arXiv subjects

Alexander Scheinker

Publications and source records attributed to Alexander Scheinker.

42 records · Page 3Linked to original sources

arXiv2020

Online Multi-Objective Particle Accelerator Optimization of the AWAKE Electron Beam Line for Simultaneous Emittance and Orbit Control

Multi-objective optimization is important for particle accelerators where various competing objectives must be satisfied routinely such as, for example, transverse emittance vs bunch length. We develop and demonstrate an online multi-time scale multi-objective optimization algorithm that performs real time feedback on particle accelerators. We demonstrate the ability to simultaneously minimize the emittance and maintain a reference trajectory of a beam in the electron beamline in CERN's Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE).

physics.acc-ph↗

arXiv2020

Advanced Control Methods for Particle Accelerators (ACM4PA) 2019 Workshop Report

Los Alamos is currently developing novel particle accelerator controls and diagnostics algorithms to enable higher quality beams with lower beam losses than is currently possible. The purpose of this workshop was to consider tuning and optimization challenges of a wide range of particle accelerators including linear proton accelerators such as the Los Alamos Neutron Science Center (LANSCE), rings such as the Advanced Photon Source (APS) synchrotron, free electron lasers (FEL) such as the Linac Coherent Light Source (LCLS) and LCLS-II, the European X-ray Free Electron Laser (EuXFEL), the Swiss FEL, and the planned MaRIE FEL, and plasma wake-field accelerators such as FACET, FACET-II, and AWAKE at CERN. One major challenge is an the ability to quickly create very high quality, extremely intense, custom current and energy profile beams while working with limited real time non-invasive diagnostics and utilizing time-varying uncertain initial beam distributions and accelerator components. Currently, a few individual accelerator labs have been developing and applying their own diagnostics tools and custom control and ML algorithms for automated machine tuning and optimization. The goal of this workshop was to bring together a group of accelerator physicists and accelerator related control and ML experts in order to define which controls and diagnostics would be most useful for existing and future accelerators and to create a plan for developing a new family of algorithms that can be shared and maintained by the community.

physics.acc-ph↗

arXiv2018

Phase space exchange-based bunch compression with reduced CSR effects

Through an interaction of theory and optimization-guided design, we have developed a novel bunch compression scheme based on an asymmetric double emittance exchange (DEEX) with greatly reduced coherent synchrotron radiation (CSR) effects. First, we discuss the benefits of the phase space exchange-based bunch compressor (BC) in comparison to the chicane-based counterpart in the approximation of linear single particle dynamics and with respect to microbunching instabilities driven by longitudinal space charge forces. We present simulation results for nonlinear dynamics in a symmetric DEEX BC which accounts for the CSR effects of the scheme with direct and mirrored longitudinal phase space at the exit of the beamline. The later scheme demonstrates self-compensation of CSR effects on the longitudinal dynamics. Next, we optimize the parameters of the beam elements with an adaptive feedback, resulting in an asymmetric configuration of the scheme with compensated CSR and nonlinear effects on the transverse dynamics, which we further improve by incorporating several sextupoles relying on an eigen-emittance analysis. Finally, we discuss how this method can be generalized for optimizing nonlinear beam dynamics with collective effects.

physics.acc-ph↗

arXiv2018

Extremum Seeking Optimal Controls of Unknown Systems

We present a method for finding optimal controllers for unknown, time-varying, dynamic systems which can be re-initialized from a given initial condition repeatedly, in which the performance measure is available for sampling with noise, but analytically unknown. Such systems are present throughout industry where processes must be repeated many times, such as a voltage source which is repeatedly turned on for a fraction of a second from zero initial conditions and then turned off again, whose output must track a specific trajectory, while the system's components are slowly drifting with time due to temperature variations. For systems with convex cost functions we prove that our algorithm will produce controllers that approach the minimal cost, e.g., the cost minimizing LQR optimal controller that could have been designed analytically had the system and objective function been known. We demonstrate the algorithm's effectiveness with simulation studies of noisy and time-varying systems.

math.OC↗

arXiv2016

Extremum Seeking for Stabilization of Systems Not Affine in Control

In [22] a form of extremum seeking for control (ESC) was developed for the stabilization of uncertain nonlinear systems. In ESC the extremum seeker itself controls the systems through feedback rather than fine tuning a controller. The ESC results, and other related results, apply only to systems affine in control. However, in most physical systems the control effort enters the system's dynamics through a nonlinear function, such as an input with deadline and saturation. In this work, we utilize our previous results on ESC to develop stabilizing controllers for systems of practical interest that are non-affine in control.

math.DS↗

arXiv2016

Suppression of Space Charge Induced Beam Halo in Nonlinear Focusing Channel

An intense non-uniform particle beam exhibits strong emittance growth and halo formation in focusing channels due to nonlinear space charge forces of the beam. This phenomenon limits beam brightness and results in particle losses. The problem is connected with irreversible distortion of phase space volume of the beam in conventional focusing structures due to filamentation in phase space. Emittance growth is accompanied by halo formation in real space, which results in inevitable particle losses. A new approach for solving a self-consistent problem for a matched non-uniform beam in two-dimensional geometry is discussed. The resulting solution is applied to the problem of beam transport, while avoiding emittance growth and halo formation by the use of nonlinear focusing field. Conservation of a beam distribution function is demonstrated analytically and by particle-in-cell simulation for a beam with a realistic beam distribution.

physics.acc-ph↗