電気学会論文誌A(基礎・材料・共通部門誌)
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
115 巻, 7 号
選択された号の論文の16件中1~16を表示しています
  • 赤崎 正則
    1995 年 115 巻 7 号 p. 549-552
    発行日: 1995/06/20
    公開日: 2008/12/26
    ジャーナル フリー
  • 趙 孟佑, 竹〓 裕正, 荒井 健次
    1995 年 115 巻 7 号 p. 553-562
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    In order to examine the basic characteristic of the plasma produced in experiments related to laser-induced lightning, computer simulations of the plasma production processes under CO2 laser irradiation are conducted. The necessary conditions for the plasma production in three neutral species, Ar, O2, and H2O, are investigated by taking into account laser energy absorption due to inverse bremsstrahlung, ionization, attachment, diffusion, recombination, chemical reactions, and other possible physical processes. The laser intensity threshold is calculated from the balance between the initial electron gain (ionization) and the loss (diffusion and attachment). For argon the threshold intensity varies widely depending on the product of the neutral density and the diffusion length. For oxygen and water vapor, laser intensity higher than 1014Wm-2 is necessary because ionization must exceed the loss due to attachment. Simulations are also conducted by taking into account the time variation of the laser intensity and the results show a reasonable agreement with the experimental results.
  • 岡部 洋典, 升方 勝己, 才木 常正, 増田 渉, 今田 剛, 八井 浄
    1995 年 115 巻 7 号 p. 563-568
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    The disturbed air and the induced impulse discharge have been visualized by a shadowgraph technique when aTEA-CO2 laser is focused to breakdown air in a rod-plane electrode configuration. The air, which is instantaneously heated near the focal point, expands rapidly, and a low density region is produced between the electrodes. Thereafter, the disturbed air diffuses gradually due to the turbulent mixing. The induced discharge flows through the interior of the disturbed air. Although the laser-produced plasma is produced instantaneously, the sparkover voltage is still high immediately after the plasma formation, and considerably decreases in 20μs-1ms after the laser irradiation. The diffusion of the disturbed air is one of the important elements to trigger the discharge gap by laser-produced plasma.
  • 西嶋 喜代人, 高橋 昭彦, 生澤 泰二
    1995 年 115 巻 7 号 p. 569-575
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    Laser-induced breakdown of quasi-uniform field gaps in atomspheric air was caused by an exicimer laser with high energy. This pulse laser up to 0.7J was focused on the different positions of a hemisphere to plane gap axis with dc voltage far, below the spontaneous breakdown voltage. The laser energy dependencies of breakdown voltage and time lag from laser irradiation to voltage collapse associated with a spark were investigated for positive and negative applied voltages and gap lengths of 1 and 2cm.
    It was found that the laser-induced breakdown voltage and time lag were dependent on laser energy, laser focused position on the gap axis and polarity of the applied voltage. The discharge processes associated with these laser induced breakdown characteristics were also observed in detail using an image converter camera, He-Ne laser interferometry and capacitive field probe. With such observed results, the breakdown mechanism was correlated with the breakdown characteristics.
  • 高橋 昭彦, 西嶋 喜代人
    1995 年 115 巻 7 号 p. 576-582
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    This paper presents a numerical analysis on the electrical breakdown process of air-like gas mixture induced by laser irradiation. We develope a computer simulation model including the Boltzmann equation to derive the electron energy distribution, and the rate equations to describe the temporal behavior of particle densities in plasmas. The calculations are performed for different laser wavelength of 308nm (XeCl), 694nm (ruby), 1.06μm (YAG) and 10.6μm (CO2). As the results, iis found that the dominant process of the laser-induced breakdown is multi-photo absorption ionization for uv lasers but cascade ionization for longer wavelangth lasers. We also investigate the effect of the laser pulse width, gas pressure, preionization, diffusion and water vapour. The results are qualitatively consistent with the experimental results which have been reported.
  • 辻 利則, 本田 親久, 内海 通弘, 田中 祀捷, 村岡 克紀, 宅間 董, 赤崎 正則, 木下 文宏, 片平 治
    1995 年 115 巻 7 号 p. 583-588
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    It is highly important to clarify the basic characteristics of plasmas produced by laser focusing for investigating the possibility of laser-induced lightning. This paper reports the electron density, electron temperature and neutral particle density in laserinduced plasmas measured by Thomson and Rayleigh scattering techniques. The electron temperature increases to 2.5eV in maximum in 3 to 3.5μs after firing the laser, and then gradually decreases in several tens of microseconds. The Rayleigh scattering measurement has shown that the rarefied air region of lower neutral particle density takes a spherical shell profile in later stages after the laser firing. This has been also confirmed by the induced discharge paths through the circumference of a plasma after 500μs.
  • 新藤 孝敏, 三木 恵, 和田 淳, 相原 良典
    1995 年 115 巻 7 号 p. 589-594
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    Recent advances of lasers suggest a possibility of laser-triggered lightning. It is necessary to make a long plasma channel for laser-triggered lightning and many experimental studies have been carried out. However, no analytical work on it has been made yet.
    In this paper, plasma production with laser propagation is calculated numerically and the results are compared with experimental results. The effects of various parameters such as laser energy and focal length on plasma production are clarified. The effects of aerosols on plasma production are also discussed.
  • 神野 雅文, 久保 寔, 板谷 良平
    1995 年 115 巻 7 号 p. 595-604
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    This paper describes the experiment triggering and guiding discharge by weak ionized channel produced by XeCl excimer laser as fundamental study for Laser Triggering of Lightning. In this experiment it was shown that XeCl excimer laser can make weak ionized channel on its light path and that CO2 laser can't make it. This weak ionized channel can guide discharge path. In order to guide discharge path, electron density required to be higher than 1.1×1016m-3. This is about only 0.05% of the density required for triggering of discharge by an air breakdown plasma.
    By using both the weak ionized channel produced by XeCl excimer laser and the air breakdown plasma heated by CO2 laser, the flashover voltage is lowered and the guided length of discharge becomes longer than those of using only XeCl excimer laser. Combining air breakdown plasma and weak ionized channel by using different wavelength laser beams, for example UV laser and IR laser, will work effective for plasma formation, triggering of lightning and guiding a lightning path.
  • 星 佳伸, 甲田 壽男, 吉田 博夫, 山中 一司, 碓井 雄一
    1995 年 115 巻 7 号 p. 605-613
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    Mechanism of the laser guided discharge was observed precisely by using high speed cameras. The following results are obtained: The radius of the metal plasma wave front varies according to the polytropic change of gases. The plasma produced by the main dischrge is found in the metal plasma produced by the laser irradiation. Both plasmas are considered to expand with the thermal energy of the main discharge. There are two types of pre-disdrarge which triggers the main discharge. The pre-discharge type I appears between the metal plasma and the anode and the type II appears at the minimum length of the anode and the cathode. The guided discharge is triggered by the pre-discharge type I and the pre-discharge type II is not observed by the camera. In the case of the misguided discharge, the pre-discharge type II triggers the main discharge when the pre-discharge type I can not trigger it and disappears.
  • 内海 通弘, 入野 仁, 槇野 武男, 田中 祀捷, 村岡 克紀, Grigory Baitsur, 木下 文宏, 片平 治, 本田 親久, ...
    1995 年 115 巻 7 号 p. 614-621
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    A long air-breakdown channel was made using a TEA. CO2 laser with an output energy of 0.5kJ in order to induce a long-gap impulse discharge. The maximum length of a plasma channel made was 18m by combined concave mirrors with a focal length of 34.3m. We have developed a new method which can measure the most effective part of the plasma channel in inducing a long-gap discharge. By using this method, it is possible to make the longest of the laser-induced sparkover for a given discharge condition. We demonstrated that the longest laser-induced sparkover length of 10m was achieved for an impulse voltage of 1.05MV.
  • 日高 邦彦, 酒井 大輔, 河野 照哉
    1995 年 115 巻 7 号 p. 622-629
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    The basic characteristics of both laser triggered and guided discharges have been studied by many researchers. In this paper, a 3.5J CO2 laser is transmitted into a rod-to-plane gap which is do electrically stressed. Trigger and guide effects of the discharge are usually observed simultaneously in the gap. However, in this study only the trigger effect is observed under some conditions. In this case, the electrical breakdown of the gap is triggered by the irradiation of laser but the breakdown path is not guided by the laser beam. The delay time between the irradiation of laser and the breakdown of the gap induced by the trigger effect varies from several hundreds μs to a few ms. The trigger effect can be caused mainly due to the drift of negative ions produced in a laser-induced plasma.
  • 猪原 哲, 毎熊 健, 佐藤 三郎, 石峯 真佐志, 山部 長兵衛
    1995 年 115 巻 7 号 p. 630-636
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    The experiments of a laser-induced discharge were carried out with CO2 laser radiation in the atmospheric ambient gases under a DC electric field. In these experiments, induced-discharge and plasma production due to the laser breakdown were suppressed with an increasing DC electric field strength. Although the laser-produced plasma was generated between the electrodes without DC electric field, both the probability of induced-discharge and plasma production decreased with the applied voltage across the electrodes. In this paper, the mechanisms of the phenomena that suppress the plasma production under applying the electric field between electrodes were discussed. It is found that the attachment processes of electrons most likely play an important role in this phenomena.
  • 池上 知顕, 新垣 秀治, 蛯原 健治, 赤崎 正則
    1995 年 115 巻 7 号 p. 637-644
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    Experiments on induction and triggering of a long-gap discharge by a laser have attracted much attention in a fundamental study of the laser-induced lightning. A plasma channel generated by the optical breakdown of the atmosphere using a high power laser is often used as a guiding path of the discharge. However, many discrete plasma beads produced near the focal point become obstacles from the viewpoint of making a long, uniform and highly conductive plasma channel. The mechanism of generation of plasma beads and an interaction between incident laser light and plasma beads have not yet been well understood. It is important to clarify these phenomena in order to make a more suitable plasma channel for the laser-induced discharge.
    To investigate the microscopic structure and the characteristics of the plasma beads produced optically by a YAG laser or a KrF excimer laser, we used a CCD camera to observe the scattering images of the incident laser due to plasma beads, and we measured the electron number density in the plasma using the Mach-Zehnder interferometer. It was found that incident laser light was strongly scattered by the plasma produced by itself, and the scattering process was dependent on the wavelength of the laser. An interferometer measurement showed that electron density in the plasma was larger than 1024m-3 at its early phase.
  • 三木 恵, 和田 淳, 新藤 孝敏, 相原 良典
    1995 年 115 巻 7 号 p. 644-652
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
    50% flashover voltage characteristics and the discharge development of positive discharges guided by CO2 lasers have been experimentally studied up to a 7 m air gap. In these experiments, we found that plasmas can guide and trigger the positive discharges under certain conditions. The applied voltage is the condition of the guide effect by laser-produced plasmas and the number of the laser-produced plasmas is the condition of trigger effect by the plasmas. On the basis of these results, we explain the mechanisms of the laser-guided positive discharges. In these mechanisms, a continuous plasma channel which is produced by the expansion of discrete plasmas play important roles. Such characteristics of the laser-guided positive discharge suggest that we must produce a continuous plasma channel at the top of the tower for laser-triggered lightning.
  • 三浦 武, 谷口 敏幸
    1995 年 115 巻 7 号 p. 652-654
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
  • 作田 忠裕, 坂下 典久, 高嶋 武, 宮本 昌広
    1995 年 115 巻 7 号 p. 654-655
    発行日: 1995/06/20
    公開日: 2008/07/15
    ジャーナル フリー
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