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Optical window sealed with indium for ultrahigh vacuum
Vacuum/volume 39/number Printed in Great Britain
G/pages 563 to 564/l
Optical window vacuum
0042-207X/89$3.00+.00 @ 1989 Pergamon Press plc
989
sealed with
H Saeki”, J Ikeda” and H Ishimaru,
National
Laboratory
indium
for ultrahigh
for High Energy Physics, Oho I- 1, Tsukuba-shi,
lbaraki- ken, 305, Japan received in revised form 8 November
1988
A bakeable (120°C) optical window sealed with indium for ultrahigh vacuum is described. The surfaces to be in contact with the seal are coated with Cr (0.05 pm) and Au (0.2 pm) using an ion plating method. Since the surfaces are sealed with an indium wire using a hot pressing method (15o”C, 85 kg cme2), the newly developed optical window is free of thermal distortion.
1. Introduction
It has been
necessary for traditional optical windows for ultrahigh vacuum to braze sleeves and windows. After brazing, thermal distortions are often found on the surfaces of the windows. Aluminium alloys with a special surface treatment are excellent materials for ultrahigh vacuum systems because of a low outgassing rate and low baking temperature (about 120°C) I,‘. The low baking temperature makes it possible to use indium as a sealing material. Therefore, an optical window sealed with indium for ultrahigh vacuum has been designed and constructed.
The window was tested for leakage using a helium leak detector. No leak was observed at a detection level of 1 x lo-” atm. cm3 s-’ at room temperature. Optical windows of this type can safely withstand baking cycles from ambient temperature to
2. Results As shown in Figure 1, the window consists of the sleeve made of aluminium alloy (A2219) and the disc made of quartz glass. The surfaces of the sleeve and the disc to be in contact with the seal, are coated with Cr (thickness 0.05 pm) and with Au (thickness 0.2 pm) on the thin film of Cr. The thin films of Cr and Au were deposited by ion plating. The sleeve was welded to a Conflat flange made of aluminium alloy (A2219) using an electron beam. The disc is 80 mm in diameter and 10 mm in thickness. The metallized sleeve and the metallized disc are connected by a circular seal made of indium using a hot pressing method (15O”C, 85 kg cm- ‘) in the atmosphere. The circular seal made of indium wire (0.5 mm in diameter) is 80.5 mm external diameter. The indium seal is about 0.1 mm thickness after forming the seal. The disc was clamped using a pressure O-ring (viton), a retaining ring (A2219) and 4 screws (2 mm in diameter) on the atmospheric side. The retaining ring is 89.5 mm external diameter, 70 mm internal diameter and 3 mm thickness. Figure 2 shows the optical window sealed with indium and welded into a Conflat flange (ICF152) made of aluminium alloy. *Matsushita Electric Industrial Osaka-fu,
571, Japan.
Co Ltd, Matsuba-cho
2-7, Kadoma-shi,
Figure 1. Structure of the optical window sealed with indium for ultrahigh vacuum. 1 Sleeve made of aluminium alloy (A2219); 2 disc made of quartz glass ; 3 circular seal made of indium ; 4 thin film of Cr ; 5 thin film of Au ; 6 Conflat flange made of aluminium alloy (A22 19) ; 7 O-ring made of viton ; 8 retaining ring made of aluminium alloy (A2219). 563
H Saaki et a/: Optical window sealed with indium
Figure 2. Optical window sealed with indium welded to a Conflat flange
Figure 3. Microscopic view of the cross-section of the seal. 1 Quartz glass
(ICF152).
2 indium ; 3 aluminium alloy.
120°C. The baking test was carried
Acknowledgements
out over 6 cycles. No leakage after the baking cycles. Figure 3 shows a microscopic view of the cross-section of the seal. It is found that the indium adheres closely to the sealing surfaces of the disc and the sleeve. Since the newly developed optical window does not involve a welding process, the window is free of the thermal distortion. It will thus be possible that the measuring accuracy of a He-Ne laser in the atmosphere could become equivalent to the accuracy in an ultrahigh vacuum environment. was detected
564
:
The authors would like to thank Dr Momose for his many helpful suggestions. This work was supported by Hakudo Co, Ltd and Musashino Seiki Co, Ltd. References
’ H Ishimaru, J Vat Sci Technol, A2, 1170 (1984). ‘M Miyamoto, Y Sumi, S Komaki, K Narushima and H Ishimaru, J Vat Sci Technol, A4,2515
(1986).
G/pages 563 to 564/l
Optical window vacuum
0042-207X/89$3.00+.00 @ 1989 Pergamon Press plc
989
sealed with
H Saeki”, J Ikeda” and H Ishimaru,
National
Laboratory
indium
for ultrahigh
for High Energy Physics, Oho I- 1, Tsukuba-shi,
lbaraki- ken, 305, Japan received in revised form 8 November
1988
A bakeable (120°C) optical window sealed with indium for ultrahigh vacuum is described. The surfaces to be in contact with the seal are coated with Cr (0.05 pm) and Au (0.2 pm) using an ion plating method. Since the surfaces are sealed with an indium wire using a hot pressing method (15o”C, 85 kg cme2), the newly developed optical window is free of thermal distortion.
1. Introduction
It has been
necessary for traditional optical windows for ultrahigh vacuum to braze sleeves and windows. After brazing, thermal distortions are often found on the surfaces of the windows. Aluminium alloys with a special surface treatment are excellent materials for ultrahigh vacuum systems because of a low outgassing rate and low baking temperature (about 120°C) I,‘. The low baking temperature makes it possible to use indium as a sealing material. Therefore, an optical window sealed with indium for ultrahigh vacuum has been designed and constructed.
The window was tested for leakage using a helium leak detector. No leak was observed at a detection level of 1 x lo-” atm. cm3 s-’ at room temperature. Optical windows of this type can safely withstand baking cycles from ambient temperature to
2. Results As shown in Figure 1, the window consists of the sleeve made of aluminium alloy (A2219) and the disc made of quartz glass. The surfaces of the sleeve and the disc to be in contact with the seal, are coated with Cr (thickness 0.05 pm) and with Au (thickness 0.2 pm) on the thin film of Cr. The thin films of Cr and Au were deposited by ion plating. The sleeve was welded to a Conflat flange made of aluminium alloy (A2219) using an electron beam. The disc is 80 mm in diameter and 10 mm in thickness. The metallized sleeve and the metallized disc are connected by a circular seal made of indium using a hot pressing method (15O”C, 85 kg cm- ‘) in the atmosphere. The circular seal made of indium wire (0.5 mm in diameter) is 80.5 mm external diameter. The indium seal is about 0.1 mm thickness after forming the seal. The disc was clamped using a pressure O-ring (viton), a retaining ring (A2219) and 4 screws (2 mm in diameter) on the atmospheric side. The retaining ring is 89.5 mm external diameter, 70 mm internal diameter and 3 mm thickness. Figure 2 shows the optical window sealed with indium and welded into a Conflat flange (ICF152) made of aluminium alloy. *Matsushita Electric Industrial Osaka-fu,
571, Japan.
Co Ltd, Matsuba-cho
2-7, Kadoma-shi,
Figure 1. Structure of the optical window sealed with indium for ultrahigh vacuum. 1 Sleeve made of aluminium alloy (A2219); 2 disc made of quartz glass ; 3 circular seal made of indium ; 4 thin film of Cr ; 5 thin film of Au ; 6 Conflat flange made of aluminium alloy (A22 19) ; 7 O-ring made of viton ; 8 retaining ring made of aluminium alloy (A2219). 563
H Saaki et a/: Optical window sealed with indium
Figure 2. Optical window sealed with indium welded to a Conflat flange
Figure 3. Microscopic view of the cross-section of the seal. 1 Quartz glass
(ICF152).
2 indium ; 3 aluminium alloy.
120°C. The baking test was carried
Acknowledgements
out over 6 cycles. No leakage after the baking cycles. Figure 3 shows a microscopic view of the cross-section of the seal. It is found that the indium adheres closely to the sealing surfaces of the disc and the sleeve. Since the newly developed optical window does not involve a welding process, the window is free of the thermal distortion. It will thus be possible that the measuring accuracy of a He-Ne laser in the atmosphere could become equivalent to the accuracy in an ultrahigh vacuum environment. was detected
564
:
The authors would like to thank Dr Momose for his many helpful suggestions. This work was supported by Hakudo Co, Ltd and Musashino Seiki Co, Ltd. References
’ H Ishimaru, J Vat Sci Technol, A2, 1170 (1984). ‘M Miyamoto, Y Sumi, S Komaki, K Narushima and H Ishimaru, J Vat Sci Technol, A4,2515
(1986).