Speaker
Takuya Hase
(Tokai University)
Description
Production of negative ions plays an essential role in Neutral Beam Injection (NBI). A negative ion beam with an energy of 1 MeV and a current of 40 A (a current density of 20 mA/cm22) is required for 3600 s to produce 16.5 MW of power. NBI predominantly uses negative hydrogen ion sources based on surface production. These negative hydrogen ion sources require cesium seeding to achieve a high ion density. However, cesium seeded surface-production of negative hydrogen ions is not desirable from the point of view of operating steady state ion sources. We demonstrated the production of negative hydrogen ions in cesium-free discharge by using the magnetized sheet plasma. We were confirm that there is negative hydrogen ions by mass spectrometry and performed an experiment of negative hydrogen ion extraction. Under a secondary hydrogen gas entering the hydrogen plasma, the peak position of the hydrogen plasma nH- is localized in the periphery of the sheet plasma. It is found that hydrogen negative ions are formed by the dissociative attachment of low energy electrons (Te = 1-2 eV) to highly vibrationally excited molecules, which are attributed to the electron-impact excitation of molecules by high energy electrons (Te > 10 eV) in the plasma column, and are transported to the periphery of the sheet plasma. The hydrogen negative an ions density were detected using an omegatron mass analyzer, while the electron density and temperature were measured using a Langmuir probe. The maximum negative hydrogen ion beam is successfully extracted using grids located in the periphery of the sheet plasma. The negative hydrogen ion current density is about 20 mA/cm22 at extraction voltage is 2 kV at a neutral gas pressure of 0.3 Pa and discharge current of 50 A.
Co-authors
Akira Tonegawa
(Tokai University, 4-1-1, Kitakaname, Hiratsuka-shi, Kanagawa, Japan)
Kazutaka Kawamura
(Tokai University, 4-1-1, Kitakaname, Hiratsuka-shi, Kanagawa, Japan)
Kohnosuke Sato
(Chubu Electric Power Co. lnc., 20-1, Kitasekiyama, Ohdaka-cyo, Midori-ku, Nagoya-shi, Aichu, Japan)
Takaaki Iijima
(Tokai University, 4-1-1, Kitakaname, Hiratsuka-shi, Kanagawa, Japan)
Takuya Hase
(Tokai University, 4-1-1, Kitakaname, Hiratsuka-shi, Kanagawa, Japan)
Toshikio Takimoto
(Tokai University, 4-1-1, Kitakaname, Hiratsuka-shi, Kanagawa, Japan)
