bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a beam profile monitor based on silicon strip sensors for low-charge electron beams
Authors: Jaster-Merz S , Assmann R W , Burkart F , Dorda U , Dreyling-Eschweiler J , Huth L , Krämer U , Stanitzki M 
Published: September 2020

Abstract
Novel accelerator techniques such as dielectric laser acceleration (DLA) will be studied at the SINBAD facility (DESY Hamburg) using the ARES electron linac. Due to the low charge of the accelerated beams, charge densities below 1 aC per square micron are expected at the spectrometer screen, which are challenging to measure with conventional techniques used in multi-pC accelerators. Therefore, a dedicated beam profile monitor, based on silicon strip sensors from the ATLAS inner tracker upgrade, was developed to measure these distributions with a sufficient spatial resolution of around 100 micron. Here, the design of the device and experimental tests with a prototype are presented.
Predicting the Trajectory of a Relativistic Electron Beam for External Injection in Plasma Wakefields
Authors: Asmus F. Peña , Velotti F. M. , Turner M. , Gessner S. , Martyanov M. , Bracco C. , Goddard B. , Muggli P. 
Published: September 2020

Abstract
We use beam position measurements over the first part of the AWAKE electron beamline, together with beamline modeling, to deduce the beam average momentum and to predict the beam position in the second part of the beamline. Results show that using only the first five beam position monitors leads to much larger differences between predicted and measured positions at the last two monitors than when using the first eight beam position monitors. These last two positions can in principle be used with ballistic calculations to predict the parameters of closest approach of the electron bunch with the proton beam. In external injection experiments of the electron bunch into plasma wakefields driven by the proton bunch, only the first five beam position monitors measurements remain un-affected by the presence of the much higher charge proton bunch. Results with eight beam position monitors show the prediction method works in principle to determine electron and proton beams closest approach within the wakefields width (<1 mm), corresponding to injection of electrons into the wakefields. Using five beam position monitors is not sufficient.
Compact and tunable active-plasma lens system for witness extraction and driver removal
Authors: Dotto A. Del , Chiadroni E. , Cianchi A. , Faillace L. , Ferrario M. , Iovine P. , Masullo M.R. , Pompili R. 
Published: September 2020

Abstract
Plasma based technology will allow an unprecedented reduction of the size of accelerating machines. Both fundamental research and applied science and technology will take profit of this feature. The same compactness is required downstream the accelerator module, where the plasma-accelerated beams usually experience a large angular divergences growth. Therefore compact, strong and tunable focusing devices are needed. Active-plasma lenses have been demonstrated to be a compact and affordable tool to generate radially symmetric magnetic fields. We present a new scheme using active-plasma lenses and a metallic collimator to catch and transport the witness bunch while removing the driver. The considered case study is in the context of the EuPRAXIA project.
Cerenkov-free RIP Maxwell solver: dispersionless along X
Authors: Pukhov Alexander 
Published: September 2020

Abstract
A semi-implicit finite-difference time-domain (FDTD) numerical Maxwell solver is presented for full electromagnetic Particle-in-Cell (PIC) codes for the simulations of plasma-based acceleration. The solver projects the volumetric Yee lattice into planes transverse to a selected axis (the particle acceleration direction) that makes the scheme quasi-one-dimensional. The fields positions build rhombi in plane (RIP) patterns. The RIP scheme uses a compact local stencil that makes it perfectly suitable for massively parallel processing via domain decomposition along all three dimensions. No global/local spectral methods are involved. The scheme removes the numerical dispersion of electromagnetic waves running parallel to the selected axis. The scheme shows no numerical Cerenkov instability (NCI).
Azimuthal decomposition study of a realistic laser profile for efficient modeling of Laser WakeField Acceleration
Authors: Zemzemi I. , Massimo F. , Beck A. 
Published: September 2020

Abstract
The advent of ultra short high intensity lasers has paved the way to new and promising, yet challenging, areas of research in the laser-plasma interaction physics. The success of constructing petawatt femtosecond lasers, for instance the Apollon laser in France, will help understanding and designing future particle accelerators and next generation of light sources. Achieving this goal intrinsically relies on the combination between experiments and massively parallel simulations. So far, Particle-In-Cell (PIC) codes have been the ultimate tool to accurately describe the laser-plasma interaction especially in the field of Laser WakeField Acceleration (LWFA). Nevertheless, the numerical modelling of laser plasma accelerators in 3D can be a very challenging task. This is due to the large dispersity between the scales involved in this process. In order to make such simulations feasible with a significant speed up, we need to use reduced numerical models which simplify the problem while retaining a high fidelity. Among these models, Fourier field decomposition in azimuthal modes for the cylindrical geometry [1] is a promising reduced model especially for physical problems that have close to cylindrical symmetry which is the case in LWFA. This geometry has been implemented in the open-source code SMILEI [2] in Finite Difference Time Domain (FDTD) discretization scheme for the Maxwell solver. In this paper we will study the case of a realistic laser measurement from Apollon facility, the ability of this method to describe it correctly and the determination of the necessary number of modes for this purpose. We will also show the importance of higher modes inclusion in the case of realistic laser profiles to insure fidelity in simulation.
Efficient cylindrical envelope modeling for laser wakefield acceleration
Authors: Massimo F. , Zemzemi I. , Beck A. , Derouillat J. , Specka A. 
Published: September 2020

Abstract
The resolution of the system given by Maxwell’s equations and Vlasov equation in three dimensions can describe all the phenomena of interest for laser wakefield acceleration, with few exceptions (e.g. ionization). Such arduous task can be numerically completed using Particle in Cell (PIC) codes, where the plasma is sampled by an ensemble of macroparticles and the electromagnetic fields are defined on a computational grid. However, the resulting three dimensional PIC simulations require substantial resources and often yield a larger amount of information than the one necessary to study a particular aspect of a phenomenon. Reduced models, i.e. models of the Maxwell-Vlasov system taking into account approximations and symmetries, are thus of fundamental importance for preliminary studies and parametric scans. In this work, the implementation of one of these models in the code SMILEI, an envelope description of the laser-plasma interaction with cylindrical symmetry, is described.
Transformer Ratio at Wakefield Excitation by Train of Electron Bunches with Linear Growth of Current in Dielectric Resonator Electron–Positron Collider
Authors: Maslov V , Bondar D , Onishchenko I , Papkovich V 
Published: September 2020

Abstract
The efficiency of electron bunch acceleration by wakefield, excited in two-beam electron-positron dielectric resonator collider by train of electron bunches is determined by transformer ratio (TR). The train of homogeneous bunches, in which current grows linearly along a train, is considered. The length of homogeneous bunch equals to half of excited wavelength 0.5λ. Interval between bunches is ρλ, p = 1, 2,… The conditions have been formulated, when the wakefield pulses from all electron bunches are added. Bunch is injected in dielectric resonator, when the back wavefront of the wakefield pulse is on the bunch-injection boundary of the resonator/cavity. Bunch leaves the resonator, when the first wavefront of wakefield pulse is on the end of the resonator. The conditions for a large TR have been formulated. The wakefield and TR have been derived after N bunch. The computer simulation has been performed taking into account wakefield pulse dispersion spreading and electron bunch transition radiations. The results of analytical investigation are compared with the results of computer simulation. It has been shown that the dependence TR = 2N is performed. Advantage of this mode with large transformer ratio that some injected bunch with decreased current becomes witness. When this bunch is injected it gets in maximum accelerating field.
The infinite periodical mode of accelerator operation has been proposed. In this mode, witness-bunches and driver-bunches are injected according to periodic mode. In the infinite periodical mode, short shaped trains of driver-bunches are alternated with witnesses. Large transformer ratio and identical decelerating field for all driver-bunches are provided by this long periodic train.
Modeling and simulation of transverse wakefields in PWFA
Authors: Chen J B B , Schulte D , Adli E 
Published: September 2020

Abstract
A simplified model describing the PWFA (plasma wakefield acceleration) transverse instability in the form of a wake function parameterized only with an effective cavity aperture radius a is benchmarked against PIC-simulations. This wake function implies a 1/a4 scaling of the transverse wakefields, which indicates transverse intra-beam wakefields typically several orders of magnitude higher than in conventional acceleration structures. Furthermore, the wakefield formalism is utilized to perform a parameter study for a 1.5 TeV plasma wakefield accelerator, where the constraint on drive beam to main beam efficiency imposed by transverse wakefields is taken into account. Eventually, a parameter set with promising properties in terms of energy spread, stability and luminosity per power was found.
Single-cycle THz signal accompanying laser wake in photoionized plasmas and plasma channels
Authors: Kalmykov S Y , Englesbe A , Elle J , Schmitt-Sody A 
Published: September 2020

Abstract
Photoionization by a femtosecond, terawatt laser pulse generates a plasma column in a neutral ambient gas. Velocity of electrons, pushed by the laser ponderomotive force along the column surface, couples to the the radial density gradient at the column boundary, generating an azimuthally polarized THz rotational current (RC). The same mechanism produces the low-frequency RC in a leaky plasma channel. Applying external voltage to the channel induces a radially non-uniform electron flow (direct current) and a constant, azimuthally polarized magnetic field. Coupling them to the electron density perturbations adds two more terms to the RC. The surface RC in the plasma column supports a broadband, evanescent THz signal accompanying the wake. A few millimeters away from the column, rapid evanescence of high-frequency components turns this THz signal into a radially polarized, single-cycle pulse.
High transformer ratio resonant PWFA ideal working point design for EuPRAXIA@SPARC_LAB
Authors: Romeo S. , Dotto A. Del , Ferrario M. , Rossi A.R. 
Published: September 2020

Abstract
In the context of plasma beam driven wakefield acceleration, we design and numerically test an ideal working point that exploits the resonant behavior of a train of driving bunches with ramped charge in order to accelerate a trailing bunch to high energy. The working point consists in a train of four bunches generated by an RF X-band photo-injector with the energy of 1.2 GeV. The bunch current profile is shaped by means of hybrid compression stage exploiting the combination of velocity bunching and magnetic chicane. The charges are properly calibrated in order to maximize the transformer ratio up to RT=8. The trailing bunch has a triangular shape and a peak current I=3 kA. By means of a 2.4m long plasma channel we simulated the acceleration of the trailing bunch up to 5 GeV mainly preserving the quality of the accelerated beam. The simulations were performed in cylindrical symmetry with the hybrid kinetic-fluid code Architect.
Numerical implementation of a hybrid PIC-fluid framework in laser-envelope approximation
Authors: Terzani Davide , Londrillo Pasquale , Tomassini Paolo , Gizzi Leonida A 
Published: September 2020

Abstract
Particle-In-Cell (PIC) simulation are fundamental to address a detailed study of a Laser Wake Field Acceleration process. Given the ongoing development of cm-scale plasma accelerators, reduced physical models are necessary to face otherwise unfeasible predictive start-to-end simulations. In this context, the equation of a plasma in the cold fluid approximation can be a powerful numerical tool because the system dynamics relies on the inversion of the Euler equation on a grid, much cheaper than the usual field coupling with macroparticle motion that characterizes the standard PIC loop. We show here the implementation of a hybrid PIC-fluid framework in ALaDyn code that allows the bulk plasma dynamics to be quickly solved while retaining the kinetic properties by placing macroparticles on top of the fluid background.
TeV acceleration in a Matryoshka plasma channel
Authors: Farmer J P , Pukhov A 
Published: September 2020

Abstract
Plasma-based accelerators offer accelerating fields orders of magnitude higher than conventional radio-frequency cavities. However, these accelerating fields are typically coupled with strong focusing fields, which can result in significant radiative energy loss at high energies. In this work, we present a new accelerator configuration, the Matryoshka channel, a hollow plasma channel stabilized by a hollow plasma filament. We demonstrate that the absence of on-axis focusing plasma fields greatly reduces radiation losses, allowing acceleration to the TeV frontier.
Measuring scattering function of HF NVIS channel by sounding with the use of a noise-like BPSK signal
Authors: Ivanov V A , Elsukov A A , Ryabova M I 
Published: September 2020

Abstract
Measuring parameters of the scattering function of near vertical incidence skywave (NVIS) radio links employed for data transmission is topical and fosters better understanding signal propagation as well as developing state-of-the-art cognitive radio systems. In this regard, the paper presents the findings of the research into the application of a noise-like phase-shift keying (PSK) signal for vertical sounding of NVIS radio links. There are presented the developed algorithms for processing the PSK signal to measure the scattering function and its parameters (signal-to-noise ratio, delay spread and Doppler spread) for multiple communication channels in the high frequency (HF) band. To carry out experiments on measuring scattering function of radio channels with bandwidth of 24 kHz and different mid-band frequencies, we employed developed ionosonde based on the universal software radio peripherals (USRP) platform.
Features of the Use of Symbolic Calculations for Constructing Wave Field Local Asymptotics Using Catastrophe Theory
Authors: Kryukovsky A S , Bova Yu I 
Published: September 2020

Abstract
Base on symbol calculation a local asymptotic method is developed that describes the diffraction focusing of electromagnetic fields in the case when a family of primary (geometrooptical) and secondary (edge) rays form focusings of the cuspoid type A2 (wave catastrophe F4). Mathematical modeling of the unfolding coefficients and the traveling wave phase was performed. Explicit expressions for the parameters of unfolding are obtained.
Approximating the probability distribution laws for critical frequency deviations of the ionospheric F2 layer by fourth-degree polynomials
Authors: Ivannikova A G , Kotonaeva N G , Mikhailov V V 
Published: September 2020

Abstract
One of important tasks in studying the ionosphere is to determine its perturbation level. Determining and predicting the ionosphere perturbation degree is necessary for solving practical problems, as well as for a theoretical study of processes occurring in it. There is also an urgent problem of creating a new daily-seasonal ionospheric perturbation scale. One of approaches to solve these problems can be to determine the distribution laws for deviations in the critical frequencies of the F2 layer from their median values calculated for previous 27 days. The optimal method for calculating polynomial dependencies for determining the probability distribution laws for deviations in the critical frequency of the ionospheric F2 layer for the longitude chain of observation stations in cases when they are different from the normal one is suggested in this article. The optimal degree of the approximating polynomial is determined. Polynomial coefficients are calculated. The percentage of data from the present period that exceeds the limits of the obtained dependencies in each case is calculated. The analysis of the obtained results is carried out, as a result of which the possibility of describing the behavior of the ionosphere by the obtained dependencies is determined.
Features of the effect of the Earth’s ionosphere on the field of an ordinary wave in the vicinity of the caustic
Authors: Bova Yu I , Kryukovsky A S , Lukin D S , Rastyagaev D V 
Published: September 2020

Abstract
The structure of the electromagnetic wave field in the vicinity of the caustic in the case of propagation in magnetically active ionospheric plasma near the surface of the earth is considered. A comparison of the uniform (caustic) approximation and the non-uniform (ray) one is performed. It is shown that the maximum value of the field amplitude in the vicinity of the caustic can be estimated from the geometrical-optical (ray) approximation. The calculations were performed both taking into account and without taking into account absorption, as well as taking into account the divergence of the radio signal in an anisotropic plasma for the model of night electron concentration and collision frequency of the high-latitude ionosphere. An estimate of the field on the caustic based on the ray approximation is proposed.
Absorption of decimetre radio waves in the Earth’s high-latitude ionosphere during a geomagnetic storm in June 2015
Authors: Andreev V E , Gubenko V N , Pavelyev A A , Kirillovich I A , Gubenko T V 
Published: September 2020

Abstract
We have analyzed the radio occultation (RO) results of ∼100 sounding sessions of the high-latitude (>65°N) lower ionosphere of the Earth’s northern hemisphere, which were carried out on 22–23 June 2015 at the GPS-frequency of 1545.42 MHz (L1 band) in the FORMOSAT-3/COSMIC experiment. Coronal plasma ejections that reached the Earth in this period provoked a class G4 magnetic storm (strong geomagnetic storm with planetary Kp-index equal to 8), which in turn caused significant ionospheric fluctuations of radio waves on the sounding paths: navigation (GPS) satellites – low-orbit (FORMOSAT-3/COSMIC) satellites. For the first time, the analysis of FORMOSAT-3/COSMIC radio frequency measurements revealed the absorption of L1 radio waves in the lower high-latitude ionosphere of the Earth. The absorption value is ∼3 dB in the range of 60-90 km and in some cases reaches ∼10 dB at altitudes from 90 to 95 km. It is shown that it is possible to obtain the absorption coefficient of GPS-frequency radio waves in the Earth’s ionosphere at these altitudes from experimental data of FORMOSAT-3/COSMIC.
Mathematical modeling of the polarization characteristics of radio waves in the Earth’s equatorial ionosphere
Authors: Bova Yu I , Kryukovsky A S , Kutuza B G , Rastyagaev D V , Lukin D S 
Published: September 2020

Abstract
Using the bicharacteristics method, mathematical modeling of the polarization parameters of P-band radio waves in the Earth’s ionosphere in the vicinity of the equatorial anomaly along the meridian path was carried out. The influence of the ionosphere on the phase deviation and the angle of the Faraday rotation during the passage of the spacecraft is studied taking into account changes in the magnitude and orientation of the Earth’s magnetic field.
The influence of clouds on atmospheric radiation fluctuations in the resonance absorption band of water vapor 18 27.2 GHz
Authors: Egorov Dobroslav P. , Kutuza Boris G. 
Published: September 2020

Abstract
The results of processing new experimental data on brightness temperature of atmospheric downwelling radiation near the resonance absorption line of water vapor 22.235 GHz are presented. The experiment was carried out by means of special 47-channel microwave radiometer-spectrometer. In this article the observations of stable clear sky and also cumulus cloud cover of various vertical extent for summer 2018-2019 measurement periods are considered. Due to assess the dynamics of brightness temperature fluctuations, the apparatus of Kolmogorov’s structural functions is used. Spectra of square root of structural function for wide range of temporal interval values under clear sky and cumulus cloud cover conditions are obtained. The two-frequency method of integral atmospheric moisture content evaluation is discussed. Experimental dependencies of cloud liquid water content on square root of structural function are shown.
Modelling the reflection of radio waves from cold glaciers
Authors: Yushkova Olga , Dymova Taisiya 
Published: September 2020

Abstract
Radio echo-sounding is a powerful technique for investigating glacier subsurface. Various remote sensing techniques use different wavelengths (e.g., 13.575 GHz for CryoSat and 20-25/200-600 MHz for ground-penetrating radar), and the results gained using different wavelengths may not coincide but rather complement each other. Here we describe the electrophysical model of a cold glacier based on glaciological input data and radiophysical laws; calculate the depth profile of the dielectric constant, and track variations in the effective part of the dielectric constant and the loss tangent depending on the surface temperature and frequency of the radio signals; calculate the frequency dependence of the reflectivity coefficient of the modelled glacier; reveal the frequency range of radio-waves most suitable for investigation of glacier characteristics.
Multi-band microwave radiometric sensing of remote rain zones
Authors: Fedoseeva E V , Rostokin I N , Shchukin G G , Rostokina E A 
Published: September 2020

Abstract
This work relates to the problem of forecasting dangerous weather events - heavy rains and heavy precipitation in the form of snow and hail in a certain area based on the results of passive microwave radiometric measurements. The article presents the results of research on the possibility of implementing a multi-band method for detecting and monitoring rain zones with inclined microwave radiometric sensing at small angles. The analysis of the influence of a remote rain area on the atmosphere radio brightness temperature during horizontal sounding of a multi-frequency microwave radiometric system is performed. Numerical estimates of the radio brightness temperature and its increase due to the presence of the rain zone in the direction of sounding are obtained. The atmosphere with rain thermal radiation power measurements data, made by a tri-band microwave radiometric system, show a trend for different time of the system output growth formation, when the rain area approaches to the place-based microwave radiometric system.