Articoli di riviste: "Particle accelerator simulation"

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Barač, Rocco, e Toni Šćulac. "Development of a simple algorithm for linear accelerator construction and simulation". St open 4 (31 agosto 2023): 1–15. http://dx.doi.org/10.48188/so.4.13.

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Aim: To develop a simple algorithm that accurately constructs and simulates an Alvarez-type linear accelerator given the initial conditions and number of accelerator parts.Methods: We wrote the algorithm in Python, a programming language with numerous useful math and science libraries, and the ability to use classes and objects. The particles were accelerated in electric fields (which we assumed to be constant within each cavity at any given moment) to allow for a comparison of numerical results with an analytic expression. No magnetic fields were present in the simulations used in this article, and the particle beams were instead focused by using collimators. The algorithm first constructed the accelerator by guessing the appropriate length of each segment until it found optimal lengths for accelerating most particles in the beam. Once constructed, the accelerator could accelerate beams of particles and the results could be analyzed.Results: The algorithm successfully constructed multiple different accelerators from the initially given conditions. The first two simulations had arbitrary accelerators in which hydrogen and lead ions were accelerated, and the results were in line with expectations from the analytic solution. The largest simulation was that of CERN’s Linac4 accelerator, which produced results similar to those found in the real world.Conclusion: Significant results could be obtained even with an algorithm as simple as the one described here. The algorithm could be further improved by using a more realistic potential inside the accelerator cavities, and more particles could pass through if magnetic fields which focus the beam were turned on

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Martinez de la Ossa, A., R. W. Assmann, M. Bussmann, S. Corde, J. P. Couperus Cabadağ, A. Debus, A. Döpp et al. "Hybrid LWFA–PWFA staging as a beam energy and brightness transformer: conceptual design and simulations". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, n. 2151 (24 giugno 2019): 20180175. http://dx.doi.org/10.1098/rsta.2018.0175.

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We present a conceptual design for a hybrid laser-driven plasma wakefield accelerator (LWFA) to beam-driven plasma wakefield accelerator (PWFA). In this set-up, the output beams from an LWFA stage are used as input beams of a new PWFA stage. In the PWFA stage, a new witness beam of largely increased quality can be produced and accelerated to higher energies. The feasibility and the potential of this concept is shown through exemplary particle-in-cell simulations. In addition, preliminary simulation results for a proof-of-concept experiment in Helmholtz-Zentrum Dresden-Rossendorf (Germany) are shown. This article is part of the Theo Murphy meeting issue ‘Directions in particle beam-driven plasma wakefield acceleration’.

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Iwamoto, Masanori, Takanobu Amano, Yosuke Matsumoto, Shuichi Matsukiyo e Masahiro Hoshino. "Particle Acceleration by Pickup Process Upstream of Relativistic Shocks". Astrophysical Journal 924, n. 2 (1 gennaio 2022): 108. http://dx.doi.org/10.3847/1538-4357/ac38aa.

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Abstract Particle acceleration at magnetized purely perpendicular relativistic shocks in electron–ion plasmas is studied by means of two-dimensional particle-in-cell simulations. Magnetized shocks with the upstream bulk Lorentz factor γ 1 ≫ 1 are known to emit intense electromagnetic waves from the shock front, which induce electrostatic plasma waves (wakefield) and transverse filamentary structures in the upstream region via stimulated/induced Raman scattering and filamentation instability, respectively. The wakefield and filaments inject a fraction of the incoming particles into a particle acceleration process, in which particles are once decoupled from the upstream bulk flow by the wakefield, and are picked up again by the flow. The picked-up particles are accelerated by the motional electric field. The maximum attainable Lorentz factor is estimated as γ max , e ∼ α γ 1 3 for electrons and γ max , i ∼ ( 1 + m e γ 1 / m i ) γ 1 2 for ions, where α ∼ 10 is determined from our simulation results. α can increase up to γ 1 for a weakly magnetized shock if γ 1 is sufficiently large. This result indicates that highly relativistic astrophysical shocks such as external shocks of gamma-ray bursts can be an efficient particle accelerator.

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Shishlo, Andrei, Sarah Cousineau, Jeffrey Holmes e Timofey Gorlov. "The Particle Accelerator Simulation Code PyORBIT". Procedia Computer Science 51 (2015): 1272–81. http://dx.doi.org/10.1016/j.procs.2015.05.312.

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Timalsina, R. "Structural Energy Distribution and Particle Phase Stability Study of Longitudinal Dynamics of a Simple Linear Proton Accelerator". Journal of Nepal Physical Society 7, n. 1 (7 maggio 2021): 66–72. http://dx.doi.org/10.3126/jnphyssoc.v7i1.36978.

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This paper presents the study of longitudinal beam dynamics of a simple linear proton accelerator and simulation results for a model linear accelerator (LINAC) using MATLAB. The study part of the transition energy, particle acceleration, transit time factor, RF factor, and momentum compaction are discussed. For the simulation, the model LINAC is built using unit cells and the unit cell consists of Quadrupole doublet and acceleration cavity. Model LINAC’s basic setup is present and the simulation is based on the single-particle analysis. The robustness of the model LINAC tested to operate varying different parameters like initial arrival phase and input energy. The criteria to measure the robustness of the model LINAC are to check the kinetic energy at the end of the LINAC and the transverse stability of the transfer matrices of each cell. The paper also presents the theoretical analysis of phase stability at both below and above transition energy. The stability of small and larger amplitude oscillations are present and simulation results for different particles each starting with different amplitudes observed, where the large amplitude oscillation falls outside of the separatrix.

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Sullivan, Kelley D., Antara Sen e M. C. Sullivan. "Investigating the magnetic field outside small accelerator magnet analogs via experiment, simulation, and theory". American Journal of Physics 91, n. 6 (1 giugno 2023): 432. http://dx.doi.org/10.1119/5.0068701.

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Particle accelerators use powerful and complex magnetic fields to turn, shape, and eventually collide beams of near-light-speed particles, yet the fundamental magnetic principles behind the accelerator magnets can be understood by undergraduate students. In this paper, we use small-scale accelerator magnet analogs in a multi-faceted, low-cost exploration of the magnetic field exterior to accelerator magnets. These fields are best understood using the multipole expansion of the field. If we assume that the magnetic field is created by ideal magnetic dipoles, we can derive a theoretical model that shows that each accelerator magnet configuration is dominated by a single multipole moment and obeys B∝1/rl+2, where l is the multipole order (with l=1,2,3, and 4 for the dipole, quadrupole, octopole, and hexadecapole moments, respectively). Using commercially available NdFeB magnets and the magnetic field sensor inside a smartphone, we experimentally verify the power-law dependence of the accelerator magnet configurations. Finally, we use the open-source Python library Magpylib to simulate the magnetic field of the permanent magnet configurations, showing good agreement among theory, experiment, and simulation.

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Planche, Thomas, e Paul M. Jung. "Symplectic and self-consistent algorithms for particle accelerator simulation". International Journal of Modern Physics A 34, n. 36 (30 dicembre 2019): 1942027. http://dx.doi.org/10.1142/s0217751x19420272.

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In this paper, we review three methods to construct symplectic and self-consistent multiparticle algorithms to simulate space–charge effects in particle accelerators. The first method is based on a discrete multiparticle Hamiltonian with an interaction term that depends explicitly on the coordinates of the macroparticles. The second method derives from Low’s Lagrangian for a collisionless plasma. The third method is based on a corresponding collisionless Hamiltonian. The last two methods have been mostly developed by the plasma physics community, but are equally applicable to accelerator physics problems.

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Ge, Lixin, Zenghai Li, Cho-Kuen Ng e Liling Xiao. "High Performance Computing in Parallel Electromagnetics Simulation Code suite ACE3P". Applied Computational Electromagnetics Society 35, n. 11 (4 febbraio 2021): 1332–33. http://dx.doi.org/10.47037/2020.aces.j.351135.

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A comprehensive set of parallel finite-element codes suite ACE3P (Advanced Computational Electromagnetics 3D Parallel) is developed by SLAC for multi-physics modeling of particle accelerators running on massively parallel computer platforms for high fidelity and high accuracy simulation. ACE3P enables rapid virtual prototyping of accelerator and RF component design, optimization and analysis. Advanced modeling capabilities have been facilitated by implementations of novel algorithms for numerical solvers. Code performance on state-of-the-art high performance computing (HPC) platforms for large-scale RF modeling in accelerator applications will be presented in this paper. All the simulations have been performed on the supercomputers at National Energy Research Computer Center (NERSC).

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Fuchs, M., G. Andonian, O. Apsimon, M. Büscher, M. C. Downer, D. Filippetto, A. Lehrach et al. "Plasma-based particle sources". Journal of Instrumentation 19, n. 01 (1 gennaio 2024): T01004. http://dx.doi.org/10.1088/1748-0221/19/01/t01004.

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Abstract High-brightness particle beams generated by advanced accelerator concepts have the potential to become an essential part of future accelerator technology. In particular, high-gradient accelerators can generate and rapidly accelerate particle beams to relativistic energies. The rapid acceleration and strong confining fields can minimize irreversible detrimental effects to the beam brightness that occur at low beam energies, such as emittance growth or pulse elongation caused by space charge forces. Due to the high accelerating gradients, these novel accelerators are also significantly more compact than conventional technology. Advanced accelerators can be extremely variable and are capable of generating particle beams with vastly different properties using the same driver and setup with only modest changes to the interaction parameters. So far, efforts have mainly been focused on the generation of electron beams, but there are concepts to extend the sources to generate spin-polarized electron beams or positron beams. The beam parameters of these particle sources are largely determined by the injection and subsequent acceleration processes. Although, over the last decade there has been significant progress, the sources are still lacking a sufficiently high 6-dimensional (D) phase-space density that includes small transverse emittance, small energy spread and high charge, and operation at high repetition rate. This is required for future particle colliders with a sufficiently high luminosity or for more near-term applications, such as enabling the operation of free-electron lasers (FELs) in the X-ray regime. Major research and development efforts are required to address these limitations in order to realize these approaches for a front-end injector for a future collider or next-generation light sources. In particular, this includes methods to control and manipulate the phase-space and spin degrees-of-freedom of ultrashort plasma-based electron bunches with high accuracy, and methods that increase efficiency and repetition rate. These efforts also include the development of high-resolution diagnostics, such as full 6D phase-space measurements, beam polarimetry and high-fidelity simulation tools. A further increase in beam luminosity can be achieve through emittance damping. Emittance cooling via the emission of synchrotron radiation using current technology requires kilometer-scale damping rings. For future colliders, the damping rings might be replaced by a substantially more compact plasma-based approach. Here, plasma wigglers with significantly stronger magnetic fields are used instead of permanent-magnet based wigglers to achieve similar damping performance but over a two orders of magnitude reduced length.

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Niedermayer, Uwe, A. Adelmann, S. Bettoni, M. Calvi, M. Dehler, E. Ferrari, F. Frei et al. "Challenges in simulating beam dynamics of dielectric laser acceleration". International Journal of Modern Physics A 34, n. 36 (26 novembre 2019): 1942031. http://dx.doi.org/10.1142/s0217751x19420314.

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Dielectric Laser Acceleration (DLA) achieves the highest gradients among structure-based electron accelerators. The use of dielectrics increases the breakdown field limit, and thus the achievable gradient, by a factor of at least 10 in comparison to metals. Experimental demonstrations of DLA in 2013 led to the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. In ACHIP, our main goal is to build an accelerator on a silicon chip, which can accelerate electrons from below 100 keV to above 1 MeV with a gradient of at least 100 MeV/m. For stable acceleration on the chip, magnet-only focusing techniques are insufficient to compensate the strong acceleration defocusing. Thus, spatial harmonic and Alternating Phase Focusing (APF) laser-based focusing techniques have been developed. We have also developed the simplified symplectic tracking code DLAtrack6D, which makes use of the periodicity and applies only one kick per DLA cell, which is calculated by the Fourier coefficient of the synchronous spatial harmonic. Due to coupling, the Fourier coefficients of neighboring cells are not entirely independent and a field flatness optimization (similarly as in multi-cell cavities) needs to be performed. The simulation of the entire accelerator on a chip by a Particle In Cell (PIC) code is possible, but impractical for optimization purposes. Finally, we have also outlined the treatment of wake field effects in attosecond bunches in the grating within DLAtrack6D, where the wake function is computed by an external solver.

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XIA, G., R. ASSMANN, R. A. FONSECA, C. HUANG, W. MORI, L. O. SILVA, J. VIEIRA, F. ZIMMERMANN e P. MUGGLI. "A proposed demonstration of an experiment of proton-driven plasma wakefield acceleration based on CERN SPS". Journal of Plasma Physics 78, n. 4 (7 febbraio 2012): 347–53. http://dx.doi.org/10.1017/s0022377812000086.

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AbstractThe proton bunch-driven plasma wakefield acceleration (PWFA) has been proposed as an approach to accelerate an electron beam to the TeV energy regime in a single plasma section. An experimental program has been recently proposed to demonstrate the capability of proton-driven PWFA by using existing proton beams from the European Organization for Nuclear Research (CERN) accelerator complex. At present, a spare Super Proton Synchrotron (SPS) tunnel, having a length of 600 m, could be used for this purpose. The layout of the experiment is introduced. Particle-in-cell simulation results based on realistic SPS beam parameters are presented. Simulations show that working in a self-modulation regime, the wakefield driven by an SPS beam can accelerate an externally injected ~10 MeV electrons to ~2 GeV in a 10-m plasma, with a plasma density of 7 × 1014 cm−3.

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LAGER, DARREL L., HAL R. BRAND e WILLIAM J. MAURER. "AN EXPERT SYSTEM FOR TUNING PARTICLE BEAM ACCELERATORS". International Journal of Pattern Recognition and Artificial Intelligence 04, n. 03 (settembre 1990): 357–69. http://dx.doi.org/10.1142/s0218001490000228.

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An expert system that acts as an intelligent assistant to operators tuning a particle beam accelerator was developed. The system incorporates three approaches to tuning: (1) Duplicating within a software program the reasoning and the procedures used by an operator to tune an accelerator. This approach has been used to steer particle beams through the transport section of Lawrence Livermore National Laboratory's Advanced Test Accelerator and through the injector section of the Experimental Test Accelerator. (2) Using a model to simulate the position of a beam in an accelerator. The simulation is based on data taken directly from the accelerator while it is running. This approach will ultimately be used by operators of the Experimental Test Accelerator to first compare actual and simulated beam performance in real time, then to determine which set of parameters is optimum in terms of centering the beam, and finally to feed those parameters to the accelerator. Operators can also use the model to determine if a component has failed. (3) Using a mouse to manually select and control the magnets that steer the beam. Operators on the Experimental Test Accelerator can also use the mouse to call up windows that display the horizontal and vertical positions of the beam as well as its current.

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Markov, P. I., R. R. Kniaziev e G. V. Sotnikov. "Acceleration and focusing of positron bunch in a dielectric wakefield accelerator with plasma in transport channel". Journal of Instrumentation 17, n. 11 (1 novembre 2022): P11013. http://dx.doi.org/10.1088/1748-0221/17/11/p11013.

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Abstract The paper presents the results of numerical particle-in-cell simulation of the positron bunch focusing during acceleration in a plasma dielectric wakefield accelerator. The wakefield is excited by drive electron bunch in quartz dielectric tube, embedded in a cylindrical metal waveguide. The internal area of the dielectric tube is filled with plasma having in the general case the paraxial vacuum channel. Two different models of the plasma density radius-relationship are investigated: the homogeneous model and the inhomogeneous dependence characterized the capillary discharge. Results of the numerical particle-in-cell simulation show that a simultaneous acceleration and focusing of the test positron bunch in the wakefield is possible. The dependence of transport and acceleration of the positron bunch with change in the size of vacuum channel, waveguide length and the plasma density-radius model is studied.

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Plura, Saskia, Mirco Christmann, Luca Doria e Achim Denig. "Search for Light Dark Matter with the DarkMESA Experiment". EPJ Web of Conferences 303 (2024): 05006. http://dx.doi.org/10.1051/epjconf/202430305006.

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The search for Dark Matter is an integral part of New Physics searches, however, Dark Matter has yet to be observed directly. Theoretical models provide a large parameter space for Dark Matter and allow for different properties of the particles. Models incorporating so-called portal interactions, where Dark Matter interacts with Standard Model particles through a mediator particle, are of special interest. Examples for these are Dark Photon and Axion models, which can be studied at low energy accelerator facilities. The DarkMESA experiment is a beam dump experiment located at the upcoming accelerator MESA at the JGU Mainz. The accelerator provides an electron beam of 155 MeV and 150 μA in extracted beam mode, which, along with the high-power beam dump of the P2 experiment, provides an ideal environment for Light Dark Matter searches. To accurately predict the expected reach and the impact of the detector design of the DarkMESA experiment on it with respect to different Dark Matter models, most notably Dark Photon and Axion mediated models, a Geant4 simulation is used. Here, the current status of the simulations is discussed.

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DILÃO, RUI. "NONLINEAR PHENOMENA IN CIRCULAR PARTICLE ACCELERATORS I: SEXTUPOLAR NONLINEARITIES". International Journal of Bifurcation and Chaos 03, n. 05 (ottobre 1993): 1083–102. http://dx.doi.org/10.1142/s021812749300091x.

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In this paper we relate the methods of the theory of dynamical systems to problems of accelerator design and optimization. It is written in review article style and any prior knowledge of accelerator physics is not required. We derive the Poincaré map for the equation of horizontal transverse motion of a test particle in a circular accelerator in the presence of any number of sextupolar nonlinearities. This map is studied within the framework of nonlinear dynamics and we identify several optimization strategies for the design of an accelerator magnet lattice. The dynamic aperture problem is analysed and we obtain, for a beam line with two sextupoles, the dependence of the dynamic aperture on the line parameters. The mechanisms of aperture reduction near rational values of the tune, ν0 = p/q ≠ 1/3, are due to the creation of heteroclinic tangles and do not affect the stability of the design orbit. For a machine with an arbitrary number of localized sextupolar fields, we obtain the dependence of the nonlinear tune on the amplitude of the particles and the parameters of the accelerator. The predictions for the nonlinear tune agree with the numerical simulations within the maximum relative error of 6% at large amplitudes (~ dynamic aperture) and within the relative error range 1%–2% at intermediate amplitudes (~ half dynamic aperture).

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Tapan, I., e F. B. Pilicer. "Silicon tracker simulation for the Turkish Accelerator Center particle factory". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 765 (novembre 2014): 240–43. http://dx.doi.org/10.1016/j.nima.2014.05.100.

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Лавлинский, V. Lavlinskiy, Савченко e Andrey Savchenko. "APPROACH OF 3D SIMULATION AN EXPERIMENTAL COMPLEX WITH CHARGED-PARTICLE ACCELERATOR". Modeling of systems and processes 8, n. 4 (11 maggio 2016): 34–38. http://dx.doi.org/10.12737/19496.

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Bosco, F., M. Behtouei, O. Camacho, M. Carillo, E. Chiadroni, L. Faillace, L. Ficcadenti et al. "Advanced Studies for the Dynamics of High Brightness Electron Beams with the Code MILES". Journal of Physics: Conference Series 2687, n. 6 (1 gennaio 2024): 062018. http://dx.doi.org/10.1088/1742-6596/2687/6/062018.

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Abstract High brightness electron beams enable a wide spectrum of applications ranging from short wavelength radiation sources to high gradient wakefield acceleration. The rich dynamics that are intrinsic in charged particles accelerated in complex systems require a careful description in the analysis and design of a given machine, particularly regarding its stability. Numerous computer codes are in use by the accelerator community for such purposes. In particular, MILES is a simple tracking code we have developed that allows fast evaluations of collective effects in RF linacs. In this paper we extend the simple models previously developed to describe specific, diverse applications that can benefit from the fast simulation tools developed in MILES. Examples of this kind include particle driven acceleration schemes in a plasma where driver and witness beams propagate in the “comb” pulse-train configuration. Specifically, we investigate the self-induced fields excited within the X-band rf-linac stage of EuPRAXIA@SPARC_LAB. Further, we discuss additional advanced topics such as resistive wall wakefield effects in planar FEL undulators and their impact on the radiation emitted.

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Ramoisiaux, E., C. Hernalsteens, R. Tesse, E. Gnacadja, N. Pauly, M. Vanwelde e F. Stichelbaut. "Concrete shielding activation for proton therapy systems using BDSIM and FISPACT-II". Journal of Physics: Conference Series 2420, n. 1 (1 gennaio 2023): 012064. http://dx.doi.org/10.1088/1742-6596/2420/1/012064.

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Abstract Proton therapy systems are used worldwide for patient treatment and fundamental research. The generation of secondary particles when the beam interacts with the beamline elements is a well known issue. In particular, the energy degrader is the dominant source of secondary radiation. This poses new challenges for the concrete shielding of compact systems and beamline elements activation computation. We use a novel methodology to seamlessly simulate all the processes relevant to the activation evaluation. A realistic model of the system is developed using Beam Delivery Simulation (BDSIM), a Geant4-based particle tracking code that allows a single model to simulate primary and secondary particle tracking and all particle-matter interactions. The secondary particle fluxes extracted from the simulations are provided as input to FISPACT-II to compute the activation by solving the rate equations. This approach is applied to the Ion Beam Applications (IBA) Proteus®ONE (P1) system and the shielding of the proton therapy research centre of Charleroi, Belgium. Proton loss distributions are used to model the production of secondary neutrals inside the accelerator structure. Two models for the distribution of proton losses are compared for the computation of the clearance index at specific locations of the design. Results show that the variation in the accelerator loss models can be characterised as a systematic error.

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Büscher, Markus, Anna Hützen, Ilhan Engin, Johannes Thomas, Alexander Pukhov, Jürgen Böker, Ralf Gebel et al. "Polarized proton beams from a laser-plasma accelerator". International Journal of Modern Physics A 34, n. 36 (26 novembre 2019): 1942028. http://dx.doi.org/10.1142/s0217751x19420284.

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We report on the concept of an innovative laser-driven plasma accelerator for polarized proton (or deuteron) beams with a kinetic energy up to several GeV. In order to model the motion of the particle spins in the plasmas, these have been implemented as an additional degree of freedom into the Particle-in-Cell simulation code VLPL. For the experimental realization, a polarized HCl gas-jet target is under construction, where the degree of proton polarization is determined with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM/Shanghai.

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Crisp, Sophie, Alexander Ody e Pietro Musumeci. "Asymmetric Dual-Grating Dielectric Laser Accelerator Optimization". Instruments 7, n. 4 (7 dicembre 2023): 51. http://dx.doi.org/10.3390/instruments7040051.

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Although hundreds of keV in energy gain have already been demonstrated in dielectric laser accelerators (DLAs), the challenge of creating structures that can confine electrons for multiple millimeters remains. We focus here on dual gratings with single-sided drive, which have experimentally demonstrated energy modulation numerous times. Using a Finite-Difference Time-Domain simulation to find the fields within various DLA structures and correlating these results with particle tracking simulation, we look at the impact of teeth height and width, as well as gap and offset, on the performance of these structures. We find a tradeoff between electron throughput and acceleration; however, we also find that for any given grating geometry, there is a gap and offset that will allow some charge acceleration. For our 780 nm laser wavelength, this results in a 1200 nm optimal gap size for most gratings.

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Babapour, Hamed, Somayeh Semyari, Masoumeh Yadollahi, Mehrsa Majdaeen, Razzagh Abedi-Firouzjah e Gholamreza Ataei. "Assessing the Effect of Directional Bremsstrahlung Splitting on the Output Spectra and Parameters Using BEAMnrc Monte Carlo Simulation Package". Biomedical Engineering and Computational Biology 13 (gennaio 2022): 117959722211384. http://dx.doi.org/10.1177/11795972221138473.

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Introduction: EGSnrc software package is one of the computational packages for Monte Carlo simulation in radiation therapy and has several subset codes. Directional bremsstrahlung splitting (DBS) is a technique that applies braking radiations in interactions in this software. This study aimed to evaluate the effect of this technique on the simulation time, uncertainty, particle number of phase-space data, and photon beam spectrum resulting from a medical linear accelerator (LINAC). Materials and methods: The gantry of the accelerator, including the materials and geometries of different parts, was simulated using the BEAMnrc code (a subset code in the EGSnrc package). The phase-space data were recorded in different parts of the LINAC. The DBS values (1, 10, 100, and 1000) were changed, and their effects were evaluated on the simulation parameters and output spectra. Results: Increasing the DBS value from 1 to 1000 resulted in an increase in the simulation time from 1.778 to 11.310 hours, and increasing the number of particles in the phase-space plane (5 590 732-180 328 382). When the DBS had been picked up from 1 to 100, the simulation uncertainty decreased by about 1.29%. In addition, the DBS increment value from 100 to 1000 leads to an increase in uncertainty and simulation time of about 0.71% and 315%, respectively. Conclusion: Although using the DBS technique reduces the simulation time or uncertainty, increasing the DBS from a specific value, equal to 100 in our study, increases simulation uncertainties and times. Therefore, we propose considering a specific DBS value as we obtained for the Monte Carlo simulation of photon beams produced by linear accelerators.

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Kluchevskaia, Yulia D., e Sergey M. Polozov. "Beam dynamics simulation in a linear accelerator for CERN Future Circular Collider". Cybernetics and Physics, Volume 9, 2020, Number 2 (30 settembre 2020): 98–102. http://dx.doi.org/10.35470/2226-4116-2020-9-2-98-102.

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Results of the beam dynamics simulation in a linear accelerator at full energy 1.5 – 2.0 GeV for an international project – CERN Future Circular Collider (FCCee) are presented. FCC is developing designs for a higher performance particle collider to extend the research currently being conducted at the Large Hadron Collider, once the latter reaches the end of its lifespan. Beam dynamics simulations done using BEAMDULAC-BL code developed in NRNU MEPhI. This code allows taking into account both the quasistatic and high-frequency self-field components.

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Gazis, Nick, Andrea Bignami, Emmanouil Trachanas, Melina Moniaki, Evangelos Gazis, Dimitrios Bandekas e Nikolaos Vordos. "Simulation Dosimetry Studies for FLASH Radiation Therapy (RT) with Ultra-High Dose Rate (UHDR) Electron Beam". Quantum Beam Science 8, n. 2 (24 maggio 2024): 13. http://dx.doi.org/10.3390/qubs8020013.

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FLASH-radiotherapy (RT) presents great potential as an alternative to conventional radiotherapy methods in cancer treatment. In this paper, we focus on simulation studies for a linear particle accelerator injector design using the ASTRA code, which permits beam generation and particle tracking through electromagnetic fields. Space charge-dominated beams were selected with the aim of providing an optimized generated beam profile and accelerator lattice with minimized emittance. The main results of the electron beam and ultra-high dose rate (UHDR) simulation dosimetry studies are reported for the FLASH mode radiobiological treatment. Results for the percentage depth dose (PDD) at electron beam energies of 5, 7, 15, 25, 50, 100 MeV and 1.2 GeV for Poly-methyl-methacrylate (PMMA) and water phantom vs. the penetration depth are presented. Additionally, the PDD transverse profile was simulated for the above energies, delivering the beam to the phantom. The simulation dosimetry results provide an UHDR electron beam under the conditions of the FLASH-RT. The performance of the beam inside the phantom and the dose depth depends on the linear accelerator beam’s energy and stability.

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Guidoni, S. E., J. T. Karpen e C. R. DeVore. "Spectral Power-law Formation by Sequential Particle Acceleration in Multiple Flare Magnetic Islands". Astrophysical Journal 925, n. 2 (1 febbraio 2022): 191. http://dx.doi.org/10.3847/1538-4357/ac39a5.

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Abstract We present a first-principles model of pitch-angle and energy distribution function evolution as particles are sequentially accelerated by multiple flare magnetic islands. Data from magnetohydrodynamic (MHD) simulations of an eruptive flare/coronal mass ejection provide ambient conditions for the evolving particle distributions. Magnetic islands, which are created by sporadic reconnection at the self-consistently formed flare current sheet, contract and accelerate the particles. The particle distributions are evolved using rules derived in our previous work. In this investigation, we assume that a prescribed fraction of particles sequentially “hops” to another accelerator and receives an additional boost in energy and anisotropy. This sequential process generates particle number spectra that obey an approximate power law at mid-range energies and presents low- and high-energy breaks. We analyze these spectral regions as functions of the model parameters. We also present a fully analytic method for forming and interpreting such spectra, independent of the sequential acceleration model. The method requires only a few constrained physical parameters, such as the percentage of particles transferred between accelerators, the energy gain in each accelerator, and the number of accelerators visited. Our investigation seeks to bridge the gap between MHD and kinetic regimes by combining global simulations and analytic kinetic theory. The model reproduces and explains key characteristics of observed flare hard X-ray spectra as well as the underlying properties of the accelerated particles. Our analytic model provides tools to interpret high-energy observations for missions and telescopes, such as RHESSI, FOXSI, NuSTAR, Solar Orbiter, EOVSA, and future high-energy missions.

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26

Collin, Jonathan, Jean-Michel Horodynski, Nicolas Arbor, Massimo Barbagallo, Federico Carminati, Giuliana Galli Carminati, Luca J. Tagliapietra e Abdel-Mjid Nourreddine. "Validation of Monte Carlo simulations by experimental measurements of neutron-induced activation in cyclotrons". EPJ Web of Conferences 288 (2023): 04025. http://dx.doi.org/10.1051/epjconf/202328804025.

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Nuclear activation is the process of production of radionuclides by irradiation. This phenomenon concerns particle accelerators used in various fields, from medical applications to industrial ones, both during operation and at the decommissioning phase. For more than three decades, the possibility of using cyclotrons for nuclear power generation and nuclear waste reduction has also been discussed, i.e. in the case of Accelerator-Driven Systems [1]. The radioprotection and dismantling issues of accelerator facilities, that have been raised recently, is even more potent for such installations. In our study, we are particularly interested in the activation due to secondary neutrons produced by (x,n) reactions, mostly (p,n) occurring in the accelerator’s components. This work focuses on the study of the radioactivity induced in various materials (V, Sc, Tb, W, Ta) irradiated by fast and thermal neutrons, in two different scenarios: through direct irradiation -with an AmBe sourceand around an operating cyclotron at the CYRCé facility (Strasbourg). A broad Monte Carlo study including FLUKA, GEANT4, PHITS and MCNP simulation has been performed, with and without a FISPACT-II coupling, to estimate the reaction rates and to trace the induced radioactivity in samples of known composition. The results of the simulations are compared with the values extracted in two dedicated experimental campaigns in which activated samples underwent high resolution gamma-ray spectrometry.

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27

Reggiani, Davide, Bertrand Blau, Rudolf Dölling, Pierre Andre Duperrex, Daniela Kiselev, Vadim Talanov, Jörg Welte e Michael Wohlmuther. "Improving beam simulations as well as machine and target protection in the SINQ beam line at PSI-HIPA". Journal of Neutron Research 22, n. 2-3 (20 ottobre 2020): 325–35. http://dx.doi.org/10.3233/jnr-200162.

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With a nominal beam power of nearly 1.4 MW, the PSI High Intensity Proton Accelerator (HIPA) is currently at the forefront of the high intensity frontier of particle accelerators. Key issues of this facility are minimization of beam losses as well as safe operation of the SINQ spallation source. Particular attention is being recently paid towards an improved understanding of the properties of the SINQ beam line by both enhancing the beam transport simulations and developing new diagnostic elements which can also, in some cases, preserve the target integrity by preventing too large beam current density, inaccurate beam steering or improper beam delivery. Moreover, part of the SINQ beam diagnostic concept is being rethought in order to include important missing devices like BPMs. On the simulation side, newly developed composite calculations involving general purpose particle transport programs like MCNPX and BDSIM will deliver insights about beam losses and transmission through collimators. All recent and planned developments of the SINQ beam line will be discussed in this contribution.

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28

Barranco, Javier, Yunhai Cai, David Cameron, Matthew Crouch, Riccardo De Maria, Laurence Field, Massimo Giovannozzi et al. "LHC@Home: a BOINC-based volunteer computing infrastructure for physics studies at CERN". Open Engineering 7, n. 1 (29 dicembre 2017): 379–93. http://dx.doi.org/10.1515/eng-2017-0042.

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AbstractThe LHC@Home BOINC project has provided computing capacity for numerical simulations to researchers at CERN since 2004, and has since 2011 been expanded with a wider range of applications. The traditional CERN accelerator physics simulation code SixTrack enjoys continuing volunteers support, and thanks to virtualisation a number of applications from the LHC experiment collaborations and particle theory groups have joined the consolidated LHC@Home BOINC project. This paper addresses the challenges related to traditional and virtualized applications in the BOINC environment, and how volunteer computing has been integrated into the overall computing strategy of the laboratory through the consolidated LHC@Home service. Thanks to the computing power provided by volunteers joining LHC@Home, numerous accelerator beam physics studies have been carried out, yielding an improved understanding of charged particle dynamics in the CERN Large Hadron Collider (LHC) and its future upgrades. The main results are highlighted in this paper.

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29

Pereslavtsev, P. E. "High-energy neutron transport file for the ²⁰⁹Bi isotope". Kerntechnik 66, n. 5-6 (1 ottobre 2001): 254–59. http://dx.doi.org/10.1515/kern-2001-0100.

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Abstract The simulation of the nuclear processes, occurring in media irradiated with high-energy particles, promote the elaboration of high-energy transport files. These files being used in versatile computer codes, such as MCNP, allow to simulate with high accuracy particle transport. High-energy transport files are very important for the investigation of accelerator-driven systems. The detailed description of the methods and codes used for the elaboration of the file for 209 Bi is presented in this paper.

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30

Yu, Yongbo, Wangbiao Ni, Gongfa Liu, Wei Xu, Chuan Li, Weiming Li e Ke Xuan. "Initial Application of Machine Learning for Beam Parameter Optimization at the Hefei Light Source II". Journal of Physics: Conference Series 2687, n. 7 (1 gennaio 2024): 072002. http://dx.doi.org/10.1088/1742-6596/2687/7/072002.

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Abstract Machine learning (ML) has become a valuable tool in particle accelerator control, with growing potential for beam parameter correction. In this study, we present preliminary ML applications at HLS-II, using Lasso regression for online tune correction and a neural network (NN) for beta function simulation correction. Both models were trained with supervised learning on measured beam parameter data, while an improved genetic algorithm optimized the NN structure. Our results show that the ML-based approach achieves competitive correction quality with fewer steps, making it a promising method for future particle accelerator applications and other fields.

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31

San Miguel Claveria, P., E. Adli, L. D. Amorim, W. An, C. E. Clayton, S. Corde, S. Gessner et al. "Betatron radiation and emittance growth in plasma wakefield accelerators". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, n. 2151 (24 giugno 2019): 20180173. http://dx.doi.org/10.1098/rsta.2018.0173.

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Abstract (sommario):

Beam-driven plasma wakefield acceleration (PWFA) has demonstrated significant progress during the past two decades of research. The new Facility for Advanced Accelerator Experimental Tests (FACET) II, currently under construction, will provide 10 GeV electron beams with unprecedented parameters for the next generation of PWFA experiments. In the context of the FACET II facility, we present simulation results on expected betatron radiation and its potential application to diagnose emittance preservation and hosing instability in the upcoming PWFA experiments. This article is part of the Theo Murphy meeting issue ‘Directions in particle beam-driven plasma wakefield acceleration’.

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32

Geng Shao-Fei, Tang De-Li, Zhao Jie e Qiu Xiao-Ming. "Particle-in-cell simulation of a cylindrical Hall anode layer plasma accelerator". Acta Physica Sinica 58, n. 8 (2009): 5520. http://dx.doi.org/10.7498/aps.58.5520.

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33

Yuan, Y. T., K. J. Fan e Y. Jiang. "Cylindrical cavity design and particle-tracking simulation in cyclotron auto-resonance accelerator". Journal of Physics: Conference Series 1350 (novembre 2019): 012064. http://dx.doi.org/10.1088/1742-6596/1350/1/012064.

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34

Tapan, I., E. Pilicer e F. B. Pilicer. "Tracking parameter simulation for the Turkish accelerator center particle factory tracker system". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 831 (settembre 2016): 389–93. http://dx.doi.org/10.1016/j.nima.2016.04.064.

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35

Novikov, Lev S., Ekaterina N. Voronina, Vladimir N. Chernik, Natalia P. Chirskaya e Weigui Zhang. "Study on Atomic Oxygen Exposure and Hard Particle Impact of Polyimide Nanocomposites". International Journal of Nanoscience 19, n. 02 (11 ottobre 2019): 1950007. http://dx.doi.org/10.1142/s0219581x19500078.

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Atomic oxygen (AO) exposure and hard microparticle impact on polyimide nanocomposites were performed by a ground-based magnetoplasmodynamic accelerator and electrostatic accelerator, respectively. The computer simulation of the AO erosion of polyimide nanocomposites was carried out with Monte Carlo method. It is found that the polyimide nanocomposites are significantly more durable to AO exposure than the pure polyimide material. Besides, in the case of combined hard microparticle impact and AO exposure, the regions around craters created by hard microparticle impact are etched more intensively than the undamaged areas of the polyimide nanocomposite sample surface.

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36

Ruban, Yuliia, Ondrej Ploc, Jakub Šlegl, David Chvátil, Ivo Světlík, Lenka Tomášková e Lembit Sihver. "Reconstruction of high energy thunderstorm radiation effects on soil matrix using Monte Carlo simulations". EPJ Web of Conferences 292 (2024): 09002. http://dx.doi.org/10.1051/epjconf/202429209002.

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Due to their electromagnetic properties, thunderclouds can act as natural particle accelerators. Electrons accelerated in the thunderclouds can reach energies up to tens of MeV. Large populations of high energetic electrons formed by avalanche growth driven by electric fields in the Earth atmosphere called Relativistic Runaway Electron Avalanches (RREA) propagate through matter. They are decelerated and deflected in the course of collisions with particles in the atmosphere and emit gamma rays known as bremsstrahlung. The produced gamma rays can further trigger photonuclear reactions in the air and soil. This article reports on the work of project CRREAT (Research Centre of Cosmic Rays and Radiation Events in the Atmosphere), studying various lightning-related phenomena in various ways, both in situ and in the laboratory. This paper focuses on the simulation of the laboratory experiments at the Microtron accelerator in Prague and the neutron generator in Ostrava, where we irradiated various soil samples with 20 MeV electron beams. Experiments showed which radionuclides can be formed during the reactions of high-energy electrons with various soils and can be as targeted products in the thunderstorm radiation effect analysis. Radionuclides produced in exposed samples were measured using a highpurity germanium (HPGe) detector. A computer simulation was done with a simple source and sample geometry using the general-purpose 3D Monte Carlo code PHITS.

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37

Vnuchenko, A., J. Lettry, S. Mochalskyy, D. Wünderlich, U. Fantz, M. Lindqvist, A. Revel e T. Minea. "H^- beam formation simulation in negative ion source for CERN's Linac4 accelerator". Journal of Instrumentation 18, n. 08 (1 agosto 2023): C08001. http://dx.doi.org/10.1088/1748-0221/18/08/c08001.

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Abstract The caesiated surface negative ion (H-) source is the first element of CERN's LINAC4 a linear injector designed to accelerate negative hydrogen ions to 160 MeV. The IS03 ion source is operated at 35 mA beam intensity and reliably feeds CERN's accelerator chain, H- ions are generated via plasma volume and caesiated molybdenum (Cs-Mo) plasma electrode surface mechanisms. Studying the beam extraction region of this H- ion source is essential for optimizing the H- production. The 3D Particle-in-cell (PIC) Monte Carlo (MC) code ONIX (Orsay Negative Ion eXtraction [1]), written to study H- beam formation processes in neutral-beam injectors for fusion, has been adapted to single aperture accelerator H- sources. The code was modified to match the conditions of the beam formation and extraction regions of the Linac4 H- source [2]. A set of parameters was chosen to characterize the plasma and to match the specific volume and surface production modes. Simulated results of the extraction regions are presented and benchmarked with experimental results obtained at the Linac4 test stand [3].

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38

VAY, J. L., P. COLELLA, P. McCORQUODALE, B. VAN STRAALEN, A. FRIEDMAN e D. P. GROTE. "Mesh refinement for particle-in-cell plasma simulations: Applications to and benefits for heavy ion fusion". Laser and Particle Beams 20, n. 4 (ottobre 2002): 569–75. http://dx.doi.org/10.1017/s0263034602204139.

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Abstract (sommario):

The numerical simulation of the driving beams in a heavy ion fusion power plant is a challenging task, and simulation of the power plant as a whole, or even of the driver, is not yet possible. Despite the rapid progress in computer power, past and anticipated, one must consider the use of the most advanced numerical techniques, if we are to reach our goal expeditiously. One of the difficulties of these simulations resides in the disparity of scales, in time and in space, which must be resolved. When these disparities are in distinctive zones of the simulation region, a method which has proven to be effective in other areas (e.g., fluid dynamics simulations) is the mesh refinement technique. We discuss the challenges posed by the implementation of this technique into plasma simulations (due to the presence of particles and electromagnetic waves). We present the prospects for and projected benefits of its application to heavy ion fusion, in particular to the simulation of the ion source and the final beam propagation in the chamber. A collaboration project is under way at Lawrence Berkeley National Laboratory between the Applied Numerical Algorithms Group (ANAG) and the Heavy Ion Fusion group to couple the adaptive mesh refinement library CHOMBO developed by the ANAG group to the particle-in-cell accelerator code WARP developed by the Heavy Ion Fusion–Virtual National Laboratory. We describe our progress and present our initial findings.

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39

Hartmann, M., D. Kiselev, D. Reggiani, J. Snuverink, H. Zhang e M. Seidel. "Design of the 590 MeV proton beamline for the proposed TATTOOS isotope production target at PSI". Journal of Physics: Conference Series 2420, n. 1 (1 gennaio 2023): 012105. http://dx.doi.org/10.1088/1742-6596/2420/1/012105.

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Abstract IMPACT (Isotope and Muon Production with Advanced Cyclotron and Target Technologies) is a proposed initiative envisaged for the high-intensity proton accelerator facility (HIPA) at the Paul Scherrer Institute (PSI). As part of IMPACT, a radioisotope target station, TATTOOS (Targeted Alpha Tumour Therapy and Other Oncological Solutions) will allow the production of terbium radionuclides for therapeutic and diagnostic purposes. The proposed TATTOOS beamline and target will be located near the UCN (Ultra Cold Neutron source) target area, branching off from the main UCN beamline. In particular, the beamline is intended to operate at a beam intensity of 100 μA, requiring a continuous splitting of the main beam via an electrostatic splitter. Realistic beam loss simulations to verify safe operation have been performed and optimised using Beam Delivery Simulation (BDSIM), a Geant4 based tool enabling the simulation of beam transportation through magnets and particle passage through the accelerator. In this study, beam profiles, beam transmission and power deposits are generated and studied.

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40

Maslov, Vasyl I., Denys S. Bondar e Ivan N. Onishchenko. "Investigation of the Way of Phase Synchronization of a Self-Injected Bunch and an Accelerating Wakefield in Solid-State Plasma". Photonics 9, n. 3 (11 marzo 2022): 174. http://dx.doi.org/10.3390/photonics9030174.

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The electron acceleration, in a laser wakefield accelerator, controlled through plasma density inhomogeneity is studied on a basis of 2.5-dimensional particle-in-cell simulation. The acceleration requires a concordance of the density scale length and shift of the accelerated electron bunch relative to wake bubble during electron acceleration. This paper considers the excitation of a wakefield in plasma with a density equal to the density of free electrons in metals, solid-state plasma (the original idea of Prof. T. Tajima), in the context of studying the wakefield process. As is known in the wake process, as the wake bubble moves through the plasma, the self-injected electron bunch shifts along the wake bubble. Then, the self-injected bunch falls into the phase of deceleration of the wake wave. In this paper, support of the acceleration process by maintaining the position of the self-injected electron bunch using an inhomogeneous plasma is proposed. It is confirmed that the method of maintaining phase synchronization proposed in the article by using a nonuniform plasma leads to an increase in the accelerating gradient and energy of the accelerated electron bunch in comparison with the case of self-injection and acceleration in a homogeneous plasma.

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41

Abdul Haneefa, K., T. Siji Cyriac, M. M. Musthafa, R. Ganapathi Raman, V. T. Hridya, A. Siddhartha e K. K. Shakir. "FLUKA Monte Carlo for Basic Dosimetric Studies of Dual Energy Medical Linear Accelerator". Journal of Radiotherapy 2014 (24 luglio 2014): 1–7. http://dx.doi.org/10.1155/2014/343979.

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General purpose Monte Carlo code for simulation of particle transport is used to study the basic dosimetric parameters like percentage depth dose and dose profiles and compared with the experimental measurements from commercial dual energy medical linear accelerator. Varian Clinac iX medical linear accelerator with dual energy photon beams (6 and 15 MV) is simulated using FLUKA. FLAIR is used to visualize and edit the geometry. Experimental measurements are taken for 100 cm source-to-surface (SSD) in 50 × 50 × 50 cm3 PTW water phantom using 0.12 cc cylindrical ionization chamber. Percentage depth dose for standard square field sizes and dose profiles for various depths are studied in detail. The analysis was carried out using ROOT (a DATA analysis frame work developed at CERN) system. Simulation result shows good agreement in percentage depth dose and beam profiles with the experimental measurements for Varian Clinac iX dual energy medical linear accelerator.

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42

Feghhi, Seyed, e Zohreh Gholamzadeh. "A MCNP simulation study of neutronic calculations of spallation targets". Nuclear Technology and Radiation Protection 28, n. 2 (2013): 128–36. http://dx.doi.org/10.2298/ntrp1302128f.

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The accelerator driven system is an innovative reactor which is being considered as a dedicated high-level waste burner. The function of the spallation target in accelerator driven system is to convert the incident high-energy particle beam to low-energy neutrons. One of the quantities of most interest for practical purposes is the number of neutrons produced per proton in a spallation target. However, this vital value depends not only on the material, but on the size of the target as well, due to the internuclear cascade. The MCNPX 2.4 code can be used for spallation target computation. Some benchmark results have been compared with MCNPX 2.4 simulations to verify the code's potential for calculating various parameters of an accelerator driven system target. Using the computation method, neutron interaction processes such as loss, capture and (n, xn) into a spallation target have been studied for W, Ta, Pb, Bi, and LBE spallation targets in different target dimensions. With relative errors less than 10%, the numerical simulation provided by the MCNPX code agrees qualitatively with other simulation results previously carried out, qualifying it for spallation calculations. Among the studied targets, W and Ta targets resulted in a higher neutron spallation yield using lesser target dimensions. Pb, Bi, and LBE spallation targets behave similarly regarding the accessible leaked neutron yield on the outer surface of the spallation target. By use of a thicker target, LBE can compete with both W and Ta targets regarding the neutron yield parameter.

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43

Park, Sae-Hoon, Sang-Hoon Lee e Yu-Seok Kim. "Emittance Measurement for Beamline Extension at the PET Cyclotron". Science and Technology of Nuclear Installations 2016 (2016): 1–4. http://dx.doi.org/10.1155/2016/4697247.

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Particle-induced X-ray emission is used for determining the elemental composition of materials. This method uses low-energy protons (of several MeV), which can be obtained from high-energy (of tens MeV) accelerators. Instead of manufacturing an accelerator for generating the MeV protons, the use of a PET cyclotron has been suggested for designing the beamline for multipurpose applications, especially for the PIXE experiment, which has a dedicated high-energy (of tens MeV) accelerator. The beam properties of the cyclotron were determined at this experimental facility by using an external beamline before transferring the ion beam to the experimental chamber. We measured the beam profile and calculated the emittance using the pepper-pot method. The beam profile was measured as the beam current using a wire scanner, and the emittance was measured as the beam distribution at the beam dump using a radiochromic film. We analyzed the measurement results and are planning to use the results obtained in the simulations of external beamline and aligned beamline components. We will consider energy degradation after computing the beamline simulation. The experimental study focused on measuring the emittance from the cyclotron, and the results of this study are presented in this paper.

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44

Baran, Mateusz, Zbisław Tabor, Krzysztof Rzecki, Przemysław Ziaja, Tomasz Szumlak, Kamila Kalecińska, Jakub Michczyński, Bartłomiej Rachwał, Michael P. R. Waligórski e David Sarrut. "Application of Conditional Generative Adversarial Networks to Efficiently Generate Photon Phase Space in Medical Linear Accelerators of Different Primary Beam Parameters". Applied Sciences 13, n. 12 (16 giugno 2023): 7204. http://dx.doi.org/10.3390/app13127204.

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Abstract (sommario):

Successful application of external photon beam therapy in oncology requires that the dose delivered by a medical linear accelerator and distributed within the patient’s body is accurately calculated. Monte Carlo simulation is currently the most accurate method for this purpose but is computationally too extensive for routine clinical application. A very elaborate and time-consuming part of such Monte Carlo simulation is generation of the full set (phase space) of ionizing radiation components (mainly photons) to be subsequently used in simulating dose delivery to the patient. We propose a method of generating phase spaces in medical linear accelerators through learning, by artificial intelligence models, the joint multidimensional probability density distribution of the photon properties (their location in space, energy, and momentum). The models are conditioned with respect to the parameters of the primary electron beam (unique to each medical accelerator), which, through Bremsstrahlung, generates the therapeutical beam of ionizing radiation. Two variants of conditional generative adversarial networks are chosen, trained, and compared. We also present the second-best type of deep learning architecture that we studied: a variational autoencoder. Differences between dose distributions obtained in a water phantom, in a test phantom, and in real patients using generative-adversarial-network-based and Monte-Carlo-based phase spaces are very close to each other, as indicated by the values of standard quality assurance tools of radiotherapy. Particle generation with generative adversarial networks is three orders of magnitude faster than with Monte Carlo. The proposed GAN model, together with our earlier machine-learning-based method of tuning the primary electron beam of an MC simulator, delivers a complete solution to the problem of tuning a Monte Carlo simulator against a physical medical accelerator.

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45

Di Staso, G., H. J. H. Clercx, S. Succi e F. Toschi. "Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, n. 2080 (13 novembre 2016): 20160226. http://dx.doi.org/10.1098/rsta.2016.0226.

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Hybrid particle–continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier–Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’.

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46

Tichý, P., J. Adam, A. Baldin, P. Chudoba, W. Furman, S. Gustov, J. Khushvaktov et al. "Experimental investigation and Monte Carlo simulations of radionuclide production inside the Uranium spallation target QUINTA irradiated with a 660-MeV proton beam". EPJ Web of Conferences 204 (2019): 04003. http://dx.doi.org/10.1051/epjconf/201920404003.

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Abstract (sommario):

The accelerator-Driven-System (ADS) is very important to study the neutron field and radionuclide production inside simple-geometry uranium subcritical setups irradiated with high energy particle beams. A subcritical setup QUINTA was irradiated with the 660-MeV proton beam from Phasotron accelerator at the Joint Institute for Nuclear Research (JINR). The radionuclide production in the region along the beam axis was investigated by the activation technique. The aim was to compare (n,x) with (p,x) reactions using activation detectors of 59Co and natPb, and compare experimental results with the calculated results using Monte Carlo simulation code MCNPX 2.7.

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47

Guo Fan, Li Yong-Dong, Wang Hong-Guang, Liu Chun-Liang, Hu Yi-Xiang, Zhang Peng-Fei e Ma Meng. "Particle-in-cell simulation of outer magnetically insulated transmission line of Z-pinch accelerator". Acta Physica Sinica 60, n. 10 (2011): 102901. http://dx.doi.org/10.7498/aps.60.102901.

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48

AKAI, Mitsunobu, Takuya TSUJI, Tomohiro DEGAWA e Toshitsugu TANAKA. "M602 Development of DEM algorithm for GPU accelerator toward ultra-large-scale particle simulation". Proceedings of Conference of Kansai Branch 2015.90 (2015): 344. http://dx.doi.org/10.1299/jsmekansai.2015.90.344.

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49

Fabris, Andrea Lucca, Christopher V. Young, Marco Manente, Daniele Pavarin e Mark A. Cappelli. "Ion Velocimetry Measurements and Particle-In-Cell Simulation of a Cylindrical Cusped Plasma Accelerator". IEEE Transactions on Plasma Science 43, n. 1 (gennaio 2015): 54–63. http://dx.doi.org/10.1109/tps.2014.2321743.

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Zeng, Xian Qiang, Lan Jing, Ze En Yao e Yu Hui Guo. "A PSO-Based LQR Controller for Accelerator PWM Power Supply". Advanced Materials Research 490-495 (marzo 2012): 71–75. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.71.

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Abstract (sommario):

In this paper the method of Linear Quadratic Regulator (LQR) is employed for controlling accelerator PWM power supply, and improving its dynamic functioning. A method based on the Particle Swarm Optimization is proposed to optimize the weighting matrix Q and R. In order to control the dynamic behavior of the power supply, the fitness function of PSO is acquired considering the needs of the power properties. The results of simulation proved that the proposed method was much better than simple LQR method and LQR-GA method, and the performance of the power supply was improved dramatically.

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