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Volume 41, Issue 10
Displaying 1-9 of 9 articles from this issue
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Kenya AKAISHI1998 Volume 41 Issue 10 Pages 829-836
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
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Akio SAGARA1998 Volume 41 Issue 10 Pages 837-840
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
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Takashi ARAI, Kei MASAKI, Kengo MIYACHI1998 Volume 41 Issue 10 Pages 841-845
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSIt needs to make low ultimate pressure to decrease impurities in a plasma in a nuclear fusion device. Baking technique is very effective method to decrease outgassing rate from first walls and inner surface of the vacuum vessel. However, in such large vacuum vessel, e.g. JT-60, the non-uniform heating and the deformation due to thermal expansion might be very important problems. The baking technique of JT-60 is described. Two baking systems were applied to JT-60 to solve the problem of non-uniform heating. One is a circulation system of the hot nitrogen gas which is located between the inner and outer skins of the double-skin structured vacuum vessel. The other is an electric heater which apply the thick of the vessel. In order to prevent the deformation, the difference of temperature was as small as possible. By both the baking at 300°C and the conditioning such as discharge cleaning, the ultimate pressure was achieved 7.9 × 10-7 Pa.View full abstractDownload PDF (756K) -
Atsushi KAMINAGA, Takashi ARAI, Kozo KODAMA, Noboru SASAKI, Masahiro S ...1998 Volume 41 Issue 10 Pages 846-850
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSSince a vacuum vessel of JT-60 is very large (167 m3) and is combined with many components, such as magnetic coils, neutral beam injection systems and RF heating systems, etc., the position of leak testing exceeds 700. The two kind of techniques for vacuum leak test used in JT-60 has been described. Firstly the probe helium gas can be fed remotely in the three-dimensionnally sectioned 54 regions of the JT-60 torus. The leak test was very rapidly performed by using this method. Secondly the helium detector system has been modified by the additional installation of the cryopump, which reduced the background level of the deuterium gas. The sensitivity of vacuum leak test with the cryopump was two orders of magnitude larger than that of without it.
The examples of the performed vacuum leak test are stated. The vacuum leaks during experiments were 9 times. They were caused by thermal strain and plasma discharge. The vacuum leaks just after maintenance are 36 times which mainly caused by mis-installation.View full abstractDownload PDF (775K) -
Migaku TAKAHASHI1998 Volume 41 Issue 10 Pages 851-855
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSThe ultra clean sputtering process (UC-process) was introduced in the fabrication of thin film media and spin valve type Ni-Fe/25 at% Ni-Mn/Ni-Fe tri-layered films. As a result, the UC process enables the control of the fine structure of the thin films and resulted in excellent magnetic properties. This study demonstrates that the UC-process is superior to the normal process presently used and plays an important role for the thin film media and spin valve head fabrication.View full abstractDownload PDF (910K) -
Kiyotaka Wasa1998 Volume 41 Issue 10 Pages 856-862
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
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Yuji HIROSE, Itsuo ISHIKAWA, Kazuya NAGASEKI, Yukinori SAITO, Shinji S ...1998 Volume 41 Issue 10 Pages 863-869
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSDischarge plasmas of C4F8/Ar/O2 and C4F8/SF6/O2 mixtures were investigated in ionic species at a frequency of 13.56 MHz, a power of 34 W, and a pressure of 6.65 Pa (50 mTorr) or 13.3 Pa (100 mTorr). The discharge sustaining voltages in both mixtures are scarcely influenced by varying the mixing ratio of C4F8 or O2 on the order of 10% around C4F8 10%/Ar 80%/O2 10% and C4F8 10%/SF6 80%/O2 10%, respectively. Intensity ratios of some ionic species, however, change according to the mixing ratio of C4F8 or O2. From the intensity variation of O+2, O+2 and O2 are considered to be consumed by reactions with dissociation products of C4F8. In the discharge in C4F8/Ar/O2, intensity ratios of major positive ions are almost the same as those in discharge at large AT mixing ratio in C4F8/Ar. In the discharge in C4F8/SF6/O2, a major negative ion is F-, and a small number of CF-3 is observed. CF-3 seems to originate from C4F8, because its intensity increases according to the mixing ratio of C4F8. Furthermore, COF-3 and C2OF-5 are also observed.View full abstractDownload PDF (866K) -
Yusuke SUETSUGU, Masamitsu SHIRAISHI, Takashi MISHIBA, Yuichi OHNO1998 Volume 41 Issue 10 Pages 870-874
Published: October 20, 1998
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSA vacuum bellows assembly that can follow a twist motion around the axis is designed and developed. The bellows assembly consists of two normal bellows sections and a special bellows section with a corrugation oblique to the axis. A trial model with a total length of 400 mm and an inner diameter of 100 mm is able to absorb the twist up to about ± 22° (44° in total) within a twisting torque of 120 kg · cm while keeping the length constant. The bellows assembly can also follow easily the usual bending, shifting, expanding and contracting motion.View full abstractDownload PDF (1149K) -
1998 Volume 41 Issue 10 Pages 898
Published: 1998
Released on J-STAGE: October 20, 2009
JOURNAL FREE ACCESSDownload PDF (72K)
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