2008 IEEE 35th International Conference on Plasma Science最新文献

{"title":"Thermodynamic and transport properties of H35 and F5 plasma cutting mixtures in non-equilibrium","authors":"V. Colombo, E. Ghedini, P. Sanibondi","doi":"10.1109/PLASMA.2008.4590972","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590972","url":null,"abstract":"Plasma science is a field in which modeling is used to play an important role for understanding and predicting the physical behavior of a plasma discharge. An application of plasma modeling is on plasma arc cutting devices which are characterized by a partially ionized plasma and by the use a of wide variety of gas mixtures, depending on the application. Knowledge of the thermodynamic and transport properties of these mixtures is a necessary prerequisite in order to perform correct simulations of these devices. Due to the lack of experimental data, the most reliable way to obtain these coefficients, for a wide variety of mixtures in the range of 300K to 40000K, is the Chapman-Enskog method for the solution of the Boltzmann equation. In this method the distribution function of the species is assumed to be a first order perturbed Maxwellian distribution. In these work some results are presented for H35 (argon 65% and hydrogen 35%) and F5 (nitrogen 95% and hydrogen 5%) mixtures using numerical codes developed by the authors for the calculation of nonequilibrium composition, thermodynamic and transport properties using the Bonnefoi electron and heavy particles decoupling approach. Results are compared with data available from previously published reports to check their accuracy.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"49 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82630195","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}

{"title":"Determination of ionization coefficient of atmospheric helium in DBD","authors":"Z. Liang, H. Luo, B. Lv, X. Wang, Z. Guan, L. Wang","doi":"10.1109/PLASMA.2008.4590783","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590783","url":null,"abstract":"Dielectric barrier discharge of helium at atmospheric pressure was investigated. Two plane-parallel electrodes, each covered by a 1-mm thick quartz plate, are 50 mm in diameter and the gas gap is 5 mm in length. Powered by an alternative voltage with a frequency of 33 kHz, a homogenous discharge was produced and characterized by one current pulse per half cycle of the applied voltage. The development of the discharge during one current pulse was recorded by taking a series of side-view photographs of 20 ns exposure time using an ICCD camera. It was important to find that a weakly luminous layer close to the anode was observed even at the time far ahead of the current pulse, which was considered as the result of a weak Townsend discharge. The distribution of light intensity in the gap was obtained by processing the photograph taken at the time of this weak Townsend discharge. The curve of this light distribution shows a shape quite similar to that of the total electron number in an electron avalanche as a function of the distance through which the avalanche passes. This suggested us that the curve could be used to determine ionization coefficient alpha in the Townsend discharge. The method is based on the proportionality of light intensity to the electron density in a discharge gap of a uniformly distributed electric field. By fitting a theoretically derived formula with the measured curve of light distribution, alpha was determined. It was found that the value of alpha is quite high even at relatively low reduced field. For instance, alpha =31 cm-1 for E/p = 3.6 V. cm-1 . Torr-1. The reason for this higher value of alpha may lie in the contribution of Penning ionization of helium metastables with impurities, especially with nitrogen molecules.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"1 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90183767","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}

{"title":"Influences of gas flow on atmospheric pressure glow discharge in helium","authors":"H. Luo, Z. Liang, B. Lv, X. Wang, Z. Guan, L. Wang","doi":"10.1109/PLASMA.2008.4590780","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590780","url":null,"abstract":"Atmospheric pressure glow discharge (APGD) was produced in a 5-mm helium gap between two plane-parallel electrodes of 50 mm in diameter, each covered by a 1-mm thick quartz plate. The influence of the helium gas flowing in parallel through the helium gap on APGD was studied. The helium flow rate varies up to 12 liter per minute, corresponding to helium at a speed of 67 cm/s flowing through a 5 mm x 60 mm cross section of the gap. The discharge current pulse appearing per half cycle of the applied voltage shifts forward as the helium flow speed increases. In accord with this phase shifting of the current pulse, the breakdown voltage of the helium gap that was deduced from the measured applied voltage and discharge current decreases from 1200 V to 950 V. Both amplitude, im, and pulse width (FWHM), tw, of the current pulse vary non-monotonically with the helium flow speed and are with same an inflexion point at flow speed of 1.4 cm/s. While im decreases from 31 mA to 20 mA and then slowly increases to 26 mA, tw increases from 750 ns to 1350 ns and then slowly decreases to about 900 ns. Although im varies with the flow speed in a way contrary to that of tw, the transferred charge calculated by integrating current over the time of one current pulse keeps almost a constant for different flow speed, which is consistent with the concept that the dielectric barrier acting as a capacitor. The side-view photographs of the discharge gap were taken by an ICCD camera with an exposure time of 20 ns. Compared with that in the case without helium flow, the discharge light with helium flow is relatively weaker over entire gap due to smaller discharge current. A distinct change in the discharge pattern with helium flow is that positive column gets shorter and Faraday dark space gets wider as the flow speed increases. It is important to find that spectrum line of 391.4 nm from the first negative system of nitrogen molecular ions gets weaker and weaker with the increase of helium flow speed. As is well known that the spectrum line of 391.4 nm is an indicative of Penning ionization between helium metastables and nitrogen impurity. The lower intensity of the spectrum line may be attributed to less impurity in the discharge gap with helium flow. As for the reason why the breakdown voltage of the helium gap decreases with helium flow, it was assumed that longer lifetimes of helium metastables result from the less impurity, quenchers of helium metastables, in the gap. For confirmation of this assumption, a monochrometer coupled with a photomultiplier is being prepared for measuring the time-resolved spectrum line of 391.4 nm.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"84 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80672383","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}

{"title":"Investigation of the cathodic region of a fluorescent lamp","authors":"Z. Tlais, D. Buso, S. Bhosle, G. Zissis","doi":"10.1109/PLASMA.2008.4590904","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590904","url":null,"abstract":"In this work the absolute intensity of barium lines during dimming operation in the vicinity of fluorescent lamp electrodes is investigated using the method of atomic emission spectroscopy. Investigations of fluorescent lamps (FL) are often focused on the electrodes, since the lifetime of the lamps is typically limited by the electrode lifetime and durability. In general, a commercial electrode system consists of a tungsten coil coated with a work function reducing emitter mix of alkali oxides, such as BaO, SrO and CaO. One of the main issues with dimming is a reduction in lamp life when the additional heating of the electrodes is not optimal, causing not-optimal electrode temperatures. There is a need for design rules for dimming to reach \"good\" lamp life, based on \"good\" additional heating. Such dimming design rules can be derived from measurements of the absolute intensities of both neutral (Ba I) and ionised (Ba II) barium lines, as these are key parameters to describe the evaporation and the sputtering of the emitter material. During steady state operation free barium is produced, which transports to the surface by diffusion through the coating mass. Barium escapes from the emitter during the course of lamp operation due to sputtering (primarily during starting and dimming), where the discharge is sustained by secondary electron emission from the (cold) electrode, and due to evaporation (primarily during steady-state), where the discharge is sustained by thermionic emission from the (hot) electrode. In the first type of experiment, the atomic emission diagnostic is used for the detection and measurement the intensities of the neutral (Bal-553.5 nm) and ionised (Ball-455.4n m) barium. The FL is dimmed for a range of discharge currents and auxiliary coil heating currents. It is seen that there is a threshold discharge current in which the behaviour of barium intensity with respect to current is markedly different. In a second type of experiment, we can estimate the relative intensities for Ba I and Ba II from the relative area under their line of absolute intensities. From these two measurements we show that the Ba loss can very easily be reduced by appropriate auxiliary coil heating.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"42 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80749289","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}

{"title":"Measurements of 193 NM laser air breakdown and scaling to the microwave regime","authors":"M. Thiyagarajan, J. Scharer, J. Way, J. Hummelt","doi":"10.1109/PLASMA.2008.4591173","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4591173","url":null,"abstract":"We report the measurements and analysis of air breakdown process by focusing 193 nm, 200 mJ, 10 MW high power UV laser radiation onto a 20-60 mum spot size that produces a maximum laser intensity of 1012-1013 W/cm2, well above the threshold flux for air ionization. The breakdown threshold is measured and compared with theoretical models including classical (collisional cascade) and quantum (multi-photon) ionization analyses. The air breakdown threshold is measured for a wide range of pressures ranging from 90 torr to 5 atmospheres. Higher pressure enhances the effective electric field due to the increased collisional frequency relative to the high laser frequency (1015 Hz). Multiphoton ionization (MPI) (n = 3) processes play a substantial role at 193 nm due to the high photon energy (6.4 eV). We examine regimes for which substantial MPI is present and analyze the plasma temperature and density evolution. The breakdown threshold data for air at 193 nm is correlated with the microwave breakdown regime using the concept of universal scaling, for which extensive microwave breakdown data is available as well as current microwave and mm wave breakdown experiments at Texas Tech University and MIT. An extensive range of optical and spectroscopic diagnostics with 5 ns time scale gating and 13 mum ICCD resolution has been constructed to characterize the plasma. The spatial and temporal evolution of the laser focused plasma is measured using shadowgraphy and two- color laser interferometry techniques. The plasma temperatures are obtained by measuring the velocity of the shock wave front and also by using optical emission spectroscopy. Optical emission spectroscopy is performed to diagnose the plasma temperature using the emission lines of O II ranging from 372.3 to 470.4 nm and the band of the N2 second positive system N2 (2+) (0,0) at 337.1 nm. Measurements of the core laser plasma density (ne= 8times1017/cc) and electron temperature (25 eV) decay are compared with a dominant two- and three-body recombination model with good correlation.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"6 12 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83698755","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}

{"title":"Experimental results from an 8-beam, 5-cavity multiple-beam klystron with 6% bandwidth","authors":"D. Abe, J. Qiu, B. Levush, D. Pershing, E. Wright, K. Nguyen, F. Wood, R. Myers, E. Eisen, I. Chernyavskiy, A. Vlasov","doi":"10.1109/PLASMA.2008.4590954","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590954","url":null,"abstract":"We describe the results of recent experiments with an eight- beam, five-cavity multiple-beam klystron (MBK). The electron gun is of the same design as used in our previous MBK and operates at a nominal cathode voltage of -45 kV and a total current of 32 A. The electrodynamic circuit is comprised of a two-gap input cavity, a two-gap idler cavity, two additional single-gap idler cavities, and a two-gap output cavity and has a total length of 22 cm. All of the multi-gap cavities operate in the pi-mode. Some of the cavities were loaded with a lossy dielectric to reduce the Q. Output power is extracted from both of the output resonator gaps in four waveguide arms (two on each gap). The tube produces ~ 600 kW of peak output power at saturation with a corresponding electronic efficiency of 40%. Beam transmission is excellent: > 99% in the small-signal regime and > 93% at saturation. Despite a mismatch in the input circuit that reduces the gain in the upper portion of the band, the MBK has a measured 3-dB bandwidth of ~ 6%. We will describe efforts to improve the input circuit match and will compare measured data with the results of numerical modeling using the MAGIC 3D particle-in-cell code and the 2.5D large-signal code, TESLA.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"93 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83838714","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}

{"title":"Development of electric propulsion systems at IRS","authors":"G. Herdrich, M. Auweter-Kurtz, D. Bock, M. Fertig, D. Haag, A. Nawaz, H. Roser","doi":"10.1109/PLASMA.2008.4591159","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4591159","url":null,"abstract":"This paper presents recent developments in the field of electric propulsion for interplanetary missions such as the arcjet system TALOS and the magnetoplasmadynamic thrusters Van-Allen belt and SIMP-LEX. Investigations include measurement of mass bit, plasma current, plasma acceleration time, plasma thrust, and plasma dynamic properties. Thruster optimization includes ground testing, numerical simulations as well as thermal modelling.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"63 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79196699","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}

{"title":"Microwave testing of a CVD diamond torus window prototype for iter","authors":"T. Scherer, R. Heidinger, A. Meier, K. Takahashi, K. Kajiwara, K. Sakamoto","doi":"10.1109/PLASMA.2008.4590797","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590797","url":null,"abstract":"For the plasma engineering of ITER, EC launchers will be used at the mid and top port levels. The EU is preparing the procurement of the upper port plug and JA the procurement of the equatorial. Part of these studies is to verify the window design and to work out, whether a concept is available for both launchers. To this goal, first experiments with low and high power mm-waves are performed and will be presented. The high power RE behavior of torus window assemblies with corrugated waveguides is being investigated by using IR imaging technique during high power microwave loading up to 1 MW at a frequency of 170 GHz at the JAEA gyrotron facility. Short and long pulse experiments are being performed to determine the temperature distribution over the whole diamond window area and the efficiency of the indirect cooling by a copper cuff. The occurrence of arcing is being studied as part of evaluation of the assembly design. For a characterization of the dielectric losses a low power measurement in a Fabry-Perot resonator setup at 170 GHz of the bare as-grown diamond disk will be compared with the brazed disk in the window housing. The evaluation of the curvature of the diamond disk is used as indicator of the residual stresses introduced in the joining process.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"12 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83231607","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}

{"title":"Atmospheric pressure field electron emission from nanostructures","authors":"A. Ağıral, J. Gardeniers","doi":"10.1109/PLASMA.2008.4590625","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590625","url":null,"abstract":"Atmospheric pressure field emission operation of 2 mum gap diode utilizing crystalline W18O49 nanowires, which were grown on sputter deposited tungsten films by thermal annealing at 700degC in ethene and nitrogen, was demonstrated. Field emission measurements in air follows Fowler-Nordheim electron tunneling theory and showed a low turn-on field of 3.3 V/mum, excellent stability and reproducibility with high emission current density (28 mA/cm2). At high electric fields (> 13 V/mum), current density diverged from Fowler-Nordheim equation and space charge limited conduction was observed. Explosion of emitters was observed similar to breakdown of small contact gaps in vacuum under overloading with high density field emission current. Resistive heating and the Nottingham mechanism may have produced the increased temperature during emission. Viability of pulsed electron emission at atmospheric pressure was demonstrated by applying a 100 Hz square wave voltage to the cathode. Pulsed electron emission with good repetition rate was observed.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"29 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81162522","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}

{"title":"Plasma diagnostics using computed tomography method","authors":"N. Denisova","doi":"10.1109/PLASMA.2008.4591120","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4591120","url":null,"abstract":"Summary form only given. A review of applications of the tomographic method for diagnostics of various plasma objects has been performed in this work. The objects are: methane plasma evolution in plasma-chemical reactor, a capillary discharge of inner diameter of 1 mm, a high-pressure non-symmetrical arc plasma, a high frequency inductive coupled plasma. The computed tomography is receiving increasing attention as a powerful method for the reconstruction of the local characteristics in both: high-temperature and low-temperature plasma. Local plasma characteristics can be derived from the integrated data by combining of an integrating measurement techniques and computer tomography algorithms and methods. This can provide much useful information on the plasma structure and its evolution in time. There are various theoretical approaches on the development of algorithms for obtaining tomographic images, such as algebraic reconstruction technique, maximum entropy method, minimum Fisher information algorithm, constrained optimization and maximum a posteriori methods. These algorithms are intended to be applied in different class of reconstruction problems corresponding to different kinds of prior and different kinds of data. A comparative analysis of these algorithms has been performed.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"62 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2008-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83435665","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}