Pub Date : 1994-12-31DOI: 10.1109/PLASMA.1994.589003
A. Kim, B.M. Kovalohuk, V. Kokshenev, S. Loginov
The long conduction POS technology is studied on GIT8 since 1992. The usual type POS with radial plasma injection has demonstrated slow opening into small impedance load simulating z-pinch load conditions. Also in this POS large amount of plasma was pushed by EM force into load region located about 60 cm downstream during 1.3 {mu}s conduction time. To avoid these problems a new POS design was developed called PSIPS (Plasma Switch with Inertial Plasma Stopping). The first PSIPS version was studied on GIT4. The idea is to inject plasma with high initial velocity between coaxial electrodes in direction opposite to that of the EM force. In this case part of the conduction time plasma moves along from the load, then stops and changes the direction of its movement to the opposite one. As a result the total time until plasma is removed from the switch region increases without increasing plasma mass and/or cathode diameter. The PSIPS operation at 40 kV charging voltage on GIT8 has demonstrated improved opening into small impedance load compared to the usual POS with radial injection. With cathode diameter of 160 mm it opens at 2.6 MA peak conduction current at a charge time of 1.3more » {mu}s.« less
{"title":"Git8 Long Conduction PCS Operation At 5ma Current Level","authors":"A. Kim, B.M. Kovalohuk, V. Kokshenev, S. Loginov","doi":"10.1109/PLASMA.1994.589003","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589003","url":null,"abstract":"The long conduction POS technology is studied on GIT8 since 1992. The usual type POS with radial plasma injection has demonstrated slow opening into small impedance load simulating z-pinch load conditions. Also in this POS large amount of plasma was pushed by EM force into load region located about 60 cm downstream during 1.3 {mu}s conduction time. To avoid these problems a new POS design was developed called PSIPS (Plasma Switch with Inertial Plasma Stopping). The first PSIPS version was studied on GIT4. The idea is to inject plasma with high initial velocity between coaxial electrodes in direction opposite to that of the EM force. In this case part of the conduction time plasma moves along from the load, then stops and changes the direction of its movement to the opposite one. As a result the total time until plasma is removed from the switch region increases without increasing plasma mass and/or cathode diameter. The PSIPS operation at 40 kV charging voltage on GIT8 has demonstrated improved opening into small impedance load compared to the usual POS with radial injection. With cathode diameter of 160 mm it opens at 2.6 MA peak conduction current at a charge time of 1.3more » {mu}s.« less","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131727797","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 : 1994-12-31DOI: 10.1109/PLASMA.1994.589114
M. Lampe, R. Hubbard, M. Friedman, V. Serlin
As the power and the frequency of a relativistic klystron increase, design of both modulation and extraction cavities becomes increasingly difficult. If the gap is narrow, the rf electric field begins to exceed breakdown limits. On the other hand, if the gap width exceeds a small fraction of a wavelength, typical extraction modes do not couple well, and space charge potential energy reduces efficiency and limits the current that can cross the gap. The authors present theoretical investigations, numerical simulations, and initial experimental results on a novel gap design which incorporates an inductively-loaded return-current structure. The structure consists of a series of washers (e.g., 25 in the device which has been built), mounted on a small number (e.g., four) of longitudinal conducting posts which bridge the gap. The unmodulated component of the beam current induces a return current which flows freely in the posts; as a result, the beam`s unmodulated space charge is nearly completely neutralized. The washers serve to increase the capacitive coupling between the beam and the structure, and to provide azimuthal symmetry for the charge on the structure. However, the inductance of the posts is sufficient to inhibit rf return current, and thus the structure sustains themore » longitudinal rf field in the cavity. With appropriate choice of resonant modes, it appears that gap widths exceeding a half wavelength can be used for modulation of high-current beams, as well as extraction of rf energy with high efficiency.« less
{"title":"Inductively-loaded Extended Gaps For Relativistic Klystrons","authors":"M. Lampe, R. Hubbard, M. Friedman, V. Serlin","doi":"10.1109/PLASMA.1994.589114","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589114","url":null,"abstract":"As the power and the frequency of a relativistic klystron increase, design of both modulation and extraction cavities becomes increasingly difficult. If the gap is narrow, the rf electric field begins to exceed breakdown limits. On the other hand, if the gap width exceeds a small fraction of a wavelength, typical extraction modes do not couple well, and space charge potential energy reduces efficiency and limits the current that can cross the gap. The authors present theoretical investigations, numerical simulations, and initial experimental results on a novel gap design which incorporates an inductively-loaded return-current structure. The structure consists of a series of washers (e.g., 25 in the device which has been built), mounted on a small number (e.g., four) of longitudinal conducting posts which bridge the gap. The unmodulated component of the beam current induces a return current which flows freely in the posts; as a result, the beam`s unmodulated space charge is nearly completely neutralized. The washers serve to increase the capacitive coupling between the beam and the structure, and to provide azimuthal symmetry for the charge on the structure. However, the inductance of the posts is sufficient to inhibit rf return current, and thus the structure sustains themore » longitudinal rf field in the cavity. With appropriate choice of resonant modes, it appears that gap widths exceeding a half wavelength can be used for modulation of high-current beams, as well as extraction of rf energy with high efficiency.« less","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126413634","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.588699
Junsheng Yu, W. Gillespie
The complex coefficients of this reduced equation are computed by numerical solution of appropriate eigenvalue problems. In conjunction with these analytical calculations, a highly accurate spectral code has been used to directly simulate the forced, circular shear flows. Both the analytical and the numerical results are in excellent agreement with fluid experiments [3] and show the same qualitative behaviour as the plasma experiments [l, 21, where a detailed quantitative comparison is difficult due to limitations in the experimental information. Our two approaches supplement each other in predicting the trasition to states of ever increasing complexity, even beyond regimes that have so far been experimentally accessible.
{"title":"Maximum Orbit Excursion Near Magnetoresonance In A Magnetostatic Wiggler With A Guide Magnetic Field","authors":"Junsheng Yu, W. Gillespie","doi":"10.1109/PLASMA.1994.588699","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588699","url":null,"abstract":"The complex coefficients of this reduced equation are computed by numerical solution of appropriate eigenvalue problems. In conjunction with these analytical calculations, a highly accurate spectral code has been used to directly simulate the forced, circular shear flows. Both the analytical and the numerical results are in excellent agreement with fluid experiments [3] and show the same qualitative behaviour as the plasma experiments [l, 21, where a detailed quantitative comparison is difficult due to limitations in the experimental information. Our two approaches supplement each other in predicting the trasition to states of ever increasing complexity, even beyond regimes that have so far been experimentally accessible.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115684307","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.589107
E. Lerner
Plasmas are as rich as any other state of matter in terms of distinct processes and interactions and they encompass distinguishable scales ranging from the atomic to the galactic. Opportunities in plasma science and technology reflect this breadth in phenomena and scales. New and emerging technologies enable significant qualitative and quantitative advances in experiments. For example, new microfabrication techniques make possible sophisticated particle and field probes with spatial resolution better than a Debye length in some laboratory plasmas. Indeed, certain plasma systems provide the most accessible physical systems where both the computational modeiing and relevant physical measurements are possible at all scale lengths; micro-, meso-, to macroscale.
{"title":"An Alternative Explanation Of The Cobe Data","authors":"E. Lerner","doi":"10.1109/PLASMA.1994.589107","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589107","url":null,"abstract":"Plasmas are as rich as any other state of matter in terms of distinct processes and interactions and they encompass distinguishable scales ranging from the atomic to the galactic. Opportunities in plasma science and technology reflect this breadth in phenomena and scales. New and emerging technologies enable significant qualitative and quantitative advances in experiments. For example, new microfabrication techniques make possible sophisticated particle and field probes with spatial resolution better than a Debye length in some laboratory plasmas. Indeed, certain plasma systems provide the most accessible physical systems where both the computational modeiing and relevant physical measurements are possible at all scale lengths; micro-, meso-, to macroscale.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"271 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124393628","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.588942
S. Rosenthal, C. Mendel
It is crucial to have appropriate tools for MITL design. This need is emphasized by the number of new pulsed power accelerators presently in the feasibility-study and design stages. MITL systems are essential components of most of these accelerators. MITLs are typically modeled by Telegrapher`s equations that treat electrons only through a voltage and current-dependent loss front current. The electron flow behind the loss front in a MITL system must also be included adequately in a model if it is to accurately determine the power and energy available to the load of a MITL. Often electromagnetic, relativistic PIC simulations must be done to characterize specific MITL designs. However, rather than concentrate on simulations of a specific geometry, they have recently done ensembles of simulations of generic MITL systems and have found patterns in the results that validate the use of a generalized set of Telegrapher`s equations which include electron flow. The fit to this pattern provides the value of a parameter, determined by the electron dynamics, used in the model. The simulations have also demonstrated features whose assumption makes the analytic model very simple to implement. One of these simplifying assumptions is that the flow impedance is essentially constant, nearlymore » independent of load impedance even in a short line. The new modeling equations should prove useful for the accurate characterization of MITLs, allowing one to easily predict load power and energy for a variety of system designs. The authors show a number of sample calculations from the model with corresponding simulation results for comparison.« less
{"title":"Pic simulation And Analytic modelling Of both Long and Short-pulse Magnetically Insulated Transmission Lines","authors":"S. Rosenthal, C. Mendel","doi":"10.1109/PLASMA.1994.588942","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588942","url":null,"abstract":"It is crucial to have appropriate tools for MITL design. This need is emphasized by the number of new pulsed power accelerators presently in the feasibility-study and design stages. MITL systems are essential components of most of these accelerators. MITLs are typically modeled by Telegrapher`s equations that treat electrons only through a voltage and current-dependent loss front current. The electron flow behind the loss front in a MITL system must also be included adequately in a model if it is to accurately determine the power and energy available to the load of a MITL. Often electromagnetic, relativistic PIC simulations must be done to characterize specific MITL designs. However, rather than concentrate on simulations of a specific geometry, they have recently done ensembles of simulations of generic MITL systems and have found patterns in the results that validate the use of a generalized set of Telegrapher`s equations which include electron flow. The fit to this pattern provides the value of a parameter, determined by the electron dynamics, used in the model. The simulations have also demonstrated features whose assumption makes the analytic model very simple to implement. One of these simplifying assumptions is that the flow impedance is essentially constant, nearlymore » independent of load impedance even in a short line. The new modeling equations should prove useful for the accurate characterization of MITLs, allowing one to easily predict load power and energy for a variety of system designs. The authors show a number of sample calculations from the model with corresponding simulation results for comparison.« less","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127229364","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.589009
C. Brooks, M. Brake, R.M. Gilgenback
{"title":"Properties Of Argon-lithium Diacharges In A Microwave Resonant Cavity","authors":"C. Brooks, M. Brake, R.M. Gilgenback","doi":"10.1109/PLASMA.1994.589009","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589009","url":null,"abstract":"","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127326652","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.588832
I. Girka
{"title":"Surface Magnetoplasma Waves In The Rectangular Cross- Sectional Metallic Waveguide With Uniform Plasma Fillng","authors":"I. Girka","doi":"10.1109/PLASMA.1994.588832","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588832","url":null,"abstract":"","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123448984","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.588765
P. Rothwell, M. Silevitch, L. Block, C-G. Fiilthammar
The equations of motion are solved for ions moving in a model electric field which corresponds to the nightside equatorial region of the magnetosphere. Features of the substorm onset such as its association with the Harang discontinuity (HD), the presence of enhanced 0' in the plasma sheet, the creation of a substorm current wedge, and the local weakening of the magnetic field are treated. The divergence of inertia currents carried by the oxygen ions at thc HD rcquircs thc formation of a substorm current wedge. A spontaneous onset occurs where the current wedge is driven to the point when sufficient east-west current is diverted to the ionosphere. A triggered onset occurs when IMFB, turns from south to north causing the cross-tail electric field to pass through zero. Under those conditions an analytic treatment in terms of elliptic functions shows that the ions may go chaotic thereby producing a current interruption.
{"title":"Substorm Onsets And Single Ion Motion","authors":"P. Rothwell, M. Silevitch, L. Block, C-G. Fiilthammar","doi":"10.1109/PLASMA.1994.588765","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588765","url":null,"abstract":"The equations of motion are solved for ions moving in a model electric field which corresponds to the nightside equatorial region of the magnetosphere. Features of the substorm onset such as its association with the Harang discontinuity (HD), the presence of enhanced 0' in the plasma sheet, the creation of a substorm current wedge, and the local weakening of the magnetic field are treated. The divergence of inertia currents carried by the oxygen ions at thc HD rcquircs thc formation of a substorm current wedge. A spontaneous onset occurs where the current wedge is driven to the point when sufficient east-west current is diverted to the ionosphere. A triggered onset occurs when IMFB, turns from south to north causing the cross-tail electric field to pass through zero. Under those conditions an analytic treatment in terms of elliptic functions shows that the ions may go chaotic thereby producing a current interruption.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115107522","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.589064
M. Walter, R. Gilgenbach, J. Hochman, T. Spencer
Experiments have been performed to investigate the effects of tapered magnetic fields on the high power microwave emission from the gyrotron-backward-wave-oscillator (gyro-BWO). Tapering trimcoils have been utilized to compare gyro-BWO microwave emission for uniform versus tapered magnetic fields in the range of {Delta}B/B{sub 0} = 10--15%, where B{sub 0} = 4--6 kG. These magnetic tapering experiments employed a TE{sub 11} mode at tunable-frequency of 4.5--6 GHz, with a uniform interaction tube radius. Initial experimental results show that the peak microwave power and integrated energy are nearly the same for the uniform magnetic field, compared to the 11% downtapered B field. Uptapered magnetic fields ({approximately}15%) gave lower powers and energies. MAGIC code simulations have been run for the gyro-BWO with a scaled TE{sub 01} mode to model various magnetic tapering magnitudes and both directions. Future gyro-BWO experiments will combine tapered tube radius with magnetic tapering to optimize microwave emission power, pulselength, and energy.
{"title":"Magnetic Tapering Of Intense E-beam, Long-pulse Gyro-bwos","authors":"M. Walter, R. Gilgenbach, J. Hochman, T. Spencer","doi":"10.1109/PLASMA.1994.589064","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589064","url":null,"abstract":"Experiments have been performed to investigate the effects of tapered magnetic fields on the high power microwave emission from the gyrotron-backward-wave-oscillator (gyro-BWO). Tapering trimcoils have been utilized to compare gyro-BWO microwave emission for uniform versus tapered magnetic fields in the range of {Delta}B/B{sub 0} = 10--15%, where B{sub 0} = 4--6 kG. These magnetic tapering experiments employed a TE{sub 11} mode at tunable-frequency of 4.5--6 GHz, with a uniform interaction tube radius. Initial experimental results show that the peak microwave power and integrated energy are nearly the same for the uniform magnetic field, compared to the 11% downtapered B field. Uptapered magnetic fields ({approximately}15%) gave lower powers and energies. MAGIC code simulations have been run for the gyro-BWO with a scaled TE{sub 01} mode to model various magnetic tapering magnitudes and both directions. Future gyro-BWO experiments will combine tapered tube radius with magnetic tapering to optimize microwave emission power, pulselength, and energy.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116227340","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 : 1994-06-06DOI: 10.1109/PLASMA.1994.589146
K. Eppley
{"title":"Two And Three Dimensional Simulation Of Disk-loaded Travelling-wave Output Structures For High-power Klystrons","authors":"K. Eppley","doi":"10.1109/PLASMA.1994.589146","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589146","url":null,"abstract":"","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122390170","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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