Paper  Title  Page 

MOEPPB007  Studies of eRHIC Coherent Instabilities  91 


Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DEAC0298CH10886 with the U.S. Department of Energy. In the presence of an effective coherent electron cooling, the rms ion bunch length in eRHIC will be kept at 8.4cm, which is about a factor of 3 shorter than the current RHIC rms bunch length. Together with a factor of 2 increase in bunch intensity, coherent instabilities could be a potential limitation for achieving desired machine performance. In this study, we use the tracking code TRANFT to find thresholds and growth rates for various single bunch and coupled bunch instabilities with linear chromaticity and amplitude dependent tune shift taken into account. Based on the simulation results, requirements of machine parameters such as rf voltage, linear chromaticity, and octupole strength are specified to avoid these instabilities. 

MOPPC025  RHIC Polarized Proton Operation in Run 12  184 


Successful RHIC operation with polarized protons requires meeting demanding and sometimes competing goals for maximizing both luminosity and beam polarization. In Run 12 we sought to fully integrate into operation the many systems that were newly commissioned in Run 11 as well as to enhance collider performance with incremental improvements throughout the acceleration cycle. For luminosity maximization special attention was paid to several possible source of emittance dilution along the injector chain, in particular to optical matching during transfer between accelerators. Possible sources of depolarization in the AGS and RHIC were also investigated including the effects of local coupling and low frequency (10 Hz) oscillations in the vertical equilibrium orbit during the RHIC ramp. The results of a fine storage energy scan made in an effort to improve store polarization lifetime are also reported in this note.  
MOPPC090  Coupling Modulator Simulations into an FEL Amplifier for Coherent Electron Cooling  346 


Funding: Work supported by the US DOE Office of Science, Office of Nuclear Physics under grant numbers DEFG0208ER85182 and DESC0000835. Nextgeneration ion colliders will require effective cooling of highenergy hadron beams. Coherent electron cooling (CeC) can in principle cool relativistic hadron beams on ordersofmagnitude shorter time scales than other techniques*. Particleincell (PIC) simulations of a CeC modulator with the parallel VORPAL framework generate macroparticle distributions with subtle but important phase space correlations. To couple these macroparticles into a 3D simulation code for the freeelectron laser (FEL) amplifier, while retaining all details of the 6D phase space coordinates, we implemented an alternative approach based on particleclone pairs**. Our approach allows for selfconsistent treatment of shot noise and spontaneous radiation, with no need for quietstart initialization of the FEL macroparticles' ponderomotive phase. We present results of comparing fully 3D amplifier modeling based on the particleclone approach vs GENESIS simulations where distribution of bunching parameter was used as input. We also discuss enabling direct coupling of the VORPAL deltaf simulation output into 3D distributions of particleclone pairs. * V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009). ** V.N. Litvinenko, "Macroparticle FEL model with selfconsistent spontaneous radiation," unpublished (2002). 

MOPPD016  Status of Proofofprinciple Experiment for Coherent Electron Cooling  400 


Funding: US DOE Office of Science, DEFC0207ER41499, DEFG0208ER85182; NERSC DOE contract No. DEAC0205CH11231. Coherent electron cooling (CEC) has a potential to significantly boost luminosity of highenergy, highintensity hadron colliders. To verify the concept we conduct proofoftheprinciple experiment at RHIC. In this paper, we describe the current experimental setup to be installed into 2 o’clock RHIC interaction regions. We present current design, status of equipment acquisition and estimates for the expected beam parameters. 

TUPPP093  General Results on the Nature of FEL Amplification  1804 


Freeelectron lasers are increasingly important tools for the material and biological sciences, and although numerical and analytical theory is extensive, a fundamental question about the nature of the FEL growing modes has remained unanswered. In this proceeding, we present results of a topological nature concerning the number of amplifying solutions to the 1dimensional FEL equations as related to the energy distribution of the electron bunches.  
WEPPR099  Shielding of a Hadron in a Finite eBeam  3171 


Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DEAC0298CH10886 with the U.S. Department of Energy. The thorough study of coherent electron cooling, the modern cooling technique capable to deal with accelerators operating in the range of few TeVs*, rises many interesting questions. One of them is a shielding dynamics of a hadron in an electron beam. Now this effect is computed analytically in an infinite beam approximation**. Many effects are drastically different in finite and infinite plasmas. Here we propose a method to compute the dynamical shielding effect in a finite cylindrical plasma  the realistic model of an electron beam in accelerators. * V. N. Litvinenko, Y. S. Derbenev, Phys. Rev. Lett. 10^{2}, 114801 (2009). ** G. Wang, M. Blaskiewicz, Phys. Rev. E 78, 026413 (2008). 

THYB02  Influence of Electron Beam Parameters on Coherent Electron Cooling  3213 


Coherent electron cooling (CeC) is promising to revolutionize the cooling of high energy hadron beams. The intricate dynamics of the CeC depends both on the local density and energy distribution of the beam. This talk should present a rigorous analytical model of the 3D processes (including diffraction) in the modulator and the FEL and describe how the theory is applied to electron beams with inhomogeneous longitudinal density and energy distributions in the process of CeC. The SPC would like you to describe the influence of electron beam energy and current variations along the bunch length.  
Slides THYB02 [0.878 MB]  
THEPPB002  HighFidelity 3D Modulator Simulations of Coherent Electron Cooling Systems  3231 


Funding: This work is supported by the US DOE Office of Science, Office of Nuclear Physics, grant numbers DESC0000835 and DEFC0207ER41499. Resources of NERSC were used under contract No. DEAC0205CH11231. Next generation electronhadron colliders will require effective cooling of highenergy, highintensity hadron beams. Coherent electron cooling (CeC) can in principle cool relativistic hadron beams on ordersofmagnitude shorter time scales than other techniques*. The parallel VORPAL framework is used for 3D deltaf PIC simulations of anisotropic Debye shielding in a full longitudinal slice of the copropagating electron beam, choosing parameters relevant to the proofofprinciple experiment under development at BNL. The transverse density conforms to an exponential Vlasov equilibrium for Gaussian velocities, with no longitudinal density variation. Comparison with 1D1V Vlasov/Poisson simulations shows good agreement in 1D. Parallel 3D simulations at NERSC show 3D effects for ions moving longitudinally and transversely. Simulation results are compared with the constantdensity theory of Wang and Blaskiewicz**. * V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 10^{2}, 114801 (2009). ** Wang and Blaskiewicz, Phys Rev E 78, 026413 (2008). 
