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Tetsuo Fukuchi Yukihiro Yamaguchi Takuya Nayuki Koshichi Nemoto Kiichiro Uchino 《Electrical Engineering in Japan》2004,146(4):10-17
A laser wavefront sensor of the Shack‐Hartmann type capable of simultaneous measurement at two wavelengths was constructed. The sensor uses a single optical path, and is suited for applications such as high‐voltage discharges in air, in which large insulation distances are necessary. The sensor was used to detect optical path differences due to an impulse discharge in air across a needle–plane electrode gap of gap length 17 mm. Optical path differences were measured at laser wavelengths of 532 and 1064 nm at 1.6 µs after insulation breakdown across the gap. From the difference in optical path differences at the two wavelengths, a line‐integrated electron density distribution in the direction perpendicular to the gap was obtained near the high‐voltage electrode. The distribution had a peak value of 1.4 × 1020m?2 and a full width at half maximum of 4.4 mm. Because of the coverage of a large observation area including the entire gap, the spatial resolution was 1.4 mm, which was inadequate to obtain the precise form of the electron density distribution. However, the results show the possibility of applying laser wavefront sensing to electron density measurement. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 10–17, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10247 相似文献
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Quantum entanglement and its paradoxical properties hold the key to an information processing revolution. Much attention has focused recently on the challenging problem of characterizing entanglement. Entanglement for a two qubit system is reasonably well understood; however, the nature and properties of multiple qubit systems are largely unexplored. Motivated by the importance of such systems in quantum computing, we show that typical pure states of N qubits are highly entangled but have decreasing amounts of pairwise entanglement (measured using the Wootter concurrence formula) as N increases. Above six qubits, very few states have any pairwise entanglement and, generally, for a typical pure state of N qubits there is a sharp cut-off where its subsystems of size m become positive partial transpose (i.e. separable or only bound entangled) around N ? 2m + 3, based on numerical analysis up to N = 13. 相似文献
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Tetsuo Fukuchi Takuya Nayuki Koshichi Nemoto Kiichiro Uchino 《Electrical Engineering in Japan》2004,148(2):76-83
An acousto‐optic laser deflector was used as a shutter for high‐speed imaging of laser interference fringes using an ordinary CCD camera. The exposure duration was set by the pulse width of the high‐frequency signal applied to the acousto‐optic deflector. Changes in laser interference fringes due to an impulse discharge in air were obtained at an exposure duration of 4 µs. By applying a sequence of high‐frequency signals with different frequency, the beam was deflected to four different angles at different times, allowing four interference images to be captured on a single video frame. This was used for time‐resolved imaging of the interference fringe pattern. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 76–83, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20011 相似文献
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Akito SAGISAKA Hiroyuki DAIDO Alexander S. PIROZHKOV Micbiaki MORI Akifumi YOGO Koichi OGURA Satoshi ORIMO Mamiko NISHIUCHI Jinglong MA Hiromitsu KIRIYAMA Shuhei KANAZAWA Shuji KONDO Yoshiki NAKAI Takuya SHIMOMURA Manabu TANOUE Atsushi AKUTSU Hajime OKADA Tomohiro MOTOMURA Tetsuya KAWACHI Sergei V. BULANOV Timur Zh. ESIRKEPOV Shigeki NASHIMA Makoto HOSODA Hideo NAGATOMO Yuji OISHI Koshichi NEMOTO II Woo CHOI Seong Ku LEE Jongmin LEE 《中国光电子学前沿》2009,2(3)
We simultaneously observed both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a thin-foil target.The maximum proton energy of ~2.3 MeV and an intense THz radiation were observed at the pulse duration of ~30fs.We also measured the proton beam and UV harmonics from a thin-foil target by changing the laser pulse duration.In the case of the ~500 fs, peaks of UV harmonics up to fourth order appeared.This unique combination of the multiple beams will provide useful applications such as pump-probe experiments. 相似文献
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R-T and I-V characteristics of single grains and grain boundaries in large-grained BaTiO3 PTC ceramics were studied with a two-probe technique using a micromanipulator and fine Al wire. The PTC originates in the grain boundary only and behaves differently in each boundary. Even below Tc , the ceramic resistance depends almost entirely on the boundary. I-V characteristics in the boundary follow Ohm's law and conduction by a space-charge-limited current with a trap, using different applied voltages. The PTC anomaly relates to activation of the trap in the boundary, not to barrier height. A band model in the intergranular layer, with dielectric BaTiO3 and the trap, is proposed. 相似文献
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Tetsuo Fukuchi Koshichi Nemoto 《IEEJ Transactions on Electrical and Electronic Engineering》2009,4(1):125-129
Neutral density variations accompanying progression of streamers across needle-to-rod air gaps of length 0.75 and 1 m were observed with the use of a laser shadowgraph system consisting of astronomical telescopes for beam expansion and reduction, and an acousto-optic laser deflector for high-speed imaging. The system had a spatial resolution of about 1 mm over an annular observation region of outer diameter 28 cm and inner diameter 11 cm, and a temporal resolution in the order of microseconds. The system was also used to observe neutral density variations accompanying shock waves which resulted from a spark discharge. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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Norio Kobayashi Koshichi Noto Manabu Ikebe Yoshio Muto 《Journal of Low Temperature Physics》1974,17(5-6):575-594
The thermal conductivity of the type II superconductors Ta95Nb5, Ta80Nb20, Ta60Nb40, and Ta20Nb80 has been measured as a function of magnetic field up to 14 kOe and of temperature between 0.5 and 4.5 K. The temperature dependence of the thermal conductivity in the superconducting state is well accounted for on the basis of the Bardeen, Rickayzen, and Tewordt theory above 0.4T
c
. The lattice thermal conductivity limited by dislocation scattering is observed below 0.3T
c
. The thermal conductivity near the upper critical fieldH
c2
shows a linear dependence on magnetic field as predicted theoretically by Caroli and Cyrot. After the correction of the phonon contribution, the experimental results for the dirtiest sample, Ta60Nb40, are found in good quantitative agreement with the theory. Deviations from the theory for less dirty alloys depend on the electron mean free path. 相似文献
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Hasegawa S Takashima R Todoriki M Kikkawa S Soda K Takano K Oishi Y Nayuki T Fujii T Nemoto K 《The Review of scientific instruments》2011,82(3):033301
We evaluate the simplified method using the Lambert-Beer law to measure the temperature of bremsstrahlung photon generated by an ultraintense laser. Analytical values are compared to the results of the Monte Carlo calculation of GEANT4 and they agreed very well on the condition of the appropriate distance between the attenuator and the detector. We performed the experiment to measure the temperature of bremsstrahlung x-ray emitted from a metal target irradiated by a Ti:sapphire laser with 76 mJ, 72 fs, 2.2 × 10(18) W∕cm(2). For a Cu target of 30 μm thick, the photon temperature was reasonably determined to be 0.18 MeV, which is in good agreement with previous studies. 相似文献
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An acousto‐optic laser deflector was used to image the intensity distribution of a continuous wave laser of microsecond order. Undeflected light was blocked while the deflected light was directed to a CCD camera, which allowed imaging of the incident laser intensity distribution of microsecond order. Experiments using a test pattern showed that there was no distortion in the deflected image. The resolution limit, estimated from diffractive effects, was about 0.2 mrad. Using this method of high‐speed imaging, density variations accompanying laser‐induced breakdown in air were visualized by shadowgraphy and interferometry. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(3): 55–61, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20386 相似文献