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Computer simulation of residual gas ionization in gas-filled neutron tubes

Vladimir Rashchikov
Deuteron beam acceleration in ion-optic system of gas-filled neutron tubes was investigated. Particle in cell (PIC) code SUMA [Rashchikov, 1990] [Didenko, Rashchikov and Fortov, 2011] used for computer simulation of ionization and knock on processes and there influence on deuteron beam parameters. When deuteron and ionized particles space charge self-field forces become the same order of magnitude as external
one, virtual cathode may occurs. It happens because of injected from ion source deuterons cannot overcome their own space charge potential wall and move in transverse direction. However, electrons, produced
by ionization, are trapped within the deuteron beam space charge potential wall and decrease it significantly. Thus, space charge neutralization of deuteron beams by electrons, may considerably increase target current and, as a result, output neutron flow. Moreover,
own longitudinal electric field rise near the target leads to reduction of accelerating electrode target potential wall, which was made to prevent knock on emission from the target. As a result, additional knocked on
electrons may appear in the region and should be taken into account. The data obtained were compared with experimental results.
CYBERNETICS AND PHYSICS, VOL. 3, No. 2, 2014, 73-78.
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