Pub Date : 1994-06-06DOI: 10.1109/PLASMA.1994.588965
J. Davis, J. Guiliani, M. Mulbrandon
{"title":"Influence Of L-shell Dynamics On K-shell X-rays From A Krypton Gas Puff Z-pinch Plasma","authors":"J. Davis, J. Guiliani, M. Mulbrandon","doi":"10.1109/PLASMA.1994.588965","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588965","url":null,"abstract":"","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"32 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":"116656988","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.1994.588916
G. Peterson, N. Rostoker
Imploded, annular z-pinches are always subject to the Rayleigh-Taylor instability, the growth of which is determined by the initial perturbations and the linear growth rate {gamma} = {radical}gk where g is the acceleration and k is the wave number. By imparting a spin to the plasma, the initial perturbations can be greatly reduced. Furthermore, the centripetal acceleration will reduce the growth rates at the end of the implosion. This idea could benefit pinch schemes that require uniform compressions, such as x-ray laser and fusion programs that are based on staged pinches and pinches with trapped magnetic fields. A summary of the spin concept is presented along with a zero-dimension implosion analysis for pinches with imparted spins and trapped magnetic fields.
{"title":"Spin control of The rayleigh-taylor Instability In a dense z-pinch","authors":"G. Peterson, N. Rostoker","doi":"10.1109/PLASMA.1994.588916","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588916","url":null,"abstract":"Imploded, annular z-pinches are always subject to the Rayleigh-Taylor instability, the growth of which is determined by the initial perturbations and the linear growth rate {gamma} = {radical}gk where g is the acceleration and k is the wave number. By imparting a spin to the plasma, the initial perturbations can be greatly reduced. Furthermore, the centripetal acceleration will reduce the growth rates at the end of the implosion. This idea could benefit pinch schemes that require uniform compressions, such as x-ray laser and fusion programs that are based on staged pinches and pinches with trapped magnetic fields. A summary of the spin concept is presented along with a zero-dimension implosion analysis for pinches with imparted spins and trapped magnetic fields.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"97 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":"121769540","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.1994.588727
O. Bolin, N. Brenning
{"title":"Two-dimensional Particle Simulations Of The Low Frequency Electric Fields In Ionospheric Injection Experiments","authors":"O. Bolin, N. Brenning","doi":"10.1109/PLASMA.1994.588727","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588727","url":null,"abstract":"","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":"122104931","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.1994.589071
J. E. Beers
High power microwave tubes require well focussed high energy electron beams High frequencies cause the r-f interaction with the beam to concentrate in the outer edge of the beam making the center relatively unimportant The Magnetron Injection Gun (MIG) uses a truncated cone for a cathode and an axial magnetic field to concentrate the electron current in an annulus eliminating the current in the center of the beam High power microwave tubes used for r f plasma generation, and for accelerators require these high current relativistic beams A theoretical study of Relativistic MIG's has been carried out using PBGUNS', a digital program for the Poisson simulation of particle beams The simulations show that there are two types of guns that need to be considered those with cathodes that are short axially compared with their mean radius from the axis and those whose length are comparable to or longer than the mean radius Short cathodes are dominated by the axial end conditions which need to be close to the Pierce angle (67 5 degrees) but are little effected by the shape of the accelerating electrode The longer cathodes are critically dependent on both the end conditions and the accelerating electrode One or two transition regions are needed, one to transporl the beam to its final diameter and a second to turn it axially in such a way that it does not ripple excessively before it reaches the front of the cathode, but can be relieved by reducing the magnetic field so that the electrons rise well above the cathode Longer cathodes can also be stabilized by using larger cone angles Cone half angles of less than 15 degrees tend to be more unstable The longer the cathode and the higher the current the greater the difficulty in forming a transportable, compressed beam Several examples will be presented
{"title":"Computer Simulations Of Relativistic Mlg's With Magnetically Compressed Beams For High Power Microwave Tubes","authors":"J. E. Beers","doi":"10.1109/PLASMA.1994.589071","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589071","url":null,"abstract":"High power microwave tubes require well focussed high energy electron beams High frequencies cause the r-f interaction with the beam to concentrate in the outer edge of the beam making the center relatively unimportant The Magnetron Injection Gun (MIG) uses a truncated cone for a cathode and an axial magnetic field to concentrate the electron current in an annulus eliminating the current in the center of the beam High power microwave tubes used for r f plasma generation, and for accelerators require these high current relativistic beams A theoretical study of Relativistic MIG's has been carried out using PBGUNS', a digital program for the Poisson simulation of particle beams The simulations show that there are two types of guns that need to be considered those with cathodes that are short axially compared with their mean radius from the axis and those whose length are comparable to or longer than the mean radius Short cathodes are dominated by the axial end conditions which need to be close to the Pierce angle (67 5 degrees) but are little effected by the shape of the accelerating electrode The longer cathodes are critically dependent on both the end conditions and the accelerating electrode One or two transition regions are needed, one to transporl the beam to its final diameter and a second to turn it axially in such a way that it does not ripple excessively before it reaches the front of the cathode, but can be relieved by reducing the magnetic field so that the electrons rise well above the cathode Longer cathodes can also be stabilized by using larger cone angles Cone half angles of less than 15 degrees tend to be more unstable The longer the cathode and the higher the current the greater the difficulty in forming a transportable, compressed beam Several examples will be presented","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"149 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":"124159606","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.1994.588960
S. Kuo, A. Ren
Recently, theory, computer simulation and experiment have demonstrated that the frequency of an electromagnetic (EM) wave interacting with a rapidly created plasma is upshifted. The interest in frequency upshifting phenomenon can be attributed to its many potential applications including the enhancement of the frequency tuning capability of existing sources of EM waves and improvement of the performance of high-power radar and direct energy systems by enabling reflectionless propagation of very powerful microwave pulses through the air, etc. Moreover, there are no technical difficulties in producing dense plasma rapidly. It was observed, however, that in some experiments a frequency downshift also exists. Since the created plasma decayed much slower than its growth and since the frequency downshift lines did not appear in the results of computer simulations using a lossless unmagnetized plasma model, the frequency downshift phenomenon has not been discussed. In this work, experimental evidence and theory is presented for the simultaneous creation of a downshifted wave. There is excellent agreement between experimental results and computer simulation based on a simple theory.
{"title":"Frequency Downshift In Rapidly Ionizing Media","authors":"S. Kuo, A. Ren","doi":"10.1109/PLASMA.1994.588960","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588960","url":null,"abstract":"Recently, theory, computer simulation and experiment have demonstrated that the frequency of an electromagnetic (EM) wave interacting with a rapidly created plasma is upshifted. The interest in frequency upshifting phenomenon can be attributed to its many potential applications including the enhancement of the frequency tuning capability of existing sources of EM waves and improvement of the performance of high-power radar and direct energy systems by enabling reflectionless propagation of very powerful microwave pulses through the air, etc. Moreover, there are no technical difficulties in producing dense plasma rapidly. It was observed, however, that in some experiments a frequency downshift also exists. Since the created plasma decayed much slower than its growth and since the frequency downshift lines did not appear in the results of computer simulations using a lossless unmagnetized plasma model, the frequency downshift phenomenon has not been discussed. In this work, experimental evidence and theory is presented for the simultaneous creation of a downshifted wave. There is excellent agreement between experimental results and computer simulation based on a simple theory.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"48 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":"123247465","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.1994.588745
G. Lapenta, J. Brackbill
complexity of the structure. So far, several numerical models have been reported concerning the EM models of ICPS[’]. The numerical solutions could not describe the physical insight of EM fields and a considerable amount of consumed CPU time could have been expected. We used the Mode Analysis Technique (MAT) to obtain a closedform solution, which provided the behaviors of each mode excited in the ICPS and the relationship between eigenmodes and the reactor geometry.
{"title":"Fluid PIC Simulation Of Plasma Processing Devices","authors":"G. Lapenta, J. Brackbill","doi":"10.1109/PLASMA.1994.588745","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588745","url":null,"abstract":"complexity of the structure. So far, several numerical models have been reported concerning the EM models of ICPS[’]. The numerical solutions could not describe the physical insight of EM fields and a considerable amount of consumed CPU time could have been expected. We used the Mode Analysis Technique (MAT) to obtain a closedform solution, which provided the behaviors of each mode excited in the ICPS and the relationship between eigenmodes and the reactor geometry.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"52 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":"123267893","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.1994.589081
G. Shvets, J. Wurtele
Theoretical analysis of the free-electron laser Green`s function has been made in two very distinct operating regimes. An analytic expression for the temporal Green`s function has been found for the strongly space-charge dominated (Raman) regime for a single pass FEL amplifier. The expression is shown to reduce to the expected steady-state result when the initial system parameters are time-independent. Frequency shifting is seen to arise from slippage and finite length electromagnetic pulses, as well as from better known causes such as variations in the beam energy and voltage. An explicit criterion for using the local gain approximation is presented. A new formalism for analyzing the temporal and spectral evolution in an oscillator is developed. Variations in both the beam and radiation profiles are included in the analysis. An exact expression for the Green`s function of the n`th pass in an oscillator is derived and can be explicitly evaluated using a fast numerical algorithm. The algorithm yields the n`th pass Green`s function directly, without requiring calculation of the Green`s function at previous passes. The calculation does not involve non-causal truncations utilized in supermode theory.
{"title":"Green's Function Analysis of Free-electron Laser Amplifiers ;nd Oscillators","authors":"G. Shvets, J. Wurtele","doi":"10.1109/PLASMA.1994.589081","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589081","url":null,"abstract":"Theoretical analysis of the free-electron laser Green`s function has been made in two very distinct operating regimes. An analytic expression for the temporal Green`s function has been found for the strongly space-charge dominated (Raman) regime for a single pass FEL amplifier. The expression is shown to reduce to the expected steady-state result when the initial system parameters are time-independent. Frequency shifting is seen to arise from slippage and finite length electromagnetic pulses, as well as from better known causes such as variations in the beam energy and voltage. An explicit criterion for using the local gain approximation is presented. A new formalism for analyzing the temporal and spectral evolution in an oscillator is developed. Variations in both the beam and radiation profiles are included in the analysis. An exact expression for the Green`s function of the n`th pass in an oscillator is derived and can be explicitly evaluated using a fast numerical algorithm. The algorithm yields the n`th pass Green`s function directly, without requiring calculation of the Green`s function at previous passes. The calculation does not involve non-causal truncations utilized in supermode theory.","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"98 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":"124923513","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.1994.589127
H. Hwang, P. Ventzek, R. Hoekstra, M. J. Kusbner
{"title":"Transport Of Dust Particles In Inductively Coupled Discharges","authors":"H. Hwang, P. Ventzek, R. Hoekstra, M. J. Kusbner","doi":"10.1109/PLASMA.1994.589127","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589127","url":null,"abstract":"","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"48 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":"121714133","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.1994.588793
N. Hershkowitz, J. Ding, J. Jenq
{"title":"Chemical Etching Of SiO/sub 2/ By CF/sub 4/ At Low Pressure- Does It Really Depend On The Plasma Chemistry?","authors":"N. Hershkowitz, J. Ding, J. Jenq","doi":"10.1109/PLASMA.1994.588793","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.588793","url":null,"abstract":"","PeriodicalId":254741,"journal":{"name":"Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)","volume":"74 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":"131068763","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.1994.589036
N. Sternberg, V. Godyak
of 2 95% for large size problems. The particle pash time achieved is 115 nsecs/particle/time step for 162 mdlion particles on 512 nodes. Comparing with the performance on a single processor Cray C90, this represents a factor of 58 speedup. The code uses a finite-difference leap frog method for field solve which is significantly more efficient than fast Fourier transforms on parallel computers. The performance of this code on the 128 node Cray T3D will also be discussed.
{"title":"Approximation Of The Bounded Plasma Model By The Plasma And The Sheath Models","authors":"N. Sternberg, V. Godyak","doi":"10.1109/PLASMA.1994.589036","DOIUrl":"https://doi.org/10.1109/PLASMA.1994.589036","url":null,"abstract":"of 2 95% for large size problems. The particle pash time achieved is 115 nsecs/particle/time step for 162 mdlion particles on 512 nodes. Comparing with the performance on a single processor Cray C90, this represents a factor of 58 speedup. The code uses a finite-difference leap frog method for field solve which is significantly more efficient than fast Fourier transforms on parallel computers. The performance of this code on the 128 node Cray T3D will also be discussed.","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":"129580185","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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