlined.

Development of a physical and electronic model for RuO 2 nanorod rectenna devices

Science.gov (United States)

Dao, Justin

Ruthenium oxide (RuO2) nanorods are an emergent technology in nanostructure devices. As the physical size of electronics approaches a critical lower limit, alternative solutions to further device miniaturization are currently under investigation. Thin-film nanorod growth is an interesting technology, being investigated for use in wireless communications, sensor systems, and alternative energy applications. In this investigation, self-assembled RuO2 nanorods are grown on a variety of substrates via a high density plasma, reactive sputtering process. Nanorods have been found to grow on substrates that form native oxide layers when exposed to air, namely silicon, aluminum, and titanium. Samples were analyzed with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques. Conductive Atomic Force Microscopy (C-AFM) measurements were performed on single nanorods to characterize structure and electrical conductivity. The C-AFM probe tip is placed on a single nanorod and I-V characteristics are measured, potentially exhibiting rectifying capabilities. An analysis of these results using fundamental semiconductor physics principles is presented. Experimental data for silicon substrates was most closely approximated by the Simmons model for direct electron tunneling, whereas that of aluminum substrates was well approximated by Fowler-Nordheim tunneling. The native oxide of titanium is regarded as a semiconductor rather than an insulator and its ability to function as a rectifier is not strong. An electronic model for these nanorods is described herein.

Theory of local and global processes which affect solar wind electrons. 2. Experimental support

International Nuclear Information System (INIS)

Scudder, J.D.; Olbert, S.

1979-01-01

We have extended the theoretical considerations of Scudder and Olbert (1979) (hereafter called paper 1) to show from the microscopic characteristics of the Coulomb cross section that there are three natural subpopulations for plasma electrons: the subthermals with local kinetic energy E 7kT/sub c/. We present experimental support from three experimental groups on three different spacecraft over a radial range in the interplanetary medium for the five interrelations projected in paper 1 between solar wind electron properties and changes in the interplanetary medium: (1) subthermals respond primarily to local changes (compressions and rarefactions) in stream dynamics: (2) the extrathermal fraction of the ambient electron density should be anticorrelated with the asymptotic bulk speed; (3) the extrathermal 'temperature' should be anticorrelated with the local wind speed at 1 AU; (4) the heat flux carried by electrons should be anticorrelated with the local bulk speed; and (5) the extrathermal differential 'temperature' should be nearly independent of radius within 1 Au. From first principles and the spatial inhomogeneity of the plasma we show that the velocity dependence of Coulomb collisions in the solar wind plasmaproduces a bifurcation in the solar wind electron distribution function at a transition energy E*. This energy is theoretically shown to scale with the local thermal temperature as E*(r) approx. =GAMMAkT/sub c/(r). This scaling is observationally supported over the radial range from 0.45 to 0.9 AU and at 1 AU. The extrathermals, defined on the basis of Coulomb collisions, are synonymous with the subpopulation previously labeled in the literature as the 'halo' or 'hot' component

Field emission electronics

CERN Document Server

Egorov, Nikolay

2017-01-01

This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.

Radiolysis of liquid water: an attempt to reconcile Monte-Carlo calculations with new experimental hydrated electron yield data at early times

International Nuclear Information System (INIS)

Muroya, Y.; Meesungnoen, J.; Jay-Gerin, J.-P.; Filali-Mouhim, A.; Goulet, T.; Katsumura, Y.; Mankhetkorn, S.

2002-01-01

A re-examination of our Monte-Carlo modeling of the radiolysis of liquid water by low linear-energy-transfer (LET ∼ 0.3 keV μm -1 ) radiation is undertaken herein in an attempt to reconcile the results of our simulation code with recently revised experimental hydrated electron (e aq - ) yield data at early times. The thermalization distance of subexcitation electrons, the recombination cross section of the electrons with their water parent cations prior to thermalization, and the branching ratios of the different competing mechanisms in the dissociative decay of vibrationally excited states of water molecules were taken as adjustable parameters in our simulations. Using a global-fit procedure, we have been unable to find a set of values for those parameters to simultaneously reproduce (i) the revised e aq - yield of 4.0 ± 0.2 molecules per 100 eV at 'time zero' (that is, a reduction of ∼20% over the hitherto accepted value of 4.8 molecules per 100 eV), (ii) the newly measured e aq - decay kinetic profile from 100 ps to 10 ns, and (iii) the time-dependent yields of the other radiolytic species H . , . OH, H 2 , and H 2 O 2 (up to ∼1 μs). The lowest possible limiting 'time-zero' yield of e aq - that we could in fact obtain, while ensuring an acceptable agreement between all computed and experimental yields, was ∼4.4 to 4.5 molecules per 100 eV. Under these conditions, the mean values of the electron thermalization distance and of the geminate electron-cation recombination probability, averaged over the subexcitation electron 'entry spectrum,' are found to be equal to ∼139 A and ∼18%, respectively. These values are to be compared with those obtained in our previous simulations of liquid water radiolysis, namely ∼88 A and ∼5.5%, respectively. Our average electron thermalization distance is also to be compared with the typical size (∼64-80 A) of the initial hydrated electron distributions estimated in current deterministic models of 'spur' chemistry

Experimental Tests of Quantum Mechanics: Pauli Exclusion Principle and Spontaneous Collapse Models

CERN Document Server

Petrascu, Catalina Curceanu; Bragadireanu, Mario; Clozza, Alberto; Guaraldo, Carlo; Iliescu, Mihai; Rizzo, Alessandro; Vidal, Antonio Romero; Scordo, Alessandro; Sirghi, Diana Laura; Sirghi, Florin; Sperandio, Laura; Doce, Oton Vazquez; Bassi, Angelo; Donadi, Sandro; Milotti, Edoardo; Laubenstein, Matthias; Bertolucci, Sergio; Bragadireanu, Mario; Curceanu, Catalina; Pietreanu, Dorel; Ponta, Titus; Cargnelli, Michael; Ishiwatari, Tomoichi; Marton, Johann; Widmann, Eberhard; Zmeskal, Johann; Matteo, Sergio di; Egger, Jean Pierre

2014-01-01

The Pauli exclusion principle (PEP), as a consequence or the spin-statistics connection, is one of the basic principles of the modern physics. Being at the very basis of our understanding of matter, it spurs a lively debate on its possible limits, deeply rooted as it is in the very foundations of Quantum Field Theory. The VIP (VIolation of the Pauli exclusion principle) experiment is searching for a possible small violation of the PEP for electrons, using the method of searching for Pauli Exclusion Principle forbidden atomic transitions in copper. We describe the experimental method and the obtained results; we briefly present future plans to go beyond the actual limit by upgrading the experiment using vetoed new spectroscopic fast Silicon Drift Detectors. We also mention the possibility of using a similar experimental technique to search for possible X-rays generated in the spontaneous collapse models of quantum mechanics.

New experimental initiatives using very highly charged ions from an 'electron beam ion trap'

International Nuclear Information System (INIS)

Schneider, D.

1996-01-01

A short review of the experimental program in highly-charged heavy ion physics conducted at the Lawrence Livermore National Laboratory Electron Beam Ion Trap (EBIT) facility is presented. The heavy-ion research, involving ions up to fully stripped U 92+ , includes precision x-ray spectroscopy and lifetime studies, electron impact ionization and excitation cross section measurements. The investigations of ion-surface interactions following the impact of high-Z highly charged ions on surfaces are aimed to study the neutralization dynamics effecting the ion and the response of the surface as well. (author)

Refrigerant flow through electronic expansion valve: Experiment and neural network modeling

International Nuclear Information System (INIS)

Cao, Xiang; Li, Ze-Yu; Shao, Liang-Liang; Zhang, Chun-Lu

2016-01-01

Highlights: • Experimental data from different sources were used in comparison of EEV models. • Artificial neural network in EEV modeling is superior to literature correlations. • Artificial neural network with 4-4-1 structure and S function is recommended. • Artificial neural network is flexible for EEV mass flow rate and opening prediction. - Abstract: Electronic expansion valve (EEV) plays a crucial role in controlling refrigerant mass flow rate of refrigeration or heat pump systems for energy savings. However, complexities in two-phase throttling process and geometry make accurate modeling of EEV flow characteristics more difficult. This paper developed an artificial neural network (ANN) model using refrigerant inlet and outlet pressures, inlet subcooling, EEV opening as ANN inputs, refrigerant mass flow rate as ANN output. Both linear and nonlinear transfer functions in hidden layer were used and compared to each other. Experimental data from multiple sources including in-house experiments of one EEV with R410A were used for ANN training and test. In addition, literature correlations were compared with ANN as well. Results showed that the ANN model with nonlinear transfer function worked well in all cases and it is much accurate than the literature correlations. In all cases, nonlinear ANN predicted refrigerant mass flow rates within ±0.4% average relative deviation (A.D.) and 2.7% standard deviation (S.D.), meanwhile it predicted the EEV opening at 0.1% A.D. and 2.1% S.D.

A revised partiality model and post-refinement algorithm for X-ray free-electron laser data

Energy Technology Data Exchange (ETDEWEB)

Ginn, Helen Mary [Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Brewster, Aaron S.; Hattne, Johan [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Evans, Gwyndaf; Wagner, Armin [Harwell Science and Innovation Campus, Fermi Avenue, Didcot OX11 0QX (United Kingdom); Grimes, Jonathan M. [Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Harwell Science and Innovation Campus, Fermi Avenue, Didcot OX11 0QX (United Kingdom); Sauter, Nicholas K. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Sutton, Geoff [Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Stuart, David Ian, E-mail: dave@strubi.ox.ac.uk [Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Harwell Science and Innovation Campus, Fermi Avenue, Didcot OX11 0QX (United Kingdom)

2015-05-23

An updated partiality model and post-refinement algorithm for XFEL snapshot diffraction data is presented and confirmed by observing anomalous density for S atoms at an X-ray wavelength of 1.3 Å. Research towards using X-ray free-electron laser (XFEL) data to solve structures using experimental phasing methods such as sulfur single-wavelength anomalous dispersion (SAD) has been hampered by shortcomings in the diffraction models for X-ray diffraction from FELs. Owing to errors in the orientation matrix and overly simple partiality models, researchers have required large numbers of images to converge to reliable estimates for the structure-factor amplitudes, which may not be feasible for all biological systems. Here, data for cytoplasmic polyhedrosis virus type 17 (CPV17) collected at 1.3 Å wavelength at the Linac Coherent Light Source (LCLS) are revisited. A previously published definition of a partiality model for reflections illuminated by self-amplified spontaneous emission (SASE) pulses is built upon, which defines a fraction between 0 and 1 based on the intersection of a reflection with a spread of Ewald spheres modelled by a super-Gaussian wavelength distribution in the X-ray beam. A method of post-refinement to refine the parameters of this model is suggested. This has generated a merged data set with an overall discrepancy (by calculating the R{sub split} value) of 3.15% to 1.46 Å resolution from a 7225-image data set. The atomic numbers of C, N and O atoms in the structure are distinguishable in the electron-density map. There are 13 S atoms within the 237 residues of CPV17, excluding the initial disordered methionine. These only possess 0.42 anomalous scattering electrons each at 1.3 Å wavelength, but the 12 that have single predominant positions are easily detectable in the anomalous difference Fourier map. It is hoped that these improvements will lead towards XFEL experimental phase determination and structure determination by sulfur SAD and will

Experimental and numerical studies of sheet electron beam propagation through a planar wiggler magnet

International Nuclear Information System (INIS)

Zhang, Ze Xiang; Granatstein, V.L.; Destler, W.W.; Rodgers, J.; Cheng, S.; Antonsen, T.M. Jr.; Levush, B.; Bidwell, S.W.

1993-01-01

Detailed experimental studies on sheet relativistic electron beam propagation through a long planar wiggler are reported and compared with numerical simulations. The planar wiggler has 56 periods with a period of 9.6 mm. Typically, the wiggler field peak amplitude is 5 kG. The experimental efforts have been focused on control of the deviation of the beam toward the side edge of the planar wiggler along the wide transverse direction. It is found that a suitably tapered magnetic field configuration at the wiggler entrance can considerably reduce the rate of the deviation. The effects of the following techniques on beam transport efficiency are also discussed: side focusing, beam transverse velocity tuning at the wiggler entrance, and beam spread limiting. High beam transport efficiency (almost 100%) of a 15 A beam has been obtained in some cases. The results are relevant to development of a free electron laser amplifier for application to stabilizing and heating of plasma in magnetic fusion research

An experimental study of electron transfer and emission during particle-surface interactions

International Nuclear Information System (INIS)

McGrath, C.T.

2000-09-01

A new coincidence technique has been developed and used to study the secondary electron emission that arises during the interaction of ions with surfaces. This coincidence technique allows the secondary electron emission statistics due to the impact of singly, doubly and multiply charged ions on surfaces to be measured in coincidence with reflected particles, in specific charge states and with specific post-collision trajectories. This system has been used to study the impact of 8 keV H + ions on polycrystalline copper and aluminium targets. Under these conditions the potential emission contribution is negligible and the electron emission is almost entirely due to kinetic emission processes. The sub-surface contribution to the observed electron emission has been isolated using two newly developed models. These models provide valuable information about the depth and amount of surface penetration and on the probability for subsequent electron transport to the surface. The impact of 2 - 100 keV Xe q+ (q = 1 - 10) ions on polycrystalline copper has also been studied using this system. From the subsequent data the potential and kinetic contributions to secondary electron emission have been separated using a previously established model for potential emission. The resulting kinetic emission yield increases with increasing ion impact energy, consistent with current concepts on quasimolecular ionisation. For ions impacting at large incident angles evidence for sub-surface emission has also been observed. The degree of penetration increases with ion impact energy, consistent with current concepts on this effect. The formation of H - ions from incident H + ions has also been studied by measuring the secondary electron emission statistics in coincidence with reflected particles in specific final charge states. This preliminary data is consistent with a two-step process of Auger neutralisation followed by resonant electron capture to the affinity level. However this mechanism

Hemorrhoids: an experimental model in monkeys

Directory of Open Access Journals (Sweden)

Plapler Hélio

2006-01-01

Full Text Available PURPOSE: Hemorrhoids are a matter of concern due to a painful outcome. We describe a simple, easy and reliable experimental model to produce hemorrhoids in monkeys. METHODS: 14 monkeys (Cebus apella were used. After general anesthesia, hemorrhoids were induced by ligation of the inferior hemorrhoidal vein, which is very alike to humans. The vein was located through a perianal incision, dissected and ligated with a 3-0 vicryl. The skin was sutured with a 4-0 catgut thread. Animals were kept in appropriate cages and evaluated daily. RESULTS: Nine days later there were hemorrhoidal piles in the anus in fifty percent (50% of the animals. Outcome was unremarkable. There was no bleeding and all animals showed no signs of pain or suffering. CONCLUSION: This is an affordable and reliable experimental model to induce hemorrhoids for experimental studies.

Research on lightning stroke model and characteristics of electronic transformer

Directory of Open Access Journals (Sweden)

Li Mu

2018-01-01

Full Text Available In order to improve the reliability of power supply, a large number of electronic voltage and current transformers are used in digital substations. In this paper, the mathematical model of the electronic transformer is analyzed firstly, and its circuit model is given. According to the difference of working characteristics between voltage transformer and current transformer, the circuit model of voltage type electronic transformer and current type electronic transformer is given respectively. By analyzing their broadband transmission characteristics, the accuracy of the model is verified, and their lightning analysis models are obtained.

An analytic model for the electrostatic contribution of the electron cloud to the vertical tune-shift

International Nuclear Information System (INIS)

Schaechter, Levi

2008-01-01

An analytic quasi-static model is developed for the analysis of the tune-shift associated with the presence of an electron cloud in a damping ring. The essential assumption is that in its direction of motion, a bunch experiences a uniform cloud density but the latter varies from one bunch to another. A second important component of the model is the life-time since it controls the build-up, the equilibrium as well as the decay of the cloud. It is demonstrated analytically that in case of a train of positron bunches, electrons may be trapped in the vertical direction for the entire train duration. Assuming that the ring is dominated by vertical magnetic fields due to either bends or wigglers, we found excellent agreement between the theoretical predictions and the experimental results reported at Cornell Electron/Positron Storage Ring. The ratio between the vertical and horizontal tune-shifts is shown to be indicative of the distribution of the cloud in the beam-chamber

Experimental test of nuclear magnetization distribution and nuclear structure models

International Nuclear Information System (INIS)

Beirsdorfer, P; Crespo-Lopez-Urrutia, J R; Utter, S B.

1999-01-01

Models exist that ascribe the nuclear magnetic fields to the presence of a single nucleon whose spin is not neutralized by pairing it up with that of another nucleon; other models assume that the generation of the magnetic field is shared among some or all nucleons throughout the nucleus. All models predict the same magnetic field external to the nucleus since this is an anchor provided by experiments. The models differ, however, in their predictions of the magnetic field arrangement within the nucleus for which no data exist. The only way to distinguish which model gives the correct description of the nucleus would be to use a probe inserted into the nucleus. The goal of our project was to develop exactly such a probe and to use it to measure fundamental nuclear quantities that have eluded experimental scrutiny. The need for accurately knowing such quantities extends far beyond nuclear physics and has ramifications in parity violation experiments on atomic traps and the testing of the standard model in elementary particle physics. Unlike scattering experiments that employ streams of free particles, our technique to probe the internal magnetic field distribution of the nucleus rests on using a single bound electron. Quantum mechanics shows that an electron in the innermost orbital surrounding the nucleus constantly dives into the nucleus and thus samples the fields that exist inside. This sampling of the nucleus usually results in only minute shifts in the electron s average orbital, which would be difficult to detect. By studying two particular energy states of the electron, we can, however, dramatically enhance the effects of the distribution of the magnetic fields in the nucleus. In fact about 2% of the energy difference between the two states, dubbed the hyperfine splitting, is determined by the effects related to the distribution of magnetic fields in the nucleus, A precise measurement of this energy difference (better than 0.01%) would then allow us to place

Improving the physiological realism of experimental models.

Science.gov (United States)

Vinnakota, Kalyan C; Cha, Chae Y; Rorsman, Patrik; Balaban, Robert S; La Gerche, Andre; Wade-Martins, Richard; Beard, Daniel A; Jeneson, Jeroen A L

2016-04-06

The Virtual Physiological Human (VPH) project aims to develop integrative, explanatory and predictive computational models (C-Models) as numerical investigational tools to study disease, identify and design effective therapies and provide an in silico platform for drug screening. Ultimately, these models rely on the analysis and integration of experimental data. As such, the success of VPH depends on the availability of physiologically realistic experimental models (E-Models) of human organ function that can be parametrized to test the numerical models. Here, the current state of suitable E-models, ranging from in vitro non-human cell organelles to in vivo human organ systems, is discussed. Specifically, challenges and recent progress in improving the physiological realism of E-models that may benefit the VPH project are highlighted and discussed using examples from the field of research on cardiovascular disease, musculoskeletal disorders, diabetes and Parkinson's disease.

Electron energy distribution in a weakly ionized plasma

International Nuclear Information System (INIS)

Cesari, C.

1967-03-01

The aim of this work is to determine from both the theoretical and experimental points of view the type of distribution function for the electronic energies existing in a positive-column type cold laboratory plasma having an ionization rate of between 10 -6 and 10 -7 . The theoretical analysis, based on the imperfect Lorentz model and taking into account inelastic collisions is developed from the Boltzmann equation. The experimental method which we have employed for making an electrostatic analysis of the electronic energies makes use of a Langmuir probe used in conjunction with a transistorized electronic device. A comparison between the experimental and theoretical results yields information concerning the mechanisms governing electronic energy transfer on a microscopic scale. (author) [fr

Analysis of detached recombining plasmas by collisonal-radiative model with energetic electron component

International Nuclear Information System (INIS)

Ohno, N.; Motoyama, M.; Takamura, S.

2001-01-01

using CR model for a helium plasma (Goto-Fujimoto code), in which the energetic electron component (electron beam) is taken into account in addition to the bulk electron Maxwellian distribution function. It is found that the evaluated bulk electron temperature with the method of Boltzmann plot tends to decrease with an increase in the electron beam density and/or energy because the population densities in relatively lower excited states become large, comparing with those in higher excited state. This result agrees with the experimental observations. We have also analyzed transition of recombining plasma to ionizing one and vice versa in detail. This analysis can reproduce the inverse ELM phenomena observed in JET and ASDEX-U. (orig.)

Multiscale models of metal behaviour and structural change under the action of high-current electron irradiation

International Nuclear Information System (INIS)

Mayer, A E; Krasnikov, V S; Mayer, P N; Pogorelko, V V

2017-01-01

We present our models of the tensile fracture of metals in the solid and molten states, the melting and the plastic deformation of the solid metals. Also we discuss implementation of these models for simulation of the high current electron beam impact on metals. The models are constructed in the following way: the atomistic simulations are used at the first stage for investigation of dynamics and kinetics of structural defects in material (voids, dislocations, melting cites); equations describing evolution of such defects are constructed, verified, and their parameters are identified by means of comparison with the atomistic simulation result; finally, the defects evolution equations are incorporated into the continuum model of the substance behaviour on the macroscopic scale. The obtained continuum models with accounting of defects subsystems are tested in comparison with the experimental results known from literature. The proposed models not only allow one to describe the metal behaviour under the conditions of intensive electron irradiation, but they also allow one to determine the structural changes in the irradiated material. (paper)

Experimental investigation of the trapping and energy loss mechanisms of intense relativistic electron rings in hydrogen gas and plasma

International Nuclear Information System (INIS)

Smith, A.C. Jr.

1977-01-01

The results of an experimental study on the trapping and energy loss mechanisms of intense, relativistic electron rings confined in Astron-like magnetic field geometries are presented. The work is subdivided into four sections: gas trapping; average ring electron energetics; plasma trapping, and hollow-beam cusp-injection into gas and plasma. The mechanisms by which the injected beam coalesces into a current ring in the existing Cornell RECE-Berta facility are considered. To investigate the nature of ring electron energy loss mechanisms following completion of the trapping process, a diagnostic was developed utilizing multi-foil X-ray absorption spectroscopy to analyze the Bremsstrahlung generated by the electrons as they impinge upon a thin tungsten wire target suspended in the circulating current. Finally, a set of preliminary experimental results is presented in which an annular electron beam was passed through a coaxial, non-adiabatic magnetic cusp located at one end of a magnetic mirror well

Molecular modeling and multiscaling issues for electronic material applications

CERN Document Server

Iwamoto, Nancy; Yuen, Matthew; Fan, Haibo

Volume 1 : Molecular Modeling and Multiscaling Issues for Electronic Material Applications provides a snapshot on the progression of molecular modeling in the electronics industry and how molecular modeling is currently being used to understand material performance to solve relevant issues in this field. This book is intended to introduce the reader to the evolving role of molecular modeling, especially seen through the eyes of the IEEE community involved in material modeling for electronic applications.  Part I presents  the role that quantum mechanics can play in performance prediction, such as properties dependent upon electronic structure, but also shows examples how molecular models may be used in performance diagnostics, especially when chemistry is part of the performance issue.  Part II gives examples of large-scale atomistic methods in material failure and shows several examples of transitioning between grain boundary simulations (on the atomistic level)and large-scale models including an example ...

Electron-positron annihilation physics

International Nuclear Information System (INIS)

Foster, B.

1990-01-01

Electron-Positron Annihilation Physics is a detailed introduction to the main topics in e + e - annihilation, with particular emphasis on experimental work. Four main areas are covered, each in great detail, beginning with the Standard Model and its application to the production of lepton, quark and boson pairs. Secondly, the general features of fragmentation and different fragmentation models are explained. Chapter 3 is devoted to heavy quark and lepton physics, to which e + e - experiments have made an immense contribution. The final chapter, 'Where do we go from here?', looks for new phenomena beyond the Standard Model. Predictions of theory are compared with experimental results, highlighting shortcomings of some current theories. Details of instrumentation are included whenever possible. This ensures that the book is of maximum practical use to research workers. A comprehensive introduction to the major topics in the field, Electron-Positron Annihilation Physics is aimed at both graduate students studying high-energy physics and mature research workers. (author)

Diffusive and convective transport modelling from analysis of ECRH-stimulated electron heat wave propagation

International Nuclear Information System (INIS)

Erckmann, V.; Gasparino, U.; Giannone, L.

1992-01-01

ECRH power modulation experiments in toroidal devices offer the chance to analyze the electron heat transport more conclusively: the electron heat wave propagation can be observed by ECE (or SX) leading to radial profiles of electron temperature modulation amplitude and time delay (phase shift). Taking also the stationary power balance into account, the local electron heat transport can be modelled by a combination of diffusive and convective transport terms. This method is applied to ECRH discharges in the W7-AS stellarator (B=2.5T, R=2m, a≤18 cm) where the ECRH power deposition is highly localized. In W7-AS, the T e modulation profiles measured by a high resolution ECE system are the basis for the local transport analysis. As experimental errors limit the separation of diffusive and convective terms in the electron heat transport for central power deposition, also ECRH power modulation experiments with off-axis deposition and inward heat wave propagation were performed (with 70 GHz o-mode as well as with 140 GHz x-mode for increased absorption). Because collisional electron-ion coupling and radiative losses are only small, low density ECRH discharges are best candidates for estimating the electron heat flux from power balance. (author) 2 refs., 3 figs

Modelling of pulsed electron beam induced graphite ablation: Sublimation versus melting

Science.gov (United States)

Ali, Muddassir; Henda, Redhouane

2017-12-01

Pulsed electron beam ablation (PEBA) has recently emerged as a very promising technique for the deposition of thin films with superior properties. Interaction of the pulsed electron beam with the target material is a complex process, which consists of heating, phase transition, and erosion of a small portion from the target surface. Ablation can be significantly affected by the nature of thermal phenomena taking place at the target surface, with subsequent bearing on the properties, stoichiometry and structure of deposited thin films. A two stage, one-dimensional heat conduction model is presented to describe two different thermal phenomena accounting for interaction of a graphite target with a polyenergetic electron beam. In the first instance, the thermal phenomena are comprised of heating, melting and vaporization of the target surface, while in the second instance the thermal phenomena are described in terms of heating and sublimation of the graphite surface. In this work, the electron beam delivers intense electron pulses of ∼100 ns with energies up to 16 keV and an electric current of ∼400 A to a graphite target. The temperature distribution, surface recession velocity, ablated mass per unit area, and ablation depth for the graphite target are numerically simulated by the finite element method for each case. Based on calculation findings and available experimental data, ablation appears to occur mainly in the regime of melting and vaporization from the surface.

Mesoscopic Electronics in Solid State Nanostructures

CERN Document Server

Heinzel, Thomas

2007-01-01

This text treats electronic transport in the regime where conventional textbook models are no longer applicable, including the effect of electronic phase coherence, energy quantization and single-electron charging. This second edition is completely updated and expanded, and now comprises new chapters on spin electronics and quantum information processing, transport in inhomogeneous magnetic fields, organic/molecular electronics, and applications of field effect transistors. The book also provides an overview of semiconductor processing technologies and experimental techniques. With a number of

Experimental Model for Retrospective Assessment of X-Ray Exposures in Dento-Maxillary Radiology Measured by Electron Paramagnetic Resonance in Tooth Enamel

Directory of Open Access Journals (Sweden)

Ioana Costina DÂNŞOREANU

2009-12-01

Full Text Available Electron paramagnetic resonance (EPR dosimetry of human tooth enamel has been widely used in measuring radiation doses in various scenarios. For experimental purposes in X-ray diagnostic or therapy human persons can not be involved. For such cases we have developed an EPR dosimetry technique making use of enamel of molars extracted from pigs. The method can evaluate doses and dose-profiles of irradiated teeth at low level as 50 – 100 mGy (in air. EPR-spectra acquisition, data processing and dose assessment were done using non-dedicated equipment, devices and software.

A parametric model to describe neutron spectra around high-energy electron accelerators and its application in neutron spectrometry with Bonner Spheres

Science.gov (United States)

Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo

2010-03-01

Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.

A parametric model to describe neutron spectra around high-energy electron accelerators and its application in neutron spectrometry with Bonner Spheres

International Nuclear Information System (INIS)

Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo

2010-01-01

Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.

Electron localization in liquid hydrocarbons: The Anderson model

International Nuclear Information System (INIS)

Hug, Gordon L.; Mozumder, A.

2008-01-01

Anderson's model is applied for initial localization in liquid hydrocarbons (particularly n-alkanes) in conjunction with certain results of scaling theory. Medium connectivity is calculated using experimental X-ray data on liquid structure, from which critical disorder (W/V) c is computed, where W is diagonal disorder and V is the transfer energy. Actual W prevailing in the liquid is computed from anisotropic molecular polarizability. V is estimated by a heuristic procedure originating in scaling theory. These values are used to compute the percentage of initially delocalized states available for low-energy electrons in alkane liquids. This percentage decreases monotonically from methane (100%) to n-pentane and beyond (0%). In ethane and propane, the initial states are highly delocalized (97.6% and 83.9%, respectively). Subsequent trapping changes the situation as evidenced in mobility studies. Butane presents a partially, intermediate delocalized case (53.2%)

On the applicability of one- and many-electron quantum chemistry models for hydrated electron clusters

Science.gov (United States)

Turi, László

2016-04-01

We evaluate the applicability of a hierarchy of quantum models in characterizing the binding energy of excess electrons to water clusters. In particular, we calculate the vertical detachment energy of an excess electron from water cluster anions with methods that include one-electron pseudopotential calculations, density functional theory (DFT) based calculations, and ab initio quantum chemistry using MP2 and eom-EA-CCSD levels of theory. The examined clusters range from the smallest cluster size (n = 2) up to nearly nanosize clusters with n = 1000 molecules. The examined cluster configurations are extracted from mixed quantum-classical molecular dynamics trajectories of cluster anions with n = 1000 water molecules using two different one-electron pseudopotenial models. We find that while MP2 calculations with large diffuse basis set provide a reasonable description for the hydrated electron system, DFT methods should be used with precaution and only after careful benchmarking. Strictly tested one-electron psudopotentials can still be considered as reasonable alternatives to DFT methods, especially in large systems. The results of quantum chemistry calculations performed on configurations, that represent possible excess electron binding motifs in the clusters, appear to be consistent with the results using a cavity structure preferring one-electron pseudopotential for the hydrated electron, while they are in sharp disagreement with the structural predictions of a non-cavity model.

On the applicability of one- and many-electron quantum chemistry models for hydrated electron clusters

Energy Technology Data Exchange (ETDEWEB)

Turi, László, E-mail: turi@chem.elte.hu [Department of Physical Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest 112 (Hungary)

2016-04-21

We evaluate the applicability of a hierarchy of quantum models in characterizing the binding energy of excess electrons to water clusters. In particular, we calculate the vertical detachment energy of an excess electron from water cluster anions with methods that include one-electron pseudopotential calculations, density functional theory (DFT) based calculations, and ab initio quantum chemistry using MP2 and eom-EA-CCSD levels of theory. The examined clusters range from the smallest cluster size (n = 2) up to nearly nanosize clusters with n = 1000 molecules. The examined cluster configurations are extracted from mixed quantum-classical molecular dynamics trajectories of cluster anions with n = 1000 water molecules using two different one-electron pseudopotenial models. We find that while MP2 calculations with large diffuse basis set provide a reasonable description for the hydrated electron system, DFT methods should be used with precaution and only after careful benchmarking. Strictly tested one-electron psudopotentials can still be considered as reasonable alternatives to DFT methods, especially in large systems. The results of quantum chemistry calculations performed on configurations, that represent possible excess electron binding motifs in the clusters, appear to be consistent with the results using a cavity structure preferring one-electron pseudopotential for the hydrated electron, while they are in sharp disagreement with the structural predictions of a non-cavity model.

Electronic structure of copper phthalocyanine : An experimental and theoretical study of occupied and unoccupied levels

NARCIS (Netherlands)

Evangelista, Fabrizio; Carravetta, Vincenzo; Stefani, Giovanni; Jansik, Branislav; Alagia, Michele; Stranges, Stefano; Ruocco, Alessandro

2007-01-01

An experimental and theoretical study of the electronic structure of copper phthalocyanine (CuPc) molecule is presented. We performed x-ray photoemission spectroscopy (XPS) and photoabsorption [x-ray absorption near-edge structure (XANES)] gas phase experiments and we compared the results with

Electronic structure and microscopic model of V2GeO4F2-a quantum spin system with S = 1

International Nuclear Information System (INIS)

Rahaman, Badiur; Saha-Dasgupta, T

2007-01-01

We present first-principles density functional calculations and downfolding studies of the electronic and magnetic properties of the oxide-fluoride quantum spin system V 2 GeO 4 F 2 . We discuss explicitly the nature of the exchange paths and provide quantitative estimates of magnetic exchange couplings. A microscopic modelling based on analysis of the electronic structure of this systems puts it in the interesting class of weakly coupled alternating chain S = 1 systems. Based on the microscopic model, we make inferrences about its spin excitation spectra, which needs to be tested by rigorous experimental study

Optimising electron microscopy experiment through electron optics simulation

Energy Technology Data Exchange (ETDEWEB)

Kubo, Y. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Hitachi High-Technologies Corporation, 882, Ichige, Hitachinaka, Ibaraki 312-8504 (Japan); Gatel, C.; Snoeck, E. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Houdellier, F., E-mail: florent.houdellier@cemes.fr [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France)

2017-04-15

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

Optimising electron microscopy experiment through electron optics simulation

International Nuclear Information System (INIS)

Kubo, Y.; Gatel, C.; Snoeck, E.; Houdellier, F.

2017-01-01

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

Ab initio study on electron excitation and electron transfer in tryptophan-tyrosine system

International Nuclear Information System (INIS)

Tong Jing; Li Xiangyuan

2002-01-01

In this article, ab initio calculation has been performed to evaluate the transition energy of electronic excitation in tryptophan and tyrosine by using semiempirical molecular orbital method AM1 and complete active space self-consistent field method. The solvent effect has been considered by means of the conductor-like screening model. After geometric optimizations of isolated tryptophan and tyrosine, and their corresponding radicals and cations, reaction heat of these electron transfer reactions have been obtained by the means of complete active space self-consistent field method. The transition energies from the ground state, respectively, to the lowest excited state and to the lowest triplet state of these two amino acids are also calculated and compared with the experimentally observed values. The ionization potential and electron affinity are also calculated for tryptophan and tyrosine employing Koopmans' theorem and ab initio calculation. Compared with the experimental measurements, the theoretical results are found satisfactory. Theoretical results give good explanations on the experimental phenomena that N 3 · can preferably oxide the side chain of tryptophan residue and then the electron transfer from tyrosine residue to tryptophan residue follows in peptides involving tryptophan and tyrosine

Absolute cross sections from the ''boomerang model'' for resonant electron-molecule scattering

International Nuclear Information System (INIS)

Dube, L.; Herzenberg, A.

1979-01-01

The boomerang model is used to calculate absolute cross sections near the 2 Pi/sub g/ shape resonance in e-N 2 scattering. The calculated cross sections are shown to satisfy detailed balancing. The exchange of electrons is taken into account. A parametrized complex-potential curve for the intermediate N 2 /sup ts-/ ion is determined from a small part of the experimental data, and then used to calculate other properties. The calculations are in good agreement with the absolute cross sections for vibrational excitation from the ground state, the absolute cross section v = 1 → 2, and the absolute total cross section

Experimental studies of thermal and non-thermal electron cyclotron phenomena in tokamaks

International Nuclear Information System (INIS)

McDermott, F.S.

1984-12-01

A direct measurement of wave absorption in the ISX-B tokamak at the second harmonic of the electron cyclotron frequency is reported. Measurements of the absorption of a wave polarized in the extraordinary mode and propagating perpendicular to the toroidal magnetic field are in agreement with the absorption predicted by the linearized Vlasov equation for a thermal plasma. Agreement is found both for an analytic approximation to the wave absorption and for a numerical simulation of ray propagation in toroidal geometry. Observations are also reported on a non-linear, three-wave interaction process occurring during high power electron cyclotron resonance heating in the Versator II tokamak. The measured spectra and the threshold power are consistent with a model in which the incident power in the extraordinary mode of polarization decays at the upper hybrid resonance layer into a lower hybrid wave and an electron Bernstein wave. Finally, measurements of non-thermal emission at the second harmonic of the electron cyclotron frequency and below the electron plasma frequency are reported from low density, non-Maxwellian plasma in the Versator II tokamak. The emission spectra are in agreement with a model in which waves are driven unstable at the anomalous Doppler resonance, while only weakly damped at the Cerenkov resonance

First-principles calculations, experimental study, and thermodynamic modeling of the Al-Co-Cr system.

Directory of Open Access Journals (Sweden)

Xuan L Liu

Full Text Available The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT and phase-equilibria experiments that led to X-ray diffraction (XRD and electron probe micro-analysis (EPMA measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS calculations predict a large bcc-A2 (disordered/B2 (ordered miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings.

Quasi-linear analysis of the extraordinary electron wave destabilized by runaway electrons

Energy Technology Data Exchange (ETDEWEB)

Pokol, G. I.; Kómár, A.; Budai, A. [Department of Nuclear Techniques, Budapest University of Technology and Economics, Budapest (Hungary); Stahl, A.; Fülöp, T. [Department of Applied Physics, Chalmers University of Technology, Göteborg (Sweden)

2014-10-15

Runaway electrons with strongly anisotropic distributions present in post-disruption tokamak plasmas can destabilize the extraordinary electron (EXEL) wave. The present work investigates the dynamics of the quasi-linear evolution of the EXEL instability for a range of different plasma parameters using a model runaway distribution function valid for highly relativistic runaway electron beams produced primarily by the avalanche process. Simulations show a rapid pitch-angle scattering of the runaway electrons in the high energy tail on the 100–1000 μs time scale. Due to the wave-particle interaction, a modification to the synchrotron radiation spectrum emitted by the runaway electron population is foreseen, exposing a possible experimental detection method for such an interaction.

Participation to the development of a kinetic model for the energy transport and deposition by using a fast electron beam in solid targets

International Nuclear Information System (INIS)

Hadj-Bachir, Mokrane

2012-06-01

Whereas existing codes (PIC, hybrid or kinetic) used to model electron transport by describing experimentally observed physical phenomena at different time scales and space scales are notably time and memory consuming (from several hours to several days of computing time), this academic work aimed at developing, from an existing code, a simple and quasi analytical model of transport of fast electron in intense current. This model allows the calculation of energy losses of beam electrons, as well as the heating a materials crossed within a relatively short time (about a minute), with ranges of about 100 microns and a resolution of about 1 micron. After a recall on the theory of fast electron transport, the author presents the structure of the code as it existed before this improvement work, and then the introduced modifications which addressed electronic conductivity, the collisional stopping power, and the distribution function. Obtained results are finally discussed

Optimizing the Diffusion Welding Process for Alloy 800H: Thermodynamic, Diffusion Modeling, and Experimental Work

International Nuclear Information System (INIS)

Mizia, R.E.; Clark, D.E.; Glazoff, M.V.; Lister, Tedd E.; Trowbridge, T.L.

2011-01-01

A research effort was made to evaluate the usefulness of modern thermodynamic and diffusion computational tools, Thermo-Calc(copyright) and Dictra(copyright), in optimizing the parameters for diffusion welding of Alloy 800H. This would achieve a substantial reduction in the overall number of experiments required to achieve optimal welding and post-weld heat treatment conditions. This problem is important because diffusion welded components of Alloy 800H are being evaluated for use in assembling compact, micro-channel heat exchangers that are being proposed in the design of a high temperature gas-cooled reactor by the US Department of Energy. The modeling was done in close contact with experimental work. The latter included using the Gleeble 3500 System(reg sign) for welding simulation, mechanical property measurement, and light optical and Scanning Electron Microscopy. The modeling efforts suggested a temperature of 1150 C for 1 hour with an applied pressure of 5 MPa using a 15 μm Ni foil as a joint filler to reduce chromium oxidation on the welded surfaces. Good agreement between modeled and experimentally determined concentration gradients was achieved, and model refinements to account for the complexity of actual alloy materials are suggested.

Status of Galileo interim radiation electron model

Science.gov (United States)

Garrett, H. B.; Jun, I.; Ratliff, J. M.; Evans, R. W.; Clough, G. A.; McEntire, R. W.

2003-01-01

Measurements of the high energy, omni-directional electron environment by the Galileo spacecraft Energetic Particle Detector (EDP) were used to develop a new model of Jupiter's trapped electron radiation in the jovian equatorial plane for the range 8 to 16 Jupiter radii.

An analytic current-voltage model for quasi-ballistic III-nitride high electron mobility transistors

Science.gov (United States)

Li, Kexin; Rakheja, Shaloo

2018-05-01

We present an analytic model to describe the DC current-voltage (I-V) relationship in scaled III-nitride high electron mobility transistors (HEMTs) in which transport within the channel is quasi-ballistic in nature. Following Landauer's transport theory and charge calculation based on two-dimensional electrostatics that incorporates negative momenta states from the drain terminal, an analytic expression for current as a function of terminal voltages is developed. The model interprets the non-linearity of access regions in non-self-aligned HEMTs. Effects of Joule heating with temperature-dependent thermal conductivity are incorporated in the model in a self-consistent manner. With a total of 26 input parameters, the analytic model offers reduced empiricism compared to existing GaN HEMT models. To verify the model, experimental I-V data of InAlN/GaN with InGaN back-barrier HEMTs with channel lengths of 42 and 105 nm are considered. Additionally, the model is validated against numerical I-V data obtained from DC hydrodynamic simulations of an unintentionally doped AlGaN-on-GaN HEMT with 50-nm gate length. The model is also verified against pulsed I-V measurements of a 150-nm T-gate GaN HEMT. Excellent agreement between the model and experimental and numerical results for output current, transconductance, and output conductance is demonstrated over a broad range of bias and temperature conditions.

Experimental Modeling of Dynamic Systems

DEFF Research Database (Denmark)

Knudsen, Morten Haack

2006-01-01

An engineering course, Simulation and Experimental Modeling, has been developed that is based on a method for direct estimation of physical parameters in dynamic systems. Compared with classical system identification, the method appears to be easier to understand, apply, and combine with physical...

Simulation of electron thermal transport in H-mode discharges

International Nuclear Information System (INIS)

Rafiq, T.; Pankin, A. Y.; Bateman, G.; Kritz, A. H.; Halpern, F. D.

2009-01-01

Electron thermal transport in DIII-D H-mode tokamak plasmas [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] is investigated by comparing predictive simulation results for the evolution of electron temperature profiles with experimental data. The comparison includes the entire profile from the magnetic axis to the bottom of the pedestal. In the simulations, carried out using the automated system for transport analysis (ASTRA) integrated modeling code, different combinations of electron thermal transport models are considered. The combinations include models for electron temperature gradient (ETG) anomalous transport and trapped electron mode (TEM) anomalous transport, as well as a model for paleoclassical transport [J. D. Callen, Nucl. Fusion 45, 1120 (2005)]. It is found that the electromagnetic limit of the Horton ETG model [W. Horton et al., Phys. Fluids 31, 2971 (1988)] provides an important contribution near the magnetic axis, which is a region where the ETG mode in the GLF23 model [R. E. Waltz et al., Phys. Plasmas 4, 2482 (1997)] is below threshold. In simulations of DIII-D discharges, the observed shape of the H-mode edge pedestal is produced when transport associated with the TEM component of the GLF23 model is suppressed and transport given by the paleoclassical model is included. In a study involving 15 DIII-D H-mode discharges, it is found that with a particular combination of electron thermal transport models, the average rms deviation of the predicted electron temperature profile from the experimental profile is reduced to 9% and the offset to -4%.

A theory of local and global processes which affect solar wind electrons. 2. Experimental support

International Nuclear Information System (INIS)

Scudder, J.D.; Olbert, S.

1979-05-01

The microscopic characteristics of the Coulomb cross section show that there are three natural subpopulations for plasma electrons: the subthermals; the transthermals; and the extrathermals. Data from three experimental groups on three different spacecraft in the interplanetary medium over a radial range are presented to support the five interrelations projected between solar wind electron properties and changes in the interplanetary medium: (1) subthermals respond primarily to local changes (compression and rarefactions) in stream dynamics; (2) the extrathermal fraction of the ambient electron density should be anti-correlated with the asymptotic bulk speed; (3) the extrathermal 'temperature' should be anti-correlated with the local wind speed at 1 AU; (4) the heat flux carried by electrons should be anti-correlated with the local bulk speed; and (5) the extrathermal differential 'temperature' should be nearly independent of radius within 1 AU

Modeling electron beam parameters and plasma interface position in an anode plasma electron gun with hydrogen atmosphere

Science.gov (United States)

Krauze, A.; Virbulis, J.; Kravtsov, A.

2018-05-01

A beam glow discharge based electron gun can be applied as heater for silicon crystal growth systems in which silicon rods are pulled from melt. Impacts of high-energy charged particles cause wear and tear of the gun and generate an additional source of silicon contamination. A steady-state model for electron beam formation has been developed to model the electron gun and optimize its design. Description of the model and first simulation results are presented. It has been shown that the model can simulate dimensions of particle impact areas on the cathode and anode, but further improvements of the model are needed to correctly simulate electron trajectory distribution in the beam and the beam current dependence on the applied gas pressure.

Modeling the Nab Experiment Electronics in SPICE

Science.gov (United States)

Blose, Alexander; Crawford, Christopher; Sprow, Aaron; Nab Collaboration

2017-09-01

The goal of the Nab experiment is to measure the neutron decay coefficients a, the electron-neutrino correlation, as well as b, the Fierz interference term to precisely test the Standard Model, as well as probe for Beyond the Standard Model physics. In this experiment, protons from the beta decay of the neutron are guided through a magnetic field into a Silicon detector. Event reconstruction will be achieved via time-of-flight measurement for the proton and direct measurement of the coincident electron energy in highly segmented silicon detectors, so the amplification circuitry needs to preserve fast timing, provide good amplitude resolution, and be packaged in a high-density format. We have designed a SPICE simulation to model the full electronics chain for the Nab experiment in order to understand the contributions of each stage and optimize them for performance. Additionally, analytic solutions to each of the components have been determined where available. We will present a comparison of the output from the SPICE model, analytic solution, and empirically determined data.

Experimental results from a DC photocathode electron gun for an IR FEL

International Nuclear Information System (INIS)

Kehne, D.; Engwall, D.; Legg, R.; Shinn, M.

1997-01-01

A 350 keV DC photocathode gun capable of delivering the high-brightness CW electron beam necessary for Jefferson Lab's infrared free-electron laser is described. The gun is to be used with a superconducting radiofrequency linac operating at 1.497 GHz and is mode-locked to the 40th subharmonic of the fundamental using a Nd:YLF drive laser. The gun provides 20--25 ps bunches at up to 135 pC/bunch. Experimental measurements of transverse and longitudinal beam properties are presented. Transverse emittance is measured using a slit-wire scanner emittance meter, and energy spread is measured using the slit and a spectrometer magnet. Longitudinal emittance is measured using a combination of sampling aperture, kicker cavity, slit and spectrometer. Measurements for bunch charges of 135 pC are described and compared with simulations

SU-F-T-74: Experimental Validation of Monaco Electron Monte Carlo Dose Calculation for Small Fields

International Nuclear Information System (INIS)

Varadhan; Way, S; Arentsen, L; Gerbi, B

2016-01-01

Purpose: To verify experimentally the accuracy of Monaco (Elekta) electron Monte Carlo (eMC) algorithm to calculate small field size depth doses, monitor units and isodose distributions. Methods: Beam modeling of eMC algorithm was performed for electron energies of 6, 9, 12 15 and 18 Mev for a Elekta Infinity Linac and all available ( 6, 10, 14 20 and 25 cone) applicator sizes. Electron cutouts of incrementally smaller field sizes (20, 40, 60 and 80% blocked from open cone) were fabricated. Dose calculation was performed using a grid size smaller than one-tenth of the R_8_0_–_2_0 electron distal falloff distance and number of particle histories was set at 500,000 per cm"2. Percent depth dose scans and beam profiles at dmax, d_9_0 and d_8_0 depths were measured for each cutout and energy with Wellhoffer (IBA) Blue Phantom"2 scanning system and compared against eMC calculated doses. Results: The measured dose and output factors of incrementally reduced cutout sizes (to 3cm diameter) agreed with eMC calculated doses within ± 2.5%. The profile comparisons at dmax, d_9_0 and d_8_0 depths and percent depth doses at reduced field sizes agreed within 2.5% or 2mm. Conclusion: Our results indicate that the Monaco eMC algorithm can accurately predict depth doses, isodose distributions, and monitor units in homogeneous water phantom for field sizes as small as 3.0 cm diameter for energies in the 6 to 18 MeV range at 100 cm SSD. Consequently, the old rule of thumb to approximate limiting cutout size for an electron field determined by the lateral scatter equilibrium (E (MeV)/2.5 in centimeters of water) does not apply to Monaco eMC algorithm.

SU-F-T-74: Experimental Validation of Monaco Electron Monte Carlo Dose Calculation for Small Fields

Energy Technology Data Exchange (ETDEWEB)

Varadhan [Minneapolis Radiation Oncology, Fridley, MN (United States); Way, S [Minneapolis Radiation Oncology, Robbinsdale, MN (United States); Arentsen, L; Gerbi, B [University of Minnesota, Minneapolis, MN (United States)

2016-06-15

Purpose: To verify experimentally the accuracy of Monaco (Elekta) electron Monte Carlo (eMC) algorithm to calculate small field size depth doses, monitor units and isodose distributions. Methods: Beam modeling of eMC algorithm was performed for electron energies of 6, 9, 12 15 and 18 Mev for a Elekta Infinity Linac and all available ( 6, 10, 14 20 and 25 cone) applicator sizes. Electron cutouts of incrementally smaller field sizes (20, 40, 60 and 80% blocked from open cone) were fabricated. Dose calculation was performed using a grid size smaller than one-tenth of the R{sub 80–20} electron distal falloff distance and number of particle histories was set at 500,000 per cm{sup 2}. Percent depth dose scans and beam profiles at dmax, d{sub 90} and d{sub 80} depths were measured for each cutout and energy with Wellhoffer (IBA) Blue Phantom{sup 2} scanning system and compared against eMC calculated doses. Results: The measured dose and output factors of incrementally reduced cutout sizes (to 3cm diameter) agreed with eMC calculated doses within ± 2.5%. The profile comparisons at dmax, d{sub 90} and d{sub 80} depths and percent depth doses at reduced field sizes agreed within 2.5% or 2mm. Conclusion: Our results indicate that the Monaco eMC algorithm can accurately predict depth doses, isodose distributions, and monitor units in homogeneous water phantom for field sizes as small as 3.0 cm diameter for energies in the 6 to 18 MeV range at 100 cm SSD. Consequently, the old rule of thumb to approximate limiting cutout size for an electron field determined by the lateral scatter equilibrium (E (MeV)/2.5 in centimeters of water) does not apply to Monaco eMC algorithm.

Modeling of Jupiter's electron an ion radiation belts

International Nuclear Information System (INIS)

Sicard, Angelica

2004-01-01

In the Fifties, James Van Allen showed the existence of regions of the terrestrial magnetosphere consisted of energetic particles, trapped by the magnetic field: the radiation belts. The radiation belts of the Earth were the subject of many modeling works and are studied since several years at the Departement Environnement Spatial (DESP) of ONERA. In 1998, the DESP decided to adapt the radiation belts model of the Earth, Salammbo, to radiation environment of Jupiter. A first thesis was thus carried out on the subject and a first radiation belts model of electrons of Jupiter was developed [Santos-Costa, 2001]. The aim of this second thesis is to develop a radiation belts model for protons and heavy ions. In order to validate the developed model, the comparisons between Salammbo results and observations are essential. However, the validation is difficult in the case of protons and heavy ions because in-situ measurements of the probes are very few and most of the time contaminated by very energetic electrons. To solve this problem, a very good model of electrons radiation belts is essential to confirm or cancel the contamination of protons and heavy ions measurements. Thus, in parallel to the development of the protons and heavy ions radiation belts model, the electrons models, already existing, has been improved. Then Salammbo results have been compared to the different observations available (in-situ measurements, radio-astronomical observations). The different comparisons show a very good agreement between Salammbo results and observations. (author) [fr

Electronic and magnetic properties of the [Ni(salophen]: An experimental and DFT study

Directory of Open Access Journals (Sweden)

Rodrigo A. Mendes

2018-01-01

Full Text Available The effect of the coordination of a Ni(II ion on the electronic and magnetic properties of the ligand salophen were experimentally and theoretically evaluated. The complex [Ni(salophen] was synthesized and characterized through FTIR and an elemental analysis. Spectral data obtained using DMSO as a solvent showed that the ligand absorption profile was significantly disturbed after the coordination of the metal atom. In addition to a redshift of the salophen ligand absorption bands, mainly composed by π → π∗electronic transitions, additional bands of around 470 nm were observed, resulting in a partial metal-to-ligand charge transfer. Furthermore, a significant increment of its band intensities was observed, favoring a more intense absorption in a broader range of the visible spectrum, which is a desired characteristic for applications in the field of organic electronics. This finding is related to an increment of the planarity and consequent electron delocalization of the macrocycle in the complex, which was estimated by the calculation of the current strengths at the PBE0/cc-pVTZ (Dyall.v3z for Ni(II level.

Experimental modeling of swirl flows in power plants

Science.gov (United States)

Shtork, S. I.; Litvinov, I. V.; Gesheva, E. S.; Tsoy, M. A.; Skripkin, S. G.

2018-03-01

The article presents an overview of the methods and approaches to experimental modeling of various thermal and hydropower units - furnaces of pulverized coal boilers and flow-through elements of hydro turbines. The presented modeling approaches based on a combination of experimentation and rapid prototyping of working parts may be useful in optimizing energy equipment to improve safety and efficiency of industrial energy systems.

Electronic field emission models beyond the Fowler-Nordheim one

Science.gov (United States)

Lepetit, Bruno

2017-12-01

We propose several quantum mechanical models to describe electronic field emission from first principles. These models allow us to correlate quantitatively the electronic emission current with the electrode surface details at the atomic scale. They all rely on electronic potential energy surfaces obtained from three dimensional density functional theory calculations. They differ by the various quantum mechanical methods (exact or perturbative, time dependent or time independent), which are used to describe tunneling through the electronic potential energy barrier. Comparison of these models between them and with the standard Fowler-Nordheim one in the context of one dimensional tunneling allows us to assess the impact on the accuracy of the computed current of the approximations made in each model. Among these methods, the time dependent perturbative one provides a well-balanced trade-off between accuracy and computational cost.

Pseudogap in the Eliashberg approach based on electron-phonon and electron-electron-phonon interaction

Energy Technology Data Exchange (ETDEWEB)

Szczesniak, R. [Institute of Physics, Czestochowa University of Technology (Poland); Institute of Physics, Jan Dlugosz University in Czestochowa (Poland); Durajski, A.P.; Duda, A.M. [Institute of Physics, Czestochowa University of Technology (Poland)

2017-04-15

The properties of the superconducting and the anomalous normal state were described by using the Eliashberg method. The pairing mechanism was reproduced with the help of the Hamiltonian, which models the electron-phonon and the electron-electron-phonon interaction (EEPh). The set of the Eliashberg equations, which determines the order parameter function (φ), the wave function renormalization factor (Z), and the energy shift function (χ), was derived. It was proven that for the sufficiently large values of the EEPh potential, the doping dependence of the order parameter (φ/Z) has the analogous course to that observed experimentally in cuprates. The energy gap in the electron density of states is induced by Z and χ - the contribution from φ is negligible. The electron density of states possesses the characteristic asymmetric form and the pseudogap is observed above the critical temperature. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Simple and universal model for electron-impact ionization of complex biomolecules

Science.gov (United States)

Tan, Hong Qi; Mi, Zhaohong; Bettiol, Andrew A.

2018-03-01

We present a simple and universal approach to calculate the total ionization cross section (TICS) for electron impact ionization in DNA bases and other biomaterials in the condensed phase. Evaluating the electron impact TICS plays a vital role in ion-beam radiobiology simulation at the cellular level, as secondary electrons are the main cause of DNA damage in particle cancer therapy. Our method is based on extending the dielectric formalism. The calculated results agree well with experimental data and show a good comparison with other theoretical calculations. This method only requires information of the chemical composition and density and an estimate of the mean binding energy to produce reasonably accurate TICS of complex biomolecules. Because of its simplicity and great predictive effectiveness, this method could be helpful in situations where the experimental TICS data are absent or scarce, such as in particle cancer therapy.

Experimental observation of the improvement in MTF from backthinning a CMOS direct electron detector

International Nuclear Information System (INIS)

McMullan, G.; Faruqi, A.R.; Henderson, R.; Guerrini, N.; Turchetta, R.; Jacobs, A.; Hoften, G. van

2009-01-01

The advantages of backthinning monolithic active pixel sensors (MAPS) based on complementary metal oxide semiconductor (CMOS) direct electron detectors for electron microscopy have been discussed previously; they include better spatial resolution (modulation transfer function or MTF) and efficiency at all spatial frequencies (detective quantum efficiency or DQE). It was suggested that a 'thin' CMOS detector would have the most outstanding properties because of a reduction in the proportion of backscattered electrons. In this paper we show, theoretically (using Monte Carlo simulations of electron trajectories) and experimentally that this is indeed the case. The modulation transfer functions of prototype backthinned CMOS direct electron detectors have been measured at 300 keV. At zero spatial frequency, in non-backthinned 700-μm-thick detectors, the backscattered component makes up over 40% of the total signal but, by backthinning to 100, 50 or 35 μm, this can be reduced to 25%, 15% and 10%, respectively. For the 35 μm backthinned detector, this reduction in backscatter increases the MTF by 40% for spatial frequencies between 0.1 and 1.0 Nyquist. As discussed in the main text, reducing backscattering in backthinned detectors should also improve DQE.

Electron-ion correlation effects in ion-atom single ionization

Energy Technology Data Exchange (ETDEWEB)

Colavecchia, F.D.; Garibotti, C.R. [Centro Atomico Bariloche and Consejo Nacional de Investigaciones Cientificas y Tecnicas, 8400 San Carlos de Bariloche (Argentina); Gasaneo, G. [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

2000-06-28

We study the effect of electron-ion correlation in single ionization processes of atoms by ion impact. We present a distorted wave model where the final state is represented by a correlated function solution of a non-separable three-body continuum Hamiltonian, that includes electron-ion correlation as coupling terms of the wave equation. A comparison of the electronic differential cross sections computed with this model with other theories and experimental data reveals that the influence of the electron-ion correlation is more significant for low energy emitted electrons. (author). Letter-to-the-editor.

Electron transport in nanometer GaAs structure under radiation exposure

CERN Document Server

Demarina, N V

2002-01-01

One investigates into effect of neutron and proton irradiation on electron transport in nanometer GaAs structures. Mathematical model takes account of radiation defects via introduction of additional mechanisms od scattering of carriers at point defects and disordered regions. To investigate experimentally into volt-ampere and volt-farad characteristics one used a structure based on a field-effect transistor with the Schottky gate and a built-in channel. Calculation results of electron mobility, drift rate of electrons, time of energy relaxation and electron pulse are compared with the experimental data

Optical conductivity calculation of a k.p model semiconductor GaAs incorporating first-order electron-hole vertex correction

Science.gov (United States)

Nurhuda, Maryam; Aziz Majidi, Muhammad

2018-04-01

The role of excitons in semiconducting materials carries potential applications. Experimental results show that excitonic signals also appear in optical absorption spectra of semiconductor system with narrow gap, such as Gallium Arsenide (GaAs). While on the theoretical side, calculation of optical spectra based purely on Density Functional Theory (DFT) without taking electron-hole (e-h) interactions into account does not lead to the appearance of any excitonic signal. Meanwhile, existing DFT-based algorithms that include a full vertex correction through Bethe-Salpeter equation may reveal an excitonic signal, but the algorithm has not provided a way to analyze the excitonic signal further. Motivated to provide a way to isolate the excitonic effect in the optical response theoretically, we develop a method of calculation for the optical conductivity of a narrow band-gap semiconductor GaAs within the 8-band k.p model that includes electron-hole interactions through first-order electron-hole vertex correction. Our calculation confirms that the first-order e-h vertex correction reveals excitonic signal around 1.5 eV (the band gap edge), consistent with the experimental data.

An Electronic Publishing Model for Academic Publishers.

Science.gov (United States)

Gold, Jon D.

1994-01-01

Describes an electronic publishing model based on Standard Generalized Markup Language (SGML) and considers its use by an academic publisher. Highlights include how SGML is used to produce an electronic book, hypertext, methods of delivery, intellectual property rights, and future possibilities. Sample documents are included. (two references) (LRW)

The experimental electron mean-free-path in Si under typical (S)TEM conditions

International Nuclear Information System (INIS)

Potapov, P.L.

2014-01-01

The electron mean-free-path in Si was measured by EELS using the test structure with the certified dimensions as a calibration standard. In a good agreement with the previous CBED measurements, the mean-free-path is 150 nm for 200 keV and 179 nm for 300 keV energy of primary electrons at large collection angles. These values are accurately predicted by the model of Iakoubovskii et al. while the model of Malis et al. incorporated in common microscopy software underestimates the mean-free-path by 15% at least. Correspondingly, the thickness of TEM samples reported in many studies of the Si-based materials last decades might be noticeably underestimated. - Highlights: • The electron inelastic mean-free-path in Si is measured for the typical (S)TEM conditions. • These reference values allow for accurate determination of the lamella thickness by EELS. • The theoretical model by Malis et al. underestimates the mean-free-path values

Experimental modeling of injectivity loss; Modelagem experimental da perda de injetividade

Energy Technology Data Exchange (ETDEWEB)

Bonato, Adriano Jose do Amaral Mello; Silva, Pedro Glauto de Farias e; Gomes, Vanessa Limeira Azevedo; Santos, Adriano dos [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

2012-07-01

Produced water reinjection, suspended particles are retained in the porous media causing formation damage and injectivity decline. In general the retention of the particles occurs near the side of injection, this fact occurs in most cases, due to the size exclusion. The modeling of filtration and the consequent formation damage is essential to the project management of water injection in oil reservoirs. Thus, mathematical models are studied to better predict the distribution of particles throughout the porous media and determine the parameters of adjustment to injectivity decline. Among these models, there is the classic model which consists in determining these parameters (coefficient of filtration and formation damage). The methodology used in modeling is given from the equations the mass conservation, kinetic particle retention, the modified Darcy equation and the function formation damage. This study aimed to improve experimental modeling, including development of software for acquisition and processing of experimental data, considering the variable number of pressure measurements along the sample. The software was developed using the Labview 2011 platform and allows the determination of relevant parameters to predict injectivity loss in water injection wells. Furthermore, based on the traditional model of filtration in porous media (including depth filtration and formation of the external plaster), the software was applied to predict injectivity loss in addition to the properties of the grout. Finally, the classical models for transporting suspensions and damage to the formation were observed. (author)

Developing a model for application of electronic banking based on electronic trust

Directory of Open Access Journals (Sweden)

Amir Hooshang Nazarpoori

2014-05-01

Full Text Available This study develops a model for application of electronic banking based on electronic trust among costumers of Day bank in KhoramAbad city. A sample of 150 people was selected based on stratified random sampling. Questionnaires were used for the investigation. Results indicate that technology-based factors, user-based factors, and trust had negative relationships with perceived risk types including financial, functional, personal, and private. Moreover, trust including trust in system and trust in bank had a positive relationship with tendency to use and real application of electronic banking.

Experimental electron density studies as key for understanding the chemical and physical properties in selected model systems; Experimentelle Elektronendichtestudien als Schluessel zum Verstaendnis chemischer und physikalischer Eigenschaften in ausgewaehlten Modellsystemen

Energy Technology Data Exchange (ETDEWEB)

Hauf, Christoph

2014-12-17

The topological analysis of experimentally determined electron density distributions, employing the quantum theory of atoms in molecules developed by Richard FW Bader, was used in this thesis to study chemically or physically motivated questions in appropriate model systems. First, transition metal complexes with activated C-H bonds or Si-H bonds were examined which led to a better understanding of agostic interactions. An important tool during these investigations is the so called atomic graph, which describes the characteristic spatial arrangement of the critical points of the Laplacefield of the electron density distribution in the valence shell of the relevant atoms. It reveals zones with a locally concentrated or depleted electron density distribution. This leads to the empirical rule, that a strong activation of C-H bonds or Si-H bonds is only observed when the hydrogen atom faces a pronounced charge depletion zone at the transition metal atom. In addition, the quasi one-dimensional rare-earth transition metal carbides Sc{sub 3}FeC{sub 4}, Sc{sub 3}CoC{sub 4} and Sc{sub 3}NiC{sub 4} were examined. Although all three compounds are isotypic at room temperature, it was revealed during this thesis, that only Sc{sub 3}CoC{sub 4} undergoes a structural phase transition at a temperature of ∝ 70 K and becomes superconducting below a critical temperature of 4.5 K. The main reason for this behaviour is the variation of the valence electrons through the exchange of Fe by Co or Ni. This results in the occupation of progressively higher energy electronic states and a raising of the Fermi level. The change in the nature of the electronic states at the Fermi level is in turn reflected by the different atomic graphs of the transition metal atoms and the distinct physical properties of these three compounds.

Status of the Galileo interim radiation electron model

Science.gov (United States)

Garrett, H. B.; Jun, I.; Ratliff, J. M.; Evans, R. W.; Clough, G. A.; McEntire, R. W.

2003-04-01

Measurements of the high energy, omni-directional electron environment by the Galileo spacecraft Energetic Particle Detector (EPD) were used to develop a new model of Jupiter's trapped electron radiation in the jovian equatorial plane for the range 8 to 16 Jupiter radii (1 jovian radius = 71,400 km). 10-minute averages of these data formed an extensive database of observations of the jovian radiation belts between Jupiter orbit insertion (JOI) in 1995 and 2002. These data were then averaged to provide a differential flux spectrum at 0.174, 0.304, 0.527, 1.5, 2.0, 11.0, and 31 MeV in the jovian equatorial plane as a function of radial distance. This omni-directional, equatorial model was combined with the original Divine model of jovian electron radiation to yield estimates of the out-of-plane radiation environment. That model, referred to here as the Galileo Interim Radiation Electron (or GIRE) model, was then used to calculate the Europa mission dose for an average and a 1-sigma worst-case situation. The prediction of the GIRE model is about a factor of 2 lower than the Divine model estimate over the range of 100 to 1000 mils (2.54 to 25.4 mm) of aluminum shielding, but exceeds the Divine model by about 50% for thicker shielding. The model, the steps leading to its creation, and relevant issues and concerns are discussed. While work remains to be done, the GIRE model clearly represents a significant step forward in the study of the jovian radiation environment, and it is a useful and valuable tool for estimating that environment for future space missions.

Endogenous opioid antagonism in physiological experimental pain models

DEFF Research Database (Denmark)

Werner, Mads U; Pereira, Manuel P; Andersen, Lars Peter H

2015-01-01

hyperalgesia models (6 studies), 'pain' models (25 studies), summation models (2 studies), nociceptive reflex models (3 studies) and miscellaneous models (2 studies). A consistent reversal of analgesia by a MOR-antagonist was demonstrated in 10 of the 25 ITP-studies, including stress-induced analgesia and r...... ratings, threshold assessments and somatosensory evoked potentials (SSEP), did not appear consistent in 28 out of 32 'pain' model studies. In conclusion, only in 2 experimental human pain models, i.e., stress-induced analgesia and rTMS, administration of MOR-antagonist demonstrated a consistent effect......Opioid antagonists are pharmacological tools applied as an indirect measure to detect activation of the endogenous opioid system (EOS) in experimental pain models. The objective of this systematic review was to examine the effect of mu-opioid-receptor (MOR) antagonists in placebo-controlled, double...

EXPERIMENTAL MODEL OF THE PRIMARY MALE HYPOGONADISM

Directory of Open Access Journals (Sweden)

P. A. Kulikova

2014-01-01

Full Text Available Background: Development of the new methods of treatment of primary male hypogonadism is an urgent medical problem. Its solution requires a suitable experimental model of the disease. Aim: The creation of new experimental model of primary male hypogonadism. Materials and methods: The study was conducted on the male Wistar rats, hypogonadism was modeled by temporary ligation of the distal part of the spermatic cord. Results: It was shown that three-day ligation of the spermatic cord led to persistent disturbance of the testosterone-producing and reproductive functions. These manifestations were reversible at shorter duration of the exposure. Conclusion: The created model of primary male hypogonadism is characterized by the persistent testosterone-producing and reproductive functions disturbance, technical availability, non-toxicity to the other organs and systems. Availability of the model provides new opportunities for the development of approaches to treating diseases of the reproductive organs in men.

Understanding Leadership: An Experimental-Experiential Model

Science.gov (United States)

Hole, George T.

2014-01-01

Books about leadership are dangerous to readers who fantasize about being leaders or apply leadership ideas as if they were proven formulas. As an antidote, I offer an experimental framework in which any leadership-management model can be tested to gain experiential understanding of the model. As a result one can gain reality-based insights about…

Experimental Verification of the Transient Model in an Enrichment Circuit

International Nuclear Information System (INIS)

Fernandino, Maria; Brasnarof, Daniel; Delmastro, Dario

2003-01-01

In the present work an experimental closed loop representing a single stage of an uranium gaseous diffusion enrichment cascade is described, loop that is used to experimentally validate an analytical model that describes the dynamics inside such a loop.The conditions established inside the experimental loop after a few working hours were reproduced by the analytical model, leaving the slower thermal phenomena taking place for future studies.Two kinds of perturbations were experimentally introduced: a change in the range of operation of one of the compressors and the addition of mass into the loop.Numerical and experimental results are compared and presented in this work. The analytical model proposed was verified against these two changes, with very good agreement in the time response and measured values.This analytical model allows us to determine the characteristic time response of the system

Application of catastrophe theory to a point model for bumpy torus with neoclassical non-resonant electrons

Energy Technology Data Exchange (ETDEWEB)

Punjabi, A; Vahala, G [College of William and Mary, Williamsburg, VA (USA). Dept. of Physics

1983-12-01

The point model for the toroidal core plasma in the ELMO Bumpy Torus (with neoclassical non-resonant electrons) is examined in the light of catastrophe theory. Even though the point model equations do not constitute a gradient dynamic system, the equilibrium surfaces are similar to those of the canonical cusp catastrophe. The point model is then extended to incorporate ion cyclotron resonance heating. A detailed parametric study of the equilibria is presented. Further, the nonlinear time evolution of these equilibria is studied, and it is observed that the point model obeys the delay convention (and hence hysteresis) and shows catastrophes at the fold edges of the equilibrium surfaces. Tentative applications are made to experimental results.

EBIT (Electron Beam Ion Trap), N-Division Experimental Physics. Annual report, 1994

International Nuclear Information System (INIS)

Schneider, D.

1995-10-01

The experimental groups in the Electron Beam Ion Trap (EBIT) program continue to perform front-line research with trapped and extracted highly charged ions (HCI) in the areas of ion/surface interactions, atomic spectroscopy, electron-ion interaction and structure measurements, highly charged ion confinement, and EBIT development studies. The ion surface/interaction studies which were initiated five years ago have reached a stage where they an carry out routine investigations, as well as produce breakthrough results towards the development of novel nanotechnology. At EBIT and SuperEBIT studies of the x-ray emission from trapped ions continue to produce significant atomic structure data with high precision for few electron systems of high-Z ions. Furthermore, diagnostics development for magnetic and laser fusion, supporting research for the x-ray laser and weapons programs, and laboratory astrophysics experiments in support of NASA's astrophysics program are a continuing effort. The two-electron contributions to the binding energy of helium like ions were measured for the first time. The results are significant because their precision is an order of magnitude better than those of competing measurements at accelerators, and the novel technique isolates the energy corrections that are the most interesting. The RETRAP project which was initiated three years ago has reached a stage where trapping, confining and electronic cooling of HCI ions up to Th 80+ can be performed routinely. Measurements of the rates and cross sections for electron transfer from H 2 performed to determine the lifetime of HCI up to Xe q+ and Th q+ (35 ≤ q ≤ 80) have been studied at mean energies estimated to be ∼ 5 q eV. This combination of heavy ions with very high charges and very low energies is rare in nature, but may be encountered in planned fusion energy demonstration devices, in highly charged ion sources, or in certain astrophysical events

Experimental study of K-electron capture probability in the decay of {sup 111}In

Energy Technology Data Exchange (ETDEWEB)

Mishra, N.R.; Kalyani, V.D.M.L.; Maldhusudhana Rao, P.V.; Vara Prasad, N.V.; Chandrasekhar Rao, M.V.S.; Satyanarayana, G.; Sastry, D.L. [Visakhapatnam, Andhra Univ. (India). Swami Jnanananda Lab. for Nuclear Research; Chintalapudi, S.N. [Calcutt, Inter-Univ. Consortium for DAEW Facilities (India)

1998-03-01

The K-electron capture probability in the decay of {sup 111}In to the 416.64 keV level of the daughter nucleus {sup 111}Cd was measured to be 0.853 {+-}0.037 in agreement with the theoretical value 0.865. The experimental value is seen to be consistent with the mass prediction of the relationship due to Wapstra and Bos.

Single-electron tunneling in double-barrier nanostructures

International Nuclear Information System (INIS)

Goldman, V.J.; Su, B.; Cunningham, J.E.

1992-01-01

In this paper, the authors review experimental study of charge transport in nanometer double-barrier resonant tunneling devices. Heterostructure material is asymmetric: one barrier is substantially less transparent than the other. Resonant tunneling through size-quantized well states and single-electron charging of the well are thus largely separated in the two bias polarities. When the emitter barrier is more transparent than the collector barrier, electrons accumulate in the well; incremental electron occupation of the well is accompanied by Coulomb blockade leading to sharp steps of the tunneling current. When the emitter barrier is less transparent, the current reflects resonant tunneling of just one electron at a time through size-quantized well states; the current peaks and/or steps (depending on experimental parameters) appear in current-voltage characteristics. Magnetic field and temperature effects are also reviewed. Good agreement is achieved in comparison of many features of experimental data with simple theoretical models

Resonant tunneling of electrons in quantum wires

International Nuclear Information System (INIS)

Krive, I.V.; Shekhter, R.I.; Jonson, M.; Krive, I.V.

2010-01-01

We considered resonant electron tunneling in various nanostructures including single wall carbon nanotubes, molecular transistors and quantum wires formed in two-dimensional electron gas. The review starts with a textbook description of resonant tunneling of noninteracting electrons through a double-barrier structure. The effects of electron-electron interaction in sequential and resonant electron tunneling are studied by using Luttinger liquid model of electron transport in quantum wires. The experimental aspects of the problem (fabrication of quantum wires and transport measurements) are also considered. The influence of vibrational and electromechanical effects on resonant electron tunneling in molecular transistors is discussed.

Electronic properties of a biased graphene bilayer

International Nuclear Information System (INIS)

Castro, Eduardo V; Lopes dos Santos, J M B; Novoselov, K S; Morozov, S V; Geim, A K; Peres, N M R; Nilsson, Johan; Castro Neto, A H; Guinea, F

2010-01-01

We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its four-band and two-band continuum approximations, and the four-band model is shown to always be a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, made out of either SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point for understanding the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, such as the second-nearest-neighbour hopping energies t' (in-plane) and γ 4 (inter-layer), and the on-site energy Δ.

Measurement of the electron and ion temperatures by the x-ray imaging crystal spectrometer on joint Texas experimental tokamak

Energy Technology Data Exchange (ETDEWEB)

Yan, W.; Chen, Z. Y., E-mail: zychen@hust.edu.cn; Huang, D. W.; Tong, R. H.; Wang, S. Y.; Wei, Y. N.; Ma, T. K.; Zhuang, G. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan (China); Jin, W. [Center of Interface Dynamics for Sustainability, China Academy of Engineering Physics, Chengdu, Sichuan 610200 (China); Lee, S. G. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Shi, Y. J. [Department of Nuclear Engineering, Seoul National University, Seoul 08826 (Korea, Republic of)

2016-11-15

An x-ray imaging crystal spectrometer has been developed on joint Texas experimental tokamak for the measurement of electron and ion temperatures from the K{sub α} spectra of helium-like argon and its satellite lines. A two-dimensional multi-wire proportional counter has been applied to detect the spectra. The electron and ion temperatures have been obtained from the Voigt fitting with the spectra of helium-like argon ions. The profiles of electron and ion temperatures show the dependence on electron density in ohmic plasmas.

Models of experimental saccular aneurysms of carotid arteries in canine

International Nuclear Information System (INIS)

Zhang Haixia; Cheng Yingsheng; Li Minghua

2006-01-01

Objective: To study the availability by making experimental saccular aneurysm models of carotid arteries in canine similar to human intracranial aneurysms. Methods: Twenty healthy canines with experimental saccular side-wall aneurysms of carotid arteries were created successfully by surgery. Results: Forty experimental saccular side-wall aneurysms of carotid arteries were created successfully with 36 aneurysms and parent arteries maintaining patency with each other and four spontaneously occluded confirmed by angiography. Model successful rate reached 90%. Conclusions: Experimental saccular side-wall aneurysms of carotid arteries in canines were one of best models created for simulating human intracranial aneurysms. (authors)

A sEMG model with experimentally based simulation parameters.

Science.gov (United States)

Wheeler, Katherine A; Shimada, Hiroshima; Kumar, Dinesh K; Arjunan, Sridhar P

2010-01-01

A differential, time-invariant, surface electromyogram (sEMG) model has been implemented. While it is based on existing EMG models, the novelty of this implementation is that it assigns more accurate distributions of variables to create realistic motor unit (MU) characteristics. Variables such as muscle fibre conduction velocity, jitter (the change in the interpulse interval between subsequent action potential firings) and motor unit size have been considered to follow normal distributions about an experimentally obtained mean. In addition, motor unit firing frequencies have been considered to have non-linear and type based distributions that are in accordance with experimental results. Motor unit recruitment thresholds have been considered to be related to the MU type. The model has been used to simulate single channel differential sEMG signals from voluntary, isometric contractions of the biceps brachii muscle. The model has been experimentally verified by conducting experiments on three subjects. Comparison between simulated signals and experimental recordings shows that the Root Mean Square (RMS) increases linearly with force in both cases. The simulated signals also show similar values and rates of change of RMS to the experimental signals.

Tree-level equivalence between a Lorentz-violating extension of QED and its dual model in electron-electron scattering

Energy Technology Data Exchange (ETDEWEB)

Toniolo, Giuliano R.; Fargnoli, H.G.; Brito, L.C.T. [Universidade Federal de Lavras, Departamento de Fisica, Caixa Postal 3037, Lavras, Minas Gerais (Brazil); Scarpelli, A.P.B. [Setor Tecnico-Cientifico, Departamento de Policia Federal, Sao Paulo (Brazil)

2017-02-15

S-matrix amplitudes for the electron-electron scattering are calculated in order to verify the physical equivalence between two Lorentz-breaking dual models. We begin with an extended Quantum Electrodynamics which incorporates CPT-even Lorentz-violating kinetic and mass terms. Then, in a process of gauge embedding, its gauge-invariant dual model is obtained. The physical equivalence of the two models is established at tree level in the electron-electron scattering and the unpolarized cross section is calculated up to second order in the Lorentz-violating parameter. (orig.)

Tree-level equivalence between a Lorentz-violating extension of QED and its dual model in electron-electron scattering

International Nuclear Information System (INIS)

Toniolo, Giuliano R.; Fargnoli, H.G.; Brito, L.C.T.; Scarpelli, A.P.B.

2017-01-01

S-matrix amplitudes for the electron-electron scattering are calculated in order to verify the physical equivalence between two Lorentz-breaking dual models. We begin with an extended Quantum Electrodynamics which incorporates CPT-even Lorentz-violating kinetic and mass terms. Then, in a process of gauge embedding, its gauge-invariant dual model is obtained. The physical equivalence of the two models is established at tree level in the electron-electron scattering and the unpolarized cross section is calculated up to second order in the Lorentz-violating parameter. (orig.)

Reliability of power electronic converter systems

CERN Document Server

Chung, Henry Shu-hung; Blaabjerg, Frede; Pecht, Michael

2016-01-01

This book outlines current research into the scientific modeling, experimentation, and remedial measures for advancing the reliability, availability, system robustness, and maintainability of Power Electronic Converter Systems (PECS) at different levels of complexity.

Experimental simulation of satellite observations of 100 kHz radio waves from relativistic electron beams above thunderclouds

OpenAIRE

Fullekrug, Martin; Hanuise, C; Parrot, M

2011-01-01

Relativistic electron beams above thunderclouds emit 100 kHz radio waves which illuminate the Earth's atmosphere and near-Earth space. This contribution aims to clarify the physical processes which are relevant for the spatial spreading of the radio wave energy below and above the ionosphere and thereby enables an experimental simulation of satellite observations of 100 kHz radio waves from relativistic electron beams above thunderclouds. The simulation uses the DEMETER satellite which...

Dielectric materials electrization by fast electrons

International Nuclear Information System (INIS)

Dyrkov, V.A.; Kononov, B.A.

1990-01-01

Electrization of short-circuited high-ohmage targets under irradiation by 50-200 keV electrons non-uniformly by volume is investigated both experimentally and theoretically. The obtained data show that effect of space charge field increases monotonically up to stationary state during irradiation. Time constant for space charge accumulation constitutes 1-10 min and has lower value for polymethylmethacrylate as compared with polyethyleneterephthalate and decreases with increase of beam current density. Good agreement of experimental and theoretical results for both materials confirms the validity of main positions of phonomenological model of space charge formation in dielectric materials under fast electron irradiation

Adjustment model of thermoluminescence experimental data

International Nuclear Information System (INIS)

Moreno y Moreno, A.; Moreno B, A.

2002-01-01

This model adjusts the experimental results for thermoluminescence according to the equation: I (T) = I (a i * exp (-1/b i * (T-C i )) where: a i , b i , c i are the i-Th peak adjusted to a gaussian curve. The adjustments of the curve can be operated manual or analytically using the macro function and the solver.xla complement installed previously in the computational system. In this work it is shown: 1. The information of experimental data from a LiF curve obtained from the Physics Institute of UNAM which the data adjustment model is operated in the macro type. 2. A LiF curve of four peaks obtained from Harshaw information simulated in Microsoft Excel, discussed in previous works, as a reference not in macro. (Author)

Electron excitation of alkali atoms

International Nuclear Information System (INIS)

Ormonde, S.

1979-02-01

The development and testing of a synthesized close-coupling effective model potential ten-channel electron-atom scattering code and some preliminary calculations of resonances in cross sections for the excitation of excited states of potassium by low energy electrons are described. The main results obtained are: identification of 1 S and 1 D structures in excitation cross sections below the 5 2 S threshold of neutral potassium; indications of additional structures - 1 P and 1 D between the 5 2 S and 5 2 D thresholds; and a suggested explanation of anomalously high interstate-electron impact excitation cross sections inferred from experiments on potassium-seeded plasmas. The effective potential model imbedded in the code can be used to simulate any atomic system that can be approximated by a single bound electron outside an ionic core. All that is needed is a set of effective potential parameters--experimental or theoretical. With minor modifications the code could be adapted to calculations of electron scattering by two-electron systems

Analysis of ionization wave dynamics in low-temperature plasma jets from fluid modeling supported by experimental investigations

Science.gov (United States)

Yousfi, M.; Eichwald, O.; Merbahi, N.; Jomaa, N.

2012-08-01

This work is devoted to fluid modeling based on experimental investigations of a classical setup of a low-temperature plasma jet. The latter is generated at atmospheric pressure using a quartz tube of small diameter crossed by helium gas flow and surrounded by an electrode system powered by a mono-polar high-voltage pulse. The streamer-like behavior of the fast plasma bullets or ionization waves launched in ambient air for every high-voltage pulse, already emphasized in the literature from experimental or analytical considerations or recent preliminary fluid models, is confirmed by a numerical one-moment fluid model for the simulation of the ionization wave dynamics. The dominant interactions between electron and the main ions present in He-air mixtures with their associated basic data are taken into account. The gradual dilution of helium in air outside the tube along the axis is also considered using a gas hydrodynamics model based on the Navier-Stokes equation assuming a laminar flow. Due to the low magnitude of the reduced electric field E/N (not exceeding 15 Td), it is first shown that consideration of the stepwise ionization of helium metastables is required to reach the critical size of the electron avalanches in order to initiate the formation of ionization waves. It is also shown that a gas pre-ionization ahead of the wave front of about 109 cm-3 (coming from Penning ionization without considering the gas photo-ionization) is required for the propagation. Furthermore, the second ionization wave experimentally observed during the falling time of the voltage pulse, between the powered electrode and the tube exit, is correlated with the electric field increase inside the ionized channel in the whole region between the electrode and the tube exit. The propagation velocity and the distance traveled by the front of the ionization wave outside the tube in the downstream side are consistent with the present experimental measurements. In comparison with the

Surface topography effects on energy-resolved polar angular distributions of electrons induced in heavy ion-Al collisions: experiments and models

International Nuclear Information System (INIS)

Mischler, J.; Banouni, M.; Banazeth, C.; Negre, M.; Benazeth, N.

1986-01-01

The influence of the surface topography on the polar angular distributions of secondary electrons emitted in Ar + (and Xe - )-Al collisions was studied. After each set of experiments, the surface target was viewed by scanning electron microscope. Under normal incidence, continuum background and Al L 23 VV Auger electron polar angular distributions were not modified by the topography and closely followed a cosine law. For Al L 23 MM Auger electrons, experimental angular distributions as a function of the emission polar angle theta, either were near a constant law or followed a decreasing law depending on the irradiation conditions. The N(theta) curves calculated from the models showed that the isotropic angular distributions obtained for electrons generated outside the crystal from a flat surface could be strongly modified by the surface topography. (author)

Electronic and optical properties of Fe, Pd, and Ti studied by reflection electron energy loss spectroscopy

International Nuclear Information System (INIS)

Tahir, Dahlang; Kraaer, Jens; Tougaard, Sven

2014-01-01

We have studied the electronic and optical properties of Fe, Pd, and Ti by reflection electron energy-loss spectroscopy (REELS). REELS spectra recorded for primary energies in the range from 300 eV to 10 keV were corrected for multiple inelastically scattered electrons to determine the effective inelastic-scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic-electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(−1/ε) by using the QUEELS-ε(k,ω)-REELS software package. The complex dielectric functions ε(k,ω), in the 0–100 eV energy range, for Fe, Pd, and Ti were determined from the derived Im(−1/ε) by Kramers-Kronig transformation and then the refractive index n and extinction coefficient k. The validity of the applied model was previously tested and found to give consistent results when applied to REELS spectra at energies between 300 and 1000 eV taken at widely different experimental geometries. In the present paper, we provide, for the first time, a further test on its validity and find that the model also gives consistent results when applied to REELS spectra in the full range of primary electron energies from 300 eV to 10000 eV. This gives confidence in the validity of the applied method.

Origin of electronic properties of PbGa2Se4 crystal: Experimental and theoretical investigations

International Nuclear Information System (INIS)

Babuka, T.; Kityk, I.V.; Parasyuk, O.V.; Myronchuk, G.; Khyzhun, O.Y.; Fedorchuk, A.O.; Makowska-Janusik, M.

2015-01-01

Graphical abstract: In the presented work the structural and electronic properties of the PbGa 2 Se 4 single crystal were investigated experimentally as well as theoretically. The XPS spectra, Urbach’s rule and steepness parameters of PbGa 2 Se 4 single crystal have been investigated for the first time. The quantum chemical calculations were also never performed before for the studied structure. The theoretically obtained data help to explain the properties of material. - Highlights: • Urbach’s rule and steepness parameters for PbGa 2 Se 4 crystals explored for the first time. • Non-reactivity of the PbGa 2 Se 4 surface was established by XPS. • DFT approach shows its efficiency to describe electronic properties of PbGa 2 Se 4 . • Electronic parameters are affected by existence of electron–phonon interaction. - Abstract: The PbGa 2 Se 4 crystal is a promising material for optoelectronic applications. It is caused by coexistence of the large polarized Pb cations and a huge contribution of anharmonic phonon subsystem caused by chalcogenide anions. In the present work the electronic and optical properties of the mentioned material were studied theoretically as well as experimentally by optical and X-ray photoelectron spectroscopy methods. The DFT approach has been used for the quantum chemical electronic properties calculations. Urbach rule and steepness parameters of the PbGa 2 Se 4 crystal have been evaluated for the first time. These parameters and Urbach energies increase with increasing temperature of the samples that is typical for the semiconducting materials. The XPS measurements of the investigated crystal reveal that all the spectral features are originated from core-level states of the constituent elements. Simultaneously these results also confirm non-reactivity of the PbGa 2 Se 4 surface. However, the titled single crystal possesses a number of intrinsic structural defects and vacancies thereby affecting its electronic properties. The

Evaluated experimental database on critical heat flux in WWER FA models

International Nuclear Information System (INIS)

Artamonov, S.; Sergeev, V.; Volkov, S.

2015-01-01

The paper presents the description of the evaluated experimental database on critical heat flux in WWER FA models of new designs. This database was developed on the basis of the experimental data obtained in the years of 2009-2012. In the course of its development, the database was reviewed in terms of completeness of the information about the experiments and its compliance with the requirements of Rostekhnadzor regulatory documents. The description of the experimental FA model characteristics and experimental conditions was specified. Besides, the experimental data were statistically processed with the aim to reject incorrect ones and the sets of experimental data on critical heat fluxes (CHF) were compared for different FA models. As a result, for the fi rst time, the evaluated database on CHF in FA models of new designs was developed, that was complemented with analysis functions, and its main purpose is to be used in the process of development, verification and upgrading of calculation techniques. The developed database incorporates the data of 4183 experimental conditions obtained in 53 WWER FA models of various designs. Keywords: WWER reactor, fuel assembly, CHF, evaluated experimental data, database, statistical analysis. (author)

Photo-activation radiotherapy with nanoparticles: Modeling at a sub-micrometer level and experimental comparison

International Nuclear Information System (INIS)

Delorme, R.

2013-01-01

the important dose enhancement factor (DEF) calculated in the vicinity of GdNP, highlighted from two-dimension DEF maps. The DEF can reach two orders of magnitude within a few nanometers of the GdNP surface and is mainly due to high-linear energy transfer electrons (≤ 5 keV). By modeling the case of nanoparticles randomly distributed on the cell membrane (closest to the experimental case), we showed that a good correlation exists between the SER4Gy and the membrane DEF. On the other hand, the comparison of the two elements showed that GdNP could produce more electrons (of lower energy) than AuNP (with same mass), but that the local DEF due to AuNP was more important. Interesting results were obtained by comparing the local DEF with experimental results on plasmid DNA. However, it seems important to carry on these studies by taking into account the post-irradiation chemical processes in modeling. (author) [fr

Tight-binding model of the photosystem II reaction center: application to two-dimensional electronic spectroscopy

Science.gov (United States)

Gelzinis, Andrius; Valkunas, Leonas; Fuller, Franklin D.; Ogilvie, Jennifer P.; Mukamel, Shaul; Abramavicius, Darius

2013-07-01

We propose an optimized tight-binding electron-hole model of the photosystem II (PSII) reaction center (RC). Our model incorporates two charge separation pathways and spatial correlations of both static disorder and fast fluctuations of energy levels. It captures the main experimental features observed in time-resolved two-dimensional (2D) optical spectra at 77 K: peak pattern, lineshapes and time traces. Analysis of 2D spectra kinetics reveals that specific regions of the 2D spectra of the PSII RC are sensitive to the charge transfer states. We find that the energy disorder of two peripheral chlorophylls is four times larger than the other RC pigments.

An improved energy-range relationship for high-energy electron beams based on multiple accurate experimental and Monte Carlo data sets

International Nuclear Information System (INIS)

Sorcini, B.B.; Andreo, P.; Hyoedynmaa, S.; Brahme, A.; Bielajew, A.F.

1995-01-01

A theoretically based analytical energy-range relationship has been developed and calibrated against well established experimental and Monte Carlo calculated energy-range data. Only published experimental data with a clear statement of accuracy and method of evaluation have been used. Besides published experimental range data for different uniform media, new accurate experimental data on the practical range of high-energy electron beams in water for the energy range 10-50 MeV from accurately calibrated racetrack microtrons have been used. Largely due to the simultaneous pooling of accurate experimental and Monte Carlo data for different materials, the fit has resulted in an increased accuracy of the resultant energy-range relationship, particularly at high energies. Up to date Monte Carlo data from the latest versions of the codes ITS3 and EGS4 for absorbers of atomic numbers between four and 92 (Be, C, H 2 O, PMMA, Al, Cu, Ag, Pb and U) and incident electron energies between 1 and 100 MeV have been used as a complement where experimental data are sparse or missing. The standard deviation of the experimental data relative to the new relation is slightly larger than that of the Monte Carlo data. This is partly due to the fact that theoretically based stopping and scattering cross-sections are used both to account for the material dependence of the analytical energy-range formula and to calculate ranges with the Monte Carlo programs. For water the deviation from the traditional energy-range relation of ICRU Report 35 is only 0.5% at 20 MeV but as high as - 2.2% at 50 MeV. An improved method for divergence and ionization correction in high-energy electron beams has also been developed to enable use of a wider range of experimental results. (Author)

Towards Automated Bargaining in Electronic Markets: A Partially Two-Sided Competition Model

Science.gov (United States)

Gatti, Nicola; Lazaric, Alessandro; Restelli, Marcello

This paper focuses on the prominent issue of automating bargaining agents within electronic markets. Models of bargaining in literature deal with settings wherein there are only two agents and no model satisfactorily captures settings in which there is competition among buyers, being they more than one, and analogously among sellers. In this paper, we extend the principal bargaining protocol, i.e. the alternating-offers protocol, to capture bargaining in markets. The model we propose is such that, in presence of a unique buyer and a unique seller, agents' equilibrium strategies are those in the original protocol. Moreover, we game theoretically study the considered game providing the following results: in presence of one-sided competition (more buyers and one seller or vice versa) we provide agents' equilibrium strategies for all the values of the parameters, in presence of two-sided competition (more buyers and more sellers) we provide an algorithm that produce agents' equilibrium strategies for a large set of the parameters and we experimentally evaluate its effectiveness.

Thermal conductivity of Al–Cu–Mg–Si alloys: Experimental measurement and CALPHAD modeling

Energy Technology Data Exchange (ETDEWEB)

Zhang, Cong [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Sino-German cooperation group “Microstructure in Al alloys”, Central South University, Changsha, Hunan 410083 (China); Du, Yong, E-mail: yong-du@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Sino-German cooperation group “Microstructure in Al alloys”, Central South University, Changsha, Hunan 410083 (China); Liu, Shuhong; Liu, Yuling [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Sino-German cooperation group “Microstructure in Al alloys”, Central South University, Changsha, Hunan 410083 (China); Sundman, Bo. [INSTN, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France)

2016-07-10

Highlights: • The thermal conductivities of Al–x wt% Cu (x = 1, 3, 5, 15 and 30) and Al–y wt% Si (y = 2, 12.5 and 20) alloys were determined. • The reported thermal conductivities of Al–Cu–Mg–Si system were critically reviewed. • The CALPHAD approach was applied for the modeling of thermal conductivity. • The applicability of CALPHAD technique in the modeling of thermal conductivity was discussed. - Abstract: In the present work, the thermal conductivities and microstructure of Al–x wt% Cu (x = 1, 3, 5, 15 and 30) and Al–y wt% Si (y = 2, 12.5 and 20) alloys were investigated by using laser-flash method, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Besides, a CALPHAD (CALculation of PHAse Diagram) approach to evaluate the thermal conductivity of Al–Cu–Mg–Si system was performed. The numerical models for the thermal conductivity of pure elements and stoichiometric phases were described as polynomials, and the coefficients were optimized via PARROT module of Thermal-Calc software applied to the experimental data. The thermal conductivity of (Al)-based solid solutions was described by using Redlich–Kister interaction parameters. For alloys in two-phase region, the interface scattering parameter was proposed in the modeling to describe the impediment of interfaces on the heat transfer. Finally, a set of self-consistent parameters for the description of thermal conductivity in Al–Cu–Mg–Si system was obtained, and comprehensive comparisons between the calculated and measured thermal conductivities show that the experimental information is satisfactorily accounted for by the present modeling.

Experimental determination of pcav factors for cylindrical ionisation chambers in electron beams

International Nuclear Information System (INIS)

Palm, Aa.; Mattsson, O.

2000-01-01

The electron beam method recommended for calibrating plane parallel ionisation chambers involves cavity correction factors for cylindrical chambers. The cavity correction factors in the IAEA TRS-381 Code of Practice are based on measurements at R 100 in a PMMA phantom using PMMA cylindrical chambers having different cavity radii. In the present work the recommended data were confirmed for electron beams delivered by modern medical accelerators by using the very same phantom and ionisation chambers that were used in the original work. From another series of measurements, using four specially designed wall-less chambers in a graphite phantom, the linear relation between p cav and the chamber radius that is the basis for the experimental method, was verified. The method was also used to determine the cavity correction factors for a set of Farmer-like graphite chambers placed in water. Compared to the TRS-381 Code of Practice a smaller correction was found for the cavity perturbation for the graphite chambers used in water. (author)

Experimental and numerical study of flow deflection effects on electronic air-cooling

International Nuclear Information System (INIS)

Arfaoui, Ahlem; Ben Maad, Rejeb; Hammami, Mahmoud; Rebay, Mourad; Padet, Jacques

2009-01-01

This work present a numerical and experimental investigation of the influence of transversal flow deflector on the cooling of a heated block mounted on a flat plate. The deflector is inclined and therefore it guides the air flow to the upper surface of the block. This situation is simulating the air-cooling of a rectangular integrated circuit or a current converter mounted on an electronic board. The electronic component are assumed dissipating a low or medium heat flux (with a density lower than 5000 W/m 2 ), as such the forced convection air cooling without fan or heat sink is still sufficient. The study details the effects of the angle of deflector on the temperature and the heat transfer coefficient along the surface of the block and around it. The results of the numerical simulations and the InfraRed camera measurements show that the deviation caused by deflector may significantly enhance the heat transfer on the top face of block

Suprathermal electron studies in Tokamak plasmas by means of diagnostic measurements and modeling

International Nuclear Information System (INIS)

Kamleitner, J.

2015-01-01

To achieve reactor-relevant conditions in a tokamak plasma, auxiliary heating systems are required and can be realized by waves injected in the plasma that heat ions or electrons. Electron cyclotron resonant heating (ECRH) is a very flexible and robust technique featuring localized power deposition and current drive (CD) capabilities. Its fundamental principles are well understood and the application of ECRH is a proven and established tool; electron cyclotron current drive (ECCD) is regularly used to develop advanced scenarios and control magneto-hydrodynamics (MHD) instabilities in the plasma by tailoring the current profile. There remain important open questions, such as the phase space dynamics, the observed radial broadening of the supra-thermal electron distribution function and discrepancies in predicted and experimental CD efficiency. A main goal is to improve the understanding of wave-particle interaction in plasmas and current drive mechanisms. This was accomplished by combined experimental and numerical studies, strongly based on the conjunction of hard X-ray (HXR) Bremsstrahlung measurements and Fokker-Planck modelling, characterizing the supra-thermal electron population. The hard X-ray tomographic spectrometer (HXRS) diagnostic was developed to perform these studies by investigating spatial HXR emission asymmetries in the co- and counter-current directions and within the poloidal plane. The system uses cadmium-telluride detectors and digital acquisition to store the complete time history of incoming photon pulses. An extensive study of digital pulse processing algorithms was performed and its application allows the HXRS to handle high count rates in a noisy tokamak environment. Numerical tools were developed to improve the time resolution by conditional averaging and to obtain local information with the general tomographic inversion package. The interfaces of the LUKE code and the well-established CQL3D Fokker-Planck code to the Tokamak a

Multi-scale modelling and numerical simulation of electronic kinetic transport

International Nuclear Information System (INIS)

Duclous, R.

2009-11-01

This research thesis which is at the interface between numerical analysis, plasma physics and applied mathematics, deals with the kinetic modelling and numerical simulations of the electron energy transport and deposition in laser-produced plasmas, having in view the processes of fuel assembly to temperature and density conditions necessary to ignite fusion reactions. After a brief review of the processes at play in the collisional kinetic theory of plasmas, with a focus on basic models and methods to implement, couple and validate them, the author focuses on the collective aspect related to the free-streaming electron transport equation in the non-relativistic limit as well as in the relativistic regime. He discusses the numerical development and analysis of the scheme for the Vlasov-Maxwell system, and the selection of a validation procedure and numerical tests. Then, he investigates more specific aspects of the collective transport: the multi-specie transport, submitted to phase-space discontinuities. Dealing with the multi-scale physics of electron transport with collision source terms, he validates the accuracy of a fast Monte Carlo multi-grid solver for the Fokker-Planck-Landau electron-electron collision operator. He reports realistic simulations for the kinetic electron transport in the frame of the shock ignition scheme, the development and validation of a reduced electron transport angular model. He finally explores the relative importance of the processes involving electron-electron collisions at high energy by means a multi-scale reduced model with relativistic Boltzmann terms

Electron-stimulated purification of platinum nanostructures grown via focused electron beam induced deposition

Directory of Open Access Journals (Sweden)

Brett B. Lewis

2015-04-01

Full Text Available Platinum–carbon nanostructures deposited via electron beam induced deposition from MeCpPt(IVMe3 are purified during a post-deposition electron exposure treatment in a localized oxygen ambient at room temperature. Time-dependent studies demonstrate that the process occurs from the top–down. Electron beam energy and current studies demonstrate that the process is controlled by a confluence of the electron energy loss and oxygen concentration. Furthermore, the experimental results are modeled as a 2nd order reaction which is dependent on both the electron energy loss density and the oxygen concentration. In addition to purification, the post-deposition electron stimulated oxygen purification process enhances the resolution of the EBID process due to the isotropic carbon removal from the as-deposited materials which produces high-fidelity shape retention.

Experimental (e, 2e) study of exchange interferences in the resonant Auger decay of Ar induced by electron impact

International Nuclear Information System (INIS)

Paripás, Béla; Palásthy, Béla; Žitnik, Matjaz

2013-01-01

Highlights: •The interference of autoionizing resonances with a common final ionic state is measured. •We have developed a method to experimentally verify for the exchange interference effect. •The sum of kinetic energies of the two detected electrons is kept constant. •Mainly the interference effects of [2p 3/2 ]4p and [2p 1/2 ]4p resonances in argon are studied. •The results possibly indicate small exchange interference effects. -- Abstract: Any two autoionizing resonances with a common final ionic state can be made to interfere by an appropriate selection of electron impact energy. To reveal the exchange interference effects a selective detection of electron pairs related to the selected final state is desired. We have performed a constant ionic state (e, 2e) experiment (CIS) isolating the final state by keeping the sum of transmission energies of two independent electron spectrometers constant. In the focus of this work are the exchange interference effects of 2p 3/2 −1 4p and 2p 1/2 −1 4p resonances in argon decaying to the 3p −2 ( 1 D)4p 2 P, 2 D final ionic state with energy E F = 37.3 ± 0.2 eV. We have developed a method to experimentally verify for the exchange interference effect. It is based on a comparison of the CIS spectrum recorded at the critical primary electron energy that activates the interferences, and the constructed, interference-free CIS spectrum that is build up from the CIS spectrum measured at primary electron energy away from the critical value. The results possibly indicate small exchange interference effects that may have been considerably smeared out at present experimental energy resolution

Understanding the role of fast electrons in the heating of dense matter: experimental techniques and recent results

International Nuclear Information System (INIS)

Freeman, R.; Anderson, C.; Hill, J.M.; King, J.; Snavely, R.; Hatchett, S.; Key, M.; Koch, J.; MacKinnon, A.; Stephens, R.; Cowan, T.

2003-01-01

An intense laser impinging upon dense matter converts a large fraction of its energy into fast electrons. (Here we take 'fast' to mean electrons that are much more energetic than the normal Boltzmann-like distribution measured in the tens to hundreds of eV.) Upon transiting the interior of the dense matter, these electrons are responsible for isochoric heating of the material. Just how these electrons traverse the material, and various interfaces within the material, is a subject of substantial amounts of computation and theory, and recently, experiments. Here we outline the nature of the heating mechanisms, and the current level of understanding of the complex physical processes. In particular we discuss new experimental techniques to record essential features of this transport problem

Study and realisation of an ion source obtained by electronic bombardment - experimentation with phosphorus

International Nuclear Information System (INIS)

Schneider, Philippe

1979-01-01

This research thesis reports the study and development of an ion source by electronic bombardment. In order to solve some practical difficulties (cathode destruction, source instability, and so on), the design of each component has been very careful, notably for the electron gun. The author first briefly discusses the exiting ionisation processes, gives a list of ion which can be produced, with a focus on phosphorus for which the ionisation cross section is defined and assessed. After an assessment of different ionisation processes, and an indication of performance of the best existing sources, the author explains the choice for a totally different process. In the second part, he describes the experimental device, and particularly the electron gun as its design has been an important part of this research work. The source operation is described and its characteristics and performance are studied. Finally, the author outlines that some improvements are still possible to obtain a totally exploitable source [fr

A Combined Model of Charging of the Surface and Bulk of a Dielectric Target by Electrons with the Energies 10-30 keV

Science.gov (United States)

Zykov, V. M.; Neiman, D. A.

2018-04-01

A physico-mathematical model of the processes of radiation-induced charging of dielectric materials with open surfaces, irradiated with monoenergetic electrons in the energy range 10-30 keV, is described. The model takes into account the relationship between the processes of surface and bulk charging for the given conditions of the experimental design, which accounts for the effect of anomalously long charging of dielectrics after the incident energy of primary electrons during charging is reduced to below the second critical energy for the secondary electronic emission coefficient. The initial fast phase of charging a high-resistivity dielectric material (Al2O3) is investigated. It is shown that as the incident electron energy is approaching the second critical energy during charging, the secondary electronic emission is partially suppressed due to negative charging of the open surface of the dielectric and formation of a near-surface inversion electrical field retarding the electronic emission yield.

Electron emission from solids induced by swift heavy ions

International Nuclear Information System (INIS)

Xiao Guoqing

2000-01-01

The recent progresses in experimental and theoretical studies of the collision between swift heavy ion and solids as well as electron emission induced by swift heavy ion in solids were briefly reviewed. Three models, Coulomb explosion, thermal spike and repulsive long-lived states, for interpreting the atomic displacements stimulated by the electronic energy loss were discussed. The experimental setup and methods for measuring the electron emission from solids were described. The signification deviation from a proportionality between total electron emission yields and electronic stopping power was found. Auger-electron and convoy-electron spectra are thought to be a probe for investigating the microscopic production mechanisms of the electronic irradiation-damage. Electron temperature and track potential at the center of nuclear tracks in C and polypropylene foils induced by 5 MeV/u heavy ions, which are related to the electronic excitation density in metals and insulators respectively, were extracted by measuring the high resolution electron spectra

A novel experimental scheme of electron scattering off unstable nuclei with a self-confining radioactive ion target (SCRIT)

International Nuclear Information System (INIS)

Wakasugi, Masanori

2005-01-01

We proposed a new experimental scheme of an electron scattering off unstable nuclei using a Self-Confining Radioactive Ion Target (SCRIT). The SCRIT is an unstable ion target formed in the electron storage ring, and is based on completely new idea. We constructed prototype of the SCRIT device and installed it in the electron storage ring KSR in Kyoto University. In the test experiment, 10 7 -Cs ions are confined in the SCRIT with the lifetime of about 2 s and the feasibility of the SCRIT as the target has been confirmed. (author)

Electronic Processes at Organic−Organic Interfaces: Insight from Modeling and Implications for Opto-electronic Devices †

KAUST Repository

Beljonne, David

2011-02-08

We report on the recent progress achieved in modeling the electronic processes that take place at interfaces between π-conjugated materials in organic opto-electronic devices. First, we provide a critical overview of the current computational techniques used to assess the morphology of organic: organic heterojunctions; we highlight the compromises that are necessary to handle large systems and multiple time scales while preserving the atomistic details required for subsequent computations of the electronic and optical properties. We then review some recent theoretical advances in describing the ground-state electronic structure at heterojunctions between donor and acceptor materials and highlight the role played by charge-transfer and long-range polarization effects. Finally, we discuss the modeling of the excited-state electronic structure at organic:organic interfaces, which is a key aspect in the understanding of the dynamics of photoinduced electron-transfer processes. © 2010 American Chemical Society.

Electron correlations in narrow energy bands: modified polar model approach

Directory of Open Access Journals (Sweden)

L. Didukh

2008-09-01

Full Text Available The electron correlations in narrow energy bands are examined within the framework of the modified form of polar model. This model permits to analyze the effect of strong Coulomb correlation, inter-atomic exchange and correlated hopping of electrons and explain some peculiarities of the properties of narrow-band materials, namely the metal-insulator transition with an increase of temperature, nonlinear concentration dependence of Curie temperature and peculiarities of transport properties of electronic subsystem. Using a variant of generalized Hartree-Fock approximation, the single-electron Green's function and quasi-particle energy spectrum of the model are calculated. Metal-insulator transition with the change of temperature is investigated in a system with correlated hopping. Processes of ferromagnetic ordering stabilization in the system with various forms of electronic DOS are studied. The static conductivity and effective spin-dependent masses of current carriers are calculated as a function of electron concentration at various DOS forms. The correlated hopping is shown to cause the electron-hole asymmetry of transport and ferromagnetic properties of narrow band materials.

Production of hot electrons in mirror systems associated with ECR heating with longitudinal input of microwaves

International Nuclear Information System (INIS)

Zhil'tsov, V.A.; Skovoroda, A.A.; Timofeev, A.V.; Kharitonov, K.Yu.; Shcherbakov, A.G.

1991-01-01

Almost all experiments on ECR plasma heating are accompanied by the formation of hot electrons (i.e., electrons with energy substantially greater than the average of the bulk population). In mirror systems these electrons may determine the basic energy content (β) of the plasma. In this paper, results are presented from experimental measurements of the hot electron population resulting from ECR heating of the plasma in OGRA-4. A theoretical model is developed which describes the hot electron dynamics and the propagation of electromagnetic oscillations in the plasma self-consistently. The results obtained with this model are in agreement with experimental data

Electron Flux Models for Different Energies at Geostationary Orbit

Science.gov (United States)

Boynton, R. J.; Balikhin, M. A.; Sibeck, D. G.; Walker, S. N.; Billings, S. A.; Ganushkina, N.

2016-01-01

Forecast models were derived for energetic electrons at all energy ranges sampled by the third-generation Geostationary Operational Environmental Satellites (GOES). These models were based on Multi-Input Single-Output Nonlinear Autoregressive Moving Average with Exogenous inputs methodologies. The model inputs include the solar wind velocity, density and pressure, the fraction of time that the interplanetary magnetic field (IMF) was southward, the IMF contribution of a solar wind-magnetosphere coupling function proposed by Boynton et al. (2011b), and the Dst index. As such, this study has deduced five new 1 h resolution models for the low-energy electrons measured by GOES (30-50 keV, 50-100 keV, 100-200 keV, 200-350 keV, and 350-600 keV) and extended the existing >800 keV and >2 MeV Geostationary Earth Orbit electron fluxes models to forecast at a 1 h resolution. All of these models were shown to provide accurate forecasts, with prediction efficiencies ranging between 66.9% and 82.3%.

Experimental and modeling analysis of fast ionization wave discharge propagation in a rectangular geometry

International Nuclear Information System (INIS)

Takashima, Keisuke; Adamovich, Igor V.; Xiong Zhongmin; Kushner, Mark J.; Starikovskaia, Svetlana; Czarnetzki, Uwe; Luggenhoelscher, Dirk

2011-01-01

Fast ionization wave (FIW), nanosecond pulse discharge propagation in nitrogen and helium in a rectangular geometry channel/waveguide is studied experimentally using calibrated capacitive probe measurements. The repetitive nanosecond pulse discharge in the channel was generated using a custom designed pulsed plasma generator (peak voltage 10-40 kV, pulse duration 30-100 ns, and voltage rise time ∼1 kV/ns), generating a sequence of alternating polarity high-voltage pulses at a pulse repetition rate of 20 Hz. Both negative polarity and positive polarity ionization waves have been studied. Ionization wave speed, as well as time-resolved potential distributions and axial electric field distributions in the propagating discharge are inferred from the capacitive probe data. ICCD images show that at the present conditions the FIW discharge in helium is diffuse and volume-filling, while in nitrogen the discharge propagates along the walls of the channel. FIW discharge propagation has been analyzed numerically using quasi-one-dimensional and two-dimensional kinetic models in a hydrodynamic (drift-diffusion), local ionization approximation. The wave speed and the electric field distribution in the wave front predicted by the model are in good agreement with the experimental results. A self-similar analytic solution of the fast ionization wave propagation equations has also been obtained. The analytic model of the FIW discharge predicts key ionization wave parameters, such as wave speed, peak electric field in the front, potential difference across the wave, and electron density as functions of the waveform on the high voltage electrode, in good agreement with the numerical calculations and the experimental results.

Fundamental models of electronic transport in amorphous semiconductors

International Nuclear Information System (INIS)

Emin, D.

1982-01-01

Significant fundamental questions lie at the heart of our understanding of the electronic and optical properties of semiconducting and insulating glasses. In this article the principal features of the Mott-CFO model and the small-polaron model are described. While the Mott-CFO model seems to apply to the high-mobility electron transport in glassy SiO 2 and Cd 2 As 3 it does not appear applicable to the most frequently studied chalocogenide glasses. Furthermore, the Mott-CFO model does not account for as basic a feature as the sign of the Hall effect. On the other hand, the small-polaron model accounts for the observed d.c. conductivity, Peltier heat and Hall mobility in a very simple and direct manner

Electron ejection from solids induced by fast highly-charged ions

Energy Technology Data Exchange (ETDEWEB)

Schiwietz, G. [Hahn-Meitner-Inst. GmbH, Berlin (Germany). Abt. FD; Xiao, G. [Hahn-Meitner-Inst. GmbH, Berlin (Germany). Abt. FD

1996-02-01

Total electron-ejection yields and Auger-electron spectra for highly-charged ions interacting with different foil targets have been investigated in this work. New experimental and theoretical data for normal incident 5 MeV/u heavy ions on graphite and polypropylene foils are presented and discussed. These two materials have been selected as model systems representing conductors and insulator targets. Our measured projectile nuclear-charge dependence of the total electron yield from carbon foils clearly deviates from results of some transport models that predict a proportionality with respect to the electronic stopping power of the projectiles. Possible reasons for this deviation are discussed. We have also extended our measurements on cascade-induced C-KLL Auger-electron production. The corresponding results for 5 MeV/u S ions on carbon were obtained with a new method and agree fairly well with previous data. Furthermore, we have performed an experimental and theoretical investigation on the nuclear-track potential in insulators. Comparison of experimental data with theoretical results for N{sup 7+}, Ne{sup 9+}, Ar{sup 16+} and Ni{sup 23+} ions allow for an estimate of the electron/hole pair recombination time at the center of the track in polypropylene. (orig.).

Failure of single electron descriptions of molecular orbital collision processes. [Electron promotion mechanism

Energy Technology Data Exchange (ETDEWEB)

Elston, S.B.

1978-01-01

Inner-shell excitation occurring in low and moderate (keV range) energy collisions between light atomic and ionic systems is frequently describable in terms of molecular promotion mechanisms, which were extensively explored both theoretically and experimentally. The bulk of such studies have concentrated on processes understandable through the use of single- and independent-electron models. Nonetheless, it is possible to find cases of inner-shell excitation in relatively simple collision systems which involve nearly simultaneous multiple-electron transitions and transitions induced by inherently two-electron interactions. Evidence for these many- and nonindependent-electron phenomena in inner-shell excitation processes and the importance of considering such effects in the interpretation of collisionally induced excitation spectra is discussed. 13 references.

Accounting of inter-electron correlations in the model of mobile electron shells

International Nuclear Information System (INIS)

Panov, Yu.D.; Moskvin, A.S.

2000-01-01

One studied the basic peculiar features of the model for mobile electron shells for multielectron atom or cluster. One offered a variation technique to take account of the electron correlations where the coordinates of the centre of single-particle atomic orbital served as variation parameters. It enables to interpret dramatically variation of electron density distribution under anisotropic external effect in terms of the limited initial basis. One studied specific correlated states that might make correlation contribution into the orbital current. Paper presents generalization of the typical MO-LCAO pattern with the limited set of single particle functions enabling to take account of additional multipole-multipole interactions in the cluster [ru

Axial channeling in electron diffraction

International Nuclear Information System (INIS)

Ichimiya, A.; Lehmpfuhl, G.

1978-01-01

Kossel patterns from Silicon and Niobium were obtained with a convergent electron beam. An intensity maximum in the direction of the zone axes [001] and [111] of Nb was interpreted as axial channeling. The intensity distribution in Kossel patterns was calculated by means of the Bloch wave picture of the dynamical theory of electron diffraction. Particularly zone axis patterns were calculated for different substance-energy combinations and they were compared with experimental observations. The intensity distribution in the calculated Kossel patterns was very sensitive to the model of absorption and it was found that a treatment of the absorption close to the model of Humphreys and Hirsch [Phil. Mag. 18, 115 (1968)] gave the best agreement with the experimental observations. Furthermore it is shown which Bloch waves are important for the intensity distribution in the Kossel patterns, how they are absorbed and how they change with energy. (orig.) [de

The AtChem On-line model and Electronic Laboratory Notebook (ELN): A free community modelling tool with provenance capture

Science.gov (United States)

Young, J. C.; Boronska, K.; Martin, C. J.; Rickard, A. R.; Vázquez Moreno, M.; Pilling, M. J.; Haji, M. H.; Dew, P. M.; Lau, L. M.; Jimack, P. K.

2010-12-01

AtChem On-line1 is a simple to use zero-dimensional box modelling toolkit, developed for use by laboratory, field and chamber scientists. Any set of chemical reactions can be simulated, in particular the whole Master Chemical Mechanism (MCM2) or any subset of it. Parameters and initial data can be provided through a self-explanatory web form and the resulting model is compiled and run on a dedicated server. The core part of the toolkit, providing a robust solver for thousands of chemical reactions, is written in Fortran and uses SUNDIALS3 CVODE libraries. Chemical systems can be constrained at multiple, user-determined timescales; this enabled studies of radical chemistry at one minute timescales. AtChem On-line is free to use and requires no installation - a web browser, text editor and any compressing software is all the user needs. CPU and storage are provided by the server (input and output data are saved indefinitely). An off-line version is also being developed, which will provide batch processing, an advanced graphical user interface and post-processing tools, for example, Rate of Production Analysis (ROPA) and chainlength analysis. The source code is freely available for advanced users wishing to adapt and run the program locally. Data management, dissemination and archiving are essential in all areas of science. In order to do this in an efficient and transparent way, there is a critical need to capture high quality metadata/provenance for modelling activities. An Electronic Laboratory Notebook (ELN) has been developed in parallel with AtChem Online as part of the EC EUROCHAMP24 project. In order to use controlled chamber experiments to evaluate the MCM, we need to be able to archive, track and search information on all associated chamber model runs, so that they can be used in subsequent mechanism development. Therefore it would be extremely useful if experiment and model metadata/provenance could be easily and automatically stored electronically

The experimental and shell model approach to 100Sn

International Nuclear Information System (INIS)

Grawe, H.; Maier, K.H.; Fitzgerald, J.B.; Heese, J.; Spohr, K.; Schubart, R.; Gorska, M.; Rejmund, M.

1995-01-01

The present status of experimental approach to 100 Sn and its shell model structure is given. New developments in experimental techniques, such as low background isomer spectroscopy and charged particle detection in 4π are surveyed. Based on recent experimental data shell model calculations are used to predict the structure of the single- and two-nucleon neighbours of 100 Sn. The results are compared to the systematic of Coulomb energies and spin-orbit splitting and discussed with respect to future experiments. (author). 51 refs, 11 figs, 1 tab