Experiments at UNR demonstrate that interesting multiply ionized aluminum plasma (T=1-30 eV, n ˜ ... more Experiments at UNR demonstrate that interesting multiply ionized aluminum plasma (T=1-30 eV, n ˜ 10^18 cm-3, Z ˜ 3) can be created on the surface of mm-diameter aluminum rods by MA pulses of current. Surface temperature has been estimated by measuring the surface brightness in the green part of the visible spectrum (Awe et al., this conference). To investigate the spectral distribution throughout the visible region, which should vary as one over wavelength to the fourth power for temperatures above about 2 eV, a Jobin-Yvon f/2 spectrometer has been coupled with a linear array of silicon photodiodes. This instrument has spectral resolution of 30 nm on each of ten array elements covering the spectrum between 400 -- 700 nm and uses a Nikon lens/fiber optic collection system to enable observation of temperatures ranging from 1-30 eV. Experimental data with comparisons to the blackbody spectrum will be presented.
In pulsed power system, the performance of current carrying surfaces is limited by plasma generat... more In pulsed power system, the performance of current carrying surfaces is limited by plasma generation. Experiments with thick (diameter 0.5 -- 1.25 mm) aluminum rods, performed on the 1 MA Zebra generator at the Nevada Terawatt Facility reveal a threshold of 2.2 MG surface fields for plasma formation, independent of the initial diameter. For 1-mm thick loads, emission spectra obtained by extreme ultraviolet spectroscopy (8-18 nm spectral range) compare well with a modeled aluminum plasma temperature (PrismSPECT) of about 15 eV, both in early and late (peak current) plasma emissions. Time-gated, intensified imaging show spotty plasma formation at early times. This suggests that the temperature in the early spotty plasma quickly rises to 15 eV. At peak current, the intensity of the 15 eV plasma emissions reaches a maximum, suggesting that more of the same 15 eV plasma covers the surface of the aluminum rod.
The threshold for plasma formation on the surface of thick metal, in response to a pulsed multi-m... more The threshold for plasma formation on the surface of thick metal, in response to a pulsed multi-megagauss magnetic field, is experimentally measured. Thick Aluminum rods with initial diameters ranging from 0.5 to 2.0 mm are pulsed with the 1.0 MA, 100-ns Zebra generator. Surface magnetic field rise rates vary from 30 to 80 MG per microsecond, with corresponding peak fields of 1.5 to 4 MG. The onset of thermal plasma is observed through an abrupt increase in the rate of surface heating when the surface temperature reaches about 0.7 eV. Plasma forms when the surface magnetic field exceeds 2 MG, independent of the rise rate of the applied field. High resolution (30 micron, 2 ns) images detail surface dynamics during this transition from warm-dense-aluminum to plasma. Measurements of magnetic field, brightness temperature, spectrum of emitted radiation, time of plasma formation, expansion velocity, and growth of instabilities are presented.
IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference (Cat. No.01CH37255), 2001
Summary form only given. X-ray emission of Ti, Fe, Mo, W and Pt X-pinches at the Nevada Terawatt ... more Summary form only given. X-ray emission of Ti, Fe, Mo, W and Pt X-pinches at the Nevada Terawatt Facility (1 MA, 220 kJ) is studied. The energy and time scaling of X-rays were measured by a PCD and an XRD. A Ni bolometer (from SNL) measured the total X-ray/EUV energy radiated to be more than 10 kJ(4-5 kJ in L-shell and 30J in K-shell). Minimum duration of x-ray pulses were: from 1.5-2.5 ns for Ti and Fe K-shell radiation to 1-1.2 ns for Mo L-shell and W and Pt M-shell radiation. Typically, the emitting X-pinch region includes 1-4 hot bright spots (each smaller than the 30-micron resolution of the pinhole camera). It was shown that a X-ray image of the source moved a distance of 1-3 mm along the symmetry axis during the discharge with a maximum speed of 5×10(7)cm/s. Strong jets are observed (mostly in softer than Ti or Fe K-shell continuum emission) directed toward the X-pinch axis, perpendicular to the wires. It was observed that a strong electron beam is not only directed to the center of the X-pinch anode, but also toward the anode ends of the wires. Such a beam influences the plasma X-ray spectra (see A.S. Shlyaptseva et al.). A strong hard X-ray beam was observed upwards along the axial axis with an energy between 50 and several hundred of keV. Most X-ray spectra were recorded with time-integrated one-dimensional convex crystal spectrographs, spectropolarimeters (wavelengths shorter than 2.5 nm), and a time-integrated one-dimensional transmission-grating spectrometer (wavelengths from 2.0 to 8.0 nm). Experiments with the "Polychromator" have shown that often the time dependence of the intensity of selected spectral lines (for example, 0.261 nm He-like Ti or 0.185 nm He-like Fe) is different from the time dependence of short wavelength PCD signals
Understanding the evolution of ohmically heated conductors is exceptionally important for basic p... more Understanding the evolution of ohmically heated conductors is exceptionally important for basic physics and applications. The thermal ionization of the surface of Al-6061 rods with radii larger than the magnetic skin depth has been investigated with well-characterized experiments and detailed numerical modeling. With appropriate rod electrical connections, plasma formation is predominantly a thermal process. Time-resolved imaging, radiometry, spectroscopy, and laser shadowgraphy find plasma forms when the surface magnetic field reaches 2.2 MG. As the pulsed current grows, the visible spectrum shifts from more bremsstrahlung-like to blackbody-like. Radiation-MHD simulations with UP, MHRDR, and Raven are explaining the experimental data, which can be computationally reproduced using certain choices of models for resistivity, equation of state, other transport coefficients, and radiation opacities.
Hard X-Ray and Gamma-Ray Detector Physics III, 2001
ABSTRACT A new five-channel spectrometer is designed for registration of x-ray spectral line emis... more ABSTRACT A new five-channel spectrometer is designed for registration of x-ray spectral line emissions from plasmas with temporal resolution. All channels are independent from each other and include wide variety of dispersing elements (crystals and/or multiplayer mirrors) and detectors (Si-diodes or PCD). Sixth channel is used for device alignments with minimum adjustments can be used as channel for transmission diffraction grating spectrometer or channel for another time resolved detector. The device was used in experiments with different plasma sources in different configurations and showed its reliability and flexibility.
Experiments with conical array implosions on axial wire have been initiated at NTF, in parallel w... more Experiments with conical array implosions on axial wire have been initiated at NTF, in parallel with MHD modeling, as an approach to shear flow z-pinch stabilization research. The main objective is to determine and study the parameters range for which a shear flow created along the z-axis can stabilize a z-pinch plasma. In our experiments, the z-pinch to be stabilized
Digest of Technical Papers-IEEE International Pulsed Power Conference, 2007
ABSTRACT Summary form only given. A flux compression experiment is being designed for the Atlas p... more ABSTRACT Summary form only given. A flux compression experiment is being designed for the Atlas pulsed power facility. The purpose is to investigate generation of megagauss fields with liner technology in the geometry needed for compression of a stabilized diffuse z pinch.1 To survey possible parameters quickly and conveniently, a semi-analytic model has been developed that computes liner motion under the assumption that the liner remains cylindrically symmetric during the implosion and the metal of the liner is incompressible.2 Thus the liner thickness increases during implosion in a predictable way to conserve liner mass. Equations are derived for the time variation of liner position and circuit current including the effect of back pressure from the compressed flux. The model allows using realistic Atlas circuit parameters. The equations are integrated using the Matlab program and a standard Runge Kutta method. Recently the model has been extended to account for a shunt resistor and the resulting time-dependent current that would be generated inside the liner.3 The important advantage of a shunt resistor is that an auxiliary power supply is not needed to generate the seed flux which liner motion will compress. By tapping the power of Atlas to generate the seed flux, the incremental cost of a flux compression experiment is minimized. The selection of shunt material and dimensions must consider both the heating of the shunt and the amount of trapped flux, which along with the liner kinetic energy determines the final level of compressed magnetic field. Initial results suggest that readily available materials (a steel shunt and an aluminum liner) and properly chosen dimensions give a workable combination that generates magnetic field of several megagauss.
Plasma formation inside magnetically insulated transmission lines (MITLs) can lead to electrical ... more Plasma formation inside magnetically insulated transmission lines (MITLs) can lead to electrical closure. The process of plasma creation and the subsequent closure are not well understood. Experiments on MITLs, driven by a 1-MA, 100-ns pulse generator (Zebra), show that the time to closure varies discontinuously with the gap between the conductors. Remarkably, for a significant range of gaps, closure occurs
Page 1. Experimental Design of a Magnetic Flux Compression Experiment Stephan Fuelling,1,* Thomas... more Page 1. Experimental Design of a Magnetic Flux Compression Experiment Stephan Fuelling,1,* Thomas J. Awe,1 Bruno S. Bauer,1 Tasha Goodrich,1 Irvin R. Lindemuth,1 Volodymyr Makhin,1 Richard E. Siemon,1 Walter L. Atchison ...
ABSTRACT A plasma discharge could be an inexpensive and efficient EUV source for microlithography... more ABSTRACT A plasma discharge could be an inexpensive and efficient EUV source for microlithography, if issues of brightness, lifetime, debris, repetition rate, and stability can be resolved. A novel discharge EUV source (international patent pending) is being investigated that may offer an economical solution to these issues. The novel EUV discharge seeks to efficiently assemble a hot, dense, uniform, axially stable plasma with magnetic pressure and inductive current drive, employing resonant theta-pinch-type compression of plasma confined in a magnetic mirror. This resonantly compressed mirror plasma (RCMP) source would be continuously driven by a radio frequency oscillator, to obtain an EUV conversion efficiency greater than that of sources in which the plasma is discarded after each radiation burst. An analytic calculation indicates the novel RCMP source could provide 115 W of 13.45 nm radiation in 3.3 mm2sr etendue to an intermediate focus. Numerical modeling of RCMP dynamics has been performed with MHRDR-EUVL, a magnetohydrodynamic (MHD) numerical simulation with atomic and radiation physics. The numerical simulation demonstrates the efficacy of resonant magneto-acoustic heating. An experiment is being developed to test the new concept.
ABSTRACT We report the first experimental results on the state selective cross-section ratio {sig... more ABSTRACT We report the first experimental results on the state selective cross-section ratio {sigma}{sup +*}/{sigma}{sup *} of helium for electron and proton impact. Our results show consistently higher yields for electrons than for protons at higher velocities. A comparison is made between the cross-section ratios {sigma}{sup 2+}/{sigma}{sup +} of helium for electron and proton impact.
ABSTRACT An experimental and theoretical study is presented of the B+(1s22pnl, n=4 and 5) doubly ... more ABSTRACT An experimental and theoretical study is presented of the B+(1s22pnl, n=4 and 5) doubly excited states. Experimentally, low-energy electron emission spectra of B+, excited by B++He, B++Ar, and B++C-foil collisions, have been recorded with a zero-degree electron spectrometer setup. Several autoionizing states of B+ have been observed between 1 and 3 eV in the projectile emitter frame. The observed resonances, namely, (1s22p4s) 3P °, 1P °, (1s22p4p) 3D,1D, (1s22p4d) 3F °, 1F °, (1s22p4d) 3P °, and 1P ° do not appear in any previous data. The observations also suggest that the population of triply excited states in B is not important in the excitation process. Theoretically, five-state (2s,2p,3s,3p,3d) close-coupling calculations using impact have been performed to determine positions, widths, and partial collision strengths for 22 of the lowest B+(1s22pnl) resonance states. Excellent agreement between theoretical and experimental energy positions is obtained.
Plasma formation from thick Al rods ohmically heated during the diffusion of pulsed multimegagaus... more Plasma formation from thick Al rods ohmically heated during the diffusion of pulsed multimegagauss magnetic field is examined experimentally. Rods in the Z-pinch config- uration are driven to 1.0-MA peak current. The evolution of the resultant surface plasma is complex yet highly reproducible. Surface plasmas first form at discrete hot spots. As the pulsed current grows, plasma filaments form, first
Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1991
ABSTRACT Absolute EUV emission cross sections for simultaneous ionization and excitation of heliu... more ABSTRACT Absolute EUV emission cross sections for simultaneous ionization and excitation of helium by H+ and C6+ projectiles have been measured for impact energies between 0.83 and 2.3 MeV/u. In this energy range the mass, charge and velocity dependence of the ionization-excitation cross sections is compared for the He+(np) Rydberg states forn5. It is found that the experimental cross sections vary approximately asZ p 3 .
Plasma formation on an aluminum surface in the vicinity of high pulsed magnetic fields is studied... more Plasma formation on an aluminum surface in the vicinity of high pulsed magnetic fields is studied using the UNR 1 MA Zebra generator. This physics is important in a number of applications including magneto-inertial fusion. A variety of 1-mm diameter loads with different contact ...
Experiments on the UNR 1 MA Zebra generator drive magnetic fields of several megagauss on the sur... more Experiments on the UNR 1 MA Zebra generator drive magnetic fields of several megagauss on the surface of an aluminum conductor. This physics is important in a number of applications including magnetized target fusion. Several 1-mm diameter load designs were tested. ...
Experiments at UNR demonstrate that interesting multiply ionized aluminum plasma (T=1-30 eV, n ˜ ... more Experiments at UNR demonstrate that interesting multiply ionized aluminum plasma (T=1-30 eV, n ˜ 10^18 cm-3, Z ˜ 3) can be created on the surface of mm-diameter aluminum rods by MA pulses of current. Surface temperature has been estimated by measuring the surface brightness in the green part of the visible spectrum (Awe et al., this conference). To investigate the spectral distribution throughout the visible region, which should vary as one over wavelength to the fourth power for temperatures above about 2 eV, a Jobin-Yvon f/2 spectrometer has been coupled with a linear array of silicon photodiodes. This instrument has spectral resolution of 30 nm on each of ten array elements covering the spectrum between 400 -- 700 nm and uses a Nikon lens/fiber optic collection system to enable observation of temperatures ranging from 1-30 eV. Experimental data with comparisons to the blackbody spectrum will be presented.
In pulsed power system, the performance of current carrying surfaces is limited by plasma generat... more In pulsed power system, the performance of current carrying surfaces is limited by plasma generation. Experiments with thick (diameter 0.5 -- 1.25 mm) aluminum rods, performed on the 1 MA Zebra generator at the Nevada Terawatt Facility reveal a threshold of 2.2 MG surface fields for plasma formation, independent of the initial diameter. For 1-mm thick loads, emission spectra obtained by extreme ultraviolet spectroscopy (8-18 nm spectral range) compare well with a modeled aluminum plasma temperature (PrismSPECT) of about 15 eV, both in early and late (peak current) plasma emissions. Time-gated, intensified imaging show spotty plasma formation at early times. This suggests that the temperature in the early spotty plasma quickly rises to 15 eV. At peak current, the intensity of the 15 eV plasma emissions reaches a maximum, suggesting that more of the same 15 eV plasma covers the surface of the aluminum rod.
The threshold for plasma formation on the surface of thick metal, in response to a pulsed multi-m... more The threshold for plasma formation on the surface of thick metal, in response to a pulsed multi-megagauss magnetic field, is experimentally measured. Thick Aluminum rods with initial diameters ranging from 0.5 to 2.0 mm are pulsed with the 1.0 MA, 100-ns Zebra generator. Surface magnetic field rise rates vary from 30 to 80 MG per microsecond, with corresponding peak fields of 1.5 to 4 MG. The onset of thermal plasma is observed through an abrupt increase in the rate of surface heating when the surface temperature reaches about 0.7 eV. Plasma forms when the surface magnetic field exceeds 2 MG, independent of the rise rate of the applied field. High resolution (30 micron, 2 ns) images detail surface dynamics during this transition from warm-dense-aluminum to plasma. Measurements of magnetic field, brightness temperature, spectrum of emitted radiation, time of plasma formation, expansion velocity, and growth of instabilities are presented.
IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference (Cat. No.01CH37255), 2001
Summary form only given. X-ray emission of Ti, Fe, Mo, W and Pt X-pinches at the Nevada Terawatt ... more Summary form only given. X-ray emission of Ti, Fe, Mo, W and Pt X-pinches at the Nevada Terawatt Facility (1 MA, 220 kJ) is studied. The energy and time scaling of X-rays were measured by a PCD and an XRD. A Ni bolometer (from SNL) measured the total X-ray/EUV energy radiated to be more than 10 kJ(4-5 kJ in L-shell and 30J in K-shell). Minimum duration of x-ray pulses were: from 1.5-2.5 ns for Ti and Fe K-shell radiation to 1-1.2 ns for Mo L-shell and W and Pt M-shell radiation. Typically, the emitting X-pinch region includes 1-4 hot bright spots (each smaller than the 30-micron resolution of the pinhole camera). It was shown that a X-ray image of the source moved a distance of 1-3 mm along the symmetry axis during the discharge with a maximum speed of 5×10(7)cm/s. Strong jets are observed (mostly in softer than Ti or Fe K-shell continuum emission) directed toward the X-pinch axis, perpendicular to the wires. It was observed that a strong electron beam is not only directed to the center of the X-pinch anode, but also toward the anode ends of the wires. Such a beam influences the plasma X-ray spectra (see A.S. Shlyaptseva et al.). A strong hard X-ray beam was observed upwards along the axial axis with an energy between 50 and several hundred of keV. Most X-ray spectra were recorded with time-integrated one-dimensional convex crystal spectrographs, spectropolarimeters (wavelengths shorter than 2.5 nm), and a time-integrated one-dimensional transmission-grating spectrometer (wavelengths from 2.0 to 8.0 nm). Experiments with the "Polychromator" have shown that often the time dependence of the intensity of selected spectral lines (for example, 0.261 nm He-like Ti or 0.185 nm He-like Fe) is different from the time dependence of short wavelength PCD signals
Understanding the evolution of ohmically heated conductors is exceptionally important for basic p... more Understanding the evolution of ohmically heated conductors is exceptionally important for basic physics and applications. The thermal ionization of the surface of Al-6061 rods with radii larger than the magnetic skin depth has been investigated with well-characterized experiments and detailed numerical modeling. With appropriate rod electrical connections, plasma formation is predominantly a thermal process. Time-resolved imaging, radiometry, spectroscopy, and laser shadowgraphy find plasma forms when the surface magnetic field reaches 2.2 MG. As the pulsed current grows, the visible spectrum shifts from more bremsstrahlung-like to blackbody-like. Radiation-MHD simulations with UP, MHRDR, and Raven are explaining the experimental data, which can be computationally reproduced using certain choices of models for resistivity, equation of state, other transport coefficients, and radiation opacities.
Hard X-Ray and Gamma-Ray Detector Physics III, 2001
ABSTRACT A new five-channel spectrometer is designed for registration of x-ray spectral line emis... more ABSTRACT A new five-channel spectrometer is designed for registration of x-ray spectral line emissions from plasmas with temporal resolution. All channels are independent from each other and include wide variety of dispersing elements (crystals and/or multiplayer mirrors) and detectors (Si-diodes or PCD). Sixth channel is used for device alignments with minimum adjustments can be used as channel for transmission diffraction grating spectrometer or channel for another time resolved detector. The device was used in experiments with different plasma sources in different configurations and showed its reliability and flexibility.
Experiments with conical array implosions on axial wire have been initiated at NTF, in parallel w... more Experiments with conical array implosions on axial wire have been initiated at NTF, in parallel with MHD modeling, as an approach to shear flow z-pinch stabilization research. The main objective is to determine and study the parameters range for which a shear flow created along the z-axis can stabilize a z-pinch plasma. In our experiments, the z-pinch to be stabilized
Digest of Technical Papers-IEEE International Pulsed Power Conference, 2007
ABSTRACT Summary form only given. A flux compression experiment is being designed for the Atlas p... more ABSTRACT Summary form only given. A flux compression experiment is being designed for the Atlas pulsed power facility. The purpose is to investigate generation of megagauss fields with liner technology in the geometry needed for compression of a stabilized diffuse z pinch.1 To survey possible parameters quickly and conveniently, a semi-analytic model has been developed that computes liner motion under the assumption that the liner remains cylindrically symmetric during the implosion and the metal of the liner is incompressible.2 Thus the liner thickness increases during implosion in a predictable way to conserve liner mass. Equations are derived for the time variation of liner position and circuit current including the effect of back pressure from the compressed flux. The model allows using realistic Atlas circuit parameters. The equations are integrated using the Matlab program and a standard Runge Kutta method. Recently the model has been extended to account for a shunt resistor and the resulting time-dependent current that would be generated inside the liner.3 The important advantage of a shunt resistor is that an auxiliary power supply is not needed to generate the seed flux which liner motion will compress. By tapping the power of Atlas to generate the seed flux, the incremental cost of a flux compression experiment is minimized. The selection of shunt material and dimensions must consider both the heating of the shunt and the amount of trapped flux, which along with the liner kinetic energy determines the final level of compressed magnetic field. Initial results suggest that readily available materials (a steel shunt and an aluminum liner) and properly chosen dimensions give a workable combination that generates magnetic field of several megagauss.
Plasma formation inside magnetically insulated transmission lines (MITLs) can lead to electrical ... more Plasma formation inside magnetically insulated transmission lines (MITLs) can lead to electrical closure. The process of plasma creation and the subsequent closure are not well understood. Experiments on MITLs, driven by a 1-MA, 100-ns pulse generator (Zebra), show that the time to closure varies discontinuously with the gap between the conductors. Remarkably, for a significant range of gaps, closure occurs
Page 1. Experimental Design of a Magnetic Flux Compression Experiment Stephan Fuelling,1,* Thomas... more Page 1. Experimental Design of a Magnetic Flux Compression Experiment Stephan Fuelling,1,* Thomas J. Awe,1 Bruno S. Bauer,1 Tasha Goodrich,1 Irvin R. Lindemuth,1 Volodymyr Makhin,1 Richard E. Siemon,1 Walter L. Atchison ...
ABSTRACT A plasma discharge could be an inexpensive and efficient EUV source for microlithography... more ABSTRACT A plasma discharge could be an inexpensive and efficient EUV source for microlithography, if issues of brightness, lifetime, debris, repetition rate, and stability can be resolved. A novel discharge EUV source (international patent pending) is being investigated that may offer an economical solution to these issues. The novel EUV discharge seeks to efficiently assemble a hot, dense, uniform, axially stable plasma with magnetic pressure and inductive current drive, employing resonant theta-pinch-type compression of plasma confined in a magnetic mirror. This resonantly compressed mirror plasma (RCMP) source would be continuously driven by a radio frequency oscillator, to obtain an EUV conversion efficiency greater than that of sources in which the plasma is discarded after each radiation burst. An analytic calculation indicates the novel RCMP source could provide 115 W of 13.45 nm radiation in 3.3 mm2sr etendue to an intermediate focus. Numerical modeling of RCMP dynamics has been performed with MHRDR-EUVL, a magnetohydrodynamic (MHD) numerical simulation with atomic and radiation physics. The numerical simulation demonstrates the efficacy of resonant magneto-acoustic heating. An experiment is being developed to test the new concept.
ABSTRACT We report the first experimental results on the state selective cross-section ratio {sig... more ABSTRACT We report the first experimental results on the state selective cross-section ratio {sigma}{sup +*}/{sigma}{sup *} of helium for electron and proton impact. Our results show consistently higher yields for electrons than for protons at higher velocities. A comparison is made between the cross-section ratios {sigma}{sup 2+}/{sigma}{sup +} of helium for electron and proton impact.
ABSTRACT An experimental and theoretical study is presented of the B+(1s22pnl, n=4 and 5) doubly ... more ABSTRACT An experimental and theoretical study is presented of the B+(1s22pnl, n=4 and 5) doubly excited states. Experimentally, low-energy electron emission spectra of B+, excited by B++He, B++Ar, and B++C-foil collisions, have been recorded with a zero-degree electron spectrometer setup. Several autoionizing states of B+ have been observed between 1 and 3 eV in the projectile emitter frame. The observed resonances, namely, (1s22p4s) 3P °, 1P °, (1s22p4p) 3D,1D, (1s22p4d) 3F °, 1F °, (1s22p4d) 3P °, and 1P ° do not appear in any previous data. The observations also suggest that the population of triply excited states in B is not important in the excitation process. Theoretically, five-state (2s,2p,3s,3p,3d) close-coupling calculations using impact have been performed to determine positions, widths, and partial collision strengths for 22 of the lowest B+(1s22pnl) resonance states. Excellent agreement between theoretical and experimental energy positions is obtained.
Plasma formation from thick Al rods ohmically heated during the diffusion of pulsed multimegagaus... more Plasma formation from thick Al rods ohmically heated during the diffusion of pulsed multimegagauss magnetic field is examined experimentally. Rods in the Z-pinch config- uration are driven to 1.0-MA peak current. The evolution of the resultant surface plasma is complex yet highly reproducible. Surface plasmas first form at discrete hot spots. As the pulsed current grows, plasma filaments form, first
Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1991
ABSTRACT Absolute EUV emission cross sections for simultaneous ionization and excitation of heliu... more ABSTRACT Absolute EUV emission cross sections for simultaneous ionization and excitation of helium by H+ and C6+ projectiles have been measured for impact energies between 0.83 and 2.3 MeV/u. In this energy range the mass, charge and velocity dependence of the ionization-excitation cross sections is compared for the He+(np) Rydberg states forn5. It is found that the experimental cross sections vary approximately asZ p 3 .
Plasma formation on an aluminum surface in the vicinity of high pulsed magnetic fields is studied... more Plasma formation on an aluminum surface in the vicinity of high pulsed magnetic fields is studied using the UNR 1 MA Zebra generator. This physics is important in a number of applications including magneto-inertial fusion. A variety of 1-mm diameter loads with different contact ...
Experiments on the UNR 1 MA Zebra generator drive magnetic fields of several megagauss on the sur... more Experiments on the UNR 1 MA Zebra generator drive magnetic fields of several megagauss on the surface of an aluminum conductor. This physics is important in a number of applications including magnetized target fusion. Several 1-mm diameter load designs were tested. ...
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