Alla S. Safronova et al- Spectroscopic and Imaging Study of Combined W andMo X-Pinches at 1 MA...

8/3/2019 Alla S. Safronova et al- Spectroscopic and Imaging Study of Combined W andMo X-Pinches at 1 MA Z-Pinch Generators

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2256 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 5, OCTOBER 2006

Spectroscopic and Imaging Study of CombinedW and Mo X -Pinches at 1 MA Z -Pinch Generators

Alla S. Safronova, Member, IEEE , Victor L. Kantsyrev, Member, IEEE , Dmitry A. Fedin, Glenn Osborne,M. Fatih Yilmaz, Travis Hoppe, Vidya Nalajala, Jonathan D. Douglass, Ryan D. McBride,Marc D. Mitchell, Member, IEEE , Lloyd M. Maxson, and David A. Hammer, Fellow, IEEE

Abstract—Experiments with X -pinches made with both Moand W wires have been performed on 1-MA pulsed power genera-tors at Cornell University and University of Nevada, Reno. X-rayimages and spectra have been studied and compared for threedifferent configurations of X -pinch loads with Mo and W wires.For all X -pinches, the image size decreases with decreasing wave-length and photoconducting diode (PCD) signals show multiplebursts except for one variant of the mixed Mo and W config-urations. Time-gated, as well as time-integrated, images indi-cate the presence of radiation from energetic electrons. Previous

experience with application of L-shell Mo modeling to variousZ - and X -pinch experiments helped to determine plasma para-meters in the X -pinches studied here, and permitted identifica-tion of M-shell W spectral features useful for plasma parameterestimation.

Index Terms—L-shell Mo radiation, modeling, M-shell W radi-ation, X -pinch, X-ray imaging, X-ray spectroscopy.

I. INTRODUCTION

TUNGSTEN (W) wire arrays have been studied extensivelyon the Z accelerator at Sandia National Laboratories

(SNL) since 1998 when it was shown that they could reach

X-ray powers up to 200 TW and X-ray energies of nearly2 MJ [1]. Substantial progress has been made recently evalu-ating this source of radiation for indirect-drive inertial confine-ment fusion (ICF) and other high-energy density applications(see, for example, [2] and the many references therein). Un-derstanding the radiation spectra emitted by these plasmas isnecessary to be able to interpret the experimental observationsand to benchmark computer codes used to try to predict resultsto be obtained from future pulsed power machines. At present,spectroscopic diagnostic methods using M-shell W radiation isnot advanced enough to provide reliable plasma parameters.In addition, the recent experiments showing axial radiationasymmetry in dynamic hohlraums driven by W wire arrays [3]

Manuscript received December 30, 2005; revised March 20, 2006. This workwas supported by the National Nuclear Security Administration (NNSA) underDepartment of Energy (DoE) Cooperative Agreement DE-F03-02NA00057and by the DoE/NNSA under University of Nevada, Reno (UNR) GrantDE-FC52-01NV14050.

A. S. Safronova, V. L. Kantsyrev, G. Osborne, M. F. Yilmaz, T. Hoppe, andV. Nalajala are with the Department of Physics, University of Nevada, Reno,NV 89557 USA (e-mail: alla@ physics.unr.edu).

D. A. Fedin was with the Department of Physics, University of Nevada,Reno, NV 89557 USA. He is now with the Department of Mechanical andAerospace Engineering, University of California, San Diego, CA 92093 USA.

J. D. Douglass, R. D. McBride, M. D. Mitchell, L. M. Maxson, andD. A. Hammer are with the Laboratory of Plasma Studies, Cornell University,Ithaca, NY 14853 USA.

Digital Object Identifier 10.1109/TPS.2006.878361

provide additional evidence for the necessity and importance of development of such diagnostics.

University-scale pulsed power devices can produce plasmascomparable in parameters with the SNL-Z machine, albeit inmuch smaller volumes. In particular, X -pinch plasmas area good source to study radiative properties of high densityand temperature pinch plasmas from ∼1-µm to ∼1-mm scalesize and to test new diagnostics and modeling. In addition

X -pinches offer the variety of load configurations that differ intypes of wire connections (planar loop or twisted), number of wires (two, four, or even more wires), and wire materials. Forexample, extensive radiographic and spectroscopic research onX -pinch plasmas has been performed on the 450-kA device atCornell University (CU) (see [4] and references therein). X-rayspectroscopic, imaging, and electron-beam studies of variousX -pinches were also carried out using the 1-MA ZEBRApulsed power machine at the University of Nevada, Reno(UNR) (see, for example, [5], [6]). There it was shown that WX -pinches generate better quality and resolution X-ray spectrawhen mixed with other, lighter materials, such as Mo [7]. Thispaper also focuses on the work with combined X -pinches with

W wires, expanding the previous preliminary report [7] byinclusion of more experimental and theoretical data.

II. EXPERIMENTAL DATA

The two university-scale pulsed power generators used forthe present experiments, COBRA and ZEBRA, have similarpeak currents of about 1 MA and rise times of about 100 ns.The details of experiments and diagnostics on ZEBRA can befound otherwise (see, for example, [6]) and COBRA is a newlyrebuilt pulsed power device that just started to produce data[8]. Experiments on both generators were focused on the study

of dense plasma formation using X -pinches made with Moand W wires of the same length of 23 mm, but the X -pinchloads were prepared in a different way. The loads on COBRAwere 4-wire X -pinches twisted at the cross point and having620-µg mass (2× 30.5-µm Mo wires and 2× 19.8-µmW wires, COBRA pulse 286). The loads on ZEBRA weretwo-wire planar-loop asymmetric X -pinches [6] of ∼890-µgmass with a 35-µm W wire in the anode loop and a 50-µmMo wire in the cathode loop denoted by W/Mo X -pinches(ZEBRA pulses 472 and 473) or with a 50-µm Mo wire in theanode loop and a 35-µm W wire in the cathode loop denotedby Mo/W X -pinches (ZEBRA pulse 474). Fig. 1 shows atypical set of X-ray pinhole images along with a current and a

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SAFRONOVA et al.: SPECTROSCOPIC AND IMAGING STUDY OF COMBINED W AND MoX-PINCHES 2257

Fig. 1. (a) Time-integrated and (b) time-gated X-ray pinhole images recorded through different filters. (c) Current, PCD signal, and timing of MCP frames fromcombined W/Mo X-pinches produced in ZEBRA pulse 473.

photoconducting diode (PCD) signal. Such set of data has beenproduced for all studied loads. Specifically, time-integratedX-ray pinhole images [Fig. 1(a)] were recorded with theresolution of 220 µm through three layers of the KodakBIOMAX MS film protected by two different sets of filters(25-µm Be and 3-µm Mylar coated with a 0.2-µm Al andwith an additional 100-µm Mylar filter) for the first film atλ < 10.3 Å and at λ < 4.4 Å, for the second film at λ < 3.7 Åand at λ < 3.1 Å, and for the third film at λ < 2.9 Å and atλ < 2.7 Å, respectively. The three images behind the first set

of filters are shown in Fig. 1(a). The anode was at the topand the cathode was at the bottom of the images. The imagesrecorded in softer X-rays (at λ < 10.3 Å) are much larger size(millimeter scale) than in harder X-rays. The source becomes acompact source with one distinct hot spot (hundred-micrometerscale) in harder X-rays (at λ < 4.4 Å and less) and continuesto decrease slightly in size with a wavelength decrease in allimages. The spectra studied in this paper are in a spectral regionfrom 4 to 6 Å, then we assume that the source of radiationwas a compact source with a size of few hundred micrometerand less. It is important to emphasize that the mentionedresolution did not allow us to distinguish a more detailedstructure inside a central hot spot but few much smaller hotspots localized in the direction towards the cathode are clearlyseen on two images (at λ < 3.7 Å and at λ < 2.9 Å). Time-gated pinhole images recorded with the resolution of 230 µmthrough two different sets of filters at λ < 12 Å (15-µm Be and3-µm Mylar coated with a 0.2-µm Al) and at λ < 4 Å (with anadditional 120-µm Mylar filter) are at the top and at bottom of Fig. 1(b), respectively. The anode was at the top and the cathodewas at the bottom of the images. These time-gated images wereregistered during six frames, which temporal positions areshown in Fig. 1(c). The PCD signal [see Fig. 1(c)] shows fourmajor X-ray bursts three of which occurred before the maxi-mum of the current (which was about 1 MA) and were captured

on the microchannel plate (MCP) detectors. The third burst(the most intense from three bursts with two peaks) resulted in

Fig. 2. X-ray “cold” characteristic lines of Mo and W (from wire materials)and of Fe, Cr, and Ni (from the anode) recorded by a LiF crystal in X-pinchexperiments on ZEBRA.

more intense images of the radiation source (frames 5 and 6).The time-gated images show temporal evolution of the size andthe structure of the source from a very compact hot spot to thebrighter source with few hot spots in the cross point and alongX -pinch wires towards the anode. All time-gated, as well astime-integrated, images indicate the presence of radiation fromenergetic electrons [Fig. 1(a) and (b)], for the Mo/W X -pinchin particular. Additional evidence of energetic electrons inX -pinch plasmas is provided by the observation in X-rayspectra of strong “cold” characteristic lines from both wirematerials (Mo and W) and from the stainless steel anode (Fe,Cr, and Ni). These particular spectra were recorded by a LiFcrystal (2d = 4.027 Å) protected from the plasma by a 70-µm

Be and 3-µm Mylar coated with a 0.2-µm Al in X -pinchexperiments on ZEBRA (see Fig. 2).




Fig. 3. Comparison of X-ray spectra recorded by a mica crystal spectrometer

from a four-wire twisted combined [W, Mo]X-pinchon COBRA and by a KAPcrystal spectrometer from a two-wire planar-loop W/Mo X-pinch on ZEBRA.

The X-ray spectrum shown in this figure, as well as the firstfilm image at the bottom, were produced in the Mo X -pinchexperiment whereas the two other images were from combinedW and Mo X -pinch experiments on ZEBRA. All K-shellcharacteristic lines of Mo (the first order of K α at λ = 0.714 Åand K β at λ = 0.632 Å as well as the second order of K α)are extremely bright for the Mo X -pinch and are detectablefor the combined Mo and W X -pinches, for Mo/W X -pinchesin particular. In addition, “cold” L-shell characteristic linesof W (Lα at λ = 1.476 Å, Lβ1 at λ = 1.282 Å and Lβ2 at

λ = 1.245 Å) appear in spectra from combined Mo and WX -pinches. L-shell characteristic lines of W are brighter forW/Mo X -pinches (W wire in the anode loop) than for Mo/WX -pinches (W wire in the cathode loop), which was expected.There is no detectable difference in the intensities of the charac-teristic lines from the stainless steel anode. There are strong K αlines of Fe, Cr, and Ni both for W/Mo and Mo/W X -pinches,which indicates that the electron beams near the anode arenot sensitive to the material in the top loop. Next three figurespresent the comparison of the X-ray spectra from combinedX -pinches from W and Mo wires, in particular from the twistedconfiguration of the wire load on COBRA and planar-loop wire

loads on ZEBRA.All X-ray spectra were recorded on the Kodak BIOMAX MSfilm by convex crystal spectrometers with a mica crystal (2d =19.93 Å) on COBRA and with a KAP crystal (2d = 26.63 Å)on ZEBRA. In [7] a comparison of X-ray spectra from 4-wiretwisted combined [W, Mo] and Mo X -pinches produced onCOBRA was shown that clearly indicates the contribution of the W radiation from 5.4 to 6 Å. In Fig. 3, a comparison of X-ray spectra from combined [W, Mo] X -pinches on COBRAand W/Mo on ZEBRA is presented in the first order of reflection from the crystals. It indicates more intense L-shellMo radiation for ZEBRA and more intense M-shell W radiationfor COBRA. Then, we can conclude that a use of a twisted

wire load (which increases the area as well as the mass of wirecontact at a cross point) produces more M-shell W radiation.

Fig. 4. Comparison of X-ray spectra recorded by a KAP crystal spectrom-

eter from two identical two-wire planar-loop asymmetrical combined W/MoX-pinches produced on ZEBRA.

Fig. 5. Comparison of X-ray spectra recorded by a KAP crystal from twotwo-wire planar-loop asymmetrical combined W/Mo and Mo/W X-pinchesproduced on ZEBRA. The two strong lines labeled Lα and Lβ are the “cold”characteristic Mo lines.

From Fig. 4, it is seen that X-ray spectra from two identicalW/Mo X -pinches on ZEBRA (shots 472 and 473) have almostidentical L-shell Mo and M-shell W spectra with slightlymore intense L-shell Mo radiation and less intense W M-shellradiation for 472 pulse. We included this figure to show thegood reproducibility of the studied spectra produced by thisparticular pulse power device.

By contrast, a comparison of X-ray spectra from W/Mo andMo/W X -pinches in Fig. 5 shows much larger differences.For example, L-shell Mo radiation from the Mo/W X -pinch ismuch weaker than that from the W/Mo X -pinch and includestwo very strong “cold” characteristic Lα and Lβ Mo lines. Thelatter evidences the presence of strong electron beams in the

plasma from the top loop wire material and correlates withthe characteristic lines in spectra registered by a LiF crystal




Fig. 6. Axially resolved X-ray spectra recorded by a KAP crystal through a 500-µm slit from the two-wire planar-loop asymmetrical combined W/Mo X-pinchproduced on ZEBRA.

(see Fig. 2). On contrary, M-shell W radiation is almostidentical in both spectra and hence is not sensitive to thechange of the material in the top loop.

The last figure with experimental data in this section, Fig. 6,presents the axially resolved X-ray spectra from the W/MoX -pinch with lineouts taken closer to the anode side, in themiddle, and closer to the cathode side of the

X -pinch. This

figure illustrates the difference in spectra and hence in modeledplasma parameters in the axial direction. This figure clearlyshows that for the W/Mo X -pinch with a W wire in the anodeloop and with the Mo wire in the cathode loop, the most intenseM-shell W and the less intense L-shell Mo spectra are recordedcloser to the anode side. In particular, this axially resolvedspectrum provides the best quality M-shell W spectrum outof all spectra for combined W and Mo X -pinches. The mostintense structure of M-shell W is located between 5.4 and 6.2 Å.The identification of features in this spectral region is basedon the theoretical atomic data from [9], Lawrence LivermoreNational Laboratory (LLNL) electron-beam ion trap (EBIT)

data [10], and our recently developed W model [7]. The featuresare associated with 3d → 4f transitions in Co-, Ni-, Cu-, and

Zn-like ions with the most intense Ni-like line at 5.689 Å. Inaddition, two well-resolved Ni-like W 3d → 4p transitions arelocated at 7.027 and 7.174 Å. The axially resolved spectrumfrom the middle has both L-shell Mo (2-3) and M-shell W(3-4) spectra of comparable intensity. Note that the previouslydiscussed and compared spectra from 472 and 473 pulses on

ZEBRA (Figs. 3–5) were radially resolved spectra, which aresimilar to the axially resolved spectra from the middle of theX -pinch. The axially resolved spectrum closer to the cathodeside shows more intense and clearly identified L-shell Moradiation and less intense M-shell radiation. The modeling of this L-shell Mo spectrum is discussed in the next section.

III. NON LOCAL THERMODYNAMIC EQUILIBRIUM (LTE)KINETIC MODELING OF RADIATION FROM

COMBINED W AN D MO X -P INCHES

The Mo model employed in this paper was developed andpreviously used to analyze experimental L-shell Mo spectra

from 1-MA ZEBRA X -pinches at UNR [5], [11], [12], from470 kA XP X -pinches at CU [11], [13] and from 20-MA Z




Fig. 7. Two synthetic L-shell Mo spectra calculated at (1) T e = 880 eV,N e = 1021 cm−3, and f = 0.1 and at (2) T e = 880 eV, N e = 8×

1020 cm−3, and f = 0.05.

wire arrays at SNL [11], [14], [15]. The spectral region from4.3 to 5.3 Å labeled as “Mo 2-3” in Fig. 6 has been modeled andused to derive plasma parameters, the electron temperature T e,electron density N e and the fraction of energetic electrons f inthe plasma distribution function. This spectral region includesmostly 2-3 L-shell Mo transitions together with some 3-5M-shell W transitions from 4.3 to 4.6 Å. Fig. 7 shows syntheticspectra of 2-3 L-shell Mo transitions in a spectral region from4.2 to 5.3 Å along with the most diagnostically important

spectral lines and structures. They are Ne-like lines (3A-3G),and F-like (F1) and Na-like (Na1 and Na2) line structures.In general, the Na1 and Na2 line structures comparable inintensity with 3C and 3D lines indicate electron temperaturesmuch lower and the F1 lines structure comparable in intensitieswith 3A and 3B lines much higher than 1000 eV at moderatedensities of 1020−1021 cm−3. Hence, the intense Na-like andF-like line structures cannot coexist in one spectrum unlessthey are produced by different radiation sources and/or hotelectrons. It was shown that the hot electrons even in smallconcentration up to few percent not only tend to increase theionization balance but also spread it over lager number of

ions [5], [11]. The time-gated spectra will be very helpful todetermine whether there are multiple radiation sources gener-ated in different times. Here, we have analyzed the experimentaltime integrated, spatially resolved spectra assuming first thatthey are radiated by one plasma with a given temperature anddensity together with a small fraction of the hot electronsand then, if necessary, adding the second radiation source.Previously, it was shown [11] and [16] that most collisionalrates are much more sensitive to f that to exact functional formor characteristic energy ε0 of the hot electrons as long as ε0 >∆E (where ∆E is the largest transition energy). Therefore,the results of collisional-radiative models are also much moresensitive to f than to the other characteristics of the hot electron

distribution. Then, line spectra can be used to detect only thepresence and approximate number of the hot electrons. To de-

Fig. 8. Spectral features from 4.3 to 5.3 Å from the ZEBRA W/Mo X-pinch

fit with the sum from two L-shell Mo sources from the previous figure.

termine the other characteristics of the hot electron distribution,soft and hard X-ray spectropolarimetry can be used, which isnot the subject of this paper. In this paper, the hot electronsof fraction f were described by a narrow Gaussian distributioncentered at the characteristic energy ε0 = 10 keV and hence thecondition ε0 > ∆E was satisfied. Two synthetic spectra calcu-lated at the same T e = 880 eV but at different electron densitiesN e and fractions of the hot electrons f are given in Fig. 7. Inparticular, the first L-shell Mo spectrum (1) was calculated atN e = 1021 cm−3 and f = 0.1, whereas the second one (2) wascalculated at N e = 8× 1020 cm−3 and f = 0.05, was shifted

0.04 Å to the right from (1) and is labeled with a prime. Thesum of these two synthetic spectra represents the best fit for theexperimental radially resolved spectrum from combined W/MoX -pinches produced in ZEBRA pulse 473 (see Fig. 8). Wehave also modeled the most intense L-shell Mo axially resolvedspectrum taken closer to the cathode side (see Fig. 6). Thisspectrum has the minimum contribution from 3-5 transitionsof M-shell W in the vicinity of 3A and 3B lines (∼4.4 Å)which allows an estimate of the electron density using the ratio(3A + 3B)/(3F + 3G). This ratio almost independent from T eand f up to densities N e = 1022 cm−3 and higher [5], [11]was about 0.45, which indicates N e ∼ (7−8)× 1021 cm−3.

Then, the best fit of the axially resolved spectrum closer to thecathode side indicates T e = 850 eV, N e = 8 × 1020 cm−3, andf = 0.1 based on a single radiation source (see Fig. 9). Theseparameters are close to the parameters of the two radiationsources derived from the modeling of the radially resolvedspectra (see Figs. 7 and 8).

IV. CONCLUSION

Combined X -pinches with W and Mo wires connectedthrough planar-loop and twisted load configurations have beenstudied through X-ray spectroscopy and imaging on two similar1-MA University-scale Z -pinch devices. Altogether the data

from three shots with twisted combined [W, Mo] X -pinchesfrom COBRA and four shots with planar-loop combined W/Mo




Fig. 9. Spectral features from 4.3 to 5.3 Å from the ZEBRA W/Mo

X-pinch axially resolved spectra near the cathode side (black) fit with theL-shell Mo spectrum (grey) calculated at T e = 850 eV, N e = 8×

1020 cm−3, and f = 0.1.

and Mo/W X -pinches from ZEBRA, were collected and therepresentative example for each different load has been shown.The mixture of W with another lighter wire material withknown radiative characteristics in such load configurations pro-duces better quality and resolution M-shell W spectra includingradial and axial resolution. Future work will involve furtherexperiments with combined X -pinches with different W andMo mass contributions and time-gated spectroscopy.

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Alla S. Safronova (M’06) was born in Moscow,Russia. She received the Ph.D. degree in physicsfrom the Institute of General Physics of RussianAcademy of Science (RAS), Moscow, in 1986.

From 1979 to 1981, she was a Graduate Student atthe P.N. Lebedev Physical Institute of RAS, Moscow.From 1982 to 1994, she was a Junior Researcher andthen a Senior Researcher in several Russian scientificresearch institutions in Moscow. From 1994 to 1998,she was first a Visiting Scientist and then a Post-doctoral Research Associate with the Department

of Physics, University of Nevada, Reno, where she has been an AssociateResearch Professor since 1998. She is one of the pioneers in applicationof X-ray line polarization to astrophysical and laboratory plasmas. She haspublished more than 100 papers in scientific journals. Her current researchinterests include modeling of hot dense plasmas and theoretical spectroscopyand spectropolarimetry of wire array and X-pinch plasmas.

Victor L. Kantsyrev (M’06) was born in Moscow,Russia. He received the M.S. and Ph.D. degrees inexperimental physics from Moscow Physical Engi-

neering Institute, in 1972 and 1981, respectively, andthe advanced degree of Dr. Sc. (Dr. Habil. degree inEurope) from the Institute of Analytical Instrumen-tation, Russian Academy of Science, St. Petersburg,in 1992.

From 1972 to 1994, he has been a Researcher,Senior Researcher, Head of a Sector, and Head of Laboratory in several Russian scientific research in-

stitutes in Moscow. From 1994 to 1995, he was a Visiting Scientist and Lecturerwith the Department of Physics, University of Nevada, Reno, where he hasbeen a Research Professor since 1996. He was one of the pioneers in thestudy and development of X-ray and extreme UV glass capillary optics, andthe development of compact laser and gas-puff plasma X-ray sources and theirapplications in X-ray lithography and microscopy. He has published more than150 papers in scientific journals on physics and radiation properties of Z -pinchand laser plasmas and plasma diagnostics. His current research interests include

the physics of wire array and X-pinch plasmas.Dr. Kantsyrev chaired the sessions at the International Society for OpticalEngineers and International Conference on Plasma Science (ICOPS) meetings.




Dmitry A. Fedin was born in Moscow, Russia, in1965. He received the M.S. degree in solid-statephysics and photonics from Moscow Physical En-gineering Institute, Moscow, and the Ph.D. degreein physics from the University of Nevada, Reno,in 2004.

He is currently a Postdoctoral Researcher withthe Center of Energy Research, Department of Me-

chanical and Aerospace Engineering, University of California, San Diego. His research interests includeexperimental plasma physics with the emphasis onsoft and hard X-ray plasma diagnostics.

Glenn Osborne was born in Walnut Creek, CA,on April 28, 1982. He received the B.S. degreein physics from the University of Nevada, Reno,in 2005. He is currently working toward the Ph.D.degree at the University of Nevada, where he isinvolved in theoretical and experimental work onX-ray spectroscopy of Z - and X-pinches.

M. Fatih Yilmaz was born in Kirikkale, Turkey, onNovember 8, 1977. He received the B.S. degree inphysics from the University of Balkesir, Balkesir,Turkey.

Since 2002, he has been a Graduate Student atthe Physics Department, University of Nevada, Reno(UNR). He is working on modeling of radiation fromZ -pinch and X-pinch plasmas, and magnetohydro-dynamic (MHD).

Travis Hoppe, photograph and biography not available at the time of publication.

Vidya Nalajala received the Diploma in electronicsand instrumentation from the Government Instituteof Electronics, Secunderabad, India, in 1999, theB.S. degree in electronics and communication engi-neering from Acharya Nagarjuna University, GunturCity, India, in 2002,and the M.S. degree with a majorin electrical engineering and a minor in physics from

the University of Nevada, Reno (UNR), in 2004, withemphasis on data acquisition and control systems,core diagnostics, energy measurements and analysis,and data processing and statistical analysis for the

UNR Physics experimental facilities, namely Sparky and Zebra.She is currently with UNR.

Jonathan D. Douglass received the B.S. degree inelectrical engineering from the University of Mis-souri, Columbia, in 2003, and is currently workingtoward the Ph.D. degree in electrical and computerengineering at Cornell University, Ithaca, NY. Hisdissertation focuses on the topic of time-gated mono-chromatic X-ray imaging of wire array Z -pinchesusing X-pinches as an X-ray source.

Ryan D. McBride received the B.S. degree fromBinghamton University, the State University of NewYork, Binghamton, in 2000, and the M.E. degreefrom Cornell University, Ithaca, NY, in 2001, allin electrical engineering. He is currently workingtoward the Doctor of Philosophy degree in electricalengineering, with a specialization in plasma physics,at the Laboratory of Plasma Studies at CU.

He worked as an Electrical Engineer at IBM from2001–2002. He is currently with the Laboratory of Plasma Studies, CU. His current work investigates

processes related to the formation of high-energy-density plasmas, specifically

those produced by wire-array Z -pinch and/or X-pinch sources.

Marc D. Mitchell (M’00) received the B.S. degreesin electrical engineering and physics from the Uni-versity of Evansville, Evansville, IN, in 2000, andthe M.S. degree in applied physics from CornellUniversity (CU), Ithaca, NY, in 2004. He is currentlyworking toward the Ph.D. degree at CU, focusing onthe characterization of X-pinch properties includingcoronal plasma density measurements using a laserinterferometer.

His research interests include high-energy plasmaphysics, laser and X-ray optics, X-ray diagnostics,

plasma diagnostics, and pulsed power.

Lloyd M. Maxson, photograph and biography not available at the time of publication.

David A. Hammer (M’78–SM’79–F’95) receivedthe B.S. degree in physics from the California Insti-tute of Technology, Pasadena, in 1964 and the Ph.D.degree in applied physics from Cornell University,Ithaca, NY, in 1969. His dissertation was on the topicof intense relativistic electron beam propagation.

After seven years at the Naval Research Labora-tory, Washington, DC, and one year at Universityof California, Los Angeles, he returned to CornellUniversity as a Faculty Member. He is currently theJ. Carlton Ward Professor of Nuclear Engineering

and a Professor of electrical and computer engineering at Cornell University.His research is focused on high-energy-density plasma physics, includingexploding wires, wire array Z -pinches and X-pinches.

Dr. Hammer is a Fellow of the American Physical Society (APS) and theAmerican Association for the Advancement of Science, and he has served asthe Chair of the Division of Plasma Physics, APS.

Alla S. Safronova et al- Spectroscopic and Imaging Study of Combined W andMo X-Pinches at 1 MA...

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