K. Takaki, K. Iinanishi, S. Mukaigawa, T. Fujiwara, Y. Suda, K. Yukimura
Summary form only given. Plasma-based ion implantation and deposition (PBII&D) technology is a promising method for improving surface properties of three-dimensional substrates as a workpiece without a complicated manipulation system. A shunting arc is a convenient pulsed plasma source of metals and semi-metals. In this study, a carbon-shunting arc discharge is generated in nitrogen gas circumstance and amorphous carbon nitride (a-CNx) films are prepared using the plasma. In the experiment, a self-magnetically accelerating system is employed to improve deposition rate. A carbon rod with a diameter of 2 mm and a length of 40 mm is held vertically between a pair of carbon electrodes. A 20 muF-capacitor bank is used to ignite a shunting arc. The carbon film is prepared on a disk target with 80 mm-diameter and 10 mm-thickness is positioned at 100 mm from the rod as an arc source. Silicon substrates are pasted on the disk target and a series of pulse voltage is applied to Si substrate synchronizing with ignition of the shunting arc with a peak current of 1.7 kA. The ambient nitrogen gas pressure is varied from 2times10-2 to 300 Pa. The shunting arc plasma is successfully produced and is accelerated along carbon rails. The heating energy to generate the shunting arc has minimum value for variation of the gas pressure. A spectroscopic measurement of the plasma shows that the produced plasma contains nitrogen particles in ambient nitrogen gas circumstance. X-ray photoelectron spectroscopy analysis shows that the energy at which the C (1s) peak shifts from the binding energy (BE) of C-C to that of sp2C-N and sp3C-N by injecting nitrogen gas. The peak in the N (1s) spectrum also appears around BE of N-sp3C and N-sp2C with the nitrogen injection. The N/C ratio of the film is obtained to be 0.35 at 2 Pa gas pressure.
{"title":"Production of nitrogen-containing carbon plasma using shunting arc discharge for carbon nitride films preparation","authors":"K. Takaki, K. Iinanishi, S. Mukaigawa, T. Fujiwara, Y. Suda, K. Yukimura","doi":"10.1002/PSSA.200778341","DOIUrl":"https://doi.org/10.1002/PSSA.200778341","url":null,"abstract":"Summary form only given. Plasma-based ion implantation and deposition (PBII&D) technology is a promising method for improving surface properties of three-dimensional substrates as a workpiece without a complicated manipulation system. A shunting arc is a convenient pulsed plasma source of metals and semi-metals. In this study, a carbon-shunting arc discharge is generated in nitrogen gas circumstance and amorphous carbon nitride (a-CNx) films are prepared using the plasma. In the experiment, a self-magnetically accelerating system is employed to improve deposition rate. A carbon rod with a diameter of 2 mm and a length of 40 mm is held vertically between a pair of carbon electrodes. A 20 muF-capacitor bank is used to ignite a shunting arc. The carbon film is prepared on a disk target with 80 mm-diameter and 10 mm-thickness is positioned at 100 mm from the rod as an arc source. Silicon substrates are pasted on the disk target and a series of pulse voltage is applied to Si substrate synchronizing with ignition of the shunting arc with a peak current of 1.7 kA. The ambient nitrogen gas pressure is varied from 2times10-2 to 300 Pa. The shunting arc plasma is successfully produced and is accelerated along carbon rails. The heating energy to generate the shunting arc has minimum value for variation of the gas pressure. A spectroscopic measurement of the plasma shows that the produced plasma contains nitrogen particles in ambient nitrogen gas circumstance. X-ray photoelectron spectroscopy analysis shows that the energy at which the C (1s) peak shifts from the binding energy (BE) of C-C to that of sp2C-N and sp3C-N by injecting nitrogen gas. The peak in the N (1s) spectrum also appears around BE of N-sp3C and N-sp2C with the nitrogen injection. The N/C ratio of the film is obtained to be 0.35 at 2 Pa gas pressure.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124653703","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 : 2007-10-15DOI: 10.1109/PPPS.2007.4345984
P. Šunka, V. Stelmashuk, J. Beneš, P. Poučková, J. Kralova
A generator of two successive shock waves focused to a common focal point-tandem shocks is developed. To investigate the effect of shock waves on living cells, suspension of melanoma B16 cells has been exposed to 600 and 1200 of tandem shocks with a fix time interval between them of 10 mus. Microscopic investigation revealed that even small number of shocks (90, 190) results in perforation of the cell membranes, which could lead to the facilitated chemotherapeutic drug penetration into targeted tumor cells.
{"title":"Potential Applications of Tandem Shock Waves in Cancer Treatment","authors":"P. Šunka, V. Stelmashuk, J. Beneš, P. Poučková, J. Kralova","doi":"10.1109/PPPS.2007.4345984","DOIUrl":"https://doi.org/10.1109/PPPS.2007.4345984","url":null,"abstract":"A generator of two successive shock waves focused to a common focal point-tandem shocks is developed. To investigate the effect of shock waves on living cells, suspension of melanoma B16 cells has been exposed to 600 and 1200 of tandem shocks with a fix time interval between them of 10 mus. Microscopic investigation revealed that even small number of shocks (90, 190) results in perforation of the cell membranes, which could lead to the facilitated chemotherapeutic drug penetration into targeted tumor cells.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130026780","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 : 2007-10-15DOI: 10.1109/PPPS.2007.4345802
H. Lee, J. Seon
Summary form only given. The acceleration channel of a plasma thruster utilizing Hall effect has been numerically simulated by using an axisymmetric two-dimensional (r,z) particle-in-cell (PIC) model with Monte-Carlo collision (MCC) method. The dynamics of electrons and ions are treated with PIC method with the time scale of electrons in order to investigate the particle transport and to calculate the specific impulse. The charged particles are coupled with Poisson's equation. Xe neutrals are injected from the inside of the anode and experience elastic, excitation, and ionization collisions with electrons and are scattered by ions. These collisions are simulated by using an MCC model. As the ionization rate is enough high to affect the density profile of neutrals, the dynamics of neutral gas is also simulated by using fluid model. This is more realistic than the previous simulations for Hall thruster. The nonuniformity of the neutral density profile plays an important role in the dynamics of charged particles. The effect of secondary electron emission at the dielectric wall is also considered in this model.
{"title":"Two-Dimensional Particle-in-Cell Simulation of a Hall Thruster","authors":"H. Lee, J. Seon","doi":"10.1109/PPPS.2007.4345802","DOIUrl":"https://doi.org/10.1109/PPPS.2007.4345802","url":null,"abstract":"Summary form only given. The acceleration channel of a plasma thruster utilizing Hall effect has been numerically simulated by using an axisymmetric two-dimensional (r,z) particle-in-cell (PIC) model with Monte-Carlo collision (MCC) method. The dynamics of electrons and ions are treated with PIC method with the time scale of electrons in order to investigate the particle transport and to calculate the specific impulse. The charged particles are coupled with Poisson's equation. Xe neutrals are injected from the inside of the anode and experience elastic, excitation, and ionization collisions with electrons and are scattered by ions. These collisions are simulated by using an MCC model. As the ionization rate is enough high to affect the density profile of neutrals, the dynamics of neutral gas is also simulated by using fluid model. This is more realistic than the previous simulations for Hall thruster. The nonuniformity of the neutral density profile plays an important role in the dynamics of charged particles. The effect of secondary electron emission at the dielectric wall is also considered in this model.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"43 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132364708","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 : 2007-10-15DOI: 10.1109/PPPS.2007.4345905
C. Myers, P. Schrafel, D. Chalenski, B. Kusse
Summary form only given. When single wires are driven with short, high-current pulses the energy deposited is terminated by a voltage collapse that occurs when coronal plasma forms along the wire. It has been shown that the formation of this plasma and the amount of energy deposited can be affected by the way electrical contact is established between a wire and the electrodes. It has also been shown that soldered contacts or improved mechanical contacts can delay the plasma formation and increase the energy deposited. We present here more detailed experiments using a new approach for improving the electrical connection between the wires and electrodes. Large diameter, 50 mum, 5056 aluminum wires were chemically etched down to 25 mum except for regions at the ends where the wire-electrode contact occurred. Initial wire diameters were determined and placement between the electrodes was adjusted using diffraction techniques. Care was taken so that the extension of the thicker portion of the wires into the anode-cathode gap region was minimized. Energy deposited before voltage collapse using these types of wires was compared to the energy deposited in uniform diameter 25 mum wires with simple mechanical electrode contacts and also with 25 mum wires using soldered contacts. Similar experiments are planned starting with larger wires of, for example 75 and 100 mum. Detailed time dependent measurements of the plasma at the ends of the wires, near the electrodes, was made using 532 nm laser interferometry. Time dependent laser backlighting was used to observe the wire expansion after the voltage collapse.
{"title":"Single Wire Electrode Contacts ABD their Effects on Energy Deposition","authors":"C. Myers, P. Schrafel, D. Chalenski, B. Kusse","doi":"10.1109/PPPS.2007.4345905","DOIUrl":"https://doi.org/10.1109/PPPS.2007.4345905","url":null,"abstract":"Summary form only given. When single wires are driven with short, high-current pulses the energy deposited is terminated by a voltage collapse that occurs when coronal plasma forms along the wire. It has been shown that the formation of this plasma and the amount of energy deposited can be affected by the way electrical contact is established between a wire and the electrodes. It has also been shown that soldered contacts or improved mechanical contacts can delay the plasma formation and increase the energy deposited. We present here more detailed experiments using a new approach for improving the electrical connection between the wires and electrodes. Large diameter, 50 mum, 5056 aluminum wires were chemically etched down to 25 mum except for regions at the ends where the wire-electrode contact occurred. Initial wire diameters were determined and placement between the electrodes was adjusted using diffraction techniques. Care was taken so that the extension of the thicker portion of the wires into the anode-cathode gap region was minimized. Energy deposited before voltage collapse using these types of wires was compared to the energy deposited in uniform diameter 25 mum wires with simple mechanical electrode contacts and also with 25 mum wires using soldered contacts. Similar experiments are planned starting with larger wires of, for example 75 and 100 mum. Detailed time dependent measurements of the plasma at the ends of the wires, near the electrodes, was made using 532 nm laser interferometry. Time dependent laser backlighting was used to observe the wire expansion after the voltage collapse.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131182399","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 : 2007-10-15DOI: 10.1109/PPPS.2007.4345862
C. Lynn, A. Neuber, J. Dickens
Summary form only given. The feasibility of utilizing shock loaded and unloaded dielectrics as a true closing/opening switch as part of an explosive-driven pulse power system is addressed. While it is known that shock wave compressed PVC and PMMA become conductive, the details of the material's recovery from the conducting back to the insulating state are much less known. To be effective as an opening switch, the recovery time has to be minimized, i.e., for instance, heating of the material must be minimized. The two primary sources of heat in the switch are shock induced heating and switch loss heating. These sources must be balanced for optimal results. Furthermore, it is also important to determine if the observed temporal behavior is due to finite shock unloading or intrinsic material relaxation properties. In the extreme case, bulk breakdown may occur during recovery as voltage increases across the switch. Previous work, performed primarily with a C-4 packed compression rod, has achieved a switch on-state resistance of less than 1 ohm, with an average on-state duration of 80 microseconds. It was also shown that PMMA appears to have a much sharper transition time than PVC, between both insulator to conductor, and conductor to insulator. The results presented here use a timed explosion to more carefully control the intensity and duration of the shock wave. This allows for more control over shock induced heating of the sample. We will present recent experimental data and discuss results as they relate to the development of an opening switch.
{"title":"Opening Switch Utilizing Shock Wave Induced Conduction in PMMA and PVC","authors":"C. Lynn, A. Neuber, J. Dickens","doi":"10.1109/PPPS.2007.4345862","DOIUrl":"https://doi.org/10.1109/PPPS.2007.4345862","url":null,"abstract":"Summary form only given. The feasibility of utilizing shock loaded and unloaded dielectrics as a true closing/opening switch as part of an explosive-driven pulse power system is addressed. While it is known that shock wave compressed PVC and PMMA become conductive, the details of the material's recovery from the conducting back to the insulating state are much less known. To be effective as an opening switch, the recovery time has to be minimized, i.e., for instance, heating of the material must be minimized. The two primary sources of heat in the switch are shock induced heating and switch loss heating. These sources must be balanced for optimal results. Furthermore, it is also important to determine if the observed temporal behavior is due to finite shock unloading or intrinsic material relaxation properties. In the extreme case, bulk breakdown may occur during recovery as voltage increases across the switch. Previous work, performed primarily with a C-4 packed compression rod, has achieved a switch on-state resistance of less than 1 ohm, with an average on-state duration of 80 microseconds. It was also shown that PMMA appears to have a much sharper transition time than PVC, between both insulator to conductor, and conductor to insulator. The results presented here use a timed explosion to more carefully control the intensity and duration of the shock wave. This allows for more control over shock induced heating of the sample. We will present recent experimental data and discuss results as they relate to the development of an opening switch.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115352046","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 : 2007-10-15DOI: 10.1109/PPPS.2007.4346263
D. Bliss, M. Cuneo, B. Jones, K. W. Starve, W. Stygar, E. Waisman, S. Chantrenne
Summary form only given. We present experimental observations of the closure of the power feed gap on the Z machine during the implosion of a wire array load. The cathode surface and wire array edge were imaged by time-resolved laser shadowgraphy and X-ray backlighting. During the run in phase of the wire array which lasts through maximum current, ~20 MA, the radial and axial power-flow surfaces of the cathode expanded < frac14 mm. In contrast, after peak X-ray emission, the radial power-flow surface expanded at a velocity of 4.8 times 104 m/s as observed by laser shadowgraphy. Assuming both anode and cathode power-flow surfaces expand with similar velocities, the extrapolated time to close a 4 mm gap is ~40 ns. Previous gap closure experiments indicated closure times less than this. Therefore a low density, low gradient plasma must be responsible for shorting the gap at earlier times. The high density plasma serves as a moving surface and source of ions.
{"title":"The Dynamics of Radiation Driven Gap Closure Across Megagauss Fields on Z","authors":"D. Bliss, M. Cuneo, B. Jones, K. W. Starve, W. Stygar, E. Waisman, S. Chantrenne","doi":"10.1109/PPPS.2007.4346263","DOIUrl":"https://doi.org/10.1109/PPPS.2007.4346263","url":null,"abstract":"Summary form only given. We present experimental observations of the closure of the power feed gap on the Z machine during the implosion of a wire array load. The cathode surface and wire array edge were imaged by time-resolved laser shadowgraphy and X-ray backlighting. During the run in phase of the wire array which lasts through maximum current, ~20 MA, the radial and axial power-flow surfaces of the cathode expanded < frac14 mm. In contrast, after peak X-ray emission, the radial power-flow surface expanded at a velocity of 4.8 times 104 m/s as observed by laser shadowgraphy. Assuming both anode and cathode power-flow surfaces expand with similar velocities, the extrapolated time to close a 4 mm gap is ~40 ns. Previous gap closure experiments indicated closure times less than this. Therefore a low density, low gradient plasma must be responsible for shorting the gap at earlier times. The high density plasma serves as a moving surface and source of ions.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125580670","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 : 2007-10-01DOI: 10.1109/CEIDP.2007.4451506
R. Joshi, G. Zhao, H. Hjalmarson
Summary form only given. Zinc oxide varistors are ceramic devices made by sintering ZnO powder together with small amounts of other additives such as Bi2O3, MnO2, Co3O4 etc... The presence of Bi-ions trapped at the grain-boundaries are thought to be responsible for a highly nonlinear behavior. The nonlinear current-voltage (I-V) characteristics and excellent energy absorption capabilities, make ZnO varistors very useful as electrical surge arresters. We present a coupled electro-thermal analyses to determine the voltage driven temperature increases and possible impact on material failure in a ZnO varistor. A two-dimensional, random Voronoi network model has been used. The inherently non-linear internal I-V characteristics have been included. A stochastic distribution of grains with varying sizes and barrier breakdown voltages has also been taken into account. The model is time-dependent and includes two-dimensional heat generation and flow. Issues relating to internal heating analyses, time-dependent localized melting, cracking due to thermal stresses, and dynamical evolution towards failure, are addressed. Our results show that application of high voltage pulses can lead to internal ZnO melting. Such phase change is known to permanently damage the non-linear GB chracter associated with the Bi2O3 present in such material. Comparisons between uniform and normally distributed barrier voltages were made. Physically, it was shown that differences would be associated would depend on grain size and the applied bias regime. It has also been shown that reduction in grain size would help lower the maximum internal stress. This is thus a desirable feature, and would also work to enhance the hold-off voltage for a given sample size.
{"title":"Electro-Thermal Simulation Studies for Pulsed Voltage Energy Absorption and Potential Failure in Microstructured ZnO Varistors","authors":"R. Joshi, G. Zhao, H. Hjalmarson","doi":"10.1109/CEIDP.2007.4451506","DOIUrl":"https://doi.org/10.1109/CEIDP.2007.4451506","url":null,"abstract":"Summary form only given. Zinc oxide varistors are ceramic devices made by sintering ZnO powder together with small amounts of other additives such as Bi2O3, MnO2, Co3O4 etc... The presence of Bi-ions trapped at the grain-boundaries are thought to be responsible for a highly nonlinear behavior. The nonlinear current-voltage (I-V) characteristics and excellent energy absorption capabilities, make ZnO varistors very useful as electrical surge arresters. We present a coupled electro-thermal analyses to determine the voltage driven temperature increases and possible impact on material failure in a ZnO varistor. A two-dimensional, random Voronoi network model has been used. The inherently non-linear internal I-V characteristics have been included. A stochastic distribution of grains with varying sizes and barrier breakdown voltages has also been taken into account. The model is time-dependent and includes two-dimensional heat generation and flow. Issues relating to internal heating analyses, time-dependent localized melting, cracking due to thermal stresses, and dynamical evolution towards failure, are addressed. Our results show that application of high voltage pulses can lead to internal ZnO melting. Such phase change is known to permanently damage the non-linear GB chracter associated with the Bi2O3 present in such material. Comparisons between uniform and normally distributed barrier voltages were made. Physically, it was shown that differences would be associated would depend on grain size and the applied bias regime. It has also been shown that reduction in grain size would help lower the maximum internal stress. This is thus a desirable feature, and would also work to enhance the hold-off voltage for a given sample size.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"430 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132725025","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}
Summary form only given. Chemical oxygen-iodine lasers (COILs) achieve oscillation on the 2P1/2rarr2P3/2 transition of atomic iodine at 1.315 mum by a series of excitation transfers from O2(1Delta). In electrically excited COILs, (eCOILs) the O2(1Delta) is produced in a flowing plasma, typically He/O2, at a few to tens of Torr. Many svstem issues motivate operating eCOILs at higher pressures to obtain larger absolute densities of O2(1Delta) for a given yield and provide higher back pressure for expansion. Obtaining high yields of O2(1Delta) will require careful management of the ozone density [a quencher of O2(1Delta)], gas temperature and discharge stability. In this paper, we discuss results from a computational investigation of O2(1Delta) production in flowing plasmas sustained at moderate pressures (< 50-100 Torr). This investigation was conducted using plug-flow and 2-dimensional models. In this study, we scaled power deposition and flow rates such that if there are not second order effects, yield should be constant and absolute O2(1Delta) production should scale linearly with pressure. We found in many cases that absolute O2(1Delta) production scaled sub-linearly with pressure. Ground state and vibrationally excited ozone are found to be one of the major quenchers of O2(1Delta) and the production of O3 is a sensitive function of pressure. Gas heating per molecule increases at high pressures due to exothermic 3-body reactions which reduces O3 production, increases O3 destruction and, for certain conditions, restores yields. With increasing pressure and increasing absolute densities of atomic oxygen and pooling reactions of O2(1Delta), quenching by these species can become important in the afterglow. The yield of O2(1Delta) is also determined by discharge stability. For the geometries we investigated, discharge constriction becomes problematic at higher pressures, thereby reducing yields.
{"title":"O2(1Δ) production in high pressure flowing He/O2 plasmas: scaling and quenching","authors":"N. Babaeva, M. Kushner, R. A. Arakoni","doi":"10.1063/1.2743878","DOIUrl":"https://doi.org/10.1063/1.2743878","url":null,"abstract":"Summary form only given. Chemical oxygen-iodine lasers (COILs) achieve oscillation on the <sup>2</sup>P<sub>1/2</sub>rarr<sup>2</sup>P<sub>3/2</sub> transition of atomic iodine at 1.315 mum by a series of excitation transfers from O<sub>2</sub>(<sup>1</sup>Delta). In electrically excited COILs, (eCOILs) the O<sub>2</sub>(<sup>1</sup>Delta) is produced in a flowing plasma, typically He/O<sub>2</sub>, at a few to tens of Torr. Many svstem issues motivate operating eCOILs at higher pressures to obtain larger absolute densities of O<sub>2</sub>(<sup>1</sup>Delta) for a given yield and provide higher back pressure for expansion. Obtaining high yields of O<sub>2</sub>(<sup>1</sup>Delta) will require careful management of the ozone density [a quencher of O<sub>2</sub>(<sup>1</sup>Delta)], gas temperature and discharge stability. In this paper, we discuss results from a computational investigation of O<sub>2</sub>(<sup>1</sup>Delta) production in flowing plasmas sustained at moderate pressures (< 50-100 Torr). This investigation was conducted using plug-flow and 2-dimensional models. In this study, we scaled power deposition and flow rates such that if there are not second order effects, yield should be constant and absolute O<sub>2</sub>(<sup>1</sup>Delta) production should scale linearly with pressure. We found in many cases that absolute O<sub>2</sub>(<sup>1</sup>Delta) production scaled sub-linearly with pressure. Ground state and vibrationally excited ozone are found to be one of the major quenchers of O<sub>2</sub>(<sup>1</sup>Delta) and the production of O<sub>3</sub> is a sensitive function of pressure. Gas heating per molecule increases at high pressures due to exothermic 3-body reactions which reduces O<sub>3</sub> production, increases O<sub>3</sub> destruction and, for certain conditions, restores yields. With increasing pressure and increasing absolute densities of atomic oxygen and pooling reactions of O<sub>2</sub>(<sup>1</sup>Delta), quenching by these species can become important in the afterglow. The yield of O<sub>2</sub>(<sup>1</sup>Delta) is also determined by discharge stability. For the geometries we investigated, discharge constriction becomes problematic at higher pressures, thereby reducing yields.","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126017606","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 : 2007-06-17DOI: 10.1109/PPPS.2007.4651953
M. Yalandin, S. Luybutin, S. Rukin, K. Sharypov, V. Shpak, S. Shunailov, B. Slovikovsky, S. Timoshenkov, M. Ulmasculov, V. Rostov, D. Grishin, V. Gubanov, A. Elchaninov, A. Klimov, G. Mesyats
Two versions of modernized experimental setup (i.e., nonstationary relativistic X-band BWO) were used for the generation of subnanoseeond-width, gigawatt-range pulses of microwave superradiation (SR).
{"title":"Repetitive Generation of X-Band Superradiation at 3-GW Peak Power","authors":"M. Yalandin, S. Luybutin, S. Rukin, K. Sharypov, V. Shpak, S. Shunailov, B. Slovikovsky, S. Timoshenkov, M. Ulmasculov, V. Rostov, D. Grishin, V. Gubanov, A. Elchaninov, A. Klimov, G. Mesyats","doi":"10.1109/PPPS.2007.4651953","DOIUrl":"https://doi.org/10.1109/PPPS.2007.4651953","url":null,"abstract":"Two versions of modernized experimental setup (i.e., nonstationary relativistic X-band BWO) were used for the generation of subnanoseeond-width, gigawatt-range pulses of microwave superradiation (SR).","PeriodicalId":446230,"journal":{"name":"2007 IEEE 34th International Conference on Plasma Science (ICOPS)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115004221","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 : 2007-06-17DOI: 10.1109/PPPS.2007.4346115
M. Glyavin, A. Luchinin
Summary form only given. Development of compact, simple and reliable sources of submillimeter wave radiation is important for numerous applications, which include plasma diagnostics, spectroscopy, new medical technology, atmospheric monitoring, chemical technologies, and production of high-purity materials. A demountable THz gyrotron tube with a pulse magnet has been designed, constructed and tested at IAP RAS. This work is based on the previous results obtained with gyrotrons using pulsed solenoids and on the development of an improved pulsed solenoid, producing up to 40 T magnetic field. The solenoid is made of a composite cable consisting of a Nb-60%Ti alloy mechanically reinforced in an outer copper shell. For reducing ohmic heating and stabilizing the operation, the solenoid is cooled by liquid nitrogen, which reduces the resistance by a factor of 7 in comparison with the room temperature resistance. The cable is wired directly on a thin stainless steel gyrotron body. This allows for significant reduction of the solenoid clearing hole diameter (up to 6 mm) and the energy required for obtaining the necessary magnetic field. Magnetic field is produced in the course of discharge of a bank of capacitors. The voltage and the coil current in 1.5 ms pulses did not exceed 2.5 kV and 6 kA, respectively (total storage energy was about 5.6 kJ). The pulse-to-pulse reproducibility of the magnetic field was within 0.05%. The pulses were repeated one in a minute. After more than 1000 pulses no signs of solenoid deterioration had been observed. Gyrotron components included the simplest cylindrical cavity (3 mm diameter) and diode type magnetron injection gun (accelerating voltage 20-25 kV, beam current 4-5 A, pulse duration 50 microseconds). First experimental results were obtained for high frequency operation at the fundamental cyclotron harmonic. Frequency measurements of single pulse submillimeter wavelength radiation were based on the mixing of the gyrotron signal with the signal from a millimeter-wave frequency synthesizer. The measured frequency is close to the cyclotron frequency defined by the magnetic field. The detection of microwave power was made by the semiconductor detector and by the dummy load. At several modes with frequencies near 1 THz, the output power close to 10 kW with the efficiency 8-10% was observed.
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