Pub Date : 2008-06-15DOI: 10.1109/PLASMA.2008.4590683
I. Litovko, V. Gushenets, E. Oks
Computer simulation for ion sources optimization used for ion implantations is reported. Highly stripped ion source is designed to provide high current beams of multiply charged phosphorous and boron ions for high energy ion implantation. Maximum current transport for boron ions is obtained with the optimisation of geometries of the ion-optical system and experimental setup. The maximum attainable percentage of singly charged B ions was 65% and the total current transport was about 60%.
{"title":"Computer simulation for ion sources optimization","authors":"I. Litovko, V. Gushenets, E. Oks","doi":"10.1109/PLASMA.2008.4590683","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590683","url":null,"abstract":"Computer simulation for ion sources optimization used for ion implantations is reported. Highly stripped ion source is designed to provide high current beams of multiply charged phosphorous and boron ions for high energy ion implantation. Maximum current transport for boron ions is obtained with the optimisation of geometries of the ion-optical system and experimental setup. The maximum attainable percentage of singly charged B ions was 65% and the total current transport was about 60%.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"124 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":"77319595","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590713
D. Ziegler, T. Mussenbrock, R. Brinkmann
This paper proposes an effective nonlinear model which derives from a mathematically demanding spatially resolved model by means of concentrating on the fundamental mode. Based on the obtained mode the interaction of the linear bulk and the nonlinear boundary sheath is analyzed. Comparing the results to traditional linear theory shows that nonlinear effects highly complicate the interaction of bulk and sheath. The low driving frequency as well as the high driving frequency contributes to electron heating within the discharge. It can be shown that this effect of nonlinear electron resonance heating considerably contributes to the total power budget of the discharge. Comparing calculated rf currents with experimentally obtained data provides qualitatively and quantitatively good results.
{"title":"Nonlinear dynamics in dual frequency capacitive discharges","authors":"D. Ziegler, T. Mussenbrock, R. Brinkmann","doi":"10.1109/PLASMA.2008.4590713","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590713","url":null,"abstract":"This paper proposes an effective nonlinear model which derives from a mathematically demanding spatially resolved model by means of concentrating on the fundamental mode. Based on the obtained mode the interaction of the linear bulk and the nonlinear boundary sheath is analyzed. Comparing the results to traditional linear theory shows that nonlinear effects highly complicate the interaction of bulk and sheath. The low driving frequency as well as the high driving frequency contributes to electron heating within the discharge. It can be shown that this effect of nonlinear electron resonance heating considerably contributes to the total power budget of the discharge. Comparing calculated rf currents with experimentally obtained data provides qualitatively and quantitatively good results.","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":"83645294","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590939
O. Diaz, V. Cooray, F. Roman
Summary form only given. Most of the experimental data available in the literature on electrical discharges is referred to the breakdown characteristics of discharge gaps for different geometries in air. However, in order to understand the physical processes associated with the electrical discharges, it is necessary to obtain experimental data on the temporal variation of current- voltage during the pre-breakdown and the spark stage. This information is necessary to understand how the resistance of the discharge channel varies as a function of time and the energy dissipation during the discharge. The aim of this work present a study performed on a self- breakdown pressured gap, where voltage and current were measured when a fast electrostatic discharge (ESD) occurred between two electrodes. This fast ESD was produced by a floating electrode charged with corona currents, obtaining some hundreds of amperes of peak-current amplitude and a few nanoseconds of risetime and pulse width. The internal gas was dry air at different pressures.
{"title":"Spark gap resistance for an electrostatic discharge at different pressures","authors":"O. Diaz, V. Cooray, F. Roman","doi":"10.1109/PLASMA.2008.4590939","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590939","url":null,"abstract":"Summary form only given. Most of the experimental data available in the literature on electrical discharges is referred to the breakdown characteristics of discharge gaps for different geometries in air. However, in order to understand the physical processes associated with the electrical discharges, it is necessary to obtain experimental data on the temporal variation of current- voltage during the pre-breakdown and the spark stage. This information is necessary to understand how the resistance of the discharge channel varies as a function of time and the energy dissipation during the discharge. The aim of this work present a study performed on a self- breakdown pressured gap, where voltage and current were measured when a fast electrostatic discharge (ESD) occurred between two electrodes. This fast ESD was produced by a floating electrode charged with corona currents, obtaining some hundreds of amperes of peak-current amplitude and a few nanoseconds of risetime and pulse width. The internal gas was dry air at different pressures.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"67 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":"91301307","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590710
J. Choi, Y. Noma, K. Terashima
Summary form only given. New cryogenic plasma source, so-called cryo plasma was established under atmospheric pressure. Cryo dielectric barrier discharge (DBD) system could easily control processing temperature from room temperature to 78 K by liquid nitrogen. Reactor chamber for this experiment consisted of two chambers, the inner and outer chamber. We employed a DBD reactor into the inner chamber and connected an AC power supply operating at a frequency of 20 kHz. Helium as discharge gas was introduced into the inner chamber and the operating pressure was kept at atmospheric pressure, with a steady state condition. And the outer chamber played a role to control and sustain gas temperature by flowing liquid nitrogen as a refrigerant. After experiments, we found out the plasma properties, such as discharge patterns and color, showed the temperature- dependent behavior as gas temperature went down. And this result was closely related with the change of emission spectra measured by optical emission spectroscopy. Conclusively, the change of gas temperature induced a transition of discharge mode. The detail will be discussed at the conference.
{"title":"Temperature-dependent transition of discharge pattern during helium cryo plasma","authors":"J. Choi, Y. Noma, K. Terashima","doi":"10.1109/PLASMA.2008.4590710","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590710","url":null,"abstract":"Summary form only given. New cryogenic plasma source, so-called cryo plasma was established under atmospheric pressure. Cryo dielectric barrier discharge (DBD) system could easily control processing temperature from room temperature to 78 K by liquid nitrogen. Reactor chamber for this experiment consisted of two chambers, the inner and outer chamber. We employed a DBD reactor into the inner chamber and connected an AC power supply operating at a frequency of 20 kHz. Helium as discharge gas was introduced into the inner chamber and the operating pressure was kept at atmospheric pressure, with a steady state condition. And the outer chamber played a role to control and sustain gas temperature by flowing liquid nitrogen as a refrigerant. After experiments, we found out the plasma properties, such as discharge patterns and color, showed the temperature- dependent behavior as gas temperature went down. And this result was closely related with the change of emission spectra measured by optical emission spectroscopy. Conclusively, the change of gas temperature induced a transition of discharge mode. The detail will be discussed at the conference.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"27 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":"89667593","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590923
K. Eleršič, Z. Vratnica, D. Vujošević, I. Junkar, J. Kovač, M. Mozetič, U. Cvelbar
Inductively coupled oxygen plasma was used to study degradation of Escherichia coli. Bacteria were deposited on a silicon wafer substrate and treated by plasma for different periods. The effect of oxygen plasma ions and neutral oxygen atoms was observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The first effect was removal of the envelope - a protective coating bacteria developed during growing. After removing the envelope (capsule), slow etching of the cell wall was observed. Further treatment resulted in gradual removal of the cell wall and after 240s, only ashes remained. Images of plasma interaction steps during bacteria degradation are presented and the plasma radical interaction steps explained by observed damages of bacteria.
{"title":"Surface analysis of demages on escherichia coli caused by oxygen plasma radicals","authors":"K. Eleršič, Z. Vratnica, D. Vujošević, I. Junkar, J. Kovač, M. Mozetič, U. Cvelbar","doi":"10.1109/PLASMA.2008.4590923","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590923","url":null,"abstract":"Inductively coupled oxygen plasma was used to study degradation of Escherichia coli. Bacteria were deposited on a silicon wafer substrate and treated by plasma for different periods. The effect of oxygen plasma ions and neutral oxygen atoms was observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The first effect was removal of the envelope - a protective coating bacteria developed during growing. After removing the envelope (capsule), slow etching of the cell wall was observed. Further treatment resulted in gradual removal of the cell wall and after 240s, only ashes remained. Images of plasma interaction steps during bacteria degradation are presented and the plasma radical interaction steps explained by observed damages of bacteria.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"70 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":"73553706","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590643
S. Guare, D. Dimitriu, C. Ionita, R. Schrittwieser
Summary form only given. By positively biasing an electrode immersed into low-temperature plasma up to a certain threshold value, a complex space charge structure appears in front of it, in form of a luminous quasi-spherical plasma body. This structure was sometimes called anode glow, ball of fire or fireball. Experimental investigation shown that such a structure consists of a positive nucleus (ion-enriched plasma) confined by an electrical double layers. The potential drop across the double layer is almost equal to the ionization potential of the background gas atoms. By accelerating the electrons from the surrounding plasma through this potential drop, the double layer can maintain the equilibrium between the production and the losses of the charged particles (electrons and positive ions), ensuring the existence of the structure. Here we report on the spectral investigation of such a complex space charge structure, in argon plasma. The spectral domain was 550-750 nm, identifying the lines corresponding to different excited states of the argon. The spectral profile of the fireball was obtained by recording the spectra at different positions in front of the electrode. The obtained results shed a new light on the elementary processes at the origin of the appearance and dynamics of the fireball, namely the electron-neutral impact excitations and ionizations.
{"title":"Spectral investigation of a fireball in low-temperature argon plasma","authors":"S. Guare, D. Dimitriu, C. Ionita, R. Schrittwieser","doi":"10.1109/PLASMA.2008.4590643","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590643","url":null,"abstract":"Summary form only given. By positively biasing an electrode immersed into low-temperature plasma up to a certain threshold value, a complex space charge structure appears in front of it, in form of a luminous quasi-spherical plasma body. This structure was sometimes called anode glow, ball of fire or fireball. Experimental investigation shown that such a structure consists of a positive nucleus (ion-enriched plasma) confined by an electrical double layers. The potential drop across the double layer is almost equal to the ionization potential of the background gas atoms. By accelerating the electrons from the surrounding plasma through this potential drop, the double layer can maintain the equilibrium between the production and the losses of the charged particles (electrons and positive ions), ensuring the existence of the structure. Here we report on the spectral investigation of such a complex space charge structure, in argon plasma. The spectral domain was 550-750 nm, identifying the lines corresponding to different excited states of the argon. The spectral profile of the fireball was obtained by recording the spectra at different positions in front of the electrode. The obtained results shed a new light on the elementary processes at the origin of the appearance and dynamics of the fireball, namely the electron-neutral impact excitations and ionizations.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"16 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":"75402403","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590662
C. Hsieh, Y.W. Liang, C. Lin, K. Leou
Summary form only given. We developed a planar transmission-line microwave interferometer for monitoring of electron density for applications in process real-time feedback control of plasma based semiconductor fabrication tools, such plasma etchers or PECVDs. The principle of this technique is the same as the conventional microwave interferometers except that the sensing microwave propagates along a transmission line structure. In this study, the sensor was a microstrip transmission-line where microwave propagates at a phase velocity determined by the structure and the electron density of the surrounding plasma. Thus the variation of plasma density can be estimated from the phase shift of the transmitted microwave from one to the other end of the transmission-line. Compared to the conventional microwave interferometers where line-averaged plasma density is measured, the transmission-line type microwave sensor will be less susceptive to the interference caused by multi-passes reflection/refraction effect resulting from nonuniformity of the plasma density profiles. Therefore, it provides a measurement of higher sensitivity and wider dynamic range. In this work, an U-shaped transmission line with 3 mm in width and 86 mm in length, the quartz based substrate thickness is 3.5 mm, and the distance between input and output ports is 23 mm. The dispersion characteristics of this microstrip line immersed in a plasma of different electron densities was simulated by using a commercial tool, High Frequency Structure Simulation code (Ansoft HFSS), a full- wave electromagnetic simulator using the finite element method. The simulation results show that the phase shift increases gradually with the plasma electron density with a sensitivity 12 degree / 1010 cm"3. Experimental demonstration has been performed with an inductively coupled plasma. The sensor was mounted on the inner wall of plasma chamber. Measurement results show that the dependence of electron density of plasma source RF power predicted by the sensor agrees with the Hairpin probe measurements.
{"title":"A microstrip-line microwave interferometer for monitoring of plasma density of processing plasmas","authors":"C. Hsieh, Y.W. Liang, C. Lin, K. Leou","doi":"10.1109/PLASMA.2008.4590662","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590662","url":null,"abstract":"Summary form only given. We developed a planar transmission-line microwave interferometer for monitoring of electron density for applications in process real-time feedback control of plasma based semiconductor fabrication tools, such plasma etchers or PECVDs. The principle of this technique is the same as the conventional microwave interferometers except that the sensing microwave propagates along a transmission line structure. In this study, the sensor was a microstrip transmission-line where microwave propagates at a phase velocity determined by the structure and the electron density of the surrounding plasma. Thus the variation of plasma density can be estimated from the phase shift of the transmitted microwave from one to the other end of the transmission-line. Compared to the conventional microwave interferometers where line-averaged plasma density is measured, the transmission-line type microwave sensor will be less susceptive to the interference caused by multi-passes reflection/refraction effect resulting from nonuniformity of the plasma density profiles. Therefore, it provides a measurement of higher sensitivity and wider dynamic range. In this work, an U-shaped transmission line with 3 mm in width and 86 mm in length, the quartz based substrate thickness is 3.5 mm, and the distance between input and output ports is 23 mm. The dispersion characteristics of this microstrip line immersed in a plasma of different electron densities was simulated by using a commercial tool, High Frequency Structure Simulation code (Ansoft HFSS), a full- wave electromagnetic simulator using the finite element method. The simulation results show that the phase shift increases gradually with the plasma electron density with a sensitivity 12 degree / 1010 cm\"3. Experimental demonstration has been performed with an inductively coupled plasma. The sensor was mounted on the inner wall of plasma chamber. Measurement results show that the dependence of electron density of plasma source RF power predicted by the sensor agrees with the Hairpin probe measurements.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"147 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":"77957392","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4591063
P. Zobdeh, R. Sadighi-Bonabi, H. Afarideh
Ultrashort laser sources have been developed by the C.PA technique in the recent years .This progress causes to produce quasi-monoenergetic electron during the laser-plasma interaction. Such high quality electron beams are generated by different mechanisms. One of the new and effective methods is to prepare the cavity or bubble regime when an ultrashort laser pulse propagates in underdense plasma. In this work we discuss about how to control the output electron energy beam in the cavity regime with using a proper parabolic plasma density profile and discuss about quality of the mentioned beam. The result shows the mentioned profile can control gain and energy of the quasi-monoenergetic electron beam.
{"title":"Control of electron beam in bubble regime produced by high intense laser plasma interaction","authors":"P. Zobdeh, R. Sadighi-Bonabi, H. Afarideh","doi":"10.1109/PLASMA.2008.4591063","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4591063","url":null,"abstract":"Ultrashort laser sources have been developed by the C.PA technique in the recent years .This progress causes to produce quasi-monoenergetic electron during the laser-plasma interaction. Such high quality electron beams are generated by different mechanisms. One of the new and effective methods is to prepare the cavity or bubble regime when an ultrashort laser pulse propagates in underdense plasma. In this work we discuss about how to control the output electron energy beam in the cavity regime with using a proper parabolic plasma density profile and discuss about quality of the mentioned beam. The result shows the mentioned profile can control gain and energy of the quasi-monoenergetic electron beam.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"153 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":"77994953","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590821
T. Berghofer, C. Eing, B. Flickinger, C. Gusbeth, R. Strassner, W. Frey, S. Schneider
Summary form only given. Pulsed laser fluorescence microscopy (PLFM) using the voltage sensitive dye ANNINE-6 permits measurements of transmembrane potentials of biological cells with a time resolution of five nanoseconds. Several theories have been proposed to explain the change of the membrane conductivity in response to an external electric field, e.g. pore-models, phase transitions due to electro-compression or local disturbances in the membrane caused by lipid rafts. The measured field-strength-dependence of the transmembrane potential of both mammalian and plant cells exhibits a saturation character which is supposed to occur due to the formation of nano/micropores. For mammalian cells with a typical diameter of 15 mum saturation effects set in at external field strengths in the order of 1 kV/cm. For tobacco-protoplasts (BY-2) with an average size three times the diameter of mammalian cells, the same saturation effect can be observed at about one third of the saturation field strength, observed for mammalian cells. This confirms the general expectations of current membrane charging models. Furthermore, protoplasts exhibit a strong asymmetry of the membrane charging at the hyper- and depolarized hemisphere of the cell, which occurs due to the higher rest potential compared to mammalian cells. The threshold transmembrane voltage for the onset of pore formation has been estimated to an absolute value of +/-200 mV. In addition, time- and field-strength-dependencies of the transmembrane potential's azimuthal distribution have been examined. Time-courses of the transmembrane potential in response to an electric field pulse show a good agreement with theoretical predictions. Results for HEK293, HeLa and 22Rv1 cells as well as for tobacco-protoplasts will be presented and the underlying measurement setup will be described.
{"title":"Transmembrane potential measurements of mammalian and plant cells","authors":"T. Berghofer, C. Eing, B. Flickinger, C. Gusbeth, R. Strassner, W. Frey, S. Schneider","doi":"10.1109/PLASMA.2008.4590821","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590821","url":null,"abstract":"Summary form only given. Pulsed laser fluorescence microscopy (PLFM) using the voltage sensitive dye ANNINE-6 permits measurements of transmembrane potentials of biological cells with a time resolution of five nanoseconds. Several theories have been proposed to explain the change of the membrane conductivity in response to an external electric field, e.g. pore-models, phase transitions due to electro-compression or local disturbances in the membrane caused by lipid rafts. The measured field-strength-dependence of the transmembrane potential of both mammalian and plant cells exhibits a saturation character which is supposed to occur due to the formation of nano/micropores. For mammalian cells with a typical diameter of 15 mum saturation effects set in at external field strengths in the order of 1 kV/cm. For tobacco-protoplasts (BY-2) with an average size three times the diameter of mammalian cells, the same saturation effect can be observed at about one third of the saturation field strength, observed for mammalian cells. This confirms the general expectations of current membrane charging models. Furthermore, protoplasts exhibit a strong asymmetry of the membrane charging at the hyper- and depolarized hemisphere of the cell, which occurs due to the higher rest potential compared to mammalian cells. The threshold transmembrane voltage for the onset of pore formation has been estimated to an absolute value of +/-200 mV. In addition, time- and field-strength-dependencies of the transmembrane potential's azimuthal distribution have been examined. Time-courses of the transmembrane potential in response to an electric field pulse show a good agreement with theoretical predictions. Results for HEK293, HeLa and 22Rv1 cells as well as for tobacco-protoplasts will be presented and the underlying measurement setup will be described.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"31 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":"74995255","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 : 2008-06-15DOI: 10.1109/PLASMA.2008.4590846
Liu Yinghui, S. Kern, M. Beringer, M. Thumm, S. Alberti, J. Hogge
Summary form only given. Recently, gyrotron-based spectrometers suitable for nuclear magnetic resonance (NMR) studies have been constructed to study dynamic nuclear polarization which can result in significant enhancement of the NMR signal. In the present paper multimode calculations of a low-power (above 10W) high-frequency (200 GHz -300 GHz) gyrotron for NMR spectroscopy applications have been performed. The co- rotating TE-7,2 mode has been chosen to be the main operating cavity mode. Five neighbor modes (TE7,2; TE-4,3; TE4,3; TE-2,4; TE2,4) whose coupling factors are above 30% of the main mode and most probably can be excited in the cavity are included into the calculation using the FZK SELFT code packet designed for time dependent and self-consistent multimode calculations. The frequency fine tuning was obtained via the excitation of a sequence of longitudinal modes of TE-7,2,q by varying the beam voltage from 15 kV upward and the magnetic field from 9.6 T to 9.77 T. The results show that the main mode TE-7,2 is quite stable against the possible transverse mode competitors within this magnetic field range and a continuous frequency tuning range more than 800 MHz (263.43 GHz - 264.28 GHz) has been achieved with a velocity ratio of 1.3, the beam radius and current being 1.33 mm and 100 mA respectively.
{"title":"Multimode calculations of frequency tunable gyrotrons for dynamic nuclear polarization applications","authors":"Liu Yinghui, S. Kern, M. Beringer, M. Thumm, S. Alberti, J. Hogge","doi":"10.1109/PLASMA.2008.4590846","DOIUrl":"https://doi.org/10.1109/PLASMA.2008.4590846","url":null,"abstract":"Summary form only given. Recently, gyrotron-based spectrometers suitable for nuclear magnetic resonance (NMR) studies have been constructed to study dynamic nuclear polarization which can result in significant enhancement of the NMR signal. In the present paper multimode calculations of a low-power (above 10W) high-frequency (200 GHz -300 GHz) gyrotron for NMR spectroscopy applications have been performed. The co- rotating TE-7,2 mode has been chosen to be the main operating cavity mode. Five neighbor modes (TE7,2; TE-4,3; TE4,3; TE-2,4; TE2,4) whose coupling factors are above 30% of the main mode and most probably can be excited in the cavity are included into the calculation using the FZK SELFT code packet designed for time dependent and self-consistent multimode calculations. The frequency fine tuning was obtained via the excitation of a sequence of longitudinal modes of TE-7,2,q by varying the beam voltage from 15 kV upward and the magnetic field from 9.6 T to 9.77 T. The results show that the main mode TE-7,2 is quite stable against the possible transverse mode competitors within this magnetic field range and a continuous frequency tuning range more than 800 MHz (263.43 GHz - 264.28 GHz) has been achieved with a velocity ratio of 1.3, the beam radius and current being 1.33 mm and 100 mA respectively.","PeriodicalId":6359,"journal":{"name":"2008 IEEE 35th International Conference on Plasma Science","volume":"31 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":"74679296","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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