IPAC2013 - List of Authors (Paret, S.)

Paper	Title	Page
MOPWO062	A Parallel Multi-objective Differential Evolution Algorithm for Photoinjector Beam Dynamics Optimization	1031
	J. Qiang, C.E. Mitchell, S. Paret, R.D. Ryne LBNL, Berkeley, California, USA Y.X. Chao UCB, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 In photoinjector design, there is growing interest in using multi-objective beam dynamics optimization to minimize the final transverse emittances and to maximize the final peak current of the beam. Most previous studies in this area were based on genetic algorithms. Recent progress in optimization suggests that the differential evolution algorithm could perform better in comparison to the genetic algorithm. In this paper, we propose a new parallel multi-objective optimizer based on the differential evolution algorithm for photoinjector beam dynamics optimization. We will discuss the numerical algorithm and some benchmark examples. This algorithm has the potential to significantly reduce the computation time required to reach the optimal Pareto solution.

TUPME059	Collisional Effects in Particle-in-Cell Beam-Beam Simulations	1700
	S. Paret, J. Qiang LBNL, Berkeley, California, USA
	Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231. Self-consistent particle tracking simulations (strong-strong) can be used to investigate the deterioration of colliding beams in a storage ring. However, the use of a small number of macroparticles copmared to the real number of particles magnifies the collisional effects and causes numerical noise. In particular, predictions of the emittance lifetime suffer from this numerical noise. In order to produce usable emittance predictions, the contribution of numerical noise to the simulated emittance growth has to be known. In this paper, we apply a diffusion model to strong-strong beam-beam simulations to study the numerical noise driven emittance growth. The scaling of emittance growth with numerical and physical parameters is discussed.

TUPME060	Tune Studies with Beam-Beam Effects in LHC	1703
	S. Paret, J. Qiang LBNL, Berkeley, California, USA R. Alemany-Fernandez, X. Buffat, R. Calaga, K. Cornelis, M. Fitterer, R. Giachino, W. Herr, A. Macpherson, G. Papotti, T. Pieloni, S. Redaelli, F. Roncarolo, M. Schaumann, R. Suykerbuyk, G. Trad CERN, Geneva, Switzerland R. Miyamoto ESS, Lund, Sweden
	Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231. In high brightness colliders, the tune spread due to the collisions has a significant impact on the quality of the beams. The impact of the working point on emittance growth and beam lifetime has been observed in beam experiments in LHC. Strong-strong beam-beam simulations that were accomplished to better understand such observations are shown. Compared to experiments, wide ranged parameter scans can be done easily. Tune footprints and scans of the emittance growth obtained from simulations are discussed. Three cases are considered: Very high intensity, moderate intensity and collisions with separated beams.

TUPME061	Emittance Growth with Crab Cavity and Damper Noise in LHC	1706
	S. Paret, J. Qiang LBNL, Berkeley, California, USA
	Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231. Strong-strong beam-beam simulations are employed to investigate the noise sensitivity of the emittance in the future High Luminosity (HL)-LHC. Noise in the accelerator causes fluctuations of the bunch centroids at the interaction points (IPs) which cause emittance growth for large beam-beam parameters. Two noise sources are examined: Crab cavities and the transverse damper. The damper noise is adjusted to bring simulations in agreement with an emittance measurement in a past LHC run. Results from simulations with HL-LHC beam parameters using different noise levels, damper gains and working points are discussed.

Paper

Title

Page

A Parallel Multi-objective Differential Evolution Algorithm for Photoinjector Beam Dynamics Optimization

1031

J. Qiang, C.E. Mitchell, S. Paret, R.D. Ryne
LBNL, Berkeley, California, USA
Y.X. Chao
UCB, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
In photoinjector design, there is growing interest in using multi-objective beam dynamics optimization to minimize the final transverse emittances and to maximize the final peak current of the beam. Most previous studies in this area were based on genetic algorithms. Recent progress in optimization suggests that the differential evolution algorithm could perform better in comparison to the genetic algorithm. In this paper, we propose a new parallel multi-objective optimizer based on the differential evolution algorithm for photoinjector beam dynamics optimization. We will discuss the numerical algorithm and some benchmark examples. This algorithm has the potential to significantly reduce the computation time required to reach the optimal Pareto solution.

TUPME059

Collisional Effects in Particle-in-Cell Beam-Beam Simulations

1700

S. Paret, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231.
Self-consistent particle tracking simulations (strong-strong) can be used to investigate the deterioration of colliding beams in a storage ring. However, the use of a small number of macroparticles copmared to the real number of particles magnifies the collisional effects and causes numerical noise. In particular, predictions of the emittance lifetime suffer from this numerical noise. In order to produce usable emittance predictions, the contribution of numerical noise to the simulated emittance growth has to be known. In this paper, we apply a diffusion model to strong-strong beam-beam simulations to study the numerical noise driven emittance growth. The scaling of emittance growth with numerical and physical parameters is discussed.

TUPME060

Tune Studies with Beam-Beam Effects in LHC

1703

S. Paret, J. Qiang
LBNL, Berkeley, California, USA
R. Alemany-Fernandez, X. Buffat, R. Calaga, K. Cornelis, M. Fitterer, R. Giachino, W. Herr, A. Macpherson, G. Papotti, T. Pieloni, S. Redaelli, F. Roncarolo, M. Schaumann, R. Suykerbuyk, G. Trad
CERN, Geneva, Switzerland
R. Miyamoto
ESS, Lund, Sweden

Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231.
In high brightness colliders, the tune spread due to the collisions has a significant impact on the quality of the beams. The impact of the working point on emittance growth and beam lifetime has been observed in beam experiments in LHC. Strong-strong beam-beam simulations that were accomplished to better understand such observations are shown. Compared to experiments, wide ranged parameter scans can be done easily. Tune footprints and scans of the emittance growth obtained from simulations are discussed. Three cases are considered: Very high intensity, moderate intensity and collisions with separated beams.

TUPME061

Emittance Growth with Crab Cavity and Damper Noise in LHC

1706

S. Paret, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231.
Strong-strong beam-beam simulations are employed to investigate the noise sensitivity of the emittance in the future High Luminosity (HL)-LHC. Noise in the accelerator causes fluctuations of the bunch centroids at the interaction points (IPs) which cause emittance growth for large beam-beam parameters. Two noise sources are examined: Crab cavities and the transverse damper. The damper noise is adjusted to bring simulations in agreement with an emittance measurement in a past LHC run. Results from simulations with HL-LHC beam parameters using different noise levels, damper gains and working points are discussed.