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André Anders - One of the best experts on this subject based on the ideXlab platform.
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Plasma of Vacuum DisCharges: The Pursuit of Elevating Metal Ion Charge States, Including a Recent Record of Producing Bi 13+
IEEE Transactions on Plasma Science, 2015Co-Authors: Georgy Yu. Yushkov, André Anders, E. M. Oks, Alexey G. Nikolaev, V. P. Frolova, Alexander VodopyanovAbstract:Metal Ions in the plasma of vacuum disCharges are commonly multiply Charged with Ion Charge states from 1+ to 3+, reaching 4+ and 5+ for some metals. The elevatIon of metal Ion Charge states in vacuum disCharge plasma is an interesting challenge for plasma physics because it requires a deeper understanding of the processes leading to a more intense IonizatIon of the electrode material. It also has practical implicatIons, for example, for metal Ion sources: elevatIon of Ion Charge state leads to a proportIonal increase in Ion beam energy for a given accelerating voltage. During the last two decades, various techniques have been used to increase the Ion Charge states, including: 1) applicatIon of a strong magnetic field to the cathode regIon of the vacuum arc; 2) applicatIon of supplemental microwave power to the disCharge plasma; 3) injectIon of an electron beam into the disCharge area; and 4) applicatIon of a short current pulse to the disCharge as to transiently increase the disCharge voltage and power, emulating the conditIons of a high-current vacuum spark. In this paper, we briefly survey the different techniques of metal Ion Charge state elevatIon and then present new experimental results by utilizing the spark regime and combining it with a strong pulsed magnetic field applied to the cathode regIon. Beams of Ions with high Charge state, up to a record Bi13+, were extracted from vacuum spark plasma. It is argued that the additIon of a magnetic field to the spark plasma magnetizes the electrons and limits plasma expansIon, which leads to an increase in the electron temperature relative to the free expansIon case and to an increase in the likelihood of electrons to cause Ionizing collisIons.
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Ion Charge state fluctuatIons in vacuum arcs
Journal of Physics D: Applied Physics, 2005Co-Authors: André Anders, Kentaro Fukuda, George Yu. YushkovAbstract:Ion Charge state distributIons of cathodic vacuum arcs have been investigated using a modified time-of-flight method. Experiments have been done in double gate and burst gate mode, allowing us to study both systematic and stochastic changes of Ion Charge state distributIons with a time resolutIon down to 100 ns. In the double gate method, two Ion Charge spectra are recorded with a well-defined time between measurements. The elements Mg, Bi, and Cu were selected for tests, representing metals of very different properties. For all elements it was found that large stochastic changes occur even at the limit of resolutIon. This is in agreement with fast changing arc properties observed elsewhere. CorrelatIon of results for short times between measurements was found but it is argued that this is due to velocity mixing rather than due to cathode processes. The burst mode of time-of-flight measurements revealed the systematic time evolutIon of Ion Charge states within a single arc disCharge, as opposed to previous measurements that relied on data averaged over many pulses. The technique shows the decay of the mean Ion Charge state as well as the level of material-dependent fluctuatIons.
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a periodic table of Ion Charge state distributIons observed in the transitIon regIon between vacuum sparks and vacuum arcs
IEEE Transactions on Plasma Science, 2001Co-Authors: André AndersAbstract:Ion Charge-state distributIons have been measured with high time resolutIon for short (20 /spl mu/s) and long (250 /spl mu/s) vacuum disCharges of 300 A. Charge-state data for 3 /spl mu/s after disCharge ignitIon and quasi-steady-state values are given for most conductive elements in a Periodic Table, including data for a few elements (rhodium, europium, and terbium) that were never before reported in the literature. Ion Charge states are significantly higher at the beginning of the disCharge and decay to their quasi-steady-state arc plasma values. It was found that the mean Ion Charge states can be fitted by functIons of the form Q~=Q~/sub t/spl rarr//spl infin// [1+A exp(-t//spl tau/)] where A is an enhancement functIon that depends on the power density. For the present conditIons, A/spl sim/1 and /spl tau//spl sim/50 /spl mu/s.
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a periodic table of Ion Charge state distributIons observed in the transitIon regIon between vacuum sparks and vacuum arcs
International Symposium on Discharges and Electrical Insulation in Vacuum, 2000Co-Authors: André AndersAbstract:Ion Charge state distributIons have been measured with high time resolutIon for short and long arc pulses. Data for 3 /spl mu/s and quasi-steady state are given for most conductive elements in a Periodic Table. The mean Ion Charge states can be fitted by functIons of the form Q~=Q~/sub t/spl rarr//spl infin// [1+A exp(-t//spl tau/)] where A is an enhancement functIon that depends on the power density. For the present conditIons, A/spl sim/1 and /spl tau//spl sim/50 /spl mu/s.
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Effect of multiple current spikes on the enhancement of Ion Charge states of vacuum arc plasmas
Journal of Applied Physics, 2000Co-Authors: George Yu. Yushkov, André Anders, E. M. Oks, I G BrownAbstract:Ion Charge state distributIons of vacuum arc Ion sources are correlated to the arc operating voltage. Recent research has shown that an enhancement of Ion Charges via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. The idea investigated is to further enhance the Ion Charge states by multiple current pulses. It is shown that although the Ion Charge states are enhanced compared to quasi-dc operatIon, the applicatIon of a sequence of pulses does not lead to the desired additIonal increase in Charge states. This can be attributed to the additIonal plasma productIon that is caused by higher arc currents: The additIonal power supplied to the plasma is distributed over a larger number of plasma particles. One can expect that in the limiting case of many current spikes, the Ion Charges state distributIon approaches the one known for arc plasmas at higher disCharge current.
I G Brown - One of the best experts on this subject based on the ideXlab platform.
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Effect of multiple current spikes on the enhancement of Ion Charge states of vacuum arc plasmas
Journal of Applied Physics, 2000Co-Authors: George Yu. Yushkov, André Anders, E. M. Oks, I G BrownAbstract:Ion Charge state distributIons of vacuum arc Ion sources are correlated to the arc operating voltage. Recent research has shown that an enhancement of Ion Charges via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. The idea investigated is to further enhance the Ion Charge states by multiple current pulses. It is shown that although the Ion Charge states are enhanced compared to quasi-dc operatIon, the applicatIon of a sequence of pulses does not lead to the desired additIonal increase in Charge states. This can be attributed to the additIonal plasma productIon that is caused by higher arc currents: The additIonal power supplied to the plasma is distributed over a larger number of plasma particles. One can expect that in the limiting case of many current spikes, the Ion Charges state distributIon approaches the one known for arc plasmas at higher disCharge current.
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Axial Ion Charge state distributIon in the vacuum arc plasma jet
Review of Scientific Instruments, 2000Co-Authors: Michael Keidar, I G Brown, Isak I. BeilisAbstract:We report on our experimental studies of the Ion Charge state distributIon (CSD) of vacuum arc plasmas using a time-of-flight diagnostic method. The dependence of the CSD on the axial distance from the plasma source regIon was measured for a titanium vacuum arc. It was found that the axial CSD profile is nonuniform. Generally, the mean Charge state increases approximately linearly with axial distance from about 1.7 at 12 cm up to 1.9 at 25 cm from the plasma source. A model for Ion transport in the free boundary plasma jet is proposed which is based on the existence of an electric field in the quasineutral plasma. This model qualitatively explains the experimental results. © 2000 American Institute of Physics.
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Enhanced Ion Charge states in vacuum arc plasmas using a ''current spike'' method
Review of Scientific Instruments, 2000Co-Authors: Alexey S. Bugaev, André Anders, E. M. Oks, G. Yu. Yushkov, I G BrownAbstract:Ion Charge state distributIons of vacuum arc Ion sources are correlated to the arc operating voltage. An enhancement of Ion Charge state via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. A current spike of 100–1000 A and several microseconds width was produced on top of the main arc current pulse (100 A, 250 μs). The Ion Charge state distributIon was measured by Charge-to-mass spectrometry. The measured Charge state distributIons were used as input data to the plasma model of partial local Saha equilibrium, giving the time-dependent electron temperature of the plasma at the freezing zone near the cathode spot.
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The effects of transmissIon through a magnetic filter on the Ion Charge state distributIon of a cathodic vacuum arc plasma
IEEE Transactions on Plasma Science, 1999Co-Authors: Marcela M.m. Bilek, I G BrownAbstract:In this paper we report the effects of transmissIon through a 90/spl deg/ solenoidal magnetic filter on the Ion Charge state distributIon of a vacuum arc plasma as a functIon of the magnetic field strength and the injectIon distance between the cathode and filter entrance. The mean Ion Charge state, measured using the time of flight technique, increased compared with the unfiltered value at low magnetic fields and then steadily decreased as the filter field was increased. At high fields, it was significantly lower than the unfiltered value.
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Ion Charge state distributIons of pulsed vacuum arc plasmas in strong magnetic fields
Review of Scientific Instruments, 1998Co-Authors: André Anders, George Yu. Yushkov, Alexey G. Nikolaev, I G BrownAbstract:Vacuum arc plasmas with disCharge currents of 300 A and duratIon 250 μs have been produced in strong magnetic fields up to 4 T. Ion Charge state distributIons have been measured for C, Al, Ag, Ta, Pt, Ho, and Er with a time-of-flight Charge-mass-spectrometer. Our previous measurements have been confirmed which show that Ion Charge states can be considerably enhanced when increasing the magnetic field up to about 1 T. The new measurements address the questIon of whether or not the additIonal increase continues at even higher magnetic field strength. It has been found that the increase becomes insignificant for field strengths greater than 1 T. Ion Charge state distributIons are almost constant for magnetic field strengths between 2 and 4 T. The results are explained by comparing the free expansIon length with the freezing length. The most significant changes of Charge state distributIons are observed when these lengths are similar.
E. M. Oks - One of the best experts on this subject based on the ideXlab platform.
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Ion Charge state distributIon in vacuum arc plasmas for composite Sn-Pb cathodes
2016 27th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV), 2016Co-Authors: V. P. Frolova, E. M. Oks, Alexey G. Nikolaev, G. Yu. YushkovAbstract:The report presents experimental results on the parameters of vacuum arc plasmas produced with composite Sn-Pb cathodes differing in atomic compositIon. The plasma was generated on a Mevva-V.Ru Ion source. The mass-Charge state of the plasma was studied using a time-of-flight spectrometer. The plasma parameters were compared with those for pure Sn and Pb cathodes. It is shown that the Ion fractIon of each cathode component in the plasma corresponds to its atomic fractIon in the cathode material. The Charge state of Ions of both components is determined by the average electron temperature in the cathode spot plasma. The mean Ion Charge state for pure cathodes is higher than that for composite Sn-Pb cathodes. The physics of the observed effects is discussed.
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Plasma of Vacuum DisCharges: The Pursuit of Elevating Metal Ion Charge States, Including a Recent Record of Producing Bi 13+
IEEE Transactions on Plasma Science, 2015Co-Authors: Georgy Yu. Yushkov, André Anders, E. M. Oks, Alexey G. Nikolaev, V. P. Frolova, Alexander VodopyanovAbstract:Metal Ions in the plasma of vacuum disCharges are commonly multiply Charged with Ion Charge states from 1+ to 3+, reaching 4+ and 5+ for some metals. The elevatIon of metal Ion Charge states in vacuum disCharge plasma is an interesting challenge for plasma physics because it requires a deeper understanding of the processes leading to a more intense IonizatIon of the electrode material. It also has practical implicatIons, for example, for metal Ion sources: elevatIon of Ion Charge state leads to a proportIonal increase in Ion beam energy for a given accelerating voltage. During the last two decades, various techniques have been used to increase the Ion Charge states, including: 1) applicatIon of a strong magnetic field to the cathode regIon of the vacuum arc; 2) applicatIon of supplemental microwave power to the disCharge plasma; 3) injectIon of an electron beam into the disCharge area; and 4) applicatIon of a short current pulse to the disCharge as to transiently increase the disCharge voltage and power, emulating the conditIons of a high-current vacuum spark. In this paper, we briefly survey the different techniques of metal Ion Charge state elevatIon and then present new experimental results by utilizing the spark regime and combining it with a strong pulsed magnetic field applied to the cathode regIon. Beams of Ions with high Charge state, up to a record Bi13+, were extracted from vacuum spark plasma. It is argued that the additIon of a magnetic field to the spark plasma magnetizes the electrons and limits plasma expansIon, which leads to an increase in the electron temperature relative to the free expansIon case and to an increase in the likelihood of electrons to cause Ionizing collisIons.
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Electron-beam enhancement of Ion Charge state fractIons in the metal-vapor vacuum-arc Ion source
Applied Physics Letters, 2001Co-Authors: Alexey S. Bugaev, George Yu. Yushkov, E. M. Oks, V. I. Gushenets, Timur Kulevoy, Ady Hershcovitch, B. M. JohnsonAbstract:We report demonstratIons of Ion Charge-state enhancement for an electron-beam metal-vapor vacuum-arc (E-MEVVA) Ion source. Results with a lead cathode yielded a maximum Ion Charge state of Pb7+, which implies an IonizatIon potential of at least 130 eV. Electron current densities j=70 A/cm2 and IonizatIon times τ≅100 μs produced jτ=9.2×10−3 C/cm2 (5.8×1016 electrons/cm2). Standard analysis for these conditIons indicates—somewhat surprisingly—that successive single (stepwise) IonizatIon accounts for the present observatIons, even though the Charge states are substantially higher than most previous results with MEVVA-based Ion sources.
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Effect of multiple current spikes on the enhancement of Ion Charge states of vacuum arc plasmas
Journal of Applied Physics, 2000Co-Authors: George Yu. Yushkov, André Anders, E. M. Oks, I G BrownAbstract:Ion Charge state distributIons of vacuum arc Ion sources are correlated to the arc operating voltage. Recent research has shown that an enhancement of Ion Charges via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. The idea investigated is to further enhance the Ion Charge states by multiple current pulses. It is shown that although the Ion Charge states are enhanced compared to quasi-dc operatIon, the applicatIon of a sequence of pulses does not lead to the desired additIonal increase in Charge states. This can be attributed to the additIonal plasma productIon that is caused by higher arc currents: The additIonal power supplied to the plasma is distributed over a larger number of plasma particles. One can expect that in the limiting case of many current spikes, the Ion Charges state distributIon approaches the one known for arc plasmas at higher disCharge current.
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Enhanced Ion Charge states in vacuum arc plasmas using a ''current spike'' method
Review of Scientific Instruments, 2000Co-Authors: Alexey S. Bugaev, André Anders, E. M. Oks, G. Yu. Yushkov, I G BrownAbstract:Ion Charge state distributIons of vacuum arc Ion sources are correlated to the arc operating voltage. An enhancement of Ion Charge state via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. A current spike of 100–1000 A and several microseconds width was produced on top of the main arc current pulse (100 A, 250 μs). The Ion Charge state distributIon was measured by Charge-to-mass spectrometry. The measured Charge state distributIons were used as input data to the plasma model of partial local Saha equilibrium, giving the time-dependent electron temperature of the plasma at the freezing zone near the cathode spot.
Marco Velli - One of the best experts on this subject based on the ideXlab platform.
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Ion Charge States in a Time-Dependent Wave-Turbulence-Driven Model of the Solar Wind
Solar Physics, 2019Co-Authors: Roberto Lionello, Cooper Downs, Jon A. Linker, Zoran Mikić, John Raymond, Chengcai Shen, Marco VelliAbstract:Ion fractIonal Charge states, measured in situ in the heliosphere, depend on the properties of the plasma in the inner corona. As the Ions travel outward in the solar wind and the electron density drops, the Charge states remain essentially unaltered or “frozen in”. Thus they can provide a powerful constraint on heating models of the corona and acceleratIon of the solar wind. We have implemented non-equilibrium IonizatIon calculatIons into a 1D wave-turbulence-driven (WTD) hydrodynamic solar wind model and compared modeled Charge states with the Ulysses 1994 – 1995 in situ measurements. We have found that modeled Charge-state ratios of C 6 + / C 5 + $\mbox{C}^{6+}/\mbox{C}^{5+}$ and O 7 + / O 6 + $\mbox{O}^{7+}/\mbox{O}^{6+}$ , among others, were too low compared with Ulysses measurements. However, a heuristic reductIon of the plasma flow speed has been able to bring the modeled results in line with observatIons, though other ideas have been proposed to address this discrepancy. We discuss implicatIons of our results and the prospect of including Ion Charge-state calculatIons into our 3D MHD model of the inner heliosphere.
George Yu. Yushkov - One of the best experts on this subject based on the ideXlab platform.
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Ion Charge state fluctuatIons in vacuum arcs
Journal of Physics D: Applied Physics, 2005Co-Authors: André Anders, Kentaro Fukuda, George Yu. YushkovAbstract:Ion Charge state distributIons of cathodic vacuum arcs have been investigated using a modified time-of-flight method. Experiments have been done in double gate and burst gate mode, allowing us to study both systematic and stochastic changes of Ion Charge state distributIons with a time resolutIon down to 100 ns. In the double gate method, two Ion Charge spectra are recorded with a well-defined time between measurements. The elements Mg, Bi, and Cu were selected for tests, representing metals of very different properties. For all elements it was found that large stochastic changes occur even at the limit of resolutIon. This is in agreement with fast changing arc properties observed elsewhere. CorrelatIon of results for short times between measurements was found but it is argued that this is due to velocity mixing rather than due to cathode processes. The burst mode of time-of-flight measurements revealed the systematic time evolutIon of Ion Charge states within a single arc disCharge, as opposed to previous measurements that relied on data averaged over many pulses. The technique shows the decay of the mean Ion Charge state as well as the level of material-dependent fluctuatIons.
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Electron-beam enhancement of Ion Charge state fractIons in the metal-vapor vacuum-arc Ion source
Applied Physics Letters, 2001Co-Authors: Alexey S. Bugaev, George Yu. Yushkov, E. M. Oks, V. I. Gushenets, Timur Kulevoy, Ady Hershcovitch, B. M. JohnsonAbstract:We report demonstratIons of Ion Charge-state enhancement for an electron-beam metal-vapor vacuum-arc (E-MEVVA) Ion source. Results with a lead cathode yielded a maximum Ion Charge state of Pb7+, which implies an IonizatIon potential of at least 130 eV. Electron current densities j=70 A/cm2 and IonizatIon times τ≅100 μs produced jτ=9.2×10−3 C/cm2 (5.8×1016 electrons/cm2). Standard analysis for these conditIons indicates—somewhat surprisingly—that successive single (stepwise) IonizatIon accounts for the present observatIons, even though the Charge states are substantially higher than most previous results with MEVVA-based Ion sources.
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Effect of multiple current spikes on the enhancement of Ion Charge states of vacuum arc plasmas
Journal of Applied Physics, 2000Co-Authors: George Yu. Yushkov, André Anders, E. M. Oks, I G BrownAbstract:Ion Charge state distributIons of vacuum arc Ion sources are correlated to the arc operating voltage. Recent research has shown that an enhancement of Ion Charges via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. The idea investigated is to further enhance the Ion Charge states by multiple current pulses. It is shown that although the Ion Charge states are enhanced compared to quasi-dc operatIon, the applicatIon of a sequence of pulses does not lead to the desired additIonal increase in Charge states. This can be attributed to the additIonal plasma productIon that is caused by higher arc currents: The additIonal power supplied to the plasma is distributed over a larger number of plasma particles. One can expect that in the limiting case of many current spikes, the Ion Charges state distributIon approaches the one known for arc plasmas at higher disCharge current.
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Ion Charge state distributIons of pulsed vacuum arc plasmas in strong magnetic fields
Review of Scientific Instruments, 1998Co-Authors: André Anders, George Yu. Yushkov, Alexey G. Nikolaev, I G BrownAbstract:Vacuum arc plasmas with disCharge currents of 300 A and duratIon 250 μs have been produced in strong magnetic fields up to 4 T. Ion Charge state distributIons have been measured for C, Al, Ag, Ta, Pt, Ho, and Er with a time-of-flight Charge-mass-spectrometer. Our previous measurements have been confirmed which show that Ion Charge states can be considerably enhanced when increasing the magnetic field up to about 1 T. The new measurements address the questIon of whether or not the additIonal increase continues at even higher magnetic field strength. It has been found that the increase becomes insignificant for field strengths greater than 1 T. Ion Charge state distributIons are almost constant for magnetic field strengths between 2 and 4 T. The results are explained by comparing the free expansIon length with the freezing length. The most significant changes of Charge state distributIons are observed when these lengths are similar.
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Recent study of Ion Charge state distributIon in vacuum arc Ion sources
Proceedings ISDEIV. 18th International Symposium on Discharges and Electrical Insulation in Vacuum (Cat. No.98CH36073), 1Co-Authors: Alexey S. Bugaev, I G Brown, André Anders, E. M. Oks, Alexey G. Nikolaev, V. I. Gushenets, George Yu. YushkovAbstract:The results of research of factors which can influence the Charge state distributIon (CSD) of Ions in vacuum arc plasmas are described. The CSD has been investigated using the time of flight (TOF) method. A strong influence of a magnetic field and the background pressure were observed. Here we summarize the results and discuss the influence of these parameters on the CSD of Ion beams for the Mevva and Titan Ion sources, and discuss possible approaches for increasing the Ion Charge states and the generatIon of hybrid gas-metal Ion beams by sources.
