title: Physical Mechanism of the Transverse Instability in Radiation Pressure Ion Acceleration.
abstract: The transverse stability of the target is crucial for obtaining high quality ion beams using the laser radiation pressure acceleration (RPA) mechanism. In this Letter, a theoretical model and supporting two-dimensional (2D) particle-in-cell (PIC) simulations are presented to clarify the physical mechanism of the transverse instability observed in the RPA process. It is shown that the density ripples of the target foil are mainly induced by the coupling between the transverse oscillating electrons and the quasistatic ions, a mechanism similar to the oscillating two stream instability in the inertial confinement fusion research. The predictions of the mode structure and the growth rates from the theory agree well with the results obtained from the PIC simulations in various regimes, indicating the model contains the essence of the underlying physics of the transverse breakup of the target.
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.|Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China.|IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Wan
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: C-H
authors.initials: CH
authors.lastname: Pai
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: C J
authors.initials: CJ
authors.lastname: Zhang
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Y P
authors.initials: YP
authors.lastname: Wu
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: J F
authors.initials: JF
authors.lastname: Hua
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.|IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: W
authors.initials: W
authors.lastname: Lu
authors.affiliation: Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China.
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Gu
authors.affiliation: GoLP/instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal.
authors.forename: L O
authors.initials: LO
authors.lastname: Silva
authors.affiliation: University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: C
authors.initials: C
authors.lastname: Joshi
authors.affiliation: University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: W B
authors.initials: WB
authors.lastname: Mori