Amplification due to two-stream instability of self-electric and magnetic fields of an ion beam propagating in background plasma

Abstract

Propagation of charged particle beams in background plasma as a method of space charge neutralization has been shown to achieve a high degree of charge and current neutralization and therefore enables nearly ballistic propagation and focusing of charged particle beams. Correspondingly, use of plasmas for propagation of charged particle beams has important applications for transport and focusing of intense particle beams in inertial fusion and high energy density laboratory plasma physics. However, the streaming of beam ions through a background plasma can lead to development of the two-stream instability between the beam ions and the plasma electrons. The beam electric and magnetic fields enhanced by the two-stream instability can lead to defocusing of the ion beam. Using particle-in-cell (PIC) simulations, we study the scaling of the instability-driven self-electromagnetic fields and consequent defocusing forces with the background plasma density and beam ion mass. We identify plasma parameters where the defocusing forces can be reduced.

Generation of forerunner electron beam during interaction of ion beam pulse with plasma

“…We focus on nonlinear stages of instability 200 ns after injection into a plasma, when we initialize time t = 0 presented in all figures. At t ≤ 0 ns, the potential mod- [30]. The potential in the plasma wave becomes very asymmetric and reaches about 1.6 kV at maximum at t = 8 ns.…”

“…Note that a significant amount of electrons is accelerated and the position of the maximum of the VDF is shifted toward the negative velocity, so that the total current is maintained, i.e., the current of the ion beam pulse is fully neutralized by the plasma electrons in 1D case. This may be different in a multidimensional setup if the beam radius is small compared to the skin depth, because the elec- tron acceleration can occur along the beam axis and the return current may occur outside the beam [30].…”

“…The ion beam propagates distance v b /τ B,i during the time τ B,i . Therefore, the strong defocusing forces caused by the two stream instability [19,30] can affect the ballistic beam propagation in plasmas only on distances shorter than v b /τ B,i .…”

The self-focusing condition of a charged particle beam in a resistive plasma

“…Transport of a charged particle beam in a background plasma is the foundation for a variety of applications, such as inertial confinement fusion (Roth et al 2001;Logan, Perkins & Barnard 2008;Frolova, Khishchenko & Charakhch'yan 2019), high-energy particle accelerators and colliders (Govil et al 1999), radiography (Sheng et al 2014), astrophysics (Bennett 1934;Alfvén 1939;Spitkovsky 2007) and material etching (Lami et al 2020). Within the transport, the beam can strongly interact with background plasmas, potentially causing many physical phenomena, commonly including exciting periodic plasma wake-fields (Adli et al 2018;Caldwell et al 2018;Martinez de la Ossa, Mehrling & Osterhoff 2018;Turner et al 2019) and beam-plasma instabilities (Lee & Lampe 1973; Davidson et al 2004;Tokluoglu et al 2018). In addition, beam focusing may also be induced under some circumstances, which has aroused our great interest.…”

Stability of different plasma sheaths near a dielectric wall with secondary electron emission

“…In the plasma bulk region, the ion streaming instability was predicted in many plasma environments, e.g. magnetized dusty plasmas (Rosenberg & Shukla 2004;Shukla et al 2008), auroral-acceleration-zone plasmas (Muschietti & Roth 2008), complex plasmas with non-Maxwellian ions (Kählert 2015;Quest, Rosenberg & Kercher 2017), negative ion source plasmas (Barminova & Chikhachev 2016;Kumar & Mathew 2017), electron-positron-ion plasmas (Saleem & Khan 2005) and ion beam propagation in inertial fusion plasmas (Tokluoglu et al 2018). In the plasma presheath region (i.e.…”