Improved Computational Modeling of Electron Cooling in the Medium Energy Regime
It is a priority of the DOE Office of Nuclear Physics to build a next-generation polarized electron-ion collider capable of meeting the luminosity requirements of the experimental nuclear physics program. The electron cooler system for the proposed Medium Energy Electron-Ion Collider (MEIC) at Jefferson Lab represents a significant design challenge due to the high energy of the ion beam and electron beam bunch structure. Even a slightly less efficient cooling than predicted by simplified models may not be sufficient to combat emittance growth from intra-beam scattering and other effects, preventing the facility from reaching its target luminosity. Because it is not feasible to carry out direct experimental measurements in the energy regime targeted by MEIC, simulation plays a central role. Codes such as BETACOOL accurately model existing low-energy cooling systems. However, the new cooling system is designed for a previously unexplored parameter domain and therefore there is risk in deriving the MEIC design parameters on the basis of simplified models that have been developed and tested only for the low energy applications. To address the need for accurate modeling of electron cooling, we will pursue a hybrid, two-level approach. At the microscopic level, Vorpal simulations will be performed to accurately estimate the dynamical friction in a variety of dynamical regimes. At the macroscopic level, the dynamical friction information from Vorpal simulations will be coupled into BETACOOL, resulting in improved modeling of cooling on long timescales. During Phase I we will evaluate the feasibility of this approach. In addition, Vorpal will be used to prototype and test the utility of a novel binary collision algorithm that works with f PIC macroparticles and allows to accurately model the evolution of the electron beam at the same time as the dynamical friction forces acting on ions are obtained. The functionality of the Vorpal Composer will be extended to work with these new capabilities. The Phase II project will fully implement and optimize the algorithms for accurate modeling on macroscopic timescales of electron cooling and competing beam heating mechanisms. Commercial Applications and Other Benefits: Vorpal is a commercial software for simulation of a wide range of electromagnetic and electrostatic phenomena, including the nonlinear kinetic behavior of plasmas. Extending the range of Vorpals electron cooling modeling capabilities will create opportunities for Vorpal sales to, and associated contract revenue form, electron cooling groups in the U.S. and abroad. There will also be possibilities for future non-SBIR revenue in this area from U.S. labs or funding agencies. Successful completion of the proposed effort will produce commercial quality software for modeling electron cooling and other processes where binary Coulomb collisions play a key role, such as several types of plasma processing. There are many opportunities for commercial sales of our software in the plasma processing market.
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