Relations between focusing power of space-charge lenses and external electromagnetic fields
International Nuclear Information System (INIS)
Yu Qingchang; Qiu Hong; Huang Jiachang
1991-01-01
Under different external electromagnetic fields, the electron densities of the electron cloud in a self-sustaning spece-charge lens are measured with the radio-frequency method and the energy distributions of the ions produced in ionization are measured with the stopping field method. From them the relations between the focusing power of space-charge lenses and the external electromagnetic fields are determined. The available region of the Lebedev-Morozov formula is discussed
Space charge in ionization detectors and the NA48 electromagnetic calorimeter
International Nuclear Information System (INIS)
Palestini, S.; Barr, G.D.; Biino, C.; Calafiura, P.; Ceccucci, A.; Cerri, C.; Chollet, J.C.; Cirilli, M.; Cogan, J.; Costantini, F.; Crepe, S.; Cundy, D.; Fantechi, R.; Fayard, L.; Fischer, G.; Formica, A.; Frabetti, P.L.; Funk, W.; Gianoli, A.; Giudici, S.; Gonidec, A.; Gorini, B.; Govi, G.; Iconomidou-Fayard, L.; Kekelidze, V.; Kubischta, W.; Luitz, S.; Mannelli, I.; Martini, M.; Mikulec, I.; Norton, A.; Ocariz, J.; Schinzel, D.; Sozzi, M.; Tatishvili, G.; Tkatchev, A.; Unal, G.; Velasco, M.; Vossnack, O.; Wahl, H.
1999-01-01
The subject of space charge due to positive ions slowly moving in parallel plate ionization chambers is considered. A model for the degradation of the detector response is developed, with particular emphasis on electromagnetic calorimeters.The topics discussed include: (a) the stationary; (b) the time dependent cases; (c) the limit of very large space charge; (d) the electric field dependence of the electron drift velocity; (e) the effect of longitudinal development of showers; (f) the behaviour of the average reductions of response; (g) the non-uniformity of response for different positions of the shower axis inside the cell defined by the electrodes. The NA48 calorimeter is used as application and for comparison of results
The effects of electromagnetic space-charge fields in RF photocathode guns
International Nuclear Information System (INIS)
Park, C.S.; Hess, M.
2010-01-01
In high-brightness rf photocathode guns, the effects of space-charge are important for electron bunches with high bunch charge. In an effort to accurately simulate the effects of these space-charge fields without the presence of numerical grid dispersion, a Green's function based code called IRPSS (Indiana Rf Photocathode Source Simulator) was developed. In this paper, we show the results of numerical simulations of the Argonne Wakefield Accelerator photocathode gun using IRPSS, and compare them with the results of an electrostatic Green's function version of IRPSS.
International Nuclear Information System (INIS)
Erokhin, N.S.; Zol'nikova, N.N.; Kuznetsov, E.A.; Mikhajlovskaya, L.A.
2010-01-01
Based on numerical calculations considered the relativistic acceleration of charged particles in space plasma when surfing on the spatially localized package of electromagnetic waves. The problem is reduced to the study of unsteady, nonlinear equation for the wave phase at the carrier frequency at the location of the accelerated charge, which is solved numerically. We study the temporal dynamics of the relativistic factor, the component of momentum and velocity of the particle, its trajectory is given gyro-rotation in an external magnetic field after the departure of the effective potential well. Dependence of the dynamics of a particle interacting with the wave of the sign of the velocity of the charge along the wave front. We formulate the optimal conditions of the relativistic particle acceleration wave packet, indicate the possibility of again (after a number gyro-turnover) charge trapping wave with an additional relativistic acceleration.
Charged particles in external electromagnetic fields
International Nuclear Information System (INIS)
Giovannini, N.P.D.
1976-01-01
The present study contains a general theoretical group analysis of the problem of a charged massive particle moving in an (arbitrary) classical external electromagnetic field. This analysis is essentially based on the space-time symmetry properties of e.m. fields and e.m. field equations, as well as the fact that the considered equations of motion depend on the field via a potential
Ferrario, M.; Palumbo, L.
2014-12-19
The space charge forces are those generated directly by the charge distribution, with the inclusion of the image charges and currents due to the interaction of the beam with a perfectly conducting smooth pipe. Space charge forces are responsible for several unwanted phenomena related to beam dynamics, such as energy loss, shift of the synchronous phase and frequency , shift of the betatron frequencies, and instabilities. We will discuss in this lecture the main feature of space charge effects in high-energy storage rings as well as in low-energy linacs and transport lines.
The Electromagnetic Force between Two Moving Charges
Minkin, Leonid; Shapovalov, Alexander S.
2018-01-01
A simple model of parallel motion of two point charges and the subsequent analysis of the electromagnetic field transformation invariant quantity are considered. It is shown that ignoring the coupling of electric and magnetic fields, as is done in some introductory physics books, can lead to miscalculations of the force between moving charges.…
International Nuclear Information System (INIS)
Chauvin, N
2013-01-01
First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented. (author)
Chauvin, N.
2013-12-16
First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented.
The electromagnetic force between two moving charges
Minkin, Leonid; Shapovalov, Alexander S.
2018-05-01
A simple model of parallel motion of two point charges and the subsequent analysis of the electromagnetic field transformation invariant quantity are considered. It is shown that ignoring the coupling of electric and magnetic fields, as is done in some introductory physics books, can lead to miscalculations of the force between moving charges. Conceptual and computational aspects of these issues are discussed, and implications to the design of electron beam devices are considered.
International Nuclear Information System (INIS)
Liu Yong; Xia Jiawen; Xu Xiangyang; Lu Xiaowen; Wu Junli
2000-01-01
Cooler Storage Ring (CSR), and upgrading program planned at the Heavy Ion Research Facility in Lanzhou (HIRFL), will supply beams with higher quality and intensity. Space charge effects should be considered due to this magnitude of intensity in CSR. The concept and some phenomena of space charge effects are discussed. Space charge intensity limit and space charge tune shift of normal CSR operation are given. It is of significance for the construction and operation of the future facility
Space charge effect in an accelerated beam
Directory of Open Access Journals (Sweden)
G. Stupakov
2008-01-01
Full Text Available It is usually assumed that the space charge effects in relativistic beams scale with the energy of the beam as γ^{-2}, where γ is the relativistic factor. We show that for a beam accelerated in the longitudinal direction there is an additional space charge effect in free space that scales as E/γ, where E is the accelerating field. This field has the same origin as the “electromagnetic mass of the electron” discussed in textbooks on electrodynamics. It keeps the balance between the kinetic energy of the beam and the energy of the electromagnetic field of the beam. We then consider the effect of this field on a beam generated in an rf gun and calculate the energy spread produced by this field in the beam.
Intrinsic space charge resonances and the space charge limit
International Nuclear Information System (INIS)
Parzen, G.
1990-01-01
A study has been done of the dependence of the space charge limit on the choice of ν-values using a simulation program. This study finds a strong dependence of the space charge limit on the location of the ν-values relative to the intrinsic space charge resonances, which are driven by the space charge forces due to the beam itself. Four accelerators were studied. For some of these accelerators the study suggest that the space charge limit can be increased by about a factor of 2 proper choice of the ν-values. The lower order 1/2 and 1/4 intrinsic resonances appear to be the important resonances. There is some evidence for effects due to the 1/6 and 1/8 intrinsic resonances, particularly for larger synchrotrons. 5 figs
Charges and Electromagnetic Radiation as Topological Excitations
Directory of Open Access Journals (Sweden)
Manfried Faber
2017-01-01
Full Text Available We discuss a model with stable topological solitons in Minkowski space with only three degrees of freedom, the rotational angles of a spatial Dreibein. This model has four types of solitons differing in two topological quantum numbers which we identify with electric charge and spin. The vacuum has a two-dimensional degeneracy leading to two types of massless excitations, characterised by a topological quantum number which could have a physical equivalent in the photon number.
Coherent electromagnetic radiation of a modulated beam of charged particles
Energy Technology Data Exchange (ETDEWEB)
Pankratov, S G [The State Committee of Standards of the USSR, Moscow, USSR
1977-12-27
The intensity of electromagnetic radiation produced by a modulated beam of charged particles is estimated. The coherence effect is due to the modulation, i.e. to periodicity in the particles distribution.
Charged particle interaction with a chirped electromagnetic pulse
Khachatryan, A.G.; Boller, Klaus J.; van Goor, F.A.
2003-01-01
It is found that a charged particle can get a net energy gain from the interaction with an electromagnetic chirped pulse. Theoretically, the energy gain increases with the pulse amplitude and with the relative frequency variation in the pulse.
Motion of charged particles in a knotted electromagnetic field
International Nuclear Information System (INIS)
Arrayas, M; Trueba, J L
2010-01-01
In this paper we consider the classical relativistic motion of charged particles in a knotted electromagnetic field. After reviewing how to construct electromagnetic knots from maps between the three-sphere and the two-sphere, we introduce a mean quadratic radius of the energy density distribution in order to study some properties of this field. We study the classical relativistic motion of electrons in the electromagnetic field of the Hopf map, and compute their trajectories. It is observed that these electrons initially at rest are strongly accelerated by the electromagnetic force, becoming ultrarelativistic in a period of time that depends on the knot energy and size.
Motion of charged particles in a knotted electromagnetic field
Energy Technology Data Exchange (ETDEWEB)
Arrayas, M; Trueba, J L, E-mail: joseluis.trueba@urjc.e [Area de Electromagnetismo, Universidad Rey Juan Carlos, Camino del Molino s/n, 28943 Fuenlabrada, Madrid (Spain)
2010-06-11
In this paper we consider the classical relativistic motion of charged particles in a knotted electromagnetic field. After reviewing how to construct electromagnetic knots from maps between the three-sphere and the two-sphere, we introduce a mean quadratic radius of the energy density distribution in order to study some properties of this field. We study the classical relativistic motion of electrons in the electromagnetic field of the Hopf map, and compute their trajectories. It is observed that these electrons initially at rest are strongly accelerated by the electromagnetic force, becoming ultrarelativistic in a period of time that depends on the knot energy and size.
Interaction of free charged particles with a chirped electromagnetic pulse
Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.
2004-01-01
We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM
The motion of a charged black hole in an electromagnetic field
International Nuclear Information System (INIS)
Bicak, J.; Cambridge Univ.
1980-01-01
The motion of a charged black hole in a weak, asymptotically uniform electric field is analysed by using the Hamiltonian formalism for coupled electromagnetic and gravitational perturbations of the Reissner-Nordstrom space-time. The hole is shown to accelerate with respect to a distant inertial observer according to Newton's law. The relation of the approximate solution obtained to the exact solution of Ernst, representing the charged C-metric without nodal singularity, is then clarified. (author)
Electromagnetic wave propagating along a space curve
Lai, Meng-Yun; Wang, Yong-Long; Liang, Guo-Hua; Wang, Fan; Zong, Hong-Shi
2018-03-01
By using the thin-layer approach, we derive the effective equation for the electromagnetic wave propagating along a space curve. We find intrinsic spin-orbit, extrinsic spin-orbit, and extrinsic orbital angular-momentum and intrinsic orbital angular-momentum couplings induced by torsion, which can lead to geometric phase, spin, and orbital Hall effects. And we show the helicity inversion induced by curvature that can convert a right-handed circularly polarized electromagnetic wave into a left-handed polarized one, vice versa. Finally, we demonstrate that the gauge invariance of the effective dynamics is protected by the geometrically induced gauge potential.
Multipole interactions of charged particles with the electromagnetic field
International Nuclear Information System (INIS)
Burzynski, A.
1982-01-01
The full multipole expansion for the lagrangian and hamiltonian of a system of point charges interacting with the electromagnetic field is studied in detail. Both classical and quantum theory are described for external and dynamical fields separately. One improvement with respect to the known Fiutak's paper is made. (author)
Interaction of free charged particles with a chirped electromagnetic pulse
International Nuclear Information System (INIS)
Khachatryan, A.G.; Goor, F.A. van; Boller, K.-J.
2004-01-01
We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles
Space charge in nanostructure resonances
Price, Peter J.
1996-10-01
In quantum ballistic propagation of electrons through a variety of nanostructures, resonance in the energy-dependent transmission and reflection probabilities generically is associated with (1) a quasi-level with a decay lifetime, and (2) a bulge in electron density within the structure. It can be shown that, to a good approximation, a simple formula in all cases connects the density of states for the latter to the energy dependence of the phase angles of the eigen values of the S-matrix governing the propagation. For both the Lorentzian resonances (normal or inverted) and for the Fano-type resonances, as a consequence of this eigen value formula, the space charge due to filled states over the energy range of a resonance is just equal (for each spin state) to one electron charge. The Coulomb interaction within this space charge is known to 'distort' the electrical characteristics of resonant nanostructures. In these systems, however, the exchange effect should effectively cancel the interaction between states with parallel spins, leaving only the anti-parallel spin contribution.
WSN-Based Space Charge Density Measurement System.
Deng, Dawei; Yuan, Haiwen; Lv, Jianxun; Ju, Yong
2017-01-01
It is generally acknowledged that high voltage direct current (HVDC) transmission line endures the drawback of large area, because of which the utilization of cable for space charge density monitoring system is of inconvenience. Compared with the traditional communication network, wireless sensor network (WSN) shows advantages in small volume, high flexibility and strong self-organization, thereby presenting great potential in solving the problem. Additionally, WSN is more suitable for the construction of distributed space charge density monitoring system as it has longer distance and higher mobility. A distributed wireless system is designed for collecting and monitoring the space charge density under HVDC transmission lines, which has been widely applied in both Chinese state grid HVDC test base and power transmission projects. Experimental results of the measuring system demonstrated its adaptability in the complex electromagnetic environment under the transmission lines and the ability in realizing accurate, flexible, and stable demands for the measurement of space charge density.
Space charge effects: tune shifts and resonances
International Nuclear Information System (INIS)
Weng, W.T.
1986-08-01
The effects of space charge and beam-beam interactions on single particle motion in the transverse degree of freedom are considered. The space charge force and the resulting incoherent tune shift are described, and examples are given from the AGS and CERN's PSB. Equations of motion are given for resonances in the presence of the space charge force, and particle behavior is examined under resonance and space charge conditions. Resonance phase space structure is described with and without space charge. Uniform and bunched beams are compared. Beam-beam forces and resonances and beam-beam detuning are described. 18 refs., 15 figs
International Nuclear Information System (INIS)
Wald, H.B.
1990-01-01
The 'PATH' codes are used to design magnetic optics subsystems for neutral particle beam systems. They include a 2-1/2D and three 3-D space charge models, two of which have recently been added. This paper describes the 3-D models and reports on preliminary benchmark studies in which these models are checked for stability as the cloud size is varied and for consistency with each other. Differences between the models are investigated and the computer time requirements for running these models are established
Longitudinal Phase Space Tomography with Space Charge
Hancock, S; Lindroos, M
2000-01-01
Tomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the non-linearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method is a hybrid one which incorporates particle tracking. Hitherto, a very simple tracking algorithm has been employed because only a brief span of measured profile data is required to build a snapshot of phase space. This is one of the strengths of the method, as tracking for relatively few turns relaxes the precision to which input machine parameters need to be known. The recent addition of longitudinal space charge considerations as an optional refinement of the code is described. Simplicity suggested an approach based on the derivative of bunch shape with the properties of...
The Status of Development of Electromagnetic Pumps for Space Application
International Nuclear Information System (INIS)
Kwak, J. S.; Kim, K. H.; Jeong, J. S.; Kim, Hee Reyoung
2013-01-01
Korea lunched this research as a part of the small nuclear power generation technology development for space. In this study, investigated are the basic principle and types of electromagnetic pump and the trend of electromagnetic pump technology development in foreign nations. The survey and analysis give the understanding of the suitability and prospect of electromagnetic pumps as space application technology in Korea. The analysis on the status of the development of electromagnetic pumps was carried out for the application to space environment. It was found that USA was approaching the research and development of electromagnetic pumps for space application. Most electromagnetic pumps surveyed have the efficiency between 35% and 50% where that of AC conduction pump is less than 6%. Further study was thought to have to be given for the mechanical and material characteristics, and the applicability of electromagnetic pumps for space nuclear reactor
Electromagnetic radiation in a semi-compact space
Iso, Satoshi; Kitazawa, Noriaki; Yokoo, Sumito
2018-02-01
In this note, we investigate the electromagnetic radiation emitted from a revolving point charge in a compact space. If the point charge is circulating with an angular frequency ω0 on the (x , y)-plane at z = 0 with boundary conditions, x ∼ x + 2 πR and y ∼ y + 2 πR, it emits radiation into the z-direction of z ∈ [ - ∞ , + ∞ ]. We find that the radiation shows discontinuities as a function of ω0 R at which a new propagating mode with a different Fourier component appears. For a small radius limit ω0 R ≪ 1, all the Fourier modes except the zero mode on (x , y)-plane are killed, but an effect of squeezing the electric field totally enhances the radiation. In the large volume limit ω0 R → ∞, the energy flux of the radiation reduces to the expected Larmor formula.
Charge quantization without superheavy masses in a Kaluza--Klein description of electromagnetism
International Nuclear Information System (INIS)
Ross, D.K.
1987-01-01
A scalar matter field coupled to general relativity and electromagnetism in a five-dimensional Kaluza--Klein model is considered. The five-dimensional space is assumed to be a fiber bundle as in the usual description of a gauge theory and not a more general manifold. Properly taking this into account allows one to use a Lagrangian density for the scalar field which includes charge quantization but not the unphysical superheavy masses found by other authors. A natural, satisfactory explanation of why charge is quantized results
Electromagnetic radiation of charged particles in stochastic motion
Energy Technology Data Exchange (ETDEWEB)
Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom); Mocanu, Gabriela [Astronomical Institute of the Romanian Academy, Cluj-Napoca (Romania)
2016-03-15
The study of the Brownian motion of a charged particle in electric and magnetic fields has many important applications in plasma and heavy ions physics, as well as in astrophysics. In the present paper we consider the electromagnetic radiation properties of a charged non-relativistic particle in the presence of electric and magnetic fields, of an exterior non-electromagnetic potential, and of a friction and stochastic force, respectively. We describe the motion of the charged particle by a Langevin and generalized Langevin type stochastic differential equation. We investigate in detail the cases of the Brownian motion with or without memory in a constant electric field, in the presence of an external harmonic potential, and of a constant magnetic field. In all cases the corresponding Langevin equations are solved numerically, and a full description of the spectrum of the emitted radiation and of the physical properties of the motion is obtained. The power spectral density of the emitted power is also obtained for each case, and, for all considered oscillating systems, it shows the presence of peaks, corresponding to certain intervals of the frequency. (orig.)
Startsev, Edward; Lee, Wei-li
2005-01-01
In intense charged particle beams with large energy anisotropy, free energy is available to drive transverse electromagnetic Weibel-type instabilities. Such slow-wave transverse electromagnetic instabilities can be described by the so-called Darwin model, which neglects the fast-wave portion of the displacement current. The Weibel instability may also lead to an increase in the longitudinal velocity spread, which would make the focusing of the beam difficult and impose a limit on the minimum spot size achievable in heavy ion fusion experiments. This paper reports the results of recent numerical studies of the Weibel instability using the Beam Eigenmode And Spectra (bEASt) code for space-charge-dominated, low-emittance beams with large tune depression. To study the nonlinear stage of the instability, the Darwin model is being developed and incorporated into the Beam Equilibrium Stability and Transport(BEST) code.
Scattering of Non-Relativistic Charged Particles by Electromagnetic Radiation
Apostol, M.
2017-11-01
The cross-section is computed for non-relativistic charged particles (like electrons and ions) scattered by electromagnetic radiation confined to a finite region (like the focal region of optical laser beams). The cross-section exhibits maxima at scattering angles given by the energy and momentum conservation in multi-photon absorption or emission processes. For convenience, a potential scattering is included and a comparison is made with the well-known Kroll-Watson scattering formula. The scattering process addressed in this paper is distinct from the process dealt with in previous studies, where the scattering is immersed in the radiation field.
Theory of charged vector mesons interacting with the electromagnetic field
International Nuclear Information System (INIS)
Lee, T.D.; Yang, C.N.
1983-01-01
It is shown that starting from the usual canonical formalism for the electromagnetic interaction of a charged vector meson with arbitrary magnetic moment one is led to a set of rules for Feynman diagrams, which appears to contain terms that are both infinite and noncovariant. These difficulties, however, can be circumvented by introducing a xi-limiting process which depends on a dimensionless positive parameter xi → 0. Furthermore, by using the mathematical artifice of a negative metric the theory becomes renormalizable (for xi > 0)
The Mathematics of Charged Particles interacting with Electromagnetic Fields
DEFF Research Database (Denmark)
Petersen, Kim
In this thesis, we study the mathematics used to describe systems of charged quantum mechanical particles coupled with their classical self-generated electromagnetic field. We prove the existence of a unique local in time solution to the many-body Maxwell-Schrödinger initial value problem expressed...... in Coulomb gauge and we show that the one-body Maxwell-Schrödinger system as well as the related one-body Maxwell-Pauli system both admit travelling wave solutions....
Direct convertor based upon space charge effects
International Nuclear Information System (INIS)
Gitomer, S.J.
1977-01-01
A device capable of converting directly the kinetic energy of charged particles into electrical energy is considered. The device differs from earlier ones (such as Post's periodic focus electrostatic direct convertor) in that it makes use of the space charge repulsion in a high density charged particle beam. The beam is directed into a monotonic decelerating electrostatic field of a several-stage planar-finned structure. The collector fins coincide with vacuum equipotential surfaces. Space charge blowup of the beam directs particles onto various collector fins. The energy efficiency of a 4-stage device has been determined using a numberical simulation approach. We find that efficiencies approaching 75 percent are possible. An approximate scaling law is derived for the space charge based direct converter and a comparison is made to the periodic focus direct convertor. We find the space charge based direct convertor to be superior to a number of ways
The modern trends in space electromagnetic instrumentation
Korepanov, V. E.
The future trends of the experimental plasma physics development in outer space demand more and more exact and sophisticated scientific instrumentation. Moreover, the situation is complicated by constant reduction of financial support of scientific research, even in leading countries. This resulted in the development of mini; micro and nanosatellites with low price and short preparation time. Consequently, it provoked the creation of new generation of scientific instruments with reduced weight and power consumption but increased level of metrological parameters. The recent state of the development of electromagnetic (EM) sensors for microsatellites is reported. For flux-gate magnetometers (FGM) the reduction of weight as well as power consumption was achieved not only due to the use of new electronic components but also because of the new operation mode development. The scientific and technological study allowed to decrease FGM noise and now the typical noise figure is about 10 picotesla rms at 1 Hz and the record one is below 1 picotesla. The super-light version of search-coil magnetometers (SCM) was created as the result of intensive research. These new SCMs can have about six decades of operational frequency band with upper limit ˜ 1 MHz and noise level of few femtotesla with total weight about 75 grams, including electronics. A new instrument.- wave probe (WP) - which combines three independent sensors in one body - SCM, split Langmuir probe and electric potential sensor - was created. The developed theory confirms that WP can directly measure the wave vector components in space plasmas.
International Nuclear Information System (INIS)
Holm, D.D.; Kupershmidt, B.A.
1987-01-01
Four levels of nonlinear hydrodynamic description are presented for a nondissipative multicondensate solution of superfluids with vorticity. First, the multivelocity superfluid (MVSF) theory is extended to the case of a multivelocity superfluid plasma (MVSP), in which some of the superfluid condensates (protons, say) are charged and coupled electromagnetically to an additional, normal, charged fluid (electrons). The resulting drag-current density is derived due to the electromagnetic coupling of the condensates with the normal fluids. For the case of one charged condensate, the MVSP equations simplify to what we call superfluid Hall magnetohydrodynamics (SHMHD) in the approximation that displacement current and electron inertia are negligible, and local charge neutrality is imposed. The contribution of the charged condensate to the Hall drift force is determined. In turn, neglecting the Hall effect in SHMHD gives the equations of superfluid magnetohydrodynamics (SMHD). Each set of equations (MVSF, MVSP, SHMHD, and SMHD) is shown to be Hamiltonian and to possess a Poisson bracket associated with the dual space of a corresponding semidirect-product Lie algebra with a generalized two-cocycle defined on it. Topological conservation laws (helicities) associated with the kernels of these Lie algebras are also discussed as well as those associated physically with generalized Kelvin theorems for conservation of superfluid circulation around closed loops moving with the normal fluid
Booted domain wall and charged Kaigorodov space
International Nuclear Information System (INIS)
Cai Ronggen
2003-01-01
The Kaigorodov space is a homogeneous Einstein space and it describes a pp-wave propagating in anti-de Sitter space. It is conjectured in the literature that M-theory or string theory on the Kaigorodov space times a compact manifold is dual to a conformal field theory in an infinitely-boosted frame with constant momentum density. In this Letter we present a charged generalization of the Kaigorodov space by boosting a non-extremal charged domain wall to the ultrarelativity limit where the boost velocity approaches the speed of light. The finite boost of the domain wall solution gives the charged generalization of the Carter-Novotny-Horsky metric. We study the thermodynamics associated with the charged Carter-Novotny-Horsky space and discuss its relation to that of the static black domain walls and its implications in the domain wall/QFT (quantum field theory) correspondence
Space Charge Mitigation by Hollow Bunches
Oeftiger, AO
2014-01-01
To satisfy the requirements of the HL-LHC (High Luminosity Large Hadron Collider), the LHC injector chain will need to supply a higher brightness, i.e. deliver the same transverse beam emittances \\epsilon_{x,y} while providing a higher intensity N. However, a larger number of particles per bunch enhances space charge effects. One approach to mitigate the impact of space charge is to change the longitudinal phase space distribution: hollow bunches feature a depleted bunch centre and a densely populated periphery. Thus, the spatial line density maximum is depressed which ultimately decreases the tune spread imposed by space charge. Therefore, a higher intensity can be accepted while keeping the same overall space charge tune shift. 3 different methods to create hollow bunches in the PSBooster are simulated.
Longitudinal Space Charge in the SPS
Lasheen, Alexandre
2016-01-01
Longitudinal instabilities due to the SPS beam coupling impedance are a major issue for future projects and it is essential to have an accurate SPS impedance model to study them. The longitudinal space charge effect can be modelled by a pure reactive impedance and should also be included in simulations as it may have an impact at low energy. In this Note, the effect of the longitudinal space charge in the SPS is evaluated by taking into account the variation of the transverse beam size and vacuum chamber geometry along the ring. Scaling laws are used to investigate what are the most important parameters for the evaluation of the longitudinal space charge impedance.
Designing localized electromagnetic fields in a source-free space
International Nuclear Information System (INIS)
Borzdov, George N.
2002-01-01
An approach to characterizing and designing localized electromagnetic fields, based on the use of differentiable manifolds, differentiable mappings, and the group of rotation, is presented. By way of illustration, novel families of exact time-harmonic solutions to Maxwell's equations in the source-free space - localized fields defined by the rotation group - are obtained. The proposed approach provides a broad spectrum of tools to design localized fields, i.e., to build-in symmetry properties of oscillating electric and magnetic fields, to govern the distributions of their energy densities (both size and form of localization domains), and to set the structure of time-average energy fluxes. It is shown that localized fields can be combined as constructive elements to obtain a complex field structure with desirable properties, such as one-, two-, or three-dimensional field gratings. The proposed approach can be used in designing localized electromagnetic fields to govern motion and state of charged and neutral particles. As an example, motion of relativistic electrons in one-dimensional and three-dimensional field gratings is treated
EGUN, Charged Particle Trajectories in Electromagnetic Focusing System
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.
2002-01-01
1 - Description of problem or function: EGUN computes trajectories of charged particles in electrostatic and magnetostatic focusing systems including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes of various shapes, user-specified conditions input for each ray, and a combination of Child's Law conditions and user specifications. Either rectangular or cylindrically symmetric geometry may be used. Magnetic fields may be specified using an arbitrary configuration of coils, or the output of a magnet program, such as Poisson, or by an externally calculated array of the axial fields. 2 - Method of solution: The program first solves Laplace's equation. Next, the first iteration of electron trajectories is started using one of the four starting options. On the first iteration cycle, space charge forces are calculated from the assumption of paraxial flow. As the rays are traced, space charge is computed and stored. After all the electron trajectories have been calculated, the program begins the second cycle by solving the Poisson equation with the space charge from the first iteration. Subsequent iteration cycles follow this pattern. The Poisson equation is solved by an alternate column relaxation technique known as the semi-iterative Chebyshev method. A fourth-order Runge-Kutta method is used to solve the relativistic differential equations of the trajectory calculations. 3 - Restrictions on the complexity of the problem - Maxima of: 9001 mesh points in a square mesh, 300 mesh points in the axial direction, 100 mesh points in the radial direction, 101 potentials, 51 rays. In the cylindrical coordinates, the magnetic fields are axially symmetric. In rectangular coordinates, the external field is assumed to be normal to the plane of the problem, which is assumed to be the median plane
Non-linear diffusion of charged particles due to stochastic electromagnetic fields
International Nuclear Information System (INIS)
Martins, A.M.; Balescu, R.; Mendonca, J.T.
1989-01-01
It is well known that the energy confinement times observed in tokamak cannot be explained by the classical or neo-classical transport theory. The alternative explanations are based on the existence of various kinds of micro-instabilities, or on the stochastic destruction of the magnetic surfaces, due to the interaction of magnetic islands of different helicities. In the absence of a well established theory of anomalous transport it is perhaps important to study in some detail the diffusion coefficient of single charged particles in the presence of electromagnetic fluctuation, because it can provide the physical grounds for more complete and self-consistent calculations. In the present work we derive a general expression for the transverse diffusion coefficient of electrons and ions in a constant magnetic field and in the presence of space and time dependent electromagnetic fluctuation. We neglect macroscopic drifts due to inhomogeneity and field curvatures, but retain finite Larmor radius effects. (author) 3 refs
Self-excitation of space charge waves
DEFF Research Database (Denmark)
Lyuksyutov, Sergei; Buchhave, Preben; Vasnetsov, Mikhail
1997-01-01
We report a direct observation of space charge waves in photorefractive crystals with point group 23 (sillenites) based on their penetration into an area with uniform light illumination. It is shown experimentally that the quality factor of the waves increases substantially with respect to what c...... current theory predicts [B. Sturman el al., Appl. Phys. A 55, 235 (1992)]. This results in the appearance of strong spontaneous beams caused by space charge wave self-excitation....
Charge radii and electromagnetic moments of At-211195
Cubiss, J. G.; Barzakh, A. E.; Seliverstov, M. D.; Andreyev, A. N.; Andel, B.; Antalic, S.; Ascher, P.; Atanasov, D.; Beck, D.; Bieroń, J.; Blaum, K.; Borgmann, Ch.; Breitenfeldt, M.; Capponi, L.; Cocolios, T. E.; Day Goodacre, T.; Derkx, X.; De Witte, H.; Elseviers, J.; Fedorov, D. V.; Fedosseev, V. N.; Fritzsche, S.; Gaffney, L. P.; George, S.; Ghys, L.; Heßberger, F. P.; Huyse, M.; Imai, N.; Kalaninová, Z.; Kisler, D.; Köster, U.; Kowalska, M.; Kreim, S.; Lane, J. F. W.; Liberati, V.; Lunney, D.; Lynch, K. M.; Manea, V.; Marsh, B. A.; Mitsuoka, S.; Molkanov, P. L.; Nagame, Y.; Neidherr, D.; Nishio, K.; Ota, S.; Pauwels, D.; Popescu, L.; Radulov, D.; Rapisarda, E.; Revill, J. P.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Sandhu, K.; Schweikhard, L.; Sels, S.; Truesdale, V. L.; Van Beveren, C.; Van den Bergh, P.; Wakabayashi, Y.; Van Duppen, P.; Wendt, K. D. A.; Wienholtz, F.; Whitmore, B. W.; Wilson, G. L.; Wolf, R. N.; Zuber, K.
2018-05-01
Hyperfine-structure parameters and isotope shifts of At-211195 have been measured for the first time at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy method. The hyperfine structures of isotopes were recorded using a triad of experimental techniques for monitoring the photo-ion current. The Multi-Reflection Time-of-Flight Mass Spectrometer, in connection with a high-resolution electron multiplier, was used as an ion-counting setup for isotopes that either were affected by strong isobaric contamination or possessed a long half-life; the ISOLDE Faraday cups were used for cases with high-intensity beams; and the Windmill decay station was used for short-lived, predominantly α -decaying nuclei. The electromagnetic moments and changes in the mean-square charge radii of the astatine nuclei have been extracted from the measured hyperfine-structure constants and isotope shifts. This was only made possible by dedicated state-of-the-art large-scale atomic computations of the electronic factors and the specific mass shift of atomic transitions in astatine that are needed for these extractions. By comparison with systematics, it was possible to assess the reliability of the results of these calculations and their ascribed uncertainties. A strong deviation in the ground-state mean-square charge radii of the lightest astatine isotopes, from the trend of the (spherical) lead isotopes, is interpreted as the result of an onset of deformation. This behavior bears a resemblance to the deviation observed in the isotonic polonium isotopes. Cases for shape coexistence have been identified in At,199197, for which a significant difference in the charge radii for ground (9 /2- ) and isomeric (1 /2+ ) states has been observed.
Stability of anisotropic beams with space charge
International Nuclear Information System (INIS)
Hofmann, I.
1997-07-01
We calculate coherent frequencies and stability properties of anisotropic or ''non-equipartitioned'' beams with different focusing constants and emittances in the two transverse directions. Based on the self-consistent Vlasov-Poisson equations the dispersion relations of transverse multipole oscillations with quadrupolar, sextupolar and octupolar symmetry are solved numerically. The eigenfrequencies give the coherent space charge tune shift for linear or nonlinear resonances in circular accelerators. We find that for sufficiently large energy anisotropy some of the eigenmodes become unstable in the space-charge-dominated regime. The properties of these anisotropy instabilities are used to show that ''non-equipartitioned'' beams can be tolerated in high-current linear accelerators. It is only in beams with strongly space-charge-depressed betatron tunes where harmful instabilities leading to emittance exchange should be expected. (orig.)
Space-charge calculations in synchrotrons
Energy Technology Data Exchange (ETDEWEB)
Machida, S.
1993-05-01
One obvious bottleneck of achieving high luminosity in hadron colliders, such as the Superconducting Super Collider (SSC), is the beam emittance growth, due to space-charge effects in low energy injector synchrotrons. Although space-charge effects have been recognized since the alternating-gradient synchrotron was invented, and the Laslett tune shift usually calculated to quantify these effects, our understanding of the effects is limited, especially when the Laslett tune shift becomes a large fraction of the integer. Using the Simpsons tracking code, which we developed to study emittance preservation issues in proton synchrotrons, we investigated space-charge effects in the SSC Low Energy Booster (LEB). We observed detailed dependence on parameters such as beam intensity, initial emittance, injection energy, lattice function, and longitudinal motion. A summary of those findings, as well as the tracking technique we developed for the study, are presented.
Space charge effects in proton linear accelerators
International Nuclear Information System (INIS)
Prome, Michel
1971-01-01
Space charge difficulties are relatively well known because of the inconveniences they cause, but the physical mechanisms by which they operate are obscure; an attempt was made to explain some of these mechanisms. The method chosen involves a numerical simulation of the beam; computer programs describing beam dynamics with space charge are presented; they are used to check results obtained elsewhere. A series of experiments was performed demonstrating that coupling phenomena produce an equalization of r. m. s. velocities in the 3 directions; new quantity (sort of hyper-emittance) is introduced: its growth between the input and output of a given linac is proportional to the beam intensity. (author) [fr
Space Charge Mitigation With Longitudinally Hollow Bunches
Oeftiger, Adrian; Rumolo, Giovanni
2016-01-01
Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN’s PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.
Charge conjugation and internal space time symmetries
International Nuclear Information System (INIS)
Pavsic, M.; Recami, E.
1982-01-01
The relativistic framework in which fundamental particles are regarded as extended objects is adopted. Then it is shown than the geometrical operation which reflects the internal space time particle is equivalent to the operation C which inverts the sign of all its additive charges
Space charge effect in the spiral inflector
International Nuclear Information System (INIS)
Toprek, Dragan
2000-01-01
This paper presents the analytical and numerical theory of the space charge effects in the beam in the spiral inflector. It considers a simplified model of a 'straight' cylindrical beam by using a uniform particle distribution. Numerical results represented in this paper are obtained by using a modified version of the program CASINO
Research on Efficiency of Contactless Charging System based on Electromagnetic Induction
Directory of Open Access Journals (Sweden)
Chen Jianshu
2016-01-01
Full Text Available For the efficiency problem of contactless charging in type of electromagnetic induction, this paper establishes a mathematical model of contactless charging in type of electromagnetic induction and the theoretical derivation. This contactless charging simulation model is founded by Matlab/Simulink, which uses the frequency of PWM generator, the mutual inductance value of the coil and load resistance of RL to simulate some conditions, such as the working frequency in practical work, the distance of coil, whether the coils are directed at the central, and changing of loads. Then through the influence of the changing frequency, load and mutual inductance, contactless charging in type of electromagnetic induction is analyzed. By the whole simulation experiment on contactless charging, the theory deduced from the mathematical model is verified, and the method to improve inductive contactless charging is proved.
Hughes, J.; Schaub, H.
2017-12-01
Spacecraft can charge to very negative voltages at GEO due to interactions with the space plasma. This can cause arcing which can damage spacecraft electronics or solar panels. Recently, it has been suggested that spacecraft charging may lead to orbital perturbations which change the orbits of lightweight uncontrolled debris orbits significantly. The motions of High Area to Mass Ratio objects are not well explained with just perturbations from Solar Radiation Pressure (SRP) and earth, moon, and sun gravity. A charged spacecraft will experience a Lorentz force as the spacecraft moves relative to Earth's magnetic field, as well as a Lorentz torque and eddy current torques if the object is rotating. Prior work assuming a constant "worst case" voltage has shown that Lorentz and eddy torques can cause quite large orbital changes by rotating the object to experience more or less SRP. For some objects, including or neglecting these electromagnetic torques can lead to differences of thousands of kilometers after only two orbits. This paper will further investigate the effects of electromagnetic perturbations by using a charging model that uses measured flux distributions to better simulate natural charging. This differs from prior work which used a constant voltage or Maxwellian distributions. This is done to a calm space weather case of Kp = 2 and a stormy case where Kp = 8. Preliminary analysis suggests that electrostatics will still cause large orbital changes even with the more realistic charging model.
Three-dimensional space charge calculation method
International Nuclear Information System (INIS)
Lysenko, W.P.; Wadlinger, E.A.
1981-01-01
A method is presented for calculating space-charge forces suitable for use in a particle tracing code. Poisson's equation is solved in three dimensions with boundary conditions specified on an arbitrary surface by using a weighted residual method. Using a discrete particle distribution as our source input, examples are shown of off-axis, bunched beams of noncircular crosssection in radio-frequency quadrupole (RFQ) and drift-tube linac geometries
Loop-space quantum formulation of free electromagnetism
International Nuclear Information System (INIS)
Di Bartolo, C.; Nori, F.; Gambini, R.; Trias, A.
1983-01-01
A procedure for direct quantization of free electromagnetism in the loop-space is proposed. Explicit solutions for the loop-dependent vacuum and the Wilson loop-average are given. It is shown that elementary lines of magnetic field appear as extremals in the vacuum state as a result of the regularization procedure
Norbury, John W.
1989-01-01
The invariance of classical electromagnetism under charge-conjugation, parity, and time-reversal (CPT) is studied by considering the motion of a charged particle in electric and magnetic fields. Upon applying CPT transformations to various physical quantities and noting that the motion still behaves physically demonstrates invariance.
Effect of frequency variation on electromagnetic pulse interaction with charges and plasma
Khachatryan, A.G.; van Goor, F.A.; Verschuur, Jeroen W.J.; Boller, Klaus J.
2005-01-01
The effect of frequency variation (chirp) in an electromagnetic (EM) pulse on the pulse interaction with a charged particle and plasma is studied. Various types of chirp and pulse envelopes are considered. In vacuum, a charged particle receives a kick in the polarization direction after interaction
Measuring Intrinsic Curvature of Space with Electromagnetism
Mabin, Mason; Becker, Maria; Batelaan, Herman
2016-01-01
The concept of curved space is not readily observable in everyday life. The educational movie "Sphereland" attempts to illuminate the idea. The main character, a hexagon, has to go to great lengths to prove that her world is in fact curved. We present an experiment that demonstrates a new way to determine if a two-dimensional surface,…
Buchholz, Detlev; Ciolli, Fabio; Ruzzi, Giuseppe; Vasselli, Ezio
2017-02-01
Conditions for the appearance of topological charges are studied in the framework of the universal C*-algebra of the electromagnetic field, which is represented in any theory describing electromagnetism. It is shown that non-trivial topological charges, described by pairs of fields localised in certain topologically non-trivial spacelike separated regions, can appear in regular representations of the algebra only if the fields depend non-linearly on the mollifying test functions. On the other hand, examples of regular vacuum representations with non-trivial topological charges are constructed, where the underlying field still satisfies a weakened form of "spacelike linearity". Such representations also appear in the presence of electric currents. The status of topological charges in theories with several types of electromagnetic fields, which appear in the short distance (scaling) limit of asymptotically free non-abelian gauge theories, is also briefly discussed.
Nonlinear space charge effect of bunched beam in linac
International Nuclear Information System (INIS)
Chen Yinbao
1992-02-01
The nonlinear space charge effect due to the nonuniform particle density distribution in bunched beam of a linac is discussed. The formulae of nonlinear space charge effect and nonlinear focusing forces were derived for the bunched beam with Kapchinskij-Vladimirskij (K-V) distribution, waterbag (WB) distribution, parabolic (PA) distribution, and Gauss (GA) distribution in both of the space charge disk model and space charge cylinder model in the waveguide of a linac
Space-charge limits in linear accelerators
International Nuclear Information System (INIS)
Wangler, T.P.
1980-12-01
This report presents equations that allow an approximate evaluation of the limiting beam current for a large class of radio-frequency linear accelerators, which use quadrupole strong focusing. Included are the Alvarez, the Wideroe, and the radio-frequency quadrupole linacs. The limiting-current formulas are presented for both the longitudinal and the transverse degrees of freedom by assuming that the average space-charge force in the beam bunch arises from a uniformly distributed charge within an azimuthally symmetric three-dimensional ellipsoid. The Mathieu equation is obtained as an approximate, but general, form for the transverse equation of motion. The smooth-approximation method is used to obtain a solution and an expression for the transverse current limit. The form of the current-limit formulas for different linac constraints is discussed
Stasis, Charging the Space of Change
Directory of Open Access Journals (Sweden)
Sarah Riviere
2017-02-01
Full Text Available This article fossicks through the fragments of historical understandings of the word stasis in ancient Greece – where stasis, in its extreme state, involved conflictual hostilities between kindred parties, often termed ‘civil war’ today. Through a series of readings of ancient Greek texts on topics ranging from pathology to literature and politics, stasis is revealed as a powerfully charged state of located dynamic exchange that operates through a precise temporal and spatial performance. This article teases out relevant aspects of the state of stasis – its high levels of spatial engagement, its inevitable resolution into energetic productivity, its precise restraint, its demand for full participation, and its role in the integration of change – all of which were acknowledged as part of the enactment and resolution of a stasis at that time. The intention of this article is to resurrect a more nuanced understanding of the state of stasis that can enrich current concepts of the dynamic in architectural and urban discourse. This understanding of stasis also poses new questions for the future design of spaces that can accommodate charged kindred engagement: lively spaces where contest becomes opportunity, and located spaces of kindred understanding that promise productive reconciliation as the common aim of all the parties involved.
Chaotic behaviour induced by space charge
International Nuclear Information System (INIS)
Lagniel, J.M.
1994-01-01
In numerous non-linear dynamical systems studied in various disciplines (fluid dynamics, celestial mechanisms, chemistry, biology, economy, ecology...), chaotic motions are generated by the dynamics itself whereas no random force is present. This phenomenon, already studied in the particle accelerator field to understand the beam-beam effect, is also observed in numerical experiments on space-charge dominated beams. Stochasticity threshold and halo formation are discussed for a continuous focusing channel (1D beam) and for a FODO channel (2D beam) with the possibility to take into account the defocusing effects of RF gaps localized between the quadrupoles. (authors). 7 refs., 4 figs
Parametric Landau damping of space charge modes
Energy Technology Data Exchange (ETDEWEB)
Macridin, Alexandru [Fermilab; Burov, Alexey [Fermilab; Stern, Eric [Fermilab; Amundson, James [Fermilab; Spentzouris, Panagiotis [Fermilab
2016-09-23
Landau damping is the mechanism of plasma and beam stabilization; it arises through energy transfer from collective modes to the incoherent motion of resonant particles. Normally this resonance requires the resonant particle's frequency to match the collective mode frequency. We have identified an important new damping mechanism, parametric Landau damping, which is driven by the modulation of the mode-particle interaction. This opens new possibilities for stability control through manipulation of both particle and mode-particle coupling spectra. We demonstrate the existence of parametric Landau damping in a simulation of transverse coherent modes of bunched accelerator beams with space charge.
Space charge physics for particle accelerators
Hofmann, Ingo
2017-01-01
Understanding and controlling the physics of space charge effects in linear and circular proton and ion accelerators are essential to their operation, and to future high-intensity facilities. This book presents the status quo of this field from a theoretical perspective, compares analytical approaches with multi-particle computer simulations and – where available – with experiments. It discusses fundamental concepts of phase space motion, matched beams and modes of perturbation, along with mathematical models of analysis – from envelope to Vlasov-Poisson equations. The main emphasis is on providing a systematic description of incoherent and coherent resonance phenomena; parametric instabilities and sum modes; mismatch and halo; error driven resonances; and emittance exchange due to anisotropy, as well as the role of Landau damping. Their distinctive features are elaborated in the context of numerous sample simulations, and their potential impacts on beam quality degradation and beam loss are discussed....
Capture of charged particles by transverse electromagnetic waves
Energy Technology Data Exchange (ETDEWEB)
Davydovskii, V Ya; Sapogin, V G; Ukolov, A S
1975-01-01
An estimate is made of the maximum possible number of resonance particles interacting with a plane, transverse electromagnetic wave. The estimate is obtained by means of a distribution function, which is expressed in terms of the integrals of motion of the particles in the wave. Values of proton fluxes accelerated by an amplitude-modulated wave in the solar corona coincide with those observed during bursts of sporadic radioemission. (SJR)
Quantum noise on a point charge from electromagnetic squeezed vacuum fluctuations
International Nuclear Information System (INIS)
Wu, Tai-Hung; Hsiang, Jen-Tsung; Lee, Da-Shin
2010-01-01
The effect of quantum noises on a point charge from electromagnetic squeezed vacuum fluctuations is studied. Here a novel reduction phenomenon in velocity dispersion is found in the situation when the particle barely moves. It shows that the velocity dispersion of the charge can be reduced below the value solely given by the normal vacuum states of the electromagnetic fields by using an appropriate choice of the squeeze parameters. This may be viewed as a transient phenomenon. Optimally utilizing this reduction scheme for gravitational wave detection is possible, but challenging.
Quantum noise on a point charge from electromagnetic squeezed vacuum fluctuations
Energy Technology Data Exchange (ETDEWEB)
Wu, Tai-Hung; Hsiang, Jen-Tsung; Lee, Da-Shin [National Dong-Hwa University, Hua-lien, Taiwan (China)
2010-09-15
The effect of quantum noises on a point charge from electromagnetic squeezed vacuum fluctuations is studied. Here a novel reduction phenomenon in velocity dispersion is found in the situation when the particle barely moves. It shows that the velocity dispersion of the charge can be reduced below the value solely given by the normal vacuum states of the electromagnetic fields by using an appropriate choice of the squeeze parameters. This may be viewed as a transient phenomenon. Optimally utilizing this reduction scheme for gravitational wave detection is possible, but challenging.
Preliminary analysis of space mission applications for electromagnetic launchers
Miller, L. A.; Rice, E. E.; Earhart, R. W.; Conlon, R. J.
1984-01-01
The technical and economic feasibility of using electromagnetically launched EML payloads propelled from the Earth's surface to LEO, GEO, lunar orbit, or to interplanetary space was assessed. Analyses of the designs of rail accelerators and coaxial magnetic accelerators show that each is capable of launching to space payloads of 800 KG or more. A hybrid launcher in which EML is used for the first 2 KM/sec followed by chemical rocket stages was also tested. A cost estimates study shows that one to two EML launches per day are needed to break even, compared to a four-stage rocket. Development models are discussed for: (1) Earth orbital missions; (2) lunar base supply mission; (3) solar system escape mission; (4) Earth escape missions; (5) suborbital missions; (6) electromagnetic boost missions; and (7) space-based missions. Safety factors, environmental impacts, and EML systems analysis are discussed. Alternate systems examined include electrothermal thrustors, an EML rocket gun; an EML theta gun, and Soviet electromagnetic accelerators.
Zhang, Ruili; Wang, Yulei; He, Yang; Xiao, Jianyuan; Liu, Jian; Qin, Hong; Tang, Yifa
2018-02-01
Relativistic dynamics of a charged particle in time-dependent electromagnetic fields has theoretical significance and a wide range of applications. The numerical simulation of relativistic dynamics is often multi-scale and requires accurate long-term numerical simulations. Therefore, explicit symplectic algorithms are much more preferable than non-symplectic methods and implicit symplectic algorithms. In this paper, we employ the proper time and express the Hamiltonian as the sum of exactly solvable terms and product-separable terms in space-time coordinates. Then, we give the explicit symplectic algorithms based on the generating functions of orders 2 and 3 for relativistic dynamics of a charged particle. The methodology is not new, which has been applied to non-relativistic dynamics of charged particles, but the algorithm for relativistic dynamics has much significance in practical simulations, such as the secular simulation of runaway electrons in tokamaks.
Charge distributions in transverse coordinate space and in impact parameter space
Energy Technology Data Exchange (ETDEWEB)
Hwang, Dae Sung [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of)], E-mail: dshwang@slac.stanford.edu; Kim, Dong Soo [Department of Physics, Kangnung National University, Kangnung 210-702 (Korea, Republic of); Kim, Jonghyun [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of)
2008-11-27
We study the charge distributions of the valence quarks inside nucleon in the transverse coordinate space, which is conjugate to the transverse momentum space. We compare the results with the charge distributions in the impact parameter space.
Charge distributions in transverse coordinate space and in impact parameter space
Hwang, Dae Sung; Kim, Dong Soo; Kim, Jonghyun
2008-01-01
We study the charge distributions of the valence quarks inside nucleon in the transverse coordinate space, which is conjugate to the transverse momentum space. We compare the results with the charge distributions in the impact parameter space.
Space Charge Correction on Emittance Measurement of Low Energy Electron Beams
Energy Technology Data Exchange (ETDEWEB)
Treado, Colleen J.; /Massachusetts U., Amherst
2012-09-07
The goal of any particle accelerator is to optimize the transport of a charged particle beam along a set path by confining the beam to a small region close to the design trajectory and directing it accurately along the beamline. To do so in the simplest fashion, accelerators use a system of magnets that exert approximately linear electromagnetic forces on the charged beam. These electromagnets bend the beam along the desired path, in the case of bending magnets, and constrain the beam to the desired area through alternating focusing and defocusing effects, in the case of quadrupole magnets. We can model the transport of such a beam through transfer matrices representing the actions of the various beamline elements. However, space charge effects, produced from self electric fields within the beam, defocus the beam and must be accounted for in the calculation of beam emittance. We present below the preliminary results of a MATLAB code built to model the transport of a charged particle beam through an accelerator and measure the emittance under the influence of space charge effects. We demonstrate the method of correctly calculating the emittance of a beam under space charge effects using a least square fit to determine the initial properties of the beam given the beam size measured at a specific point after transport.
Alternating phase focussing including space charge
International Nuclear Information System (INIS)
Cheng, W.H.; Gluckstern, R.L.
1992-01-01
Longitudinal stability can be obtained in a non-relativistic drift tube accelerator by traversing each gap as the rf accelerating field rises. However, the rising accelerating field leads to a transverse defocusing force which is usually overcome by magnetic focussing inside the drift tubes. The radio frequency quadrupole is one way of providing simultaneous longitudinal and transverse focusing without the use of magnets. One can also avoid the use of magnets by traversing alternate gaps between drift tubes as the field is rising and falling, thus providing an alternation of focussing and defocusing forces in both the longitudinal and transverse directions. The stable longitudinal phase space area is quite small, but recent efforts suggest that alternating phase focussing (APF) may permit low velocity acceleration of currents in the 100-300 ma range. This paper presents a study of the parameter space and a test of crude analytic predictions by adapting the code PARMILA, which includes space charge, to APF. 6 refs., 3 figs
Space charge emission in cylindrical diode
International Nuclear Information System (INIS)
Torres-Córdoba, Rafael; Martínez-García, Edgar
2014-01-01
In this paper, a mathematical model to describe cylindrical electron current emissions through a physics approximation method is presented. The proposed mathematical approximation consists of analyzing and solving the nonlinear Poisson's equation, with some determined mathematical restrictions. Our findings tackle the problem when charge-space creates potential barrier that disable the steady-state of the beam propagation. In this problem, the potential barrier effects of electron's speed with zero velocity emitted through the virtual cathode happens. The interaction between particles and the virtual cathode have been to find the inter-atomic potentials as boundary conditions from a quantum mechanics perspective. Furthermore, a non-stationary spatial solution of the electrical potential between anode and cathode is presented. The proposed solution is a 2D differential equation that was linearized from the generalized Poisson equation. A single condition was used solely, throughout the radial boundary conditions of the current density formation
Space Charge Modules for PyHEADTAIL
Oeftiger, Adrian
2016-01-01
PyHEADTAIL is a 6D tracking tool developed at CERN to simulate collective effects. We present recent developments of the direct space charge (SC) suite, which is available for both the CPU and GPU. A new 3D particle-in-cell solver with open boundary conditions has been implemented. For the transverse plane, there is a semi-analytical Bassetti-Erskine model as well as 2D self-consistent particle-in-cell solvers with both open and closed boundary conditions. For the longitudinal plane, PyHEADTAIL offers line density derivative models. Simulations with these models are benchmarked with experiments at the injection plateau of CERN’s SPS.
Space charge effects and electronic bistability
International Nuclear Information System (INIS)
Ruffini, A.; Strumia, F.; Tommasi, O.
1996-01-01
The excitation of metastable states in an atomic beam apparatus by means of electron collision is a widespread technique. The authors have observed a large bistable behaviour in apparatus designed to provide an intense and collimated beam of metastable helium by excitation with orthogonally impinging electrons. This bistable behaviour largely affects the efficiency of the apparatus and is therefore worth of being carefully investigated. The apparatus has an electrode configuration equivalent to that of a tetrode valve with large intergrid distances. The bistability consists in a hysteresis cycle in the curve of the anode current vs. grid voltage. Experimental measurements, supported by a simple theoretical model and by numerical simulation, stress out the crucial role played by space charge effects for the onset of bistability. A comparison with previous observations of this phenomenon is given. Spontaneous current oscillations with various shapes have been recorded in one of the two curves of the hysteresis cycle
Motion of Charged Particles in Electromagnetic Fields and Special
Indian Academy of Sciences (India)
charged particles as seen from different inertial frames of reference. ... is solved for various initial conditions of the values of q,. --t -+. -+ m,o, E, v and B to be .... on the choice of the particular frame of reference that is employed to describe the ...
Lie symmetries for charged particles in the presence of a general electromagnetic field
International Nuclear Information System (INIS)
Medeiros Ritter, Oswaldo de.
1991-10-01
We discuss the Lie method and apply it to differential equations obtaining their symmetries. We also discuss methods of how to obtain first integrals from these symmetries. We apply these methods to some interesting physical problems, all of them involving charged particles in electromagnetic fields. (author). 77 refs
Coupled heat-electromagnetic simulation of inductive charging stations for electric vehicles
Kaufmann, C.; Günther, M.; Klagges, D.; Richwin, M.; Schöps, S.; Maten, ter E.J.W.
2012-01-01
Coupled electromagnetic-heat problems have been studied for induction or inductive heating, for dielectric heating, for testing of corrosion, for detection of cracks, for hardening of steel, and more recently for inductive charging of electric vehicles. In nearly all cases a simple co-simulation is
Coupled heat-electromagnetic simulation of inductive charging stations for electric vehicles
Kaufmann, C.; Günther, M.; Klagges, D.; Richwin, M.; Schöps, S.; Maten, ter E.J.W.; Fontes, M.; Günther, M.; Marheineke, N.
2014-01-01
Coupled electromagnetic-heat problems have been studied for induction or inductive heating, for dielectric heating, for testing of corrosion, for detection of cracks, for hardening of steel, and more recently for inductive charging of electric vehicles. In nearly all cases a simple co-simulation is
Quantum phases for a charged particle and electric/magnetic dipole in an electromagnetic field
Kholmetskii, Alexander; Yarman, Tolga
2017-11-01
We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic field must be composed from more fundamental quantum phases emerging for moving elementary charges. Using this idea, we have found two new fundamental quantum phases, next to the known magnetic and electric Aharonov-Bohm phases, and discuss their general properties and physical meaning.
On the Electromagnetic Momentum of Static Charge and Steady Current Distributions
Gsponer, Andre
2007-01-01
Faraday's and Furry's formulae for the electromagnetic momentum of static charge distributions combined with steady electric current distributions are generalized in order to obtain full agreement with Poynting's formula in the case where all fields are of class C[superscript 1], i.e., continuous and continuously differentiable, and the…
Dielectric sample with two-layer charge distribution for space charge calibration purposes
DEFF Research Database (Denmark)
Holbøll, Joachim; Henriksen, Mogens; Rasmussen, C.
2002-01-01
In the present paper is described a dielectric test sample with two very narrow concentrations of bulk charges, achieved by two internal electrodes not affecting the acoustical properties of the sample, a fact important for optimal application of most space charge measuring systems. Space charge...
Surface charges for gravity and electromagnetism in the first order formalism
Frodden, Ernesto; Hidalgo, Diego
2018-02-01
A new derivation of surface charges for 3 + 1 gravity coupled to electromagnetism is obtained. Gravity theory is written in the tetrad-connection variables. The general derivation starts from the Lagrangian, and uses the covariant symplectic formalism in the language of forms. For gauge theories, surface charges disentangle physical from gauge symmetries through the use of Noether identities and the exactness symmetry condition. The surface charges are quasilocal, explicitly coordinate independent, gauge invariant and background independent. For a black hole family solution, the surface charge conservation implies the first law of black hole mechanics. As a check, we show the first law for an electrically charged, rotating black hole with an asymptotically constant curvature (the Kerr–Newman (anti-)de Sitter family). The charges, including the would-be mass term appearing in the first law, are quasilocal. No reference to the asymptotic structure of the spacetime nor the boundary conditions is required and therefore topological terms do not play a rôle. Finally, surface charge formulae for Lovelock gravity coupled to electromagnetism are exhibited, generalizing the one derived in a recent work by Barnich et al Proc. Workshop ‘ About Various Kinds of Interactions’ in honour of Philippe Spindel (4–5 June 2015, Mons, Belgium) C15-06-04 (2016 (arXiv:1611.01777 [gr-qc])). The two different symplectic methods to define surface charges are compared and shown equivalent.
Electromagnetic energy and momentum from a charged particle
International Nuclear Information System (INIS)
Marx, E.
1975-01-01
The flux of the stress-energy tensor across a tube surrounding the world line of a charged particle is computed. By slight modifications of the definition of the Coulomb energy-momentum, the resulting expression contains the radiation reaction term (proportional to the square of the four-acceleration) but not the Schott term (proportional to the derivative of the acceleration). The equation of motion for the particle derived from this expression implies a variable rest mass. (author)
Space charge tracking code for a synchrotron accelerator
Energy Technology Data Exchange (ETDEWEB)
Ottinger, M.B.; Tajima, T. [Univ. of Texas, Austin, TX (United States); Hiramoto, K. [Hitachi Ltd., Hitachi, Ibaraki (Japan). Hitachi Research Lab.
1997-06-01
An algorithm has been developed to compute particle tracking, including self-consistent space charge effects for synchrotron accelerators. In low-energy synchrotrons space charge plays a central role in enhancing emittance of the beam. The space charge effects are modeled by mutually interacting (through the Coulombic force) N cylindrical particles (2-{1/2}-dimensional dynamics) whose axis is in the direction of the equilibrium particle flow. On the other hand, their interaction with synchrotron lattice magnets is treated with the thin-lens approximation and in a fully 3-dimensional way. Since the existing method to treat space charge fully self-consistently involved 3-D space charge effect computation, the present method allows far more realistic physical parameters and runs in far shorter time (about 1/20). Some examples on space charge induced instabilities are presented.
Space telescopes capturing the rays of the electromagnetic spectrum
English, Neil
2017-01-01
Space telescopes are among humankind’s greatest scientific achievements of the last fifty years. This book describes the instruments themselves and what they were designed to discover about the Solar System and distant stars. Exactly how these telescopes were built and launched and the data they provided is explored. Only certain kinds of radiation can penetrate our planet's atmosphere, which limits what we can observe. But with space telescopes all this changed. We now have the means to "see" beyond Earth using ultraviolet, microwave, and infrared rays, X-rays and gamma rays. In this book we meet the pioneers and the telescopes that were built around their ideas. This book looks at space telescopes not simply chronologically but also in order of the electromagnetic spectrum, making it possible to understand better why they were made.
Measurement of the Charged Pion Electromagnetic Form Factor
International Nuclear Information System (INIS)
J. Volmer; David Abbott; H. Anklin; Chris Armstrong; John Arrington; K. Assamagan; Steven Avery; Oliver K. Baker; Henk Blok; C. Bochna; Ed Brash; Herbert Breuer; Nicholas Chant; Jim Dunne; Tom Eden; Rolf Ent; David Gaskell; Ron Gilman; Kenneth Gustafsson; Wendy Hinton; Garth Huber; Hal Jackson; Mark K. Jones; Cynthia Keppel; P.H. Kim; Wooyoung Kim; Andi Klein; Doug Koltenuk; Meme Liang; George Lolos; Allison Lung; David Mack; D. McKee; David Meekins; Joseph Mitchell; H. Mkrtchian; B. Mueller; Gabriel Niculescu; Ioana Niculescu; D. Pitz; D. Potterveld; Liming Qin; Juerg Reinhold; I.K. Shin; Stepan Stepanyan; V. Tadevosian; L.G. Tang; R.L.J. van der Meer; K. Vansyoc; D. Van Westrum; Bill Vulcan; Stephen Wood; Chen Yan; W.X. Zhao; Beni Zihlmann
2001-01-01
Separated longitudinal and transverse structure functions for the reaction 1H(e,eprime pi+)n were measured in the momentum transfer region Q2=0.6-1.6 (GeV/c)**2 at a value of the invariant mass W=1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parameterization fitted to very low Q2 elastic data
Modal description of longitudinal space-charge fields in pulse-driven free-electron devices
Directory of Open Access Journals (Sweden)
Yu. Lurie
2010-05-01
Full Text Available In pulsed-beam free-electron devices, longitudinal space-charge fields result in collective effects leading to an expansion of short electron bunches along their trajectory. This effect restricts an application of intense ultrashort electron pulses in free-electron radiation sources. A careful theoretical treatment is required in order to achieve an accurate description of the self-fields and the resulted electron beam dynamics. In this paper, longitudinal space-charge fields are considered in the framework of a three-dimensional, space-frequency approach. The model is based on the expansion of the total electromagnetic field (including self-fields in terms of transverse eigenmodes of the (cold cavity, in which the field is excited and propagates. The electromagnetic field, originally obtained in the model as a solution of the wave equation, is shown to satisfy also Gauss’s law. We applied the theory to derive an analytical expression for the longitudinal electric field of a pointlike charge, moving along a waveguide at a constant velocity. This enables consideration and study of the role played by different terms of the resulted expressions, such as components arising from forward and backward waves, propagating waves, and under cutoff frequencies, and so on. Possible simplifications in evaluation of longitudinal space-charge fields are discussed.
Electromagnetic Charge Radius of the Pion at High Precision
Ananthanarayan, B.; Caprini, Irinel; Das, Diganta
2017-09-01
We present a determination of the pion charge radius from high precision data on the pion vector form factor from both timelike and spacelike regions, using a novel formalism based on analyticity and unitarity. At low energies, instead of the poorly known modulus of the form factor, we use its phase, known with high accuracy from Roy equations for π π elastic scattering via the Fermi-Watson theorem. We use also the values of the modulus at several higher timelike energies, where the data from e+e- annihilation and τ decay are mutually consistent, as well as the most recent measurements at spacelike momenta. The experimental uncertainties are implemented by Monte Carlo simulations. The results, which do not rely on a specific parametrization, are optimal for the given input information and do not depend on the unknown phase of the form factor above the first inelastic threshold. Our prediction for the charge radius of the pion is rπ=(0.657 ±0.003 ) fm , which amounts to an increase in precision by a factor of about 2.7 compared to the Particle Data Group average.
Electromagnetic contribution to charge symmetry violation in parton distributions
Directory of Open Access Journals (Sweden)
X.G. Wang
2016-02-01
Full Text Available We report a calculation of the combined effect of photon radiation and quark mass differences on charge symmetry violation (CSV in the parton distribution functions of the nucleon. Following a recent suggestion of Martin and Ryskin, the initial photon distribution is calculated in terms of coherent radiation from the proton as a whole, while the effect of the quark mass difference is based on a recent lattice QCD simulation. The distributions are then evolved to a scale at which they can be compared with experiment by including both QCD and QED radiation. Overall, at a scale of 5 GeV2, the total CSV effect on the phenomenologically important difference between the d and u-quark distributions is some 20% larger than the value based on quark mass differences alone. In total these sources of CSV account for approximately 40% of the NuTeV anomaly.
Charged fluid distribution in higher dimensional spheroidal space-time
Indian Academy of Sciences (India)
A general solution of Einstein field equations corresponding to a charged fluid distribution on the background of higher dimensional spheroidal space-time is obtained. The solution generates several known solutions for superdense star having spheroidal space-time geometry.
Smart reconfigurable parabolic space antenna for variable electromagnetic patterns
Kalra, Sahil; Datta, Rituparna; Munjal, B. S.; Bhattacharya, Bishakh
2018-02-01
An application of reconfigurable parabolic space antenna for satellite is discussed in this paper. The present study focuses on shape morphing of flexible parabolic antenna actuated with Shape Memory Alloy (SMA) wires. The antenna is able to transmit the signals to the desired footprint on earth with a desired gain value. SMA wire based actuation with a locking device is developed for a precise control of Antenna shape. The locking device is efficient to hold the structure in deformed configuration during power cutoff from the system. The maximum controllable deflection at any point using such actuation system is about 25mm with a precision of ±100 m. In order to control the shape of the antenna in a closed feedback loop, a Proportional, Integral and Derivative (PID) based controller is developed using LabVIEW (NI) and experiments are performed. Numerical modeling and analysis of the structure is carried out using finite element software ABAQUS. For data reduction and fast computation, stiffness matrix generated by ABAQUS is condensed by Guyan Reduction technique and shape optimization is performed using Non-dominated Sorting Genetic Algorithm (NSGA-II). The matching in comparative study between numerical and experimental set-up shows efficacy of our method. Thereafter, Electro-Magnetic (EM) simulations of the deformed shape is carried out using electromagnetic field simulation, High Frequency Structure Simulator (HFSS). The proposed design is envisaged to be very effective for multipurpose application of satellite system in the future missions of Indian Space Research Organization (ISRO).
Stochastic Coulomb interactions in space charge limited electron emission
Nijkerk, M.D.; Kruit, P.
2004-01-01
A Monte Carlo simulation tool, which was used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics, was discussed. It was found that interactions in the space charge cloud affect the electron trajectories such that the velocity
Quadrupole transport experiment with space charge dominated cesium ion beam
International Nuclear Information System (INIS)
Faltens, A.; Keefe, D.; Kim, C.; Rosenblum, S.; Tiefenback, M.; Warwick, A.
1984-08-01
The purpose of the experiment is to investigate the beam current transport limit in a long quadrupole-focussed transport channel in the space charge dominated region where the space charge defocussing force is almost as large as the average focussing force of the channel
Klystron - Space-charge limited flow, guns, Perveance
International Nuclear Information System (INIS)
Isagawa, S.
1999-01-01
This paper treats Thermionic emission, Cathode as an e - emitter, Space-charge limited effect and 3/2 power law, Perveance, Beam spread due to space charge, Pierce guns, Magnetically immersed guns, Method of gun design including simulations, and Examples, mainly treating E3786, which attendees will operate above 1 MW-CW in a practical exercise course at KEK. (author). 74 refs
Implementation of Space Charge Forces in BimBim
Gottlob, Emmanuel; Oeftiger, Adrian
An numerical algorithm is described for the implementation of linearised coherent space charge forces into BimBim, an eigenvalue solver for the coherent modes of oscillation of multibunch beams in the presence of beam coupling impedance, beam-beam, transverse feedback and now space charge effects. First results obtained with the model are described and compared to existing results where applicable.
Coupling gravity, electromagnetism and space-time for space propulsion breakthroughs
Millis, Marc G.
1994-01-01
spaceflight would be revolutionized if it were possible to propel a spacecraft without rockets using the coupling between gravity, electromagnetism, and space-time (hence called 'space coupling propulsion'). New theories and observations about the properties of space are emerging which offer new approaches to consider this breakthrough possibility. To guide the search, evaluation, and application of these emerging possibilities, a variety of hypothetical space coupling propulsion mechanisms are presented to highlight the issues that would have to be satisfied to enable such breakthroughs. A brief introduction of the emerging opportunities is also presented.
Space-charge dynamics of polymethylmethacrylate under electron beam irradiation
Gong, H; Ong, C K
1997-01-01
Space-charge dynamics of polymethylmethacrylate (PMMA) under electron beam irradiation has been investigated employing a scanning electron microscope. Assuming a Gaussian space-charge distribution, the distribution range (sigma) has been determined using a time-resolved current method in conjunction with a mirror image method. sigma is found to increase with irradiation time and eventually attain a stationary value. These observations have been discussed by taking into account radiation-induced conductivity and charge mobility. (author)
Guo, Li-xin; Chen, Wei; Li, Jiang-ting; Ren, Yi; Liu, Song-hua
2018-05-01
The dielectric coefficient of a weakly ionised dusty plasma is used to establish a three-dimensional time and space inhomogeneous dusty plasma sheath. The effects of scattering on electromagnetic (EM) waves in this dusty plasma sheath are investigated using the auxiliary differential equation finite-difference time-domain method. Backward radar cross-sectional values of various parameters, including the dust particle radius, charging frequency of dust particles, dust particle concentration, effective collision frequency, rate of the electron density variation with time, angle of EM wave incidence, and plasma frequency, are analysed within the time and space inhomogeneous plasma sheath. The results show the noticeable effects of dusty plasma parameters on EM waves.
Single-Bunch Stability With Direct Space Charge
Oeftiger, Adrian
2017-01-01
Previous studies have shown the suppressing effect of direct space charge on impedance-driven head-tail instabilities. The present work investigates transverse stability for the HL-LHC scenario based on our macro-particle simulation tool PyHEADTAIL using realistic bunch distributions. The impact of selfconsistent modelling is briefly discussed for non-linear space charge forces. We study how space charge pushes the instability threshold for the transverse mode coupling instability (TMCI) occurring between mode 0 and -1. Next we consider finite chromaticity: in absence of space charge, the impedance model predicts head-tail instabilities. For a selected case below TMCI threshold at Q0 = 5, we demonstrate the stabilising effect of space charge. Finally, we compare simulation results to past LHC measurements.
Strange and charge symmetry violating electromagnetic form factors of the nucleon
International Nuclear Information System (INIS)
Shanahan, P.E.
2016-01-01
We summarise recent work based on lattice QCD simulations of the electromagnetic form factors of the octet baryons from the CSSM/QCDSF/UKQCD collaborations. After an analysis of the simulation results using techniques to approach the infinite volume limit and the physical pseudoscalar masses at non-zero momentum transfer, the extrapolated proton and neutron form factors are found to be in excellent agreement with those extracted from experiment. Given the success of these calculations, we describe how the strange electromagnetic form factors may be estimated from these results under the same assumption of charge symmetry used in experimental determinations of those quantities. Motivated by the necessity of that assumption, we explore a method for determining the size of charge symmetry breaking effects using the same lattice results. (author)
DEFF Research Database (Denmark)
Holbøll, Joachim; Bambery, K. R.; Fleming, R. J.
2000-01-01
Electromagnetic theory predicts that a dielectric sample in which a steady DC current of density ε is flowing, and in which the ratio of permittivity ε to conductivity σ varies with position, will acquire a space charge density j·grad(ε/σ). A simple and convenient way to generate an ε/σ gradient...... in a homogeneous sample is to establish a temperature gradient across it. The resulting spatial variation in ε is usually small in polymeric insulators, but the variation in σ can be appreciable. Laser induced pressure pulse (LIPP) measurements were made on 1.5 mm thick plaques of ultra pure LDPE equipped...... with vacuum-evaporated aluminium electrodes. Temperature differences up to 27°C were maintained across the samples, which were subjected to DC fields up to 20 kV/mm. Current density was measured as a function of temperature and field. Negligible thermally generated space charge was observed. The charge...
Electromagnetically-induced nuclear-charge pickup observed in ultra-relativistic Pb collisions
International Nuclear Information System (INIS)
Scheidenberger, C.; Aumann, T.; Pshenichnov, I.A.; Russian Academy of Sciences, Moscow
2002-01-01
A strong increase of inclusive nuclear-charge pickup cross sections, forming 83 Bi from 158 A GeV 82 Pb ions, is observed in comparison to similar measurements at 10.6 A GeV. From the dependence of these cross sections on target atomic number, this increase is attributed to the electromagnetic process of pion production by equivalent photons. The observed cross sections can be reproduced quantitatively using the recently developed RELDIS code. (orig.)
International Nuclear Information System (INIS)
Shukla, P K; Eliasson, B; Kopp, A
2006-01-01
We report on an investigation into the radiation condensation (RC) instability of low-frequency (in comparison with the electron gyrofrequency) compressional electromagnetic waves in a magnetized plasma containing charged dust impurities. By using a two-fluid model, supplemented by the Faraday and Ampere laws, we derive a new dispersion relation. The latter is numerically analysed to examine the role of charged dust grains on the growth rate of the RC instability. The relevance of our investigation to density condensation in the next generation tokamak edges and on solar prominences is discussed
Masongsong, E. V.; Glesener, G. B.; Angelopoulos, V.; Lilensten, J.; Bingley, L.
2015-12-01
The Planeterrella can be used as an analog to help students visualize and understand the electromagnetic processes driving space weather that affect our daily lives. Solar storms and solar wind charged particles (plasma) cause "space weather" via their interaction with Earth's protective magnetic shield, the magnetosphere. The Planeterrella uses magnetized spheres in a vacuum chamber to demonstrate solar wind energy transfer to Earth and planets, with polar localization of aurora due to charged particles traveling along geomagnetic field lines. The Planeterrella provides a unique opportunity to experience and manipulate plasma, the dominant form of matter in our universe, yet seldom observable on Earth. Severe space weather events produce spectacular auroral displays as well as devastating consequences: radiation exposure to air and space travelers, prolonged radio blackouts, and damage to critical GPS and communications satellites. We will (1) discuss ways in which the Planeterrella may be most useful in classroom settings, including large lecture halls, laboratories, and small discussion sessions; (2) provide information on how instructors can produce their own Planeterrella for their courses; and (3) invite meeting attendees to engage in a discussion on how we might be able to improve on the current design of the Planeterrella, and how to reach students in more parts of the world.
Xin, Encheng; Ju, Yong; Yuan, Haiwen
2016-10-20
A space charge density wireless measurement system based on the idea of distributed measurement is proposed for collecting and monitoring the space charge density in an ultra-high-voltage direct-current (UHVDC) environment. The proposed system architecture is composed of a number of wireless nodes connected with space charge density sensors and a base station. The space charge density sensor based on atmospheric ion counter method is elaborated and developed, and the ARM microprocessor and Zigbee radio frequency module are applied. The wireless network communication quality and the relationship between energy consumption and transmission distance in the complicated electromagnetic environment is tested. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the UHVDC transmission lines and can accurately measure the space charge density.
International Space Station-Based Electromagnetic Launcher for Space Science Payloads
Jones, Ross M.
2013-01-01
A method was developed of lowering the cost of planetary exploration missions by using an electromagnetic propulsion/launcher, rather than a chemical-fueled rocket for propulsion. An electromagnetic launcher (EML) based at the International Space Station (ISS) would be used to launch small science payloads to the Moon and near Earth asteroids (NEAs) for the science and exploration missions. An ISS-based electromagnetic launcher could also inject science payloads into orbits around the Earth and perhaps to Mars. The EML would replace rocket technology for certain missions. The EML is a high-energy system that uses electricity rather than propellant to accelerate payloads to high velocities. The most common type of EML is the rail gun. Other types are possible, e.g., a coil gun, also known as a Gauss gun or mass driver. The EML could also "drop" science payloads into the Earth's upper
International Nuclear Information System (INIS)
Rybakov, Yu.P.; Chakrabarti, S.
1981-01-01
Stability by the form of scalar charged solitons with account of electromagnetic field is studied by the Lyapunov method. Conditions of stability for the Sing model are investigated. The model is shown to admit the existence of pointless spherically-symmetric solitons in the absence of the electromagnetic field. Perturbation theory by a non-dimensional parameter is applied for evaluating the effect of electromagnetic field on the stability of pointless solitons [ru
Na, Dong-Yeop; Omelchenko, Yuri A.; Moon, Haksu; Borges, Ben-Hur V.; Teixeira, Fernando L.
2017-10-01
We present a charge-conservative electromagnetic particle-in-cell (EM-PIC) algorithm optimized for the analysis of vacuum electronic devices (VEDs) with cylindrical symmetry (axisymmetry). We exploit the axisymmetry present in the device geometry, fields, and sources to reduce the dimensionality of the problem from 3D to 2D. Further, we employ 'transformation optics' principles to map the original problem in polar coordinates with metric tensor diag (1 ,ρ2 , 1) to an equivalent problem on a Cartesian metric tensor diag (1 , 1 , 1) with an effective (artificial) inhomogeneous medium introduced. The resulting problem in the meridian (ρz) plane is discretized using an unstructured 2D mesh considering TEϕ-polarized fields. Electromagnetic field and source (node-based charges and edge-based currents) variables are expressed as differential forms of various degrees, and discretized using Whitney forms. Using leapfrog time integration, we obtain a mixed E - B finite-element time-domain scheme for the full-discrete Maxwell's equations. We achieve a local and explicit time update for the field equations by employing the sparse approximate inverse (SPAI) algorithm. Interpolating field values to particles' positions for solving Newton-Lorentz equations of motion is also done via Whitney forms. Particles are advanced using the Boris algorithm with relativistic correction. A recently introduced charge-conserving scatter scheme tailored for 2D unstructured grids is used in the scatter step. The algorithm is validated considering cylindrical cavity and space-charge-limited cylindrical diode problems. We use the algorithm to investigate the physical performance of VEDs designed to harness particle bunching effects arising from the coherent (resonance) Cerenkov electron beam interactions within micro-machined slow wave structures.
Space-charge-limit instabilities in electron beams
International Nuclear Information System (INIS)
Coutsias, E.A.; Sullivan, D.J.
1983-01-01
The method of characteristics and multiple-scaling perturbation techniques are used to study the space-charge instability of electron beams. It is found that the stable oscillating state (virtual cathode) created when the space-charge limit is exceeded is similar to a collisionless shock wave. The oscillatory solution originates at the bifurcation point of two unstable steady states. Complementary behavior (virtual anode) results when an ion beam exceeds its space-charge limit. The virtual cathode can also exist in the presence of a neutralizing heavy-ion background. The Pierce instability, where the electron and ion charge densities are equal, is a special case of this broader class. Estimates of the nonlinear growth rate of the instability at the space-charge limit are given
Dynamic space charge behaviour in polymeric DC cables
DEFF Research Database (Denmark)
Rasmussen, Claus Nygaard; Holbøll, Joachim; Henriksen, Mogens
2002-01-01
The use of extruded insulation for DC cables involves a risk of local electric field enhancement, caused by a space charge build-up within the dielectric. In this work, the theory of charge generation and transport in polymers is applied in a numerical computer model in order to predict...... the formation and transport of space charges in a polymeric dielectric. The model incorporates the processes of field assisted electron-hole pair generation from impurity atoms, trapping and charge injection at the electrodes. Its aim has been to study the field- and temperature dependent dynamic behaviour...
Conductivity and Space Charges in PE with Additives
DEFF Research Database (Denmark)
Holbøll, Joachim; Henriksen, Mogens; Hjerrild, J.
2003-01-01
temperatures. Space charge formation under an applied electrical field of 20 kV/mm was investigated by means of the pulse-electro-acoustic method (PEA) at room temperature. The results were compared to space charge formation and conductivity in common LDPE. The measurements showed considerable differences...... between materials and only minor influence of crosslinking process and the addition of antioxidant with respect to the electrical properties of the material. Possible correlations between conductivity and space charge formation are discussed in the paper. The relevance of the findings for application...
Study of space--charge effect by computer
International Nuclear Information System (INIS)
Sasaki, T.
1982-01-01
The space--charge effect in high density electron beams (beam current approx.2 μA) focused by a uniform magnetic field is studied computationally. On an approximation of averaged space-- charge force, a theory of trajectory displacements of beam electrons is developed. The theory shows that the effect of the averaged space--charge force appears as a focal length stretch. The theory is confirmed not only qualitatively but also quantitatively by simulations. Empirical formulas for the trajectory displacement and the energy spread are presented. A comparison between the empirical formulas and some theoretical formulas is made, leading to a severe criticism on the theories of energy spreads
Space-charge compensation of highly charged ion beam from laser ion source
International Nuclear Information System (INIS)
Kondrashev, S.A.; Collier, J.; Sherwood, T.R.
1996-01-01
The problem of matching an ion beam delivered by a high-intensity ion source with an accelerator is considered. The experimental results of highly charged ion beam transport with space-charge compensation by electrons are presented. A tungsten thermionic cathode is used as a source of electrons for beam compensation. An increase of ion beam current density by a factor of 25 is obtained as a result of space-charge compensation at a distance of 3 m from the extraction system. The process of ion beam space-charge compensation, requirements for a source of electrons, and the influence of recombination losses in a space-charge-compensated ion beam are discussed. (author)
Effect of ion compensation of the beam space charge on gyrotron operation
Energy Technology Data Exchange (ETDEWEB)
Fokin, A. P.; Glyavin, M. Yu. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Nusinovich, G. S. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)
2015-04-15
In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.
Motion of a point charge in electromagnetic fields under consideration of radiation damping
International Nuclear Information System (INIS)
Stoeckel, H.
1976-01-01
The 'new equation' of Mo and Papas for the description of a point charge in an electromagnetic field under consideration of radiation damping, published in 1971, doesn't show the known disadvantages of the Lorentz-Dirac equation, taken as a basis up to now. Different forms of the Mo-Papas equation are derived and the resulting force- and power-balances are discussed. Exact and approximated solutions are derived for simple given fields, for instance for a homogeneous magnetic field, a homogeneous electric field and for the field of a resting point charge. The scattering angles are calculated for the scattering of a point charge by a homogeneous magnetic resp. electric field of finite extension. The results agree well with approximation formulas of other authors. (author)
One-carrier free space charge motion under applied voltage
Energy Technology Data Exchange (ETDEWEB)
de ALMEIDA, L E.C.; FERREIRA, G F.L. [SAO PAULO UNIV., SAO CARLOS (BRAZIL). INSTITUTO DE FISICA E QUIMICA
1975-12-01
It is shown how to transform the system of partial differential equations, describing the free one-carrier space charge motion in solid dielectrics under a given applied voltage and while the charge distribution touches only one of the electrodes, into a first order ordinary differential equation from whose solution all the interesting quantities may be easily derived. It was found that some charge distributions can display current reversal.
The electromagnetic multipole moments of the charged open-flavor {Z}_{\\bar{c}q} states
Azizi, K.; Özdem, U.
2018-05-01
The electromagnetic multipole moments of the open-flavor {Z}\\bar{cq} states are investigated by assuming a diquark–antidiquark picture for their internal structure and quantum numbers {J}{PC}={1}+- for their spin-parity. In particular, their magnetic and quadrupole moments are extracted in the framework of light-cone QCD sum rule by the help of the photon distribution amplitudes. The electromagnetic multipole moments of the open-flavor {Z}\\bar{cq} states are important dynamical observables, which encode valuable information on their underlying structure. The results obtained for the magnetic moments of different structures are considerably large and can be measured in future experiments. We obtain very small values for the quadrupole moments of {Z}\\bar{cq} states indicating a nonspherical charge distribution.
Space Charge Effect in the Sheet and Solid Electron Beam
Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung
1998-11-01
We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.
Nonlinear periodic space-charge waves in plasma
International Nuclear Information System (INIS)
Kovalev, V. A.
2009-01-01
A solution is obtained in the form of coupled nonlinear periodic space-charge waves propagating in a magnetoactive plasma. The wave spectrum in the vicinity of the critical point, where the number of harmonics increases substantially, is found to fall with harmonic number as ∝ s -1/3 . Periodic space-charge waves are invoked to explain the zebra pattern in the radio emission from solar flares.
Study of static properties of magnetron-type space charges
International Nuclear Information System (INIS)
Delcroix, Jean-Loup
1953-01-01
This research thesis reports an in-depth analysis of physical properties of static regimes to address the issue of space charges. This theoretical study of the Hull magnetron is followed by the description of experiments on the Hull magnetron which highlight transitions between the different regimes. Then, another theoretical approach aims at generalising the magnetron theory, based on other types of magnetron theory (general equations of magnetron-type space charges, inverted Hull magnetron theory, circular field magnetron theory)
Space-Charge Effects in a Gas Detector
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D.D.
2010-12-03
Discussion of space-charge effects in a photoluminescence cell that will be used as a nondisruptive total energy monitor at the LCLS facility is presented. Regimes where primary photoelectrons will be confined within the X-ray beam aperture are identified. Effects of the space-charge on the further evolution of the electron and ion populations are discussed. Parameters of the afterglow plasma are evaluated. Conditions under which the detector output will be proportional to the pulse energy are defined.
Charge symmetry violation in the electromagnetic form factors of the proton
International Nuclear Information System (INIS)
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M.; Pleiter, D.; Stueben, H.
2015-03-01
Experimental tests of QCD through its predictions for the strange-quark content of the proton have been drastically restricted by our lack of knowledge of the violation of charge symmetry (CSV). We find unexpectedly tiny CSV in the proton's electromagnetic form factors by performing the first extraction of these quantities based on an analysis of lattice QCD data. The resulting values are an order of magnitude smaller than current bounds on proton strangeness from parity violating electron-proton scattering experiments. This result paves the way for a new generation of experimental measurements of the proton's strange form factors to challenge the predictions of QCD.
Space charge studies in the PS
Asvesta, F; Damerau, H; Huschauer, A; Papaphilippou, Y; Serluca, M; Sterbini, G; Zisopoulos, P
2017-01-01
In this paper the results of Machine Development (MD)studies conducted at the CERN Proton Sychrotron (PS) arepresented. The main focus was the investigation of newworking points in an effort to characterize and potentiallyimprove the brightness for LHC-type beams in view of theLHC Injectors Upgrade (LIU). Various working points werecompared in terms of losses and emittance evolution. Sincespace charge and the resonances it excites are the main causefor emittance blow-up and losses, tunes close to excitedresonances were carefully studied. Mitigation techniques,such as bunch flattening using a double harmonic RF system,were also tested.
Electromagnetic-field equations in the six-dimensional space-time R6
International Nuclear Information System (INIS)
Teli, M.T.; Palaskar, D.
1984-01-01
Maxwell's equations (without monopoles) for electromagnetic fields are obtained in six-dimensional space-time. The equations possess structural symmetry in space and time, field and source densities. Space-time-symmetric conservation laws and field solutions are obtained. The results are successfully correlated with their four-dimensional space-time counterparts
Electromagnetic Weible Instability in Intense Charged Particle Beams with Large Energy Anisotropy
International Nuclear Information System (INIS)
Startsev, Edward A.; Davidson, Ronald C.
2003-01-01
In plasmas with strongly anisotropic distribution functions, collective instabilities may develop if there is sufficient coupling between the transverse and longitudinal degrees of freedom. Our previous numerical and theoretical studies of intense charged particle beams with large temperature anisotropy [E. A. Startsev, R. C. Davidson and H. Qin, PRSTAB, 6, 084401 (2003); Phys. Plasmas 9, 3138 (2002)] demonstrated that a fast, electrostatic, Harris-like instability develops, and saturates nonlinearly, for sufficiently large temperature anisotropy (T perpendi c ular b /T parallelb >> 1). The total distribution function after saturation, however, is still far from equipartitioned. In this paper the linearized Vlasov-Maxwell equations are used to investigate detailed properties of the transverse electromagnetic Weibel-type instability for a long charge bunch propagating through a cylindrical pipe of radius r w . The kinetic stability analysis is carried out for azimuthally symmetric perturbations about a two-temperature thermal equilibrium distribution in the smooth-focusing approximation. The most unstable modes are identified, and their eigenfrequencies, radial mode structure and instability thresholds are determined. The stability analysis shows that, although there is free energy available to drive the electromagnetic Weibel instability, the finite transverse geometry of the charged particle beam introduces a large threshold value for the temperature anisotropy ((T perpendi c ularb /T parallelb ) Weibel >> (T perpendi c ularb /T parallelb ) Harris ) below which the instability is absent. Hence, unlike the case of an electrically neutral plasma, the Weibel instability is not expected to play as significant a role in the process of energy isotropization of intense unneutralized charged particle beams as the electrostatic Harris-type instability
A Wigner quasi-distribution function for charged particles in classical electromagnetic fields
International Nuclear Information System (INIS)
Levanda, M.; Fleurov, V.
2001-01-01
A gauge-invariant Wigner quasi-distribution function for charged particles in classical electromagnetic fields is derived in a rigorous way. Its relation to the axial gauge is discussed, as well as the relation between the kinetic and canonical momenta in the Wigner representation. Gauge-invariant quantum analogs of Hamilton-Jacobi and Boltzmann kinetic equations are formulated for arbitrary classical electromagnetic fields in terms of the 'slashed' derivatives and momenta, introduced for this purpose. The kinetic meaning of these slashed quantities is discussed. We introduce gauge-invariant conditional moments and use them to derive a kinetic momentum continuity equation. This equation provides us with a hydrodynamic representation for quantum transport processes and a definition of the 'collision force'. The hydrodynamic equation is applied for the rotation part of the electron motion. The theory is illustrated by its application in three examples: Wigner quasi-distribution function and equations for an electron in a magnetic field and harmonic potential; Wigner quasi-distribution function for a charged particle in periodic systems using the kq representation; two Wigner quasi-distribution functions for heavy-mass polaron in an electric field
International Nuclear Information System (INIS)
Braginsky, V.B.; Kardashev, N.S.; Polnarev, A.G.; Novikov, I.D.
1989-12-01
Propagation of an electromagnetic wave in the field of gravitational waves is considered. Attention is given to the principal difference between the electromagnetic wave propagation in the field of random gravitational waves and the electromagnetic wave propagation in a medium with a randomly-inhomogeneous refraction index. It is shown that in the case of the gravitation wave field the phase shift of an electromagnetic wave does not increase with distance. The capability of space radio interferometry to detect relic gravitational waves as well as gravitational wave bursts of non cosmological origin are analyzed. (author). 64 refs, 2 figs
International Nuclear Information System (INIS)
Konstantinovich, A.V.; Melnychuk, S.V.; Konstantinovich, I.A.
2002-01-01
The integral expressions for spectral-angular and spectral distributions of the radiation power of heterogeneous charged particles system moving on arbitrary trajectory in nonabsorbable isotropic media media with ε≠1 , μ≠1 are obtained using the Lorentz's self-interaction method. In this method a proper electromagnetic field, acting on electron, is defined as a semi difference between retarded and advanced potentials (Dirac, 1938). The power spectrum of Cherenkov radiation for the linear uniformly moving heterogeneous system of charged particles are obtained. It is found that the expression for the radiation power of heterogeneous system of charged particles becomes simplified when a system of charged particles is homogeneous. In this case the radiation power includes the coherent factor. It is shown what the redistribution effects in energy of the radiation spectrum of the studied system are caused by the coherent factor. The radiation spectrum of the system of electrons moving in a circle in this medium is discrete. The Doppler effect causes the appearance of the new harmonics for the system of electrons moving in a spiral. These harmonics form the region of continuous radiation spectrum. (authors)
Charge collection and space charge distribution in neutron-irradiated epitaxial silicon detectors
Energy Technology Data Exchange (ETDEWEB)
Poehlsen, Thomas
2010-04-15
In this work epitaxial n-type silicon diodes with a thickness of 100 {mu}m and 150 {mu}m are investigated. After neutron irradiation with fluences between 10{sup 14} cm{sup -2} and 4 x 10{sup 15} cm{sup -2} annealing studies were performed. CV-IV curves were taken and the depletion voltage was determined for different annealing times. All investigated diodes with neutron fluences greater than 2 x 10{sup 14} cm{sup -2} showed type inversion due to irradiation. Measurements with the transient current technique (TCT) using a pulsed laser were performed to investigate charge collection effects for temperatures of -40 C, -10 C and 20 C. The charge correction method was used to determine the effective trapping time {tau}{sub eff}. Inconsistencies of the results could be explained by assuming field dependent trapping times. A simulation of charge collection could be used to determine the field dependent trapping time {tau}{sub eff}(E) and the space charge distribution in the detector bulk. Assuming a linear field dependence of the trapping times and a linear space charge distribution the data could be described. Indications of charge multiplication were seen in the irradiated 100 {mu}m thick diodes for all investigated fluences at voltages above 800 V. The space charge distribution extracted from TCT measurements was compared to the results of the CV measurements and showed good agreement. (orig.)
Charge collection and space charge distribution in neutron-irradiated epitaxial silicon detectors
International Nuclear Information System (INIS)
Poehlsen, Thomas
2010-04-01
In this work epitaxial n-type silicon diodes with a thickness of 100 μm and 150 μm are investigated. After neutron irradiation with fluences between 10 14 cm -2 and 4 x 10 15 cm -2 annealing studies were performed. CV-IV curves were taken and the depletion voltage was determined for different annealing times. All investigated diodes with neutron fluences greater than 2 x 10 14 cm -2 showed type inversion due to irradiation. Measurements with the transient current technique (TCT) using a pulsed laser were performed to investigate charge collection effects for temperatures of -40 C, -10 C and 20 C. The charge correction method was used to determine the effective trapping time τ eff . Inconsistencies of the results could be explained by assuming field dependent trapping times. A simulation of charge collection could be used to determine the field dependent trapping time τ eff (E) and the space charge distribution in the detector bulk. Assuming a linear field dependence of the trapping times and a linear space charge distribution the data could be described. Indications of charge multiplication were seen in the irradiated 100 μm thick diodes for all investigated fluences at voltages above 800 V. The space charge distribution extracted from TCT measurements was compared to the results of the CV measurements and showed good agreement. (orig.)
Space charge-limited emission studies using Coulomb's Law
Carr, Christopher G.
2004-01-01
Approved for Public Release; Distribution is Unlimited Child and Langmuir introduced a solution to space charge limited emission in an infinite area planar diode. The solution follows from starting with Poisson's equation, and requires solving a non-linear differential equation. This approach can also be applied to cylindrical and spherical geometries, but only for one-dimensional cases. By approaching the problem from Coulomb's law and applying the effect of an assumed charge distribution...
Quantum theory of space charge limited current in solids
Energy Technology Data Exchange (ETDEWEB)
González, Gabriel, E-mail: gabriel.gonzalez@uaslp.mx [Cátedras Conacyt, Universidad Autónoma de San Luis Potosí, San Luis Potosí 78000, Mexico and Coordinación para la Innovación y la Aplicación de la Ciencia y la Tecnología, Universidad Autónoma de San Luis Potosí, San Luis Potosí 78000 (Mexico)
2015-02-28
We present a quantum model of space charge limited current transport inside trap-free solids with planar geometry in the mean field approximation. We use a simple transformation which allows us to find the exact analytical solution for the steady state current case. We use our approach to find a Mott-Gurney like behavior and the mobility for single charge carriers in the quantum regime in solids.
Stochastic Coulomb interactions in space charge limited electron emission
International Nuclear Information System (INIS)
Nijkerk, M.D.; Kruit, P.
2004-01-01
Emission models that form the basis of self-consistent field computations make use of the approximation that emitted electrons form a smooth space charge jelly. In reality, electrons are discrete particles that are subject to statistical Coulomb interactions. A Monte Carlo simulation tool is used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics. We find that interactions in the space charge cloud affect the electron trajectories such that the velocity distribution is Maxwellian, regardless of the current density. Interactions near the emitter effectively conserve the Maxwellian distribution. The surprising result is that the width of the distribution of transversal velocities does not change. The distribution of longitudinal velocities does broaden, as expected from existing theories
Space-Charge Experiments at the CERN Proton Synchrotron
Franchetti, Giuliano; Hofmann, I; Martini, M; Métral, E; Qiang, J; Ryne, D; Steerenberg, R; CFA Beam Dynamics Workshop “High Intensity and Brightness Hadron Beams”
2005-01-01
Benchmarking of the simulation codes used for the design of the next generation of high beam power accelerators is of paramount importance due to the very demanding requirements on the level of beam losses. This is usually accomplished by comparing simulation results against available theories, and more importantly, against experimental observations. To this aim, a number of well-defined test cases, obtained by accurate measurements made in existing machines, are of great interest. Such measurements have been made in the CERN Proton Synchrotron to probe three space-charge effects: (i) transverse emittance blow-up due to space-charge induced crossing of the integer or half-integer stop-band, (ii) space-charge and octupole driven resonance trapping, and (iii) intensity-dependent emittance transfer between the two transverse planes. The last mechanism is discussed in detail in this paper and compared to simulation predictions.
Space-charge effects in Penning ion traps
Porobić, T.; Beck, M.; Breitenfeldt, M.; Couratin, C.; Finlay, P.; Knecht, A.; Fabian, X.; Friedag, P.; Fléchard, X.; Liénard, E.; Ban, G.; Zákoucký, D.; Soti, G.; Van Gorp, S.; Weinheimer, Ch.; Wursten, E.; Severijns, N.
2015-06-01
The influence of space-charge on ion cyclotron resonances and magnetron eigenfrequency in a gas-filled Penning ion trap has been investigated. Off-line measurements with K39+ using the cooling trap of the WITCH retardation spectrometer-based setup at ISOLDE/CERN were performed. Experimental ion cyclotron resonances were compared with ab initio Coulomb simulations and found to be in agreement. As an important systematic effect of the WITCH experiment, the magnetron eigenfrequency of the ion cloud was studied under increasing space-charge conditions. Finally, the helium buffer gas pressure in the Penning trap was determined by comparing experimental cooling rates with simulations.
A modified space charge routine for high intensity bunched beams
International Nuclear Information System (INIS)
Lapostolle, P.; Lombardi, A.M.; Tanke, E.; Valero, S.; Garnett, R.W.; Wangler, T.P.
1996-01-01
A new routine and a computer code (DYNAC) for the calculation of space charge densities in a new generation of linear accelerators for various industrial applications is presented. The new beam dynamics method used in this code, employs a set of quasi-Liouvillian equations, allowing beam dynamics computations in long and complex structures for electrons, as well as protons and ions. With this new beam dynamics method, the coordinates of particles are known at any position in the accelerating elements, allowing multistep space charge calculations. (K.A.)
Three-dimensional space-charge calculation method
International Nuclear Information System (INIS)
Lysenko, W.P.; Wadlinger, E.A.
1980-09-01
A method is presented for calculating space-charge forces on individual particles in a particle tracing simulation code. Poisson's equation is solved in three dimensions with boundary conditions specified on an arbitrary surface. When the boundary condition is defined by an impressed radio-frequency field, the external electric fields as well as the space-charge fields are determined. A least squares fitting procedure is used to calculate the coefficients of expansion functions, which need not be orthogonal nor individually satisfy the boundary condition
High-energy charged particle bursts in the near-Earth space as earthquake precursors
Directory of Open Access Journals (Sweden)
S. Yu. Aleksandrin
2003-02-01
Full Text Available The experimental data on high-energy charged particle fluxes, obtained in various near-Earth space experiments (MIR orbital station, METEOR-3, GAMMA and SAMPEX satellites were processed and analyzed with the goal to search for particle bursts. Particle bursts have been selected in every experiment considered. It was shown that the significant part of high-energy charged particle bursts correlates with seismic activity. Moreover, the particle bursts are observed several hours before strong earthquakes; L-shells of particle bursts and corresponding earthquakes are practically the same. Some features of a seismo-magnetosphere connection model, based on the interaction of electromagnetic emission of seismic origin and radiation belt particles, were considered. Key words. Ionospheric physics (energetic particles, trapped; energetic particles, precipitating; magnetosphere-ionosphere interactions
Resonance behavior in the presence of space charge
International Nuclear Information System (INIS)
Month, M.; Weng, W.T.
1983-01-01
An analysis is presented of the resonance behavior of particle beams in the presence of space charge fields. Since self-consistent requirements are ignored, the results describe onset or early behavior. It is shown that in a beam of uniform current resonances excited by magnetic field errors are stabilized by the detuning effect of the self-field space charge force. This situation is changed when a radiofrequency accelerating field is applied. As beam bunching results after rf turn-on, the space charge force becomes modulated along the bunches, vanishing at the ends. At these regions of small or vanishing space charge, stabilization from non-linear detuning tends to disappear, thus leaving particles susceptible to resonance blow-up. This picture of the effect of beam bunching can be studied by considering the phase space structure for particles at different positions along the bunches. A somewhat unusual conclusion is made on the use of this analysis to model beam capture in a synchrotron at low energy
Simulation of space charge effects in a synchrotron
International Nuclear Information System (INIS)
Machida, Shinji; Ikegami, Masanori
1998-01-01
We have studied space charge effects in a synchrotron with multi-particle tracking in 2-D and 3-D configuration space (4-D and 6-D phase space, respectively). First, we will describe the modelling of space charge fields in the simulation and a procedure of tracking. Several ways of presenting tracking results will be also mentioned. Secondly, it is discussed as a demonstration of the simulation study that coherent modes of a beam play a major role in beam stability and intensity limit. The incoherent tune in a resonance condition should be replaced by the coherent tune. Finally, we consider the coherent motion of a beam core as a driving force of halo formation. The mechanism is familiar in linac, and we apply it in a synchrotron
Space charge limited avalanche growth in multigap resistive plate chambers
International Nuclear Information System (INIS)
Akindinov, A.N.; Kaidalov, A.B.; Kisselev, S.M.; Alici, A.; Basile, M.; Cifarelli, L.; Anselmo, F.; Antonioli, P.; Romeo, G. Cara; Cindolo, F.; Baek, Y.; Kim, D.H.; Cosenza, F.; Caro, A. De; Pasquale, S. De; Bartolomeo, A. Di; Girard, M. Fusco; Guida, M.; Hatzifotiadou, D.; Kim, D.W.; Laurenti, G.; Lee, K.; Lee, S.C.; Lioublev, E.; Luvisetto, M.L.; Margotti, A.; Martemiyanov, A.N.; Nania, R.; Noferini, F.; Otiougova, P.; Pierella, F.; Polozov, P.A.; Scapparone, E.; Scioli, G.; Sellitto, S.B.; Smirnitski, A.V.; Tchoumakov, M.M.; Valenti, G.; Vicinanza, D.; Voloshin, K.G.; Williams, M.C.S.; Zagreev, B.V.; Zampolli, C.; Zichichi, A.
2004-01-01
Abstract The ALICE TOF array will be built using the Multigap Resistive Plate Chamber(MRPC) configured as a double stack. Each stack contains 5 gas gaps with width of 250 μm. There has been an intense R and D effort to optimise this new detector to withstand the problems connected with the high level of radiation at the LHC. One clear outcome of the R and D is that the growth of the gas avalanche is strongly affected by space charge. The effect of the space charge is a decrease in the rate of change in gain with electric field; this allows more stable operation of this detector. We have measured the gain as a function of the electric field and also measured the ratio of the fast charge to the total charge produced in the gas gap. It is well established that RPCs built with 250 μm gas gap have a much superior performance than 2 mm gaps; we discuss and compare the performance of 250 μm gap MRPCs with 2 mm gap RPCs to show the importance of space-charge limitation of avalanche growth. (orig.)
Artemyev, A V; Neishtadt, A I; Zelenyi, L M; Vainchtein, D L
2010-12-01
We present an analytical and numerical study of the surfatron acceleration of nonrelativistic charged particles by electromagnetic waves. The acceleration is caused by capture of particles into resonance with one of the waves. We investigate capture for systems with one or two waves and provide conditions under which the obtained results can be applied to systems with more than two waves. In the case of a single wave, the once captured particles never leave the resonance and their velocity grows linearly with time. However, if there are two waves in the system, the upper bound of the energy gain may exist and we find the analytical value of that bound. We discuss several generalizations including the relativistic limit, different wave amplitudes, and a wide range of the waves' wavenumbers. The obtained results are used for qualitative description of some phenomena observed in the Earth's magnetosphere. © 2010 American Institute of Physics.
Space charge effects in a bending magnet system
International Nuclear Information System (INIS)
Lee, E.P.; Close, E.; Smith, L.
1987-03-01
In order to examine problems and phenomena associated with space charge in a beam bending system, the beam dynamics code HICURB has been written. Its principal features include momentum variations, vertical and horizontal envelope dynamics coupled to the off-axis centroid, curvature effect on fields, and images. Preliminary results for an achromatic lattice configuration are presented
Current distribution in triodes neglecting space charge and initial velocities
Hamaker, H.C.
1950-01-01
A theory of the current distribution in triodes with positive grid is developed on the assumption that space charge and the initial velocities of both primary and secondary electrons may be neglected. This theory, which is originally due to De Lussanct de la Sablonière, has been put in a more lucid
Space charge limited conduction in CdSe thin films
Indian Academy of Sciences (India)
Unknown
of trap limited space charge limited conduction (SCLC) at higher voltage. The transition voltage (Vt ) from ohmic to SCLC is found to be quite independent of ambient temperature as well as intensity of illumination. SCLC is explained on the basis of the exponential trap distribution in CdSe films. Trap depths estimated from.
Numerical investigation of space charge electric field for a sheet ...
Indian Academy of Sciences (India)
One of the problems in scaling high power vacuum and plasma microwave sources to higher frequencies is the need to transport beams with higher space charge density, since the radio frequency circuit transverse dimensions tend to decrease with wavelength. The use of sheet electron beams can alleviate this difficulty ...
Low-energy beam transport using space-charge lenses
International Nuclear Information System (INIS)
Meusel, O.; Bechtold, A.; Pozimski, J.; Ratzinger, U.; Schempp, A.; Klein, H.
2005-01-01
Space-charge lenses (SCL) of the Gabor type provide strong cylinder symmetric focusing for low-energy ion beams using a confined nonneutral plasma. They need modest magnetic and electrostatic field strength and provide a short installation length when compared to conventional LEBT-lenses like quadrupoles and magnetic solenoids. The density distribution of the enclosed space charge within the Gabor lens is given by the confinement in transverse and longitudinal directions. In the case of a positive ion beam, the space charge of the confined electron cloud may cause an overcompensation of the ion beam space-charge force and consequently focuses the beam. To investigate the capabilities of an SCL double-lens system for ion beam into an RFQ, a test injector was installed at IAP and put into operation successfully. Furthermore, to study the focusing capabilities of this lens at beam energies up to 500 keV, a high-field Gabor lens was built and installed downstream of the RFQ. Experimental results of the beam injection into the RFQ are presented as well as those of these first bunched beam-focusing tests with the 110 A keV He + beam
Space charge effects in a bending magnet system
International Nuclear Information System (INIS)
Lee, E.P.; Close, E.; Smith, L.
1987-01-01
In order to examine problems and phenomena associated with space charge in a beam bending system, the beam dynamics code HICURB has been written. Its principal features include momentum variations, vertical and horizontal envelope dynamics coupled to the off-axis centroid, curvature effect on fields, and images. Preliminary results for an achromatic lattice configuration are presented
Spectral investigation of a complex space charge structure in plasma
International Nuclear Information System (INIS)
Gurlui, S.; Dimitriu, D. G.; Ionita, C.; Schrittwieser, R. W.
2009-01-01
Complex space charge structures bordered by electrical double layers were spectrally investigated in argon plasma in the domain 400-1000 nm, identifying the lines corresponding to the transitions from different excited states of argon. The electron excitation temperature in the argon atoms was estimated from the spectral lines intensity ratio. (authors)
Space-Charge-Limited Emission Models for Particle Simulation
Verboncoeur, J. P.; Cartwright, K. L.; Murphy, T.
2004-11-01
Space-charge-limited (SCL) emission of electrons from various materials is a common method of generating the high current beams required to drive high power microwave (HPM) sources. In the SCL emission process, sufficient space charge is extracted from a surface, often of complicated geometry, to drive the electric field normal to the surface close to zero. The emitted current is highly dominated by space charge effects as well as ambient fields near the surface. In this work, we consider computational models for the macroscopic SCL emission process including application of Gauss's law and the Child-Langmuir law for space-charge-limited emission. Models are described for ideal conductors, lossy conductors, and dielectrics. Also considered is the discretization of these models, and the implications for the emission physics. Previous work on primary and dual-cell emission models [Watrous et al., Phys. Plasmas 8, 289-296 (2001)] is reexamined, and aspects of the performance, including fidelity and noise properties, are improved. Models for one-dimensional diodes are considered, as well as multidimensional emitting surfaces, which include corners and transverse fields.
One-carrier free space charge motion under applied voltage
International Nuclear Information System (INIS)
Camargo, P.C.; Ferreira, G.F.L.
1976-01-01
The system of partial differential equations describing the one-carrier free space-charge motion under a given applied voltage is transformed into a system of two ordinary differential equations. The method is applied to find the external current injection [pt
Quantum electrodynamics with arbitrary charge on a noncommutative space
International Nuclear Information System (INIS)
Zhou Wanping; Long Zhengwen; Cai Shaohong
2009-01-01
Using the Seiberg-Witten map, we obtain a quantum electrodynamics on a noncommutative space, which has arbitrary charge and keep the gauge invariance to at the leading order in theta. The one-loop divergence and Compton scattering are reinvestigated. The noncommutative effects are larger than those in ordinary noncommutative quantum electrodynamics. (authors)
Energy Technology Data Exchange (ETDEWEB)
Rudolph, E [Max-Planck-Institut fuer Physik und Astrophysik, Muenchen (F.R. Germany)
1975-01-01
As a model for gravitational radiation damping of a planet the electromagnetic radiation damping of an extended charged body moving in an external gravitational field is calculated in harmonic coordinates using a weak field, slowing-motion approximation. Special attention is paid to the case where this gravitational field is a weak Schwarzschild field. Using Green's function methods for this purpose it is shown that in a slow-motion approximation there is a strange connection between the tail part and the sharp part: radiation reaction terms of the tail part can cancel corresponding terms of the sharp part. Due to this cancelling mechanism the lowest order electromagnetic radiation damping force in an external gravitational field in harmonic coordinates remains the flat space Abraham Lorentz force. It is demonstrated in this simplified model that a naive slow-motion approximation may easily lead to divergent higher order terms. It is shown that this difficulty does not arise up to the considered order.
KOBRA 3 - a code for the calculation of space-charge-influenced trajectories in 3-dimensions
International Nuclear Information System (INIS)
Spaedtke, P.; Wipf, S.
1989-06-01
KOBRA3 is a three-dimensional multi-purpose program, written in standard FORTRAN77. The main purpose of the program is to calculate the trajectories of charged particles through a static electro-magnetic field in three dimensions. If space charge is not negligible its influence is taken into account by an iterative process. The Laplace equation is solved for the scalar potential. During the ray tracing, in which the equations of motion for charged particles are solved, the space charge term in the Poisson equation is distributed onto the mesh. By repeating this procedure the steady-state Vlasov equation is solved: ∇ 2 φ+∫∫∫f p dxdydz = 0, where φ is the electro-static potential and f p (r vector, v vector) describes the distribution of the charged particles in space. KOBRA3 can handle finite plasma boundaries, which are found by the program automatically. Special features are included within the program to investigate the beam quality (emittance, transverse energy), and to display the geometry, the trajectories and the potential and magnetic fields graphically. The modular structure of the program enables the user to create his (her) own diagnostic programs or interfaces to the main program. This report is intended to facilitate the use of KOBRA3 by describing the theory, structure and numerical methods used. At GSI (Gesellschaft fuer Schwerionenforschung) the program runs on an IBM 3090-40E. The program has been installed on other machines e.g. CRAY XM-P, CRAY II, VAX 8600, IBM 3090-200, IBM 3033, ATARI ST, IBM-AT. (orig./HSI)
Electromagnetic Emissions During Rock-fracturing Experiments Inside Magnetic Field Free Space
Wang, H.; Zhou, J.; Zhu, T.; Jin, H.
2012-12-01
Abnormal electromagnetic emission (EME) signal is one type of the most important precursors before earthquake, which has been widely observed and recorded before large earthquake, but the physical mechanism underlying the phenomenon is unclear and under controversy. Monitoring the EME signals during rock-fracturing experiments in laboratory is an effective way to study the phenomena and their underlying mechanism. Electromagnetic noise is everywhere because industrial and civilian electrical equipments have been widely used, which make difficulties to the in-lab experiments and field monitoring. To avoid the interference from electromagnetic noise, electromagnetic experiments must be carried out inside shielded space. Magnetic Field Free Space (MFFS) was constructed by Institute of Geophysics, China Earthquake Administration in 1980s. MFFS is a near-spherical polyhedron 'space' with 26 faces and inside diameter about 2.3 m. It is enclosed by 8-layer permalloy 1J85 for shielding magnetic field and 2-layer purified aluminium for shielding electric field. MFFS mainly shields static magnetic field by a factor of 160-4000 for the magnetic signals with the frequencies ranging from 0.01 Hz to 10 Hz. The intensity of magnetic field inside the space is less than 20 nT and its fluctuation is less than 0.3 nT in 90 hours. MFFS can dramatically shield EME signals in the frequency range of EME antennas utilized in our experiments, (several to ~320) kHz, by at least 90%, based on observation. Rock specimens (granite, marble) were fractured by two ways inside MFFS. 1) Cuboid bulk specimens were drilled, filled with static cracking agent, and then dilated from inside until fracture. 2) Cylindrical rock specimens were stressed until fracture by using a non-magnetic rock testing machine with the maximum testing force 300kN. EME, acoustic emission (AE) and strain signals were collected synchronously by the same data acquisitor, Acoustic Emission Workstation made by Physical Acoustics
Determination of charged particle beam parameters with taking into account of space charge
International Nuclear Information System (INIS)
Ishkhanov, B.S.; Poseryaev, A.V.; Shvedunov, V.I.
2005-01-01
One describes a procedure to determine the basic parameters of a paraxial axially-symmetric beam of charged particles taking account of space charge contribution. The described procedure is based on application of the general equation for beam envelope. Paper presents data on its convergence and resistance to measurement errors. The position determination error of crossover (stretching) and radius of beam in crossover is maximum 15% , while the emittance determination error depends on emittance and space charge correlation. The introduced procedure was used to determine parameters of the available electron gun 20 keV energy beam with 0.64 A current. The derived results turned to agree closely with the design parameters [ru
Reduction of space charge breakdown in e-beam irradiated nano/polymethyl methacrylate composites
International Nuclear Information System (INIS)
Zheng Feihu; Zhang Yewen; An Zhenlian; Dong Jianxing; Lei Qingquan
2013-01-01
Fast discharge of numerous space charges in dielectric materials can cause space charge breakdown. This letter reports the role of nanoparticles in affecting space charge breakdown of nano/polymethyl methacrylate composites. Space charge distributions in the composites, implanted by electron beam irradiation, were measured by pressure wave propagation method. The results show that the nanoparticles have significant effects on the isothermal charge decay and space charge breakdown in the nanocomposites. The resistance to space charge breakdown in the nanocomposites is attributed to the combined action of the introduction of deep trapping states and the scattering effect by the added nanoparticles.
Rowland, D. R.
2007-01-01
The physical analysis of a uniformly accelerating point charge provides a rich problem to explore in advanced courses in electrodynamics and relativity since it brings together fundamental concepts in relation to electromagnetic radiation, Einstein's equivalence principle and the inertial mass of field energy in ways that reveal subtleties in each…
Charge Transport in Spiro-OMeTAD Investigated through Space-Charge-Limited Current Measurements
Röhr, Jason A.; Shi, Xingyuan; Haque, Saif A.; Kirchartz, Thomas; Nelson, Jenny
2018-04-01
Extracting charge-carrier mobilities for organic semiconductors from space-charge-limited conduction measurements is complicated in practice by nonideal factors such as trapping in defects and injection barriers. Here, we show that by allowing the bandlike charge-carrier mobility, trap characteristics, injection barrier heights, and the shunt resistance to vary in a multiple-trapping drift-diffusion model, a numerical fit can be obtained to the entire current density-voltage curve from experimental space-charge-limited current measurements on both symmetric and asymmetric 2 ,2',7 ,7' -tetrakis(N ,N -di-4-methoxyphenylamine)-9 ,9' -spirobifluorene (spiro-OMeTAD) single-carrier devices. This approach yields a bandlike mobility that is more than an order of magnitude higher than the effective mobility obtained using analytical approximations, such as the Mott-Gurney law and the moving-electrode equation. It is also shown that where these analytical approximations require a temperature-dependent effective mobility to achieve fits, the numerical model can yield a temperature-, electric-field-, and charge-carrier-density-independent mobility. Finally, we present an analytical model describing trap-limited current flow through a semiconductor in a symmetric single-carrier device. We compare the obtained charge-carrier mobility and trap characteristics from this analytical model to the results from the numerical model, showing excellent agreement. This work shows the importance of accounting for traps and injection barriers explicitly when analyzing current density-voltage curves from space-charge-limited current measurements.
CHAOTIC MOTION OF CHARGED PARTICLES IN AN ELECTROMAGNETIC FIELD SURROUNDING A ROTATING BLACK HOLE
International Nuclear Information System (INIS)
Takahashi, Masaaki; Koyama, Hiroko
2009-01-01
The observational data from some black hole candidates suggest the importance of electromagnetic fields in the vicinity of a black hole. Highly magnetized disk accretion may play an importance rule, and large-scale magnetic field may be formed above the disk surface. Then, we expect that the nature of the black hole spacetime would be revealed by magnetic phenomena near the black hole. We will start investigating the motion of a charged test particle which depends on the initial parameter setting in the black hole dipole magnetic field, which is a test field on the Kerr spacetime. Particularly, we study the spin effects of a rotating black hole on the motion of the charged test particle trapped in magnetic field lines. We make detailed analysis for the particle's trajectories by using the Poincare map method, and show the chaotic properties that depend on the black hole spin. We find that the dragging effects of the spacetime by a rotating black hole weaken the chaotic properties and generate regular trajectories for some sets of initial parameters, while the chaotic properties dominate on the trajectories for slowly rotating black hole cases. The dragging effects can generate the fourth adiabatic invariant on the particle motion approximately.
Jumbo Space Environment Simulation and Spacecraft Charging Chamber Characterization
2015-04-09
probes for Jumbo. Both probes are produced by Trek Inc. Trek probe model 370 is capable of -3 to 3kV and has an extremely fast, 50µs/kV response to...changing surface potentials. Trek probe 341B is capable of -20 to 20kV with a 200 µs/kV response time. During our charging experiments the probe sits...unlimited. 12 REFERENCES [1] R. D. Leach and M. B. Alexander, "Failures and anomalies attributed to spacecraft charging," NASA RP-1375, Marshall Space
Discrete space charge affected field emission: Flat and hemisphere emitters
Energy Technology Data Exchange (ETDEWEB)
Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil [Code 6854, Naval Research Laboratory, Washington, DC 20375 (United States); Shiffler, Donald A.; Tang, Wilkin [Air Force Research Laboratory, Kirtland AFB, New Mexico 87117 (United States); Rittersdorf, Ian M. [Code 6770, Naval Research Laboratory, Washington, DC 20375 (United States); Lebowitz, Joel L. [Department of Mathematics and Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States); Harris, John R. [U.S. Navy Reserve, New Orleans, Louisiana 70143 (United States); Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Petillo, John J. [Leidos, Billerica, Massachusetts 01821 (United States); Luginsland, John W. [Physics and Electronics Directorate, AFOSR, Arlington, Virginia 22203 (United States)
2015-05-21
Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.
On the electromagnetic field and the Teukolsky relations in arbitrary space-times
International Nuclear Information System (INIS)
Coll, B.; Ferrando, J.J.
1985-01-01
The relations on the electromagnetic field obtained by Teukolsky for type D, vacuum space-times are studied. The role played by the maxwellian geometry of the basic tetrad is shown. It is proved that Teukolsky relations are, generically, incomplete. Once completed, their generalization to arbitrary space-times is given [fr
Cancellation of the centrifugal space-charge force
International Nuclear Information System (INIS)
Lee, E.P.
1990-01-01
The transverse dynamics of high-energy electrons confined in curved geometry are examined, including the effects of space-charge-induced fields. Attention is restricted to the centrifugal-space-charge force, which is the result of noncancellation of beam-induced transverse electric and magnetic fields in the curved geometry. This force is shown to be nearly cancelled in the evaluation of the horizontal tune and chromaticity by another, often overlooked term in the equation of motion. The additional term is the consequence of oscillations of the kinetic energy, which accompany betatron oscillations in the beam-induced electric potential. In curved geometry this term is of first order in the amplitude of the radial oscillation. A highly simplified system model is employed so that physical effects appear in as clear a form as possible. We assume azimuthal and median plane symmetry, static fields, and ultrarelativistic particle velocity (1/γ 2 ->0). (author) 9 refs
Modeling space charge in beams for heavy-ion fusion
International Nuclear Information System (INIS)
Sharp, W.M.
1995-01-01
A new analytic model is presented which accurately estimates the radially averaged axial component of the space-charge field of an axisymmetric heavy-ion beam in a cylindrical beam pipe. The model recovers details of the field near the beam ends that are overlooked by simpler models, and the results compare well to exact solutions of Poisson's equation. Field values are shown for several simple beam profiles and are compared with values obtained from simpler models
Space charge effects and coherent stability limits in barrier buckets
Directory of Open Access Journals (Sweden)
Oliver Boine-Frankenheim
2003-03-01
Full Text Available A large-scale Vlasov simulation study of the microwave instability below transition energy in a beam confined between two barrier pulses is performed. Starting from a matched distribution function for the confined ion beam including the space charge impedance the stability threshold in the longitudinal impedance plane is obtained. A simple stability criterium is found to be in good agreement with the simulation results.
Influence of space charge during the injection in Saturne II
International Nuclear Information System (INIS)
Lemaire, J.L.
Calculations were made in which a fixed acceptance window, established since the beginning of the injection, was considered, and a filling pattern that was a linear function of time was supposed. Evidently, these conditions are no longer met if the space charge modifies the wave number of the beam and, consequently, the filling rate changes with time. The importance of these conditions upon injection for the theoretical operation point zone 3 is reported
Halo and space charge issues in the SNS Ring
International Nuclear Information System (INIS)
Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.
2000-01-01
The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring
Space-charge effects in vacuum-deposited polyimide layer
Czech Academy of Sciences Publication Activity Database
Zhivkov, I.; Strijkova, V.; Spassova, E.; Danev, G.; Nešpůrek, Stanislav; Iwamoto, M.
2005-01-01
Roč. 7, č. 1 (2005), s. 245-248 ISSN 1454-4164 R&D Projects: GA MŠk ME 558 Grant - others:Ministry of Education and Science(BG) X-1322 Institutional research plan: CEZ:AV0Z40500505 Keywords : polyimide * electrical conductivity * space-charge spectroscopy Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.138, year: 2005
Space-charge effects in Penning ion traps
Czech Academy of Sciences Publication Activity Database
Porobic, T.; Beck, M.; Breitenfeldt, M.; Couratin, C.; Finlay, P.; Knecht, A.; Fabian, X.; Friedag, P.; Flechard, X.; Lienard, E.; Ban, G.; Zákoucký, Dalibor; Soti, G.; Van Gorp, S.; Weinheimer, C.; Wursten, E.; Severijns, N.
2015-01-01
Roč. 785, JUN (2015), s. 153-162 ISSN 0168-9002 R&D Projects: GA MŠk LA08015; GA MŠk(CZ) LG13031 Institutional support: RVO:61389005 Keywords : Penning trap * space-charge * magnetron motion * ion trapping * buffer gas cooling * ion cyclotron resonance Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.200, year: 2015
Halo and space charge issues in the SNS Ring
Energy Technology Data Exchange (ETDEWEB)
Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.
2000-06-30
The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring.
The space charge effects on the slow extraction process
International Nuclear Information System (INIS)
Ohmori, Chihiro.
1992-06-01
The calculation of the slow extraction which includes the space charge effects has been performed for the Compressor/Stretcher Ring (CSR) of the proposed Japanese Hadron Project. We have investigated the slow extraction of 1 GeV proton beam with an average current of 100μA. Calculation shows not only the emittance growth of the extracted beam but also decrease of the extraction efficiency and discontinuity of beam spill. (author)
Analysis of beam envelope by transverse space charge effect
International Nuclear Information System (INIS)
Toyama, Shin'ichi
1997-09-01
It is important for high current accelerators to estimate the contribution of the space charge effect to keep the beam off its beak up. The application of an envelope equation is examined in previous report in which the beam is just coasting beam (non accelerating). The analysis of space charge effect is necessary for the comparison in coming accelerator test in PNC. In order to evaluate the beam behavior in high current, the beam dynamics and beam parameters which are input to the equation for the evaluation are developed and make it ready to estimate the beam transverse dynamics by the space charge. The estimate needs to have enough accuracy for advanced code calculation. After the preparation of the analytic expression of transverse motion, the non-linear differential equation of beam dynamics is solved by a numerical method on a personal computer. The beam envelope from the equation is estimated by means of the beam emittance, current and energy. The result from the analysis shows that the transverse beam broadening is scarecely small around the beam current value of PNC design. The contribution to the beam broadening of PNC linac comes from its beam emittance. The beam broadening in 100 MeV case is almost negligible in the view of transverse space charge effect. Therefore, the electron beam is stable up to 10 A order in PNC linac design. Of course, the problem for RF supply is out of consideration here. It is important to estimate other longitudinal effect such as beam bunch effect which is lasting unevaluated. (author)
Incorporating space charge in the transverse phase-space matching and tomography at PITZ
Energy Technology Data Exchange (ETDEWEB)
Kourkafas, Georgios
2015-11-15
The ever-expanding achievements in the field of particle accelerators push their specifications to very demanding levels. The performance of many modern applications depends on their ability to be operated with high bunch charges confined in small volumes. However, the consequence of increased intensity is strong space-charge forces, which perplex the beam manipulation and undermine the beam quality. As a result, reliable methods are needed to control and measure the accelerated particles under these extraordinary conditions. The phase space tomography is a diagnostic technique which can reveal details of the transverse beam parameters for a wide range of intensities and energies, with minimal influence from the machine instabilities, in a quasi non-destructive way. The accuracy of this method relies on the precise knowledge and control of the particle dynamics under the influence of space charge in different stages of the measurement. On the one hand, the matching of the beam to the measurement's design transverse parameters requires a procedure which efficiently compensates the effects of space charge. Depending on the structure of the magnetic lattice, different aspects of these effects prevail, therefore different strategies have to be developed. On the other hand, the impact of the space-charge forces on the phase-space transformations during the data acquisition has to be included in the model which is used for the tomographic reconstruction. The aim of this thesis is to provide and test time-efficient solutions for the incorporation of space charge in the transverse beam matching and phase space tomography.
Incorporating space charge in the transverse phase-space matching and tomography at PITZ
International Nuclear Information System (INIS)
Kourkafas, Georgios
2015-11-01
The ever-expanding achievements in the field of particle accelerators push their specifications to very demanding levels. The performance of many modern applications depends on their ability to be operated with high bunch charges confined in small volumes. However, the consequence of increased intensity is strong space-charge forces, which perplex the beam manipulation and undermine the beam quality. As a result, reliable methods are needed to control and measure the accelerated particles under these extraordinary conditions. The phase space tomography is a diagnostic technique which can reveal details of the transverse beam parameters for a wide range of intensities and energies, with minimal influence from the machine instabilities, in a quasi non-destructive way. The accuracy of this method relies on the precise knowledge and control of the particle dynamics under the influence of space charge in different stages of the measurement. On the one hand, the matching of the beam to the measurement's design transverse parameters requires a procedure which efficiently compensates the effects of space charge. Depending on the structure of the magnetic lattice, different aspects of these effects prevail, therefore different strategies have to be developed. On the other hand, the impact of the space-charge forces on the phase-space transformations during the data acquisition has to be included in the model which is used for the tomographic reconstruction. The aim of this thesis is to provide and test time-efficient solutions for the incorporation of space charge in the transverse beam matching and phase space tomography.
Particle-in-cell/accelerator code for space-charge dominated beam simulation
Energy Technology Data Exchange (ETDEWEB)
2012-05-08
Warp is a multidimensional discrete-particle beam simulation program designed to be applicable where the beam space-charge is non-negligible or dominant. It is being developed in a collaboration among LLNL, LBNL and the University of Maryland. It was originally designed and optimized for heave ion fusion accelerator physics studies, but has received use in a broader range of applications, including for example laser wakefield accelerators, e-cloud studies in high enery accelerators, particle traps and other areas. At present it incorporates 3-D, axisymmetric (r,z) planar (x-z) and transverse slice (x,y) descriptions, with both electrostatic and electro-magnetic fields, and a beam envelope model. The code is guilt atop the Python interpreter language.
A Method to Overcome Space Charge at Injection
International Nuclear Information System (INIS)
Ya. Derbenev
2005-01-01
The transverse space charge forces in a high current, low energy beam can be reduced by mean of a large increase of the beam's transverse sizes while maintaining the beam area in the 4D phase space. This can be achieved by transforming the beam area in phase space of each of two normal 2D transverse (either plane or circular) modes from a spot shape into a narrow ring of a large amplitude, but homogeneous in phase. Such a transformation results from the beam evolution in the island of a dipole resonance when the amplitude width of the island shrinks adiabatically. After stacking (by using stripping foils or cooling) the beam in such a state and accelerating to energies sufficiently high that the space charge becomes insignificant, the beam then can be returned back to a normal spot shape by applying the reverse transformation. An arrangement that can provide such beam gymnastics along a transport line after a linac and before a booster and/or in a ring with circulating beam will be described and numerical estimates will be presented. Other potential applications of the method will be briefly discussed
High-order space charge effects using automatic differentiation
International Nuclear Information System (INIS)
Reusch, Michael F.; Bruhwiler, David L.
1997-01-01
The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach
High-order space charge effects using automatic differentiation
International Nuclear Information System (INIS)
Reusch, M.F.; Bruhwiler, D.L.; Computer Accelerator Physics Conference Williamsburg, Virginia 1996)
1997-01-01
The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach. copyright 1997 American Institute of Physics
Grant, Ian S
1990-01-01
The Manchester Physics Series General Editors: D. J. Sandiford; F. Mandl; A. C. Phillips Department of Physics and Astronomy, University of Manchester Properties of Matter B. H. Flowers and E. Mendoza Optics Second Edition F. G. Smith and J. H. Thomson Statistical Physics Second Edition F. Mandl Electromagnetism Second Edition I. S. Grant and W. R. Phillips Statistics R. J. Barlow Solid State Physics Second Edition J. R. Hook and H. E. Hall Quantum Mechanics F. Mandl Particle Physics Second Edition B. R. Martin and G. Shaw the Physics of Stars Second Edition A. C. Phillips Computing for Scient
Non linear dynamic of Langmuir and electromagnetic waves in space plasmas
International Nuclear Information System (INIS)
Guede, Jose Ricardo Abalde
1995-11-01
The aim of this work is to study the nonlinear dynamics of Langmuir and electromagnetic waves in space plasmas. Firstly, the generalized Zakharov equations are derived which are used to study the hybrid parametric instability involving the generation of daughter Langmuir, electromagnetic and ion-acoustic waves induced by two counter-propagating Langmuir pump waves with different amplitudes based on a coupled dispersion relation. Secondly, starting from the generalized Zakharov equations the linear and nonlinear coupled mode theories of three-wave and four-wave parametric interactions are developed, respectively. In three-waves processes, a Langmuir wave decays into another Langmuir wave and an ion-acoustic wave (electrostatic parametric decay) or into an electromagnetic wave and an ion-acoustic wave (electromagnetic parametric decay). In four-wave (modulational) processes, the interaction involves two wave triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplet the coupling of a pump wave with a low-frequency wave generate an anti-Stokes wave. These modulational processes are convective and resonant processes wherein the low-frequency modes are Eigenmodes of plasma and are known as the stimulated modulational processes. Four such processes are investigated in this thesis: two with Langmuir pump waves (electrostatic and hybrid stimulated modulation processes) and the other two with electromagnetic pump waves (stimulated modulation Brillouin scattering and electromagnetic stimulated modulation process). Applications of the theoretical results in space plasmas are discussed. In particular, it is shown that the electrostatic and electromagnetic parametric decay processes of Langmuir waves can model the generation and modulation of radio emissions and Langmuir waves in the
Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films
Hu, Weijin; Wang, Zhihong; Du, Yuanmin; Zhang, Xixiang; Wu, Tao
2014-01-01
We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current
Silva, António; Urbano, Diana; Kim, Hyun-Chul
2018-02-01
We investigate the flavor decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model (χQSM) with symmetry-conserving quantization. We consider the rotational 1/N_c and linear strange-quark mass (ms) corrections. We discuss the results of the flavor-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). Finally, we discuss the transverse charge densities for both unpolarized and polarized nucleons. The transverse charge density inside a neutron turns out to be negative in the vicinity of the center within the SU(3) χQSM, which can be explained by the contribution of the strange quark.
3D Simulations of Space Charge Effects in Particle Beams
Energy Technology Data Exchange (ETDEWEB)
Adelmann, A
2002-10-01
For the first time, it is possible to calculate the complicated three-dimensional proton accelerator structures at the Paul Scherrer Institut (PSI). Under consideration are external and self effects, arising from guiding and space-charge forces. This thesis has as its theme the design, implementation and validation of a tracking program for charged particles in accelerator structures. This work form part of the discipline of Computational Science and Engineering (CSE), more specifically in computational accelerator modelling. The physical model is based on the collisionless Vlasov-Maxwell theory, justified by the low density ({approx} 10{sup 9} protons/cm{sup 3}) of the beam and of the residual gas. The probability of large angle scattering between the protons and the residual gas is then sufficiently low, as can be estimated by considering the mean free path and the total distance a particle travels in the accelerator structure. (author)
SNS accumulator ring design and space charge considerations
Energy Technology Data Exchange (ETDEWEB)
Weng, W.T.
1998-08-01
The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5 {micro}s with average beam power of 1 MW. To achieve such purpose, a proton storage ring operated at 60 Hz with 1 {times} 10{sup 14} protons per pulse at 1 GeV is required. The Accumulator Ring (AR) receives 1 msec long H{sup {minus}} beam bunches of 28 mA from a 1 GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1 mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generatino and beam collimation etc. is discussed.
SNS ACCUMULATOR RING DESIGN AND SPACE CHARGE CONSIDERATIONS
Energy Technology Data Exchange (ETDEWEB)
WENG,W.T.
1998-05-04
The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5{micro}s with average beam power of 1MW. To achieve such purpose, a proton storage ring operated at 60Hz with 1 x 10{sup 14} protons per pulse at 1GeV is required. The Accumulator Ring (AR) receives 1msec long H{sup {minus}} beam bunches of 28mA from a 1GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generation and beam collimation etc. is discussed.
3D Simulations of Space Charge Effects in Particle Beams
International Nuclear Information System (INIS)
Adelmann, A.
2002-10-01
For the first time, it is possible to calculate the complicated three-dimensional proton accelerator structures at the Paul Scherrer Institut (PSI). Under consideration are external and self effects, arising from guiding and space-charge forces. This thesis has as its theme the design, implementation and validation of a tracking program for charged particles in accelerator structures. This work form part of the discipline of Computational Science and Engineering (CSE), more specifically in computational accelerator modelling. The physical model is based on the collisionless Vlasov-Maxwell theory, justified by the low density (∼ 10 9 protons/cm 3 ) of the beam and of the residual gas. The probability of large angle scattering between the protons and the residual gas is then sufficiently low, as can be estimated by considering the mean free path and the total distance a particle travels in the accelerator structure. (author)
SNS accumulator ring design and space charge considerations
International Nuclear Information System (INIS)
Weng, W.T.
1998-01-01
The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5micros with average beam power of 1MW. To achieve such purpose, a proton storage ring operated at 60Hz with 1 x 10 14 protons per pulse at 1GeV is required. The Accumulator Ring (AR) receives 1msec long H - beam bunches of 28mA from a 1GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generation and beam collimation etc. is discussed
Chaos in Time-Dependent Space-Charge Potentials
Betzel, Gregory T; Sideris, Ioannis V
2005-01-01
We consider a spherically symmetric, homologously breathing, space-charge-dominated beam bunch in the spirit of the particle-core model. The question we ask is: How does the time dependence influence the population of chaotic orbits? The static beam has zero chaotic orbits; the equation of particle motion is integrable up to quadrature. This is generally not true once the bunch is set into oscillation. We quantify the population of chaotic orbits as a function of space charge and oscillation amplitude (mismatch). We also apply a newly developed measure of chaos, one that distinguishes between regular, sticky, and wildly chaotic orbits, to characterize the phase space in detail. We then introduce colored noise into the system and show how its presence modifies the dynamics. One finding is that, despite the presence of a sizeable population of chaotic orbits, halo formation in the homologously breathing beam is much less prevalent than in an envelope-matched counterpart wherein an internal collective mode is ex...
International Nuclear Information System (INIS)
Yang, Zhanfeng; Liu, Guozhi; Shao, Hao; Chen, Changhua; Sun, Jun
2013-01-01
This paper reports the space-charge limited current (SLC) and virtual cathode behaviors in one-dimensional grounded drift space. A simple general analytical solution and an approximate solution for the planar diode are given. Through a semi-analytical method, a general solution for SLC in one-dimensional drift space is obtained. The behaviors of virtual cathode in the drift space, including dominant frequency, electron transit time, position, and transmitted current, are yielded analytically. The relationship between the frequency of the virtual cathode oscillation and the injected current presented may explain previously reported numerical works. Results are significant in facilitating estimations and further analytical studies
Space-charge effects in high-energy photoemission
Energy Technology Data Exchange (ETDEWEB)
Verna, Adriano, E-mail: adriano.verna@uniroma3.it [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); CNISM Unità di Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Greco, Giorgia [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Lollobrigida, Valerio [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Scuola Dottorale in Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Offi, Francesco; Stefani, Giovanni [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); CNISM Unità di Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy)
2016-05-15
Highlights: • N-body simulations of interacting photoelectrons in hard X-ray experiments. • Secondary electrons have a pivotal role in determining the energy broadening. • Space charge has negligible effects on the photoelectron momentum distribution. • A simple model provides the characteristic time for energy-broadening mechanism. • The feasibility of time-resolved high-energy experiments with FELs is discussed. - Abstract: Pump-and-probe photoelectron spectroscopy (PES) with femtosecond pulsed sources opens new perspectives in the investigation of the ultrafast dynamics of physical and chemical processes at the surfaces and interfaces of solids. Nevertheless, for very intense photon pulses a large number of photoelectrons are simultaneously emitted and their mutual Coulomb repulsion is sufficiently strong to significantly modify their trajectory and kinetic energy. This phenomenon, referred as space-charge effect, determines a broadening and shift in energy for the typical PES structures and a dramatic loss of energy resolution. In this article we examine the effects of space charge in PES with a particular focus on time-resolved hard X-ray (∼10 keV) experiments. The trajectory of the electrons photoemitted from pure Cu in a hard X-ray PES experiment has been reproduced through N-body simulations and the broadening of the photoemission core-level peaks has been monitored as a function of various parameters (photons per pulse, linear dimension of the photon spot, photon energy). The energy broadening results directly proportional to the number N of electrons emitted per pulse (mainly represented by secondary electrons) and inversely proportional to the linear dimension a of the photon spot on the sample surface, in agreement with the literature data about ultraviolet and soft X-ray experiments. The evolution in time of the energy broadening during the flight of the photoelectrons is also studied. Despite its detrimental consequences on the energy
Quantum computing based on space states without charge transfer
International Nuclear Information System (INIS)
Vyurkov, V.; Filippov, S.; Gorelik, L.
2010-01-01
An implementation of a quantum computer based on space states in double quantum dots is discussed. There is no charge transfer in qubits during a calculation, therefore, uncontrolled entanglement between qubits due to long-range Coulomb interaction is suppressed. Encoding and processing of quantum information is merely performed on symmetric and antisymmetric states of the electron in double quantum dots. Other plausible sources of decoherence caused by interaction with phonons and gates could be substantially suppressed in the structure as well. We also demonstrate how all necessary quantum logic operations, initialization, writing, and read-out could be carried out in the computer.
Space charge effects for multipactor in coaxial lines
Energy Technology Data Exchange (ETDEWEB)
Sorolla, E., E-mail: eden.sorolla@xlim.fr [XLIM, UMR 7252, Université de Limoges/CNRS, 123 Av. Albert Thomas, 87060 Limoges (France); Sounas, A.; Mattes, M. [Laboratoire d' Électromagnétisme et d' Acoustique (LEMA), École Polytechnique Fédérale de Lausanne, Station 11, CH-1015 Lausanne (Switzerland)
2015-03-15
Multipactor is a hazardous vacuum discharge produced by secondary electron emission within microwave devices of particle accelerators and telecommunication satellites. This work analyzes the dynamics of the multipactor discharge within a coaxial line for the mono-energetic electron emission model taking into account the space charge effects. The steady-state is predicted by the proposed model and an analytical expression for the maximum number of electrons released by the discharge presented. This could help to link simulations to experiments and define a multipactor onset criterion.
Investigations of the Dynamics of Space Charged Dominated Beams
International Nuclear Information System (INIS)
York, Richard C.
2002-01-01
We propose to perform investigations of the dynamics of space charge dominated beams. These investigations will support present activities such as the electron ring project at the University of Maryland as well as provide an improved basis for future accelerator designs. Computer simulations will provide the primary research element with improved code development being an integral part of the activities during the first period. We believe that one of the code development projects provides a unique strategy for the inclusion of longitudinal dynamics, and that this concept should provide a computationally rapid research tool
Space charge effects for multipactor in coaxial lines
International Nuclear Information System (INIS)
Sorolla, E.; Sounas, A.; Mattes, M.
2015-01-01
Multipactor is a hazardous vacuum discharge produced by secondary electron emission within microwave devices of particle accelerators and telecommunication satellites. This work analyzes the dynamics of the multipactor discharge within a coaxial line for the mono-energetic electron emission model taking into account the space charge effects. The steady-state is predicted by the proposed model and an analytical expression for the maximum number of electrons released by the discharge presented. This could help to link simulations to experiments and define a multipactor onset criterion
Space charge effect in SQS transition in a gas counter
International Nuclear Information System (INIS)
Ohgaki, Hideaki; Kametani, Hitoshi; Fujita, Yasuyuki; Uozumi, Yuusuke; Ijiri, Hidenobu; Matoba, Masaru; Sakae, Takeji; Koori, Norihiko
1990-01-01
Systematic investigation of the gas multiplication characteristics in the transition region from proportional to SQS mode in a cylindrical proportional counter has been performed. The property of saturation of the gas multiplication factor can be reproduced using the effective electric field which is corrected for the space charge related to the positive ion density in the avalanche. Photon-mediated gas multiplication can explain the large jump phenomenon of the SQS transition. It is shown that the effective electric field in the avalanche becomes almost zero near the anode surface (Meek's streamer condition) at the 50% transition voltage and the region of its maximum moves slightly away from the anode surface. (orig.)
Program NAJOCSC and space charge effect simulation in C01
International Nuclear Information System (INIS)
Tang, J.Y.; Chabert, A.; Baron, E.
1999-01-01
During the beam tests of the THI project at GANIL, it was found it difficult to increase the beam power above 2 kW at CSS2 extraction. The space charge effect (abbreviated as S.C. effect) in cyclotrons is suspected to play some role in the phenomenon, especially the longitudinal S.C. one and also the coupling between longitudinal and radial motions. The injector cyclotron C01 is studied, and the role played by the S.C. effect in this cyclotron in the THI case is investigated by a simulation method. (K.A.)
Investigations of the Dynamics of Space Charged Dominated Beams
Energy Technology Data Exchange (ETDEWEB)
York, Richard C.
2002-08-01
We propose to perform investigations of the dynamics of space charge dominated beams. These investigations will support present activities such as the electron ring project at the University of Maryland as well as provide an improved basis for future accelerator designs. Computer simulations will provide the primary research element with improved code development being an integral part of the activities during the first period. We believe that one of the code development projects provides a unique strategy for the inclusion of longitudinal dynamics, and that this concept should provide a computationally rapid research tool.
Simulations of space charge neutralization in a magnetized electron cooler
Energy Technology Data Exchange (ETDEWEB)
Gerity, James [Texas A-M; McIntyre, Peter M. [Texas A-M; Bruhwiler, David Leslie [RadiaSoft, Boulder; Hall, Christopher [RadiaSoft, Boulder; Moens, Vince Jan [Ecole Polytechnique, Lausanne; Park, Chong Shik [Fermilab; Stancari, Giulio [Fermilab
2017-02-02
Magnetized electron cooling at relativistic energies and Ampere scale current is essential to achieve the proposed ion luminosities in a future electron-ion collider (EIC). Neutralization of the space charge in such a cooler can significantly increase the magnetized dynamic friction and, hence, the cooling rate. The Warp framework is being used to simulate magnetized electron beam dynamics during and after the build-up of neutralizing ions, via ionization of residual gas in the cooler. The design follows previous experiments at Fermilab as a verification case. We also discuss the relevance to EIC designs.
International Nuclear Information System (INIS)
Oraevskij, V.N.; Golyshev, S.A.; Levitin, A.E.; Breus, T.K.; Ivanova, S.V.; Komarov, F.I.; Rapoport, S.I.
1995-01-01
Space and time distribution of the electric and magnetic fields and current systems in the near terrestrial space (electromagnetic weather) were studied in connection with ambulance calls in Moscow, Russia, related to the cardia-vascular diseases. The some examples of the correlations between the solar activity parameters and geomagnetic variations and the events of the extreme number of ambulance calls were presented. 4 refs., 5 figs., 2 tabs
Jia, Shouqing; La, Dongsheng; Ma, Xuelian
2018-04-01
The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.
Camera memory study for large space telescope. [charge coupled devices
Hoffman, C. P.; Brewer, J. E.; Brager, E. A.; Farnsworth, D. L.
1975-01-01
Specifications were developed for a memory system to be used as the storage media for camera detectors on the large space telescope (LST) satellite. Detectors with limited internal storage time such as intensities charge coupled devices and silicon intensified targets are implied. The general characteristics are reported of different approaches to the memory system with comparisons made within the guidelines set forth for the LST application. Priority ordering of comparisons is on the basis of cost, reliability, power, and physical characteristics. Specific rationales are provided for the rejection of unsuitable memory technologies. A recommended technology was selected and used to establish specifications for a breadboard memory. Procurement scheduling is provided for delivery of system breadboards in 1976, prototypes in 1978, and space qualified units in 1980.
Electromagnetic processes in nucleus-nucleus collisions relating to space radiation research
Norbury, John W.
1992-01-01
Most of the papers within this report deal with electromagnetic processes in nucleus-nucleus collisions which are of concern in the space radiation program. In particular, the removal of one and two nucleons via both electromagnetic and strong interaction processes has been extensively investigated. The theory of relativistic Coulomb fission has also been developed. Several papers on quark models also appear. Finally, note that the theoretical methods developed in this work have been directly applied to the task of radiation protection of astronauts. This has been done by parameterizing the theoretical formalism in such a fashion that it can be used in cosmic ray transport codes.
Transport and matching of low energy space charge dominated beams
International Nuclear Information System (INIS)
Pandit, V.S.
2013-01-01
The transport and matching of low energy high intensity beams from the ion source to the subsequent accelerating structure are of considerable interest in recent years for variety of applications such as Accelerator driven system (ADSS), transmutation of nuclear waste, spallation neutron sources etc. It is essential to perform detailed simulations with experimentation to predict the beam evolution in the presence of nonlinear self as well as external fields before the design of the next accelerating structure is finalized. In order to study and settle various physics and technical issues related with transport of space charge dominated beams we have developed a 2.45 GHz microwave ion source at VECC which is now delivering more than 10 mA proton beam current at 80 keV. We have successfully transported well collimated 8 mA proton beam through the solenoid based 3 meter long transport line and studied various beam properties. We have also studied the transport of beam through spiral inflector at low beam current ∼ 1mA. In this article we will discuss the beam transport issues and describe a technique for simulation of beam envelopes in presence of linear space charge effects. We use canonical description of the motion of a single particle and then obtain first order differential equations for evolution of the moments of beam ensemble by assuming uniform distribution of the beam. We will also discuss the methodology used in the simulations to understand the observed beam behaviour during transport. (author)
Injection space charge: enlargements of flux density functioning point choice
International Nuclear Information System (INIS)
Ropert, A.
In Saturne, injection consists of a synchrobetatron filling of the chamber, with the goal of providing a beam with the following characteristics circulating in the machine: horizontal flux density 90 πmm mrd, vertical flux density 210 πmm mrd, dispersion in moments +- 7 x 10 -3 , and number of particles 2 x 10 12 . The determination of the principal injection parameters was made by means of GOC calculation programs. The goal of this study is to show a certain number of phenomena induced by the forces due to space charge and left suspended up to this point: variations in the intensity injectable into the machine extension of the beam occupation zone in the ν/sub x'/ ν/sub z/ diagram, and turn-turn interactions. The effects of the space charge lead to a deterioration of the injected beam for certain functioning points leading to the selection of a zone in the ν/sub x'/ ν/sub z/ diagram that is particularly suitable for beam injection
An FPGA computing demo core for space charge simulation
International Nuclear Information System (INIS)
Wu, Jinyuan; Huang, Yifei
2009-01-01
In accelerator physics, space charge simulation requires large amount of computing power. In a particle system, each calculation requires time/resource consuming operations such as multiplications, divisions, and square roots. Because of the flexibility of field programmable gate arrays (FPGAs), we implemented this task with efficient use of the available computing resources and completely eliminated non-calculating operations that are indispensable in regular micro-processors (e.g. instruction fetch, instruction decoding, etc.). We designed and tested a 16-bit demo core for computing Coulomb's force in an Altera Cyclone II FPGA device. To save resources, the inverse square-root cube operation in our design is computed using a memory look-up table addressed with nine to ten most significant non-zero bits. At 200 MHz internal clock, our demo core reaches a throughput of 200 M pairs/s/core, faster than a typical 2 GHz micro-processor by about a factor of 10. Temperature and power consumption of FPGAs were also lower than those of micro-processors. Fast and convenient, FPGAs can serve as alternatives to time-consuming micro-processors for space charge simulation.
A modified space charge routine for high intensity bunched beams
International Nuclear Information System (INIS)
Lapostolle, P.; Garnett, R.W.; Wangler, T.P.
1996-01-01
In 1991 a space charge calculation for bunched beam with a three-dimensional ellipsoid was proposed, replacing the usual SCHEFF routines. It removes the cylindrical symmetry required in SCHEFF and avoids the point to point interaction computation, whose number of simulation points is limited. This routine has now been improved with the introduction of two or three ellipsoids giving a good representation of the complex non-symmetrical form of the bunch (unlike the 3-d ellipsoidal assumption). The ellipsoidal density distributions are computed with a new method, avoiding the difficulty encountered near the centre (the axis in 2-d problems) by the previous method. It also provides a check of the ellipsoidal symmetry for each part of the distribution. Finally, the Fourier analysis reported in 1991 has been replaced by a very convenient Hermite expansion, which gives a simple but accurate representation of practical distributions. Comparisons with other space charge routines have been made, particularly with the ones applying other techniques such as SCHEFF. Introduced in the versatile beam dynamics code DYNAC, it should provide a good tool for the study of the various parameters responsible for the halo formation in high intensity linacs. (orig.)
Working Group 2 summary: Space charge effects in bending systems
International Nuclear Information System (INIS)
Bohn, C.L.; Emma, P.J.
2000-01-01
At the start of the Workshop, the authors asked the Working Group 2 participants to concentrate on three basic goals: (1) survey the status of how comprehensively the physics concerning space-charge effects in bends is understood and how complete is the available ensemble of analytic and computational tools; (2) guided by data from experiments and operational experience, identify sources of, and cures for, beam degradation; and (3) review space-charge physics in rings and the limitations it introduces. As the Workshop unfolded, the third goal naturally folded into the other two goals, and these goals, they believe, were fulfilled in that the Working Group was able to compile an end product consisting of a set of recommendations for potentially fruitful future work. This summary constitutes an overview of the deliberations of the Working Group, and it is their hope that the summary clarifies the motivation for the recommended work listed at the end. The summary is organized according to the two aforementioned goals, and the prime topics of discussion appear as subsections under these goals
An FPGA computing demo core for space charge simulation
Energy Technology Data Exchange (ETDEWEB)
Wu, Jinyuan; Huang, Yifei; /Fermilab
2009-01-01
In accelerator physics, space charge simulation requires large amount of computing power. In a particle system, each calculation requires time/resource consuming operations such as multiplications, divisions, and square roots. Because of the flexibility of field programmable gate arrays (FPGAs), we implemented this task with efficient use of the available computing resources and completely eliminated non-calculating operations that are indispensable in regular micro-processors (e.g. instruction fetch, instruction decoding, etc.). We designed and tested a 16-bit demo core for computing Coulomb's force in an Altera Cyclone II FPGA device. To save resources, the inverse square-root cube operation in our design is computed using a memory look-up table addressed with nine to ten most significant non-zero bits. At 200 MHz internal clock, our demo core reaches a throughput of 200 M pairs/s/core, faster than a typical 2 GHz micro-processor by about a factor of 10. Temperature and power consumption of FPGAs were also lower than those of micro-processors. Fast and convenient, FPGAs can serve as alternatives to time-consuming micro-processors for space charge simulation.
Effect of surface topography and morphology on space charge packets in polyethylene
International Nuclear Information System (INIS)
Zhou Yuanxiang; Wang Yunshan; Sun Qinghua; Wang Ninghua
2009-01-01
Polyethylene (PE) is a major kind of internal insulating material. With great progresses of space charge measurement technologies in the last three decades, lots of researches are focused on space charge in PE. The heat pressing and annealing condition of polyethylene affect its morphology obviously. During the heat pressing, the surface of PE forms different surface topographies because of different substrate materials. Surface topography has great relation to the epitaxial crystallization layer and influences the space charge characteristic of PE dramatically. This paper studied the formation process of different surface topographies and their micrographic characters in low density polyethylene (LDPE). pulsed electro-acoustic (PEA) method was used to measure the space charge distribution of samples with different surface topographies and morphologies in LDPE. The effect of surface topography and morphology to space charge packet were studied. The surface topography has great influence on space charge packet polarity and morphology has influence on both movement speed rate and polarity of space charge packet.
Kholmetskii, A. L.; Missevitch, O. V.; Yarman, T.
2018-05-01
We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic (EM) field must be presented as the superposition of more fundamental quantum phases emerging for elementary charges. Using this idea, we find two new fundamental quantum phases for point-like charges, next to the known electric and magnetic Aharonov-Bohm (A-B) phases, named by us as the complementary electric and magnetic phases, correspondingly. We further demonstrate that these new phases can indeed be derived via the Schrödinger equation for a particle in an EM field, where however the operator of momentum is re-defined via the replacement of the canonical momentum of particle by the sum of its mechanical momentum and interactional field momentum for a system "charged particle and a macroscopic source of EM field". The implications of the obtained results are discussed.
International Nuclear Information System (INIS)
Forssen, C.; Caurier, E.; Navratil, P.
2009-01-01
Recently, charge radii and ground-state electromagnetic moments of Li and Be isotopes were measured precisely. We have performed large-scale ab initio no-core shell model calculations for these isotopes using high-precision nucleon-nucleon potentials. The isotopic trends of our computed charge radii and quadrupole and magnetic-dipole moments are in good agreement with experimental results with the exception of the 11 Li charge radius. The magnetic moments are in particular well described, whereas the absolute magnitudes of the quadrupole moments are about 10% too small. The small magnitude of the 6 Li quadrupole moment is reproduced, and with the CD-Bonn NN potential, also its correct sign
Electrostatic storage ring with focusing provided by the space charge of an electron plasma
International Nuclear Information System (INIS)
Pacheco, J. L.; Ordonez, C. A.; Weathers, D. L.
2013-01-01
Electrostatic storage rings are used for a variety of atomic physics studies. An advantage of electrostatic storage rings is that heavy ions can be confined. An electrostatic storage ring that employs the space charge of an electron plasma for focusing is described. An additional advantage of the present concept is that slow ions, or even a stationary ion plasma, can be confined. The concept employs an artificially structured boundary, which is defined at present as one that produces a spatially periodic static field such that the spatial period and range of the field are much smaller than the dimensions of a plasma or charged-particle beam that is confined by the field. An artificially structured boundary is used to confine a non-neutral electron plasma along the storage ring. The electron plasma would be effectively unmagnetized, except near an outer boundary where the confining electromagnetic field would reside. The electron plasma produces a radially inward electric field, which focuses the ion beam. Self-consistently computed radial beam profiles are reported.
A note on dust grain charging in space plasmas
Rosenberg, M.; Mendis, D. A.
1992-01-01
Central to the study of dust-plasma interactions in the solar system is the electrostatic charging of dust grains. While previous calculations have generally assumed that the distributions of electrons and ions in the plasma are Maxwellian, most space plasmas are observed to have non-Maxwellian tails and can often be fit by a generalized Lorentzian (kappa) distribution. Here we use such a distribution to reevaluate the grain potential, under the condition that the dominant currents to the grain are due to electron and ion collection, as is the case in certain regions of space. The magnitude of the grain potential is found to be larger than that in a Maxwellian plasma as long as the electrons are described by a kappa distribution: this enhancement increased with ion mass and decreasing electron kappa. The modification of the grain potential in generalized Lorentzian plasmas has implications for both the physics (e.g., grain growth and disruption) and the dynamics of dust in space plasmas. These are also briefly discussed.
Equilibrium phase-space distributions and space charge limits in linacs
International Nuclear Information System (INIS)
Lysenko, W.P.
1977-10-01
Limits on beam current and emittance in proton and heavy ion linear accelerators resulting from space charge forces are calculated. The method involves determining equilibrium distributions in phase space using a continuous focusing, no acceleration, model in two degrees of freedom using the coordinates r and z. A nonlinear Poisson equation must be solved numerically. This procedure is a matching between the longitudinal and transverse directions to minimize the effect of longitudinal-transverse coupling which is believed to be the main problem in emittance growth due to space charge in linacs. Limits on the Clinton P. Anderson Meson Physics Facility (LAMPF) accelerator performance are calculated as an example. The beam physics is described by a few space charge parameters so that accelerators with different physical parameters can be compared in a natural way. The main result of this parameter study is that the requirement of a high-intensity beam is best fulfilled with a low-frequency accelerator whereas the requirement of a high-brightness beam is best fulfilled with a high-frequency accelerator
Particle trapping by nonlinear resonances and space charge
International Nuclear Information System (INIS)
Franchetti, G.; Hofmann, I.
2006-01-01
In the FAIR [C.D.R. http://www.gsi.de/GSI Future/cdr/] facility planned at GSI high space charge effects and nonlinear dynamics may play an important role for limiting nominal machine performance. The most relevant interplay of these two effects on the single particle dynamics has been proposed in terms of trapping of particles into stable islands [G. Franchetti, I. Hofmann, AIP Conf. Proc. 642 (2002) 260]. Subsequent numerical studies and dedicated experiments have followed [G. Franchetti et al., Phys. Rev. ST Accel. Beams 6 (2003) 124201; G. Franchetti et al., AIP Conf. Proc. 773 (2005) 137]. We present here the effect of the chromaticity on the mechanisms of halo formation induced by particle trapping into resonances
PSR experience with beam losses, instabilities and space charge effects
International Nuclear Information System (INIS)
Macek, R.J.
1998-01-01
Average current from the PSR has been limited to ∼70 μA at 20 Hz by beam losses of 0.4 to 0.5 μA which arise from two principal causes, production of H 0 excited states and stored-beam scattering in the stripper foil. To reduce beam losses, an upgrade from the two-step H 0 injection to direct H - injection is underway and will be completed in 1998. Peak intensity from the PSR is limited by a strong instability that available evidence indicates is the two-stream e-p instability. New evidence for the e-p hypothesis is presented. At operating intensities, the incoherent space charge tune shift depresses both horizontal and vertical tunes past the integer without additional beam loss although some intensity-dependent emittance growth is observed. copyright 1998 American Institute of Physics
PSR experience with beam losses, instabilities and space charge effects
International Nuclear Information System (INIS)
Macek, Robert J.
1998-01-01
Average current from the PSR has been limited to ∼70 μA at 20 Hz by beam losses of 0.4 to 0.5 μA which arise from two principal causes, production of H 0 excited states and stored-beam scattering in the stripper foil. To reduce beam losses, an upgrade from the two-step H 0 injection to direct H - injection is underway and will be completed in 1998. Peak intensity from the PSR is limited by a strong instability that available evidence indicates is the two-stream e-p instability. New evidence for the e-p hypothesis is presented. At operating intensities, the incoherent space charge tune shift depresses both horizontal and vertical tunes past the integer without additional beam loss although some intensity-dependent emittance growth is observed
Space-Charge Simulation of Integrable Rapid Cycling Synchrotron
Energy Technology Data Exchange (ETDEWEB)
Eldred, Jeffery [Fermilab; Valishev, Alexander [Fermilab
2017-05-01
Integrable optics is an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use a Synergia space-charge simulation to investigate the application of integrable optics to a high-intensity hadron ring that could replace the Fermilab Booster. We find that incorporating integrability into the design suppresses the beam halo generated by a mismatched KV beam. Our integrable rapid cycling synchrotron (iRCS) design includes other features of modern ring design such as low momentum compaction factor and harmonically canceling sextupoles. Experimental tests of high-intensity beams in integrable lattices will take place over the next several years at the Fermilab Integrable Optics Test Accelerator (IOTA) and the University of Maryland Electron Ring (UMER).
A parallel implementation of particle tracking with space charge effects on an INTEL iPSC/860
International Nuclear Information System (INIS)
Chang, L.; Bourianoff, G.; Cole, B.; Machida, S.
1993-05-01
Particle-tracking simulation is one of the scientific applications that is well-suited to parallel computations. At the Superconducting Super Collider, it has been theoretically and empirically demonstrated that particle tracking on a designed lattice can achieve very high parallel efficiency on a MIMD Intel iPSC/860 machine. The key to such success is the realization that the particles can be tracked independently without considering their interaction. The perfectly parallel nature of particle tracking is broken if the interaction effects between particles are included. The space charge introduces an electromagnetic force that will affect the motion of tracked particles in 3-D space. For accurate modeling of the beam dynamics with space charge effects, one needs to solve three-dimensional Maxwell field equations, usually by a particle-in-cell (PIC) algorithm. This will require each particle to communicate with its neighbor grids to compute the momentum changes at each time step. It is expected that the 3-D PIC method will degrade parallel efficiency of particle-tracking implementation on any parallel computer. In this paper, we describe an efficient scheme for implementing particle tracking with space charge effects on an INTEL iPSC/860 machine. Experimental results show that a parallel efficiency of 75% can be obtained
Electromagnetic Field Theory in (N+1)-Space-Time : AModern Time-Domain Tensor/Array Introduction
De Hoop, A.T.
2012-01-01
In this paper, a modern time-domain introduction is presented for electromagnetic field theory in (N+1)-spacetime. It uses a consistent tensor/array notation that accommodates the description of electromagnetic phenomena in N-dimensional space (plus time), a requirement that turns up in present-day
Modelling natural electromagnetic interference in man-made conductors for space weather applications
Trichtchenko, Larisa
2016-04-01
Power transmission lines above the ground, cables and pipelines in the ground and under the sea, and in general all man-made long grounded conductors are exposed to the variations of the natural electromagnetic field. The resulting currents in the networks (commonly named geomagnetically induced currents, GIC), are produced by the conductive and/or inductive coupling and can compromise or even disrupt system operations and, in extreme cases, cause power blackouts, railway signalling mis-operation, or interfere with pipeline corrosion protection systems. To properly model the GIC in order to mitigate their impacts it is necessary to know the frequency dependence of the response of these systems to the geomagnetic variations which naturally span a wide frequency range. For that, the general equations of the electromagnetic induction in a multi-layered infinitely long cylinder (representing cable, power line wire, rail or pipeline) embedded in uniform media have been solved utilising methods widely used in geophysics. The derived electromagnetic fields and currents include the effects of the electromagnetic properties of each layer and of the different types of the surrounding media. This exact solution then has been used to examine the electromagnetic response of particular samples of long conducting structures to the external electromagnetic wave for a wide range of frequencies. Because the exact solution has a rather complicated structure, simple approximate analytical formulas have been proposed, analysed and compared with the results from the exact model. These approximate formulas show good coincidence in the frequency range spanning from geomagnetic storms (less than mHz) to pulsations (mHz to Hz) to atmospherics (kHz) and above, and can be recommended for use in space weather applications.
The role of space charge compensation for ion beam extraction and ion beam transport (invited)
International Nuclear Information System (INIS)
Spädtke, Peter
2014-01-01
Depending on the specific type of ion source, the ion beam is extracted either from an electrode surface or from a plasma. There is always an interface between the (almost) space charge compensated ion source plasma, and the extraction region in which the full space charge is influencing the ion beam itself. After extraction, the ion beam is to be transported towards an accelerating structure in most cases. For lower intensities, this transport can be done without space charge compensation. However, if space charge is not negligible, the positive charge of the ion beam will attract electrons, which will compensate the space charge, at least partially. The final degree of Space Charge Compensation (SCC) will depend on different properties, like the ratio of generation rate of secondary particles and their loss rate, or the fact whether the ion beam is pulsed or continuous. In sections of the beam line, where the ion beam is drifting, a pure electrostatic plasma will develop, whereas in magnetic elements, these space charge compensating electrons become magnetized. The transport section will provide a series of different plasma conditions with different properties. Different measurement tools to investigate the degree of space charge compensation will be described, as well as computational methods for the simulation of ion beams with partial space charge compensation
Energy Technology Data Exchange (ETDEWEB)
Milant' ev, V. P., E-mail: vmilantiev@sci.pfu.edu.ru; Castillo, A. J., E-mail: vmilant@mail.ru [Peoples' Friendship University of Russia (Russian Federation)
2013-04-15
Averaged relativistic equations of motion of a charged particle in the field of intense electromagnetic radiation have been obtained in the geometrical optics approximation using the Bogoliubov method. Constraints are determined under which these equations are valid. Oscillating additions to the smoothed dynamical variables of the particle have been found; they are reduced to known expressions in the case of the circularly and linearly polarized plane waves. It has been shown that the expressions for the averaged relativistic force in both cases contain new additional small terms weakening its action. The known difference between the expressions for the ponderomotive force in the cases of circularly and linearly polarized waves has been confirmed.
International Nuclear Information System (INIS)
Swanekamp, S. B.; Schumer, J. W.
2007-01-01
In Phys Plasmas 13, 073101 (2006), the drop in the space-charge-limited (SCL) current for a beam injected into a space with an open boundary is analyzed with an electromagnetic particle-in-cell code. The authors explained the power loss observed at the open boundary as the loss of electromagnetic radiation created from the deceleration of electrons in the gap, and they developed an effective voltage theory to predict the drop in the SCL current observed in the simulations. In this Comment, we show that, provided the current remains below the SCL value, the electric and magnetic fields are constant in time so that power loss from the open boundary is a dc phenomenon with no rf power leaving through the boundary. We show that the electric and magnetic fields are static in time and static fields DO NOT RADIATE. Instead, the electron beam charges the collector plate, which causes a real electrostatic electric field to develop. The electron energy loss is not due to radiation but rather to the work done by this electrostatic field on the electrons as they move across the gap. This is precisely the energy dissipated in the matched resistance across the open boundary, which is a consequence of the boundary condition. Furthermore, since a real electrostatic potential develops, the voltage drop is real and there is no need to call the voltage drop an effective voltage
Progress of Space Charge Research on Oil-Paper Insulation Using Pulsed Electroacoustic Techniques
Directory of Open Access Journals (Sweden)
Chao Tang
2016-01-01
Full Text Available This paper focuses on the space charge behavior in oil-paper insulation systems used in power transformers. It begins with the importance of understanding the space charge behavior in oil-paper insulation systems, followed by the introduction of the pulsed electrostatic technique (PEA. After that, the research progress on the space charge behavior of oil-paper insulation during the recent twenty years is critically reviewed. Some important aspects such as the environmental conditions and the acoustic wave recovery need to be addressed to acquire more accurate space charge measurement results. Some breakthroughs on the space charge behavior of oil-paper insulation materials by the research team at the University of Southampton are presented. Finally, future work on space charge measurement of oil-paper insulation materials is proposed.
Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge
International Nuclear Information System (INIS)
Paret, Stefan
2010-01-01
A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)
Equivalent circuit modeling of space charge dominated magnetically insulated transmission lines
Energy Technology Data Exchange (ETDEWEB)
Hiraoka, Kazuki; Nakajima, Mitsuo; Horioka, Kazuhiko
1997-12-31
A new equivalent circuit model for space charge dominated MITLs (Magnetically Insulated Transmission Lines) was developed. MITLs under high power operation are dominated with space charge current flowing between anode and cathode. Conventional equivalent circuit model does not account for space charge effects on power flow. The model was modified to discuss the power transportation through the high power MITLs. With this model, it is possible to estimate the effects of space charge current on the power flow efficiency, without using complicated particle code simulations. (author). 3 figs., 3 refs.
Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge
Energy Technology Data Exchange (ETDEWEB)
Paret, Stefan
2010-02-22
A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)
International Nuclear Information System (INIS)
Bosanac, Slobodan Danko
2016-01-01
This book is devoted to theoretical methods used in the extreme circumstances of very strong electromagnetic fields. The development of high power lasers, ultrafast processes, manipulation of electromagnetic fields and the use of very fast charged particles interacting with other charges requires an adequate theoretical description. Because of the very strong electromagnetic field, traditional theoretical approaches, which have primarily a perturbative character, have to be replaced by descriptions going beyond them. In the book an extension of the semi-classical radiation theory and classical dynamics for particles is performed to analyze single charged atoms and dipoles submitted to electromagnetic pulses. Special attention is given to the important problem of field reaction and controlling dynamics of charges by an electromagnetic field.
Structure resonances due to space charge in periodic focusing channels
Li, Chao; Jameson, R. A.
2018-02-01
The Vlasov-Poisson model is one of the most effective methods to study the space charge dominated beam evolution self-consistently in a periodic focusing channel. Since the approach to get the solution with this model is not trivial, previous studies are limited in degenerated conditions, either in smoothed channel (constant focusing) [I. Hofmann, Phys. Rev. E 57, 4713 (1998)] or in alternating gradient focusing channel with equal initial beam emittance condition in the degrees of freedom [I. Hofmann et al., Part. Accel. 13, 145 (1983); Chao Li et al., THOBA02, IPAC2016]. To establish a basis, we intentionally limit this article to the study of the pure transverse periodic focusing lattice with arbitrary initial beam condition, and the same lattice structure in both degrees of freedom, but with possibility of different focusing strengths. This will show the extension of the existing work. The full Hamiltonian is invoked for a pure transverse focusing lattice in various initial beam conditions, revealing different mode structure and additional modes beyond those of the degenerated cases. Application of the extended method to realistic lattices (including longitudinal accelerating elements) and further details will then reveal many new insights, and will be presented in later work.
Relativistic space-charge-limited current for massive Dirac fermions
Ang, Y. S.; Zubair, M.; Ang, L. K.
2017-04-01
A theory of relativistic space-charge-limited current (SCLC) is formulated to determine the SCLC scaling, J ∝Vα/Lβ , for a finite band-gap Dirac material of length L biased under a voltage V . In one-dimensional (1D) bulk geometry, our model allows (α ,β ) to vary from (2,3) for the nonrelativistic model in traditional solids to (3/2,2) for the ultrarelativistic model of massless Dirac fermions. For 2D thin-film geometry we obtain α =β , which varies between 2 and 3/2, respectively, at the nonrelativistic and ultrarelativistic limits. We further provide rigorous proof based on a Green's-function approach that for a uniform SCLC model described by carrier-density-dependent mobility, the scaling relations of the 1D bulk model can be directly mapped into the case of 2D thin film for any contact geometries. Our simplified approach provides a convenient tool to obtain the 2D thin-film SCLC scaling relations without the need of explicitly solving the complicated 2D problems. Finally, this work clarifies the inconsistency in using the traditional SCLC models to explain the experimental measurement of a 2D Dirac semiconductor. We conclude that the voltage scaling 3 /2 <α <2 is a distinct signature of massive Dirac fermions in a Dirac semiconductor and is in agreement with experimental SCLC measurements in MoS2.
Space-charge-limited currents in electron-irradiated dielectrics
International Nuclear Information System (INIS)
Nunes de Oliveira, L.; Gross, B.
1975-01-01
This paper develops the theory of steady-state currents generated in a dielectric placed between positively or negatively biased electrodes and irradiated with a partially penetrating electron beam. The dielectric is divided into an irradiated region (IR), which extends from the electrode of incidence to the extrapolated range of the beam, and a nonirradiated region (NIR). In the IR the primary beam generates an electron-hole plasma. Its end plane acts as a virtual electrode embedded in the dielectric. Currents are space-charge limited in the NIR and Ohmic in the IR which is characterized by a uniform radiation-induced conductivity. Depending on the polarity of the electrode bias, electrons or holes are drawn from the IR into the NIR. The theory correctly predicts an apparent threshold effect for the inset of steady-state currents: the current amplitudes remain small as long as the electron range is smaller than half the sample thickness, and increase strongly only afterwards. Calculated current curves for different beam energies are in satisfactory agreement with experimental results. The role of the electron beam as a virtual electrode is discussed
A modified space charge routine for LINAC beam dynamics codes
International Nuclear Information System (INIS)
Valero, S.; Lapostolle, P.; Lombardi, A.M.; Tanke, E.; Warner, D.
1994-01-01
In 1991 a space charge calculation for bunched beams with three-dimensional ellipsoidal symmetry was proposed for the PARMILA code, replacing the usual SCHEFF routines: it removes the cylindrical symmetry needed for the Fast Fourier Transform method and avoids the point to point interaction computation, where the number of simulation points is limited. This routine has now been improved with the introduction of two (or more) ellipsoids, giving a good representation of actual, pear-shaped bunches (unlike the 3-D ellipsoidal assumption). The ellipsoidal density distributions are computed with a new method, avoiding the difficulty caused by statistical effects, encountered near the centre (the axis in 2-D problems) by the previous method. It also provides a check of the ellipsoidal symmetry for each part of the distribution. Finally, the Fourier analysis reported in 1991 has been replaced by a very convenient Hermite expansion, which gives a simple but accurate representation of practical distributions. Introduced in the new, versatile beam dynamics code, DYNAC, it should provide a good tool for the study of the effects of the various parameters responsible for the halo formation in high intensity linacs. (authors). 11 refs
International Nuclear Information System (INIS)
Dubois, Daniel M.
2000-01-01
This paper is a continuation of our preceding paper dealing with computational derivation of the Klein-Gordon quantum relativist equation and the Schroedinger quantum equation with forward and backward space-time shifts. The first part introduces forward and backward derivatives for discrete and continuous systems. Generalized complex discrete and continuous derivatives are deduced. The second part deduces the Klein-Gordon equation from the space-time complex continuous derivatives. These derivatives take into account forward-backward space-time shifts related to an internal phase velocity u. The internal group velocity v is related to the speed of light u.v=c 2 and to the external group and phase velocities u.v=v g .v p . Without time shift, the Schroedinger equation is deduced, with a supplementary term, which could represent a reference potential. The third part deduces the Quantum Relativist Klein-Gordon equation for a particle in an electromagnetic field
Maximizing Ion Current by Space Charge Neutralization using Negative Ions and Dust Particles
International Nuclear Information System (INIS)
Smirnov, A.; Raitses, Y.; Fisch, N.J.
2005-01-01
Ion current extracted from an ion source (ion thruster) can be increased above the Child-Langmuir limit if the ion space charge is neutralized. Similarly, the limiting kinetic energy density of the plasma flow in a Hall thruster might be exceeded if additional mechanisms of space charge neutralization are introduced. Space charge neutralization with high-mass negative ions or negatively charged dust particles seems, in principle, promising for the development of a high current or high energy density source of positive light ions. Several space charge neutralization schemes that employ heavy negatively charged particles are considered. It is shown that the proposed neutralization schemes can lead, at best, only to a moderate but nonetheless possibly important increase of the ion current in the ion thruster and the thrust density in the Hall thruster
Directory of Open Access Journals (Sweden)
Ivan V. Bazarov
2008-10-01
Full Text Available We present a comparison between space charge calculations and direct measurements of the transverse phase space of space charge dominated electron bunches from a high voltage dc photoemission gun followed by an emittance compensation solenoid magnet. The measurements were performed using a double-slit emittance measurement system over a range of bunch charge and solenoid current values. The data are compared with detailed simulations using the 3D space charge codes GPT and Parmela3D. The initial particle distributions were generated from measured transverse and temporal laser beam profiles at the photocathode. The beam brightness as a function of beam fraction is calculated for the measured phase space maps and found to approach within a factor of 2 the theoretical maximum set by the thermal energy and the accelerating field at the photocathode.
Design of achromatic bending systems in the presence of space charge
International Nuclear Information System (INIS)
Jason, A.J.; Svaton, E.M.; Blind, B.; Heighway, E.A.
1987-01-01
The usual conditions for achromaticity of a dispersive system are shown to be inadequate when space-charge effects are included. Using a matrix formulation describing linear space-charge forces, we give generalized criteria necessary for a system to be achromatic. Additionally, these conditions are necessary for conservation of transverse emittances. An example of such a system is given
Design of achromatic bending systems in the presence of space charge
International Nuclear Information System (INIS)
Jason, A.J.; Svaton, E.M.; Blind, B.; Heighway, E.A.
1987-01-01
The usual conditions for achromaticity of a dispersive system are shown to be inadequate when space-charge effects are included. Using a matrix formulation describing linear space-charge forces, the authors give generalized criteria necessary for a system to be achromatic. Additionally, these conditions are necessary for conservation of transverse emittances. An example of such a system is given
Electro-Optical Sensing Apparatus and Method for Characterizing Free-Space Electromagnetic Radiation
Zhang, Xi-Cheng; Libelo, Louis Francis; Wu, Qi
1999-09-14
Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric field and a laser beam in an electro-optic crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field--optical beam interaction length, thereby making imaging applications practical.
Wigner functions for nonparaxial, arbitrarily polarized electromagnetic wave fields in free space.
Alonso, Miguel A
2004-11-01
New representations are defined for describing electromagnetic wave fields in free space exactly in terms of rays for any wavelength, level of coherence or polarization, and numerical aperture, as long as there are no evanescent components. These representations correspond to tensors assigned to each ray such that the electric and magnetic energy densities, the Poynting vector, and the polarization properties of the field correspond to simple integrals involving these tensors for the rays that go through the specified point. For partially coherent fields, the ray-based approach provided by the new representations can reduce dramatically the computation times for the physical properties mentioned earlier.
Effect of the space charge layer on pre-transition corrosion rate of Zr alloys
International Nuclear Information System (INIS)
Nanikawa, S.; Etoh, Y.
1998-01-01
The pre- and post-transition oxide films formed in steam at 673 K were investigated by an AC impedance method. The results showed that the space charge layer was present in the pre-transition oxide film and it was absent in the post-transition oxide film. The oxidation kinetics was simulated by oxygen diffusion in the space charge layer. Cubic or one-fourth power law was explained by the effect of the space charge layer. Supposing that the space charge layer formed the potential difference through the oxide film by 0.7 V, calculated oxidation kinetics agreed with the experimental one before transition. This potential difference corresponded to the measured value by AC impedance method within the experimental error. Shadow effect could be explained by this simulation supposing the disappearance of the space charge layer due to the formation of a negative electric field by β-rays. (author)
arXiv Electromagnetic dipole moments of charged baryons with bent crystals at the LHC
Bagli, E.; Cavoto, G.; Guidi, V.; Henry, L.; Marangotto, D.; Martinez Vidal, F.; Mazzolari, A.; Merli, A.; Neri, N.; Ruiz Vidal, J.
2017-12-05
We propose a unique program of measurements of electric and magnetic dipole moments of charm, beauty and strange charged baryons at the LHC, based on the phenomenon of spin precession of channeled particles in bent crystals. Studies of crystal channeling and spin precession of positively- and negatively-charged particles are presented, along with feasibility studies and expected sensitivities for the proposed experiment using a layout based on the LHCb detector.
Electromagnetic dipole moments of charged baryons with bent crystals at the LHC
Energy Technology Data Exchange (ETDEWEB)
Bagli, E.; Bandiera, L.; Guidi, V.; Mazzolari, A. [Universita di Ferrara, Ferrara (Italy); INFN, Sezione di Ferrara (Italy); Cavoto, G. [' ' Sapienza' ' Universita di Roma, Rome (Italy); INFN, Sezione di Roma (Italy); Henry, L.; Martinez Vidal, F.; Ruiz Vidal, J. [IFIC, Universitat de Valencia-CSIC, Valencia (Spain); Marangotto, D. [Universita di Milano, Milan (Italy); INFN, Sezione di Milano (Italy); Merli, A.; Neri, N. [Universita di Milano, Milan (Italy); CERN, Geneva (Switzerland); INFN, Sezione di Milano (Italy)
2017-12-15
We propose a unique program of measurements of electric and magnetic dipole moments of charm, beauty and strange charged baryons at the LHC, based on the phenomenon of spin precession of channeled particles in bent crystals. Studies of crystal channeling and spin precession of positively- and negatively-charged particles are presented, along with feasibility studies and expected sensitivities for the proposed experiment using a layout based on the LHCb detector. (orig.)
An SU(3)xU(1) theory of weak-electromagnetic interactions with charged boson mixing
International Nuclear Information System (INIS)
Singer, M.
1978-01-01
An SU(3)xU(1) gauge theory of weak electromagnetic interactions is proposed in which the charged bosons mix with each other. The model naturally ensures e-μ and quark-lepton universality in couplings, and the charged boson mixing permits an equal number of leptons and quark flavours. There are no new stable leptons. All the fermions are placed in triplets and singlets and the theory is vector-like and hence free of anomalies. In addition one of the charged bosons can have a mass less than 43 GeV. Discrete symmetries and specific choices for Higgs fields are postulated to obtain the appropriate boson and fermion masses. Calculations for the decay of the tau particle, which is described as a heavy electron, are given. Multimuon events are discussed as are neutrino neutral currents. Calculations are also given for testing asymmetries in e-hadron scattering due to weak electron neutral currents along with other phenomenology of the model
Energy Technology Data Exchange (ETDEWEB)
Bandiera, Laura; Bagli, Enrico; Guidi, Vincenzo [INFN Sezione di Ferrara and Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Saragat 1, 44121 Ferrara (Italy); Tikhomirov, Victor V. [Research Institute for Nuclear Problems, Belarusian State University, Minsk (Belarus)
2015-07-15
The analytical theories of coherent bremsstrahlung and channeling radiation well describe the process of radiation generation in crystals under some special cases. However, the treatment of complex situations requires the usage of a more general approach. In this report we present a C++ routine, named RADCHARM++, to compute the electromagnetic radiation emitted by electrons and positrons in crystals and complex structures. In the RADCHARM++ routine, the model for the computation of e.m. radiation generation is based on the direct integration of the quasiclassical formula of Baier and Katkov. This approach allows one taking into account real trajectories, and thereby the contribution of incoherent scattering. Such contribution can be very important in many cases, for instance for electron channeling. The generality of the Baier–Katkov operator method permits one to simulate the electromagnetic radiation emitted by electrons/positrons in very different cases, e.g., in straight, bent and periodically bent crystals, and for different beam energy ranges, from sub-GeV to TeV and above. The RADCHARM++ routine has been implemented in the Monte Carlo code DYNECHARM++, which solves the classical equation of motion of charged particles traveling through a crystal under the continuum potential approximation. The code has proved to reproduce the results of experiments performed at the MAinzer MIkrotron (MAMI) with 855 MeV electrons and has been used to predict the radiation spectrum generated by the same electron beam in a bent crystal.
Course Notes: United States Particle Accelerator School Beam Physics with Intense Space-Charge
International Nuclear Information System (INIS)
Barnard, J.J.; Lund, S.M.
2008-01-01
The purpose of this course is to provide a comprehensive introduction to the physics of beams with intense space charge. This course is suitable for graduate students and researchers interested in accelerator systems that require sufficient high intensity where mutual particle interactions in the beam can no longer be neglected. This course is intended to give the student a broad overview of the dynamics of beams with strong space charge. The emphasis is on theoretical and analytical methods of describing the acceleration and transport of beams. Some aspects of numerical and experimental methods will also be covered. Students will become familiar with standard methods employed to understand the transverse and longitudinal evolution of beams with strong space charge. The material covered will provide a foundation to design practical architectures. In this course, we will introduce you to the physics of intense charged particle beams, focusing on the role of space charge. The topics include: particle equations of motion, the paraxial ray equation, and the Vlasov equation; 4-D and 2-D equilibrium distribution functions (such as the Kapchinskij-Vladimirskij, thermal equilibrium, and Neuffer distributions), reduced moment and envelope equation formulations of beam evolution; transport limits and focusing methods; the concept of emittance and the calculation of its growth from mismatches in beam envelope and from space-charge non-uniformities using system conservation constraints; the role of space-charge in producing beam halos; longitudinal space-charge effects including small amplitude and rarefaction waves; stable and unstable oscillation modes of beams (including envelope and kinetic modes); the role of space charge in the injector; and algorithms to calculate space-charge effects in particle codes. Examples of intense beams will be given primarily from the ion and proton accelerator communities with applications from, for example, heavy-ion fusion, spallation
Effect of the space-charge force on tracking at low energy
International Nuclear Information System (INIS)
Furman, M.A.
1987-01-01
The authors present tracking results for the SSC's Low Energy Booster at injection energy, including the effect of the space-charge force. The bunches are assumed to be gaussian with elliptical cross-section. Magnet errors and sextupoles are not included, but an RF cavity is. The authors compare the phase space with and without synchrotron oscillations, with and without space-charge. The effective emittance is not significantly altered. They also present results on tune shifts with amplitude
Charge symmetry of electron wave functions in a quantized electromagnetic wave field
Energy Technology Data Exchange (ETDEWEB)
Fedorov, M V [AN SSSR, Moscow. Fizicheskij Inst.
1975-01-01
An attempt to clear up the reasons of the electron charge symmetry violation in the quantum wave field was made in this article. For this purpose the connection between the Dirac equation and the electron wave functions in the external field with the exact equation of quantum electrodynamics is established. Attention is paid to the fact that a number of equations for single-electron wave functions can be used in the framework of the same assumptions. It permits the construction of the charge-symmetric solutions in particular.
Equations of motion for a radiating charged particle in electromagnetic fields on curved spacetime
International Nuclear Information System (INIS)
Prasanna, A.R.
1982-11-01
In this note we present the equations of motion for a radiating charged particle in the framework of general relativity and give a formal procedure of solving the system numerically using iterations, when the motion is confined to the equatorial plane. (author)
Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder
Galatà, A.; Patti, G.; Celona, L.; Mascali, D.; Neri, L.; Torrisi, G.
2016-02-01
The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which the selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself.
Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder
International Nuclear Information System (INIS)
Galatà, A.; Patti, G.; Celona, L.; Mascali, D.; Neri, L.; Torrisi, G.
2016-01-01
The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which the selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself
Motion of a Charged Particle in a Constant and Uniform Electromagnetic Field
Ladino, L. A.; Rondón, S. H.; Orduz, P.
2015-01-01
This paper focuses on the use of software developed by the authors that allows the visualization of the motion of a charged particle under the influence of magnetic and electric fields in 3D, at a level suitable for introductory physics courses. The software offers the possibility of studying a great number of physical situations that can…
Space Charge Effects for the ERL Prototype Injector Line at Daresbury Laboratory
Muratori, Bruno; Owen, Hywel; de Loos, Marieke; van der Geer, Bas
2005-01-01
Daresbury Laboratory is currently building an Energy Recovery Linac Prototype (ERLP) that will operate at a beam energy of 35 MeV. In this paper we examine the space charge effects on the beam dynamics in the ERLP injector line. A Gaussian particle distribution is tracked with GPT (General Particle Tracer) through the injection line to the main linac to calculate the effect of 3Dspace charge in the dipoles. The nominal beam energy in the injection line is 8.3 MeV and the bunch charge 80 pC. The effects of space charge on the transverse and longitudinal emittance are studied for various electron beam parameter settings.
Preliminary feasibility assessment for Earth-to-space electromagnetic (Railgun) launchers
Rice, E. E.; Miller, L. A.; Earhart, R. W.
1982-01-01
An Earth to space electromagnetic (railgun) launcher (ESRL) for launching material into space was studied. Potential ESRL applications were identified and initially assessed to formulate preliminary system requirements. The potential applications included nuclear waste disposal in space, Earth orbital applications, deep space probe launchers, atmospheric research, and boost of chemical rockets. The ESRL system concept consisted of two separate railgun launcher tubes (one at 20 deg from the horizontal for Earth orbital missions, the other vertical for solar system escape disposal missions) powered by a common power plant. Each 2040 m launcher tube is surrounded by 10,200 homopolar generator/inductor units to transmit the power to the walls. Projectile masses are 6500 kg for Earth orbital missions and 2055 kg for nuclear waste disposal missions. For the Earth orbital missions, the projectile requires a propulsion system, leaving an estimated payload mass of 650 kg. For the nuclear waste disposal in space mission, the high level waste mass was estimated at 250 kg. This preliminary assessment included technical, environmental, and economic analyses.
Xu, Guangwei
2018-02-22
Charge transport governs the operation and performance of organic diodes. Illuminating the charge-transfer/transport processes across the interfaces and the bulk organic semiconductors is at the focus of intensive investigations. Traditionally, the charge transport properties of organic diodes are usually characterized by probing the current–voltage (I–V) curves of the devices. However, to unveil the landscape of the underlying potential/charge distribution, which essentially determines the I–V characteristics, still represents a major challenge. Here, the electrical potential distribution in planar organic diodes is investigated by using the scanning Kelvin probe force microscopy technique, a method that can clearly separate the contact and bulk regimes of charge transport. Interestingly, by applying to devices based on novel, high mobility organic materials, the space-charge-limited-current-like I–V curves, which are previously believed to be a result of the bulk transport, are surprisingly but unambiguously demonstrated to be caused by contact-limited conduction. A model accounting is developed for the transport properties of both the two metal/organic interfaces and the bulk. The results indicate that pure interface-dominated transport can indeed give rise to I–V curves similar to those caused by bulk transport. These findings provide a new insight into the charge injection and transport processes in organic diodes.
Energy Technology Data Exchange (ETDEWEB)
Medeiros Ritter, Oswaldo de
1991-10-01
We discuss the Lie method and apply it to differential equations obtaining their symmetries. We also discuss methods of how to obtain first integrals from these symmetries. We apply these methods to some interesting physical problems, all of them involving charged particles in electromagnetic fields. (author). 77 refs.
Charged fluid distribution in higher dimensional spheroidal space-time
Indian Academy of Sciences (India)
associated 3-spaces obtained as hypersurfaces t = constant, 3-spheroids, are suit- ... pressure. Considering the Vaidya–Tikekar [12] spheroidal geometry, ... a relativistic star in hydrostatic equilibrium having the spheroidal geometry of the .... K = 1, the spheroidal 3-space degenerates into a flat 3-space and when K = 0 it.
International Nuclear Information System (INIS)
Kumar, Raghwendra; Biswas, Debabrata
2008-01-01
For a nonrelativistic electron beam propagating in a cylindrical drift tube, it is shown that the limiting current density does not saturate to the electrostatic one-dimensional (1D) estimate with increasing beam radius. Fully electromagnetic particle-in-cell (PIC) simulation studies show that beyond a critical aspect ratio, the limiting current density is lower than the 1D electrostatic prediction. The lowering in the limiting current density is found to be due to the transition from the space charge limited to magnetically limited flow. An adaptation of Alfven's single particle trajectory method is used to estimate the magnetically limited current as well as the critical radius beyond which the flow is magnetically limited in a drift tube. The predictions are found to be in close agreement with PIC simulations
Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films
Hu, Weijin
2014-11-12
We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current is revealed to be the dominant leakage mechanism in such organic ferroelectric devices, and electrostatic interactions due to space charges lead to the emergence of anomalous ferroelectric loops. The reliable control of ferroelectric switching in P(VDF-TrEE) copolymers opens doors toward engineering advanced organic memories with tailored switching characteristics.
On Beam Matching and the Space-Charge Effect in protoDUNE-SP
Mandalia, Jesal Paresh
2017-01-01
In this project simulations using LArSoft have been analysed in particular looking at how the space-charge effect will affect the matching of particle tracks from the beam line monitor to the TPC and the TPC's performance measuring $\\frac{dE}{dx}$ in protoDUNE-SP. The analysis here provides some preliminary calibrations for protoDUNE-SP to account for the impact the space charge effect will have. Many areas of pion cross section analysis will be affected by the space charge effect so it is vital for a calibration to be developed.
Space Charge Compensation in the Linac4 Low Energy Beam Transport Line with Negative Hydrogen Ions
Valerio-Lizarraga, C; Leon-Monzon, I; Lettry, J; Midttun, O; Scrivens, R
2014-01-01
The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Tranport (LEBT) using the package IBSimu1, which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H- beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.
Space charge and magnet error simulations for the SNS accumulator ring
International Nuclear Information System (INIS)
Beebe-Wang, J.; Fedotov, A.V.; Wei, J.; Machida, S.
2000-01-01
The effects of space charge forces and magnet errors in the beam of the Spallation Neutron Source (SNS) accumulator ring are investigated. In this paper, the focus is on the emittance growth and halo/tail formation in the beam due to space charge with and without magnet errors. The beam properties of different particle distributions resulting from various injection painting schemes are investigated. Different working points in the design of SNS accumulator ring lattice are compared. The simulations in close-to-resonance condition in the presence of space charge and magnet errors are presented. (author)
Space-charge effects of the proportional counters in a multiple-ionization chamber
International Nuclear Information System (INIS)
Mang, M.
1993-01-01
At the ALADIN spectrometer of the GSI in october 1991 for the first time the new multiple ionization chamber was applied, in the two anode planes of which are additional multiwire-proportional counters. The proportional counters are required in order to make the detection of light fragments (Z 4 gold projectiles per second by these positive space charges the homogeneous electric field of the MUSIC is disturbed. This effect is especially strong in the beam plane. As consequence of the space charge additionally electrons are focused on the proportional counter so that their amplitudes in dependence on the beam intensity increase up to the 2.5-fold. Furthermore the y coordinate is falsified, because the electrons are diverted to the medium plane. On the measurement of the x coordinate this diversion has with maximally 0.1% only a small influence. These space-charge effects can be qualitatively described by a schematic model, which assumes a stationary positive space charge. Additionally for the proportional counters, which are not in the beam plane, their resolution was determined. In these counters the space-charge effects are small, because essentially fewer particles are registrated than in the medium MWPC's. By this charges of fragments with Z<10 could be separated. The charge resolution amounted at lithium 0.8 charge units. The position resolution of the proportional counters in y direction was determined to less than 8 mm. The detection probability of the fragments amounts for lithium 90% and from boron all fragments are detected
Directory of Open Access Journals (Sweden)
Steven M. Lund
2009-11-01
Full Text Available Self-consistent Vlasov-Poisson simulations of beams with high space-charge intensity often require specification of initial phase-space distributions that reflect properties of a beam that is well adapted to the transport channel—both in terms of low-order rms (envelope properties as well as the higher-order phase-space structure. Here, we first review broad classes of kinetic distributions commonly in use as initial Vlasov distributions in simulations of unbunched or weakly bunched beams with intense space-charge fields including the following: the Kapchinskij-Vladimirskij (KV equilibrium, continuous-focusing equilibria with specific detailed examples, and various nonequilibrium distributions, such as the semi-Gaussian distribution and distributions formed from specified functions of linear-field Courant-Snyder invariants. Important practical details necessary to specify these distributions in terms of standard accelerator inputs are presented in a unified format. Building on this presentation, a new class of approximate initial kinetic distributions are constructed using transformations that preserve linear focusing, single-particle Courant-Snyder invariants to map initial continuous-focusing equilibrium distributions to a form more appropriate for noncontinuous focusing channels. Self-consistent particle-in-cell simulations are employed to show that the approximate initial distributions generated in this manner are better adapted to the focusing channels for beams with high space-charge intensity. This improved capability enables simulations that more precisely probe intrinsic stability properties and machine performance.
Coherent and Semiclassical States of a Charged Particle in Electromagnetic Fields
Pereira, A. S.
2018-03-01
In the present article, we extend our study (Bagrov et al., Braz. J. Phys. 45, 369, 2015) of generalized coherent states (GCS) of a one-dimensional particle considering such important physical system as a three-dimensional charged particle in electric and magnetic fields. Constructing GCS in a many-dimensional case, we meet technical complications that make the consideration nontrivial and instructive. The GCS of the system under consideration are constructed. We study the properties of this GCS such as completeness relations, minimization of uncertainty relations, and so on. We point out which family of the obtained GCS of a charged particle in a magnetic field is related to the CS constructed first by Malkin and Man'ko. We obtain conditions under which some of the GCS can be considered as semiclassical states (SS).
Coherent and Semiclassical States of a Charged Particle in Electromagnetic Fields
Pereira, A. S.
2018-06-01
In the present article, we extend our study (Bagrov et al., Braz. J. Phys. 45, 369, 2015) of generalized coherent states (GCS) of a one-dimensional particle considering such important physical system as a three-dimensional charged particle in electric and magnetic fields. Constructing GCS in a many-dimensional case, we meet technical complications that make the consideration nontrivial and instructive. The GCS of the system under consideration are constructed. We study the properties of this GCS such as completeness relations, minimization of uncertainty relations, and so on. We point out which family of the obtained GCS of a charged particle in a magnetic field is related to the CS constructed first by Malkin and Man'ko. We obtain conditions under which some of the GCS can be considered as semiclassical states (SS).
International Nuclear Information System (INIS)
Zheng, Feihu; An, Zhenlian; Zhang, Yewen; Liu, Chuandong; Lin, Chen; Lei, Qingquan
2013-01-01
The thermal pulse method is a powerful method to measure space charge and polarization distributions in thin dielectric films, but a complicated calibration procedure is necessary to obtain the real distribution. In addition, charge dynamic behaviour under an applied electric field cannot be observed by the classical thermal pulse method. In this work, an improved thermal pulse measuring system with a supplemental circuit for applying high voltage is proposed to realize the mapping of charge distribution in thin dielectric films under an applied field. The influence of the modified measuring system on the amplitude and phase of the thermal pulse response current are evaluated. Based on the new measuring system, an easy calibration approach is presented with some practical examples. The newly developed system can observe space charge evolution under an applied field, which would be very helpful in understanding space charge behaviour in thin films. (paper)
Gravitational collapse in higher-dimensional charged-Vaidya space ...
Indian Academy of Sciences (India)
time. We show that singularities arising in a charged null fluid in higher dimension are always naked violating ... of matter is one of the most active field of research in the contemporary general relativity. ... The main open issue ..... [3] A Papapetrou, in A random walk in relativity and cosmology edited by N Dadhich, J K Rao,.
Ion trajectories calculation in a three dimensional beam subjected to a space charge
International Nuclear Information System (INIS)
Tauth, T.
1978-04-01
Physical and geometrical conditions allowing a first approximation of necessary sizes to numerical integration of the ions movement equations subjected to electrical and magnetic crossed fields and space charge action are investigated here. To take into consideration the effect of the last one, two artifices are put forward: replacing charged particles by equivalent particles in calculating the coulomb force, electrical field calculation produced in different points situated on the beam envelope by the uniform charges distribution [fr
Charged particle spin flip in a storage ring with HF-electromagnetic field
International Nuclear Information System (INIS)
Polunin, A.A.; Shatupov, Yu.M.
1982-01-01
An experiment for revealing a possibility of adiabatic electron spin flip in the VEPP-2M storage ring is described. High frequency longitudinal magnetic field up to 100 Gs at the length of 40 cm and frequency of 7.95 MHz was produced by a spiral of 10 coils supplied from HF-generator with 5 kW power. The control system permitted to vary generator frequency within +-3x10 - 3 f range during 10 - 3 -10 s. Determination of beam polarization degree was exercised by detection of electron elastic scattering inside the bunch. A possibility of changing the polarization sign at preservation of other beam parameters (dimensions, currents, energy, etc.) is of interest in experiments with polarized particles in storage rings. Spin flip can be exercised by effect on the beam of high frequency electromagnetic field, resonance with spin precession frequency around the leading field of the storage ring. The polarized 5 mA beam was produced due to radiation polarization at which electron spins are alinged along the direction of the magnetic field. Processing of the experimental results revealed good correspondence to analytical dependence. The depolarization value at the spin flip did not exceed 10%
Electromagnetic scattering by a polydispersion of small charged cosmic dust particles
Directory of Open Access Journals (Sweden)
M. Kocifaj
2011-09-01
Full Text Available Some recent studies on extended red emissions suggest the presence of very small dust particles in the Universe. The sizes of these particles vary from 1 nm to some tens of nanometers, thus situating them deeply in the Rayleigh region if computations are made for visible or near infrared. The optical response of such particles can be a function of the surface charge. In this study we analyse the effect of surface electric potential on the total optical thickness and scattering phase function of the cosmic dust particles. The results are compared with those obtained for electrically neutral dust.
An Improved Treatment of AC Space Charge Fields in Large Signal Simulation Codes
National Research Council Canada - National Science Library
Dialetis, D; Chernin, D; Antonsen, Jr., T. M; Levush, B
2006-01-01
An accurate representation of the AC space charge electric field is required in order to be able to predict the performance of linear beam tubes, including TWT's and klystrons, using a steady state...
Numerical design of electron guns and space charge limited transport systems
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.
1980-10-01
This paper describes the capabilities and limitations of computer programs used to design electron guns and similarly space-charge limited transport systems. Examples of computer generated plots from several different types of gun problems are included
Cousineau, Sarah M
2005-01-01
Space charge effects are a major contributor to beam halo and emittance growth leading to beam loss in high intensity, low energy accelerators. As future accelerators strive towards unprecedented levels of beam intensity and beam loss control, a more comprehensive understanding of space charge effects is required. A wealth of simulation tools have been developed for modeling beams in linacs and rings, and with the growing availability of high-speed computing systems, computationally expensive problems that were inconceivable a decade ago are now being handled with relative ease. This has opened the field for realistic simulations of space charge effects, including detailed benchmarks with experimental data. A great deal of effort is being focused in this direction, and several recent benchmark studies have produced remarkably successful results. This paper reviews the achievements in space charge benchmarking in the last few years, and discusses the challenges that remain.
Dacuñ a, Javier; Salleo, Alberto
2011-01-01
We have developed and have applied a mobility edge model that takes drift and diffusion currents to characterize the space-charge-limited current in organic semiconductors into account. The numerical solution of the drift-diffusion equation allows
Space charge build-up in XLPE-cable with temperature gradient
DEFF Research Database (Denmark)
Holbøll, Joachim; Henriksen, Mogens; Hjerrild, Jesper
2000-01-01
and temperatures were applied in the 20 - 80°C range with gradients across the insulation of up to 15°C. In this paper, the observed charge phenomena in the bulk and at the interfaces are related to the external conditions, in particular to the temperature gradient. The measured space charge distributions...
International Nuclear Information System (INIS)
Hao Jian; Liao Ruijin; Chen, George
2011-01-01
Dielectric response and space charge behaviour of oil-paper insulation sample with different moisture contents were investigated using the frequency dielectric spectroscopy (FDS) and the pulsed electroacoustic (PEA) technique, respectively. The influence of moisture on the dielectric response and space charge behaviour of oil impregnated paper insulation was analysed. Results show that the moisture has great effect on the FDS and space charge behaviour of oil impregnated paper insulation. In the frequency range of 10 -2 ∼10 6 Hz, the conductivity and the capacitance of oil impregnated paper increases with its moisture content. The space charge distribution of oil-paper sample with lower and higher moisture contents is very different from each other. The higher the moisture concentration of the oil impregnated paper, the easier the negative charge penetration into the insulation paper. There is a significant amount of positive charge accumulated at the paper-paper interface near to the cathode for oilpaper sample with lower moisture content. However, the positive charge appears in the middle layer paper for oil-paper sample with higher moisture content. Due to the high conductivity, the charge trapped in the oil-paper sample with higher moisture content disappears much faster than that in the oil-paper sample with lower moisture content after removing the voltage.
A multigrid based 3D space-charge routine in the tracking code GPT
Pöplau, G.; Rienen, van U.; Loos, de M.J.; Geer, van der S.B.; Berz, M.; Makino, K.
2005-01-01
Fast calculation of3D non-linear space-charge fields is essential for the simulation ofhigh-brightness charged particle beams. We report on our development of a new 3D spacecharge routine in the General Particle Tracer (GPT) code. The model is based on a nonequidistant multigrid Poisson solver that
Multigrid Algorithms for the Fast Calculation of Space-Charge Effects in Accelerator Design
Pöplau, G.; Rienen, van U.; Geer, van der S.B.; Loos, de M.J.
2004-01-01
Numerical prediction of charged particle dynamics in accelerators is essential for the design and understanding of these machines. Methods to calculate the self-fields of the bunch, the so-called space-charge forces, become increasingly important as the demand for high-quality bunches increases. We
Space-charge-limited currents: An E-infinity Cantorian approach
Czech Academy of Sciences Publication Activity Database
Zmeškal, O.; Nešpůrek, Stanislav; Weiter, M.
2007-01-01
Roč. 34, č. 2 (2007), s. 143-158 ISSN 0960-0779 R&D Projects: GA MPO FT-TA/036; GA AV ČR IAA100100622 Institutional research plan: CEZ:AV0Z40500505 Keywords : space charge * fractal * charge injection Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.025, year: 2007
Energy Technology Data Exchange (ETDEWEB)
Hao Jian; Liao Ruijin [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University (China); Chen, George, E-mail: jh210v@ecs.soton.ac.uk [School of Electronics and Computer Science, University of Southampton (United Kingdom)
2011-08-12
Dielectric response and space charge behaviour of oil-paper insulation sample with different moisture contents were investigated using the frequency dielectric spectroscopy (FDS) and the pulsed electroacoustic (PEA) technique, respectively. The influence of moisture on the dielectric response and space charge behaviour of oil impregnated paper insulation was analysed. Results show that the moisture has great effect on the FDS and space charge behaviour of oil impregnated paper insulation. In the frequency range of 10{sup -2}{approx}10{sup 6}Hz, the conductivity and the capacitance of oil impregnated paper increases with its moisture content. The space charge distribution of oil-paper sample with lower and higher moisture contents is very different from each other. The higher the moisture concentration of the oil impregnated paper, the easier the negative charge penetration into the insulation paper. There is a significant amount of positive charge accumulated at the paper-paper interface near to the cathode for oilpaper sample with lower moisture content. However, the positive charge appears in the middle layer paper for oil-paper sample with higher moisture content. Due to the high conductivity, the charge trapped in the oil-paper sample with higher moisture content disappears much faster than that in the oil-paper sample with lower moisture content after removing the voltage.
Benaglia, Andrea; Lecoq, Paul; Wenzel, Hans; Para, Adam
2016-01-01
The performance of hadronic calorimeters will be a key parameter at the next generation of High Energy Physics accelerators. A detector combining fine granularity with excellent timing information would prove beneficial for the reconstruction of both jets and electromagnetic particles with high energy resolution. In this work, the space and time structure of high energy showers is studied by means of a Geant4-based simulation toolkit. In particular, the relevant time scales of the different physics phenomena contributing to the energy loss are investigated. A correlation between the fluctuations of the energy deposition of high energy hadrons and the time development of the showers is observed, which allows for an event-by-event correction to be computed to improve the energy resolution of the calorimeter. These studies are intended to set the basic requirements for the development of a new-concept, total absorption time-imaging calorimeter, which seems now within reach thanks to major technological advanceme...
International Nuclear Information System (INIS)
Sernelius, Bo E
2008-01-01
The energy spectrum of electromagnetic normal modes plays a central role in the theory of the van der Waals and Casimir interaction. Here we study the modes in connection with the van der Waals interaction between two metal half spaces. Neglecting dissipation leads to distinct normal modes with real-valued frequencies. Including dissipation seems to have the effect that these distinct modes move away from the real axis into the complex frequency plane. The summation of the zero-point energies of these modes render a complex-valued result. Using the contour integration, resulting from the use of the generalized argument principle, gives a real-valued and different result. We resolve this contradiction and show that the spectrum of true normal modes forms a continuum with real frequencies
EXPLORING TRANSVERSE BEAM STABILITY IN THE SNS IN THE PRESENCE OF SPACE CHARGE.
Energy Technology Data Exchange (ETDEWEB)
FEDOTOV,A.V.; BLASKIEWICZ,M.; WEI,J.; DANILOV,V.; HOLMES,J.; SHISHLO,A.
2002-06-03
The highest possible intensity in the machine is typically determined by the onset of coherent beam instabilities. Understanding the contribution of various effects to the damping and growth of such instabilities in the regime of strong space charge is thus of crucial importance. In this paper we explore transverse beam stability by numerical simulations using recently implemented models of transverse impedance and three-dimensional space charge. Results are discussed with application to the SNS accumulators.
Theory and Simulation of the Physics of Space Charge Dominated Beams
International Nuclear Information System (INIS)
Haber, Irving
2002-01-01
This report describes modeling of intense electron and ion beams in the space charge dominated regime. Space charge collective modes play an important role in the transport of intense beams over long distances. These modes were first observed in particle-in-cell simulations. The work presented here is closely tied to the University of Maryland Electron Ring (UMER) experiment and has application to accelerators for heavy ion beam fusion
Kaon transverse charge density from space- and timelike data
Mecholsky, N. A.; Meija-Ott, J.; Carmignotto, M.; Horn, T.; Miller, G. A.; Pegg, I. L.
2017-12-01
We used the world data on the kaon form factor to extract the transverse kaon charge density using a dispersion integral of the imaginary part of the kaon form factor in the timelike region. Our analysis includes recent data from e+e- annihiliation measurements extending the kinematic reach of the data into the region of high momentum transfers conjugate to the region of short transverse distances. To calculate the transverse density we created a superset of both timelike and spacelike data and developed an empirical parameterization of the kaon form factor. The spacelike set includes two new data points we extracted from existing cross section data. We estimate the uncertainty on the resulting transverse density to be 5% at b =0.025 fm and significantly better at large distances. New kaon data planned with the 12 GeV Jefferson Lab may have a significant impact on the charge density at distances of b <0.1 fm.
Charged anisotropic star on paraboloidal space-time
Indian Academy of Sciences (India)
dr2 − r2 ( dθ2 + sin2 θdφ2). ,. (1) with the energy–momentum tensor for anisotropic charged fluid,. Tij = diag. ( ρ + E2, pr − E2, pt + E2, pt + E2). ,. (2) where ρ is the energy density, pr is the radial pressure, pt is the tangential pressure and. E is the electric field intensity. These quantities are measured relative to the comoving.
Nonlinear classical theory of electromagnetism
International Nuclear Information System (INIS)
Pisello, D.
1977-01-01
A topological theory of electric charge is given. Einstein's criteria for the completion of classical electromagnetic theory are summarized and their relation to quantum theory and the principle of complementarity is indicated. The inhibiting effect that this principle has had on the development of physical thought is discussed. Developments in the theory of functions on nonlinear spaces provide the conceptual framework required for the completion of electromagnetism. The theory is based on an underlying field which is a continuous mapping of space-time into points on the two-sphere. (author)
Case Studies in Space Charge and Plasma Acceleration of Charged Beams
Bazzani, A; Londrillo, P; Sinigardi, S; Turchetti, G
2014-01-01
Plasma acceleration with electron or proton driver beams is a challenging opportunity for high energy physics. An energy doubling experiment with electron drivers was successfully performed at SLAC and a key experiment AWAKE with proton drivers is on schedule at CERN. Simulations play an important role in choosing the best experimental conditions and in interpreting the results. The Vlasov equation is the theoretical tool to describe the interaction of a driver particle beam or a driver laser pulse with a plasma. Collective effects, such as tune shift and mismatch instabilities, appear in high intensity standard accelerators and are described by the Poisson-Vlasov equation. In the paper we review the Vlasov equation in electrostatic and fully electromagnetic case. The general framework of variational principles is used to derive the equation, the local form of the balance equations and related conservation laws. In the electrostatic case we remind the analytic Kapchinskij-Vladimirskij (K-V) model and we propo...
Electromagnetic modelling of a space-borne far-infrared interferometer
Donohoe, Anthony; O'Sullivan, Créidhe; Murphy, J. Anthony; Bracken, Colm; Savini, Giorgio; Pascale, Enzo; Ade, Peter; Sudiwala, Rashmi; Hornsby, Amber
2016-02-01
In this paper I will describe work done as part of an EU-funded project `Far-infrared space interferometer critical assessment' (FISICA). The aim of the project is to investigate science objectives and technology development required for the next generation THz space interferometer. The THz/FIR is precisely the spectral region where most of the energy from stars, exo-planetary systems and galaxy clusters deep in space is emitted. The atmosphere is almost completely opaque in the wave-band of interest so any observation that requires high quality data must be performed with a space-born instrument. A space-borne far infrared interferometer will be able to answer a variety of crucial astrophysical questions such as how do planets and stars form, what is the energy engine of most galaxies and how common are the molecule building blocks of life. The FISICA team have proposed a novel instrument based on a double Fourier interferometer that is designed to resolve the light from an extended scene, spectrally and spatially. A laboratory prototype spectral-spatial interferometer has been constructed to demonstrate the feasibility of the double-Fourier technique at far infrared wavelengths (0.15 - 1 THz). This demonstrator is being used to investigate and validate important design features and data-processing methods for future instruments. Using electromagnetic modelling techniques several issues related to its operation at long baselines and wavelengths, such as diffraction, have been investigated. These are critical to the design of the concept instrument and the laboratory testbed.
Gravitation and electromagnetism
Apsel, D
1979-01-01
Through an examination of the Bohm-Aharonov experiment, a new theory of gravitation and electromagnetism is proposed. The fundamental assumption of the theory is that the motion of a particle in a combination of gravitational and electromagnetic fields is determined from a variational principle of the form delta integral /sub A//sup B /d tau =0. The form of the physical time is determined from an examination of the Maxwell-Einstein action function. The field and motion equations are formally identical to those of Maxwell-Einstein theory. The theory predicts that even in a field-free region of space, electromagnetic potentials can alter the phase of a wave function and the lifetime of a charged particle. The phase alteration has been observed in the Bohm-Aharonov experiment. There is an indication that the lifetime alteration has shown up in a recent CERN storage ring experiment. Experimental tests are proposed. (11 refs).
Longitudinal and transverse space charge limitations on transport of maximum power beams
International Nuclear Information System (INIS)
Khoe, T.K.; Martin, R.L.
1977-01-01
The maximum transportable beam power is a critical issue in selecting the most favorable approach to generating ignition pulses for inertial fusion with high energy accelerators. Maschke and Courant have put forward expressions for the limits on transport power for quadrupole and solenoidal channels. Included in a more general way is the self consistent effect of space charge defocusing on the power limit. The results show that no limits on transmitted power exist in principal. In general, quadrupole transport magnets appear superior to solenoids except for transport of very low energy and highly charged particles. Longitudinal space charge effects are very significant for transport of intense beams
Metal nanoparticle mediated space charge and its optical control in an organic hole-only device
Energy Technology Data Exchange (ETDEWEB)
Ligorio, G.; Nardi, M. V. [Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Brook-Taylor Str. 6, 12489 Berlin (Germany); Steyrleuthner, R.; Neher, D. [Institute of Physics and Astronomy, Universität Potsdam, Karl-Liebknecht Str. 24, 14476 Potsdam (Germany); Ihiawakrim, D. [Institut de Physique et de Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, 67034 Strasbourg, Cedex2 (France); Crespo-Monteiro, N.; Brinkmann, M. [Institut Charles Sadron CNRS, 23 rue du Loess, 67034 Strasbourg (France); Koch, N., E-mail: norbert.koch@physik.hu-berlin.de [Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Brook-Taylor Str. 6, 12489 Berlin (Germany); Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Erneuerbare Energien, Albert-Einstein Str. 15, 12489 Berlin (Germany)
2016-04-11
We reveal the role of localized space charges in hole-only devices based on an organic semiconductor with embedded metal nanoparticles (MNPs). MNPs act as deep traps for holes and reduce the current density compared to a device without MNPs by a factor of 10{sup 4} due to the build-up of localized space charge. Dynamic MNPs charged neutrality can be realized during operation by electron transfer from excitons created in the organic matrix, enabling light sensing independent of device bias. In contrast to the previous speculations, electrical bistability in such devices was not observed.
Metal nanoparticle mediated space charge and its optical control in an organic hole-only device
International Nuclear Information System (INIS)
Ligorio, G.; Nardi, M. V.; Steyrleuthner, R.; Neher, D.; Ihiawakrim, D.; Crespo-Monteiro, N.; Brinkmann, M.; Koch, N.
2016-01-01
We reveal the role of localized space charges in hole-only devices based on an organic semiconductor with embedded metal nanoparticles (MNPs). MNPs act as deep traps for holes and reduce the current density compared to a device without MNPs by a factor of 10 4 due to the build-up of localized space charge. Dynamic MNPs charged neutrality can be realized during operation by electron transfer from excitons created in the organic matrix, enabling light sensing independent of device bias. In contrast to the previous speculations, electrical bistability in such devices was not observed.
Metal nanoparticle mediated space charge and its optical control in an organic hole-only device
Ligorio, G.; Nardi, M. V.; Steyrleuthner, Robert; Ihiawakrim, D.; Crespo-Monteiro, N.; Brinkmann, M.; Neher, D.; Koch, N.
2017-01-01
We reveal the role of localized space charges in hole-only devices based on an organic semiconductor with embedded metal nanoparticles (MNPs). MNPs act as deep traps for holes and reduce the current density compared to a device without MNPs by a factor of 104 due to the build-up of localized space charge. Dynamic MNPs charged neutrality can be realized during operation by electron transfer from excitons created in the organic matrix, enabling light sensing independent of device bias. In contr...
The Influence of Pre-Conditioning on Space Charge Formation in LDPE
DEFF Research Database (Denmark)
Fleming, Robert J.; Henriksen, Mogens; Holbøll, Joachim T.
1996-01-01
In this paper we present space charge accumulation data for planar low density polyethylene samples subjected to 20 kV/mm dc fields at room temperature. The data were obtained using the laser-induced-pressure-pulse (LIPP) technique. Some of the samples were conditioned by holding them at 40oC in ......C in short-circuit at rotary pump pressure for 48 hr prior to measurement. Such conditioning had no consistent effect on the space charge. The extent of charge injection/extraction at the semicon electrodes appeared to vary considerably between samples....
Experiments on ion space-charge neutralization with pulsed electron beams
Energy Technology Data Exchange (ETDEWEB)
Herleb, U; Riege, H [CERN LHC-Division, Geneva (Switzerland)
1997-12-31
The method of space-charge neutralization of heavy ion beams with electron beam pulses generated with electron guns incorporating ferroelectric cathodes was investigated experimentally. Several experiments are described, the results of which prove that the intensity of selected ion beam parts with defined charge states generated in a laser ion source can be increased by an order of magnitude. For elevated charge states the intensity amplification is more significant and may reach a factor of 4 for highly charged ions from an Al target. (author). 7 figs., 3 -refs.
Internal electric fields of electrolytic solutions induced by space-charge polarization
Sawada, Atsushi
2006-10-01
The dielectric dispersion of electrolytic solutions prepared using chlorobenzene as a solvent and tetrabutylammonium tetraphenylborate as a solute is analyzed in terms of space-charge polarization in order to derive the ionic constants, and the Stokes radius obtained is discussed in comparison with the values that have been measured by conductometry. A homogeneous internal electric field is assumed for simplicity in the analysis of the space-charge polarization. The justification of the approximation by the homogeneous field is discussed from two points of view: one is the accuracy of the Stokes radius value observed and the other is the effect of bound charges on electrodes in which they level the highly inhomogeneous field, which has been believed in the past. In order to investigate the actual electric field, numerical calculations based on the Poisson equation are carried out by considering the influence of the bound charges. The variation of the number of bound charges with time is clarified by determining the relaxation function of the dielectric constant attributed to the space-charge polarization. Finally, a technique based on a two-field approximation, where homogeneous and hyperbolic fields are independently applied in relevant frequency ranges, is introduced to analyze the space-charge polarization of the electrolytic solutions, and further improvement of the accuracy in the determination of the Stokes radius is achieved.
Ferroelectric plasma source for heavy ion beam space charge neutralization
International Nuclear Information System (INIS)
Efthimion, Philip C.; Gilson, Erik P.; Davidson, Ronald C.; Grisham, Larry; Grant Logan, B.; Seidl, Peter A.; Waldron, William; Yu, Simon S.
2007-01-01
Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to allow them to focus to a small spot size and compress their axial pulse length. The plasma source should be able to operate at low neutral pressures and without strong externally applied electric or magnetic fields. To produce 1 m-long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients are being developed. The sources utilize the ferroelectric ceramic BaTiO 3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic material, and high voltage (∼7 kV) will be applied between the drift tube and the front surface of the ceramics. A prototype ferroelectric source, 20 cm in length, has produced plasma densities of 5x10 11 cm -3 . It was integrated into the Neutralized Transport Experiment (NTX), and successfully charge neutralized the K + ion beam. A 1 m-long source comprised of five 20-cm-long sources has been tested. Simply connecting the five sources in parallel to a single pulse forming network power supply yielded non-uniform performance due to the time-dependent nature of the load that each of the five plasma sources experiences. Other circuit combinations have been considered, including powering each source by its own supply. The 1-m-long source has now been successfully characterized, producing relatively uniform plasma over the 1 m length of the source in the mid-10 10 cm -3 density range. This source will be integrated into the NDCX device for charge neutralization and beam compression experiments
Experimental Characterization of Space Charge in IZIP Detectors
Energy Technology Data Exchange (ETDEWEB)
Doughty, T; /UC, Berkeley; Pyle, M.; /Stanford U.; Mirabolfathi, N.; Serfass, B.; /UC, Berkeley; Kamaev, O.; /Queen' s U., Kingston; Hertel, S.; Leman, S.W.; /MIT; Brink, P.; /SLAC; Cabrera, B.; /Stanford U.; Sadoulet, B.; /UC, Berkeley
2012-06-12
Interleaved ionization electrode geometries offer the possibility of efficient rejection of near-surface events. The CDMS collaboration has recently implemented this interleaved approach for the charge and phonon readout for our germanium detectors. During a recent engineering run, the detectors were found to lose ionization stability quickly. This paper summarizes studies done in order to determine the underlying cause of the instability, as well as possible running modes that maintain stability without unacceptable loss of livetime. Additionally, results are shown for the new version IZIP mask which attempts to improve the overall stability of the detectors.
A measurement of the space-like pion electromagnetic form factor
International Nuclear Information System (INIS)
Amendolia, S.R.; Badelek, B.; Batignani, G.; Bedeschi, F.; Bertolucci, E.; Bettoni, D.; Bosisio, L.; Bradaschia, C.; Dell'Orso, M.; Fidecaro, F.; Foa, L.; Focardi, E.; Giazotto, A.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Ristori, L.; Scribano, A.; Tonelli, G.; Triggiani, G.; Codino, A.; Enorini, M.; Fabbri, F.L.; Laurelli, P.; Satta, L.; Spillantini, P.; Zallo, A.
1986-01-01
The pion form factor has been measured in the space-like q 2 region 0.014 to 0.26 (GeV/c) 2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar result to the naive pole form, and conclude π 2 >=0.439±0.008 fm 2 . (orig.)
Phase space imaging of a beam of charged particles by frictional forces
International Nuclear Information System (INIS)
Daniel, H.
1977-01-01
In the case of frictional forces, defined by always acting opposite to the particle motion, Liouville's theorem does not apply. The effect of such forces on a beam of charged particles is calculated in closed form. Emphasis is given to the phase space imaging by a moderator. Conditions for an increase in phase space density are discussed. (Auth.)
Detection of electromagnetic radiation using nonlinear materials
Hwang, Harold Y.; Liu, Mengkun; Averitt, Richard D.; Nelson, Keith A.; Sternbach, Aaron; Fan, Kebin
2016-06-14
An apparatus for detecting electromagnetic radiation within a target frequency range is provided. The apparatus includes a substrate and one or more resonator structures disposed on the substrate. The substrate can be a dielectric or semiconductor material. Each of the one or more resonator structures has at least one dimension that is less than the wavelength of target electromagnetic radiation within the target frequency range, and each of the resonator structures includes at least two conductive structures separated by a spacing. Charge carriers are induced in the substrate near the spacing when the resonator structures are exposed to the target electromagnetic radiation. A measure of the change in conductivity of the substrate due to the induced charge carriers provides an indication of the presence of the target electromagnetic radiation.
Space charge beam dynamics studies for a pulsed spallation source accelerator
Energy Technology Data Exchange (ETDEWEB)
Cho, Y.; Lessner, E.
1995-12-31
Feasibility studies for 2-GeV, 1-MW and 10-GeV, 5-MW rapid cycling synchrotrons (RCS) for spallation neutron sources have been completed. Both synchrotrons operate at a repetition rate of 30 Hz, and accelerate 1.04 {times} 10{sup 14} protons per pulse. The injection energy of the 2-GeV ring is 400 MeV, and the 10-GeV RCS accepts the beam from the 2-GeV machine. Work performed to-date includes calculation of the longitudinal space charge effects in the 400-MeV beam transfer line, and of both longitudinal and transverse space charge effects during the injection, capture and acceleration processes in the two rings. Results of space charge calculations in the rings led to proper choices of the working points and of rf voltage programs that prevents beam loss. Space charge effects in the 2-GeV synchrotron, in both transverse and longitudinal phase space, have major impact on the design due to the fact that the injection energy is 400 MeV. The design achieves the required performance while alleviating harmful effects due to space charge.
Simulation of space charge effects and transition crossing in the Fermilab Booster
International Nuclear Information System (INIS)
Lucas, P.; MacLachlan, J.
1987-03-01
The longitudinal phase space program ESME, modified for space charge and wall impedance effects, has been used to simulate transition crossing in the Fermilab Booster. The simulations yield results in reasonable quantitative agreement with measured parameters. They further indicate that a transition jump scheme currently under construction will significantly reduce emittance growth, while attempts to alter machine impedance are less obviously beneficial. In addition to presenting results, this paper points out a serious difficulty, related to statistical fluctuations, in the space charge calculation. False indications of emittance growth can appear if care is not taken to minimize this problem
International Nuclear Information System (INIS)
Borges, E.M.
1991-01-01
Thermoelectric Electromagnetic (TEEM) Pumps can be used for controlling the fluid flow in the primary and secondary circuits of liquid metal cooled space nuclear reactor. In order to simulate and to evaluate the pumps performance, in steady-state, the computer program BEMTE has been developed to study the main operational parameters and to determine the system actuation point, for a given reactor operating power. The results for each stage of the program were satisfactory, compared to experimental data. The program shows to be adequate for the design and simulating of direct current electromagnetic pumps. (author)
Space-charge effects on bunching of electrons in the CEBAF injector
International Nuclear Information System (INIS)
Liu, H.
1997-01-01
The main injector for the 4 GeV CEBAF accelerator at Thomas Jefferson national accelerator facility was designed to deliver simultaneously three CW electron beams for nuclear physics research. The maximum design current for a single beam from the injector is 100 μA, or 0.2 pC per microbunch at a repetition rate of 499 MHz. It was found through computer simulation that space charge even at a subpicocoulomb level can spoil the bunching of electrons significantly, and some unexpected phenomena observed experimentally could be explained accordingly. This problem arises because of the low-momentum tilt allowed for bunching to preserve low-momentum spread. In this paper, we analyze in detail the space-charge effects on bunching of electrons with the CEBAF injector as an example. Conditions for effective matching of longitudinal phase space in the presence of space charge are discussed. (orig.)
The influence of oxidation on space charge formation in gamma-irradiated low-density polyethylene
Chen, G; Xie, H K; Banford, H M; Davies, A E
2003-01-01
The research presented in this paper investigates the role of oxidation in the formation of space charge in gamma-irradiated low-density polyethylene after being electrically stressed under dc voltage. Polyethylene plaques both with and without antioxidant were irradiated up to 500 kGy using a sup 6 sup 0 Co gamma source and space charge distributions were measured using the piezoelectric induced pressure wave propagation method. It has been found that a large amount of positive charge evolved adjacent to the cathode in the sample without antioxidant and was clearly associated with oxidation of the surface. The amount of charge formed for a given applied stress increased with the dose absorbed by the material. A model has been proposed to explain the formation of space charge and its profile. The charge decay after the removal of the external applied stress is dominated by a process being controlled by the cathode interfacial stress (charge injection) rather than a conventional RC circuit model. On the other ...
Space charge dynamic of irradiated cyanate ester/epoxy at cryogenic temperatures
Wang, Shaohe; Tu, Youping; Fan, Linzhen; Yi, Chengqian; Wu, Zhixiong; Li, Laifeng
2018-03-01
Glass fibre reinforced polymers (GFRPs) have been widely used as one of the main electrical insulating structures for superconducting magnets. A new type of GFRP insulation material using cyanate ester/epoxy resin as a matrix was developed in this study, and the samples were irradiated by Co-60 for 1 MGy and 5 MGy dose. Space charge distributed within the sample were tested using the pulsed electroacoustic method, and charge concentration was found at the interfaces between glass fibre and epoxy resin. Thermally stimulated current (TSC) and dc conduction current were also tested to evaluate the irradiation effect. It was supposed that charge mobility and density were suppressed at the beginning due to the crosslinking reaction, and for a higher irradiation dose, molecular chain degradation dominated and led to more sever space charge accumulation at interfaces which enhance the internal electric field higher than the external field, and transition field for conduction current was also decreased by irradiation. Space charge dynamic at cryogenic temperature was revealed by conduction current and TSC, and space charge injection was observed for the irradiated samples at 225 K, which was more obvious for the irradiated samples.
EBQ code: Transport of space-charge beams in axially symmetric devices
Paul, A. C.
1982-11-01
Such general-purpose space charge codes as EGUN, BATES, WODF, and TRANSPORT do not gracefully accommodate the simulation of relativistic space-charged beams propagating a long distance in axially symmetric devices where a high degree of cancellation has occurred between the self-magnetic and self-electric forces of the beam. The EBQ code was written specifically to follow high current beam particles where space charge is important in long distance flight in axially symmetric machines possessing external electric and magnetic field. EBQ simultaneously tracks all trajectories so as to allow procedures for charge deposition based on inter-ray separations. The orbits are treated in Cartesian geometry (position and momentum) with z as the independent variable. Poisson's equation is solved in cylindrical geometry on an orthogonal rectangular mesh. EBQ can also handle problems involving multiple ion species where the space charge from each must be included. Such problems arise in the design of ion sources where different charge and mass states are present.
EBQ code: transport of space-charge beams in axially symmetric devices
International Nuclear Information System (INIS)
Paul, A.C.
1982-11-01
Such general-purpose space charge codes as EGUN, BATES, WOLF, and TRANSPORT do not gracefully accommodate the simulation of relativistic space-charged beams propagating a long distance in axially symmetric devices where a high degree of cancellation has occurred between the self-magnetic and self-electric forces of the beam. The EBQ code was written specifically to follow high current beam particles where space charge is important in long distance flight in axially symmetric machines possessing external electric and magnetic field. EBQ simultaneously tracks all trajectories so as to allow procedures for charge deposition based on inter-ray separations. The orbits are treated in Cartesian geometry (position and momentum) with z as the independent variable. Poisson's equation is solved in cylindrical geometry on an orthogonal rectangular mesh. EBQ can also handle problems involving multiple ion species where the space charge from each must be included. Such problems arise in the design of ion sources where different charge and mass states are present
Charge retention test experiences on Hubble Space Telescope nickel-hydrogen battery cells
Nawrocki, Dave E.; Driscoll, J. R.; Armantrout, J. D.; Baker, R. C.; Wajsgras, H.
1993-01-01
The Hubble Space Telescope (HST) nickel-hydrogen battery module was designed by Lockheed Missile & Space Co (LMSC) and manufactured by Eagle-Picher Ind. (EPI) for the Marshall Space Flight Center (MSFC) as an Orbital Replacement Unit (ORU) for the nickel-cadmium batteries originally selected for this low earth orbit mission. The design features of the HST nickel hydrogen battery are described and the results of an extended charge retention test are summarized.
International Nuclear Information System (INIS)
Ibarra-Sierra, V.G.; Sandoval-Santana, J.C.; Cardoso, J.L.; Kunold, A.
2015-01-01
We discuss the one-dimensional, time-dependent general quadratic Hamiltonian and the bi-dimensional charged particle in time-dependent electromagnetic fields through the Lie algebraic approach. Such method consists in finding a set of generators that form a closed Lie algebra in terms of which it is possible to express a quantum Hamiltonian and therefore the evolution operator. The evolution operator is then the starting point to obtain the propagator as well as the explicit form of the Heisenberg picture position and momentum operators. First, the set of generators forming a closed Lie algebra is identified for the general quadratic Hamiltonian. This algebra is later extended to study the Hamiltonian of a charged particle in electromagnetic fields exploiting the similarities between the terms of these two Hamiltonians. These results are applied to the solution of five different examples: the linear potential which is used to introduce the Lie algebraic method, a radio frequency ion trap, a Kanai–Caldirola-like forced harmonic oscillator, a charged particle in a time dependent magnetic field, and a charged particle in constant magnetic field and oscillating electric field. In particular we present exact analytical expressions that are fitting for the study of a rotating quadrupole field ion trap and magneto-transport in two-dimensional semiconductor heterostructures illuminated by microwave radiation. In these examples we show that this powerful method is suitable to treat quadratic Hamiltonians with time dependent coefficients quite efficiently yielding closed analytical expressions for the propagator and the Heisenberg picture position and momentum operators. -- Highlights: •We deal with the general quadratic Hamiltonian and a particle in electromagnetic fields. •The evolution operator is worked out through the Lie algebraic approach. •We also obtain the propagator and Heisenberg picture position and momentum operators. •Analytical expressions for a
Energy Technology Data Exchange (ETDEWEB)
Ibarra-Sierra, V.G.; Sandoval-Santana, J.C. [Departamento de Física, Universidad Autónoma Metropolitana Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 México D.F. (Mexico); Cardoso, J.L. [Área de Física Teórica y Materia Condensada, Universidad Autónoma Metropolitana Azcapotzalco, Av. San Pablo 180, Col. Reynosa-Tamaulipas, Azcapotzalco, 02200 México D.F. (Mexico); Kunold, A., E-mail: akb@correo.azc.uam.mx [Área de Física Teórica y Materia Condensada, Universidad Autónoma Metropolitana Azcapotzalco, Av. San Pablo 180, Col. Reynosa-Tamaulipas, Azcapotzalco, 02200 México D.F. (Mexico)
2015-11-15
We discuss the one-dimensional, time-dependent general quadratic Hamiltonian and the bi-dimensional charged particle in time-dependent electromagnetic fields through the Lie algebraic approach. Such method consists in finding a set of generators that form a closed Lie algebra in terms of which it is possible to express a quantum Hamiltonian and therefore the evolution operator. The evolution operator is then the starting point to obtain the propagator as well as the explicit form of the Heisenberg picture position and momentum operators. First, the set of generators forming a closed Lie algebra is identified for the general quadratic Hamiltonian. This algebra is later extended to study the Hamiltonian of a charged particle in electromagnetic fields exploiting the similarities between the terms of these two Hamiltonians. These results are applied to the solution of five different examples: the linear potential which is used to introduce the Lie algebraic method, a radio frequency ion trap, a Kanai–Caldirola-like forced harmonic oscillator, a charged particle in a time dependent magnetic field, and a charged particle in constant magnetic field and oscillating electric field. In particular we present exact analytical expressions that are fitting for the study of a rotating quadrupole field ion trap and magneto-transport in two-dimensional semiconductor heterostructures illuminated by microwave radiation. In these examples we show that this powerful method is suitable to treat quadratic Hamiltonians with time dependent coefficients quite efficiently yielding closed analytical expressions for the propagator and the Heisenberg picture position and momentum operators. -- Highlights: •We deal with the general quadratic Hamiltonian and a particle in electromagnetic fields. •The evolution operator is worked out through the Lie algebraic approach. •We also obtain the propagator and Heisenberg picture position and momentum operators. •Analytical expressions for a
Negative space charge effects in photon-enhanced thermionic emission solar converters
International Nuclear Information System (INIS)
Segev, G.; Weisman, D.; Rosenwaks, Y.; Kribus, A.
2015-01-01
In thermionic energy converters, electrons in the gap between electrodes form a negative space charge and inhibit the emission of additional electrons, causing a significant reduction in conversion efficiency. However, in Photon Enhanced Thermionic Emission (PETE) solar energy converters, electrons that are reflected by the electric field in the gap return to the cathode with energy above the conduction band minimum. These electrons first occupy the conduction band from which they can be reemitted. This form of electron recycling makes PETE converters less susceptible to negative space charge loss. While the negative space charge effect was studied extensively in thermionic converters, modeling its effect in PETE converters does not account for important issues such as this form of electron recycling, nor the cathode thermal energy balance. Here, we investigate the space charge effect in PETE solar converters accounting for electron recycling, with full coupling of the cathode and gap models, and addressing conservation of both electric and thermal energy. The analysis shows that the negative space charge loss is lower than previously reported, allowing somewhat larger gaps compared to previous predictions. For a converter with a specific gap, there is an optimal solar flux concentration. The optimal solar flux concentration, the cathode temperature, and the efficiency all increase with smaller gaps. For example, for a gap of 3 μm the maximum efficiency is 38% and the optimal flux concentration is 628, while for a gap of 5 μm the maximum efficiency is 31% and optimal flux concentration is 163
Active charge, passive discharge floor space heating system
Energy Technology Data Exchange (ETDEWEB)
Salt, H.; Mahoney, K.J.
1987-01-01
This space heating system has a rockbed beneath and in contact with the floor of a dwelling, which is heated by radiation and convection from the floor. The ability of the heating system to maintain comfort conditions with no additional energy input is discussed and it is shown that the system is more suitable for use in mild climates than severe ones. Experimental work on horizontal air flow rockbeds is reported and shows that shallow beds can be designed in the same way as vertical air flow beds. The influence of natural convection on the effective thermal conductivity of the experimental rockbeds is reported.
A prototype silicon detector system for space cosmic-ray charge measurement
Zhang, Fei; Fan, Rui-Rui; Peng, Wen-Xi; Dong, Yi-Fa; Gong, Ke; Liang, Xiao-Hua; Liu, Ya-Qing; Wang, Huan-Yu
2014-06-01
A readout electronics system used for space cosmic-ray charge measurement for multi-channel silicon detectors is introduced in this paper, including performance measurements. A 64-channel charge sensitive ASIC (VA140) from the IDEAS company is used. With its features of low power consumption, low noise, large dynamic range, and high integration, it can be used in future particle detecting experiments based on silicon detectors.
Gain reduction due to space charge at high counting rates in multiwire proportional chambers
International Nuclear Information System (INIS)
Smith, G.C.; Mathieson, E.
1986-10-01
Measurements with a small MWPC of gas gain reduction, due to ion space charge at high counting rates, have been compared with theoretical predictions. The quantity ln(q/q 0 )/(q/q 0 ), where (q/q 0 ) is the relative reduced avalanche charge, has been found to be closely proportional to count rate, as predicted. The constant of proportionality is in good agreement with calculations made with a modified version of the original, simplified theory
Hall, D. J.; Skottfelt, J.; Soman, M. R.; Bush, N.; Holland, A.
2017-12-01
Charge-Coupled Devices (CCDs) have been the detector of choice for imaging and spectroscopy in space missions for several decades, such as those being used for the Euclid VIS instrument and baselined for the SMILE SXI. Despite the many positive properties of CCDs, such as the high quantum efficiency and low noise, when used in a space environment the detectors suffer damage from the often-harsh radiation environment. High energy particles can create defects in the silicon lattice which act to trap the signal electrons being transferred through the device, reducing the signal measured and effectively increasing the noise. We can reduce the impact of radiation on the devices through four key methods: increased radiation shielding, device design considerations, optimisation of operating conditions, and image correction. Here, we concentrate on device design operations, investigating the impact of narrowing the charge-transfer channel in the device with the aim of minimising the impact of traps during readout. Previous studies for the Euclid VIS instrument considered two devices, the e2v CCD204 and CCD273, the serial register of the former having a 50 μm channel and the latter having a 20 μm channel. The reduction in channel width was previously modelled to give an approximate 1.6× reduction in charge storage volume, verified experimentally to have a reduction in charge transfer inefficiency of 1.7×. The methods used to simulate the reduction approximated the charge cloud to a sharp-edged volume within which the probability of capture by traps was 100%. For high signals and slow readout speeds, this is a reasonable approximation. However, for low signals and higher readout speeds, the approximation falls short. Here we discuss a new method of simulating and calculating charge storage variations with device design changes, considering the absolute probability of capture across the pixel, bringing validity to all signal sizes and readout speeds. Using this method, we
Assessment and Control of Spacecraft Charging Risks on the International Space Station
Koontz, Steve; Valentine, Mark; Keeping, Thomas; Edeen, Marybeth; Spetch, William; Dalton, Penni
2004-01-01
The International Space Station (ISS) operates in the F2 region of Earth's ionosphere, orbiting at altitudes ranging from 350 to 450 km at an inclination of 51.6 degrees. The relatively dense, cool F2 ionospheric plasma suppresses surface charging processes much of the time, and the flux of relativistic electrons is low enough to preclude deep dielectric charging processes. The most important spacecraft charging processes in the ISS orbital environment are: 1) ISS electrical power system interactions with the F2 plasma, 2) magnetic induction processes resulting from flight through the geomagnetic field and, 3) charging processes that result from interaction with auroral electrons at high latitude. Recently, the continuing review and evaluation of putative ISS charging hazards required by the ISS Program Office revealed that ISS charging could produce an electrical shock hazard to the ISS crew during extravehicular activity (EVA). ISS charging risks are being evaluated in an ongoing measurement and analysis campaign. The results of ISS charging measurements are combined with a recently developed model of ISS charging (the Plasma Interaction Model) and an exhaustive analysis of historical ionospheric variability data (ISS Ionospheric Specification) to evaluate ISS charging risks using Probabilistic Risk Assessment (PRA) methods. The PRA combines estimates of the frequency of occurrence and severity of the charging hazards with estimates of the reliability of various hazard controls systems, as required by NASA s safety and risk management programs, to enable design and selection of a hazard control approach that minimizes overall programmatic and personnel risk. The PRA provides a quantitative methodology for incorporating the results of the ISS charging measurement and analysis campaigns into the necessary hazard reports, EVA procedures, and ISS flight rules required for operating ISS in a safe and productive manner.
International Nuclear Information System (INIS)
Oh, Y.J.; Lee, J.H.; Jo, W.
2006-01-01
Retention behavior and local hysteresis characteristics in Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films on Pt electrodes have been investigated by electrostatic force microscopy (EFM). A sol-gel method is used to synthesize PZT thin films and drying conditions are carefully explored over a wide range of temperature. Decay and retention mechanisms of single-poled and reverse-poled regions of the ferroelectric thin films are explained by space charge redistribution. Trapping behavior of space charges is dependent on the nature of interface between ferroelectric thin films and bottom electrodes. Local measurement of polarization-electric field curves by EFM shows inhomogeneous space charge entrapment
Stability analysis of Hasegawa space-charge waves in a plasma waveguide with collisional ion beam
Lee, Myoung-Jae; Jung, Young-Dae
2017-12-01
The dispersion relation for the Hasegawa space-charge wave propagating in a cylindrical waveguide dusty plasma containing collision-dominated ion stream is derived by using the fluid equations and the Poisson equation which lead to a Bessel equation. The solution of Bessel equation is null at the boundary and then the roots of the Bessel function would characterize the property of space-charge wave propagation. We have found that the Hasegawa space-charge wave can be excited for a large axial wave number. The growth rate of excitation increases as the order of the roots of the Bessel function increases. The growth rate decreases with an increase of the radius of cylindrical waveguide as well as with an increase of the collision frequency. We found that the disturbance of wave can be damped only for small wave numbers.
Search for space charge effects in the ICARUS T600 LAr-TPC
Torti, Marta
2016-11-01
Space charge in Liquid Argon Time Projection Chamber is due to the accumu- lation of positive ions, produced by ionizing tracks crossing the detector, which slowly flow toward the cathode. As a consequence, electric field distortions may arise, thus hindering the possibility to produce faithful 3D images of the ionizing events. The presence of space charge becomes relevant for large TPCs operating at surface or at shallow depths, where cosmic ray flux is high. These effects could interest the next phase of the ICARUS T600 detector, which will be deployed at shallow depths as a Far Detector for Short Baseline Neutrino experiment at FNAL dedicated to sterile neutrino searches. In 2001, the first ICARUS T600 module (T300) operated at surface in Pavia (Italy), recording cosmic ray data. In this work, a sample of cosmic muon tracks from the 2001 run was analyzed and results on space charge effects in LAr-TPCs are shown.
Search for space charge effects in the ICARUS T600 LAr-TPC
International Nuclear Information System (INIS)
Torti, Marta
2016-01-01
Space charge in Liquid Argon Time Projection Chamber is due to the accumu- lation of positive ions, produced by ionizing tracks crossing the detector, which slowly flow toward the cathode. As a consequence, electric field distortions may arise, thus hindering the possibility to produce faithful 3D images of the ionizing events. The presence of space charge becomes relevant for large TPCs operating at surface or at shallow depths, where cosmic ray flux is high. These effects could interest the next phase of the ICARUS T600 detector, which will be deployed at shallow depths as a Far Detector for Short Baseline Neutrino experiment at FNAL dedicated to sterile neutrino searches. In 2001, the first ICARUS T600 module (T300) operated at surface in Pavia (Italy), recording cosmic ray data. In this work, a sample of cosmic muon tracks from the 2001 run was analyzed and results on space charge effects in LAr-TPCs are shown
International Nuclear Information System (INIS)
BEEBE - WANG, J.; LUCCIO, A.U.; D IMPERIO, N.; MACHIDA, S.
2002-01-01
Space charge in high intensity beams is an important issue in accelerator physics. Due to the complicity of the problems, the most effective way of investigating its effect is by computer simulations. In the resent years, many space charge simulation methods have been developed and incorporated in various 2D or 3D multi-particle-tracking codes. It has becoming necessary to benchmark these methods against each other, and against experimental results. As a part of global effort, we present our initial comparison of the space charge methods incorporated in simulation codes ORBIT++, ORBIT and SIMPSONS. In this paper, the methods included in these codes are overviewed. The simulation results are presented and compared. Finally, from this study, the advantages and disadvantages of each method are discussed
Simulation of a cascaded longitudinal space charge amplifier for coherent radiation generation
Energy Technology Data Exchange (ETDEWEB)
Halavanau, A., E-mail: aliaksei.halavanau@gmail.com [Department of Physics and Northern Illinois, Center for Accelerator & Detector Development, Northern Illinois University, DeKalb, IL 60115 (United States); Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Piot, P. [Department of Physics and Northern Illinois, Center for Accelerator & Detector Development, Northern Illinois University, DeKalb, IL 60115 (United States); Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)
2016-05-21
Longitudinal space charge (LSC) effects are generally considered as harmful in free-electron lasers as they can seed unfavorable energy modulations that can result in density modulations with associated emittance dilution. This “micro-bunching instabilities” is naturally broadband and could possibly support the generation of coherent radiation over a broad region of the spectrum. Therefore there has been an increasing interest in devising accelerator beam lines capable of controlling LSC induced density modulations. In the present paper we refine these previous investigations by combining a grid-less space charge algorithm with the popular particle-tracking program ELEGANT. This high-fidelity model of the space charge is used to benchmark conventional LSC models. We finally employ the developed model to investigate the performance of a cascaded LSC amplifier using beam parameters comparable to the ones achievable at Fermilab Accelerator Science & Technology (FAST) facility currently under commissioning at Fermilab.
Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions
Energy Technology Data Exchange (ETDEWEB)
Valerio-Lizarraga, Cristhian A., E-mail: cristhian.alfonso.valerio.lizarraga@cern.ch [CERN, Geneva (Switzerland); Departamento de Investigación en Física, Universidad de Sonora, Hermosillo (Mexico); Lallement, Jean-Baptiste; Lettry, Jacques; Scrivens, Richard [CERN, Geneva (Switzerland); Leon-Monzon, Ildefonso [Facultad de Ciencias Fisico-Matematicas, Universidad Autónoma de Sinaloa, Culiacan (Mexico); Midttun, Øystein [CERN, Geneva (Switzerland); University of Oslo, Oslo (Norway)
2014-02-15
The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H{sup −} beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.
Space Charge Effects and Advanced Modelling for CERN Low Energy Machines
AUTHOR|(CDS)2088716; Rumolo, Giovanni
The strong space charge regime of future operation of CERN’s circular particle accelerators is investigated and mitigation strategies are developed in the framework of the present thesis. The intensity upgrade of the injector chain of Large Hadron Collider (LHC) prepares the particle accelerators to meet the requirements of the High-Luminosity LHC project. Producing the specified characteristics of the future LHC beams imperatively relies on injecting brighter bunches into the Proton Synchrotron Booster (PSB), the downstream Proton Synchrotron (PS) and eventually the Super Proton Synchrotron (SPS). The increased brightness, i.e. bunch intensity per transverse emittance, entails stronger beam self-fields which can lead to harmful interaction with betatron resonances. Possible beam emittance growth and losses as a consequence thereof threaten to degrade the beam brightness. These space charge effects are partly mitigated by the upgrade of the PSB and PS injection energies. Nevertheless, the space charge tune ...
Energy Technology Data Exchange (ETDEWEB)
BEEBE - WANG,J.; LUCCIO,A.U.; D IMPERIO,N.; MACHIDA,S.
2002-06-03
Space charge in high intensity beams is an important issue in accelerator physics. Due to the complicity of the problems, the most effective way of investigating its effect is by computer simulations. In the resent years, many space charge simulation methods have been developed and incorporated in various 2D or 3D multi-particle-tracking codes. It has becoming necessary to benchmark these methods against each other, and against experimental results. As a part of global effort, we present our initial comparison of the space charge methods incorporated in simulation codes ORBIT++, ORBIT and SIMPSONS. In this paper, the methods included in these codes are overviewed. The simulation results are presented and compared. Finally, from this study, the advantages and disadvantages of each method are discussed.
The longitudinal space charge problem in the high current linear proton accelerators
International Nuclear Information System (INIS)
Lustfeld, H.
1984-01-01
In a linear proton accelerator peak currents of 200 mA lead to high space charge densities and the resultant space charge forces reduce the effective focussing considerably. In particular the longitudinal focussing is affected. A new concept based on linear theory is proposed that restricts the influence of the space charge forces on the longitudinal focussing by increasing a, the mean transverse bunch radius, as a proportional(βγ)sup(3/8). This concept is compared with other concepts for the Alvarez (1 MeV - 100 MeV) and for the high energy part (100 MeV - 1100 MeV) of the SNQ linear accelerator. (orig.)
Adaptive matching of the iota ring linear optics for space charge compensation
Energy Technology Data Exchange (ETDEWEB)
Romanov, A. [Fermilab; Bruhwiler, D. L. [RadiaSoft, Boulder; Cook, N. [RadiaSoft, Boulder; Hall, C. [RadiaSoft, Boulder
2016-10-09
Many present and future accelerators must operate with high intensity beams when distortions induced by space charge forces are among major limiting factors. Betatron tune depression of above approximately 0.1 per cell leads to significant distortions of linear optics. Many aspects of machine operation depend on proper relations between lattice functions and phase advances, and can be i proved with proper treatment of space charge effects. We implement an adaptive algorithm for linear lattice re matching with full account of space charge in the linear approximation for the case of Fermilab’s IOTA ring. The method is based on a search for initial second moments that give closed solution and, at the same predefined set of goals for emittances, beta functions, dispersions and phase advances at and between points of interest. Iterative singular value decomposition based technique is used to search for optimum by varying wide array of model parameters
Aspects of space charge theory applied to dielectric under electron beam irradiation
International Nuclear Information System (INIS)
Oliveira, L.N. de.
1975-01-01
Irradiation of solid dielectric with electron beams has been used as a power full tool in investigations of charge storage and transport in such materials. Some of the results that have been obtained in this area are reviewed and the formulation of a transport equation for excess charge in irradiated insulators is dicussed. This equation is subsequently applied to various experimental set-ups. It is found that space charge effects play an essential role in the establishment of stationary currents in samples subject to quasi-penetrating electron beams. Such effects may, however, be neglected for low electron ranges. Theoretical results are in good agreement with experimental findings by Spear (1955)
Structural-electromagnetic bidirectional coupling analysis of space large film reflector antennas
Zhang, Xinghua; Zhang, Shuxin; Cheng, ZhengAi; Duan, Baoyan; Yang, Chen; Li, Meng; Hou, Xinbin; Li, Xun
2017-10-01
As used for energy transmission, a space large film reflector antenna (SLFRA) is characterized by large size and enduring high power density. The structural flexibility and the microwave radiation pressure (MRP) will lead to the phenomenon of structural-electromagnetic bidirectional coupling (SEBC). In this paper, the SEBC model of SLFRA is presented, then the deformation induced by the MRP and the corresponding far field pattern deterioration are simulated. Results show that, the direction of the MRP is identical to the normal of the reflector surface, and the magnitude is proportional to the power density and the square of cosine incident angle. For a typical cosine function distributed electric field, the MRP is a square of cosine distributed across the diameter. The maximum deflections of SLFRA linearly increase with the increasing microwave power densities and the square of the reflector diameters, and vary inversely with the film thicknesses. When the reflector diameter becomes 100 m large and the microwave power density exceeds 102 W/cm2, the gain loss of the 6.3 μm-thick reflector goes beyond 0.75 dB. When the MRP-induced deflection degrades the reflector performance, the SEBC should be taken into account.
Modelling of Electromagnetic Scattering by a Hypersonic Cone-Like Body in Near Space
Directory of Open Access Journals (Sweden)
Ji-Wei Qian
2017-01-01
Full Text Available A numerical procedure for analysis of electromagnetic scattering by a hypersonic cone-like body flying in the near space is presented. First, the fluid dynamics equation is numerically solved to obtain the electron density, colliding frequency, and the air temperature around the body. They are used to calculate the complex relative dielectric constants of the plasma sheath. Then the volume-surface integral equation method is adopted to analyze the scattering properties of the body plus the plasma sheath. The Backscattering Radar Cross-Sections (BRCS for the body flying at different speeds, attack angles, and elevations are examined. Numerical results show that the BRCS at a frequency higher than 300 MHz is only slightly affected if the speed is smaller than 7 Mach. The BRCS at 1 GHz would be significantly reduced if the speed is greater than 7 Mach and is continuously increased, which can be attributed to the absorption by the lossy plasma sheath. Typically, the BRCS is influenced by 5~10 dBm for a change of attack angle within 0~15 degrees, or for a change of elevation within 30~70 km above the ground.
Space-charge Effect on Electroresistance in Metal-Ferroelectric-Metal capacitors
Tian, Bo Bo; Liu, Yang; Chen, Liu Fang; Wang, Jian Lu; Sun, Shuo; Shen, Hong; Sun, Jing Lan; Yuan, Guo Liang; Fusil, Stéphane; Garcia, Vincent; Dkhil, Brahim; Meng, Xiang Jian; Chu, Jun Hao
2015-12-01
Resistive switching through electroresistance (ER) effect in metal-ferroelectric-metal (MFM) capacitors has attracted increasing interest due to its potential applications as memories and logic devices. However, the detailed electronic mechanisms resulting in large ER when polarisation switching occurs in the ferroelectric barrier are still not well understood. Here, ER effect up to 1000% at room temperature is demonstrated in C-MOS compatible MFM nanocapacitors with a 8.8 nm-thick poly(vinylidene fluoride) (PVDF) homopolymer ferroelectric, which is very promising for silicon industry integration. Most remarkably, using theory developed for metal-semiconductor rectifying contacts, we derive an analytical expression for the variation of interfacial barrier heights due to space-charge effect that can interpret the observed ER response. We extend this space-charge model, related to the release of trapped charges by defects, to MFM structures made of ferroelectric oxides. This space-charge model provides a simple and straightforward tool to understand recent unusual reports. Finally, this work suggests that defect-engineering could be an original and efficient route for tuning the space-charge effect and thus the ER performances in future electronic devices.
Three-dimensional space charge distribution measurement in electron beam irradiated PMMA
International Nuclear Information System (INIS)
Imaizumi, Yoichi; Suzuki, Ken; Tanaka, Yasuhiro; Takada, Tatsuo
1996-01-01
The localized space charge distribution in electron beam irradiated PMMA was investigated using pulsed electroacoustic method. Using a conventional space charge measurement system, the distribution only in the depth direction (Z) can be measured assuming the charges distributed uniformly in the horizontal (X-Y) plane. However, it is difficult to measure the distribution of space charge accumulated in small area. Therefore, we have developed the new system to measure the three-dimensional space charge distribution using pulsed electroacoustic method. The system has a small electrode with a diameter of 1mm and a motor-drive X-Y stage to move the sample. Using the data measured at many points, the three-dimensional distribution were obtained. To estimate the system performance, the electron beam irradiated PMMA was used. The electron beam was irradiated from transmission electron microscope (TEM). The depth of injected electron was controlled using the various metal masks. The measurement results were compared with theoretically calculated values of electron range. (author)
Simulation of the plasma meniscus with and without space charge using triode extraction system
International Nuclear Information System (INIS)
Rahman, M.M.Abdel; El-Khabeary, H.
2009-01-01
In this work, simulation of the singly charged argon ion trajectories for a variable plasma meniscus is studied with and without space charge for the triode extraction system by using SIMION 3D (Simulation of Ion Optics in Three Dimensions) version 7 personal computer program. The influence of acceleration voltage applied to the acceleration electrode of the triode extraction system on the shape of the plasma meniscus has been determined. The plasma electrode is set at +5000 volt and the acceleration voltage applied to the acceleration electrode is varied from -5000 volt to +5000 volt. In the most of the concave and convex plasma shapes, ion beam emittance can be calculated by using separate standard deviations of positions and elevations angles. Ion beam emittance as a function of the curvature of the plasma meniscus for different plasma shapes ( flat, concave and convex ) without space charge at acceleration voltage varied from -5000 volt to +5000 volt applied to the acceleration electrode of the triode extraction system has been investigated. The influence of the extraction gap on ion beam emittance for a plasma concave shape of 3.75 mm without space charge at acceleration voltage, V acc = -2000 volt applied to the acceleration electrode of the triode extraction system has been determined. Also the influence of space charge on ion beam emittance for variable plasma meniscus at acceleration voltage, V acc = -2000 volt applied to the acceleration electrode of the triode extraction system has been studied. (author)
Energy Technology Data Exchange (ETDEWEB)
Halavanau, A. [Northern Illinois U.; Piot, P. [Northern Illinois U.
2015-12-01
Cascaded Longitudinal Space Charge Amplifiers (LSCA) have been proposed as a mechanism to generate density modulation over a board spectral range. The scheme has been recently demonstrated in the optical regime and has confirmed the production of broadband optical radiation. In this paper we investigate, via numerical simulations, the performance of a cascaded LSCA beamline at the Fermilab Accelerator Science & Technology (FAST) facility to produce broadband ultraviolet radiation. Our studies are carried out using elegant with included tree-based grid-less space charge algorithm.
Observation of Octupole Driven Resonance Phenomena with Space Charge at the CERN Proton Synchrotron
Métral, E; Martini, M; Steerenberg, R; Franchetti, Giuliano; Hofmann, I
2006-01-01
Several benchmarking space charge experiments have been performed during the last few years in the CERN Proton Synchrotron. These controlled experiments are of paramount importance to validate the present very powerful simulation codes. The observations of the combined effect of space charge and nonlinear resonance on beam loss and emittance, using a single controllable octupole during ~ 1 s at 1.4 GeV kinetic energy, are discussed in some detail in the present paper. By lowering the working point towards the octupolar resonance, a gradual transition from a regime of loss-free core emittance blow-up to a regime of continuous loss was found.
Phase modulation spectroscopy of space-charge wave resonances in Bi12SiO20
DEFF Research Database (Denmark)
Vasnetsov, M.; Buchhave, Preben; Lyuksyutov, S.
1997-01-01
A new experimental method for the study of resonance effects and space-charge wave excitation in photorefractive Bi12SiO20 crystals by using a combination of frequency detuning and phase modulation technique has been developed. The accuracy of the method allows a detection of resonance peaks...... of diffraction efficiency within 0.5 Hz. Numerical simulations of the nonlinear differential equations describing the behaviour of the space-charge waves in photorefractive crystals have been performed and found to be in a good agreement with experiment. We have measured the photocurrent through the crystal...
Transverse modes of a bunched beam with space charge dominated impedance
Directory of Open Access Journals (Sweden)
V. Balbekov
2009-12-01
Full Text Available Transverse coherent oscillations of a bunched beam in a ring accelerator are considered with space charge dominated impedance, taking into account linear synchrotron oscillations. A general equation of the bunch eigenmodes is derived, its exact analytical solution is presented for boxcar bunch, and numerical solutions are found for several realistic models. Both low and high synchrotron frequency approximations are considered and compared, fields of their applicability are determined, and some estimations are developed in the intermediate region. It is shown that most of the bunch eigenmodes are stabilized by Landau damping due to the space charge produced tune spread.
CrossRef Space-charge effects in Penning ion traps
Porobić, T; Breitenfeldt, M; Couratin, C; Finlay, P; Knecht, A; Fabian, X; Friedag, P; Fléchard, X; Liénard, E; Ban, G; Zákoucký, D; Soti, G; Van Gorp, S; Weinheimer, Ch; Wursten, E; Severijns, N
2015-01-01
The influence of space-charge on ion cyclotron resonances and magnetron eigenfrequency in a gas-filled Penning ion trap has been investigated. Off-line measurements with View the MathML source using the cooling trap of the WITCH retardation spectrometer-based setup at ISOLDE/CERN were performed. Experimental ion cyclotron resonances were compared with ab initio Coulomb simulations and found to be in agreement. As an important systematic effect of the WITCH experiment, the magnetron eigenfrequency of the ion cloud was studied under increasing space-charge conditions. Finally, the helium buffer gas pressure in the Penning trap was determined by comparing experimental cooling rates with simulations.
International Nuclear Information System (INIS)
Cardoso, Vitor; Lemos, Jose P.S.; Yoshida, Shijun
2003-01-01
We investigate the electromagnetic radiation released during the high energy collision of a charged point particle with a four-dimensional Schwarzschild black hole. We show that the spectra is flat, and well described by a classical calculation. We also compare the total electromagnetic and gravitational energies emitted, and find that the former is suppressed in relation to the latter for very high energies. These results could apply to the astrophysical world in the case that charged stars and small charged black holes are out there colliding into large black holes, and to a very high energy collision experiment in a four-dimensional world. In this latter scenario the calculation is to be used for the moments just after black hole formation, when the collision of charged debris with the newly formed black hole is certainly expected. Since the calculation is four dimensional, it does not directly apply to TeV-scale gravity black holes, as these inhabit a world of six to eleven dimensions, although our results should qualitatively hold when extrapolated with some care to higher dimensions
Energy Technology Data Exchange (ETDEWEB)
Tang Chao; Liao Ruijin [The State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University (China); Chen, G [School of Electronics and Computer Science, University of Southampton (United Kingdom); Fu, M, E-mail: tangchao_1981@163.co [AVERA T and D Technology Centre, Stafford (United Kingdom)
2009-08-01
In this paper, space charge in a multi-layer oil-paper insulation system was investigated using the pulsed electroacoustic (PEA) technique. A series of measurements had been carried following subjection of the insulation system to different applied voltages and different temperatures. Charge behaviours in the insulation system were analyzed and the influence of temperature on charge dynamics was discussed. The test results shows that homocharge injection takes place under all the test conditions, the applied DC voltage mainly affects the amount of space charge, while the temperature has greater influence on the distribution and mobility of space charge inside oil-paper samples.
International Nuclear Information System (INIS)
Alba, D.; Crater, H.W.; Lusanna, L.
2010-01-01
A complete exposition of the rest-frame instant form of dynamics for arbitrary isolated systems (particles, fields, strings, fluids) admitting a Lagrangian description is given. The starting point is the parametrized Minkowski theory describing the system in arbitrary admissible noninertial frames in Minkowski space-time, which allows one to define the energy-momentum tensor of the system and to show the independence of the description from the clock synchronization convention and from the choice of the 3-coordinates. The restriction to the inertial rest frame, centered on the inertial observer having the Fokker-Pryce center-of-inertia world-line, and the study of relativistic collective variables replacing the nonrelativistic center of mass lead to the description of the isolated system as a decoupled globally defined noncovariant canonical external center of mass carrying a pole-dipole structure (the invariant mass M and the rest spin S¯ of the system) and an external realization of the Poincare group. Mc and S¯ are the energy and angular momentum of a unfaithful internal realization of the Poincare group built with the energy-momentum tensor of the system and acting inside the instantaneous Wigner 3-spaces where all the 3-vectors are Wigner covariant. The vanishing of the internal 3-momentum and of the internal Lorentz boosts eliminate the internal 3-center of mass inside the Wigner 3-spaces, so that at the end the isolated system is described only by Wigner-covariant canonical internal relative variables. Then an isolated system of positive-energy charged scalar articles with mutual Coulomb interaction plus a transverse electromagnetic field in the radiation gauge is investigated as a classical background for defining relativistic atomic physics. The electric charges of the particles are Grassmann-valued to regularize the self-energies. The external and internal realizations of the Poincare algebra in the rest-frame instant form of dynamics are found. This
International Nuclear Information System (INIS)
Haouat, S.; Chekireb, R.
2012-01-01
The influence of electromagnetic fields on the creation of scalar particles from vacuum in a flat Robertson-Walker space-time is studied. The Klein-Gordon equation with varying electric field and constant magnetic one is solved. The Bogoliubov transformation method is applied to calculate the pair creation probability and the number density of created particles. It is shown that the electric field amplifies the creation of scalar particles while the magnetic field minimizes it. (orig.)
International Nuclear Information System (INIS)
Domijan, A.D. Jr.; Emami, M.V.
1990-01-01
This paper reports on a simulation of a MHO distance relay developed to study the effect of its operation under various system conditions. Simulation is accomplished using a state space approach and a modeling technique using ElectroMagnetic Transient Program (Transient Analysis of Control Systems). Furthermore, simulation results are compared with those obtained in another independent study as a control, to validate the results. A data code for the practical utilization of this simulation is given
Phase space properties of charged fields in theories of local observables
International Nuclear Information System (INIS)
Buchholz, D.; D'Antoni, C.
1994-10-01
Within the setting of algebraic quantum field theory a relation between phase-space properties of observables and charged fields is established. These properties are expressed in terms of compactness and nuclarity conditions which are the basis for the characterization of theories with physically reasonable causal and thermal features. Relevant concepts and results of phase space analysis in algebraic qunatum field theory are reviewed and the underlying ideas are outlined. (orig.)
A heterogeneous CPU+GPU Poisson solver for space charge calculations in beam dynamics studies
Energy Technology Data Exchange (ETDEWEB)
Zheng, Dawei; Rienen, Ursula van [University of Rostock, Institute of General Electrical Engineering (Germany)
2016-07-01
In beam dynamics studies in accelerator physics, space charge plays a central role in the low energy regime of an accelerator. Numerical space charge calculations are required, both, in the design phase and in the operation of the machines as well. Due to its efficiency, mostly the Particle-In-Cell (PIC) method is chosen for the space charge calculation. Then, the solution of Poisson's equation for the charge distribution in the rest frame is the most prominent part within the solution process. The Poisson solver directly affects the accuracy of the self-field applied on the charged particles when the equation of motion is solved in the laboratory frame. As the Poisson solver consumes the major part of the computing time in most simulations it has to be as fast as possible since it has to be carried out once per time step. In this work, we demonstrate a novel heterogeneous CPU+GPU routine for the Poisson solver. The novel solver also benefits from our new research results on the utilization of a discrete cosine transform within the classical Hockney and Eastwood's convolution routine.
Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy
International Nuclear Information System (INIS)
Chen, Qian Nataly; Li, Jiangyu; Adler, Stuart B.
2014-01-01
Nanocrystalline ceria exhibits a total conductivity several orders of magnitude higher than microcrystalline ceria in air at high temperature. The most widely accepted theory for this enhancement (based on fitting of conductivity data to various transport and kinetic models) is that relatively immobile positively charged defects and/or impurities accumulate at the grain boundary core, leading to a counterbalancing increase in the number of mobile electrons (small polarons) within a diffuse space charge region adjacent to each grain boundary. In an effort to validate this model, we have applied electrochemical strain microscopy to image the location and relative population of mobile electrons near grain boundaries in polycrystalline Sm-doped ceria in air at 20–200 °C. Our results show the first direct (spatially resolved) evidence that such a diffuse space charge region does exist in ceria, and is localized to both grain boundaries and the gas-exposed surface
Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy
Energy Technology Data Exchange (ETDEWEB)
Chen, Qian Nataly; Li, Jiangyu, E-mail: jjli@uw.edu [Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195 (United States); Adler, Stuart B., E-mail: stuadler@uw.edu [Department of Chemical Engineering, University of Washington, Seattle, Washington 98195 (United States)
2014-11-17
Nanocrystalline ceria exhibits a total conductivity several orders of magnitude higher than microcrystalline ceria in air at high temperature. The most widely accepted theory for this enhancement (based on fitting of conductivity data to various transport and kinetic models) is that relatively immobile positively charged defects and/or impurities accumulate at the grain boundary core, leading to a counterbalancing increase in the number of mobile electrons (small polarons) within a diffuse space charge region adjacent to each grain boundary. In an effort to validate this model, we have applied electrochemical strain microscopy to image the location and relative population of mobile electrons near grain boundaries in polycrystalline Sm-doped ceria in air at 20–200 °C. Our results show the first direct (spatially resolved) evidence that such a diffuse space charge region does exist in ceria, and is localized to both grain boundaries and the gas-exposed surface.
Czech Academy of Sciences Publication Activity Database
Zelinka, Jiří; Oral, Martin; Radlička, Tomáš
2018-01-01
Roč. 184, JAN (2018), s. 66-76 ISSN 0304-3991 R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : space charge * self-consistent simulation * aberration polynomial * electron emission Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.843, year: 2016
DEFF Research Database (Denmark)
Bambery, K.R.; Fleming, R.J.; Holbøll, Joachim
2001-01-01
.5×107 V m-1. Current density was also measured as a function of temperature and field. Space charge due exclusively to the temperature gradient was detected, with density of order 0.01 C m-3. The activation energy associated with the transport of electrons through the bulk was calculated as 0.09 e...
Study of electric field distorted by space charges under positive lightning impulse voltage
Wang, Zezhong; Geng, Yinan
2018-03-01
Actually, many insulation problems are related to electric fields. And measuring electric fields is an important research topic of high-voltage engineering. In particular, the electric field distortion caused by space charge is the basis of streamer theory, and thus quantitatively measuring the Poisson electric field caused by space charge is significant to researching the mechanism of air gap discharge. In this paper, we used our photoelectric integrated sensor to measure the electric field distribution in a 1-m rod-plane gap under positive lightning impulse voltage. To verify the reliability of this quantitative measurement, we compared the measured results with calculated results from a numerical simulation. The electric-field time domain waveforms on the axis of the 1-m rod-plane out of the space charge zone were measured with various electrodes. The Poisson electric fields generated by space charge were separated from the Laplace electric field generated by applied voltages, and the amplitudes and variations were measured for various applied voltages and at various locations. This work also supplies the feasible basis for directly measuring strong electric field under high voltage.
Beam halo formation from space-charge dominated beams in uniform focusing channels
International Nuclear Information System (INIS)
O'Connell, J.S.; Wangler, T.P.; Mills, R.S.; Crandall, K.R.
1993-01-01
In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which results in a 2-component beam consisting of an inner core and an outer halo. The halo is very prominent in mismatched beams, and the potential for accelerator activation is of concern for a next generation of cw, high-power proton linacs that could be applied for intense neutron generators to process nuclear materials. We present new results about beam halo and the evolution of space-charge dominated beams from multiparticle simulation of initial laminar beams in a uniform linear focusing channel, and from a model consisting of single particle interactions with a uniform-density beam core. We study the energy gain from particle interactions with the space-charge field of the core, and we identify the resonant characteristic of this interaction as the basic cause of the separation of the beam into the two components. We identify three different particle-trajectory types, and we suggest that one of these types may lead to continuous halo growth, even after the halo is removed by collimators
Space charge and beam stability issues of the Fermilab proton driver in Phase I
Energy Technology Data Exchange (ETDEWEB)
K. Y. Ng
2001-08-24
Issues concerning beam stability of the proposed Fermilab Proton Driver are studied in its Phase I. Although the betatron tune shifts are dominated by space charge, these shifts are less than 0.25 and will therefore not drive the symmetric and antisymmetric modes of the beam envelope into instability. The longitudinal space charge force is large and inductive inserts may be needed to compensate for the distortion of the rf potential. Although the longitudinal impedance is space charge dominated, it will not drive any microwave instability, unless the real part of the impedance coming from the inductive inserts and wall resistivity of the beam tube are large enough. The design of the beam tube is therefore very important in order to limit the flow of eddy current and keep wall resistivity low. The transverse impedance is also space charge dominated. With the Proton Driver operated at an imaginary transition gamma, however, Landau damping will never be canceled and beam stability can be maintained with negative chromaticities.
Calculation and measurement of space charge in MV-size xxtruded cables systems under load conditions
Morshuis, P.H.F.; Bodega, R.; Fabiani, D.; Montanari, G.C.; Dissado, L.A.; Smit, J.J.
2007-01-01
A load current in dc high voltage cables results in a temperature drop across the insulation and hence a radial distribution of the insulation conductivity is found. Direct consequence is an accumulation of space charge in the bulk of the nsulation, that may significantly affect its reliability.
Progress in 3D Space-charge Calculations in the GPT Code
Pöplau, G.; Rienen, van U.; Loos, de M.J.; Geer, van der S.B.
2004-01-01
The mesh-based 3D space-charge routine in the GPT (General Particle Tracer, Pulsar Physics) code scales linearly with the number of particles in terms of CPU time and allows a million particles to be tracked on a normal PC. The crucial ingredient of the routine is a non-equidistant multi-grid
The Influence of Pre-conditioning on the Space Charge Formation in LDPE and XLPE
DEFF Research Database (Denmark)
Henriksen, Mogens; Holbøll, Joachim T.; Fleming, R.J.
1996-01-01
Planar LDPE and XLPE samples were conditioned by holding in short circuit for 48 hrs. at 40oC under rotary pump pressure, and space charge accumulation in these samples under DC fields of 20 kV/mm was then compared with the corresponding accumulation in unconditioned samples.The test results were...
Radial space-charge-limited electron flow in semi-insulating GaN:Fe
Czech Academy of Sciences Publication Activity Database
Mareš, Jiří J.; Hubík, Pavel; Krištofik, Jozef; Prušáková, Lucie; Uxa, Štěpán; Paskova, T.; Evans, K.
2011-01-01
Roč. 110, č. 1 (2011), 013723/1-013723/6 ISSN 0021-8979 R&D Projects: GA ČR GAP204/10/0212 Institutional research plan: CEZ:AV0Z10100521 Keywords : gallium nitride * semi-insulator * space-charge-limited current Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.168, year: 2011
Light-induced space-charge fields for the structuration of dielectric materials
International Nuclear Information System (INIS)
Eggert, H.A.
2006-11-01
Light-induced space-charge fields in lithium-niobate crystals are used for patterning of dielectric materials. This includes tailored ferroelectric domains in the bulk of the crystal, different sorts of micro and nanoparticles on a crystal surface, as well as poling of electrooptic chromophores. A stochastical model is introduced, which can describe the spatial inhomogeneous domain inversion. (orig.)
The effect of space charge force on beams extracted from ECR ion sources
International Nuclear Information System (INIS)
Xie, Z.Q.
1989-01-01
A new 3 dimensional ray tracing code BEAM-3D, with a simple model to calculate the space charge force of multiple ion species, is under development and serves as a theoretical tool to study the ECRIS beam formation. Excellent agreement between the BEAM-3D calculations and beam profile and emittance measurements of the total extracted helium 1+ beam from the RTECR ion source was obtained when a low degree of beam neutralization was assumed in the calculations. The experimental evidence indicates that the positive space charge effects dominate the early RTECR ion source beam formation and beamline optics matching process. A review of important beam characteristics is made, including a conceptual model for the space charge beam blow up. Better beam transport through the RTECR beamline analysis magnet has resulted after an extraction geometry modification in which the space charge force was more correctly matched. This work involved the development of an online beam characteristic measuring apparatus which will also be described
Simulation of the Plasma Meniscus with and without Space Charge using Triode Extraction System
International Nuclear Information System (INIS)
Abdel Rahman, M.M.; EI-Khabeary, H.
2007-01-01
In this work simulation of the singly charged argon ion trajectories for a variable plasma meniscus is studied with and without space charge for the triode extraction system by using SIMION 3D (Simulation of Ion Optics in Three Dimensions) version 7 personal computer program. Tbe influence of acceleration voltage applied to tbe acceleration electrode of the triode extraction system on the shape of the plasma meniscus has been determined. The plasma electrode is set at +5000 volt and the acceleration voltage applied to the acceleration electrode is varied from -5000 volt to +5000 volt. In the most of the concave and convex plasma shapes ion beam emittance can be calculated by using separate standard deviations of positions and elevations angles. Ion beam emittance as a function of the curvature of the plasma meniscus for different plasma shapes ( flat concave and convex ) without space change at acceleration voltage varied from -5000 volt to +5000 volt applied to the acceleration electrode of the triode extraction system has been investigated. Tbe influence of the extraction gap on ion beam emittance for a plasma concave shape of 3.75 mm without space charge at acceleration voltage, V a cc = -2000 volt applied to the acceleration electrode of the triode extraction system has been determined. Also the influence of space charge on ion beam emittance for variable plasma meniscus at acceleration voltage, V a cc = - 2000 volt applied to the acceleration electrode of. the triode extraction system has been studied
Theory of space-charge polarization for determining ionic constants of electrolytic solutions
Sawada, Atsushi
2007-06-01
A theoretical expression of the complex dielectric constant attributed to space-charge polarization has been derived under an electric field calculated using Poisson's equation considering the effects of bound charges on ions. The frequency dependence of the complex dielectric constant of chlorobenzene solutions doped with tetrabutylammonium tetraphenylborate (TBATPB) has been analyzed using the theoretical expression, and the impact of the bound charges on the complex dielectric constant has been clarified quantitatively in comparison with a theory that does not consider the effect of the bound charges. The Stokes radius of TBA +(=TPB-) determined by the present theory shows a good agreement with that determined by conductometry in the past; hence, the present theory should be applicable to the direct determination of the mobility of ion species in an electrolytic solution without the need to measure ionic limiting equivalent conductance and transport number.
International Nuclear Information System (INIS)
Bourdier, A.
1999-01-01
This work concerns mainly the dynamics of a charged particle in an electromagnetic wave. It is a first step in elaborating a more general model permitting to predict the wave-particle interaction. We show how deriving a first integral gives an idea on how to create an electron current in a cold electron plasma. We present results which can be used to test the 2D and 3D Vlasov-Maxwell codes being built up in CEA-DAM. These codes will allow the calcination of the magnetic field created by an electromagnetic wave like the one due to the inverse Faraday effect when a circularly polarized wave drives the electrons of a plasma into circular orbits. (author)
Plasma-induced evolution behavior of space-charge-limited current for multiple-needle cathodes
International Nuclear Information System (INIS)
Li Limin; Liu Lie; Zhang Jun; Wen Jianchun; Liu Yonggui; Wan Hong
2009-01-01
Properties of the plasma and beam flow produced by tufted carbon fiber cathodes in a diode powered by a ∼500 kV, ∼400 ns pulse are investigated. Under electric fields of 230-260 kV cm -1 , the electron current density was in the range 210-280 A cm -2 , and particularly at the diode gap of 20 mm, a maximum beam power density of about 120 MW cm -2 was obtained. It was found that space-charge-limited current exhibited an evolution behavior as the accelerating pulse proceeded. There exists a direct relation between the movement of plasma within the diode and the evolution of space-charge-limited current. Initially in the accelerating pulse, the application of strong electric fields caused the emission sites to explode, forming cathode flares or plasma spots, and in this stage the space-charge-limited current was approximately described by a multiple-needle cathode model. As the pulse proceeded, these plasma spots merged and expanded towards the anode, thus increasing the emission area and shortening the diode gap, and the corresponding space-charge-limited current followed a planar cathode model. Finally, the space-charge-limited current is developed from a unipolar flow into a bipolar flow as a result of the appearance of anode plasma. In spite of the nonuniform distribution of cathode plasma, the cross-sectional uniformity of the extracted electron beam is satisfactory. The plasma expansion within the diode is found to be a major factor in the diode perveance growth and instability. These results show that these types of cathodes can offer promising applications for high-power microwave tubes.
Energy Technology Data Exchange (ETDEWEB)
Delcroix, Jean-Loup
1953-05-30
This research thesis reports an in-depth analysis of physical properties of static regimes to address the issue of space charges. This theoretical study of the Hull magnetron is followed by the description of experiments on the Hull magnetron which highlight transitions between the different regimes. Then, another theoretical approach aims at generalising the magnetron theory, based on other types of magnetron theory (general equations of magnetron-type space charges, inverted Hull magnetron theory, circular field magnetron theory)
Safety of information in electronic equipment influenced by the charged space particles
Directory of Open Access Journals (Sweden)
Ksenia Gennad’evna Sizova
2016-10-01
Full Text Available A version of the existing evaluation method of electronic equipment to the influence of charged space particles causing single event effects for the purpose of improving the accuracy of calculation in the field of information safety is suggested. On the basis of the existing and modified methods radiation tolerance of real payload spacecraft responsible for the security of transmitted information are defined. The results of comparison are introduced. Significant differences not only in quantitative but also in qualitative character of tolerance indicators are revealed. It is demonstrated that the modified method allows to take into account the functional complexity of the hardware and the application efficiency of the sophisticated single event effects protection tools. To confirm the applicability of the modified method of equipment tolerance evaluation method to the influence of charged space particles causing single event effects proposals to the procedure of ground tests of the payload and the space experiment are developed.
Skevington, Jennifer L.
2010-01-01
Charged particle sources are integral devices used by Marshall Space Flight Center s Environmental Effects Branch (EM50) in order to simulate space environments for accurate testing of materials and systems. By using these sources inside custom vacuum systems, materials can be tested to determine charging and discharging properties as well as resistance to sputter damage. This knowledge can enable scientists and engineers to choose proper materials that will not fail in harsh space environments. This paper combines the steps utilized to build a low energy electron gun (The "Skevington 3000") as well as the methods used to characterize the output of both the Skevington 3000 and a manufactured Xenon ion source. Such characterizations include beam flux, beam uniformity, and beam energy. Both sources were deemed suitable for simulating environments in future testing.
Alexander, LYSENKO; Iurii, VOLK
2018-03-01
We developed a cubic non-linear theory describing the dynamics of the multiharmonic space-charge wave (SCW), with harmonics frequencies smaller than the two-stream instability critical frequency, with different relativistic electron beam (REB) parameters. The self-consistent differential equation system for multiharmonic SCW harmonic amplitudes was elaborated in a cubic non-linear approximation. This system considers plural three-wave parametric resonant interactions between wave harmonics and the two-stream instability effect. Different REB parameters such as the input angle with respect to focusing magnetic field, the average relativistic factor value, difference of partial relativistic factors, and plasma frequency of partial beams were investigated regarding their influence on the frequency spectrum width and multiharmonic SCW saturation levels. We suggested ways in which the multiharmonic SCW frequency spectrum widths could be increased in order to use them in multiharmonic two-stream superheterodyne free-electron lasers, with the main purpose of forming a powerful multiharmonic electromagnetic wave.
A feasibility study of space-charge neutralized ion induction linacs: Final report
International Nuclear Information System (INIS)
Slutz, S.A.; Primm, P.; Renk, T.; Johnson, D.J.
1997-03-01
Applications for high current (> 1 kA) ion beams are increasing. They include hardening of material surfaces, transmutation of radioactive waste, cancer treatment, and possibly driving fusion reactions to create energy. The space-charge of ions limits the current that can be accelerated in a conventional ion linear accelerator (linac). Furthermore, the accelerating electric field must be kept low enough to avoid the generation and acceleration of counter-streaming electrons. These limitations have resulted in ion accelerator designs that employ long beam lines and would be expensive to build. Space-charge neutralization and magnetic insulation of the acceleration gaps could substantially reduce these two limitations, but at the expense of increasing the complexity of the beam physics. We present theory and experiments to determine the degree of charge-neutralization that can be achieved in various environments found in ion accelerators. Our results suggest that, for high current applications, space-charge neutralization could be used to improve on the conventional ion accelerator technology. There are two basic magnetic field geometries that can be used to insulate the accelerating gaps, a radial field or a cusp field. We will present studies related to both of these geometries. We shall also present numerical simulations of open-quotes multicuspclose quotes accelerator that would deliver potassium ions at 400 MeV with a total beam power of approximately 40 TW. Such an accelerator could be used to drive fusion
Surface Layer Fluorination-Modulated Space Charge Behaviors in HVDC Cable Accessory
Directory of Open Access Journals (Sweden)
Jin Li
2018-05-01
Full Text Available Space charges tend to accumulate on the surface and at the interface of ethylene–propylene–diene terpolymer (EPDM, serving as high voltage direct current (HVDC cable accessory insulation, which likely induces electrical field distortion and dielectric breakdown. Direct fluorination is an effective method to modify the surface characteristics of the EPDM without altering the bulk properties too much. In this paper, the surface morphology, hydrophobic properties, relative permittivity, and DC conductivity of the EPDM before and after fluorination treatment were tested. Furthermore, the surface and interface charge behaviors in the HVDC cable accessory were investigated by the pulsed electroacoustic (PEA method, and explained from the point of view of trap distribution. The results show that fluorination helps the EPDM polymer obtain lower surface energy and relative permittivity, which is beneficial to the interface match in composite insulation systems. The lowest degree of space charge accumulation occurs in EPDM with 30 min of fluorination. After analyzing the results of the 3D potentials and the density of states (DOS behaviors in EPDM before and after fluorination, it can be found that fluorination treatment introduces shallower electron traps, and the special electrostatic potential after fluorination can significantly suppress the space charge accumulation at the interface in the HVDC cable accessory.
Kramer, Leonard; Kerslake, Thomas W.; Galofaro, Joel T.
2010-01-01
The International Space Station (ISS) undergoes electrical charging in low Earth orbit (LEO) due to positively biased, exposed conductors on solar arrays that collect electrical charges from the space plasma. Exposed solar array conductors predominately collect negatively charged electrons and thus drive the metal ISS structure electrical ground to a negative floating potential (FP) relative to plasma. This FP is variable in location and time as a result of local ionospheric conditions. ISS motion through Earth s magnetic field creates an addition inductive voltage up to 20 positive and negative volts across ISS structure depending on its attitude and location in orbit. ISS Visiting Vehicles (VVs), such as the planned Orion crew exploration vehicle, contribute to the ISS plasma charging processes. Upon physical contact with ISS, the current collection properties of VVs combine with ISS. This is an ISS integration concern as FP must be controlled to minimize arcing of ISS surfaces and ensure proper management of extra vehicular activity crewman shock hazards. This report is an assessment of ISS induced charging from docked Orion vehicles employing negatively grounded, 130 volt class, UltraFlex (ATK Space Systems) solar arrays. To assess plasma electron current collection characteristics, Orion solar cell test coupons were constructed and subjected to plasma chamber current collection measurements. During these tests, coupon solar cells were biased between 0 and 120 V while immersed in a simulated LEO plasma. Tests were performed using several different simulated LEO plasma densities and temperatures. These data and associated theoretical scaling of plasma properties, were combined in a numerical model which was integrated into the Boeing Plasma Interaction Model. It was found that the solar array design for Orion will not affect the ISS FP by more than about 2 V during worst case charging conditions. This assessment also motivated a trade study to determine
Longitudinal holes in debunched particle beams in storage rings, perpetuated by space-charge forces
Directory of Open Access Journals (Sweden)
Shane Koscielniak
2001-04-01
Full Text Available Stationary, self-consistent, and localized longitudinal density perturbations on an unbunched charged-particle beam, which are solutions of the nonlinearized Vlasov-Poisson equation, have recently received some attention. In particular, we address the case that space charge is the dominant longitudinal impedance and the storage ring operates below transition energy so that the negative mass instability is not an explanation for persistent beam structure. Under the customary assumption of a bell-shaped steady-state distribution, about which the expansion is made, the usual wave theory of Keil and Schnell for perturbations on unbunched beams predicts that self-sustaining perturbations are possible only (below transition if the impedance is inductive (or resistive or if the bell shape is inverted. Space charge gives a capacitive impedance. Nevertheless, we report numerous experimental measurements made at the CERN Proton Synchrotron Booster that plainly show the longevity of holelike structures in coasting beams. We shall also report on computer simulations of boosterlike beams that provide compelling evidence that it is space-charge force which perpetuates the holes. We shall show that the localized solitonlike structures, i.e., holes, decouple from the steady-state distribution and that they are simple solutions of the nonlinearized time-independent Vlasov equation. We have derived conditions for stationarity of holes that satisfy the requirement of self-consistency; essentially, the relation between the momentum spread and depth of the holes is given by the Hamiltonian—with the constraint that the phase-space density be high enough to support the solitons. The stationarity conditions have scaling laws similar to the Keil-Schnell criteria except that the charge and momentum spread of the hole replaces that of the beam.
Semi-analytic variable charge solitary waves involving dust phase-space vortices (holes)
Energy Technology Data Exchange (ETDEWEB)
Tribeche, Mouloud; Younsi, Smain; Amour, Rabia; Aoutou, Kamel [Plasma Physics Group, Faculty of Sciences-Physics, Theoretical Physics Laboratory, University of Bab-Ezzouar, USTHB BP 32, El Alia, Algiers 16111 (Algeria)], E-mail: mtribeche@usthb.dz
2009-09-15
A semi-analytic model for highly nonlinear solitary waves involving dust phase-space vortices (holes) is outlined. The variable dust charge is expressed in terms of the Lambert function and we take advantage of this transcendental function to investigate the localized structures that may occur in a dusty plasma with variable charge trapped dust particles. Our results which complement the previously published work on this problem (Schamel et al 2001 Phys. Plasmas 8 671) should be of basic interest for experiments that involve the trapping of dust particles in ultra-low-frequency dust acoustic modes.
Semi-analytic variable charge solitary waves involving dust phase-space vortices (holes)
International Nuclear Information System (INIS)
Tribeche, Mouloud; Younsi, Smain; Amour, Rabia; Aoutou, Kamel
2009-01-01
A semi-analytic model for highly nonlinear solitary waves involving dust phase-space vortices (holes) is outlined. The variable dust charge is expressed in terms of the Lambert function and we take advantage of this transcendental function to investigate the localized structures that may occur in a dusty plasma with variable charge trapped dust particles. Our results which complement the previously published work on this problem (Schamel et al 2001 Phys. Plasmas 8 671) should be of basic interest for experiments that involve the trapping of dust particles in ultra-low-frequency dust acoustic modes.
Aberration of a negative ion beam caused by space charge effect.
Miyamoto, K; Wada, S; Hatayama, A
2010-02-01
Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.
Aberration of a negative ion beam caused by space charge effect
International Nuclear Information System (INIS)
Miyamoto, K.; Wada, S.; Hatayama, A.
2010-01-01
Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.
Aberration of a negative ion beam caused by space charge effect
Energy Technology Data Exchange (ETDEWEB)
Miyamoto, K. [Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan); Wada, S.; Hatayama, A. [Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)
2010-02-15
Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.
Chaos in charged AdS black hole extended phase space
Chabab, M.; El Moumni, H.; Iraoui, S.; Masmar, K.; Zhizeh, S.
2018-06-01
We present an analytical study of chaos in a charged black hole in the extended phase space in the context of the Poincare-Melnikov theory. Along with some background on dynamical systems, we compute the relevant Melnikov function and find its zeros. Then we analyse these zeros either to identify the temporal chaos in the spinodal region, or to observe spatial chaos in the small/large black hole equilibrium configuration. As a byproduct, we derive a constraint on the Black hole' charge required to produce chaotic behaviour. To the best of our knowledge, this is the first endeavour to understand the correlation between chaos and phase picture in black holes.
Energy Technology Data Exchange (ETDEWEB)
Chen, Ye; Gjonaj, Erion; Weiland, Thomas [TEMF, Technische Universitaet Darmstadt, Schlossgartenstrasse 8, 64289 Darmstadt (Germany)
2015-07-01
The physics of the photoemission, as one of the key issues for successful operation of linac based free-electron lasers like the European X-ray Free Electron Laser (E-XFEL) and the Free-electron Laser in Hamburg (FLASH), is playing an increasingly important role in the high brightness DESY-PITZ electron source. We study photoemission physics and discuss full three-dimensional numerical modeling of the electron bunch emission. The beam extraction dynamics at the photocathode has been investigated through the 3D fully electromagnetic (EM) Particle-in-Cell (PIC) solver of CST Particle Studio under the assumption of the photoemission source operating at or close to its space charge limit. PIC simulation results have shown good agreements with measurements on total emitted bunch charge for distinct experimental parameters. Further comparisons showed a general failure for the conventional Poisson solver based tracking algorithm to correctly predict the beam dynamics at the space charge limit. It is furthermore found, that fully EM PIC simulations are also consistent with a simple emission model based on the multidimensional Child-Langmuir law.
de Graaf, S E; Leppäkangas, J; Adamyan, A; Danilov, A V; Lindström, T; Fogelström, M; Bauch, T; Johansson, G; Kubatkin, S E
2013-09-27
We study a superconducting charge qubit coupled to an intensive electromagnetic field and probe changes in the resonance frequency of the formed dressed states. At large driving strengths, exceeding the qubit energy-level splitting, this reveals the well known Landau-Zener-Stückelberg interference structure of a longitudinally driven two-level system. For even stronger drives, we observe a significant change in the Landau-Zener-Stückelberg pattern and contrast. We attribute this to photon-assisted quasiparticle tunneling in the qubit. This results in the recovery of the qubit parity, eliminating effects of quasiparticle poisoning, and leads to an enhanced interferometric response. The interference pattern becomes robust to quasiparticle poisoning and has a good potential for accurate charge sensing.
Directory of Open Access Journals (Sweden)
Cristina Stancu
2009-10-01
Full Text Available A computation method of the electricfield and ionic space charge density in planeinsulations with water trees (using a ComsolMultiphysics software and the thermal step currents(Im(t measured with Thermal Step Method ispresented. A parabolic spatial variation of volumecharge density, an exponential spatial variation ofthe electric permittivity ε and a linear dependency ofε and the temperature coefficient of permittivity αεwith the average water concentration in trees, areconsidered. For a water tree with a known length,different values of charge density are consideredand the electric field and the thermal step currentsIc(t are calculated. The currents Ic(t and Im(t arecompared and the volume of charge density andelectric field for which Ic(t is identical with Im(t arekept.
Electromagnetic Detection of a Perfect Invisibility Cloak
International Nuclear Information System (INIS)
Zhang Baile; Wu, Bae-Ian
2009-01-01
A perfect invisibility cloak is commonly believed to be undetectable from electromagnetic (EM) detection because it is equivalent to a curved but empty EM space created from coordinate transformation. Based on the intrinsic asymmetry of coordinate transformation applied to motions of photons and charges, we propose a method to detect this curved EM space by shooting a fast-moving charged particle through it. A broadband radiation generated in this process makes a cloak visible. Our method is the only known EM mechanism so far to detect an ideal perfect cloak (curved EM space) within its working band.
Directory of Open Access Journals (Sweden)
C. A. Valerio-Lizarraga
2018-03-01
Full Text Available The need to extract the maximum beam intensity with low transversal emittance often comes with the drawback of operating the ion source to limits where beam current instabilities arise, such fluctuations can change the beam properties producing a mismatch in the following sections of the machine. The space charge compensation (SCC generated by the beam particles colliding with the residual gas reaches a steady state after a build-up time. This paper shows how once in the steady state, the beam ends with a transversal emittance value bigger than the case without compensation. In addition, we study how the beam intensity variation can disturb the SCC dynamics and its impact on the beam properties. The results presented in this work come from 3-D simulations using tracking codes taking into account the secondary ions to estimate the degree of the emittance growth due to space charge and SCC.
PATH: a lumped-element beam-transport simulation program with space charge
International Nuclear Information System (INIS)
Farrell, J.A.
1983-01-01
PATH is a group of computer programs for simulating charged-particle beam-transport systems. It was developed for evaluating the effects of some aberrations without a time-consuming integration of trajectories through the system. The beam-transport portion of PATH is derived from the well-known program, DECAY TURTLE. PATH contains all features available in DECAY TURTLE (including the input format) plus additional features such as a more flexible random-ray generator, longitudinal phase space, some additional beamline elements, and space-charge routines. One of the programs also provides a simulation of an Alvarez linear accelerator. The programs, originally written for a CDC 7600 computer system, also are available on a VAX-VMS system. All of the programs are interactive with input prompting for ease of use
Space-charge calculation for bunched beams with 3-D ellipsoidal symmetry
International Nuclear Information System (INIS)
Garnett, R.W.; Wangler, T.P.
1991-01-01
A method for calculating 3-D space-charge forces has been developed that is suitable for bunched beams of either ions or relativistic electrons. The method is based on the analytic relations between charge-density and electric fields for a distribution with 3-D ellipsoidal symmetry in real space. At each step we use a Fourier-series representation for the smooth particle-density function obtained from the distribution of the macroparticles being tracked through the elements of the system. The resulting smooth electric fields reduce the problem of noise from artificial collisions, associated with small numbers of interacting macroparticles. Example calculations will be shown for comparison with other methods. 4 refs., 2 figs., 1 tab
Effect of nonuniform radial density distribution on the space charge dominated beam bunching
International Nuclear Information System (INIS)
Sing Babu, P.; Goswami, A.; Pandit, V. S.
2011-01-01
Beam dynamics of a space charge dominated beam during the bunch compression is studied self consistently for the case of fixed shape non-uniform bell shape and hollow shape density distributions in the transverse direction. We have used thick slices at different parts of the beam to account for variation in the beam radius in the study of the transverse dynamics. The longitudinal dynamics has been studied using the disc model. The axial variation of the radius of the slices and emittance growth arising from the phase dependence of the transverse rf forces are also included in the simulation. We have modified the beam envelope equation to take into account the longitudinal space charge effect on the transverse motion which arises due to the finite bunch size. To demonstrate the application of the theoretical formulations developed, we have studied a sinusoidal beam bunching system and presented detailed numerical results.
Numerical simulation of amplification of space charge waves in n-InP films
International Nuclear Information System (INIS)
Garcia-Barrientos, Abel; Palankovski, Vassil
2011-01-01
The non-linear interaction of space charge waves including the amplification in microwave and millimeter wave range in n-InP films, possessing the negative differential conductance phenomenon, is investigated theoretically. Both the amplified signal and the generation of harmonics of the input signal are demonstrated, which are due to non-linear effect of the negative differential resistance. It is possible to observe an amplification of the space charge waves in n-InP films of submicron thicknesses at essentially higher frequencies f <70 GHz, when compared with n-GaAs films f < 44 GHz. The increment observed in the gain is due to the larger dynamic range in n-InP than in n-GaAs films.
Numerical Study of Three Dimensional Effects in Longitudinal Space-Charge Impedance
Energy Technology Data Exchange (ETDEWEB)
Halavanau, A. [NICADD, DeKalb; Piot, P. [NICADD, DeKalb
2015-06-01
Longitudinal space-charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed instabilities. Such “microbunching instabilities” were recently shown to be potentially useful to support the generation of broadband coherent radiation pulses [1, 2]. Therefore there has been an increasing interest in devising accelerator beamlines capable of sustaining this LSC instability as a mechanism to produce a coherent light source. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. In this paper we use a N-body “Barnes-Hut” algorithm [3] to simulate the 3D space charge force in the beam combined with elegant [4] and explore the limitation of the 1D model often used
Enhanced ionic conductivity in composite materials due to interfacial space charge layers
International Nuclear Information System (INIS)
Dudney, N.J.
1985-01-01
The ionic conductivity of a number of salts (e.g., β-AgI, LiI, CuCl, HgI 2 , etc.) can be enhanced by one to three orders of magnitude with the addition of fine particles of an insoluble and nonconducting material such as Al 2 O 3 or SiO 2 . Typically the conductivity increases with addition of the inert particles and reaches a peak at 10-40 vol % of the particles. The mechanism responsible for the enhanced conductivity of the composite is not understood at this time. Some claim that this effect is due to an increased concentration of charge carriers in a diffuse space charge layer near the charged surface of the particle. The goal of the present study is to test this proposed mechanism by calculating the maximum space charge layer effect and then using this result to estimate the conductivity of a composite with a random distribution of Al 2 O 3 particles. Also, the conductivity of composite systems has been investigated assuming an ordered distribution of particles which are surrounded by a high conductivity layer
Electromagnetic weather in the near-earth space in dependence on solar wind parameters
International Nuclear Information System (INIS)
Belov, B.A.; Burtsev, Yu.A.; Dremukhina, L.A.; Papitashvili, V.O.
1995-01-01
Analysis of modern models of electrical and magnetic fields, electrical current and plasma convection is carried out with the purpose of quantitative description of the near-earth electrodynamic parameters. Possibility of utilizing such models simultaneously with radar and geomagnetic observations for continuous real time control of electromagnetic weather in the earth magnetosphere is considered. Refs. 24, refs. 3
Electromagnetic interferometry in wavenumber and space domains in a layered earth
Hunziker, J.W.; Slob, E.C.; Fan, Y.; Snieder, R.; Wapenaar, C.P.A.
2013-01-01
With interferometry applied to controlled-source electromagnetic data, the direct field and the airwave and all other effects related to the air-water interface can be suppressed in a data-driven way. Interferometry allows for retreival of the scattered field Green’s function of the subsurface or,
Berberyan, A. Kh; Garakov, V. G.
2018-04-01
A large number of works have been devoted to investigation of the influence of the piezoelectric properties of a material on the propagation of elastic waves [1–3]. Herewith, the quasi-static piezoelasticity model was mainly used. In the problem of an electromagnetic wave reflection from an elastic medium with piezoelectric properties, it is necessary to consider hyperbolic equations [4].
A multislit transverse-emittance diagnostic for space-charge-dominated electron beams
International Nuclear Information System (INIS)
Piot, P.; Song, J.; Li, R.
1997-01-01
Jefferson Lab is developing a 10 MeV injector to provide an electron beam for a high-power free-electron laser (FEL). To characterize the transverse phase space of the space-charged-dominated beam produced by this injector, the authors designed an interceptive multislit emittance diagnostic. It incorporates an algorithm for phase-space reconstruction and subsequent calculation of the Twiss parameters and emittance for both transverse directions at an update rate exceeding 1 Hz, a speed that will facilitate the transverse-phase-space matching between the injector and the FEL's accelerator that is critical for proper operation. This paper describes issues pertaining to the diagnostic's design. It also discusses the acquisition system, as well as the software algorithm and its implementation in the FEL control system. First results obtained from testing this diagnostic in Jefferson Lab's Injector Test Stand are also included
Space Charge Saturated Sheath Regime and Electron Temperature Saturation in Hall Thrusters
International Nuclear Information System (INIS)
Raitses, Y.; Staack, D.; Smirnov, A.; Fisch, N.J.
2005-01-01
Secondary electron emission in Hall thrusters is predicted to lead to space charge saturated wall sheaths resulting in enhanced power losses in the thruster channel. Analysis of experimentally obtained electron-wall collision frequency suggests that the electron temperature saturation, which occurs at high discharge voltages, appears to be caused by a decrease of the Joule heating rather than by the enhancement of the electron energy loss at the walls due to a strong secondary electron emission
Bifurcation of space-charge wave in a plasma waveguide including the wake potential effect
Energy Technology Data Exchange (ETDEWEB)
Lee, Myoung-Jae [Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 04763 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588, South Korea and Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States)
2016-09-15
The wake potential effects on the propagation of the space-charge dust ion-acoustic wave are investigated in a cylindrically bounded dusty plasma with the ion flow. The results show that the wake potential would generate the double frequency modes in a cylindrically bounded dusty plasma. It is found that the upper mode of the wave frequency with the root of higher-order is smaller than that with the root of lower-order in intermediate wave number domains. However, the lower mode of the scaled wave frequency with the root of higher-order is found to be greater than that with the root of lower-order. It is found that the influence in the order of the root of the Bessel function on the wave frequency of the space-charge dust-ion-acoustic wave in a cylindrically confined dusty plasma decreases with an increase in the propagation wave number. It is also found that the double frequency modes increase with increasing Mach number due to the ion flow in a cylindrical dusty plasma. In addition, it is found that the upper mode of the group velocity decreases with an increase in the scaled radius of the plasma cylinder. However, it is shown that the lower mode of the scaled group velocity of the space-charge dust ion acoustic wave increases with an increase in the radius of the plasma cylinder. The variation of the space-charge dust-ion-acoustic wave due to the wake potential and geometric effects is also discussed.
Study on discrete space charge effects in electron beams and guns
International Nuclear Information System (INIS)
Tang Tiantong
1990-01-01
The discrete space charge effects in electron beams are studied and a statistical dynamics equation of the ensemble of beam electrons is derived. An approximated analytical solution of this equation is given. This equation has been applied to beam crossover and field-emission and thermal-emission gun problems. The computer calculation results agree on the whole with those of Monte Carlo simulation and experimental data. (orig.)
An integrodifferential Dirac equation with quantized charge in one space dimension
International Nuclear Information System (INIS)
Ranada, A.F.
1985-01-01
An integrodifferential Dirac equation in one space dimension is proposed, such that there is a close correspondence between its solutions and a subset of those of the sine-Gordon equation. It has solitonic solutions, quantized charge and positive definite energy density, so that it can be considered a spinorial version of sine-Gordon. Accordingly, it could be named the sine-Dirac equation. (orig.)
Space charge and wake field analysis for a high brightness electron source
International Nuclear Information System (INIS)
Parsa, Z.
1991-01-01
We present a brief overview of the formalism used, and some simulation results for transverse and longitudinal motion of a bunch of particles moving through a cavity (e.g., the Brookhaven National Laboratory high brightness photocathode gun), including effects of the accelerating field, space charge forces (e.g., arising from the interaction of the cavity surface and the self field of the bunch). 3 refs., 12 figs
Space-charge effects in the Fermilab Main Ring at 8 GeV
International Nuclear Information System (INIS)
Mane, S.R.
1989-03-01
I use computer tracking to investigate the effects of space-charge on particle motion in the Fermilab Main Ring at p = 8 GeV/c. The results are found to agree with the Laslett tuneshift formula. Simple model cases are also studied to speed up the tracking. The effects of synchrotron oscillations, via tune modulation and dispersion, are included. 2 refs., 5 figs
PIC space-charge emission with finite Δt and Δz
International Nuclear Information System (INIS)
Hewett, D.W.; Chen, Yu-Jiuan.
1993-01-01
A new algorithm for space charge emission has been developed to provide the correct (to a few percent) Child-Langmuir steady-state current limits as the number of mesh points in the voltage gap drops to O(10). Further, the transient behavior of such flows compares well with idealized, analytic cases, lending confidence as we extend these algorithms into full RZ geometry with curved emitting surfaces to investigate transient characteristics of realistic injector designs
Carbon Nanotube/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation
Smith, J. G., Jr.; Watson, K. A.; Thompson, C. M.; Connell, J. W.
2002-01-01
Low solar absorptivity, space environmentally stable polymeric materials possessing sufficient electrical conductivity for electrostatic charge dissipation (ESD) are of interest for potential applications on spacecraft as thin film membranes on antennas, solar sails, large lightweight space optics, and second surface mirrors. One method of imparting electrical conductivity while maintaining low solar absorptivity is through the use of single wall carbon nanotubes (SWNTs). However, SWNTs are difficult to disperse. Several preparative methods were employed to disperse SWNTs into the polymer matrix. Several examples possessed electrical conductivity sufficient for ESD. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.
Optical method for mapping the transverse phase space of a charged particle beam
International Nuclear Information System (INIS)
Fiorito, R.B.; Shkvarunets, A.G.; O'Shea, P.G.
2002-01-01
We are developing an all optical method to map the transverse phase space map of a charged particle beam. Our technique employs OTR interferometry (OTRI) in combination with a scanning pinhole to make local orthogonal (x,y) divergence and trajectory angle measurements as function of position within the transverse profile of the beam. The localized data allows a reconstruction of the horizontal and vertical phase spaces of the beam. We have also demonstrated how single and multiple pinholes can in principle be used to make such measurements simultaneously
Spinorial charges and their role in the fusion of internal and space-time symmetries
International Nuclear Information System (INIS)
Daniel, M.; Ktorides, C.N.
1976-01-01
The advent of supersymmetry immediately led to speculations that a non-trivial mixing of internal and space-time symmetries could be achieved within its framework. In fact, the well-known no-go theorems do not apply to the supersymmetry algebra due to the presence, in the latter, of (anticommuting) spinorial charges. However, not until the recent work of Haag, Lopuszanski and Sohnius did a clearcut picture emerge as to how the aforementioned nontrivial mixing can take place. Most notably, the presence of the conformal algebra within the supersymmetry algebra turns out to be vital. The findings of Haag et al. are solidified through an explicit construction which uses as underlying space the pseudo-Euclidean space E(4, 2), i.e. the space for which the conformal group is the group of rotations, and which employs as main tools the spinors associated with the space E(4, 2). The algebro-geometric approach of Cartan is followed in order to understand both the introduction and the properties of these spinors. In this manner, many insights are gained regarding the mathematical foundations of supersymmetry. Thus, the emergence of the anticommutator, rather than the commutator, among spinor charges is fully understood as a natural algebraic consequence and not as an a priori given fact. In addition, it is clearly seen how an (internal) unitary symmetry group can make its appearance within the supersymmetry scheme and verify, via this explicit construction, the results of Haag et al. (Auth.)
Seckler, Tobias; Jagielski, Kai; Stunder, Dominik
2015-05-27
Electromagnetic interference is a concern for people wearing cardiovascular implantable electronic devices (CIEDs). The aim of this study was to assess the electromagnetic compatibility between CIEDs and the magnetic field of a common wireless charging technology. To do so the voltage induced in CIEDs by Qi A13 design magnetic fields were measured and compared with the performance limits set by ISO 14117. In order to carry this out a measuring circuit was developed which can be connected with unipolar or bipolar pacemaker leads. The measuring system was positioned at the four most common implantation sites in a torso phantom filled with physiological saline solution. The phantom was exposed by using Helmholtz coils from 5 µT to 27 µT with 111 kHz sine‑bursts or by using a Qi A13 design wireless charging board (Qi‑A13‑Board) in two operating modes "power transfer" and "pinging". With the Helmholtz coils the lowest magnetic flux density at which the performance limit was exceeded is 11 µT. With the Qi‑A13‑Board in power transfer mode 10.8% and in pinging mode 45.7% (2.2% at 10 cm distance) of the performance limit were reached at maximum. In neither of the scrutinized cases, did the voltage induced by the Qi‑A13‑Board exceed the performance limits.
Zhang, Xi-Cheng; Riordan, Jenifer Ann; Sun, Feng-Guo
2000-08-29
Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric (or magnetic) field and a laser beam in an electro-optic (or magnetic-optic) crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field-optical beam interaction length, thereby making imaging applications practical.
International Nuclear Information System (INIS)
Sugaya, Reija
1991-01-01
The velocity-space diffusion equation describing distortion of the velocity distribution function due to resonant wave-wave scattering of electromagnetic and electrostatic waves in an unmagnetized plasma is derived from the Vlasov-Maxwell equations by perturbation theory. The conservation laws for total energy and momentum densities of waves and particles are verified, and the time evolutions of the energy and momentum densities of particles are given in terms of the nonlinear wave-wave coupling coefficient in the kinetic wave equation. (author)
Yu, Lei; Li, Haibo; Wan, Weishi; Wei, Zheng; Grzelakowski, Krzysztof P; Tromp, Rudolf M; Tang, Wen-Xin
2017-12-01
The effects of space charge, aberrations and relativity on temporal compression are investigated for a compact spherical electrostatic capacitor (α-SDA). By employing the three-dimensional (3D) field simulation and the 3D space charge model based on numerical General Particle Tracer and SIMION, we map the compression efficiency for a wide range of initial beam size and single-pulse electron number and determine the optimum conditions of electron pulses for the most effective compression. The results demonstrate that both space charge effects and aberrations prevent the compression of electron pulses into the sub-ps region if the electron number and the beam size are not properly optimized. Our results suggest that α-SDA is an effective compression approach for electron pulses under the optimum conditions. It may serve as a potential key component in designing future time-resolved electron sources for electron diffraction and spectroscopy experiments. Copyright © 2017 Elsevier B.V. All rights reserved.
Studies on space charge neutralization and emittance measurement of beam from microwave ion source
Energy Technology Data Exchange (ETDEWEB)
Misra, Anuraag; Goswami, A.; Sing Babu, P.; Srivastava, S.; Pandit, V. S., E-mail: pandit@vecc.gov.in, E-mail: vspandit12@gmail.com [Variable Energy Cyclotron Centre, 1-AF, Bidhannagar, Kolkata 700 064 (India)
2015-11-15
A 2.45 GHz microwave ion source together with a beam transport system has been developed at VECC to study the problems related with the injection of high current beam into a compact cyclotron. This paper presents the results of beam profile measurement of high current proton beam at different degrees of space charge neutralisation with the introduction of neon gas in the beam line using a fine leak valve. The beam profiles have been measured at different pressures in the beam line by capturing the residual gas fluorescence using a CCD camera. It has been found that with space charge compensation at the present current level (∼5 mA at 75 keV), it is possible to reduce the beam spot size by ∼34%. We have measured the variation of beam profile as a function of the current in the solenoid magnet under the neutralised condition and used these data to estimate the rms emittance of the beam. Simulations performed using equivalent Kapchinsky-Vladimirsky beam envelope equations with space charge neutralization factor are also presented to interpret the experimental results.
A Self Consistent Multiprocessor Space Charge Algorithm that is Almost Embarrassingly Parallel
International Nuclear Information System (INIS)
Nissen, Edward; Erdelyi, B.; Manikonda, S.L.
2012-01-01
We present a space charge code that is self consistent, massively parallelizeable, and requires very little communication between computer nodes; making the calculation almost embarrassingly parallel. This method is implemented in the code COSY Infinity where the differential algebras used in this code are important to the algorithm's proper functioning. The method works by calculating the self consistent space charge distribution using the statistical moments of the test particles, and converting them into polynomial series coefficients. These coefficients are combined with differential algebraic integrals to form the potential, and electric fields. The result is a map which contains the effects of space charge. This method allows for massive parallelization since its statistics based solver doesn't require any binning of particles, and only requires a vector containing the partial sums of the statistical moments for the different nodes to be passed. All other calculations are done independently. The resulting maps can be used to analyze the system using normal form analysis, as well as advance particles in numbers and at speeds that were previously impossible.
Numerical analysis of ion wind flow using space charge for optimal design
Ko, Han Seo; Shin, Dong Ho; Baek, Soo Hong
2014-11-01
Ion wind flow has been widly studied for its advantages of a micro fluidic device. However, it is very difficult to predict the performance of the ion wind flow for various conditions because of its complicated electrohydrodynamic phenomena. Thus, a reliable numerical modeling is required to design an otimal ion wind generator and calculate velocity of the ion wind for the proper performance. In this study, the numerical modeling of the ion wind has been modified and newly defined to calculate the veloctiy of the ion wind flow by combining three basic models such as electrostatics, electrodynamics and fluid dynamics. The model has included presence of initial space charges to calculate transfer energy between space charges and air gas molecules using a developed space charge correlation. The simulation has been performed for a geometry of a pin to parallel plate electrode. Finally, the results of the simulation have been compared with the experimental data for the ion wind velocity to confirm the accuracy of the modified numerical modeling and to obtain the optimal design of the ion wind generator. This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean government (MEST) (No. 2013R1A2A2A01068653).
Transition from Fowler-Nordheim field emission to space charge limited current density
International Nuclear Information System (INIS)
Feng, Y.; Verboncoeur, J. P.
2006-01-01
The Fowler-Nordheim law gives the current density extracted from a surface under strong fields, by treating the emission of electrons from a metal-vacuum interface in the presence of an electric field normal to the surface as a quantum mechanical tunneling process. Child's law predicts the maximum transmitted current density by considering the space charge effect. When the electric field becomes high enough, the emitted current density will be limited by Child's law. This work analyzes the transition of the transmitted current density from the Fowler-Nordheim law to Child's law space charge limit using a one-dimensional particle-in-cell code. Also studied is the response of the emission model to strong electric fields near the transition point. We find the transition without geometrical effort is smooth and much slower than reported previously [J. P. Barbour, W. W. Dolan, J. K. Trolan, E. E. Martin, and W. P. Dyke, Phys. Rev. 92, 45 (1953)]. We analyze the effects of geometric field enhancement and work function on the transition. Using our previous model for effective field enhancement [Y. Feng and J. P. Verboncoeur, Phys. Plasmas 12, 103301 (2005)], we find the geometric effect dominates, and enhancement β>10 can accelerate the approach to the space charge limit at practical electric field. A damped oscillation near the local plasma frequency is observed in the transient system response
International Nuclear Information System (INIS)
Yoon, Sangcheol; Hwang, Inchan; Park, Byoungchoo
2015-01-01
The loss of photocurrent efficiency by space-charge effects in organic solar cells with energetic disorder was investigated to account for how energetic disorder incorporates space-charge effects, utilizing a drift-diffusion model with field-dependent charge-pair dissociation and suppressed bimolecular recombination. Energetic disorder, which induces the Poole–Frenkel behavior of charge carrier mobility, is known to decrease the mobility of charge carriers and thus reduces photovoltaic performance. We found that even if the mobilities are the same in the absence of space-charge effects, the degree of energetic disorder can be an additional parameter affecting photocurrent efficiency when space-charge effects occur. Introducing the field-dependence parameter that reflects the energetic disorder, the behavior of efficiency loss with energetic disorder can differ depending on which charge carrier is subject to energetic disorder. While the energetic disorder that is applied to higher-mobility charge carriers decreases photocurrent efficiency further, the efficiency loss can be suppressed when energetic disorder is applied to lower-mobility charge carriers. (paper)
Xu, Guangwei; Gao, Nan; Lu, Congyan; Wang, Wei; Ji, Zhuoyu; Bi, Chong; Han, Zhiheng; Lu, Nianduan; Yang, Guanhua; Li, Yuan; Liu, Qi; Li, Ling; Liu, Ming
2018-01-01
, the charge transport properties of organic diodes are usually characterized by probing the current–voltage (I–V) curves of the devices. However, to unveil the landscape of the underlying potential/charge distribution, which essentially determines the I
Energy Technology Data Exchange (ETDEWEB)
Anaguano, L.
2005-07-01
According to the theory of Quantum Electrodynamics (QED) the vacuum state will change in the presence of very strong electromagnetic fields. If the external field (in the simplest case purely electrostatic) exceeds a certain critical value the creation of electron-positron pairs will ensue, resulting the the formation of a charged vacuum. This process is characterized by the emergence of electron states with a binding energy larger than twice the electron rest mass. The effect up to now usually was studied for spherically symmetric systems, in particular for the Coulomb potential of a heavy nucleus. In the present thesis we investigate, how this phenomenon changes when passing from spherical to cylindrical geometry. For this, we derive the solutions of the Dirac equation for electrons in the electrostatic potential of a long, thin charged cylinder (a ''charged string'') and study the ensuing supercritical effects. Since the logarithmic potential of an infinitely long string rises indefinitely with growing distance, all electron states should be supercritical (i.e., electrons should be able to tunnel through the particle-antiparticle gap of the Dirac equation). Therefore on may expect that the central charge will surround itself with an oppositely charged sheath of vacuum electrons, leading to neutralization of the string. To develop a quantitative description of this process, we investigate the solutions of the Poisson equation and the Dirac equation in cylindrical symmetry. In the first step a series expansion of the electrostatic potential in the central plane of a homogeneously charge cylinder of finite length and finite radius is derived. Subsequently, we employ the tetrad (vierbein) formalism to separate the Dirac equation in cylindrical coordinates. The resulting radial Dirac equation is transformed to Schroedinger type. The bound states are evaluated using the method of uniform approximation (a version of the WKB approximation). We study
Extraction of space-charge-dominated ion beams from an ECR ion source: Theory and simulation
Alton, G. D.; Bilheux, H.
2004-05-01
Extraction of high quality space-charge-dominated ion beams from plasma ion sources constitutes an optimization problem centered about finding an optimal concave plasma emission boundary that minimizes half-angular divergence for a given charge state, independent of the presence or lack thereof of a magnetic field in the extraction region. The curvature of the emission boundary acts to converge/diverge the low velocity beam during extraction. Beams of highest quality are extracted whenever the half-angular divergence, ω, is minimized. Under minimum half-angular divergence conditions, the plasma emission boundary has an optimum curvature and the perveance, P, current density, j+ext, and extraction gap, d, have optimum values for a given charge state, q. Optimum values for each of the independent variables (P, j+ext and d) are found to be in close agreement with those derived from elementary analytical theory for extraction with a simple two-electrode extraction system, independent of the presence of a magnetic field. The magnetic field only increases the emittances of beams through additional aberrational effects caused by increased angular divergences through coupling of the longitudinal to the transverse velocity components of particles as they pass though the mirror region of the electron cyclotron resonance (ECR) ion source. This article reviews the underlying theory of elementary extraction optics and presents results derived from simulation studies of extraction of space-charge dominated heavy-ion beams of varying mass, charge state, and intensity from an ECR ion source with emphasis on magnetic field induced effects.
Extraction of space-charge-dominated ion beams from an ECR ion source: Theory and simulation
International Nuclear Information System (INIS)
Alton, G.D.; Bilheux, H.
2004-01-01
Extraction of high quality space-charge-dominated ion beams from plasma ion sources constitutes an optimization problem centered about finding an optimal concave plasma emission boundary that minimizes half-angular divergence for a given charge state, independent of the presence or lack thereof of a magnetic field in the extraction region. The curvature of the emission boundary acts to converge/diverge the low velocity beam during extraction. Beams of highest quality are extracted whenever the half-angular divergence, ω, is minimized. Under minimum half-angular divergence conditions, the plasma emission boundary has an optimum curvature and the perveance, P, current density, j +ext , and extraction gap, d, have optimum values for a given charge state, q. Optimum values for each of the independent variables (P, j +ext and d) are found to be in close agreement with those derived from elementary analytical theory for extraction with a simple two-electrode extraction system, independent of the presence of a magnetic field. The magnetic field only increases the emittances of beams through additional aberrational effects caused by increased angular divergences through coupling of the longitudinal to the transverse velocity components of particles as they pass though the mirror region of the electron cyclotron resonance (ECR) ion source. This article reviews the underlying theory of elementary extraction optics and presents results derived from simulation studies of extraction of space-charge dominated heavy-ion beams of varying mass, charge state, and intensity from an ECR ion source with emphasis on magnetic field induced effects
Emittance growth due to static and radiative space charge forces in an electron bunch compressor
Talman, Richard; Malitsky, Nikolay; Stulle, Frank
2009-01-01
Evolution of short intense electron bunches passing through bunch-compressing beam lines is studied using the UAL (Unified Accelerator Libraries) string space charge formulation [R. Talman, Phys. Rev. ST Accel. Beams 7, 100701 (2004)PRABFM1098-440210.1103/PhysRevSTAB.7.100701; N. Malitsky and R. Talman, in Proceedings of the 9th European Particle Accelerator Conference, Lucerne, 2004 (EPS-AG, Lucerne, 2004); R. Talman, Accelerator X-Ray Sources (Wiley-VCH, Weinheim, 2006), Chap. 13]. Three major configurations are studied, with the first most important and studied in greatest detail (because actual experimental results are available and the same results have been simulated with other codes): (i) Experimental bunch compression results were obtained at CTF-II, the CERN test facility for the “Compact Linear Collider” using electrons of about 40 MeV. Previous simulations of these results have been performed (using TraFiC4* [A. Kabel , Nucl. Instrum. Methods Phys. Res., Sect. A 455, 185 (2000)NIMAER0168-900210.1016/S0168-9002(00)00729-4] and ELEGANT [M. Borland, Argonne National Laboratory Report No. LS-287, 2000]). All three simulations are in fair agreement with the data except that the UAL simulation predicts a substantial dependence of horizontal emittance γx on beam width (as controlled by the lattice βx function) at the compressor location. This is consistent with the experimental observations, but inconsistent with other simulations. Excellent agreement concerning dependence of bunch energy loss on bunch length and magnetic field strength [L. Groening , in Proceedings of the Particle Accelerator Conference, Chicago, IL, 2001 (IEEE, New York, 2001), http://groening.home.cern/groening/csr_00.htm] confirms our understanding of the role played by coherent synchrotron radiation (CSR). (ii) A controlled comparison is made between the predictions of the UAL code and those of CSRTrack [M. Dohlus and T. Limberg, in Proceedings of the 2004 FEL Conference, pp. 18
Computer simulations of electromagnetic cool ion beam instabilities. [in near earth space
Gary, S. P.; Madland, C. D.; Schriver, D.; Winske, D.
1986-01-01
Electromagnetic ion beam instabilities driven by cool ion beams at propagation parallel or antiparallel to a uniform magnetic field are studied using computer simulations. The elements of linear theory applicable to electromagnetic ion beam instabilities and the simulations derived from a one-dimensional hybrid computer code are described. The quasi-linear regime of the right-hand resonant ion beam instability, and the gyrophase bunching of the nonlinear regime of the right-hand resonant and nonresonant instabilities are examined. It is detected that in the quasi-linear regime the instability saturation is due to a reduction in the beam core relative drift speed and an increase in the perpendicular-to-parallel beam temperature; in the nonlinear regime the instabilities saturate when half the initial beam drift kinetic energy density is converted to fluctuating magnetic field energy density.
Johnson, Dean L.; Ross, Ronald G., Jr.
1991-01-01
This paper describes the electromagnetic compatibility (EMC) measurements of an 80-K Stirling-cycle cooler. The measurements, performed in the JPL EMC test facility, include dc magnetic field characterization, radiated magnetic and electric field emissions, and conducted emissions on the internal lines between the cooler electronics and the cooler. The measurements conform to both the MILSTD-461C specifications as well as to the specifications for the NASA Earth Observing System.
Electromagnetic diffraction by an impedance cylinder buried halfway between two half-spaces
Salem, Mohamed; Kamel, Aladin Hassan
2011-01-01
We consider the problem of electromagnetic diffraction from a cylinder with impedance surface and half-buried between two dielectric media. An arbitrary located electric dipole provides the excitation. The harmonic solution is presented as a series sum over a spectrum of a discrete-index Hankel transform, and the spectral amplitudes are determined by solving an infinite linear system of equations, which is constructed by applying the orthogonality relation of the 1D Green's function. © 2011 IEEE.
Electromagnetic diffraction by an impedance cylinder buried halfway between two half-spaces
Salem, Mohamed
2011-08-01
We consider the problem of electromagnetic diffraction from a cylinder with impedance surface and half-buried between two dielectric media. An arbitrary located electric dipole provides the excitation. The harmonic solution is presented as a series sum over a spectrum of a discrete-index Hankel transform, and the spectral amplitudes are determined by solving an infinite linear system of equations, which is constructed by applying the orthogonality relation of the 1D Green\\'s function. © 2011 IEEE.
International Nuclear Information System (INIS)
Teyssedre, G.; Laurent, C.; Vu, T. T. N.
2015-01-01
Among features observed in polyethylene materials under relatively high field, space charge packets, consisting in a pulse of net charge that remains in the form of a pulse as it crosses the insulation, are repeatedly observed but without complete theory explaining their formation and propagation. Positive charge packets are more often reported, and the models based on negative differential mobility(NDM) for the transport of holes could account for some charge packets phenomenology. Conversely, NDM for electrons transport has never been reported so far. The present contribution reports space charge measurements by pulsed electroacoustic method on miniature cables that are model of HVDC cables. The measurements were realized at room temperature or with a temperature gradient of 10 °C through the insulation under DC fields on the order 30–60 kV/mm. Space charge results reveal systematic occurrence of a negative front of charges generated at the inner electrode that moves toward the outer electrode at the beginning of the polarization step. It is observed that the transit time of the front of negative charge increases, and therefore the mobility decreases, with the applied voltage. Further, the estimated mobility, in the range 10 −14 –10 −13 m 2 V −1 s −1 for the present results, increases when the temperature increases for the same condition of applied voltage. The features substantiate the hypothesis of negative differential mobility used for modelling space charge packets
Teyssedre, G.; Vu, T. T. N.; Laurent, C.
2015-12-01
Among features observed in polyethylene materials under relatively high field, space charge packets, consisting in a pulse of net charge that remains in the form of a pulse as it crosses the insulation, are repeatedly observed but without complete theory explaining their formation and propagation. Positive charge packets are more often reported, and the models based on negative differential mobility(NDM) for the transport of holes could account for some charge packets phenomenology. Conversely, NDM for electrons transport has never been reported so far. The present contribution reports space charge measurements by pulsed electroacoustic method on miniature cables that are model of HVDC cables. The measurements were realized at room temperature or with a temperature gradient of 10 °C through the insulation under DC fields on the order 30-60 kV/mm. Space charge results reveal systematic occurrence of a negative front of charges generated at the inner electrode that moves toward the outer electrode at the beginning of the polarization step. It is observed that the transit time of the front of negative charge increases, and therefore the mobility decreases, with the applied voltage. Further, the estimated mobility, in the range 10-14-10-13 m2 V-1 s-1 for the present results, increases when the temperature increases for the same condition of applied voltage. The features substantiate the hypothesis of negative differential mobility used for modelling space charge packets.
International Nuclear Information System (INIS)
Zhu Meng; Zhou Hui; Cheng Yinhui; Li Baozhong; Wu Wei; Li Jinxi; Ma Liang; Zhao Mo
2013-01-01
Electromagnetic pulse can be generated by the nuclear detonation in space via two radiation mechanisms. The electric dipole and magnetic dipole models were analyzed. The electric radiation in the far field generated by two models was calculated as well. Investigations show that in the case of one hundred TNT yield detonations, when electrons are emitted according to the Gaussian shape, two radiation models can give rise to the electric field in great distances with amplitudes of kV/m and tens of V/m, independently. Because the geomagnetic field in space is not strong and the electrons' angular motion is much weaker than the motion in the original direction, radiations from the magnetic dipole model are much weaker than those from the electric dipole model. (authors)
Photosensitive space charge limited current in screen printed CdTe thin films
Vyas, C. U.; Pataniya, Pratik; Zankat, Chetan K.; Patel, Alkesh B.; Pathak, V. M.; Patel, K. D.; Solanki, G. K.
2018-05-01
Group II-VI Compounds have emerged out as most suitable in the class of photo sensitive material. They represent a strong position in terms of their applications in the field of detectors as well as photo voltaic devices. Cadmium telluride is the prime member of this Group, because of high acceptance of this material as active component in opto-electronic devices. In this paper we report preparation and characterization of CdTe thin films by using a most economical screen printing technique in association with sintering at 510°C temperature. Surface morphology and smoothness are prime parameters of any deposited to be used as an active region of devices. Thus, we studied of the screen printed thin film by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM) for this purpose. However, growth processes induced intrinsic defects in fabricated films work as charge traps and affect the conduction process significantly. So the conduction mechanism of deposited CdTe thin film is studied under dark as well as illuminated conditions. It is found that the deposited films showed the space charge limited conduction (SCLC) mechanism and hence various parameters of space charge limited conduction (SCLC) of CdTe film were evaluated and discussed and the photo responsive resistance is also presented in this paper.
Space charge compensation on the low energy beam transport of Linac4
AUTHOR|(SzGeCERN)733270; Scrivens, Richard; Jesus Castillo, Santos
Part of the upgrade program in the injector chains of the CERN accelerator complex is the replacement of the the proton accelerator Linac2 for the brand new Linac4 which will accelerate H$^-$ and its main goal is to increase the beam intensity in the next sections of the LHC accelerator chain. The Linac4 is now under commissioning and will use several ion sources to produce high intensity unbunched H$^-$ beams with different properties, and the low energy beam transport (LEBT) is the system in charge of match all these different beams to the Radio frequency quadrupole (RFQ). The space charge forces that spread the beam ions apart of each other and cause emittance growth limits the maximum intensity that can be transported in the LEBT, but the space charge of intense unbunched ion beams can be compensated by the generated ions by the impact ionization of the residual gas, which creates a source of secondary particles inside the beam pipe. For negative ion beams, the effect of the beam electric field is to ex...
Modelling of electric tree progression due to space charge modified fields
International Nuclear Information System (INIS)
Seralathan, K E; Mahajan, A; Gupta, Nandini
2008-01-01
Tree initiation and growth require localized field enhancement that results in material erosion and formation of tree channels. Tree progression is linked to partial discharges within the tree tubules, characterized by recurrent periods of activity followed by quiescent states. Charge builds up across the non-conducting tree channels during the inactive regime, and discharge follows. In this work, the role of the space charge modified field during the non-discharging regime in deciding the site of subsequent discharges and thereby shaping tree structures is studied. A simple stochastic model was developed, in order to understand the respective effects of charges trapped on the walls of tree tubules, at channel tips, or in the volume of the dielectric. While some charge distributions are seen to arrest tree growth, others encourage axial growth towards the other electrode, and some aid in producing bushy trees clustered around the needle tip. The effect of carbon deposition within tree channels, making them effectively conducting, was also investigated. The insights gained from the simulations were successfully used to explain tree growth in the laboratory under high- and low-field conditions
Radiation and Internal Charging Environments for Thin Dielectrics in Interplanetary Space
Minow, Joseph I.; Parker, Linda Neergaard; Altstatt, Richard L.
2004-01-01
Spacecraft designs using solar sails for propulsion or thin membranes to shade instruments from the sun to achieve cryogenic operating temperatures are being considered for a number of missions in the next decades. A common feature of these designs are thin dielectric materials that will be exposed to the solar wind, solar energetic particle events, and the distant magnetotail plasma environments encountered by spacecraft in orbit about the Earth-Sun L2 point. This paper will discuss the relevant radiation and internal charging environments developed to support spacecraft design for both total dose radiation effects as well as dose rate dependent phenomenon, such as internal charging in the solar wind and distant magnetotail environments. We will describe the development of radiation and internal charging environment models based on nearly a complete solar cycle of Ulysses solar wind plasma measurements over a complete range of heliocentric latitudes and the early years of the Geotail mission where distant magnetotail plasma environments were sampled beyond X(sub GSE) = -100 Re to nearly L2 (X(sub GSE) -236 Re). Example applications of the environment models are shown to demonstrate the radiation and internal charging environments of thin materials exposed to the interplanetary space plasma environments.
International Nuclear Information System (INIS)
Shirkov, G.D.
1996-01-01
The Electron Beam Ion Sources (EBIS), Electron Beam Ion Traps (EBIT) and electron beams for electron cooling application have the beam parameters in the same ranges of magnitudes. EBIS and EBIT produce and accumulate ions in the beam due to electron impact ionization. The cooling electron beam accumulates positive ions from the residual gas in the accelerator chamber during the cooling cycle. The space charge neutralization of cooling beam is also used to reduce the electron energy spread and enhance the cooling ability. The advanced results of experimental investigations and theoretical models of the EBIS electron beams are applied to analyze the problem of beam neutralization in the electron cooling techniques. The report presents the analysis of the most important processes connected with ion production, accumulation and losses in the intensive electron beams of ion sources and electron cooling systems for proton and ion colliders. The inelastic and elastic collision processes of charged particles in the electron beams are considered. The inelastic processes such as ionization, charge exchange and recombination change the charge states of ions and neutral atoms in the beam. The elastic Coulomb collisions change the energy of particles and cause the energy redistribution among components in the electron-ion beams. The characteristic times and specific features of ionization, beam neutralization, ion heating and loss in the ion sources and electron cooling beams are determined. The dependence of negative potential in the beam cross section on neutralization factor is studied. 17 refs., 5 figs., 1 tab
Thermal blurring effects on fluctuations of conserved charges in rapidity space
Energy Technology Data Exchange (ETDEWEB)
Asakawa, M.; Kitazawa, M.; Onishi, Y.; Sakaida, M.
2016-12-15
We argue that the diffusion in the hadron phase and the thermal blurring at thermal freezeout affect observed conserved charge fluctuations considerably in relativistic heavy ion collisions, and show that their effects are of similar order at RHIC and LHC, and thus equally important in understanding experimental data. We also argue that, in order to disentangle them and obtain the initial state charge fluctuations, which we are interested in, it is crucial to measure their dependence on the rapidity window size. In the energy range of the beam energy scan program at RHIC, the diffusion effect would be less important because of the shorter duration of the hadron phase, but the importance of thermal blurring is not reduced. In addition, it is necessary to take account of the complex correspondence between the space-time rapidity and rapidity of observed particles, there.
Quadrupole beam-transport experiment for heavy ions under extreme space charge conditions
International Nuclear Information System (INIS)
Chupp, W.; Faltens, A.; Hartwig, E.C.
1983-03-01
A Cs ion-beam-transport experiment is in progress to study beam behavior under extreme space-charge conditions. A five-lens section matches the beam into a periodic electrostatic quadrupole FODO channel and its behavior is found to agree with predictions. With the available parameters (less than or equal to 200 keV, less than or equal to 20 mA, πepsilon/sub n/ greater than or equal to 10 - 7 π rad-m, up to 41 periods) the transverse (betatron) occillation frequency (nu) can be depressed down to one-tenth of its zero current value (nu/sub 0/), where nu/sup 2/ = nu/sub 0//sup 2/ -#betta#/sub p/ 2 /2, and #betta#/sub p/ is the beam plasma frequency. The current can be controlled by adjustment of the gun and the emittance can be controlled independently by means of a set of charged grids
Space distribution and energy straggling of charged particles via Fokker-Planck equation
International Nuclear Information System (INIS)
Manservisi, S.; Molinari, V.; Nespoli, A.
1996-01-01
The Fokker-Planck equation describing a beam of charged particles entering a homogeneous medium is solved here for a stationary case. Interactions are taken into account through Coulomb cross-section. Starting from the charged-particle distribution as a function of velocity and penetration depth, some important kinetic quantities are calculated, like mean velocity, range and the loss of energy per unit space. In such quantities the energy straggling is taken into account. This phenomenon is not considered in the continuous slowing-down approximation that is commonly used to obtain the range and the stopping power. Finally the well-know Bohr of Bethe formula is found as a first-order approximation of the Fokker-Planck equation
Soula, Serge
1994-01-01
The evolution of the vertical electric field profile deduced from simultaneous field measurements at several levels below a thundercloud shows the development of a space charge layer at least up to 600 m. The average charge density in the whole layer from 0 m to 600 m can reach about 1 nC m(exp -3). The ions are generated at the ground by corona effect and the production rate is evaluated with a new method from the comparison of field evolutions at the ground and at altitude after a lightning flash. The modeling of the relevant processes shows tht ground corona accounts for the observed field evolutions and that the aerosol particles concentration has a very large effect on the evolution of corona ions. However, with a realistic value for this concentration a large amount of ground corona ions reach the level of 600 m.
Szymanski, Marek Z.; Kulszewicz-Bajer, Irena; Faure-Vincent, Jérôme; Djurado, David
2012-08-01
We have studied hole transport in triarylamine based dendrimer using space-charge-limited current transient technique. A mobility of 8 × 10-6 cm2/(V s) and a characteristic detrapping time of about 100 ms have been obtained. We found that quasi-ohmic contact is formed with gold. The obtained mobility differs from the apparent one given by the analysis of stationary current-voltage characteristics because of a limited contact efficiency. The comparison between transients obtained from fresh and aged samples reveals no change in mobility with aging. The deterioration of electrical properties is exclusively caused by trap formation and accumulation of ionic conducting impurities. Finally, repeated transient measurements have been applied to analyze the dynamics of charge trapping process.
Theory of accelerated orbits and space charge effects in an AVF cyclotron
International Nuclear Information System (INIS)
Kleeven, W.J.G.M.
1988-01-01
In the first part of this thesis the influence of the accelerating electric field upon the motion of particles in a cyclotron is studied. A general relativistic Hamiltonian theory is derived which allows for a simultaneous study of the transverse and longitudinal motion as well as the coupling between both motions. It includes azimuthally varying magnetic fields and therefore describes phenomena which are due to the interfering influences of a given geometrical dee system with the azimuthally varying part of the magnetic field. As an example the electric gap crossing resonance is treated. The second part deals with space charge effects in a AVF cyclotron. The properties of the bunch, like the sizes, emittances and momentum spread, are represented in terms of second order moments of the phase space distribution function, and two sets of differential equations are derived which describe the time evolution of these moments under space charge conditions. The model takes into account the coupling between the longitudinal and radial motion, and the fact that the revolution frequency of the particles is independent of their energy. The analytical models developed can be applied to a given cyclotron by adopting the relevant parameters. Some calculations are presented for the small 3 MeV Iscochroneous Low Energy Cyclotron ILEC which is presently under construction at the Eindhoven University. Also some attention to the construction of this machine is given. (H.W.). 49 refs.; 37 figs
Space charge calibration of the ALICE TPC operated with an open gating grid
Energy Technology Data Exchange (ETDEWEB)
Hellbaer, Ernst [Institut fuer Kernphysik, Goethe-Universitaet Frankfurt (Germany); Ivanov, Marian [GSI (Germany); Wiechula, Jens [Universitaet Tuebingen (Germany); Collaboration: ALICE-Collaboration
2015-07-01
The Time Projection Chamber (TPC) is the main particle identification detector of the ALICE experiment at the CERN LHC. High interaction rates of 50 kHz in Pb-Pb during the Run 3 period after 2020 require a major upgrade of the TPC readout. The currently used Multiwire Proportional Chambers (MWPCs) will be replaced by readout chambers (ROCs) based on Gas Electron Multiplier (GEM) technology which will be operated in a continuous mode. While the gating grid of the MWPCs prevents the positive ions of the amplification region from entering the drift volume, the GEM-based ROCs will introduce an ion backflow (IBF) of about 1%. In combination with the high-luminosity environment, this amount of back-drifting ions results in a considerable space charge density which distorts the drift path of the primary ionisation electrons significantly. In order to still provide a high tracking efficiency and cluster-to-track association, an efficient calibration scheme will be implemented. As a test ground for the new calibration scheme, pp collision data was taken during Run 1 with the gating grid operated in a transparent mode allowing the ions to enter the drift volume. The measured space point distortions due to the space charge are presented together with the corrected data and compared to simulations for Run 3.
Space-charge limits on the transport of ion beams in a long alternating gradient system
International Nuclear Information System (INIS)
Tiefenback, M.G.
1986-11-01
We have experimentally studied the space-charge-dominated transport of ion beams in an alternating-gradient channel, without acceleration. We parameterize the focusing strength in terms of the zero-current ''betatron'' oscillation phase advance rate, σ 0 (degrees per focusing period). We have investigated the conditions for ''stability'', defined as the constancy of the total current and phase space area of the beam during transport. We find that the beam may be transported with neither loss of current nor growth in phase area if σ 0 0 . In this regime, the space-charge repulsive force can counter 98-99% of the externally applied focusing field, and the oscillation frequency of the beam particles can be depressed by self-forces to almost a factor of 10 below the zero-current value, limited only by the optical quality of our ion source. For σ 0 > 90 0 , we find that collective interactions bound the maintainable density of the beam, and we present a simple, semi-empirical characterization for stability, within our ability to distinguish the growth rate from zero in our apparatus. Our channel comprises 87 quadrupole lenses, 5 of which are used to prepare the beam for injection into the non-azimuthally-symmetric focusing channel
International Nuclear Information System (INIS)
Grunau, Saskia; Kagramanova, Valeria
2011-01-01
We present the full set of analytical solutions of the geodesic equations of charged test particles in the Reissner-Nordstroem space-time in terms of the Weierstrass weierp, σ, and ζ elliptic functions. Based on the study of the polynomials in the θ and r equations, we characterize the motion of test particles and discuss their properties. The motion of charged test particles in the Reissner-Nordstroem space-time is compared with the motion of neutral test particles in the field of a gravitomagnetic monopole. Electrically or magnetically charged particles in the Reissner-Nordstroem space-time with magnetic or electric charges, respectively, move on cones similar to neutral test particles in the Taub-NUT space-times.
International Nuclear Information System (INIS)
Nasr, Amgad
2012-01-01
In vivo coronary angiography is one of the techniques used to investigate the heart diseases, by using catheter to inject a contrast medium of a given absorption coefficient into the heart vessels. Taking X-ray images produced by X-ray tube or synchrotron radiation for visualizing the blood in the coronary arteries. As the synchrotron radiation generated by the relativistic charged particle at the bending magnets, which emits high intensity photons in comparison with the X-ray tube. The intensity of the synchrotron radiation is varies with time. However for medical imaging it's necessary to measure the incoming intensity with the integrated time. The thesis work includes building a Multi-channel ionization chamber which can be filled with noble gases N 2 , Ar and Xe with controlled inner pressure up to 30 bar. This affects the better absorption efficiency in measuring the high intensity synchrotron beam fluctuation. The detector is a part of the experimental setup used in the k-edge digital subtraction angiography project, which will be used for correcting the angiography images taken by another detector at the same time. The Multi-channel ionization chamber calibration characteristics are measured using 2 kW X-ray tube with molybdenum anode with characteristic energy of 17.44 keV. According to the fast drift velocity of the electrons relative to the positive ions, the electrons will be collected faster at the anode and will induce current signals, while the positive ions is still drifting towards the cathode. However the accumulation of the slow ions inside the detector disturbs the homogeneous applied electric field and leads to what is known a space charge effect. In this work the space charge effect is measured with very high synchrotron photons intensity from EDR beam line at BESSYII. The strong attenuation in the measured amplitude signal occurs when operating the chamber in the recombination region. A plateau is observed at the amplitude signal when
Energy Technology Data Exchange (ETDEWEB)
Nasr, Amgad
2012-07-18
In vivo coronary angiography is one of the techniques used to investigate the heart diseases, by using catheter to inject a contrast medium of a given absorption coefficient into the heart vessels. Taking X-ray images produced by X-ray tube or synchrotron radiation for visualizing the blood in the coronary arteries. As the synchrotron radiation generated by the relativistic charged particle at the bending magnets, which emits high intensity photons in comparison with the X-ray tube. The intensity of the synchrotron radiation is varies with time. However for medical imaging it's necessary to measure the incoming intensity with the integrated time. The thesis work includes building a Multi-channel ionization chamber which can be filled with noble gases N{sub 2}, Ar and Xe with controlled inner pressure up to 30 bar. This affects the better absorption efficiency in measuring the high intensity synchrotron beam fluctuation. The detector is a part of the experimental setup used in the k-edge digital subtraction angiography project, which will be used for correcting the angiography images taken by another detector at the same time. The Multi-channel ionization chamber calibration characteristics are measured using 2 kW X-ray tube with molybdenum anode with characteristic energy of 17.44 keV. According to the fast drift velocity of the electrons relative to the positive ions, the electrons will be collected faster at the anode and will induce current signals, while the positive ions is still drifting towards the cathode. However the accumulation of the slow ions inside the detector disturbs the homogeneous applied electric field and leads to what is known a space charge effect. In this work the space charge effect is measured with very high synchrotron photons intensity from EDR beam line at BESSYII. The strong attenuation in the measured amplitude signal occurs when operating the chamber in the recombination region. A plateau is observed at the amplitude signal when
International Nuclear Information System (INIS)
Taflove, A.
1992-01-01
This paper summarizes the present state and future directions of applying finite-difference and finite-volume time-domain techniques for Maxwell's equations on supercomputers to model complex electromagnetic wave interactions with structures. Applications so far have been dominated by radar cross section technology, but by no means are limited to this area. In fact, the gains we have made place us on the threshold of being able to make tremendous contributions to non-defense electronics and optical technology. Some of the most interesting research in these commercial areas is summarized. 47 refs
Energy Technology Data Exchange (ETDEWEB)
Bluemlein, J.; Hasselhuhn, A.; Kovacikova, P.; Moch, S.
2011-04-15
We provide a fast and precise Mellin-space implementation of the O({alpha}{sub s}) heavy flavor Wilson coefficients for charged current deep inelastic scattering processes. They are of importance for the extraction of the strange quark distribution in neutrino-nucleon scattering and the QCD analyses of the HERA charged current data. Errors in the literature are corrected. We also discuss a series of more general parton parameterizations in Mellin space. (orig.)
A Novel Method Describing the Space Charge Limited Region in a Planar Diode
Directory of Open Access Journals (Sweden)
Mitra Ghergherehchi
2017-11-01
Full Text Available A novel and rather simple method is presented to describe the physics of space-charge region in a planar diode. The method deals with the issue in the time domain and as a consequence transient time behavior can be achieved. Potential distributions and currents obtained using this technique, supposing zero initial velocity for electrons, reveal absolute agreement with Child's results. Moreover, applying the method for non-zero uniform initial velocity for electrons, gives results which are in good agreement with previous works
Space-charge effects on the propagation of hollow electron beams
International Nuclear Information System (INIS)
Barroso, J.J.; Stellati, C.
1994-01-01
The dynamics of hollow electron beams with gyro motion propagating down a cylindrical drift tube is analysed on the basis of a non-adiabatic-gun-generated laminar beam. Due to the action of beam's self-space charge field, the transverse velocity spread has an oscillatory behavior along the drift tube wherein the spatial auto modulation period shortens with increasing current. Numerical simulation results indicate that even at a 10 A beam current, the resulting transverse velocity spread is still less than the spread for a zero beam current. (author). 5 refs, 3 figs
Space-charge driven emittance growth in a 3D mismatched anisotropic beam
International Nuclear Information System (INIS)
Qiang, J.; Ryne, R.D.; Hofmann, I.
2002-01-01
In this paper we present a 3D simulation study of the emittance growth in a mismatched anisotropic beam. The equipartitioning driven by a 4th order space-charge resonance can be significantly modified by the presence of mismatch oscillation and halo formation. This causes emittance growth in both the longitudinal and transverse directions which could drive the beam even further away from equipartition. The averaged emittance growth per degree freedom follows the upper bound of the 2D free energy limit plus the contributions from equipartitioning
Space-charge flow in a non-cylindrically symmetric diode
International Nuclear Information System (INIS)
Quintenz, J.P.; Poukey, J.W.
1976-01-01
The one-dimensional cylindrical space-charge-limited emission and flow results of Langmuir and Blodgett are extended to the two-dimensional (r-theta) non-symmetric case by solving a fluid model numerically. It is found that particle beams thus generated can be controlled by suitable adjustment of the applied potentials and cylinder radii. A particle code has been modified to treat razor blade cathodes by including a simplified model for the blade emission. Numerical results are compared with experimental data. These results indicate that beams produced by razor blades pinch less tightly than those from block cathodes, but in some cases may still pinch enough to be interesting
Space-charge limitation of avalanche growth in narrow-gap resistive plate chambers
Williams, M C S
2004-01-01
A big advance in resistive plate chamber technology happened in 1996 with the advent of the multigap resistive plate chamber (MRPC). The MRPC allows us to easily construct detectors with many small gas gaps and thus we obtain good timing together with high detection efficiency. Using this technology, it is now common to build detectors with gas gaps of 200-300 mum in width. This paper examines space-charge limited avalanche growth; this becomes a dominant effect for narrow gap resistive plate chambers. This effect controls gas gain and explains the reason for the excellent behaviour of MRPCs built with this gas gap.
Increased-accuracy numerical modeling of electron-optical systems with space-charge
International Nuclear Information System (INIS)
Sveshnikov, V.
2011-01-01
This paper presents a method for improving the accuracy of space-charge computation for electron-optical systems. The method proposes to divide the computational region into two parts: a near-cathode region in which analytical solutions are used and a basic one in which numerical methods compute the field distribution and trace electron ray paths. A numerical method is used for calculating the potential along the interface, which involves solving a non-linear equation. Preliminary results illustrating the improvement of accuracy and the convergence of the method for a simple test example are presented.
The effect of nonlinear forces on coherently oscillating space-charge-dominated beams
International Nuclear Information System (INIS)
Celata, C.M.
1987-03-01
A particle-in-cell computer simulation code has been used to study the transverse dynamics of nonrelativistic misaligned space-charge-dominated coasting beams in an alternating gradient focusing channel. In the presence of nonlinear forces due to dodecapole or octupole imperfections of the focusing fields or to image forces, the transverse rms emittance grows in a beat pattern. Analysis indicates that this emittance dilution is due to the driving of coherent modes of the beam near their resonant frequencies by the nonlinear force. The effects of the dodecapole and images forces can be made to effectively cancel for some boundary conditions, but the mechanism is not understood at this time
Modelling of space-charge accumulation process in dielectrics of MDS structures under irradiation
International Nuclear Information System (INIS)
Gurtov, V.A.; Nazarov, A.I.; Travkov, I.V.
1990-01-01
Results of numerical modelling of radiation-induced space charge (RISC) accumulation in MOS structure silicon dioxide are given. Diffusion-drift model which takes account of trap heterogeneous distribution within dielectric volume and channeling of carriers captured at traps represents basis for calculations. Main physical processes affecting RISC accumulation are picked out and character of capture filling in dielectric volume under stress in MOS structure shutter during irradiation on the basis of comparison of experimental results for different thickness oxides with calculation data are predicted
International Nuclear Information System (INIS)
Kopnin, S. I.; Morzhakova, A. A.; Popel, S. I.; Shukla, P. K.
2011-01-01
Effects associated with neutral component of complex (dusty) ionospheric plasmas which affect dust particle charging are studied. Microscopic ion currents on dust particles with taking into account ion-neutral interaction are presented. Calculations are performed both for the case of negative charges of dust particles, when the influence of Solar radiation on dust particle charging processes is negligible, and for the case of positive charges which is realized in the presence of sufficiently intensive UV or X-ray radiation. We also carry out investigation of the electron heating due to the photoelectric effect. We show that the efficiency of electron heating depends on the density of neutral component of the plasma. As result, we determine altitudes where the influence of the neutral plasma component on dust particle charging processes as well as the electron heating effect are significant and should be taken into account under consideration of the ionospheric complex plasmas. In particular, we show that the effects considered could be important for the description of noctilucent clouds, polar mesosphere summer echoes, and some other physical phenomena associated with dust particles in the ionosphere.
International Nuclear Information System (INIS)
Goncalves, Bruno; Dias Junior, Mario Marcio
2013-01-01
Full text: The discussion of experimental manifestations of torsion at low energies is mainly related to the torsion-spin interaction. In this respect the behavior of Dirac field and the spinning particle in an external torsion field deserves and received very special attention. In this work, we consider the combined action of torsion and magnetic field on the massive spinor field. In this case, the Dirac equation is not straightforward solved. We suppose that the spinor has two components. The equations have mixed terms between the two components. The electromagnetic field is introduced in the action by the usual gauge transformation. The torsion field is described by the field S μ . The main purpose of the work is to get an explicit form to the equation of motion that shows the possible interactions between the external fields and the spinor in a Hamiltonian that is independent to each component. We consider that S 0 is constant and is the unique non-vanishing term of S μ . This simplification is taken just to simplify the algebra, as our main point is not to describe the torsion field itself. In order to get physical analysis of the problem, we consider the non-relativistic approximation. The final result is a Hamiltonian that describes a half spin field in the presence of electromagnetic and torsion external fields. (author)
International Nuclear Information System (INIS)
Gow, J P D; Murray, N J; Holland, A D; Hall, D J; Cropper, M; Burt, D; Hopkinson, G; Duvet, L
2012-01-01
Euclid is a medium class European Space Agency mission candidate for launch in 2019 with a primary goal to study the dark universe using the weak lensing and baryonic acoustic oscillations techniques. Weak lensing depends on accurate shape measurements of distant galaxies. Therefore it is beneficial that the effects of radiation-induced charge transfer inefficiency (CTI) in the Euclid CCDs over the course of the 5 year mission at L2 are understood. This will allow, through experimental analysis and modelling techniques, the effects of radiation induced CTI on shape to be decoupled from those of mass inhomogeneities along the line-of-sight. This paper discusses a selection of work from the study that has been undertaken using the e2v CCD204 as part of the initial proton radiation damage assessment for Euclid. The experimental arrangement and procedure are described followed by the results obtained, thereby allowing recommendations to be made on the CCD operating temperature, to provide an insight into CTI effects using an optical background, to assess the benefits of using charge injection on CTI recovery and the effect of the use of two different methods of serial clocking on serial CTI. This work will form the basis of a comparison with a p-channel CCD204 fabricated using the same mask set as the n-channel equivalent. A custom CCD has been designed, based on this work and discussions between e2v technologies plc. and the Euclid consortium, and designated the CCD273.
Electromagnetic fields in an expanding universe
International Nuclear Information System (INIS)
Hogan, P.A.; Ellis, G.F.R.
1989-01-01
The asymptotic form of the electromagnetic field due to a bounded distribution of charge current in an open, expanding Friedmann--Lemaitre--Robertson--Walker universe is studied. The technique used is to first describe a mechanism for passing from a solution of Maxwell's vacuum field equations on Minkowskian space-time to a solution of Maxwell's field equations in a region free of charge current on the cosmological background. This is tested on the field of an accelerating point charge and then applied to the rigorous treatment of the asymptotic electromagnetic field of a bounded charge-current distribution in Minkowskian space-time given by Goldberg and Kerr [J. Math. Phys. 5, 172 (1964)]. A ''peeling expansion'' of the electromagnetic field in the expanding universe is obtained in inverse powers of a parameter that is proportional to the area distance along the generators of future null cones with vertices on the world line of a fundamental observer. The algebraic character of the two leading coefficients in the expansion is the same as that of the two leading coefficients in the Goldberg--Kerr expansion in Minkowskian space-time. In addition, bounds can be calculated, at any instant in the history of a fundamental observer, on all the coefficients in the peeling expansion, as a consequence of the evaluation of such bounds by Goldberg and Kerr in the case treated by them
Directory of Open Access Journals (Sweden)
P. Musumeci
2013-10-01
Full Text Available The evolution of picosecond modulations of the longitudinal profile of an electron beam generated in an rf photoinjector is analyzed and optimized with the goal of obtaining high peak current electron bunch trains at very high frequencies (≥THz. Taking advantage of nonlinear longitudinal space charge forces, it is found that more than 500 A peak current 1 THz bunch trains can be generated using a standard 1.6 cell SLAC/UCLA/BNL rf gun. Postacceleration is used to freeze the longitudinal phase space dynamics after one half plasma oscillation. Applications range from tunable narrow bandwidth THz radiation generation to drivers for high frequency high gradient accelerators.
Vacuum polarization and topological self-interaction of a charge in multiconic space
International Nuclear Information System (INIS)
Gal'tsov, D.V.; Grats, Y.V.; Lavrent'ev, A.B.
1995-01-01
The behavior of classical and quantized massless scalar fields in n-dimensional multiconic space-time is considered. An expression for the Euclidean Green's function is obtained using the methods of perturbation theory. It is shown that a nontrivial topology of the space distorts the electrostatic field of a pointlike charge; as a result, the self-energy of the particle assumes a nonzero value, and a force of topological self-interaction arises. Similarly, a change in the spectrum of vacuum fluctuations of a quantized scalar field leads to nonzero vacuum expectation values left-angle φ 2 right-angle vac and left-angle T μv right-angle va and gives rise to vacuum attraction between parallel cosmic strings. 28 refs
Calibration function for the Orbitrap FTMS accounting for the space charge effect.
Gorshkov, Mikhail V; Good, David M; Lyutvinskiy, Yaroslav; Yang, Hongqian; Zubarev, Roman A
2010-11-01
Ion storage in an electrostatic trap has been implemented with the introduction of the Orbitrap Fourier transform mass spectrometer (FTMS), which demonstrates performance similar to high-field ion cyclotron resonance MS. High mass spectral characteristics resulted in rapid acceptance of the Orbitrap FTMS for Life Sciences applications. The basics of Orbitrap operation are well documented; however, like in any ion trap MS technology, its performance is limited by interactions between the ion clouds. These interactions result in ion cloud couplings, systematic errors in measured masses, interference between ion clouds of different size yet with close m/z ratios, etc. In this work, we have characterized the space-charge effect on the measured frequency for the Orbitrap FTMS, looking for the possibility to achieve sub-ppm levels of mass measurement accuracy (MMA) for peptides in a wide range of total ion population. As a result of this characterization, we proposed an m/z calibration law for the Orbitrap FTMS that accounts for the total ion population present in the trap during a data acquisition event. Using this law, we were able to achieve a zero-space charge MMA limit of 80 ppb for the commercial Orbitrap FTMS system and sub-ppm level of MMA over a wide range of total ion populations with the automatic gain control values varying from 10 to 10(7). Copyright © 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Agostino Marinelli
2010-11-01
Full Text Available Longitudinal space-charge forces from density fluctuations generated by shot noise can be a major source of microbunching instability in relativistic high brightness electron beams. The gain in microbunching due to this effect is broadband, extending at least up to optical frequencies, where the induced structure on the beam distribution gives rise to effects such as coherent optical transition radiation. In the high-frequency regime, theoretical and computational analyses of microbunching formation require a full three-dimensional treatment. In this paper we address the problem of space-charge induced optical microbunching formation in the high-frequency limit when transverse thermal motion due to finite emittance is included for the first time. We derive an analytical description of this process based on the beam’s plasma dielectric function. We discuss the effect of transverse temperature on the angular distribution of microbunching gain and its connection to the physics of Landau damping in longitudinal plasma oscillations. Application of the theory to a relevant experimental scenario is discussed. The analytical results obtained are then compared to the predictions arising from high resolution three-dimensional molecular dynamics simulations.
Rf and space-charge induced emittances in laser-driven rf guns
International Nuclear Information System (INIS)
Kim, Kwang-Je; Chen, Yu-Jiuan.
1988-10-01
Laser-driven rf electron guns are potential sources of high-current, low-emittance, short bunch-length electron beams, which are required for many advanced accelerator applications, such as free-electron lasers and injectors for high-energy machines. In such guns the design of which was pioneered at Los Alamos National Laboratory and which is currently being developed at several other laboratories, a high-power laser beam illuminates a photo-cathode surface placed on an end wall of an rf cavity. The main advantages of this type of gun are that the time structure of the electron beam is controlled by the laser, eliminating the need for bunchers, and that the electric field in rf cavities can be made very strong, so that the effects due to space-charge repulsion can be minimized. In this paper, we present an approximate but simple analysis for the transverse and longitudinal emittances in rf guns that takes into account both the time variation of the rf field and the space-charge effect. The results are compared and found to agree well with those from simulation. 7 refs., 6 figs
Simulation of space-charge effects in an ungated GEM-based TPC
Energy Technology Data Exchange (ETDEWEB)
Böhmer, F.V., E-mail: felix.boehmer@tum.de; Ball, M.; Dørheim, S.; Höppner, C.; Ketzer, B.; Konorov, I.; Neubert, S.; Paul, S.; Rauch, J.; Vandenbroucke, M.
2013-08-11
A fundamental limit to the application of Time Projection Chambers (TPCs) in high-rate experiments is the accumulation of slowly drifting ions in the active gas volume, which compromises the homogeneity of the drift field and hence the detector resolution. Conventionally, this problem is overcome by the use of ion-gating structures. This method, however, introduces large dead times and restricts trigger rates to a few hundred per second. The ion gate can be eliminated from the setup by the use of Gas Electron Multiplier (GEM) foils for gas amplification, which intrinsically suppress the backflow of ions. This makes the continuous operation of a TPC at high rates feasible. In this work, Monte Carlo simulations of the buildup of ion space charge in a GEM-based TPC and the correction of the resulting drift distortions are discussed, based on realistic numbers for the ion backflow in a triple-GEM amplification stack. A TPC in the future P{sup ¯}ANDA experiment at FAIR serves as an example for the experimental environment. The simulations show that space charge densities up to 65 fC cm{sup −3} are reached, leading to electron drift distortions of up to 10 mm. The application of a laser calibration system to correct these distortions is investigated. Based on full simulations of the detector physics and response, we show that it is possible to correct for the drift distortions and to maintain the good momentum resolution of the GEM-TPC.
Simulation of space-charge effects in an ungated GEM-based TPC
International Nuclear Information System (INIS)
Böhmer, F.V.; Ball, M.; Dørheim, S.; Höppner, C.; Ketzer, B.; Konorov, I.; Neubert, S.; Paul, S.; Rauch, J.; Vandenbroucke, M.
2013-01-01
A fundamental limit to the application of Time Projection Chambers (TPCs) in high-rate experiments is the accumulation of slowly drifting ions in the active gas volume, which compromises the homogeneity of the drift field and hence the detector resolution. Conventionally, this problem is overcome by the use of ion-gating structures. This method, however, introduces large dead times and restricts trigger rates to a few hundred per second. The ion gate can be eliminated from the setup by the use of Gas Electron Multiplier (GEM) foils for gas amplification, which intrinsically suppress the backflow of ions. This makes the continuous operation of a TPC at high rates feasible. In this work, Monte Carlo simulations of the buildup of ion space charge in a GEM-based TPC and the correction of the resulting drift distortions are discussed, based on realistic numbers for the ion backflow in a triple-GEM amplification stack. A TPC in the future P ¯ ANDA experiment at FAIR serves as an example for the experimental environment. The simulations show that space charge densities up to 65 fC cm −3 are reached, leading to electron drift distortions of up to 10 mm. The application of a laser calibration system to correct these distortions is investigated. Based on full simulations of the detector physics and response, we show that it is possible to correct for the drift distortions and to maintain the good momentum resolution of the GEM-TPC
Improving the beam quality of rf guns by correction of rf and space-charge effects
International Nuclear Information System (INIS)
Serafini, L.
1992-01-01
In this paper we describe two possible strategies to attain ultra-low emittance electron beam generation by laser-driven RF guns. The first one is based on the exploitation of multi-mode resonant cavities to neutralize the emittance degradation induced by RF effects. Accelerating cigar-like (long and thin) electron bunches in multi-mode operated RF guns the space charge induced emittance is strongly decreased at the same time: high charged bunches, as typically requested by future TeV e - e + colliders, can be delivered by the gun at a quite low transverse emittance and good behaviour in the longitudinal phase space, so that they can be magnetically compressed to reach higher peak currents. The second strategy consists in using disk-like electron bunches, produced by very short laser pulses illuminating the photocathode. By means of an analytical study a new regime has been found, where the normalized transverse emittance scales like the inverse of the peak current, provided that the laser pulse intensity distribution is properly shaped in the transverse direction. Preliminary numerical simulations confirm the analytical predictions and show that the minimum emittance achievable is set up, in this new regime, by the wake-field interaction between the bunch and the cathode metallic wall
International Nuclear Information System (INIS)
Jiang Xiaojun; Zhang Haichao; Wang Yuzhu
2016-01-01
We report the experimental investigation of electromagnetically induced transparency (EIT) in a Zeeman-sublevels Λ-type system of cold 87 Rb atoms in free space. We use the Zeeman substates of the hyperfine energy states 5 2 S 1/2 , F = 2 and 5 2 P 3/2 , F′ = 2 of 87 Rb D 2 line to form a Λ-type EIT scheme. The EIT signal is obtained by scanning the probe light over 1 MHz in 4 ms with an 80 MHz arbitrary waveform generator. More than 97% transparency and 100 kHz EIT window are observed. This EIT scheme is suited for an application of pulsed coherent storage atom clock (Yan B, et al. 2009 Phys. Rev. A 79 063820). (paper)
International Nuclear Information System (INIS)
Rios, I.J.; Mayer, R.E.
2016-01-01
When proportional counters are employed in charge integration mode to determine the magnitude of a radiation pulse, so intense that individual detection events take place in a time too short to produce individual output pulses, mostly in pulsed neutron sources, the strong build-up of positive space charge reduces the electric multiplication factor of the proportional detector. Under such conditions the ensuing measurement underestimates the amount of radiation that interacted with the detector. If the geometric characteristics, the filling gas pressure and the voltage applied to that detector are known, it becomes possible to apply an analytical correction method to the measurement. In this article we present a method that allows to determine the absolute value of the detected radiation burst without the need to know the characteristics of the employed detectors. It is necessary to employ more than one detector, taking advantage of the Influence Method. The “Influence Method” is conceived for the absolute determination of a nuclear particle flux in the absence of known detector efficiency and without the need to register coincidences of any kind. This method exploits the influence of the presence of one detector in the count rate of another detector, when they are placed one behind the other and define statistical estimators for the absolute number of incident particles and for the efficiency (Rios and Mayer, 2015 [1,2]). Its practical implementation in the measurement of a moderated neutron flux arising from an isotopic neutron source was exemplified in (Rios and Mayer, 2016 [3]) and the extension for multiple detectors in (Rios and Mayer 2016 [4]). - Highlights: • Absolute determination of radiation burst. • Proportional counters space charge effect. • Radiation measurements on pulsed devices.
Effect of paraelectrode processes on contraction of space charge in periodic-pulse lasers
Arytyunyan, R. V.; Baranov, V. Yu.; Borisov, V. M.; Vinokhodov, A. Yu.; Kiryukhin, Yu. B.
1986-05-01
A characteristic feature of periodic-pulse electric-discharge CO2-lasers and excimer lasers is contraction of the space charge as the pulse repetition rate increases. The emission energy per pulse decreases as a consequence, with the average laser power first ceasing to increase linearly beyond a certain corner repetition rate and then decreasing beyond a certain critical repetition rate. A study of this phenomenon was made, for the purpose of separating the effect of paracathode processes from the effect of gas dynamics and then evaluating the effect of the former alone. Paraelectrode perturbations were simulated by focusing the radiation from the an XeCl-laser on the cathode surface in an atmosphere of nonabsorbing gases. Laser pulses of up to approximately 0.5 J energy and of approximately 50 ns duration were focused within a spot of 1 mm(2) area on a cathode inside a discharge chamber, with the power density of incident radiation regulated by means of an attenuator. A space charge within a volume of 2.5x4.5x9 cm(3) was generated between this specially shaped cathode and a mesh anode with an approximately 50% optical transmission coefficient. The space charge in helium and in neon was photographed, and the time lag of a discharge pulse behind a contracting laser pulse was measured as a function of the laser pulse energy for these two gases, as well as for a He+C12 gas mixture. The general trend was found to be the same in each case, the time lag increasing with increasing energy first at a slower rate up to a critical energy level and then faster. It has been established that plasma does not build up on the cathode before the laser pulse energy reaches 30 mJ (for a 3 mm(2) surface area), while plasma glow begins as the laser pulse energy reaches 150 mJ. A contracted channel begins to form within the laser-cathode interaction space, with an attendant fast increase of the time lag owing to evaporation of the cathode metal.
Dragt, A. J.; Roberts, P.; Stasevich, T. J.; Dragt, A. Bodoh-Creed A. J.; Roberts, P.; Stasevich, T. J.; Bodoh-Creed, A.; Walstrom, P. L.
2010-01-01
Three-dimensional field distributions from realistic beamline elements can be obtained only by measurement or by numerical solution of a boundary-value problem. In numerical charged-particle map generation, fields along a reference trajectory are differentiated multiple times. Any attempt to differentiate directly such field data multiple times is soon dominated by "noise" due to finite meshing and/or measurement errors. This problem can be overcome by the use of field data on a surface outsi...
Directory of Open Access Journals (Sweden)
E. A. Schneidmiller
2010-11-01
Full Text Available Longitudinal space charge (LSC driven microbunching instability in electron beam formation systems of x-ray free-electron lasers (FELs is a recently discovered effect hampering beam instrumentation and FEL operation. The instability was observed in different facilities in infrared and visible wavelength ranges. In this paper we propose to use such an instability for generation of vacuum ultraviolet (VUV and x-ray radiation. A typical longitudinal space charge amplifier (LSCA consists of few amplification cascades (drift space plus chicane with a short undulator behind the last cascade. If the amplifier starts up from the shot noise, the amplified density modulation has a wide band, on the order of unity. The bandwidth of the radiation within the central cone is given by an inverse number of undulator periods. A wavelength compression could be an attractive option for LSCA since the process is broadband, and a high compression stability is not required. LSCA can be used as a cheap addition to the existing or planned short-wavelength FELs. In particular, it can produce the second color for a pump-probe experiment. It is also possible to generate attosecond pulses in the VUV and x-ray regimes. Some user experiments can profit from a relatively large bandwidth of the radiation, and this is easy to obtain in the LSCA scheme. Finally, since the amplification mechanism is broadband and robust, LSCA can be an interesting alternative to the self-amplified spontaneous emission free-electron laser (SASE FEL in the case of using laser-plasma accelerators as drivers of light sources.
Directory of Open Access Journals (Sweden)
M. Rihaoui
2009-12-01
Full Text Available We report on an experimental study of space-charge effects in a radio-frequency (rf photoinjector. A 5 MeV electron bunch, consisting of a number of beamlets separated transversely, was generated in an rf photocathode gun and propagated in the succeeding drift space. The collective interaction of these beamlets was studied for different experimental conditions. The experiment allowed the exploration of space-charge effects and its comparison with 3D particle-in-cell simulations. Our observations also suggest the possible use of a multibeam configuration to tailor the transverse distribution of an electron beam.
Coreless Linear Induction Motor (LIM) for Space-borne Electro-magnetic Mass Driver Applications
National Aeronautics and Space Administration — Large scale linear induction motors use ferromagnetic cores, but at high speed these cores choke the system’s ability to transform electrical energy into mechanical...
Emittance growth due to static and radiative space charge forces in an electron bunch compressor
Directory of Open Access Journals (Sweden)
Richard Talman
2009-01-01
Full Text Available Evolution of short intense electron bunches passing through bunch-compressing beam lines is studied using the UAL (Unified Accelerator Libraries string space charge formulation [R. Talman, Phys. Rev. ST Accel. Beams 7, 100701 (2004PRABFM1098-440210.1103/PhysRevSTAB.7.100701; N. Malitsky and R. Talman, in Proceedings of the 9th European Particle Accelerator Conference, Lucerne, 2004 (EPS-AG, Lucerne, 2004; R. Talman, Accelerator X-Ray Sources (Wiley-VCH, Weinheim, 2006, Chap. 13]. Three major configurations are studied, with the first most important and studied in greatest detail (because actual experimental results are available and the same results have been simulated with other codes: (i Experimental bunch compression results were obtained at CTF-II, the CERN test facility for the “Compact Linear Collider” using electrons of about 40 MeV. Previous simulations of these results have been performed (using TraFiC4* [A. Kabel et al., Nucl. Instrum. Methods Phys. Res., Sect. A 455, 185 (2000NIMAER0168-900210.1016/S0168-9002(0000729-4] and ELEGANT [M. Borland, Argonne National Laboratory Report No. LS-287, 2000]. All three simulations are in fair agreement with the data except that the UAL simulation predicts a substantial dependence of horizontal emittance ϵ_{x} on beam width (as controlled by the lattice β_{x} function at the compressor location. This is consistent with the experimental observations, but inconsistent with other simulations. Excellent agreement concerning dependence of bunch energy loss on bunch length and magnetic field strength [L. Groening et al., in Proceedings of the Particle Accelerator Conference, Chicago, IL, 2001 (IEEE, New York, 2001, http://groening.home.cern/groening/csr_00.htm] confirms our understanding of the role played by coherent synchrotron radiation (CSR. (ii A controlled comparison is made between the predictions of the UAL code and those of CSRTrack [M. Dohlus and T. Limberg, in Proceedings of the
Charge independence and charge symmetry
Energy Technology Data Exchange (ETDEWEB)
Miller, G A [Washington Univ., Seattle, WA (United States). Dept. of Physics; van Oers, W T.H. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Physics; [TRIUMF, Vancouver, BC (Canada)
1994-09-01
Charge independence and charge symmetry are approximate symmetries of nature, violated by the perturbing effects of the mass difference between up and down quarks and by electromagnetic interactions. The observations of the symmetry breaking effects in nuclear and particle physics and the implications of those effects are reviewed. (author). 145 refs., 3 tabs., 11 figs.
Charge independence and charge symmetry
International Nuclear Information System (INIS)
Miller, G.A.
1994-09-01
Charge independence and charge symmetry are approximate symmetries of nature, violated by the perturbing effects of the mass difference between up and down quarks and by electromagnetic interactions. The observations of the symmetry breaking effects in nuclear and particle physics and the implications of those effects are reviewed. (author). 145 refs., 3 tabs., 11 figs
Fujiwara, Shizuo; 藤原, 鎮男
1989-01-01
Human body works as a kind of tuning filter for the electromagnetic waves in space. The work can be interpretted in terms of the modelling of the surface of the human body as an equivalent circuit formed of the electronic components of inductance, capacit
Energy Technology Data Exchange (ETDEWEB)
Teyssedre, G., E-mail: gilbert.teyssedre@laplace.univ-tlse.fr; Laurent, C. [Université de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse cedex 9 (France); CNRS, LAPLACE, F-31062 Toulouse (France); Vu, T. T. N. [Université de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse cedex 9 (France); Electric Power University, 235 Hoang Quoc Viet, 10000 Hanoi (Viet Nam)
2015-12-21
Among features observed in polyethylene materials under relatively high field, space charge packets, consisting in a pulse of net charge that remains in the form of a pulse as it crosses the insulation, are repeatedly observed but without complete theory explaining their formation and propagation. Positive charge packets are more often reported, and the models based on negative differential mobility(NDM) for the transport of holes could account for some charge packets phenomenology. Conversely, NDM for electrons transport has never been reported so far. The present contribution reports space charge measurements by pulsed electroacoustic method on miniature cables that are model of HVDC cables. The measurements were realized at room temperature or with a temperature gradient of 10 °C through the insulation under DC fields on the order 30–60 kV/mm. Space charge results reveal systematic occurrence of a negative front of charges generated at the inner electrode that moves toward the outer electrode at the beginning of the polarization step. It is observed that the transit time of the front of negative charge increases, and therefore the mobility decreases, with the applied voltage. Further, the estimated mobility, in the range 10{sup −14}–10{sup −13} m{sup 2} V{sup −1} s{sup −1} for the present results, increases when the temperature increases for the same condition of applied voltage. The features substantiate the hypothesis of negative differential mobility used for modelling space charge packets.
Energy Technology Data Exchange (ETDEWEB)
Zurhelle, Alexander F.; Souza, Roger A. de [Institute of Physical Chemistry, RWTH Aachen University (Germany); Tong, Xiaorui; Mebane, David S. [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV (United States); Klein, Andreas [Institute of Materials Science, TU Darmstadt (Germany)
2017-11-13
A space-charge theory applicable to concentrated solid solutions (Poisson-Cahn theory) was applied to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy (XPS) for the concentration of Ce{sup 3+} (the reactive species) at the surface of the oxide catalyst Ce{sub 0.8}Sm{sub 0.2}O{sub 1.9}. In contrast to previous theoretical treatments, these calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space-charge zone. The high space-charge potential that develops at the surface (>0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the space-charge layer. This approach emphasizes the need to take into account defect interactions and to allow deviations from local charge neutrality when considering the surfaces of oxide catalysts. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
Directory of Open Access Journals (Sweden)
Yuanwei Zhu
2018-06-01
Full Text Available Based on the existing acknowledgment that space charge modulates AC and DC breakdown of insulating materials, this investigation promotes the related investigation into the situations of more complex electrical stress, i.e., AC-DC combined voltages. Experimentally, the AC-DC breakdown characteristics of oil impregnated paper insulation were systematically investigated. The effects of pre-applied voltage waveform, AC component ratio, and sample thickness on AC-DC breakdown characteristics were analyzed. After that, based on an improved bipolar charge transport model, the space charge profiles and the space charge induced electric field distortion during AC-DC breakdown were numerically simulated to explain the differences in breakdown characteristics between the pre-applied AC and pre-applied DC methods under AC-DC combined voltages. It is concluded that large amounts of homo-charges are accumulated during AC-DC breakdown, which results in significantly distorted inner electric field, leading to variations of breakdown characteristics of oil impregnated paper insulation. Therefore, space charges under AC-DC combined voltages must be considered in the design of converter transformers. In addition, this investigation could provide supporting breakdown data for insulation design of converter transformers and could promote better understanding on the breakdown mechanism of insulating materials subjected to AC-DC combined voltages.
Space-charge effect in electron time-of-flight analyzer for high-energy photoemission spectroscopy
International Nuclear Information System (INIS)
Greco, G.; Verna, A.; Offi, F.; Stefani, G.
2016-01-01
Highlights: • Two methods for the simulation of space-charge effect in time-resolved PES. • Reliability and advantages in the use of the SIMION"® software. • Simulation of the space-charge effect in an electron TOF analyzer. • Feasibility of a TOF analyzer in time-resolved high-energy PES experiments at FEL. - Abstract: The space-charge effect, due to the instantaneous emission of many electrons after the absorption of a single photons pulse, causes distortion in the photoelectron energy spectrum. Two calculation methods have been applied to simulate the expansion during a free flight of clouds of mono- and bi-energetic electrons generated by a high energy pulse of light and their results have been compared. The accuracy of a widely used tool, such as SIMION"®, in predicting the energy distortion caused by the space-charge has been tested and the reliability of its results is verified. Finally we used SIMION"® to take into account the space-charge effects in the simulation of simple photoemission experiments with a time-of-flight analyzer.
Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier
Energy Technology Data Exchange (ETDEWEB)
Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2011-03-15
A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)
Effects of emittance and space-charge in femtosecond bunch compression
International Nuclear Information System (INIS)
Kan, K.; Yang, J.; Kondoh, T.; Norizawa, K.; Yoshida, Y.
2008-01-01
Ultrashort electron bunches of the order of <100fs are essential for the study of ultrafast reactions and phenomena by means of time-resolved pump-probe experiments. In order to generate such an electron bunch, the effects of emittance, space-charge (SC) and coherent synchrotron radiation (CSR) on the bunch length in a femtosecond magnetic bunch compressor were studied theoretically. It was observed that the bunch length is dominated by the emittance, SC and CSR effects when the electron bunch is compressed into a femtosecond electron bunch. The increases in bunch length due to the transverse emittance, SC and CSR effects in the bunch compressor were 1.7 fs/mm mrad, 107 fs/nC and 72 fs/nC, respectively. Finally, the simulated bunch length was compared with the experimental results.
Space charge dosimeters for extremely low power measurements of radiation in shipping containers
Britton, Jr; Charles, L [Alcoa, TN; Buckner, Mark A [Oak Ridge, TN; Hanson, Gregory R [Clinton, TN; Bryan, William L [Knoxville, TN
2011-04-26
Methods and apparatus are described for space charge dosimeters for extremely low power measurements of radiation in shipping containers. A method includes in situ polling a suite of passive integrating ionizing radiation sensors including reading-out dosimetric data from a first passive integrating ionizing radiation sensor and a second passive integrating ionizing radiation sensor, where the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor remain situated where the dosimetric data was integrated while reading-out. Another method includes arranging a plurality of ionizing radiation sensors in a spatially dispersed array; determining a relative position of each of the plurality of ionizing radiation sensors to define a volume of interest; collecting ionizing radiation data from at least a subset of the plurality of ionizing radiation sensors; and triggering an alarm condition when a dose level of an ionizing radiation source is calculated to exceed a threshold.
Emittance growth in displaced, space-charge-dominated beams with energy spread
International Nuclear Information System (INIS)
Barnard, J.J.; Miller, J.; Haber, I.
1993-01-01
Conversion of transverse energy associated with the coherent motion of displaced beams into thermal energy, and thus emittance growth, has been predicted theoretically by a number of authors. Here, they authors show, using 2-D particle-in-cell simulations, that emittance growth is inhibited for tune depressed beams, if the energy spread of the beam is not too large. Further, using a uniform density model to calculate the space charge field of the beam, they numerically determine the criteria for emittance growth as a function of tune depression, energy spread, and beam displacement over a wide range of parameters. A theoretical interpretation of the results is presented. This study is applicable to an inertial fusion reactor driven by a heavy ion accelerator
Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier
International Nuclear Information System (INIS)
Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V.
2011-03-01
A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)
Theory of space charge limited currents in films and nanowires with dopants
Zhang, Xiaoguang; Pantelides, Sokrates
2015-03-01
We show that proper description of the space charge limited currents (SCLC) in a homogeneous bulk material must account fully for the effect of the dopants and the interplay between dopants and traps. The sharp rise in the current at the trap-filled-limit (TFL) is partially mitigated by the dopant energy levels and the Frenkel effect, namely the lowering of the ionization energy by the electric field, which is screened by the free carriers. In nanowires, lack of effective screening causes the trap occupation at small biases to reach a high level comparable to the TFL in bulk. This explains the high current density in SCLCs observed in nanowires. This work is supported by the LDRD program at ORNL. Portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.
The Properties of the Space-Charge and Net Current Density in Magnetized Plasmas
International Nuclear Information System (INIS)
Hatami, M. M.
2013-01-01
A hydrodynamic model is used to investigate the properties of positive space-charge and net current density in the sheath region of magnetized, collisional plasmas with warm positive ions. It is shown that an increase in the ion-neutral collision frequency, as well as the magnitude of the external magnetic field, leads to an increase in the net current density across the sheath region. The results also show that the accumulation of positive ions in the sheath region increases by increasing the ion-neutral collision frequency and the magnitude of the magnetic field. In addition, it is seen that an increase in the positive ion temperatures causes a decrease in the accumulation of positive ions and the net current density in the sheath region. (basic plasma phenomena)
Generation of attosecond soft x-ray pulses in a longitudinal space charge amplifier
Directory of Open Access Journals (Sweden)
M. Dohlus
2011-09-01
Full Text Available A longitudinal space charge amplifier (LSCA, operating in soft x-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane and a short radiator undulator in the end. The broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond x-ray pulses. It is shown that a compact and cheap addition to the soft x-ray free-electron laser facility FLASH would allow one to generate 60 attosecond (FWHM long x-ray pulses with the peak power at the 100 MW level and a contrast above 98%.
Self-consistent study of space-charge-dominated beams in a misaligned transport system
International Nuclear Information System (INIS)
Sing Babu, P.; Goswami, A.; Pandit, V.S.
2013-01-01
A self-consistent particle-in-cell (PIC) simulation method is developed to investigate the dynamics of space-charge-dominated beams through a misaligned solenoid based transport system. Evolution of beam centroid, beam envelope and emittance is studied as a function of misalignment parameters for various types of beam distributions. Simulation results performed up to 40 mA of proton beam indicate that centroid oscillations induced by the displacement and rotational misalignments of solenoids do not depend of the beam distribution. It is shown that the beam envelope around the centroid is independent of the centroid motion for small centroid oscillation. In addition, we have estimated the loss of beam during the transport caused by the misalignment for various beam distributions
Smith, Joseph G., Jr.; Watson, Kent A.; Delozier, Donavon M.; Connell, John W.
2003-01-01
Thin film membranes of space environmentally stable polymeric materials possessing low color/solar absorptivity (alpha) are of interest for potential applications on Gossamer spacecraft. In addition to these properties, sufficient electrical conductivity is required in order to dissipate electrostatic charge (ESC) build-up brought about by the charged orbital environment. One approach to achieve sufficient electrical conductivity for ESC mitigation is the incorporation of single wall carbon nanotubes (SWNTs). However, when the SWNTs are dispersed throughout the polymer matrix, the nanocomposite films tend to be significantly darker than the pristine material resulting in a higher alpha. The incorporation of conductive additives in combination with a decreased loading level of SWNTs is one approach for improving alpha while retaining conductivity. Taken individually, the low loading level of conductive additives and SWNTs is insufficient in achieving the percolation level necessary for electrical conductivity. When added simultaneously to the film, conductivity is achieved through a synergistic effect. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.
Alternative model of space-charge-limited thermionic current flow through a plasma
Campanell, M. D.
2018-04-01
It is widely assumed that thermionic current flow through a plasma is limited by a "space-charge-limited" (SCL) cathode sheath that consumes the hot cathode's negative bias and accelerates upstream ions into the cathode. Here, we formulate a fundamentally different current-limited mode. In the "inverse" mode, the potentials of both electrodes are above the plasma potential, so that the plasma ions are confined. The bias is consumed by the anode sheath. There is no potential gradient in the neutral plasma region from resistivity or presheath. The inverse cathode sheath pulls some thermoelectrons back to the cathode, thereby limiting the circuit current. Thermoelectrons entering the zero-field plasma region that undergo collisions may also be sent back to the cathode, further attenuating the circuit current. In planar geometry, the plasma density is shown to vary linearly across the electrode gap. A continuum kinetic planar plasma diode simulation model is set up to compare the properties of current modes with classical, conventional SCL, and inverse cathode sheaths. SCL modes can exist only if charge-exchange collisions are turned off in the potential well of the virtual cathode to prevent ion trapping. With the collisions, the current-limited equilibrium must be inverse. Inverse operating modes should therefore be present or possible in many plasma devices that rely on hot cathodes. Evidence from past experiments is discussed. The inverse mode may offer opportunities to minimize sputtering and power consumption that were not previously explored due to the common assumption of SCL sheaths.
Yücel, Abdulkadir C.
2014-07-01
Space vehicles that re-enter the atmosphere often experience communication blackout. The blackout occurs when the vehicle becomes engulfed in plasma produced by interactions between the vehicle surface and the atmosphere. The plasma often is concentrated in a relatively thin shell around the vehicle, with higher densities near its nose than rear. A less structured, sometimes turbulent plasma wake often trails the vehicle. The plasma shell severely affects the performance of side-mounted antennas as it alters their characteristics (frequency response, gain patterns, axial ratio, and impedance) away from nominal, free-space values, sometimes entirely shielding the antenna from the outside world. The plasma plume/turbulent wake similarly affect the performance of antennas mounted at the back of the vehicle. The electromagnetic characteristics of the thin plasma shell and plume/turbulent wake heavily depend on the type of re-entry trajectory, the vehicle\\'s speed, angles of attack, and chemical composition, as well as environmental conditions. To analyze the antennas\\' performance during blackout and to design robust communication antennas, efficient and accurate simulation tools for charactering the antennas\\' performance along the trajectory are called for.
Space-time description of particle creation in gravitational and electromagnetic fields
International Nuclear Information System (INIS)
Mamaev, S.G.; Trunov, N.N.
1983-01-01
The dynamics of the creation of pairs of particles from the vacuum in strong time-dependent external fields is studied. The space-time correlation function of the pair is determined. An analysis of the behavior of this function allows one, in particular, to study the pair-creation process, to distinguish between real and virtual particles, etc
International Nuclear Information System (INIS)
Grote, D.P.
1994-01-01
Heavy ion fusion requires injection, transport and acceleration of high current beams. Detailed simulation of such beams requires fully self-consistent space charge fields and three dimensions. WARP3D, developed for this purpose, is a particle-in-cell plasma simulation code optimized to work within the framework of an accelerator's lattice of accelerating, focusing, and bending elements. The code has been used to study several test problems and for simulations and design of experiments. Two applications are drift compression experiments on the MBE-4 facility at LBL and design of the electrostatic quadrupole injector for the proposed ILSE facility. With aggressive drift compression on MBE-4, anomalous emittance growth was observed. Simulations carried out to examine possible causes showed that essentially all the emittance growth is result of external forces on the beam and not of internal beam space-charge fields. Dominant external forces are the dodecapole component of focusing fields, the image forces on the surrounding pipe and conductors, and the octopole fields that result from the structure of the quadrupole focusing elements. Goal of the design of the electrostatic quadrupole injector is to produce a beam of as low emittance as possible. The simulations show that the dominant effects that increase the emittance are the nonlinear octopole fields and the energy effect (fields in the axial direction that are off-axis). Injectors were designed that minimized the beam envelope in order to reduce the effect of the nonlinear fields. Alterations to the quadrupole structure that reduce the nonlinear fields further were examined. Comparisons were done with a scaled experiment resulted in very good agreement
Space-charge-limited ion flow through an ionizing neutral layer
International Nuclear Information System (INIS)
Duvall, R.E.; Litwin, C.; Maron, Y.
1993-01-01
Space-charge-limited ion flow through an ionizing layer of neutral atoms is studied. The ion flow is between two parallel conducting plates (anode and cathode) with an externally applied voltage between them. An expanding layer of neutral atoms is adjacent to the anode surface, extending a finite distance into the anode--cathode gap. All ions originate either from the anode surface or from the ionization of neutrals; electrons originate only from ionization. Electrons are strongly magnetized by an externally applied, time-independent direct current (dc) magnetic field directed across the ion flow. The ions are unmagnetized, all motion being perpendicular to the conducting plates. Two different models of the anode layer were used to analyze this problem: a multifluid steady-state model and a single fluid time-dependent model. From both models it was found that the anode surface becomes shielded after the ion flux from the ionizing layer becomes larger than the space-charge-limited flux of the reduced gap between the neutral layer and cathode. Comparison was made between the time-dependent model and results from magnetically insulated ion beam diode (MID) experiments. Using an initial areal density of neutral hydrogen and carbon equal to the final observed electron areal density, comparison was made between calculated plasma shielding times and upper bounds on the shielding time observed in experiments. It was found that a layer of neutral hydrogen must contain a minimum of 15% carbon (by number density) to explain the rapid electric field screening observed in experiments