IPAC2015 - List of Authors (Yu, K.)

Paper	Title	Page
MOPWA003	Optimal Generalized Finite Difference Solution to the Particle-in-Cell Problem	77
	X. Wang, X. Jiao, H. Liu, V. Samulyak, K. Yu SBU, Stony Brook, USA V. Samulyak BNL, Upton, Long Island, New York, USA
	The particle-in-cell (PIC) method is widely used in applications, such as in electromagnetics, but the accuracy of its solutions degrades when the particle distribution is highly non-uniform. In our work, we propose an adaptive PIC method with optimal point distribution and a generalized finite difference (GFD) scheme. Our method replaces the Cartesian grid in the classical PIC with adaptive computational nodes or particles, to which the charges from the sample particles are assigned by a weighted least-square approximations. The partial differential equation is then discretized using a GFD method and solved with fast linear solvers. The density of computational particles is chosen adaptively, so that the error from GFD and that from Monte Carlo integration are balanced and the total error is approximately minimized. We also present the verification results using electrostatic problems and comparison of accuracy and solution time of our method with the classical PIC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA003
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MOPMN012	SPACE Code for Beam-Plasma Interaction	728
	K. Yu, V. Samulyak SBU, Stony Brook, USA V. Samulyak BNL, Upton, Long Island, New York, USA
	A parallel particle-in-cell code SPACE has been developed for the simulation of electromagnetic fields, relativistic particle beams, and plasmas. The algorithms include atomic processes in the plasma, proper boundary conditions, an efficient method for highly-relativistic beams in non-relativistic plasma, support for simulations in relativistic moving frames, and special data transfer algorithm from the moving to the laboratory frame that collects particles and fields in the lab frame without time shift due to the Lorentz transform, enabling data analysis and visualization. Plasma chemistry algorithms implement atomic physics processes such as the generation and evolution of plasma, recombination of plasma, and electron attachment on dopants in dense neutral gas. Benchmarks and experimental validation tests are also discussed. The code has been used for the simulation of processes relevant to the eRHIC program at BNL and the high pressure RF cavity (HPRF) program at Fermilab.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN012
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MOPMN013	Simulation of Beam-Induced Plasma in Gas Filled Cavities	731
	K. Yu, V. Samulyak SBU, Stony Brook, USA M. Chung UNIST, Ulsan, Republic of Korea B.T. Freemire IIT, Chicago, Illinois, USA V. Samulyak BNL, Upton, Long Island, New York, USA A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA
	Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN013
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MOPMN015	Simulation of Beam-Induced Plasma for the Mitigation of Beam-Beam Effects	734
	J. Ma, V. Samulyak, K. Yu SBU, Stony Brook, USA V. Litvinenko, V. Samulyak, G. Wang BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA V. Samulyak SUNY SB, Stony Brook, New York, USA
	One of the main challenges in the increase of luminosity of circular colliders is the control of the beam-beam effect. In the process of exploring beam-beam mitigation methods using plasma, we evaluated the possibility of plasma generation via ionization of neutral gas by proton beams, and performed highly resolved simulations of the beam-plasma interaction using SPACE, a 3D electromagnetic particle-in-cell code. The process of plasma generation is modelled using experimentally measured cross-section coefficients and a plasma recombination model that takes into account the presence of neutral gas and beam-induced electromagnetic fields. Numerically simulated plasma oscillations are consistent with theoretical analysis. In the beam-plasma interaction process, high-density neutral gas reduces the mean free path of plasma electrons and their acceleration. A numerical model for the drift speed as a limit of plasma electron velocity was developed. Simulations demonstrate a significant reduction of the beam electric field in the presence of plasma. Preliminary simulations using fully-ionized plasma have also been performed and compared with the case of beam-induced plasma.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN015
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Paper

Title

Page

Optimal Generalized Finite Difference Solution to the Particle-in-Cell Problem

77

X. Wang, X. Jiao, H. Liu, V. Samulyak, K. Yu
SBU, Stony Brook, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA

The particle-in-cell (PIC) method is widely used in applications, such as in electromagnetics, but the accuracy of its solutions degrades when the particle distribution is highly non-uniform. In our work, we propose an adaptive PIC method with optimal point distribution and a generalized finite difference (GFD) scheme. Our method replaces the Cartesian grid in the classical PIC with adaptive computational nodes or particles, to which the charges from the sample particles are assigned by a weighted least-square approximations. The partial differential equation is then discretized using a GFD method and solved with fast linear solvers. The density of computational particles is chosen adaptively, so that the error from GFD and that from Monte Carlo integration are balanced and the total error is approximately minimized. We also present the verification results using electrostatic problems and comparison of accuracy and solution time of our method with the classical PIC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA003

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMN012

SPACE Code for Beam-Plasma Interaction

728

K. Yu, V. Samulyak
SBU, Stony Brook, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA

A parallel particle-in-cell code SPACE has been developed for the simulation of electromagnetic fields, relativistic particle beams, and plasmas. The algorithms include atomic processes in the plasma, proper boundary conditions, an efficient method for highly-relativistic beams in non-relativistic plasma, support for simulations in relativistic moving frames, and special data transfer algorithm from the moving to the laboratory frame that collects particles and fields in the lab frame without time shift due to the Lorentz transform, enabling data analysis and visualization. Plasma chemistry algorithms implement atomic physics processes such as the generation and evolution of plasma, recombination of plasma, and electron attachment on dopants in dense neutral gas. Benchmarks and experimental validation tests are also discussed. The code has been used for the simulation of processes relevant to the eRHIC program at BNL and the high pressure RF cavity (HPRF) program at Fermilab.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN012

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMN013

Simulation of Beam-Induced Plasma in Gas Filled Cavities

731

K. Yu, V. Samulyak
SBU, Stony Brook, USA
M. Chung
UNIST, Ulsan, Republic of Korea
B.T. Freemire
IIT, Chicago, Illinois, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA
A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA

Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN013

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMN015

Simulation of Beam-Induced Plasma for the Mitigation of Beam-Beam Effects

734

J. Ma, V. Samulyak, K. Yu
SBU, Stony Brook, USA
V. Litvinenko, V. Samulyak, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
V. Samulyak
SUNY SB, Stony Brook, New York, USA

One of the main challenges in the increase of luminosity of circular colliders is the control of the beam-beam effect. In the process of exploring beam-beam mitigation methods using plasma, we evaluated the possibility of plasma generation via ionization of neutral gas by proton beams, and performed highly resolved simulations of the beam-plasma interaction using SPACE, a 3D electromagnetic particle-in-cell code. The process of plasma generation is modelled using experimentally measured cross-section coefficients and a plasma recombination model that takes into account the presence of neutral gas and beam-induced electromagnetic fields. Numerically simulated plasma oscillations are consistent with theoretical analysis. In the beam-plasma interaction process, high-density neutral gas reduces the mean free path of plasma electrons and their acceleration. A numerical model for the drift speed as a limit of plasma electron velocity was developed. Simulations demonstrate a significant reduction of the beam electric field in the presence of plasma. Preliminary simulations using fully-ionized plasma have also been performed and compared with the case of beam-induced plasma.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN015

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)