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Updated: Jun 15, 2026

3D Depth Profile Reconstruction of Segregated Impurities Using Secondary Ion Mass Spectrometry
Published on: April 29, 2020
Enhanced surface production in H- ion sources by introducing a negatively biased secondary electrode
YoungHwa An1, BongKi Jung, Y S Hwang
1Department of Nuclear Engineering, Seoul National University, Seoul 151-742, Republic of Korea.
Abstract:
A transformer coupled plasma negative hydrogen ion source with an external rf antenna has been developed at SNU, which is capable of continuous operation with long lifetime. A positively biased plasma electrode (PE) has been successfully used for the optimization of H(-) extraction. With molybdenum-coated stainless steel PE, the enhancement of H(-) production at the electrode surface was observed at the bias voltage lower than the plasma potential. However, the low bias voltage is unfavorable to H(-) beam extraction since the negative ions are repelled. A second electrode is inserted in front of the PE to enhance H(-) production at the electrode surface without impeding beam extraction. By biasing the secondary electrode (SE) more negatively, H(-) production is clearly enhanced although the SE itself reduces H(-) beam currents because of suppressed electron transport in front of the PE. In this configuration enhancement of surface productions is most pronounced in tantalum electrode among various electrode materials.
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