Characterization of plasma ion source utilizing anode spot with positively biased electrode for stable and high-current ion beam extraction

Journal Article · Thu Dec 15 04:00:00 EST 2011 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3664616· OSTI ID:22062381

Park, Yeong-Shin; Lee, Yuna; Chung, Kyoung-Jae; Hwang, Y S ^[1]

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1. Department of Nuclear Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

The operating conditions of a rf plasma ion source utilizing a positively biased electrode have been investigated to develop a stably operating, high-current ion source. Ion beam characteristics such as currents and energies are measured and compared with bias currents by varying the bias voltages on the electrode immersed in the ambient rf plasma. Current-voltage curves of the bias electrode and photographs confirm that a small and dense plasma, so-called anode spot, is formed near an extraction aperture and plays a key role to enhance the performance of the plasma ion source. The ion beam currents from the anode spot are observed to be maximized at the optimum bias voltage near the knee of the characteristic current-voltage curve of the anode spot. Increased potential barrier to obstruct beam extraction is the reason for the reduction of the ion beam current in spite of the increased bias current indicating the density of the anode spot. The optimum bias voltage is measured to be lower at higher operating pressure, which is favorable for stable operation without severe sputtering damage on the electrode. The ion beam current can be further enhanced by increasing the power for the ambient plasma without increasing the bias voltage. In the same manner, noble gases with higher atomic number as a feedstock gas are preferable for extracting higher beam current more stably. Therefore, performance of the plasma ion source with a positively biased electrode can be enhanced by controlling the operating conditions of the anode spot in various manners.

• OSTI ID: 22062381
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 12 Vol. 82; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ANODES
BEAM CURRENTS
BEAM EXTRACTION
CURRENT DENSITY
DAMAGE
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
IMAGES
ION BEAMS
ION SOURCES
PLASMA
RARE GASES
RF SYSTEMS
SPUTTERING