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Volume 128, Issue 10
Displaying 1-9 of 9 articles from this issue
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Special Issue on 2007 Japan-Korea Joint Symposium on Electrical Discharge and High Voltage Engineering
Special Issue Paper
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Osamu Yamamoto, Hirotaka Hayashi, Toshihiko Wadahama, Daisuke Takeda, ...2008 Volume 128 Issue 10 Pages 606-610
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSThis paper deals with charging characteristics of the inner surface of an insulating hollow cylinder in vacuum. We conducted measurements of electric field strength near the triple points on cathode by using an electrostatic probe. Also we conducted a computer simulation of charging based on the Secondary Electron Emission Avalanche (SEEA) mechanism. These results are compared with those obtained previously for solid cylinders. As a result, we have clarified that hollow cylinders acquire surface charge which is larger than that of solid cylinders. We have also found that charge controlling effect by roughening the inner surface, which have been proved effective to depress charging on the surface of solid cylinders in our previous studies, is limited for hollow cylinders.View full abstractDownload PDF (889K) -
Brush-like Discharge Extending from a Grounded Electrode toward a Large-scale Charged Particle CloudKenji Toki, Shin-ichi Migita, Yoshio Higashiyama2008 Volume 128 Issue 10 Pages 611-614
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSElectrostatic discharge occurring between a large-scale charged particle cloud and a grounded spherical electrode was investigated. The charged particle cloud was formed by the cloud generators consisting of a blower and a corona charger. To cause electrostatic discharges between the cloud and a grounded electrode with reproducibility, the grounded spherical electrode with 100 or 125 mm in diameter was set at the outside of the cloud. The charge quantity in a charged particle cloud affected the number of discharges, discharge current and charge quantity. Under the condition of applied voltage to the corona charger of 19 kV, peak value of discharge current for the electrode of 100 and 125 mm diameter was 3.0 and 4.8 A and the charge quantities neutralized in a single discharge was 1.9 and 2.4 μC, respectively. The peak current depends strongly on the diameter of the spherical electrode.View full abstractDownload PDF (735K) -
Takeshi Kitajima, Akihiro Kubota, Toshiki Nakano2008 Volume 128 Issue 10 Pages 615-618
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSNitrogen atom densities in rare-gas diluted N2 plasmas are diagnosed by using Vacuum Ultra Violet Absorption Spectroscopy (VUVAS). The influence of rare-gas dilution for low pressure (20 mTorr) inductively coupled plasma is that N atom density shows a peak around 3 % of N2 fraction due to the increase of the high energy electrons. The N2 ion density, another precursor for nitridation, did not show a peak even for the high rare-gas fraction. On the other hand, capacitively coupled plasma operated at 0.5 Torr range showed no steep increase of N atom density. The optical diagnostics shows that rare-gas dilution of N2 plasma leads to the change of reactant flux ratio between neutral atoms and ions.View full abstractDownload PDF (580K) -
Sebastian Gnapowski, Chobei Yamabe, Satoshi Ihara2008 Volume 128 Issue 10 Pages 619-623
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSAn ozonizer using a rotating electrode was used to improve the ozone production characteristics. The ozone concentration increased up to maximum about two times lager compared with the case of no rotation. The input power increased with the rotating speed and discharge area grew up too. Both the obtained ozone concentration and the ozone production efficiency with rotating electrode more improved compared with the case of no rotating electrode. One of the reasons came from the increase of discharge length of canals during the rotation of electrode.View full abstractDownload PDF (818K) -
Youhei Hizume, Atsushi Okita, Akinori Oda, Hirotake Sugawara, Yoshiyuk ...2008 Volume 128 Issue 10 Pages 624-628
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSA CH4/H2 radio frequency capacitively coupled plasma used for synthesis of carbon nanotubes (CNTs) was simulated with a 1-dimensional fluid model. The pressure of CH4 was fixed at 1 Torr and that of H2 varied from 0 to 9 Torr. When the H2 mixture ratio was 0.1, the fluxes of H2+ and H3+ to the substrate were respectively about 5 and 10 times those for the case without H2 mixing. In our previous experiment, a slight mixture of H2 promoted CNT growth. We inferred that this was because H2 maintained the activity of the catalyst particle from which CNT grew. The present numerical result supports our hypothesis. In addition, CxHy (x, y ≥ 2) accumulated with time. This accumulation is not negligible because it lowers the electron temperature. We estimated the H2 ionization rate in CH4/CxHy is about 2/3 of that in CH4. It is pointed out that we need to consider the accumulation of CxHy to improve the accuracy of the estimation of CNT growth.View full abstractDownload PDF (996K) -
Masashi Kawada, Yasushi Yamano, Yoshio Saito, Shinichi Kobayashi2008 Volume 128 Issue 10 Pages 629-634
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSIt is known that the hold-off voltages of vacuum gaps can be improved by the spark conditioning with repetitive electrical breakdowns. At the early stage of spark conditioning process, small pulse currents (not breakdowns) were observed, and in turn hold-off voltages were improved. To investigate the characteristics of the pulse current occurrences and the reason of the improvement in hold-off voltages, experiments on pulse current observations for a vacuum gap were carried out, and chemical compositions on the electrode surfaces were analyzed before and after the experiments by an X-ray photoelectron spectroscopy (XPS). Pulse current observations confirmed that the currernt peak value decreases with repetitive voltage applications and then the phenomena occurring during the conditioning process change over from pulse current event to breakdowns. The XPS analysis revealed that the electrode surface was cleaned by repetitive pulse current occurrences. This result suggests that cleaning the electrode surface by repetitive pulse current occurrences would be one of causes of the improvement in hold-off voltages of a vacuum gap at the early stage of conditioning process.View full abstractDownload PDF (726K) -
Hirokazu Ishimaru, Masatake Kawada, Katsuo Isaka2008 Volume 128 Issue 10 Pages 635-640
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSWe propose a method to estimate the number of partial discharge sources in multipath environment using the multichannel blind deconvolution method called the super-exponential deflation method. Blind deconvolution is a method of recovering transmitted signals from only observed signals without any a priori knowledge of the source signals. The deflation approach can extract a source signal which is non-Gaussian from the observed signals one by one. The deflation approach is repeated until all non-Gaussian signals are extracted, in which case the input signals become close to Gaussian noise. The eigenvalues of the spatial correlation matrix of the input signals indicate whether the input signals are Gaussian noise or not. Thus, the proposed method estimates the number of PD sources by repeating the deflation approach and analyzing the eigenvalues.View full abstractDownload PDF (542K) -
Masanori Takaoka, Tatsuya Sakoda, Masahisa Otsubo, Shigeru Akaiwa, Mas ...2008 Volume 128 Issue 10 Pages 641-646
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSThe aim of our study is to investigate the relationship between lowering of the insulation performance of cross-linked polyethylene (CV) cable and partial discharges (PDs) followed by the dielectric breakdown and to establish a diagnostic technique using an acoustic emission (AE) sensor.
In this study, we focused on characterization of AE signals detected from ethylene propylene rubbers (EPRs) used as insulating materials of CV cables. Elastic waves with various frequencies were added to the surface of the EPR, and then characteristics of the detected AE signals due to the elastic waves propagated in the EPR were evaluated. We showed characteristics of Lamb waves whose low frequency components around 100 kHz were large and their small attenuation characteristics.View full abstractDownload PDF (590K) -
Hiroto Ishikawa, Yoshimichi Ohki2008 Volume 128 Issue 10 Pages 647-651
Published: October 01, 2008
Released on J-STAGE: October 01, 2008
JOURNAL FREE ACCESSPolybutylene succinate, a kind of biodegradable polymer, shows thermally stimulated polarization current (TSPC) peaks at around -35°C and 50°C. The lower-temperature TSPC peak can be well explained by dipolar polarization. As for the higher-temperature TSPC peak, the permittivity increases more significantly with a decrease in frequency, and the increment in permittivity estimated from the TSPC area agrees with the difference in permittivity at a sufficiently low frequency and at a sufficiently high frequency. It is assumed that a hetero charge layer is formed in front of the two electrodes and that such space charge is responsible for both the higher-temperature TSPC peak and the permittivity increase. The dielectric loss factor also increases with a decrease in frequency, and the increment is in good agreement with the assumption that the dielectric loss is ascribed to conduction loss due to high conductivity at high temperatures. All the results indicate that mobile ions are dominant carrier species in polybutylene succinate.View full abstractDownload PDF (729K)
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