Dielectric window for reactor like ICRF vacuum transmission line

Liisa Heikinheimo, Juha Linden, A. Kaye, Seppo Orivuori, Samuli Saarelma, Seppo Tähtinen, R. Walton, Frej Wasastjerna, J.A. Heikkinen (Corresponding Author)

    Research output: Contribution to journalArticleScientificpeer-review

    1 Citation (Scopus)

    Abstract

    The dielectric window of a 35–60 MHz ion cyclotron resonance frequency (ICRF) transmission line is designed for reactor conditions in due consideration of irradiation, dielectric heating, fabrication issues, and remote handling. Electric field, temperature distribution, and thermal stresses are evaluated for beryllia and alumina dielectrics using finite element codes. The analysis is made for two annular ceramic septa joining coaxial water-cooled conductors having maximum operating 50 kV peak rf voltage and 30 Ω characteristic impedance. For unfavourable irradiation conditions (>1023 n/m2 neutron fluence), alumina is found to be heated excessively to about 1000 °C with unacceptable stresses. For moderately irradiated beryllia (<1022 n/m2) or for unirradiated alumina of specific grades (tan δ comparable or less than 5×10−4), the temperature and the thermal stresses are found to stay acceptable provided niobium or titanium is used as a conductor. Beryllia (BeO) is chosen as a candidate for the window ceramic because of its better thermal conductivity and smaller thermal expansion mismatch with the conductor material helping also the manufacturing process. The characteristics for the ceramic/metal joints are estimated for candidate conductor and ceramic (alumina) materials. Vacuum brazing using active filler materials provides sufficiently good conditions for heat conduction across the joint, and the joints appear to be tight enough. Suitable window location on the transmission line is investigated by calculating neutron fluences at the window using an experimental reactor like configuration with 2500 h total burn time (1500 MW).
    Original languageEnglish
    Pages (from-to)419-436
    Number of pages18
    JournalFusion Engineering and Design
    Volume55
    Issue number4
    DOIs
    Publication statusPublished - 2001
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Cyclotron resonance
    Beryllia
    Electric lines
    Alumina
    Vacuum
    Ions
    Thermal stress
    Neutrons
    Dielectric heating
    Vacuum brazing
    Irradiation
    Experimental reactors
    Cermets
    Niobium
    Heat conduction
    Joining
    Thermal expansion
    Fillers
    Thermal conductivity
    Temperature distribution

    Keywords

    • Dielectric window
    • Vacuum transmission line
    • Diagnostics

    Cite this

    Heikinheimo, L., Linden, J., Kaye, A., Orivuori, S., Saarelma, S., Tähtinen, S., ... Heikkinen, J. A. (2001). Dielectric window for reactor like ICRF vacuum transmission line. Fusion Engineering and Design, 55(4), 419-436. https://doi.org/10.1016/S0920-3796(01)00216-2
    Heikinheimo, Liisa ; Linden, Juha ; Kaye, A. ; Orivuori, Seppo ; Saarelma, Samuli ; Tähtinen, Seppo ; Walton, R. ; Wasastjerna, Frej ; Heikkinen, J.A. / Dielectric window for reactor like ICRF vacuum transmission line. In: Fusion Engineering and Design. 2001 ; Vol. 55, No. 4. pp. 419-436.
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    abstract = "The dielectric window of a 35–60 MHz ion cyclotron resonance frequency (ICRF) transmission line is designed for reactor conditions in due consideration of irradiation, dielectric heating, fabrication issues, and remote handling. Electric field, temperature distribution, and thermal stresses are evaluated for beryllia and alumina dielectrics using finite element codes. The analysis is made for two annular ceramic septa joining coaxial water-cooled conductors having maximum operating 50 kV peak rf voltage and 30 Ω characteristic impedance. For unfavourable irradiation conditions (>1023 n/m2 neutron fluence), alumina is found to be heated excessively to about 1000 °C with unacceptable stresses. For moderately irradiated beryllia (<1022 n/m2) or for unirradiated alumina of specific grades (tan δ comparable or less than 5×10−4), the temperature and the thermal stresses are found to stay acceptable provided niobium or titanium is used as a conductor. Beryllia (BeO) is chosen as a candidate for the window ceramic because of its better thermal conductivity and smaller thermal expansion mismatch with the conductor material helping also the manufacturing process. The characteristics for the ceramic/metal joints are estimated for candidate conductor and ceramic (alumina) materials. Vacuum brazing using active filler materials provides sufficiently good conditions for heat conduction across the joint, and the joints appear to be tight enough. Suitable window location on the transmission line is investigated by calculating neutron fluences at the window using an experimental reactor like configuration with 2500 h total burn time (1500 MW).",
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    Heikinheimo, L, Linden, J, Kaye, A, Orivuori, S, Saarelma, S, Tähtinen, S, Walton, R, Wasastjerna, F & Heikkinen, JA 2001, 'Dielectric window for reactor like ICRF vacuum transmission line', Fusion Engineering and Design, vol. 55, no. 4, pp. 419-436. https://doi.org/10.1016/S0920-3796(01)00216-2

    Dielectric window for reactor like ICRF vacuum transmission line. / Heikinheimo, Liisa; Linden, Juha; Kaye, A.; Orivuori, Seppo; Saarelma, Samuli; Tähtinen, Seppo; Walton, R.; Wasastjerna, Frej; Heikkinen, J.A. (Corresponding Author).

    In: Fusion Engineering and Design, Vol. 55, No. 4, 2001, p. 419-436.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Dielectric window for reactor like ICRF vacuum transmission line

    AU - Heikinheimo, Liisa

    AU - Linden, Juha

    AU - Kaye, A.

    AU - Orivuori, Seppo

    AU - Saarelma, Samuli

    AU - Tähtinen, Seppo

    AU - Walton, R.

    AU - Wasastjerna, Frej

    AU - Heikkinen, J.A.

    PY - 2001

    Y1 - 2001

    N2 - The dielectric window of a 35–60 MHz ion cyclotron resonance frequency (ICRF) transmission line is designed for reactor conditions in due consideration of irradiation, dielectric heating, fabrication issues, and remote handling. Electric field, temperature distribution, and thermal stresses are evaluated for beryllia and alumina dielectrics using finite element codes. The analysis is made for two annular ceramic septa joining coaxial water-cooled conductors having maximum operating 50 kV peak rf voltage and 30 Ω characteristic impedance. For unfavourable irradiation conditions (>1023 n/m2 neutron fluence), alumina is found to be heated excessively to about 1000 °C with unacceptable stresses. For moderately irradiated beryllia (<1022 n/m2) or for unirradiated alumina of specific grades (tan δ comparable or less than 5×10−4), the temperature and the thermal stresses are found to stay acceptable provided niobium or titanium is used as a conductor. Beryllia (BeO) is chosen as a candidate for the window ceramic because of its better thermal conductivity and smaller thermal expansion mismatch with the conductor material helping also the manufacturing process. The characteristics for the ceramic/metal joints are estimated for candidate conductor and ceramic (alumina) materials. Vacuum brazing using active filler materials provides sufficiently good conditions for heat conduction across the joint, and the joints appear to be tight enough. Suitable window location on the transmission line is investigated by calculating neutron fluences at the window using an experimental reactor like configuration with 2500 h total burn time (1500 MW).

    AB - The dielectric window of a 35–60 MHz ion cyclotron resonance frequency (ICRF) transmission line is designed for reactor conditions in due consideration of irradiation, dielectric heating, fabrication issues, and remote handling. Electric field, temperature distribution, and thermal stresses are evaluated for beryllia and alumina dielectrics using finite element codes. The analysis is made for two annular ceramic septa joining coaxial water-cooled conductors having maximum operating 50 kV peak rf voltage and 30 Ω characteristic impedance. For unfavourable irradiation conditions (>1023 n/m2 neutron fluence), alumina is found to be heated excessively to about 1000 °C with unacceptable stresses. For moderately irradiated beryllia (<1022 n/m2) or for unirradiated alumina of specific grades (tan δ comparable or less than 5×10−4), the temperature and the thermal stresses are found to stay acceptable provided niobium or titanium is used as a conductor. Beryllia (BeO) is chosen as a candidate for the window ceramic because of its better thermal conductivity and smaller thermal expansion mismatch with the conductor material helping also the manufacturing process. The characteristics for the ceramic/metal joints are estimated for candidate conductor and ceramic (alumina) materials. Vacuum brazing using active filler materials provides sufficiently good conditions for heat conduction across the joint, and the joints appear to be tight enough. Suitable window location on the transmission line is investigated by calculating neutron fluences at the window using an experimental reactor like configuration with 2500 h total burn time (1500 MW).

    KW - Dielectric window

    KW - Vacuum transmission line

    KW - Diagnostics

    U2 - 10.1016/S0920-3796(01)00216-2

    DO - 10.1016/S0920-3796(01)00216-2

    M3 - Article

    VL - 55

    SP - 419

    EP - 436

    JO - Fusion Engineering and Design

    JF - Fusion Engineering and Design

    SN - 0920-3796

    IS - 4

    ER -