Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202888
R. Romanets, V. Bolshakov, B. Dikarev, G. Karasev
Measurements of charging, discharging and voltage-reversal currents were carried out in dielectric liquids of simple molecular structure (benzene and carbon tetrachloride) and complex molecular structure (two kinds of fluorocarbon liquids). The experiments were carried out under dynamic and steady-state conditions. The slope of the voltage-current characteristics was n>1 for results obtained under dynamic conditions and n<1 for steady-state conditions. For simple liquid hydrocarbons the slope of the voltage-current characteristics was n=1 for a current time less than 0.5 s after the liquid was in equilibrium conditions. From transient measurements, mobilities of charge carriers in the fluorocarbon liquids have been determined which are similar to those in liquid crystals. The activation energy for electric conduction of the fluorocarbon liquids has been calculated.<>
{"title":"Relaxation currents in dielectric liquids","authors":"R. Romanets, V. Bolshakov, B. Dikarev, G. Karasev","doi":"10.1109/ICDL.1990.202888","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202888","url":null,"abstract":"Measurements of charging, discharging and voltage-reversal currents were carried out in dielectric liquids of simple molecular structure (benzene and carbon tetrachloride) and complex molecular structure (two kinds of fluorocarbon liquids). The experiments were carried out under dynamic and steady-state conditions. The slope of the voltage-current characteristics was n>1 for results obtained under dynamic conditions and n<1 for steady-state conditions. For simple liquid hydrocarbons the slope of the voltage-current characteristics was n=1 for a current time less than 0.5 s after the liquid was in equilibrium conditions. From transient measurements, mobilities of charge carriers in the fluorocarbon liquids have been determined which are similar to those in liquid crystals. The activation energy for electric conduction of the fluorocarbon liquids has been calculated.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128231439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202929
I. Alexeff, M. Pace, T. V. Blalock, A. Wintenberg
Observed phenomena in liquid hexane at a point cathode include the formation of a low-density region (LDR), a chain of growing electrical pulses, a succession of light flashes, and a final disruption and termination of the process. The authors address three separate effects: the inception of the process; the growth of the low-density region, with electrical pulses and light emission; and the break-up of the low-density region. It is shown that it is possible to predict the onset, growth, pulse and light phenomena, termination of growth, and break-up of the low-density region in terms of electrical and fluid dynamical processes.<>
{"title":"Possible models for the earliest prebreakdown events in DC stressed hexane","authors":"I. Alexeff, M. Pace, T. V. Blalock, A. Wintenberg","doi":"10.1109/ICDL.1990.202929","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202929","url":null,"abstract":"Observed phenomena in liquid hexane at a point cathode include the formation of a low-density region (LDR), a chain of growing electrical pulses, a succession of light flashes, and a final disruption and termination of the process. The authors address three separate effects: the inception of the process; the growth of the low-density region, with electrical pulses and light emission; and the break-up of the low-density region. It is shown that it is possible to predict the onset, growth, pulse and light phenomena, termination of growth, and break-up of the low-density region in terms of electrical and fluid dynamical processes.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128635065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202878
P. Mathy, J. Girard, G. Thomas
A TMGe detector designed for high-energy tomography has been successfully tested on a 100-Hz pulsed X-ray beam produced by a 8-MeV linear accelerator. A dynamic range of five decades has been measured, corresponding to 25-cm lead attenuation, with a maximum dose rate of 0.43 rad/s. The ratio between the electronic pulse current and the ionic interpulse current, mostly dependent on the duty cycle, was improved by means of electronics integrating during the pulse and just before. TMGe has been demonstrated to be an interesting detecting medium for fan-beam tomography, where a large number of very homogeneous, high-dynamic-range cells is required.<>
{"title":"Application of a TMGe detector to high energy pulsed X-ray tomography","authors":"P. Mathy, J. Girard, G. Thomas","doi":"10.1109/ICDL.1990.202878","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202878","url":null,"abstract":"A TMGe detector designed for high-energy tomography has been successfully tested on a 100-Hz pulsed X-ray beam produced by a 8-MeV linear accelerator. A dynamic range of five decades has been measured, corresponding to 25-cm lead attenuation, with a maximum dose rate of 0.43 rad/s. The ratio between the electronic pulse current and the ionic interpulse current, mostly dependent on the duty cycle, was improved by means of electronics integrating during the pulse and just before. TMGe has been demonstrated to be an interesting detecting medium for fan-beam tomography, where a large number of very homogeneous, high-dynamic-range cells is required.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"15 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130587261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202931
M. Haidara, A. Denat
The regular pulse regime observed in liquid cyclohexane and propane is shown to correspond to electron multiplication in the liquid phase. A rough estimation of the multiplication coefficient in the liquid phase can be made from studies in compressed hydrocarbonous gases and liquids. The length of the ionization region and the corresponding critical electrical field can be deduced. It is shown that fields E>2.5 MV/cm are required for electronic ionization in liquid cyclohexane and propane.<>
{"title":"Electron multiplication in liquid cyclohexane and propane: an estimation of the ionization coefficient","authors":"M. Haidara, A. Denat","doi":"10.1109/ICDL.1990.202931","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202931","url":null,"abstract":"The regular pulse regime observed in liquid cyclohexane and propane is shown to correspond to electron multiplication in the liquid phase. A rough estimation of the multiplication coefficient in the liquid phase can be made from studies in compressed hydrocarbonous gases and liquids. The length of the ionization region and the corresponding critical electrical field can be deduced. It is shown that fields E>2.5 MV/cm are required for electronic ionization in liquid cyclohexane and propane.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123770873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202862
M.V. Atrazhev, E. G. Dmitriev, I.T. Iakubov
It has been demonstrated that impact electron avalanche can be realized in liquid Ar, Kr and Xe. The DC- and laser-induced breakdown strengths of these liquids are lower than low-density-gas extrapolation values. This difference is due to the absence of inelastic electron energy losses in liquids.<>
{"title":"The impact ionization as the decisive factor of induced prebreakdown events in atomic liquids with high electron mobility","authors":"M.V. Atrazhev, E. G. Dmitriev, I.T. Iakubov","doi":"10.1109/ICDL.1990.202862","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202862","url":null,"abstract":"It has been demonstrated that impact electron avalanche can be realized in liquid Ar, Kr and Xe. The DC- and laser-induced breakdown strengths of these liquids are lower than low-density-gas extrapolation values. This difference is due to the absence of inelastic electron energy losses in liquids.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127083576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202906
A.T. Perez, A. Castellanos
Ion transport and mixing in periodic finite-amplitude electroconvection are studied. It is shown that ion trajectories in EHD (electrohydrodynamic) convection become chaotic when the velocity field is periodic. The separatrix gives place to an homoclinic tangle and a chaotic layer, the latter comprising a finite region of both injector and collector electrodes. For large enough values of the amplitude perturbation this resonance separatrix layer connects the inner and outer regions, thus allowing the ions to enter the otherwise empty-of-charge region. It is conjectured that this chaotic nature of ion trajectories is at the basis of the chaotic behavior of EHD flows.<>
{"title":"Time depending behavior in finite amplitude electroconvection","authors":"A.T. Perez, A. Castellanos","doi":"10.1109/ICDL.1990.202906","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202906","url":null,"abstract":"Ion transport and mixing in periodic finite-amplitude electroconvection are studied. It is shown that ion trajectories in EHD (electrohydrodynamic) convection become chaotic when the velocity field is periodic. The separatrix gives place to an homoclinic tangle and a chaotic layer, the latter comprising a finite region of both injector and collector electrodes. For large enough values of the amplitude perturbation this resonance separatrix layer connects the inner and outer regions, thus allowing the ions to enter the otherwise empty-of-charge region. It is conjectured that this chaotic nature of ion trajectories is at the basis of the chaotic behavior of EHD flows.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130452122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202909
W. He, J. Chang, M. Baird
The behavior of water droplets in an insulating liquid under the influence of electrohydrodynamic forces was experimentally investigated. Diameters and velocities of distilled water drops under both DC and pulse electric field have been measured in a rectangular cell arranged 3 degrees inclined from horizontal. For the system of distilled water dispersed in a viscous oil, uniformly spherical drops can be formed at a single stainless steel nozzle. It is shown that the droplet size could be reduced and the droplet initial velocity could be increased significantly under the influence of the EHD forces. The effect of applied pulsed electric field on the droplet formation and its subsequent motion is greater, for a given voltage, than that of DC electric field.<>
{"title":"Liquid droplet dispersion in an insulating fluid by EHD techniques","authors":"W. He, J. Chang, M. Baird","doi":"10.1109/ICDL.1990.202909","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202909","url":null,"abstract":"The behavior of water droplets in an insulating liquid under the influence of electrohydrodynamic forces was experimentally investigated. Diameters and velocities of distilled water drops under both DC and pulse electric field have been measured in a rectangular cell arranged 3 degrees inclined from horizontal. For the system of distilled water dispersed in a viscous oil, uniformly spherical drops can be formed at a single stainless steel nozzle. It is shown that the droplet size could be reduced and the droplet initial velocity could be increased significantly under the influence of the EHD forces. The effect of applied pulsed electric field on the droplet formation and its subsequent motion is greater, for a given voltage, than that of DC electric field.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129020013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202933
H. Yamashita, H. Kawai, K. Stricklett, E. F. Kelley
The effect of pressure on initiation of prebreakdown streamers in n-hexane in a nonuniform field is investigated. Using a high-magnification (100*) high-resolution (1 mu m) optical system and a high-speed camera, the initial growth of low-density streamers propagating from a needle cathode is examined at pressures ranging from 0.1 to 1.1 MPa. The initial streamer is a single filament which grows to approximately 4 mu m in diameter and 8 mu m in length before the appearance of a dense bushy structure at its tip. Oscillatory behavior of the initial streamer is observed in which the diameter of the initial streamer expands and contracts as the streamer grows. The pressure dependence of the streamer initiation voltage is shown.<>
{"title":"The effect of high pressure on prebreakdown phenomena in n-hexane","authors":"H. Yamashita, H. Kawai, K. Stricklett, E. F. Kelley","doi":"10.1109/ICDL.1990.202933","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202933","url":null,"abstract":"The effect of pressure on initiation of prebreakdown streamers in n-hexane in a nonuniform field is investigated. Using a high-magnification (100*) high-resolution (1 mu m) optical system and a high-speed camera, the initial growth of low-density streamers propagating from a needle cathode is examined at pressures ranging from 0.1 to 1.1 MPa. The initial streamer is a single filament which grows to approximately 4 mu m in diameter and 8 mu m in length before the appearance of a dense bushy structure at its tip. Oscillatory behavior of the initial streamer is observed in which the diameter of the initial streamer expands and contracts as the streamer grows. The pressure dependence of the streamer initiation voltage is shown.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115427446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202904
G. Johri, M. Johri, J. Roberts
Dielectric-response and phase-transition measurements of nematic liquid crystals at various temperatures in the frequency range near 9.00 GHz were made using a microwave cavity spectrometer. The liquid crystals chosen for study were pentyl-cyano-biphenyl (PCB) and heplyl-cyano-biphenyl (HCB). The relaxation times for these crystals were calculated using Slater's perturbation equations for a loaded resonant microwave cavity. The measured data for benziliclene butylaniline (MBBA) have also been incorporated into the analysis to compare the trend of variation of relaxation time for PCB and HCB. It is concluded that the cavity perturbation technique is a useful method for monitoring the phase changes in liquid crystals.<>
{"title":"Dielectric response and phase transition measurements of nematic liquid crystals at various temperatures in the frequency range near 9.00 GHz","authors":"G. Johri, M. Johri, J. Roberts","doi":"10.1109/ICDL.1990.202904","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202904","url":null,"abstract":"Dielectric-response and phase-transition measurements of nematic liquid crystals at various temperatures in the frequency range near 9.00 GHz were made using a microwave cavity spectrometer. The liquid crystals chosen for study were pentyl-cyano-biphenyl (PCB) and heplyl-cyano-biphenyl (HCB). The relaxation times for these crystals were calculated using Slater's perturbation equations for a loaded resonant microwave cavity. The measured data for benziliclene butylaniline (MBBA) have also been incorporated into the analysis to compare the trend of variation of relaxation time for PCB and HCB. It is concluded that the cavity perturbation technique is a useful method for monitoring the phase changes in liquid crystals.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123553797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202923
S.M. Korobejnikov, E.V. Yanshin
A model of prebreakdown processes based on discharges in bubbles which lead to bubble deformation and field increases in the vicinity of bubble poles is presented. Breakdown occurs when the field near a bubble has reached a critical value. According to the model, breakdown pressure dependence is altered when the pulse duration is decreased. If breakdown occurs at a pulse duration of less than 1 mu s, the electrical strength dependence on pressure is very weak. This is explained by bubble elongation over a short period of time, leading to a considerable increase of Coulomb forces, in turn producing a decrease of the role of external factors in the resulting action on the bubbles.<>
{"title":"Bubble model: time dependent pressure effect in liquids","authors":"S.M. Korobejnikov, E.V. Yanshin","doi":"10.1109/ICDL.1990.202923","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202923","url":null,"abstract":"A model of prebreakdown processes based on discharges in bubbles which lead to bubble deformation and field increases in the vicinity of bubble poles is presented. Breakdown occurs when the field near a bubble has reached a critical value. According to the model, breakdown pressure dependence is altered when the pulse duration is decreased. If breakdown occurs at a pulse duration of less than 1 mu s, the electrical strength dependence on pressure is very weak. This is explained by bubble elongation over a short period of time, leading to a considerable increase of Coulomb forces, in turn producing a decrease of the role of external factors in the resulting action on the bubbles.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123364551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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