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Volume 32, Issue 4
Displaying 1-4 of 4 articles from this issue
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Kazuya SAITOH1989 Volume 32 Issue 4 Pages 429-435
Published: April 20, 1989
Released on J-STAGE: October 20, 2009
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Kenya AKAISHI, Yusuke KUBOTA, Akira MIYAHARA1989 Volume 32 Issue 4 Pages 436-443
Published: April 20, 1989
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSFrom purpose of vacuum use of graphite and carbon as a plasma facing material in fusion devices, test samples made from these materials which are available in Japan are prepared and occluded gas amounts in these samples have been measured with thermal desorption method. At first total gas amounts evolved on heating as-received samples in a thermal bath with a linear ramp rate from room temperature to 1400°C have been measured. The gas amounts which are normalized with sample volume of 5 cm3, distribute in the range from 7.5 × 10-1 to 1.8 × 10-2 Torr l/cm3, depending on outgassing treatments for the materials by manufacturers. The lowest value for the gas amounts is obtained from among materials which are supplied after degassing in vacuum at 2000°C at makers. Secondarily some of samples after the first thermal desorption test have been subsequently exposed to air for 50 days and reabsorbed gas amounts in the samples have been also measured. A saturation on the gas recovering has been observed and the avarage saturated gas amount is nearly the same value with the lowest gas amount for as-received samples after the higher temperature degassing. Finally derivation of a formular to calculate internal surface area of graphite is discussed according to a modeling presented for pore structure of isotropic graphite and the measured gas amount for the graphite is expressed with another normalized quantity as trapped gas molecules per unit surface area.View full abstractDownload PDF (921K) -
Baking Temperature and Baking HistoryYuichi ISHIKAWA, Kenji ODAKA, Shinjiro UEDA, Hideaki KAMOHARA1989 Volume 32 Issue 4 Pages 444-452
Published: April 20, 1989
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSReduction of outgassing from stainless steels by baking is examined as a function of baking temperature and previous baking history. The effect of baking and prebaking temperature and subsequent air exposure on the outgassing reduction is discussed in terms of the changes in the surface compositions determined by Auger electron spectroscopy and in the desorption characteristics of adsorbed gases by thermal desorption spectra.
The significance of the surface change in the outgassing reduction is pointed out. The surface compositional changes cannot fully explain the ougassing reduction and the changes in the structure and thickness of the surface oxide layer must be taken into account. This surface oxide layer is suggested to play a critical role in determining the desorption characteristics of adsorbed gases from the surface.
This surface oxide layer also contributes to the outgassing reduction during the repeated air exposure/baking cycles. Full characterization of the surface oxide layer may result in more effective process of outgassing reduction leading to the establishment of extreme high vacuum technique.View full abstractDownload PDF (1129K) -
Tsunetoshi ARIKADO, Nobuhiro HATA1989 Volume 32 Issue 4 Pages 460-464
Published: April 20, 1989
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSDownload PDF (762K)
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