Enhanced negative hydrogen ion production in volume ion source

Authors

Yohannes Abate National Institute of Physics, University of the Philippines Diliman
Paul Conception National Institute of Physics, University of the Philippines Diliman
Rainier Awayan National Institute of Physics, University of the Philippines Diliman
Marko Arciaga National Institute of Physics, University of the Philippines Diliman
Mira Macandog National Institute of Physics, University of the Philippines Diliman
Laudemer Mejia National Institute of Physics, University of the Philippines Diliman
Virginia Noguera National Institute of Physics, University of the Philippines Diliman
Ma. Gracita Cardinal National Institute of Physics, University of the Philippines Diliman
Henry Ramos National Institute of Physics, University of the Philippines Diliman

Abstract

The production of negative hydrogen ions is of great interest in the context of fusion reactor heating and refueling and a considerable effort is underway to develop and optimize efficient ion sources. A number of different processes can generate H^- in the discharge, but it is generally accepted that the most important volume processes is the dissociative attachment to vibrationally excited hydrogen molecules: e + H₂ (𝜈*) → H (1s) + H⁻. The most important destruction mechanism is normally electron detachment, H⁻ + e → H + 2e, which has low threshold energy of 0.75 eV. Useful strategies for optimizing negative ion yield is reducing the electron temperature T_e in one part of the reactor by using magnetic filters, or by power modulation, or by adding heavier species. Adding noble gases is one possible way of reducing the temperature T_e.
A modified sheet plasma ion source using steel is used in this study. Negative hydrogen ions in a weakly magnetized plasma (~50 G) are volume produced by low energy electrons (~0.67 eV) through detaching vibrationally excited hydrogen molecules near the plasma electrode. Sheet plasma with a thickness of several millimeters was produced by a combination of a pair of dipole magnetic fields and a mirror magnetic field. A ferrite magnet and a coreless magnetic coil encased in the limiters add to the mirror field enhancing quiescence in the plasma. The negative hydrogen ions produced in the peripheral region of the sheet plasma was measured with a 180° deflection mass analyzer, which we have constructed anew.
In the present work, experiments have been carried out to investigate the effect of adding noble gases to the discharge.

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Issue

1999: Proceedings of the 17th National Physics Congress of the Samahang Pisika ng Pilipinas

Article ID

SPP-1999-SP-01

Section

Spectroscopy and Interferometry

Published

1999-10-22

How to Cite

[1]

Y Abate, P Conception, R Awayan, M Arciaga, M Macandog, L Mejia, V Noguera, MG Cardinal, and H Ramos, Enhanced negative hydrogen ion production in volume ion source, Proceedings of the Samahang Pisika ng Pilipinas 17, SPP-1999-SP-01 (1999). URL: https://proceedings.spp-online.org/article/view/SPP-1999-SP-01.