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ABSTRACT: Phosphor imaging plates (IPs) have been calibrated and proven useful for
quantitative x-ray imaging in the 1 to over 1000 keV energy range. In this
paper we report on calibration measurements made at XUV energies in the 60 to
900 eV energy range using beamline 6.3.2 at the Advanced Light Source at
Lawrence Berkeley National Laboratory. We measured a sensitivity of ~25 plus or
minus 15 counts/pJ over the stated energy range which is compatible with the
sensitivity of Si photodiodes that are used for time-resolved measurements. Our
measurements at 900 eV are consistent with the measurements made by Meadowcroft
et al. at ~1 keV.
02/2012;
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ABSTRACT: Investigations of magnetic field diffusion and plasma resistivity in 12-cm-diameter triple-gas-puff Ar Z -pinch implosions were carried out by using planar laser-induced fluorescence (PLIF), a laser shearing interferometer (LSI), and a laser wavefront analyzer (LWA) on a 3.5-MA 200-ns generator. The PLIF measurements gave the initial Ar gas distributions. The implosion velocity and electron density profiles were measured from LWA and/or LSI. From these, the implosion plasma sheath thickness, ion density, mean ion charge states, temperatures, and implosion velocity are obtained, which allows us to calculate the classical plasma resistivity. A 1-D analytic magnetic field diffusion model is constructed and used to predict the imploding plasma sheath thickness and its resistivity. Based on comparisons of the experimental measurements and the diffusion model prediction, we found out that plasma resistivity is enhanced by the cross-field diffusion above the classical value, as high as 60 times the Spitzer's value. Details are given in this paper.
IEEE Transactions on Plasma Science 05/2010; · 1.17 Impact Factor
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ABSTRACT: In a proof-of-principle test, we measured how the L-3 Pulse Sciences MBS (~200 keV peak voltage) Bremsstrahlung spectrum changed in time using a pair of filter-fluorescer channels, one at 41 ± 18 keV and another at 87 ± 27 keV. This demonstrates an approach for measuring a time-resolved bremsstrahlung spectrum for SGEMP applications, albeit with coarse energy resolution (30–45%). Using filter fluorescers and detecting the resultant X-rays with plastic scintillator PMTs, there is adequate sensitivity and dynamic range to correlate spectra from two sources, MBS and PITHON, which differ by a factor of up to ~100× in brightness (from 1 to 100 rad CaF2 at the spectrometer entrance). For such a correlation, no hardware changes are required—only the PMT gains need to be changed. The time resolution of the measurement is expected to be 2 ns.
Journal of Instrumentation 03/2009; 4(03):P03007. · 1.87 Impact Factor
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ABSTRACT: The distribution of argon gas injected by a 12-cm-diameter triple-shell nozzle was characterized using both planar, laser-induced fluorescence (PLIF) and high-sensitivity interferometry. PLIF is used to measure the density distribution at a given time by detecting fluorescence from an acetone tracer added to the gas. Interferometry involves making time-dependent, line-integrated gas density measurements at a series of chordal locations that are then Abel inverted to obtain the gas density distribution. Measurements were made on nominally identical nozzles later used for gas-puff Z-pinch experiments on the Saturn pulsed-power generator. Significant differences in the mass distributions obtained by the two techniques are presented and discussed, along with the strengths and weaknesses of each method.
The Review of scientific instruments 11/2008; 79(10):10E717. · 1.52 Impact Factor
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ABSTRACT: Recently, a new approach for efficiently generating K-shell x-rays in large-diameter, long-implosion time, structured argon gas Z-pinches has been demonstrated based on a “pusher-stabilizer-radiator” model. In this paper, direct observations of the Rayleigh–Taylor instability mitigation of a 12-cm diameter, 200-ns implosion time argon Z-pinch using a laser shearing interferometer (LSI) and a laser wavefront analyzer (LWA) are presented. Using a zero-dimensional snowplow model, the imploding plasma trajectories are calculated with the driver current waveforms and the initial mass distributions measured using the planar laser induced fluorescence method. From the LSI and LWA images, the plasma density and trajectory during the implosion are measured. The measured trajectory agrees with the snowplow calculations. The suppression of hydromagnetic instabilities in the “pusher-stabilizer-radiator” structured loads, leading to a high-compression ratio, high-yield Z-pinch, is discussed. For comparison, the LSI and LWA images of an alternative load (without stabilizer) show the evolution of a highly unstable Z-pinch.
Physics of Plasmas 02/2008; 15(2):022703-022703-9. · 2.15 Impact Factor
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R.J. Commisso,
J.P. Apruzese,
D. Mosher,
D.P. Murphy,
B.V. Weber,
J.W. Banister, B.H. Failor,
J.S. Levine,
N. Qi,
H.M. Sze,
A. Bixler,
P.L. Coleman,
A. Jarema,
J. Knight,
S. Lee,
M. Krishnan,
J. Thompson,
K. Wilson,
C.A. Coverdale,
C. Deeney
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ABSTRACT: We carry out an energy-inventory analysis for a 12-cm-diameter, argon gas-puff shot on the Saturn generator. From the measured pinch inductance time history, we infer the average radius of the pinch current, r ind , and the total work done on the pinch, E coupled , both as functions of time. The kinetic energy as a function of time, E KE , is inferred from r ind and the measured initial mass distribution, assuming all of the mass is accreted as in a snowplow. The results show that early in the implosion, E coupled ≈ E KE . However, when the pinch begins to radiate significantly, E KE begins to decrease while E coupled continues to increase. The increase in coupled energy goes into plasma internal energy, E int , i.e., ionization and thermal energies of the z-pinch plasma, and total radiation, E rad . During the time of K-shell emission, the significant (∼ 150-kJ) increase in E coupled is reflected in approximately the same increase in E rad . There is agreement between E int at the time of peak K-shell emission inferred from E coupled and measurements of E rad , and E int inferred from independent spectroscopic measurements combined with an atomic-physics model.
Pulsed Power Conference, 2007 16th IEEE International; 07/2007
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ABSTRACT: High power x-ray sources built for nuclear weapons effects testing are evolving toward larger overall diameters and smaller anode cathode gaps. We describe a framing camera developed to measure the time-evolution of these 20-50 ns pulsed x-ray sources produced by currents in the 1.5-2.5 MA range and endpoint voltages between 0.2 and 1.5 MV. The camera has up to 4 frames with 5 ns gate widths; the frames are separated by 5 ns. The image data are recorded electronically with a gated intensified CCD camera and the data are available immediately following a shot. A fast plastic scintillator (2.1 ns decay time) converts the x-rays to visible light and, for high sensitivity, a fiber optic imaging bundle carries the light to the CCD input. Examples of image data are shown.
Journal of Instrumentation 07/2007; 2(07):P07001. · 1.87 Impact Factor
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ABSTRACT: Large radius Z-pinches are inherently susceptible to the magnetic Rayleigh-Taylor (RT) instability because of their relatively long acceleration path. This has been reflected in a significant reduction of the argon K-shell yield as was observed when the diameter of the load was increased from 2.5 to >4 cm. Recently, an approach was demonstrated to overcome the challenge with a structured gas puff load that mitigates the RT instability, enhances the energy coupling, and leads to a high compression, high yield Z-pinch. The novel load consists of a “pusher,” outer region plasma that carries the current and couples energy from the driver, a “stabilizer,” inner region plasma that mitigates the RT growth, and a “radiator,” high-density center jet plasma that is heated and compressed to radiate. In 3.5-MA, 200-ns, 12-cm initial diameter implosions, the Ar K-shell yield has increased by a factor of 2, to 21 kJ, matching the yields obtained on the same accelerator with 100-ns, 2.5-cm-diam implosions. Further tests of such structured Ar gas load on ∼ 6 MA, 200-ns accelerators have achieved >80 kJ. From laser diagnostics and measurements of the K-shell and extreme ultraviolet emission, initial gas distribution and implosion trajectories were obtained, illustrating the RT suppression and stabilization of the imploding plasma, and identifying the radiation source region in a structured gas puff load. Magnetohydrodynamic simulations, started from actual initial density profiles, reproduce many features of the measurements both qualitatively and quantitatively.
Physics of Plasmas 04/2007; 14(5):056307-056307-8. · 2.15 Impact Factor
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ABSTRACT: Structured 12-cm-diam Ar gas-puff loads have recently produced Z-pinch implosions with reduced Rayleigh-Taylor instability growth and increased K-shell x-ray yield [
H. Sze, J. Banister, B. H. Failor, J. S. Levine, N. Qi, A. L. Velikovich, J. Davis, D. Lojewski, and P. Sincerny, Phys. Rev. Lett. 95, 105001 (2005)
]. To better understand the dynamics of these loads, we have measured the extreme ultraviolet (XUV) emission resolved radially, spectrally, and axially. Radial measurements indicated a compressed diameter of ≈ 3 mm, consistent with the observed load inductance change and an imploded-mass consisting of a ≈ 1.5-mm-diam, hot, K-shell-emitting core and a cooler surrounding blanket. Spectral measurements indicate that, if the load is insufficiently heated, then radiation from the core will rapidly photoheat the outer blanket, producing a strong increase in XUV emission. Also, adding a massive center jet ( ≥ 20% of load mass) increases the rise and fall times of the XUV emission to ≥ 40 ns, consistent with a more adiabatic compression and heating of the load. Axial measurements show that, despite differences in the XUV and K-shell emission time histories, the K-shell x-ray yield is insensitive to axial variations in load mass.
Physics of Plasmas 02/2007; 14(2):022703-022703-10. · 2.15 Impact Factor
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C.A. Coverdale,
C. Deeney,
B Jones,
P.D. LePell,
A.L. Velikovich,
J.W. Thornhill,
J.P. Apruzese,
K.G. Whitney,
R.W. Clark,
J Davis,
J.S. Levine,
H.M. Sze,
J.W. Banister, B.H. Failor,
N. Qi,
Y. Maron
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ABSTRACT: Over the last several years, the Z Accelerator has been engaged in research on near-Planckian x-ray sources for inertial confinement fusion and on K-shell emitting sources for radiation-material interaction studies. These radiating z pinches exhibit complex dynamics that have been, and continue to be, studied over a wide range of configurations. In this paper, the progress to date for the production of tens to hundreds of kilojoules of K-shell emission from 8 keV to 3 keV will be presented. Nested wire arrays and multi-shell gas puffs have been employed to help mitigate implosion instabilities and asymmetries to produce x-ray powers of tens of terawatts with emitted x-ray risetimes of a few nanoseconds. Spectroscopy and modeling of these pinches are providing insight into the role of temperature and density gradients and other plasma phenomena in the production of the radiation. Future directions will also be discussed.
Magagauss Magnetic Field Generation and Related Topics, 2006 IEEE International Conference on; 12/2006
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F.C. Young,
R.J. Commisso,
D.P. Murphy,
J.P. Apruzese,
D. Mosher,
A.L. Velikovich,
P.L. Coleman,
J.W. Banister, B.H. Failor,
J.S. Levine,
N. Qi,
H.M. Sze
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ABSTRACT: Time-resolved measurements of the absolute free-bound (FB) continuum spectrum emitted from a 12-cm-diameter argon gas-puff Z-pinch driven at ~6-MA peak current with 220- to 260-ns implosion times are reported. A crystal spectrometer is used with silicon diode detectors to provide kiloelectronvolt spectral resolution. The energy and absolute-intensity calibration procedures for the spectrometer are described. The slope of the FB continuum is well represented by a decaying exponential spectrum with a single electron temperature from which spatially averaged, time-resolved (T<sub>e</sub>(t)), and time-integrated (langT<sub>e</sub>rang) electron temperatures are inferred. An expression for the absolute FB continuum, which takes into account recombination onto bare as well as H-like species, is presented and used to infer time-integrated spatially averaged ion densities langn<sub>i</sub>rang. The values of langT<sub>e</sub>rang and langn<sub>i</sub>rang are in general agreement with the values of these quantities obtained by using the conventional K-shell line-ratio method. Values of T<sub>e</sub>(t) peak on the rise of the continuum radiation pulse and gradually decrease during the pulse. The fraction of the total energy radiated in the K-shell that resides in the FB continuum is 6%-10%, and this fraction increases with langn<sub>i</sub>rang. Calculated continuum spectra are in agreement with measured spectra
IEEE Transactions on Plasma Science 11/2006; · 1.17 Impact Factor
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ABSTRACT: A bent-crystal Laue {or Cauchois [
J. Phys. Radium 3, 320 (1932)
] geometry} spectrograph is a good compromise between sensitivity and spectral resolution for measuring x-ray spectra (15<E<100 keV) from large area x-ray sources because source-size spectral broadening is mitigated. We have designed, built, and tested such a spectrograph for measuring the spectra from electron-beam x-ray sources with diameters as large as 30 cm. The same spectrograph geometry has also been used to diagnose (with higher spectral resolution) smaller sources, such as x-ray tubes for mammography and laser-driven inertial fusion targets. We review our spectrograph design and describe the performance of different components. We have compared the reflectivity and spectral resolution of LiF, and Ge diffracting crystals. We have also measured the differences in sensitivity and spectral resolution using different x-ray to light converters (plastic scintillator, CsI, and Gd2O2S) fiber optically coupled to an intensified charge-coupled device camera. We have also coupled scintillating fibers to photomultiplier tubes to obtain temporal records for discrete energy channels.
Review of Scientific Instruments 09/2006; 77(10):10F314-10F314-4. · 1.37 Impact Factor
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ABSTRACT: We have proposed and demonstrated successfully a new approach for generating high-yield K-shell radiation with large-diameter gas-puff Z pinches. The novel load design consists of an outer region plasma that carries the current and couples energy from the driver, an inner region plasma that stabilizes the implosion, and a high-density center jet plasma that radiates. It increased the Ar K-shell yield at 3.46 MA in 200 ns implosions from 12 cm initial diameter by a factor of 2, to 21 kJ, matching the yields obtained earlier on the same accelerator with 100 ns implosions. A new "pusher-stabilizer-radiator" physical model is advanced to explain this result.
Physical Review Letters 10/2005; 95(10):105001. · 7.37 Impact Factor
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R.J. Commisso,
J.P. Apruzese,
Y.K. Chong,
J. Davis,
M.H. Frese,
D. Mosher,
D.P. Murphy,
D.G. Phipps,
J.W. Thornhill,
A.L. Velikovich, [......],
H. Sze,
A. Bixler,
P. Coleman,
M. Krishnan,
J. Thompson,
E. Carlson,
R.C. Hazelton,
E.J. Yadlowsky,
F. Davies,
C. De La Cruz
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ABSTRACT: Summary form only given. Large radius implosions of gas-puff Z-pinches are the subject of intense investigation. Such implosions are needed to achieve the high specific energy required to excite K-line radiation from high-atomic-number (e.g. Z>26) radiators, for proper matching with high-current (~10 MA and higher) generators, for continuum radiator concepts that require heating beyond the optimum He/H-like state for K-shell emission, and to utilize more efficiently long-current-rise-time (>100 ns) generators. The key physics issues involve R-T instability mitigation and energy coupling to the radiating plasma by the choice of the initial radial and axial mass profiles. In this talk, recent experimental and theoretical progress in this work are reviewed, including achieving 20-kJ of argon K-shell radiation from a 12-cm-diam. nozzle at 3.5 MA and 200-ns implosion time. The primary experimental testbeds are double-EAGLE (long-pulse mode, 3.5 MA, 210 ns) at TPSD and the Decade Quad (6 MA, 300 ns) at Arnold Engineering Development Center. Supporting experiments on Hawk (0.6 MA, 300 ns) at NRL are also reviewed. Besides the usual soft X-ray and electrical diagnostics, we have developed methods for measuring: the initial gas profile, the L-shell emitting region, the UV and continuum, the initial current flow paths, and the 2-D evolution of the pinch. Recent developments in 2-D radiation-hydrodynamic simulations are also reviewed
Plasma Science, 2005. ICOPS '05. IEEE Conference Record - Abstracts. IEEE International Conference on; 07/2005
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ABSTRACT: We have developed a 12-cm-diameter Ar gas Z-pinch load, which produces two annular gas shells and a center gas jet. The two-dimensional (2-D) gas density profiles of the load, in r-θ and r-z planes, were measured with submillimeter spatial resolutions using the planar-laser-induced fluorescence (PLIF) method, for conditions used in Z-pinch experiments. Due to interactions between the shells, the net gas density profile differs from the superposition of the individual shell profiles. Narrow density peaks are observed both at smaller and larger radii than the radius where the shells come in contact with each other. Two-dimensional flow velocity distributions are determined from the displacements between the fluorescence and later time phosphorescence images. The measured stream velocities of argon gas puffs are 650 ± 20 m/s, higher than the ideal gas velocity due to the formation of clusters in the supersonic gas flow. Indeed, clusters were observed in earlier Rayleigh scattering experiments. The gas measurements of the initial phase using the PLIF will be combined with other density measurements of the implosion and pinch phases to better understand the implosion dynamics and to provide initial conditions for simulation codes.
IEEE Transactions on Plasma Science 05/2005; · 1.17 Impact Factor
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ABSTRACT: Recently, an 8 cm diameter double-shell nozzle has produced argon Z pinches with high K-shell yields with implosion time of 210 ns. To produce even longer implosion time Z pinches for facilities such as Decade Quad [D. Price, et al., “Electrical and Mechanical Design of the Decade Quad in PRS Mode,” in Proceedings of the 12th IEEE Pulsed Power Conference, Monterey, CA, edited by C. Stallings and H. Kirbie (IEEE, New York, 1999), p. 489] (9 MA short circuit current at 300 ns), a larger nozzle (12 cm outer diameter) was designed and fabricated. During initial testing on Double-EAGLE [P. Sincerny et al., Proceedings of the 5th IEEE Pulsed Power Conference, Arlington, VA, edited by M. F. Rose and P. J. Turchi (IEEE, New York, 1985), p. 151], 9 kJ of argon K-shell radiation in a 6 ns full width at half maximum pulse was produced with a 240 ns implosion. The initial gas distributions produced by various nozzle configurations have been measured and their impact on the final radiative characteristics of the pinch are presented. The addition of a central jet to increase the initial gas density near the axis is observed to enhance the pinch quality, increasing K-shell yield by 17% and power by 40% in the best configuration tested. © 2004 American Institute of Physics.
Physics of Plasmas 04/2004; 11(5):2054-2059. · 2.15 Impact Factor
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R.C. Hazelton,
E.J. Yadlowsky,
J.J. Moschella,
E.P. Carlson,
C. Vidoli,
J. Niemel, B.H. Failor,
P.L. Coleman,
J.S. Levine,
Y. Song,
H.M. Sze,
J.W. Thornhill
[show abstract]
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ABSTRACT: Theoretical studies have predicted that the disruptive role of the Rayleigh-Taylor (R-T) instability on the current conduction and implosion characteristics of annular Z-pinch loads will be mitigated by mass accretion if uniform fill or multiple annular shell loads are used. Holographic interferometry was used to study these physical processes during the implosion phase of puff-on-puff loads on a terawatt accelerator. Both axial (r-z) density perturbation and azimuthal (r-θ) filamentation modes of the R-T instability were observed. Significant ionization (Z≈3-10) of the inner gas puff atoms was observed below the anode grid before the outer puff had imploded to this radial position. Radiation hydrodynamic calculations indicate that photoionization by radiation from the outer current carrying shell could not account for this ionization. Current flowing on the inner gas puff could be the source of this ionization. The effect of these physical processes on the radiation yield from z-pinches warrants further investigation.
IEEE Transactions on Plasma Science 01/2004; · 1.17 Impact Factor
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ABSTRACT: We have applied the technique of acetone laser-induced fluorescence (LIF) to the measurement of gas distributions from axisymmetric supersonic nozzles used to produce loads for z-pinch plasma radiation sources. Typical peak particle densities are ∼ 1017 particles/cm3 for loads imploded on the Double-EAGLE facility. The experimental approach uses a pulsed laser (266 nm wavelength, 2.2 mJ per pulse, 5 ns pulse width, and 3×107 W/cm2 intensity) to obtain a snapshot along a chord through the center of the gas density distribution at an arbitrary axial distance, z, from the nozzle exit. We report measurements at 4.3 and 20.0 mm from the exit of the nozzle for comparison with previous measurements. We find acceptable agreement between LIF and laser interferometer measurements. Strengths of the LIF approach include simplicity of implementation and high radial spatial resolution. © 2003 American Institute of Physics.
Review of Scientific Instruments 01/2003; 74(2):1070-1076. · 1.37 Impact Factor
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E. J. Yadlowsky,
F. Barakat,
E. P. Carlson,
R. C. Hazelton,
M. Keitz,
C. C. Klepper, B. H. Failor,
J. S. Levine,
Y. Song,
B. L. Whitten,
C. R. Coverdale,
C. Deeney,
R. B. Spielman
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ABSTRACT: The Doppler broadening of ion line profiles emitted by z-pinch plasma provides information about the thermalization of the implosion kinetic energy and the radiation efficiency of the pinch. Measurements of these line profiles are often complicated by source broadening in the instrument and opacity broadening of the emitted radiation. A high resolution concave crystal spectrometer in the Johann geometry was used to record the time averaged spectra of optically thin trace elements in the load. An imaging slit provided radially resolved but axially averaged spectra. The measurements indicate that lower ion temperatures (3–5 keV) are observed for Al wire loads on both the Saturn and Double EAGLE accelerators in the short current pulse mode (60–100 ns) than in the long pulse mode (125–225 ns) where values of 6.3–9.5 keV are observed. These values are smaller than those observed on Saturn by others. Furthermore, the wavelength at the line center of axially resolved ion line profiles on the DM-2 accelerator at Titan was observed to vary about some average value which implies an axially varying fluid motion of the plasma column transverse to the pinch axis. © 2002 American Institute of Physics.
Journal of Applied Physics 09/2002; 92(7):3458-3462. · 2.17 Impact Factor
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ABSTRACT: A series of Z pinch experiments using argon and krypton was conducted on the Double-EAGLE pulse power driver at 3.5 to 4.0 MA peak current and 170-190 ns implosion time. A shell-on-shell nozzle provided the opportunity to separate the two gases and to control which was driven more strongly (by virtue of being in the inner plenum). With argon in the inner plenum, 12 to 16±3 kJ krypton L-shell and 8 to 10±3 kJ of argon K-shell radiation was produced. With krypton in the inner plenum, 23.6 ±2.5 kJ of krypton L-shell and 2.5±2.3 kJ of argon K-shell radiation were produced. Since the optimum implosion times for the two gases were different, changing the mass of the z pinch varied the ratio of the yields. Using a streak spectrograph and PCDs with a Ross filter pair, the time history of the krypton and the argon radiation could be distinguished and seen to be simultaneous. Spectroscopic measurements of a chlorine dopant in the inner shell gas demonstrated that the implosions with krypton achieved lower density and electron temperature than with argon whether the krypton was in the inner or outer plenum.
IEEE Transactions on Plasma Science 05/2002; · 1.17 Impact Factor
