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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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 -