Nearly monoenergetic positive ion beam with self-neutralized space charge extracted from a pulsed plasma
| Autor: | Siyuan Tian, Paul Ruchhoeft, Ya-Ming Chen, Demetre J. Economou, Vincent M. Donnelly, Ryan Sawadichai |
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| Rok vydání: | 2019 |
| Předmět: |
010302 applied physics
Materials science Acoustics and Ultrasonics Ion beam Faraday cup 02 engineering and technology Plasma Electron 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 7. Clean energy Space charge Surfaces Coatings and Films Electronic Optical and Magnetic Materials Ion symbols.namesake Physics::Plasma Physics 0103 physical sciences symbols Atomic physics 0210 nano-technology Beam (structure) DC bias |
| Zdroj: | Journal of Physics D: Applied Physics. 52:355205 |
| ISSN: | 1361-6463 0022-3727 |
| DOI: | 10.1088/1361-6463/ab294e |
| Popis: | A nearly monoenergetic Ar+ ion beam (100 eV peak energy, 3.5 eV full width at half maximum), with self-neutralized space charge, was extracted from a power modulated (pulsed) inductively coupled plasma (ICP), through a single grounded grid. The beam energy was set by applying a synchronous DC bias voltage to a boundary electrode in contact with the plasma, in the late afterglow of the power pulse. A retarding field energy analyzer and a movable Faraday cup were used to measure the ion energy distribution (IED) and the time resolved ion and electron current densities, as a function of position along the beam axis, to unravel the mechanism of self-neutralization of the space charge of the beam. When a +100 V DC bias was applied to the boundary electrode during the afterglow, a ~100 eV beam (ion density ~109 cm−3) emerged that was space-charge neutralized by periodic injection of electrons, mainly during the early afterglow, into the region downstream of the extraction grid. A background plasma (electron density ~1010 cm−3) was formed by these electrons, in conjunction with relatively low-energy ions (1–10 eV) that flew out of the ICP when the DC bias was off, as well as formed by resonant charge exchange of the 100 eV beam ions with the background Ar in the downstream region near the extraction grid. The behavior of the beam IED as a function of pressure and power of the ICP as well as the timing of application of the DC bias voltage was also studied. |
| Databáze: | OpenAIRE |
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