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SAPAF03 | Comparison of Model-Based and Heuristic Optimization Algorithms Applied to Photoinjectors Using Libensemble | simulation, cavity, space-charge, solenoid | 22 |
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Funding: U.S. DOE, OS, contract DE-AC02-06CH11357 and grant DE-SC0015479. Genetic algorithms are common and often used in the accelerator community. They require large amounts of computational resources and empirical adjustment of hyperparameters. Model based methods are significantly more efficient, but often labeled as unreliable for the nonlinear or unsmooth problems that can be found in accelerator physics. We investigate the behavior of both approaches using a photoinjector operated in the space charge dominated regime. All optimization runs are coordinated and managed by the Python library libEnsemble, which is developed at Argonne National Laboratory. |
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Slides SAPAF03 [0.653 MB] | |||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF03 | ||
About • | paper received ※ 11 November 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019 | ||
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TUPAF19 | pyaopt Optimization Suite and its Applications to an SRF Cavity Design for UEMs | SRF, simulation, cavity, electron | 229 |
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Funding: DOE SBIR In order to achieve sharp, high resolution real-time imaging, electrons in a MeV UEM (ultrafast electron microscope) beamline need to minimize instabilities. The Superconducting RF (SRF) photocathode gun is a promising candidate to produce highly stable electrons for UEM/UED applications. It operates in an ultrahigh Q, CW mode, and dissipates a few watts of RF power, which make it possible to achieve a 10s ppm level of beam stability by using modern RF control techniques. In order to find the best performance of the gun design, an optimization procedure is required. pyaopt is a Python-based optimization suite that supports multi-objective optimizations using advanced algorithms. In this paper, the novel SRF photogun design and its optimizations through pyaopt and Astra’s beam simulations will be discussed. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF19 | ||
About • | paper received ※ 22 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019 | ||
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TUPAG13 | S-Based Macro-Particle Spectral Algorithm for an Electron Gun | electron, cathode, solenoid, simulation | 290 |
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We derive a Hamiltonian description of a continuous particle distribution and its electrostatic potential from the Low Lagrangian. The self consistent space charge potential is discretized according to the spectral Galerkin approximation. The particle distribution is discretized using macro-particles. We choose a set of initial and boundary conditions to model the TRIUMF 300keV thermionic DC electron gun. The field modes and macro-particle coordinates are integrated self-consistently. The current status of the implementation is discussed. | |||
Slides TUPAG13 [1.335 MB] | |||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG13 | ||
About • | paper received ※ 01 November 2018 paper accepted ※ 10 December 2018 issue date ※ 26 January 2019 | ||
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WEPAF02 | Simulations of Beam Chopping for Potential Upgrades of the SNS LEBT Chopper | rfq, simulation, LEBT, operation | 325 |
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Funding: This work was performed at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract number DE-AC05-00OR22725 for the United States Department of Energy. The LEBT chopper is a critical element of the SNS accelerator system. In this work, the benefit of increasing the chopping voltage amplitude for the present chopping pattern is shown with beam simulations, and an ongoing hardware upgrade of the chopper pulser units is discussed. In addition, with the prospect of higher voltage capability of the new pulser design, two alternative chopping patterns which reduce the switching frequency of the chopper pulsers down to 1/2 or 1/4 of the present chopping pattern, are also explored with beam simulations. |
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Slides WEPAF02 [7.431 MB] | |||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPAF02 | ||
About • | paper received ※ 31 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019 | ||
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