Ion Motion Induced Emittance Growth of Matched Electron Beams in Plasma Wakefields

Weiming An; Wei Lu; Chengkun Huang; Xinlu Xu; Mark J Hogan; Chan Joshi; Warren B Mori

doi:10.1103/PhysRevLett.118.244801

Ion Motion Induced Emittance Growth of Matched Electron Beams in Plasma Wakefields

Phys Rev Lett. 2017 Jun 16;118(24):244801. doi: 10.1103/PhysRevLett.118.244801. Epub 2017 Jun 14.

Authors

Weiming An^{1

2}, Wei Lu^{3

4}, Chengkun Huang⁵, Xinlu Xu^{1

2}, Mark J Hogan⁶, Chan Joshi¹, Warren B Mori^{1

2}

Affiliations

¹ Department of Electrical Engineering, University of California Los Angeles, Los Angeles, California 90095, USA.
² Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
³ Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
⁴ IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China.
⁵ Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
⁶ SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

PMID: 28665672
DOI: 10.1103/PhysRevLett.118.244801

Abstract

Plasma-based acceleration is being considered as the basis for building a future linear collider. Nonlinear plasma wakefields have ideal properties for accelerating and focusing electron beams. Preservation of the emittance of nano-Coulomb beams with nanometer scale matched spot sizes in these wakefields remains a critical issue due to ion motion caused by their large space charge forces. We use fully resolved quasistatic particle-in-cell simulations of electron beams in hydrogen and lithium plasmas, including when the accelerated beam has different emittances in the two transverse planes. The projected emittance initially grows and rapidly saturates with a maximum emittance growth of less than 80% in hydrogen and 20% in lithium. The use of overfocused beams is found to dramatically reduce the emittance growth. The underlying physics that leads to the lower than expected emittance growth is elucidated.