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Numerical simulation of a triode source of intense radial converging electron beam

### Abstract

The results of numerical simulations of a triode source of an intense radial converging electron beam are presented. The role of the initial transverse velocity of electrons, defocusing effect of the controlling grid, the beam self-magnetic field, backscattering of electrons, and ion flow from the target is analyzed. It was found that the ion flow from the target essentially increases the value of the electron current. The influence of the beam self-magnetic field on electron trajectories leads to the fact that there is a critical value of the cathode-grid voltage dividing the mode of the source operation into stable and unstable. The influence of initial transverse electron energies on the beam focusing is essentially higher than the influence of the controlling grid. Backscattering of the beam electrons from the target surface increases the target ion current so that the source operation may become unstable and the distribution of the beam power density on the target becomes nonuniform with a maximum in the center. Electrons passing by the target drift along the source axis. This leads to diminishing the power density at the center of the target and to the exit of peripheral electrons from the source. Conditions for achieving required electron beam parameters (the electron kinetic energy—120 keV, the beam energy density on the target ∼40 J/cm^{2} on a maximum possible length of the target surface) were determined.

Published by AIP Publishing.

Received 23 August 2016
Accepted 19 September 2016
Published online 11 October 2016

Article outline:

I. INTRODUCTION
II. SCHEME OF THE SOURCE
III. THE TECHNIQUE OF MODELING
IV. RESULTS
A. Zero initial transverse velocity of electrons
B. Nonzero initial velocity of electrons
C. Effect of backscattered electrons
D. Combined influence of backscattered electrons and nonzero initial transverse velocity of electrons
V. SUMMARY

/content/aip/journal/jap/120/14/10.1063/1.4964335

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V. Altsybeyev, A. Ovsyannikov, D. Ovsyannikov, and V. Engelko, “ Numerical simulations of the radial electron flow formation for the triode type source,” in 10th International Vacuum Electron Sources Conference, IVESC 2014 and 2nd International Conference on Emission Electronics, ICEE 2014 (2014).

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V. Altsybeyev and V. Ponomarev, “ Development of 2D Poisson equation C++ finite-difference solver for particle-in-cell method,” in 2015 International Conference on Stability and Control Processes in Memory of V. I. Zubov (SCP) (2015), pp. 195–197.

3.

V. Altsybeyev, V. Ponomarev, D. Ovsyannikov, A. Ovsyannikov, V. Engelko, and G. Mueller, “ Numerical simulations of the radial convergent electrons and ions flows for cylindrical pulsed source,” in 2015 International Conference on Stability and Control Processes in Memory of V. I. Zubov (SCP) (2015), pp. 138–141.

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V. V. Altsybeyev and V. A. Ponomarev, “ Application of Gauss's law space-charge limited emission model in iterative particle tracking method,” J. Comput. Phys. 324, 62–72 (2016).

http://dx.doi.org/10.1016/j.jcp.2016.08.007
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V. Engelko, V. Kuznetsov, G. Viazmenova, G. Mueller, and H. Bluhm, “ Influence of electrons reflected from a target on the operation of triode-type electron sources,” J. Appl. Phys. 88, 3879–3888 (2000).

http://dx.doi.org/10.1063/1.1290709
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V. I. Engelko, V. S. Kuznetsov, and G. Mueller, “ Electron source of triode type with radial converging electron flow for irradiation of cylindrical targets,” J. Appl. Phys. 105, 023305 (2009).

http://dx.doi.org/10.1063/1.2996286
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R. Hockney and J. Eastwood, Computer Simulation Using Particles ( Francis, 1988).

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V. Ilyin, Numerical Methods for Solution of Problems of Electrophysics ( Nauka, 1985).

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http://dx.doi.org/10.1063/1.1410891
http://aip.metastore.ingenta.com/content/aip/journal/jap/120/14/10.1063/1.4964335

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2016-10-11

2016-10-23

### Abstract

The results of numerical simulations of a triode source of an intense radial converging electron beam are presented. The role of the initial transverse velocity of electrons, defocusing effect of the controlling grid, the beam self-magnetic field, backscattering of electrons, and ion flow from the target is analyzed. It was found that the ion flow from the target essentially increases the value of the electron current. The influence of the beam self-magnetic field on electron trajectories leads to the fact that there is a critical value of the cathode-grid voltage dividing the mode of the source operation into stable and unstable. The influence of initial transverse electron energies on the beam focusing is essentially higher than the influence of the controlling grid. Backscattering of the beam electrons from the target surface increases the target ion current so that the source operation may become unstable and the distribution of the beam power density on the target becomes nonuniform with a maximum in the center. Electrons passing by the target drift along the source axis. This leads to diminishing the power density at the center of the target and to the exit of peripheral electrons from the source. Conditions for achieving required electron beam parameters (the electron kinetic energy—120 keV, the beam energy density on the target ∼40 J/cm^{2} on a maximum possible length of the target surface) were determined.

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