The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
T. Mizutani - One of the best experts on this subject based on the ideXlab platform.
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Space Charge behavior of LDPE with a blocking electrode
Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2002Co-Authors: Chao Zhang, T. MizutaniAbstract:In this paper, to better understand the Space Charge behavior of LDPE, we tried to distinguish various processes resulting in Space Charge. A polyethylene terephthalate (PET) thin film (about 2.5 /spl mu/m) was set between LDPE (about 100 /spl mu/m) and semiconductive electrode to block carriers. Then, carriers injected from the electrode and those generated in the bulk can be separated. The Space Charge profiles in LDPE with a blocking electrode indicated that carriers generated in the bulk and injected from the aluminum cathode made little contribution to Space Charge in the specimen. Carriers injected from the semiconductive anode played an important role in Space Charge formation. No Space Charge was observed in a 100 /spl mu/m PET film under a DC field of 50 MVm/sup -1/ and PET film showed less DC current than LDPE. These suggest that a PET thin film is suitable to make a blocking electrode.
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Effects of additives and morphology on Space Charge in LDPE
Proceedings of 2001 International Symposium on Electrical Insulating Materials (ISEIM 2001). 2001 Asian Conference on Electrical Insulating Diagnosis , 2001Co-Authors: T. MizutaniAbstract:The effects of additives and morphology on Space Charge in various LDPEs have been investigated. Antioxidants, by-products of the cross-linking and oxidation products enhanced Space Charge in LDPE. The Space Charge also depended upon the physical structure (or density) of LDPE and the process of polymerization. Injected Space Charge moved more easily in LDPE with a lower density and it decayed more quickly after the short-circuit. The Space Charge distributions were affected by electrode material, temperature and applied field. The X-ray induced TSC revealed that the origins of some carrier traps are physical defects such as cavities formed by the local arrangement of molecular chains. This is one of reasons why Space Charge in LDPE is closely related to its physical structure (morphology).
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Space Charge behavior in low density polyethylene
IEEE Transactions on Dielectrics and Electrical Insulation, 2000Co-Authors: T. Mizutani, H Semi, K KanekoAbstract:The Space Charge distribution in low-density polyethylene (LDPE) was measured with the pulsed electroacoustic (PEA) method. We used three types of LDPE: LDPE-L and LDPE-H were prepared by the high pressure process, and m-LDPE was polymerized with a metallocene catalyst. Space Charge in LDPE strongly depended upon the electrode material. Semiconductive electrodes enhanced carrier injection into LDPE and, as a result, Space Charge. The density, polymerization process, applied field, temperature and so on also affected the Space Charge behavior. This Space Charge behavior was compared with the results of dc current measurements.
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Space Charge dynamics in polypropylene
The 17th Annual Meeting of the IEEE Lasers and Electro-Optics Society 2004. LEOS 2004., 1Co-Authors: T. Mizutani, E. Nakane, Kazue Kaneko, Mitsugu IshiokaAbstract:We investigated the Space Charge dynamics in polypropylene, M-PP and Z-PP which were polymerized using metallocene and Ziegler catalysts, respectively. Space Charge distributions depended upon temperature, polarity and electrode materials. Carriers injected from the semiconducting electrode played an important role in the formation of Space Charge in PP at high temperatures. The amount of Space Charge was the largest around 40/spl deg/C for both M-PP and Z-PP. They showed similar Space Charge dynamics in spite of their difference in morphology. Z-PP showed larger current than M-PP. These results were also compared with those of polyethylene and they were discussed considering the difference in morphology among M-PP, Z-PP and polyethylene.
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Space Charge distributions in insulating polymers
Proceedings of 8th International Symposium on Electrets (ISE 8), 1Co-Authors: T. MizutaniAbstract:Recently, new non-destructive techniques such as the LIPP, PIPS, PEA and TP methods have been developed to measure directly the Space Charge distributions in solid dielectrics. These techniques are very powerful to understand the Space Charge in insulating materials. In this paper, these new techniques have been briefly reviewed. The Space Charge distributions and behaviors in insulating polymers, especially in polyethylene, have been shown. The Space Charge effects on the high-field conduction and breakdown phenomena in polyethylene have been also discussed quantitatively.
M. Reiser - One of the best experts on this subject based on the ideXlab platform.
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Study of Longitudinal Space-Charge Wave Dynamics in Space-Charge Dominated Beams
Proceedings of the 2005 Particle Accelerator Conference, 2005Co-Authors: K. Tian, Rami Kishek, M. Reiser, Irving Haber, P.g. O'sheaAbstract:Understanding the dynamics of longitudinal Space-Charge waves is very important for advanced accelerator research. Although analytical solutions of Space-Charge wave equations based on the cold fluid model exist in one dimension, there are few results for two-dimensional wave evolution. One-dimensional theory predicts two eigen solutions, given an initial perturbation. One is called the fast wave, which moves toward the beam head in the beam frame and the other is termed the slow wave, which moves backward in the beam frame. In this paper, we report experimental results of Space Charge wave studies conducted on a 2.3 meter long straight beam line at the University of Maryland. An energy analyzer is used to directly measure the energy of Space-Charge waves at the end of the transport line, which demonstrates the decomposition of an initial current perturbation into a slow wave and a fast wave. A PIC code, WARP [1], is used to simulate this experiment and the behavior of longitudinal waves in Space-Charge dominated beams in an R-Z geometry. Simulations shown here also demonstrate if the initial current and velocity perturbation strengths are chosen properly, only fast or slow waves could be selectively generated.
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nonlinear behavior of localized Space Charge waves in Space Charge dominated electron beams
Physical Review Letters, 2000Co-Authors: Y Zou, J G Wang, H Suk, M. ReiserAbstract:We present experimental observations of the abnormal growth of localized nonlinear Space-Charge waves in Space-Charge dominated electron beams passing through a resistive channel. The energy width of the Space-Charge waves is measured on both ends of the channel. Previous experiments had shown that, for small initial perturbations, the energy width of the slow waves increases, while the energy width of the fast waves decreases, in agreement with linear theory. We report that in the nonlinear regime (large initial perturbations), the energy width of the fast wave increases, which is unexpected, and, to the best of our knowledge, no theory exists that would predict this phenomenon.
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observation of nonlinear behavior of localized Space Charge waves in Space Charge dominated electron beams
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999Co-Authors: J G Wang, Y Zou, H Suk, M. ReiserAbstract:We present an experimental observation of the abnormal growth of localized nonlinear fast Space-Charge waves in Space-Charge dominated electron beams passing through a dissipative channel. High-perveance electron beams with localized perturbations are launched from a gridded electron gun and transported through a short resistive-wall channel consisting of a resistive-film coated glass tube inside a long solenoid providing uniform focusing. The energy width of the Space-Charge waves developed from the perturbations is measured on both ends of the channel. The experiments have shown that the localized fast Space-Charge wave appears to grow under nonlinear perturbations; in the linear regime, as expected, the energy width of slow waves increases, while the energy width of fast waves decreases when they pass through the resistive channel.
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LOCALIZED Space-Charge WAVES IN Space-Charge DOMINATED BEAMS
International Journal of Modern Physics B, 1995Co-Authors: J G Wang, M. ReiserAbstract:The physics of Space-Charge waves in Space-Charge dominated beams is presented. This includes the generation and propagation of such waves in coasting beams, and the end effect on Space-Charge waves in bunched beams. It is shown for the first time in experiments that a single Space-Charge wave can be generated, that the geometry factor g can be measured with localized Space-Charge waves, and that both reflection and transmission take place at the ends of an initially rectangular bunch. The experimental results are supported by theoretical analyses. The application of localized Space-Charge waves as a new technique for beam diagnostics is also described.
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Studies of localized Space-Charge waves in Space-Charge dominated beams
Proceedings Particle Accelerator Conference, 1Co-Authors: J G Wang, M. ReiserAbstract:The results of the experiments on localized Space-Charge waves are presented. This includes the generation and propagation of Space-Charge waves in coasting beams, the end effect on Space-Charge waves in bunched beams, and the application of localized Space-Charge waves to beam diagnostics.
J G Wang - One of the best experts on this subject based on the ideXlab platform.
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nonlinear behavior of localized Space Charge waves in Space Charge dominated electron beams
Physical Review Letters, 2000Co-Authors: Y Zou, J G Wang, H Suk, M. ReiserAbstract:We present experimental observations of the abnormal growth of localized nonlinear Space-Charge waves in Space-Charge dominated electron beams passing through a resistive channel. The energy width of the Space-Charge waves is measured on both ends of the channel. Previous experiments had shown that, for small initial perturbations, the energy width of the slow waves increases, while the energy width of the fast waves decreases, in agreement with linear theory. We report that in the nonlinear regime (large initial perturbations), the energy width of the fast wave increases, which is unexpected, and, to the best of our knowledge, no theory exists that would predict this phenomenon.
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observation of nonlinear behavior of localized Space Charge waves in Space Charge dominated electron beams
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999Co-Authors: J G Wang, Y Zou, H Suk, M. ReiserAbstract:We present an experimental observation of the abnormal growth of localized nonlinear fast Space-Charge waves in Space-Charge dominated electron beams passing through a dissipative channel. High-perveance electron beams with localized perturbations are launched from a gridded electron gun and transported through a short resistive-wall channel consisting of a resistive-film coated glass tube inside a long solenoid providing uniform focusing. The energy width of the Space-Charge waves developed from the perturbations is measured on both ends of the channel. The experiments have shown that the localized fast Space-Charge wave appears to grow under nonlinear perturbations; in the linear regime, as expected, the energy width of slow waves increases, while the energy width of fast waves decreases when they pass through the resistive channel.
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Experimental studies of Space-Charge waves and resistive-wall instability in Space-Charge-dominated electron beams
Fusion Engineering and Design, 1996Co-Authors: J G Wang, H Suk, Martin ReiserAbstract:Abstract We present results of experiments on Space-Charge waves and longitudinal instabilities in Space-Charge-dominated beams, which are important to the design and development of induction accelerators as heavy-ion fusion drivers. By employing localized Space-Charge waves, the geometry factor-an important beam parameter for heavy-ion fusion accelerator design-has been measured and its correct formula has been verified. Space-Charge waves have been found to reflect back on the shoulder of an eroded rectangular beam bunch. This phenomenon has significant implications for the understanding and analysis of longitudinal instabilities. A resistive-wall instability experiment has clearly shown the growth of slow waves and the decay of fast waves. For localized perturbations, the amplitude change that results from the instability is smaller than expected.
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LOCALIZED Space-Charge WAVES IN Space-Charge DOMINATED BEAMS
International Journal of Modern Physics B, 1995Co-Authors: J G Wang, M. ReiserAbstract:The physics of Space-Charge waves in Space-Charge dominated beams is presented. This includes the generation and propagation of such waves in coasting beams, and the end effect on Space-Charge waves in bunched beams. It is shown for the first time in experiments that a single Space-Charge wave can be generated, that the geometry factor g can be measured with localized Space-Charge waves, and that both reflection and transmission take place at the ends of an initially rectangular bunch. The experimental results are supported by theoretical analyses. The application of localized Space-Charge waves as a new technique for beam diagnostics is also described.
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Generation of Space-Charge waves due to localized perturbations in a Space-Charge dominated beam
Physical review letters, 1993Co-Authors: J G Wang, Ding-xiong Wang, Martin ReiserAbstract:It has been found for the first time in experiments with an electron beam that Space-Charge waves can be generated not only in pairs. A single slow wave, a single fast wave, or combinations of the two waves with different amplitude and polarity relations have been produced experimentally in a Space-Charge dominated beam. Analytical solutions derived from one-dimensional fluid equations show the amplitude and polarity of each Space-Charge wave as a function of the initial perturbation parameters. The theory provides the correct interpretation of the experimental observations.
Tatsuo Takada - One of the best experts on this subject based on the ideXlab platform.
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Space Charge behavior in low density polyethylene at pre breakdown
IEEE Transactions on Dielectrics and Electrical Insulation, 2005Co-Authors: K Matsui, Takashi Maeno, Tatsuo Takada, Yasuhiro Tanaka, T Fukao, K Fukunaga, J M AlisonAbstract:It has been known that the electrical breakdown of insulating materials is strongly affected by the formation of Space Charge in the bulk of the materials. Many researchers have attempted to study the relationship between the Space Charge and the breakdown; however, it has not been clarified yet. Although the pulsed electroacoustic (PEA) method has been widely used to observe Space Charge profiles, previous works have not shown clear evidence of the influence of the Space Charge on the breakdown. Therefore, we have developed a new PEA system with an interval of 0.5 ms to observe the Space Charge distribution continuously under the ultra-high electric field. Using this system, we observed the Space Charge dynamics in the low-density polyethylene (LDPE) at and around the breakdown. We also investigated the dependence of the applied electric field on Space Charge behavior. From the results, it is found that the injected Charge packet moved faster and deeper under a relatively lower electric field rather than that under a higher electric field. Furthermore, we found that the maximum electric field in each specimen was almost the same when the breakdown happened in a specimen.
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Space-Charge characteristics in polyethylene
Journal of Applied Physics, 1998Co-Authors: X. Wang, Noboru Yoshimura, K. Murata, Y. Tanaka, Tatsuo TakadaAbstract:Space-Charge distributions in plate and coaxial cable samples of various polyethylene (PE) materials such as high density polyethylene, linear low density polyethylene, low density polyethylene, and cross-linking polyethylene under dc voltage are systematically investigated by the pulsed electro-acoustic method. The chemical structure and morphology of the sample materials are studied. The formation mechanism of Space Charge and the relations among Space Charge, chemical structure, and morphology are discussed. Our research results show that the distribution characteristics of Space Charge in various PE materials can be attributed to their chemical structure and morphology.
Martin Reiser - One of the best experts on this subject based on the ideXlab platform.
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Dispersion and Space Charge
1998Co-Authors: M. Venturini, R.a. Kishek, Martin ReiserAbstract:The presence of Space Charge affects the value of the dispersion function. On the other hand dispersion has a role in shaping the beam distribution and therefore in determining the resulting forces due to Space Charge. In this paper we present a framework where the interplay between Space Charge and dispersion for a continuous beam can be simultaneously treated. We revise the derivation of a new set of rms envelope-dispersion equations we have recently proposed in [1]. The new equations generalize the standard rms envelope equations currently used for matching to the case where bends and a longitudinal momentum spread are present. We report a comparison between the solutions of the rms envelope-dispersion equations and the results obtained using WARP, a Particle in Cell (PIC) code, in the modeling of the Maryland Electron Ring.
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Experimental studies of Space-Charge waves and resistive-wall instability in Space-Charge-dominated electron beams
Fusion Engineering and Design, 1996Co-Authors: J G Wang, H Suk, Martin ReiserAbstract:Abstract We present results of experiments on Space-Charge waves and longitudinal instabilities in Space-Charge-dominated beams, which are important to the design and development of induction accelerators as heavy-ion fusion drivers. By employing localized Space-Charge waves, the geometry factor-an important beam parameter for heavy-ion fusion accelerator design-has been measured and its correct formula has been verified. Space-Charge waves have been found to reflect back on the shoulder of an eroded rectangular beam bunch. This phenomenon has significant implications for the understanding and analysis of longitudinal instabilities. A resistive-wall instability experiment has clearly shown the growth of slow waves and the decay of fast waves. For localized perturbations, the amplitude change that results from the instability is smaller than expected.
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Generation of Space-Charge waves due to localized perturbations in a Space-Charge dominated beam
Physical review letters, 1993Co-Authors: J G Wang, Ding-xiong Wang, Martin ReiserAbstract:It has been found for the first time in experiments with an electron beam that Space-Charge waves can be generated not only in pairs. A single slow wave, a single fast wave, or combinations of the two waves with different amplitude and polarity relations have been produced experimentally in a Space-Charge dominated beam. Analytical solutions derived from one-dimensional fluid equations show the amplitude and polarity of each Space-Charge wave as a function of the initial perturbation parameters. The theory provides the correct interpretation of the experimental observations.
