bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards ultra-high gradient particle acceleration in carbon nanotubes
Authors: Perera A , Bonatto A , Bontoiu C , Resta-López J , Rodin V , Welsch C , Xia G , Yadav G
Published: September 2020

Charged particle acceleration using solid-state nanostructures is attracting new attention in recent years as a method of achieving ultra-high acceleration gradients in the order of TV/m. The use of carbon nanotubes (CNTs) has the potential to overcome limitations of using natural crystals, e.g. channelling aperture and thermo-mechanical robustness. In this work, we present preliminary particle-in-cell simulation results of laser and beam interaction with a single CNT, modelled as 20 parallel plates of Carbon ions and electrons. This is the equivalent to a 10-layers tube in 3D. We further discuss simulation of anisotropic particles to model 2D quasi-free electrons in CNT walls. Further research ideas are outlined along with the presentation of a possible proof-of-principle experiment.
Electromagnetic and Beam Dynamics Studies for High Gradient Accelerators at Terahertz Frequencies
Authors: Marongiu M. , Chiadroni E. , Croia M. , Ferrario M. , Ficcadenti L. , Lupi S. , Martinelli V. , Mostacci A. , Pompili R. , Tofani S.
Published: September 2020

THz radiation is one of the most appealing portion of the electromagnetic spectrum in terms of multi-disciplinary use in basic science and technology. Beyond the numerous applications, a great interest is its potential for future, compact linear accelerators.

Conventional radio-frequency accelerating structures operating at the S and C band can reach gradients up to 30 - 50MV/m, respectively; higher accelerating gradients, of the order of 100MV/m, have been obtained with X-band cavities. THz-based accelerating structures enable operation at even higher gradient, potentially up to the GV/m scale, holding great potential for their application to free-electron lasers and linear colliders, for instance.

Here we present electromagnetic and beam dynamics studies about the use of a dielectric loaded waveguide to accelerate electron bunches by mean of a narrow-band multi-cycle THz pulse. The excitation of the accelerating structure by the THz pulse and the bunch acceleration in the excited field are investigated through CST Microwave Studio and GPT simulations.
Spatial autocorrelation study for laser beam quality estimation
Authors: Scifo Jessica , Dotto Alessio Del , Ferrario Massimo , Pompili Riccardo , Villa Fabio
Published: September 2020

High brightness electron beam is required by several applications in the accelerator physics field. In order to have a high brightness beam, that means a high current and a low emittance beam, it is important to study, among other things, the beams non uniformity due to the non perfect transverse laser beam uniformity. Regarding the transverse analysis of the beam, statistical tools as mean and standard deviation are usually used. In this work we will show how the autocorrelation function of a photocathode laser can be used for monitoring the spatial distribution of the beam non-uniformity, strictly connected with the high electron beam emittance: we will apply our analysis on the SPARC_LAB data.
High gradient ultra-high brightness C-band photoinjector optimization
Authors: Croia M , Alesini D , Cardelli F , Diomede M , Ferrario M , Giribono A , Romeo S , Vaccarezza C , Vannozzi A
Published: September 2020

Cathode, laser system, high RF peak field, and gun solenoid are fundamental aspects that have to be optimized to produce high brightness beam in photoinjectors. In order to produce ultra-high brightness beams of about one order of magnitude more than the present devices, new studies have been done in the last years. One promising approach is to increase the peak field on the cathode surface. In this paper we will present a study on a C-band gun using a cathode peak field of 240 MV/m. A first RF study to reach such very high field was done, by means of shortening the RF pulse duration. A first design of the RF structures and solenoid was carried out. If we will not reach exactly the predicted gradient during the RF tests, the impact on the beam dynamics have been simulated reducing the peak field on the cathode up to the value of 130 MV/m, maintaining the same geometry. The convenience of such gun also at a lower gradient, opened the way to possible applications on light production devices. For example, this C-band injector is one of the main options to guide the X-band linac in the CompactLight design study, where an X-ray FEL is foreseen.
Feasibility study for a THz acceleration experiment on the PHIL accelerator at LAL
Authors: Vinatier’ T , Bruni C , Assmann R W , Dorda U , Lemery F , Marchetti B
Published: September 2020

We present a feasibility study for an experiment aiming to post-accelerate an electron bunch, coming from the PHIL (Photo-Injecteur au LAL) photoinjector at LAL (Laboratoire de l’Accélérateur Linéaire), in a circular partially dielectric-loaded waveguide (DLW) driven by a multicycle THz pulse generated by the infrared laser coming from the LASERIX (Installation laser XUV/IR de l’Université Paris Sud) facility. We first discuss the considerations taken into account to fix the DLW design and the THz pulse properties, especially the choice of a 160 GHz THz pulse frequency, and then provide a set of values for their main parameters. We then perform start-to-end simulations of the acceleration experiment, taking into account the current achievable range of parameters at PHIL and the THz pulse properties already achieved with LASERIX with some margins for the coupling losses. They demonstrate the possibility to obtain a 1.2 MeV energy gain for a 10 pC bunch, without charge losses, with a clear shift of the energy spectrum, which would represent a significant improvement compared to the current state-of-the-art of THz acceleration. An overview of the upcoming steps towards the realization of the experiment is finally given.
Summary of Working Group 4: Application of compact and high-gradient accelerators
Authors: Brenner C M , Sarri G
Published: September 2020

We present here an overview of the topics presented and discussed during the Working Group 4 sessions of the European Advanced Accelerator Concepts workshop 2019 (EAAC19). The remit of Working Group 4 (WG4) is to address topics relating to all potential application areas of compact and high-gradient accelerators. This includes recent experimental results and planned demonstration experiments with relevance to radiation generation, medical, industrial, and cultural heritage sector applications, and development of advanced photon sources such as free electron lasers (FEL). Within scope of Working Group 4 is also discussions on planned facilities implementing advanced accelerator concepts that have a focus on applications, as well as beam shaping and tailoring to deliver adequate beams for applications. The topics discussed in the EAAC19 programme for Working Group 4 all fit within the following application theme areas: 1) new facilities exploiting advanced and novel accelerator concepts, 2) development of next generation photon sources, 2) imaging and spectroscopy with laser-plasma accelerator particle and photon beams, and 3) radiobiology with laser-plasma accelerator particle beams.
SINBAD-ARES - A Photo-Injector for external Injection Experiments in novel Accelerators at DESY
Authors: Marchetti Barbara , Assmann Ralph , Brinkmann Reinhard , Burkart Florian , Dorda Ulrich , Floettmann Klaus , Hartl Ingmar , Hillert Wolfgang , Huening Markus , Jafarinia Farzad , Jaster-Merz Sonja , Kellermeier Max , Kuropka Willi , Lemery Francois , Marx Daniel , Mayet Frank , Panofski Eva , Pfeiffer Sven , Schlarb Holger , Vinatier Thomas , Walker Paul Andreas , Winkelmann Lutz , Yamin Sumera
Published: September 2020

The accelerator R&D facility SINBAD (Short Innovative Bunches and Accelerators at DESY) will drive multiple independent experiments in the fields of production of ultra-short electron bunches and tests of advanced high gradient acceleration concepts.

The SINBAD-ARES (Accelerator Research Experiment at SINBAD) linac has been designed to allow the production of high brightness ultra-short electron bunches with excellent arrival-time stability. The accelerator will be used to study experimentally the optimization of the brightness for fs long electron bunches. Such electron bunches, with tunable characteristics, will be then injected into novel accelerators realized in the context of the ATHENA project, the ACHIP international collaboration and the ARIES program. In this paper we describe the principal characteristics of the linac design, we underline the technical challenges connected to the production and characterization of fs bunches and we report on the status of the installation and commissioning.
Progress Towards Laser Wakefield Acceleration and Applications at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA)
Authors: Holt G K , Battaglia G , Brunetti E , Feehan J , Kornaszewski A , Li W , Maitrallain A , Manahan G G , Pring W D , Reid L R , Shahzad M , Spesyvstev R , Vieux G , Wiggins S M , Jaroszynski D A
Published: September 2020

Laser wakefield accelerators (LWFAs) are promising sources of high brightness particle and radiation beams with many possible applications, ranging from scientific research to medicine, industry and border security. The Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) is a university-based facility employing the use of two high-power, ultrashort pulse lasers to advance research, development and application of laser-plasma accelerators. Here we report on recent advancements in LWFA research at SCAPA and upcoming research programmes to demonstrate proof-of-concept applications of the LWFA.
Progress towards laser plasma based free electron laser on COXINEL
Authors: Couprie Marie-Emmanuelle , André Thomas , Blache Frédéric , Bouvet François , Dietrich Yannick , Duval Jean-Pierre , El-Ajjouri Moussa , Ghaith Amin , Herbeaux Christian , Hubert Nicolas , Kitégi Charles , Khojoyan Martin , Labat Marie , Leclercq Nicolas , Lestrade Alain , Loulergue Alexandre , Marcouillé Olivier , Marteau Fabrice , Oumbarek-Espinos Driss , Rommeluére Patrick , Sebdaoui Mourad , Tavakoli Keihan , Valléau Mathieu , Corde Sébastien , Gautier Julien , Goddet Jean Philippe , Kononenko Olena , Lambert Guillaume , Tafzi Amar , Phuoc Kim Ta , Thaury Cédric , Bielawski Serge , Roussel Eléonore , Szwaj Christophe , Andriyash Igor , Malka Victor , Smartsev Slava
Published: September 2020

The Free Electron Laser (FEL) application of Laser Plasma Acceleration (LPA) requires the handling of the energy spread and divergence. The COXINEL manipulation line, designed and built at SOLEIL for this purpose, consists of high gradient quadrupoles for divergence handling and a decompression chicane for energy sorting, enabling FEL amplification with baseline parameters. Installed at Laboratoire d’Optique Appliquee (LOA), it uses robust electrons generated and accelerated by ionization injection using a 30 TW laser. We report here on the work progress towards a FEL demonstration. The LPA measured electron beam characteristics deviates from the baseline reference case. After the installation of the equipment, the electron beam transport has first been optimized. The electron position and dispersion are independently adjusted. Then, undulator radiation has been measured. The spectral purity is controlled via the energy spread adjusted in the slit located in the chicane. FEL effect demonstration is within reach, with currently achieved performance on different LPA experiments.
Multi-objective optimization of the matching beamline for external injection into a laser-driven plasma accelerator
Authors: Panofski E , Assmann R W , Svystun E N
Published: September 2020

Accelerators based on laser plasma wakefield acceleration are of great interest for a new generation of compact machines. External injection of an electron beam from an RF injector into a plasma accelerating stage has the advantage that a well-controlled and fully characterized beam can be used. The matching of the electron bunches into an accelerating plasma wakefield places high demands on the electron beam quality. The electron beam size must be extremely small to match the field structure inside the plasma wake. The short period of the accelerating field in the plasma requires a bunch length in the (sub-)fs range. These electron beam properties result in a high electron density and strongly space charge dominated bunches. The beamline upstream of the plasma must be able to control the significant effect of space charge on the bunch and to transversely match the beam to the focusing fields of the plasma. Further constraints to the beamline design are given by the in-coupling of the high-power drive laser and the implementation of diagnostic tools. Choosing suitable settings for the beamline elements in order to match the beam thus poses a great challenge. Using multi-objective optimization, suitable settings for the beamline elements can be extracted from Pareto optimum solutions. The development of a universal multi-objective optimization algorithm for beamline matching as well as first optimization results are presented.
Summary of Working Group 5: Plasma devices, plasma and beam diagnostics
Authors: D’Arcy Richard , Delerue Nicolas
Published: September 2020

The presentations and proceedings of Working Group 5 (plasma devices, plasma and beam diagnostics) at the fourth European Advanced Accelerator (EAAC) Workshop reported on experimental demonstrations and simulation studies for new concepts in the field of plasma/beam diagnostics and plasma devices. New schemes, as well as the development of those already well benchmarked, were described, covering a breadth of concepts ranging from the diagnosis of how both hot and cold plasmas evolve in time to how in time they may be applied to future high-energy-physics and photon science facilities.
Plasma density profile measurements for ultra-short high power laser beam guiding experiments at SPARC _LAB
Authors: Costa G , Anania M P , Biagioni A , Bisesto F G , Brentegani E , Ferrario M , Pompili R , Romeo S , Rossi A R , Zigler A , Cianchi A
Published: September 2020

External injection is a promising method to achieve high accelerating gradients and to control the beam properties. The energy gain of an electron via the wakefield is proportional to the product of the accelerating field multiplied by the effective propagation distance of the laser. Therefore, in order to bring the electron energy in the order of the GeV, a longer propagation length is required, which can be obtained by guiding the laser pulse in a wave-guide. In the case of SPARC_LAB, a 500 μτη diameter hydrogen-filled capillary discharge is used; to guide the laser beam it is necessary to act on the refractive index of the plasma, depending on its density. In this work measurements of the trend over time of the longitudinal profile of the plasma density within the capillary are presented, along with openFOAM simulations of the gas profile distribution. Preliminary test of laser guiding are also shown, detecting the behaviour of the laser beam at the exit of the capillary with respect to the discharge current value.
Control of undulator radiation using a Laser Plasma Acceleration Source
Authors: Ghaith Amin , Oumbarek-Espinos Driss , André Thomas , Roussel Eléonore , Loulergue Alexandre , Labat Marie , Corde Sébastian , Kononenko Olena , Valléau Mathieu , Marcouillé Olivier , Bielawski Serge , Malka Victor , Couprie Marie-Emmanuelle
Published: September 2020

Spontaneous undulator radiation emission, after the COXINEL line using a Laser Plasma acceleration (LPA) source, has been observed. The line enables to manipulate the electron beam phase space such as emittance, dispersion and energy spread along a 10 m long transport. The large divergence is handled at a very early stage to mitigate the chromatic emittance, using high gradient permanent magnet based quadrupoles mounted on translation tables. The operating energy is between 161-180 MeV focused in a 2-m long cryo-ready undulator with a period of 18 mm emitting light in the Ultra-Violet range. The spectral flux is characterized using a spectrometer. The wavelength is tuned by either changing the electron beam energy or by adjusting the undulator gap. The radiation pattern signature is illustrated alongside its dependence on the energy spread that is modified by introducing a slit in a magnetic chicane where a small relative bandwidth of 5% has been achieved.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Simulation of the radar signal reflection from the lunar surface
Authors: Yushkova Olga , Iushkov Viacheslav , Rudamenko Roman
Published: September 2020

To determine the structure and mineralogical composition of lunar subsurface a radar complex RLK-L will be installed on the “Luna-26” spacecraft. The inverse problem solution of subsurface sounding will be more accurate if all factors affecting the shape of the reflected signal are taken into account. Topography is one such factor. The article deals with modelling the reflection of a radio signal from a rough surface. An analysis of a series of numerical experiments showed that destruction of high frequency part of the spectrum depends on the dispersion of the inhomogeneities’ heights in reflection spot. The simulation results are consistent with previously performed experimental measurements and well-known theoretical estimates. Therefore, in radar experiments, it makes sense to first analyze the signals reflected from smooth areas, then from the area in which a three-dimensional digital model of lunar surface reveals the presence of depressions, and then areas with mountain ranges.
The bandwidth-duration product of the received radar signal as a criterion for observing wind field inhomogeneity
Authors: Zhukov V Y , Denisenkov D A , Shchukin G G
Published: September 2020

The coherent mode meteorological radars applicability to recognizing weather hazard associated with wind fields inhomogeneity is analyzed. It is noted that for the aviation weather service the estimates of the received reflections spectral characteristics prove to be little informative. Problems that hinder the use of these phenomena detection results have been identified. It is proposed that new methods based on estimates of the reflected signal spectrum width and methods based on the detection of the complexity of the received signal, which is the sum of two reflections from different air masses with different characteristics, should be used for this purpose. As an indicator of this complication, it is assumed to use the bandwidth-duration product, which is a product of its energy spectrum width by the interval of its amplitude correlation. The theoretical calculation results of the bandwidth-duration product, which spectrum consists of two Gaussian form components, for different values of average frequency and/or width, are given. The received data allow asserting that the bandwidth-duration product practically does not change at small differences of Doppler shifts of signal components, but very sensitively reacts to a difference in a spectrum width, i.e. in the most interesting cases for a solved problem.
Algorithm for designing low-noise frequency synthesizers for remote sensing systems
Authors: Romashov V V , Yakimenko K A , Romashova L V , Doktorov A N
Published: September 2020

Frequency synthesizer is an important component of radar tracking system for remote sensing. Synthesizers generate wideband radio frequency signals with high frequency resolution. Parameters of radar depend on the synthesizers phase noise. This paper presents algorithm for structural design of signal generators based on various synthesis methods: direct, indirect and hybrid ones. Specialized software based on presented algorithm was developed in this work. Software allows calculating frequency ratios in the structure of synthesizers, selecting optimal parameters which can provide low phase noise level. Also software allows performing mathematical modelling and analysis of phase noise power spectral density (PSD) of frequency synthesizers. Presented algorithm and software can be useful for developers of remote sensing radio systems.
The Tangential Velocity MTI Algorithms in Space-borne Systems for Remote Sensing of the Earth
Authors: Kostrov V V , Tolstov E F , Khramov K K
Published: September 2020

In this paper, the problem of moving target indication (MTI) using synthetic aperture radar (SAR) is considered. The focus of the article is the tangential component of velocity. Two tangential velocity MTI algorithms are considered. The first algorithm uses two apertures with various synthetic time of the radar image (AVST algorithm), and the second uses two apertures displaced along trajectory (ADAT algorithm). The structure of the MTI system based on the analysis of phase and amplitude radar images is considered. For S band and X band SAR, the phase change in the trajectory signal of a moving target, the effects of shift and bifurcation of target responses on the radar image are analyzed in detail. It was found that the AVST algorithm has a small working range of unambiguous velocity estimate (up to ±10 m/s). It is shown that the ADAT algorithm has a higher quality of work in a wide velocity range and can effectively suppress the signals of stationary objects by 20…30 dB. The obtained characteristics allow us to make demands on the parameters of space-borne systems for remote sensing of the Earth and processing systems.
Features of Through-Wall Radars Development for Detecting of Moving Objects behind Optically Opaque Barriers
Authors: Ioda S V , Vasiliev Ya O , Marchuk V N
Published: September 2020

Detecting people behind optically opaque barriers is an urgent task of the modern world. It allows to solve problems in the following areas: conducting anti-terrorist operations, searching people under rubble and avalanches, security measures. This article describes the device features developed on the basis of the radio wave methods usage, which makes it possible to detect moving objects behind optically opaque obstacles. The performance of the instrument is improved over the prototype broadband radar for detecting people behind optically opaque obstacles “Dannik-5”, developed at the Federal State Unitary Enterprise SDB IRE RAS. Unique ultra-wideband small-sized printed antennas have been developed for the device. Thanks to them, its directional diagram has been improved, a clearer restructuring in the field of view and a more accurate determination of the location of a moving object are provided. The use of small-sized printed antennas and an optimized internal layout of the device made it possible to improve the shielding of the device, which eliminated its susceptibility to objects moving on the side and behind the radar, and also made it possible to significantly improve its mass-dimensional characteristics. Comparative characteristics in relation to domestic devices and foreign analogs are given. The device is competitive with world analogues.
Application high-speed digital-to-analog converters for direct digital synthesis of high-frequency radio signals
Authors: Romashov V V , Doktorov A N , Yakimenko K A , Sochneva N A
Published: September 2020

The main features of high-speed digital-to-analog converters designed for direct digital synthesis of radio frequency signals in the UHF and microwave ranges are presented. A block diagram of a digital signal generator based on high-speed DACS is proposed. These DACs are designed to create digital signal generators that work based on the direct digital synthesis method. The main specialized modes of operation of high-speed digital-to-analog converters that allow efficient use of extra components of the spectrum are studied. Images of the main frequency of synthesis occur when the signal is restored from digital to analog form. Special operating modes of high-speed DACS allow you to create broadband and ultra-wideband signals. The use of high-speed digital-to-analog converters in special modes of operation makes it possible to simplify the block diagrams of digital signal generator. The scheme is simplified by reducing the number of cascades of the output frequency multipliers.