@article{Lan2020b,

title = {Neutralization of ion beam by electron injection: Accumulation of cold electrons},

author = {C. Lan and I. D. Kaganovich},

url = {http://aip.scitation.org/doi/pdf/10.1063/1.5128521},

doi = {10.1063/1.5128521},

year  = {2020},

date = {2020-04-23},

journal = {Physics of Plasmas},

volume = {27},

number = {4},

abstract = {Ion beam charge neutralization by electron injection is a complex kinetic process. Recent experiments show that the resulting self-potential of the ion beam after neutralization by plasma is much lower than the temperature of plasma electrons [Stepanov et al., Phys. Plasmas 23, 043113 (2016)], indicating that kinetic effects are important and may affect the neutralization of the ion beam. We performed a numerical study of the charge neutralization process of an ion beam making use of a two-dimensional electrostatic particle-in-cell code. The results show that the process of charge neutralization by electron injection is composed of two stages. During the first stage, the self-potential of the beam is higher than the temperature of injected electrons (Te/e) and all injected electrons are captured by the ion beam. During the second stage, hot electrons escape from the ion beam and the beam self-potential (φ) decreases because cold electrons slowly accumulate resulting in the beam self-potential φ to become much lower than Te/e in agreement with previous experimental observations at Princeton Advanced Teststand. We also determined that the resulting φ scales as φ∼Te⎯⎯⎯⎯√, in agreement with previous experimental observations from Gabovich's group. In addition, the results show that the transverse position of the electron source has a great impact on ion beam neutralization. A slight shift of the electron source as relevant to the ion thrusters leads to a large increase in the beam self-potential because of an increase in potential energy of injected electrons.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lan2020,

title = {Neutralization of ion beam by electron injection: Excitation and propagation of electrostatic solitary waves},

author = {C. Lan and I. D. Kaganovich},

url = {https://aip.scitation.org/doi/pdf/10.1063/1.5128523},

doi = {10.1063/1.5128523},

year  = {2020},

date = {2020-04-10},

journal = {Physics of Plasmas},

volume = {27},

number = {4},

abstract = {The charge neutralization of an ion beam by electron injection is investigated using a two-dimensional electrostatic particle-in-cell code. The simulation results show that electrostatic solitary waves (ESWs) can be robustly generated in the neutralization process and last for a long time (for more than 30 μs) and therefore, ESWs can strongly affect the neutralization process. The ESWs propagate along the axis of the ion beam and reflect from the beam boundaries. The simulations clearly show that two ESWs can pass through each other with only small changes in amplitude. Partial exchange of trapped electrons in collisions of two ESWs is observed in the simulations and can explain interaction during collisions of two ESWs. Coalescence of two ESWs is also observed.

},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Galea2020,

title = {Coherent microwave scattering from xenon resonance-enhanced multiphoton ionization-initiated plasma in air},

author = {C. A. Galea and M. N. Shneider and M. Gragston and Z. Zhang},

url = {https://pcrf.princeton.edu/j-appl-phys-127-053301-2020/},

doi = {10.1063/1.5135316},

year  = {2020},

date = {2020-02-04},

journal = {Journal of Applied Physics},

volume = {127},

number = {5},

abstract = {Here we present the experimental and computational study of resonance-enhanced multiphoton ionization (REMPI) of xenon and subsequent avalanche ionization of air. Xenon was excited from the ground state to the excited 6p state (89162cm−1) by two photons at 224.3 nm. The third photon at 224.3 nm subsequently produced ionization of xenon in air. The seed electrons from the ionization served as the medium to further absorb the laser pulse for the rotational and vibrational excitation and avalanche ionization of O2 and N2. Plasma chemistry of O2 and N2 in air was included in the model. The results are useful for understanding REMPI-initiated plasma in air and possibly new diagnostics tools based on REMPI-initiated plasma emissions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}