1. Dynamics of ion beam charge neutralization by ferroelectric plasma sources.
- Author
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Stepanov, Anton D., Gilson, Erik P., Grisham, Larry R., Kaganovich, Igor D., and Davidson, Ronald C.
- Subjects
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ION beams , *NEUTRALIZATION (Chemistry) , *FERROELECTRIC crystals , *PLASMA sources , *SPACE charge , *ELECTRIC potential - Abstract
Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Arþ beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established ~5 µs after the driving pulse is applied to the FEPS and can last for 35 µs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-µs surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of µs after the high voltage pulse is applied. It is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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