We present a prototype of a tool leveraging the synergy of model driven engineering (MDE) and Large Language Models (LLM) for the purpose of software development process automation in the automotive industry. In this approach, the user-provided input is free form textual requirements, which are first translated to Ecore model instance representation using an LLM, which is afterwards checked for consistency using Object Constraint Language (OCL) rules. After successful consistency check, the model instance is fed as input to another LLM for the purpose of code generation. The generated code is evaluated in a simulated environment using CARLA simulator connected to an example centralized vehicle architecture, in an emergency brake scenario.

We propose a novel model- and feature-based approach to development of vehicle software systems, where the end architecture is not explicitly defined. Instead, it emerges from an iterative process of search and optimization given certain constraints, requirements and hardware architecture, while retaining the property of single-system illusion, where applications run in a logically uniform environment. One of the key points of the presented approach is the inclusion of modern generative AI, specifically Large Language Models (LLMs), in the loop. With the recent advances in the field, we expect that the LLMs will be able to assist in processing of requirements, generation of formal system models, as well as generation of software deployment specification and test code. The resulting pipeline is automated to a large extent, with feedback being generated at each step.

Cherenkov radiation (CR) generated by a charge moving through a hollow conical target made of dielectric material is analyzed. We consider two cases: the charge moves from the base of the cone to its top (“straight” cone) or from the top to the base (“inverted” cone). Unlike previous papers, a nonzero shift of the charge trajectory from the symmetry axis is taken into account which leads to generation of asymmetric CR. The most interesting effect is the phenomenon of “Cherenkov spotlight” which has been reported earlier for axially symmetric problems. This effect allows essential enhancement of the CR intensity in the far-field region by proper selection of the target’s parameters and charge velocity. Here we describe the influence of charge shift on CR farfield patterns paying the main attention to the “Cherenkov spotlight” regime. Influence of variation of the charge speed on this phenomenon is also investigated.

A rigorous approach for solving canonical circular open-ended dielectric-lined waveguide diffraction problems is presented. This is continuation of our recent paper [1] where a simpler case of uniform dielectric filling has been considered. Here we deal with the case of an open-ended circular waveguide with layered dielectric filling which is closer to potential applications. The presented method uses the solution of corresponding Wiener-Hopf-Fock equation and leads to an infinite linear system for reflection coefficients (S-parameters) of the waveguide, the latter can be efficiently solved numerically using the reducing technique. As a specific example directly applicable to beam-driven radiation sources based on dielectric-lined capillaries, diffraction of a slow TM symmetrical mode at the open end of the described waveguide is considered. A series of such modes forms the wakefield (Cherenkov radiation field) generated by a charged particle bunch during its passage along the vacuum channel axis. Calculated S-parameters were compared with those obtained from COMSOL simulation and an excellent agreement was shown. This method is expected to be very convenient for analytical investigation of various electromagnetic interactions of Terahertz (THz) waves (both free and guided) and charged particle bunches with slow-wave structures prospective in context of modern beam-driven THz emitters, THz accererators and THz-based bunch manipulation and bunch diagnostic systems.

Simulating the brain-body-environment trinity in closed loop is an attractive proposal to investigate how perception, motor activity and interactions with the environment shape brain activity, and vice versa. The relevance of this embodied approach, however, hinges entirely on the modeled complexity of the various simulated phenomena. In this article, we introduce a software framework that is capable of simulating large-scale, biologically realistic networks of spiking neurons embodied in a biomechanically accurate musculoskeletal system that interacts with a physically realistic virtual environment. We deploy this framework on the high performance computing resources of the EBRAINS research infrastructure and we investigate the scaling performance by distributing computation across an increasing number of interconnected compute nodes. Our architecture is based on requested compute nodes as well as persistent virtual machines; this provides a high-performance simulation environment that is accessible to multi-domain users without expert knowledge, with a view to enable users to instantiate and control simulations at custom scale via a web-based graphical user interface. Our simulation environment, entirely open source, is based on the Neurorobotics Platform developed in the context of the Human Brain Project, and the NEST simulator. We characterize the capabilities of our parallelized architecture for large-scale embodied brain simulations through two benchmark experiments, by investigating the effects of scaling compute resources on performance defined in terms of experiment runtime, brain instantiation and simulation time. The first benchmark is based on a large-scale balanced network, while the second one is a multi-region embodied brain simulation consisting of more than a million neurons and a billion synapses. Both benchmarks clearly show how scaling compute resources improves the aforementioned performance metrics in a near-linear fashion. The second benchmark in particular is indicative of both the potential and limitations of a highly distributed simulation in terms of a trade-off between computation speed and resource cost. Our simulation architecture is being prepared to be accessible for everyone as an EBRAINS service, thereby offering a community-wide tool with a unique workflow that should provide momentum to the investigation of closed-loop embodiment within the computational neuroscience community.

Cherenkov radiation (CR) generated by a charge moving along one of the faces of a dielectric prism is analyzed. Unlike our previous papers, here we suppose that the charge moves from the the prism ``nose'' to its base. For CR analysis, we use the technique described in our previous papers and called the ``aperture method''. However, here we develop a new version of this technique which is suitable for objects with plane faces: it utilizes field expansion only over plane waves inside the object. This approach is especially convenient for objects having two or more plane interfaces on which the waves are reflected and/or refracted. Using this technique, we obtain the electromagnetic field distribution over the aperture and then apply Stratton-Chu formulas (aperture integrals). Further, the main attention is paid to the calculation of the radiation field in the Fraunhofer (far-field) area. It is notable that we obtain expressions for corresponding Fourier transforms in the form of single integrals. Using them, the series of typical angular diagrams are computed and physical conclusions are made.

Radiation of charged particles moving in the presence of dielectric targets is of essential importance for various applications in accelerator and beam physics. As a rule, the sizes of these targets are much larger than the wavelengths under consideration. This fact gives an obvious small parameter of the problem and allows developing approximate methods for analysis. Here we apply one such method (called the “aperture method” in our preceding papers) to analysis of Cherenkov radiation from a charge flying through a vacuum channel in a dielectric sphere. We present analytical results and describe the main physical effects. Typical angular and radial distributions of the radiation field are also presented. In particular, it is shown that the field has an expressed maximum at a certain distance from the sphere. Special attention is paid to the far-field area where the radiation is formed, and corresponding angular distribution does not depend on the distance from the sphere.

Radiation generated by a charge moving through a vacuum channel in a dielectric cone is analyzed. It is assumed that the charge moves through the cone from the apex side to the base side (the case of inverted cone). The cone size is supposed to be much larger than the wavelengths under consideration. We calculate the wave field outside the target using the aperture method developed in our previous papers. Contrary to the problems considered earlier, here the wave which incidences directly on the aperture is not the main wave, while the wave once reflected from the lateral surface is much more important. The general formulas for the radiation field are obtained, and the particular cases of the ray-optics area and the Fraunhofer area are analyzed. Significant physical effects including the phenomenon of "Cherenkov spotlight" are discussed. In particular it is shown that the Cherenkov spotlight regime allows for reaching the most efficient radiation for the given target with the largest intensity and smallest divergence in the far-field region. Moreover, owing to the inverted cone geometry, this effect can be realized for arbitrary charge velocity, including the ultrarelativistic case, by proper selection of the cone material and the apex angle. Typical radiation patterns in the far-field area are demonstrated.

An elegant and convenient rigorous approach for solving circular open-ended dielectric-loaded waveguide diffraction problems is presented. It uses the solution of corresponding Wiener-Hopf-Fock equation to obtain an infinite linear system for reflection coefficients (S-parameters) of the waveguide. This system can be efficiently solved numerically using the reduction technique. As a specific example, diffraction of a TM symmetrical mode at the open end of a circular waveguide with uniform dielectric filling is considered. A series of such modes represent the wakefield (Cherenkov radiation field) generated by a charged particle bunch during its passage through the waveguide. Calculated S-parameters were compared with those obtained from COMSOL simulation and an excellent agreement is shown. Advantages of using this method for investigation of various waveguide structures prospective in context of modern beam-driven Terahertz radiation sources development is discussed.

A theoretical approach for describing the electromagnetic radiation produced by a prolonged electron bunch propagating in the lattice of metallic wires of finite length is presented. This approach is based on the vibrator antenna theory and involves the approximate solving of Hallen's integral equation. For a single wire, it is also supposed that a wire is sufficiently thin and charge motion is relativistic. For many-wire structures, the approximation similar to the kinematic approach of the parametric x-ray radiation theory is additionally applied. The validity of the method is verified by numerical simulations with comsoL Multiphysics. Possible applications of the interaction between charged particle bunches and artificial wire structures arc discussed.

A theoretical approach for describing the electromagnetic radiation produced by prolonged electron bunch propagating in the lattice of metallic wires of finite length is presented. This approach is based on vibrator antenna theory and involves approximate solving of Hallen's integral equation. For a single wire, it is also supposed that a wire is sufficiently thin and charge motion is relativistic. For many-wire structures, the approximation similar to kinematic approach of parametric X-ray radiation (PXR) theory is additionally applied. The validity of the method is verified by numerical simulations with COMSOL Multiphysics. Possible applications of interaction between charged particle bunches and artificial wire structures are discussed.

Received 9 September 2019DOI:https://doi.org/10.1103/PhysRevAccelBeams.22.109901Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam diagnosticsElectromagnetic field calculationsPhysical SystemsRadiation from moving chargesAccelerators & Beams

We analyze the wave field of a charged particle bunch moving in a circular waveguide consisting of two parts: the first one has a corrugated wall and the other one has a smooth wall. It is assumed that the period and the depth of the corrugation are much less than the waveguide radius and wavelengths under consideration. The influence of corrugation on the electromagnetic field is analyzed using the method of equivalent boundary conditions (EBC). The cases of the bunch moving in both directions inside of such a waveguide are considered. We obtain analytical expressions for the main part of the field having discrete spectrum. Figures of a typical mode distribution of radiation are presented. We also perform numerical simulations in software package CST Particle Studio. Comparison of analytical and numerical results confirms the validity of the EBC method.

A theoretical investigation of radiation field produced by a charge moving through the dielectric concentrator for Cherenkov radiation is performed for the general case where a charge trajectory is shifted with respect to the target axis. The idea of dielectric target with specific profile of the outer surface was presented and investigated in our previous papers for the symmetric case. Here we show how nonsymmetric field components generated in the bulk of the target affect field distribution near the focus where strong concentration of the energy occurs. Possible applications of this target are discussed.

We consider a charged particle bunch passing along the axis of a semi-infinite open-ended circular vacuum waveguide placed into a collinear infinite waveguide with larger radius. The rigorous solution of this problem is constructed using residue-calculus technique. Analytical expressions for the Fourier harmonics of the field components are obtained in each domain of the structure. Numerical integration over frequency is also performed and time-domain field dependencies are obtained. The analytical results are compared with the results of the numerical simulation and an excellent agreement is observed. In particular, we report on the effect of a "bunch image," a radiation pulse is generated in the coaxial area and has the form of the transverse electric field correlating with the longitudinal charge distribution within the bunch.

This paper is devoted to the analysis of electromagnetic field excited by a charge moving in a circular waveguide, which consists of two semi-infinite parts. The charge moves with a constant velocity along the waveguide axis from the partially dielectric section into the homogeneous one. It is assumed that Cherenkov radiation is generated in the bilayer section. The total field is represented as a sum of a known forced field that is the field of the charge in the infinite regular waveguide and a free field resulting from the presence of the transverse boundary. The infinite system of algebraic equations for amplitudes of the free-field modes is derived. The further analysis is conducted using numerical calculations. Special attention is given to the study of the so-called Cherenkov-transition radiation (CTR) within the homogeneous part of the waveguide volume. Typical distributions of CTR over frequencies and modes are presented for the case when the channel and the homogeneous area are free of medium. Analytical results obtained for the point charge are generalized for the charged bunch with an arbitrary profile and verified using direct simulations for the case of Gaussian bunch.

We consider the electromagnetic field of a point charged particle moving along the axis of a cylindrical waveguide from a homogeneously filled area to a dielectric loading area having an axially symmetrical channel. We are interested in studying the Cherenkov radiation excited in the bilayer area. The solution is performed by expanding the field in each area in a series of orthogonal eigenmodes. The main attention is focused on investigation of the wave field in the bilayer section. We show that, at a given observation point, the "reduced wakefield" is simplified with time (the number of modes decreases). The obtained results are generalized for the case of a bunch with Gaussian longitudinal profile. The typical numerical results for wakefield formation process are presented. These results agree with simulations done by the industry standard electromagnetic code CST Particle Studio.

Surface waves generated by a charged-particle bunch at the semi-infinite planar periodic wire structure are analyzed. It is supposed that the bunch moves parallel to the edge of the structure. The influence of the grid is described by the averaged boundary conditions. The analytical results are given for a general case, which takes into account the finite period and wires radius. It is shown that the surface waves excited by the bunch propagate along wires with the speed of light in vacuum. The number and the structure of these surface waves depend on relative location of the bunch path and the grid. One type of wave is always excited, but its magnitude decreases with distance from the bunch path to the structure edge. If the bunch projection falls on the half-plane occupied by wires, then additionally three surface waves are generated: two of them are equivalent to ones excited by the bunch moving along infinite wire grid and another one represents the surface wave reflected from the edge. The analysis of the surface waves shows that their structure allows for determination of the length of the bunch. Typical numerical results are presented.

Recently we have reported on axisymmetric dielectric concentrator for Cherenkov radiation that focuses almost the whole radiation in the vicinity of the given point (focus) located on the trajectory of the charge [1]. Particularly, we have shown that this structure can increase the field up to two orders of magnitude. In this report we continue investigation of this concentrating target and analyse in more detail the field near the focal point depending on parameters of the target. INTRODUCTION Various dielectric targets are considered as candidates for development of modern non-invasive system of bunch diagnostics [2]. However, rigorous theory describing radiation processes for most of targets’ geometries cannot be developed. Therefore, various approximate approaches are considered [3-6]. We have applied our original approach to calculate the shape of axisymmetric dielectric target concentrating most of generated Cherenkov radiation (CR) in a small vicinity of a focus point. We call this target “dielectric concentrator for CR” [1]. Here we proceed with investigation of this structure and perform analysis of the field components near the focal point. THEORY Figure 1 shows x z − cut of the axisymmetric dielectric target with cylindrical channel (where a charge q passes) and specific form of the outer boundary. In the coordinate system shown in Fig. 1, this hyperbolic surface 0 x , 0 y , 0 z is determined as 0 0 0 0 0 0 cos , sin , ( )sin , ( ) cos , f x y r z z r ρ φ ρ φ ρ θ θ θ θ = = = = + (1) [ ] 1 ( ) (1 ) 1 sin( ) r f n n θ α θ − = − + + , (2) where r is a distance from f z z = to the surface, 0 n εμ = > , 1 sin ( ) n α β − = , 1 Vc β − = (V is a charge velocity and c is a speed of light in vacuum), f is a focal parameter, i.e. minimal distance from the focus to the surface, (3 2 ) f r π α = − . For θ satisfying sin( ) 1 / n α θ + = − we obtain r →∞ , and this angle corresponds to the asymptote of hyperbola. In order to obtain the outer surface of the final target, we should take a piece of (2) for [ ] min max , θ θ θ ∈ , where 0 max ( ) a ρ θ = ( a is a channel radius), 0 min max ( ) x ρ θ = , and rotate this piece over z axis. Length of the target max z is max 0 max 0 min ( ) ( ) z z z θ θ = − . (3) Consideration of the refracted rays shows that they converge exactly to the focus point, while ray optics formulas give divergent field magnitude [1]: || 1 exp , 1 ( ) i H H T l l r c φω φω ω θ ∗   ≈   −   (4) where l is a distance from the surface to the observation point along the ray, || T is a Fresnel transmission coefficient, [ ] 1 || 2cos cos cos i i t T n θ θ θ − = + , (5) and Hφω ∗ is the field at the inner side of the surface [7]: ( ) ( ) 1 1 exp 2 iq H sH s i z c c φω ω η ρ β ∗ ∗ ∗   =     , (6) 1 2 ( ) 1 s c ω β εμβ − = − , Im 0 s ≥ , 1 2 ( ) 1 k c ω β β − = − , ( ) ( ) ( ) ( ) ( ) ( ) 2 1 1 1 0 0 1 2 2 ( ) (1 ) (1 ) i a I ka H sa sI ka H sa π η εμβ β ε − = − + − , (7) ρ∗ and z∗ are cylindrical coordinates of the ray start point at the surface. Since for the focus point there is an equality ( ) l r θ = , we obtain divergence in (4). Figure 1: Geometry of concentrator ( x z − cut). vacuum