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Bakeable vacuum feedthrough with 22 pins
Bakeable vacuum feedthrough with 22 pins received 1 February 1977 H Ishimaru, National Laboratory for High Energy Physics, Oho-machi, Tsukuba-gun, Ibaraki-ken, Japan
A bakeable (300°C), small size (outer diameter, 28 mm), quick contact (Burndy connector G6F18-22 SNE, G18-22S and RC 20M-13D28), gold plated and weldable 22-pins vacuum feedthrough is described.
in our laboratory we have recently constructed many devices which required multi-pin vacuum feedthroughs. The feedthroughs are to be used for the monitor system of the 12 GeV proton synchrotron 1 such as profile monitors and emittance monitors, etc. Since they should be able to resist an intense
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2
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b)
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5/
~
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radiation dose as well as be suitable for ultrahigh vacuum which necessitates baking at high temperature, epoxy resin, other organic materials or glass could not be used for insulators. Ceramic-Kovar seal multi-pin feedthroughs fulfil these various requirements, but no commercially available feedthroughs 2 fulfil the requirements of resistance to the atmosphere and good electrical contact for many baking cycles. As shown in Figure l, the feedthrough consists of an outer conductor, 22 conducting pins and the insulator. All the conductors are made of Kovar. The outer conductor is to be welded to a vacuum envelope or a metal flange. These conductors are insulated from each other by metallized ceramic (98 ~ alumina: Kyocera A 473a). Kovar is made rusty by the baking procedure, so the surfaces of the conductor are coated with about 2 /~m thick gold for good electrical contact. At the end of the skirt the surface is not coated so as to ensure satisfactory welding. On the atmospheric side, each pin is flexible radially and the geometrical arrangement is precise, so that a commercially available plug matches this feedthrough. The 22-pins Burndy 4 connector wit h cable mates to this 22-pin vacuum feedthrough and can be connected or removed quickly on both the atmospheric side and the vacuum side. The connector on the atmospheric side is Burndy G6Fl 8-22SNE and on the vacuum side is Burndy G18-22S. The metal housing of the connector in the vacuum should be removed as shown in Figure 2. The insulator of the commercially available connector is plastic. For ultrahigh vacuum, the pin contact used should be Burndy RC 20M-13D28. After it is welded to a vacuum vessel, the welded surfaces of the
(o) t 0
I I0 m m
Figure 1. (a) Top view of 22-pin feedthrough. (b) Cross sectional view. (c) End view in vacuum. (1) Outer sleeve-Kovar, (2) pin conductor-Kovar, (3) insulator-ceramic, (4) washer-Kovar, (5) ceramic to metal seal--silver solder, (6) argon arc weld to the vacuum fitting.
Vacuum/volume 27/numbers 7/8.
Figure 2. A photograph of the bakeable 22-pin vacuum feedthrough, the outer connector (Burndy G6F18-22SNE), the inner connector (Burndy G18-22S) for high vacuum and inner contact (Burndy RC 20M-13D28) for ultrahigh vacuum.
Pergamon Press~Printedin Great Britain
465
H Ishimaru: Bakeable vacuum feedthrough with 22 pins
feedthrough and tile vessel are glass-bead-blasted to clean them. The feedthroughs were tested by a He leak detector and confirmed to have a leak rate of less than 10-1o atom cm 3 s-1. The K o v a r - c e r a m i c seals of this type are mechanically strong enough and safely withstand baking cycles at a temperature of up to 300°C. If this feedthrough is used at or near the r o o m temperature it should last indefinitely. The electrical insulation provided by the ceramic is also found to be very good: at least 10 t i ..Q between the conductors. The maximum rating of each pin is 3 A. The maximum voltage between each conductor is about 1000 V dc. The resulting assembly is compatible with ultrahigh vacuum operation and is resistant to strong radioactive radiation. This
466
type of feedthrough has been widely used for a particle accelerator, a nuclear fusion apparatus and a molecular physics device. Acknowledgements Acknowledgement is made to Kyoto Ceramic Co Ltd for their work on the feedthrough construction. References t Annual Report 1973-1976, National Laboratory for High Energy Physics, Japan. 2 Varian, Vacuum Division, 611 Hansen Way/Palo Alto, California 94303, USA. a Kyoto Ceramic Co Ltd, Kyoto, Japan. " Burndy Electronic Products, Norwalk, Conn. 06852, USA.
A bakeable (300°C), small size (outer diameter, 28 mm), quick contact (Burndy connector G6F18-22 SNE, G18-22S and RC 20M-13D28), gold plated and weldable 22-pins vacuum feedthrough is described.
in our laboratory we have recently constructed many devices which required multi-pin vacuum feedthroughs. The feedthroughs are to be used for the monitor system of the 12 GeV proton synchrotron 1 such as profile monitors and emittance monitors, etc. Since they should be able to resist an intense
(c}
2
I
/
b)
f6
// x2 //
5/
~
m
radiation dose as well as be suitable for ultrahigh vacuum which necessitates baking at high temperature, epoxy resin, other organic materials or glass could not be used for insulators. Ceramic-Kovar seal multi-pin feedthroughs fulfil these various requirements, but no commercially available feedthroughs 2 fulfil the requirements of resistance to the atmosphere and good electrical contact for many baking cycles. As shown in Figure l, the feedthrough consists of an outer conductor, 22 conducting pins and the insulator. All the conductors are made of Kovar. The outer conductor is to be welded to a vacuum envelope or a metal flange. These conductors are insulated from each other by metallized ceramic (98 ~ alumina: Kyocera A 473a). Kovar is made rusty by the baking procedure, so the surfaces of the conductor are coated with about 2 /~m thick gold for good electrical contact. At the end of the skirt the surface is not coated so as to ensure satisfactory welding. On the atmospheric side, each pin is flexible radially and the geometrical arrangement is precise, so that a commercially available plug matches this feedthrough. The 22-pins Burndy 4 connector wit h cable mates to this 22-pin vacuum feedthrough and can be connected or removed quickly on both the atmospheric side and the vacuum side. The connector on the atmospheric side is Burndy G6Fl 8-22SNE and on the vacuum side is Burndy G18-22S. The metal housing of the connector in the vacuum should be removed as shown in Figure 2. The insulator of the commercially available connector is plastic. For ultrahigh vacuum, the pin contact used should be Burndy RC 20M-13D28. After it is welded to a vacuum vessel, the welded surfaces of the
(o) t 0
I I0 m m
Figure 1. (a) Top view of 22-pin feedthrough. (b) Cross sectional view. (c) End view in vacuum. (1) Outer sleeve-Kovar, (2) pin conductor-Kovar, (3) insulator-ceramic, (4) washer-Kovar, (5) ceramic to metal seal--silver solder, (6) argon arc weld to the vacuum fitting.
Vacuum/volume 27/numbers 7/8.
Figure 2. A photograph of the bakeable 22-pin vacuum feedthrough, the outer connector (Burndy G6F18-22SNE), the inner connector (Burndy G18-22S) for high vacuum and inner contact (Burndy RC 20M-13D28) for ultrahigh vacuum.
Pergamon Press~Printedin Great Britain
465
H Ishimaru: Bakeable vacuum feedthrough with 22 pins
feedthrough and tile vessel are glass-bead-blasted to clean them. The feedthroughs were tested by a He leak detector and confirmed to have a leak rate of less than 10-1o atom cm 3 s-1. The K o v a r - c e r a m i c seals of this type are mechanically strong enough and safely withstand baking cycles at a temperature of up to 300°C. If this feedthrough is used at or near the r o o m temperature it should last indefinitely. The electrical insulation provided by the ceramic is also found to be very good: at least 10 t i ..Q between the conductors. The maximum rating of each pin is 3 A. The maximum voltage between each conductor is about 1000 V dc. The resulting assembly is compatible with ultrahigh vacuum operation and is resistant to strong radioactive radiation. This
466
type of feedthrough has been widely used for a particle accelerator, a nuclear fusion apparatus and a molecular physics device. Acknowledgements Acknowledgement is made to Kyoto Ceramic Co Ltd for their work on the feedthrough construction. References t Annual Report 1973-1976, National Laboratory for High Energy Physics, Japan. 2 Varian, Vacuum Division, 611 Hansen Way/Palo Alto, California 94303, USA. a Kyoto Ceramic Co Ltd, Kyoto, Japan. " Burndy Electronic Products, Norwalk, Conn. 06852, USA.