Paper  Title  Page 

MOPWO062  A Parallel Multiobjective Differential Evolution Algorithm for Photoinjector Beam Dynamics Optimization  1031 


Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC0205CH11231 In photoinjector design, there is growing interest in using multiobjective 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 multiobjective 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 ParticleinCell BeamBeam Simulations  1700 


Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DEAC0205CH11231. Selfconsistent particle tracking simulations (strongstrong) 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 strongstrong beambeam 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 BeamBeam Effects in LHC  1703 


Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DEAC0205CH11231. 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. Strongstrong beambeam 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 


Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DEAC0205CH11231. Strongstrong beambeam 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 beambeam 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 HLLHC beam parameters using different noise levels, damper gains and working points are discussed. 
