title: Upgraded millimeter-wave interferometer for measuring the electron density during the beam extraction in the negative ion source.
abstract: The upgraded millimeter-wave interferometer with the frequency of 70 GHz is installed on a large-scaled negative ion source. Measurable line-averaged electron density is from 2 × 1015to 3 × 1018m-3in front of the plasma grid. Several improvements such as the change to shorter wavelength probing with low noise, the installation of special ordered horn antenna, the signal modulation for a high accuracy digital phase detection, the insertion of insulator, and so on, are carried out for the measurement during the beam extraction by applying high voltage. The line-averaged electron density is successfully measured and it is found that it increases linearly with the arc power and drops suddenly at the beam extraction.
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Tokuzawa
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kisaki
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nagaoka
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tsumori
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Osakabe
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Takeiri
authors.affiliation: National Institutes of Natural Sciences, 4-3-13 Toranomon, Minato-ku, Tokyo 105-0001, Japan.
authors.forename: O
authors.initials: O
authors.lastname: Kaneko