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W A Stygar,
M E Cuneo,
R A Vesey,
H C Ives,
M G Mazarakis,
G A Chandler,
D L Fehl,
R J Leeper,
M K Matzen,
D H McDaniel, [......],
J L Porter,
J J Ramirez, J F Seamen,
C S Speas,
R B Spielman,
K W Struve,
J A Torres,
E M Waisman,
T C Wagoner,
T L Gilliland
[show abstract]
[hide abstract]
ABSTRACT: We have developed wire-array z -pinch scaling relations for plasma-physics and inertial-confinement-fusion (ICF) experiments. The relations can be applied to the design of z -pinch accelerators for high-fusion-yield (approximately 0.4 GJ/shot) and inertial-fusion-energy (approximately 3 GJ/shot) research. We find that (delta(a)/delta(RT)) proportional (m/l)1/4 (Rgamma)(-1/2), where delta(a) is the imploding-sheath thickness of a wire-ablation-dominated pinch, delta(RT) is the sheath thickness of a Rayleigh-Taylor-dominated pinch, m is the total wire-array mass, l is the axial length of the array, R is the initial array radius, and gamma is a dimensionless functional of the shape of the current pulse that drives the pinch implosion. When the product Rgamma is held constant the sheath thickness is, at sufficiently large values of m/l, determined primarily by wire ablation. For an ablation-dominated pinch, we estimate that the peak radiated x-ray power P(r) proportional (I/tau(i))(3/2)Rlphigamma, where I is the peak pinch current, tau(i) is the pinch implosion time, and phi is a dimensionless functional of the current-pulse shape. This scaling relation is consistent with experiment when 13 MA < or = I < or = 20 MA, 93 ns < or = tau(i) < or = 169 ns, 10 mm < or = R < or = 20 mm, 10 mm < or = l < or = 20 mm, and 2.0 mg/cm < or = m/l < or = 7.3 mg/cm. Assuming an ablation-dominated pinch and that Rlphigamma is held constant, we find that the x-ray-power efficiency eta(x) congruent to P(r)/P(a) of a coupled pinch-accelerator system is proportional to (tau(i)P(r)(7/9 ))(-1), where P(a) is the peak accelerator power. The pinch current and accelerator power required to achieve a given value of P(r) are proportional to tau(i), and the requisite accelerator energy E(a) is proportional to tau2(i). These results suggest that the performance of an ablation-dominated pinch, and the efficiency of a coupled pinch-accelerator system, can be improved substantially by decreasing the implosion time tau(i). For an accelerator coupled to a double-pinch-driven hohlraum that drives the implosion of an ICF fuel capsule, we find that the accelerator power and energy required to achieve high-yield fusion scale as tau(i)0.36 and tau(i)1.36, respectively. Thus the accelerator requirements decrease as the implosion time is decreased. However, the x-ray-power and thermonuclear-yield efficiencies of such a coupled system increase with tau(i). We also find that increasing the anode-cathode gap of the pinch from 2 to 4 mm increases the requisite values of P(a) and E(a) by as much as a factor of 2.
Physical Review E 09/2005; 72(2 Pt 2):026404. · 2.26 Impact Factor
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M. Keith Matzen,
M. A. Sweeney,
R. G. Adams,
J. R. Asay,
J. E. Bailey,
G. R. Bennett,
D. E. Bliss,
D. D. Bloomquist,
T. A. Brunner,
R. B. Campbell, [......], J. F. Seamen,
D. B. Sinars,
S. A. Slutz,
I. C. Smith,
K. W. Struve,
W. A. Stygar,
R. A. Vesey,
E. A. Weinbrecht,
D. F. Wenger,
E. P. Yu
[show abstract]
[hide abstract]
ABSTRACT: The Z accelerator [
R. B. Spielman, W. A. Stygar, J. F. Seamen et al., Proceedings of the 11th International Pulsed Power Conference, Baltimore, MD, 1997, edited by G. Cooperstein and I. Vitkovitsky (IEEE, Piscataway, NJ, 1997), Vol. 1, p. 709
] at Sandia National Laboratories delivers ∼ 20 MA load currents to create high magnetic fields (>1000 T) and high pressures (megabar to gigabar). In a z-pinch configuration, the magnetic pressure (the Lorentz force) supersonically implodes a plasma created from a cylindrical wire array, which at stagnation typically generates a plasma with energy densities of about 10 MJ/cm3 and temperatures >1 keV at 0.1% of solid density. These plasmas produce x-ray energies approaching 2 MJ at powers >200 TW for inertial confinement fusion (ICF) and high energy density physics (HEDP) experiments. In an alternative configuration, the large magnetic pressure directly drives isentropic compression experiments to pressures >3 Mbar and accelerates flyer plates to >30 km/s for equation of state (EOS) experiments at pressures up to 10 Mbar in aluminum. Development of multidimensional radiation-magnetohydrodynamic codes, coupled with more accurate material models (e.g., quantum molecular dynamics calculations with density functional theory), has produced synergy between validating the simulations and guiding the experiments. Z is now routinely used to drive ICF capsule implosions (focusing on implosion symmetry and neutron production) and to perform HEDP experiments (including radiation-driven hydrodynamic jets, EOS, phase transitions, strength of materials, and detailed behavior of z-pinch wire-array initiation and implosion). This research is performed in collaboration with many other groups from around the world. A five year project to enhance the capability and precision of Z, to be completed in 2007, will result in x-ray energies of nearly 3 MJ at x-ray powers >300 TW.
Physics of Plasmas 05/2005; 12(5):055503-055503-16. · 2.15 Impact Factor
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W A Stygar,
H C Ives,
D L Fehl,
M E Cuneo,
M G Mazarakis,
J E Bailey,
G R Bennett,
D E Bliss,
G A Chandler,
R J Leeper, [......],
T L Gilliland,
M L Horry,
D O Jobe,
S E Lazier,
J A Mills,
T D Mulville,
J H Pyle,
T M Romero,
J J Seamen,
R M Smelser
[show abstract]
[hide abstract]
ABSTRACT: We have measured the x-ray power and energy radiated by a tungsten-wire-array z pinch as a function of the peak pinch current and the width of the anode-cathode gap at the base of the pinch. The measurements were performed at 13- and 19-MA currents and 1-, 2-, 3-, and 4-mm gaps. The wire material, number of wires, wire-array diameter, wire-array length, wire-array-electrode design, normalized-pinch-current time history, implosion time, and diagnostic package were held constant for the experiments. To keep the implosion time constant, the mass of the array was increased as I2 (i.e., the diameter of each wire was increased as I), where I is the peak pinch current. At 19 MA, the mass of the 300-wire 20-mm-diam 10-mm-length array was 5.9 mg. For the configuration studied, we find that to eliminate the effects of gap closure on the radiated energy, the width of the gap must be increased approximately as I. For shots unaffected by gap closure, we find that the peak radiated x-ray power P(r) proportional to I1.24+/-0.18, the total radiated x-ray energy E(r) proportional to I1.73+/-0.18, the x-ray-power rise time tau(r) proportional to I0.39+/-0.34, and the x-ray-power pulse width tau(w) proportional to demonstrate that the internal energy and radiative opacity of the pinch are not responsible for the observed subquadratic power scaling. Heuristic wire-ablation arguments suggest that quadratic power scaling will be achieved if the implosion time tau(i) is scaled as I(-1/3). The measured 1sigma shot-to-shot fluctuations in P(r), E(r), tau(r), tau(w), and tau(i) are approximately 12%, 9%, 26%, 9%, and 2%, respectively, assuming that the fluctuations are independent of I. These variations are for one-half of the pinch. If the half observed radiates in a manner that is statistically independent of the other half, the variations are a factor of 2(1/2) less for the entire pinch. We calculate the effect that shot-to-shot fluctuations of a single pinch would have on the shot-success probability of the double-pinch inertial-confinement-fusion driver proposed by Hammer et al. [Phys. Plasmas 6, 2129 (1999)]. We find that on a given shot, the probability that two independent pinches would radiate the same peak power to within a factor of 1+/-alpha (where 0< or =alpha<1) is equal to erf(alpha/2sigma), where sigma is the 1sigma fractional variation of the peak power radiated by a single pinch. Assuming alpha must be < or =7% to achieve adequate odd-Legendre-mode radiation symmetry for thermonuclear-fusion experiments, sigma must be <3% for the shot-success probability to be > or =90%. The observed (12/2(1/2))%=8.5% fluctuation in P(r) would provide adequate symmetry on 44% of the shots. We propose that three-dimensional radiative-magnetohydrodynamic simulations be performed to quantify the sensitivity of the x-ray emission to various initial conditions, and to determine whether an imploding z pinch is a spatiotemporal chaotic system.
Physical Review E 04/2004; 69(4 Pt 2):046403. · 2.26 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The quality of high wire-number z-pinch implosions on Z using a dynamic-hohlraum configuration is significantly affected by the method of holding the wires. The two arrangements discussed here have led to differences of a factor of 1.6±0.2 in radial x-ray power, where the higher power is produced by the holder with the superior current contact at the cathode. In support of this observation, single exploding wire data taken on a 250-ns pulser indicate that improved wire-electrode contact at the cathode permits greater energy delivery to the wire prior to current shunting to surrounding wire-plasma corona.
Pulsed Power Conference, 2003. Digest of Technical Papers. PPC-2003. 14th IEEE International; 07/2003
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R.J. Leeper,
T.E. Alberts,
J.R. Asay,
P.M. Baca,
K.L. Baker,
S.P. Breeze,
G.A. Chandler,
D.L. Cook,
G.W. Cooper,
C. Deeney, [......],
M. Vargas,
T.C. Wagoner,
C. Wakefield,
J.H. Hammer,
D.D. Ryutov,
M. Tabak,
S.C. Wilks,
R.L. Bowers,
K.D. McLenithan,
D.L. Peterson
[show abstract]
[hide abstract]
ABSTRACT: Three hohlraum concepts are being pursued at Sandia National Laboratories (SNL) to investigate the possibility of using pulsed power driven magnetic implosions (Z pinches) to drive targets capable of fusion yields in the range 200-1000 MJ. This research is being conducted on SNL's Z facility, which is capable of driving peak currents of 20 MA in various Z pinch load configurations that produce implosion velocities as high as 7.5 × 107cm/s, X ray energies of 1-2 MJ and X ray powers of 100-250 TW. The first concept, denoted dynamic hohlraum, has achieved a temperature of 180 ± 14 eV in a configuration suitable for driving capsules. In addition, this concept has also achieved a temperature of 230 ± 18 eV in an arrangement suitable for driving an external hohlraum. The second concept, denoted static walled hohlraum, has achieved temperatures of ~80-100 eV. Experimental investigation of the third concept, denoted Z pinch driven hohlraum, has recently begun. The article discusses each of these hohlraum concepts and provides an overview of the experiments that have been conducted on these systems to date.
Nuclear Fusion 05/2002; 39(9Y):1283. · 4.09 Impact Factor
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T.W.L. Sanford,
R.E. Olson,
G.A. Chandler,
D.L. Fehl,
J.S. Lash,
R.J. Leeper,
L. Ruggles,
K.W. Struve,
R.A. Vesey,
M.S. Derzon, [......],
R.C. Mock,
D.E. Hebron,
T.L. Gilliland,
D.O. Jobe,
J S McGurn, J.F. Seamen,
W. Simpson,
J A Torres,
M.F. Vargars,
D.L. Peterson
[show abstract]
[hide abstract]
ABSTRACT: Summary form only given. Implosion and ignition of an indirectly-driven ICF capsule operating near a Fermi-degenerate isentrope requires initial Planckian-radiation-drive temperatures of 70-to-90 eV to be present for a duration of 10-to-15 ns prior to the main drive pulse. Such capsules are being designed for high pulsed-power generators such as X1. This foot-pulse drive capability has been recently demonstrated in a NIF-sized (φ=6-mm 1=7-mm), gold hohlraum, using a one-sided static-wall hohlraum geometry on the Z generator. The general arrangement utilized nested tungsten-wire arrays of radii (mass) 20 mm (2 mg) and 10 mm (1 mg) that had an axial length of -10 mm. The arrays were driven by a peak current of -21 MA and were made to implode on a 2-μm-thick Cu annulus (mass=4.5 mg), which had a radius of 4 mm and was filled with a low-density CH foam, all centered about the z-axis. The gold hohlraum was mounted on axis and above the Cu/foam target. A 2.9-mm-radius axial hole between the top of the target and hohlraum permitted the X-rays generated from the implosion to enter the hohlraum. The radiation within the hohlraum was monitored by viewing the hohlraum through a 3-mm diameter hole on the lateral side of the hohlraum with a suite of diagnostics. The radiation entering the hohlraum was estimated by an additional suite of on-axis diagnostics, in a limited number of separate shots, when the hohlraum was not present. Additionally, the radiation generated outside the Cu annulus was monitored, for all shots, through a 3-mm diameter aperture located on the outside of the current return can
Plasma Science, 1999. ICOPS '99. IEEE Conference Record - Abstracts. 1999 IEEE International Conference on; 02/1999
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W.A. Stygar,
R.B. Spielman,
R.A. Anderson,
R.E. Clark,
J.W. Douglas,
T.L. Gilliland,
M.L. Horry,
T.P. Hughes,
H.C. Ives,
F.W. Long, [......],
D.H. McDaniel,
O. Milton,
M.A. Mostrom, J.F. Seamen,
R.W. Shoup,
J.W. Smith,
K.W. Struve,
G.E. Vogtlin,
T.C. Wagoner,
O. Yamamoto
[show abstract]
[hide abstract]
ABSTRACT: We have demonstrated operation of a 3.35-m-diameter insulator stack at 158 kV/cm with no total-stack flashovers on five consecutive Z-accelerator shots. The stack consisted of five +45/spl deg/-profile 5.715-cm-thick crosslinked-polystyrene (Rexolite-1422) insulator rings, and four anodized-aluminum grading rings shaped to reduce the field at cathode triple junctions. The width of the voltage pulse at 89% of peak was 32 ns. We compare this result to a new empirical flashover relation developed from previous small-insulator experiments conducted with flat unanodized electrodes. The relation predicts a 50% flashover probability for a Rexolite insulator during an applied voltage pulse when E/sub max/e/sup -0.27/d/(t/sub eff/C)/sup 1/10/=224, where E/sub max/ is the peak mean electric field (kV/cm), d is the insulator thickness (cm), t/sub eff/ is the effective pulse width (/spl mu/s), and C is the insulator circumference (cm). We find the Z stack can be operated at a stress at least 19% higher than predicted. This result, together with previous experiments conducted by Vogtlin, suggest anodized electrodes with geometries that reduce the field at both anode and cathode triple junctions would improve the flashover strength of multi-stage insulator stacks.
Pulsed Power Conference, 1999. Digest of Technical Papers. 12th IEEE International; 02/1999
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M K Matzen,
C Deeney,
R J Leeper,
J L Porter,
R B Spielman,
G A Chandler,
M S Derzon,
M R Douglas,
D L Fehl,
D E Hebron,
T J Nash,
R E Olson,
L E Ruggles,
T W L Sanford, J F Seamen,
K W Struve,
W A Stygar,
D L Peterson
[show abstract]
[hide abstract]
ABSTRACT: As a result of advances in fast pulsed-power technology and cylindrical load fabrication, the Z pulsed-power accelerator at Sandia National Laboratories drives currents approaching 20 MA with a rise time of approximately 100 ns through cylindrically-symmetric loads (typically a cylindrical array consisting of a few hundred wires) to produce plasma densities in excess of , x-ray output energies approaching 2 MJ, radiation pulses as short as 4 ns and peak x-ray powers as high as . More than 15% of the stored electrical energy in the Z pulsed-power accelerator is converted into x-rays. The plasma pressures at peak compression are several TPa with electron temperatures that can exceed 3 keV at containment magnetic fields exceeding 1000 T. Depending on the atomic number and composition of the imploding plasma, these z-pinches can be tailored to produce intense sources of thermal x-rays, keV x-rays or neutrons. Although applications of these x-ray sources have included research in radiation material interaction, equations of state, opacity, astrophysics and x-ray lasers, the principal focus of the present research is to use them for indirect-drive inertial confinement fusion (ICF).
Plasma Physics and Controlled Fusion 12/1998; 41(3A):A175. · 2.42 Impact Factor
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J. P. Apruzese,
P. E. Pulsifer,
J. Davis,
R. W. Clark,
K. G. Whitney,
J. W. Thornhill,
T. W. L. Sanford,
G. A. Chandler,
C. Deeney,
D. L. Fehl, [......],
R. B. Spielman,
W. A. Stygar,
K. W. Struve,
R. C. Mock,
T. L. Gilliland,
D. O. Jobe,
J. S. McGurn, J. F. Seamen,
J. A. Torres,
M. Vargas
[show abstract]
[hide abstract]
ABSTRACT: Al:Mg alloy wire arrays of mass loads 1.3–3.6 mg/cm have been imploded with peak currents of 19 MA on the 60 TW Z generator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories. The large mass loads have resulted in the highest K-shell x-ray line optical depths ( ∼ 103) produced to date in Z-pinches. Analysis of the time-resolved spectrum of a 2.1 mg/cm shot near the time of peak compression has yielded a temperature–density profile of the pinch that approximately reproduces all features of the x-ray data except the continuum above 5 keV, which is underpredicted. The Ly α/He α ratio for Al is shown to be enhanced relative to that of Mg by two mechanisms: photopumped ladder ionization and absorption of the Al He-like line in a cool outer halo. This analysis and comparisons to some Ti shots demonstrates that the K-shell yield of Al is significantly reduced by line and continuum self-absorption, but that of Ti is not. © 1998 American Institute of Physics.
Physics of Plasmas 11/1998; 5(12):4476-4483. · 2.15 Impact Factor
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T.W.L. Sanford,
R.B. Spielman,
G.O. Allshouse,
G.A. Chandler,
D.L. Fehl,
W.A. Stygar,
K.W. Struve,
C. Deeney,
T.J. Nash, J.F. Seamen,
R.C. Mock,
T.L. Gilliland,
J.S. McGurn,
D.O. Jobe
[show abstract]
[hide abstract]
ABSTRACT: Doubling the number of tungsten wires from 120 to 240, keeping the
mass fixed, increased the radiated X-ray power relative to the
electrical power at the insulator stack of the Z accelerator by
(35±15)% for 8.75- and 20-mm radii Z-pinch wire arrays.
One-dimensional radiation magneto hydrodynamic calculations suggest that
the arrays were operating in a quasi “plasma-shed” regime,
where the plasma generated by the individual wires partially merge prior
to the inward implosion of the entire array
IEEE Transactions on Plasma Science 09/1998; · 1.17 Impact Factor
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R. B. Spielman,
C. Deeney,
G. A. Chandler,
M. R. Douglas,
D. L. Fehl,
M. K. Matzen,
D. H. McDaniel,
T. J. Nash,
J. L. Porter,
T. W. L. Sanford, [......],
J. S. McGurn,
J. A. Torres,
D. M. Zagar,
T. L. Gilliland,
D. O. Jobe,
J. L. McKenney,
R. C. Mock,
M. Vargas,
T. Wagoner,
D. L. Peterson
[show abstract]
[hide abstract]
ABSTRACT: Here Z, a 60 TW/5 MJ electrical accelerator located at Sandia National Laboratories, has been used to implode tungsten wire-array Z pinches. These arrays consisted of large numbers of tungsten wires (120–300) with wire diameters of 7.5 to 15 μm placed in a symmetric cylindrical array. The experiments used array diameters ranging from 1.75 to 4 cm and lengths from 1 to 2 cm. A 2 cm long, 4 cm diam tungsten array consisting of 240, 7.5 μm diam wires (4.1 mg mass) achieved an x-ray power of ∼ 200 TW and an x-ray energy of nearly 2 MJ. Spectral data suggest an optically thick, Planckian-like radiator below 1000 eV. One surprising experimental result was the observation that the total radiated x-ray energies and x-ray powers were nearly independent of pinch length. These data are compared with two-dimensional radiation magnetohydrodynamic code calculations. © 1998 American Institute of Physics.
Physics of Plasmas 04/1998; 5(5):2105-2111. · 2.15 Impact Factor
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J.P. Quintenz,
R.G. Adams,
G.O. Allshouse,
J.E. Bailey,
D.D. Bloomquist,
G.A. Chandler,
R.S. Coats,
D.L. Cook,
M.E. Cuneo,
C. Deeney, [......],
C.L. Ruiz,
T.W.L. Sanford, J.F. Seamen,
D.B. Seidel,
S.A. Slutz,
R.B. Spielman,
W.A. Stygar,
M.A. Sweeney,
R.A. Vesey,
D.F. Wenger
[show abstract]
[hide abstract]
ABSTRACT: The US Department of Energy has supported a substantial research
program in Inertial Confinement Fusion (ICF) since the early 1970s. Over
the ensuing 25 years, pulsed power approaches to inertial fusion have
remained of interest primarily because of the high energy, efficiency,
and relatively low cost of the technology when compared to the mainline
ICF approach involving large glass lasers. These compelling advantages,
however, have been tempered with the difficulty in concentrating the
energy in space and time to create the high energy and power density
required to achieve temperatures useful in indirect drive ICF. Since the
Beams '96 meeting, the situation has changed dramatically, and extremely
high X-ray power (290 TW) and energy (1.8 MJ) have been produced in fast
z-pinch implosions on the Z accelerator. These sources have been
utilized to heat hohlraums to >150 eV and have opened the door to
important ICF capsule experiments. Although light ion beams offer a long
term potential for fusion energy, we are suspending our ion beam
research this year to maximize progress with z pinches
High-Power Particle Beams, 1998. BEAMS '98. Proceedings of the 12th International Conference on; 02/1998
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[show abstract]
[hide abstract]
ABSTRACT: PBFA Z is a new 55 TW/4.5 MJ short pulse electrical driver located
at Sandia National Laboratories. We use PBFA Z to magnetically-implode
plasma shells. These configurations are historically known as Z pinches.
The pulsed power design of PBFA Z is based on conventional single-pulse
Marx generator, water-line pulse-forming technology used on the earlier
Saturn and PBFA II accelerators. PBFA Z stores 11.4 MJ in its 36 Marx
generators, couples 4.5 MJ in 55-TW/105-ns pulse to the output water
transmission lines, and delivers up to 3.0 MJ and 40 TW of electrical
energy to the Z-pinch load. Depending on the initial load inductance and
the implosion time, we attain peak currents of 16-20 MA with a rise time
of 105 ns. Current is fed to the Z-pinch load through self
magnetically-insulated transmission lines (MITLs). Peak electric fields
in the MITLs exceed 2 MV/cm. The current from the four independent
conical disk MITLs is combined together in a double post-hole vacuum
convolute with an efficiency greater than 95%. The measured system
performance of the water transmission lines, the vacuum insulator stack,
the MITLs, and the double post-hole vacuum convolute differed from
preshot predictions by ~5%. Using a 2-cm radius and a 2-cm length
tungsten wire array with 240, 7.5-μm diameter wires (4.1-mg mass) as
the Z-pinch load, we achieved X-ray powers of 200 TW and X-ray energies
of 1.85 MJ as measured by X-ray diodes and resistive bolometry
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
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C. Deeney,
J. McGurn,
D. Noack,
J. L. Porter,
R. B. Spielman, J. F. Seamen,
D. O. Jobe,
M. F. Vargas,
T. Gilliland,
M. R. Douglas,
M. K. Matzen
[show abstract]
[hide abstract]
ABSTRACT: A combination of a 400 ns, 300 mJ, 640 nm dye laser, and an optical streak camera have been used to demonstrate that time-resolved shadowgrams can be made of the implosion phase of tungsten wire arrays. Initial experiments have shown that mirror lifetime and spatial resolution are issues for this diagnostic technique. Nonetheless, these experiments have provided new information on wire array dynamics; specifically, they show that even with a 0.46 mm wire spacing, the high density regions formed by the wires, are separate until 30 ns into the main drive current. Peak currents of 6.6 MA were obtained 40 ns after the start of the current, while peak radiated powers of 85 TW were measured at 50 ns. © 1997 American Institute of Physics.
Review of Scientific Instruments 02/1997; · 1.37 Impact Factor
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T. W. L. Sanford,
T. J. Nash,
R. C. Mock,
R. B. Spielman, J. F. Seamen,
J. S. McGurn,
D. Jobe,
T. L. Gilliland,
M. Vargas,
K. G. Whitney,
J. W. Thornhill,
P. E. Pulsifer,
J. P. Apruzese
[show abstract]
[hide abstract]
ABSTRACT: Time-resolved x-ray pinhole photographs and time-integrated radially resolved x-ray crystal-spectrometer measurements of azimuthally symmetric aluminum-wire implosions suggest that the densest phase of the pinch is composed of a hot plasma core surrounded by a cooler plasma halo. The slope of the free-bound x-ray continuum, provides a time-resolved, model-independent diagnostic of the core electron temperature. A simultaneous measurement of the time-resolved K-shell line spectra provides the electron temperature of the spatially averaged plasma. Together, the two diagnostics support a one-dimensional radiation–hydrodynamic model prediction of a plasma whose thermalization on axis produces steep radial gradients in temperature, from temperatures in excess of 1 kV in the core to below 1 kV in the surrounding plasma halo. © 1997 American Institute of Physics.
Review of Scientific Instruments 02/1997; · 1.37 Impact Factor
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T.W.L. Sanford,
B.M. Marder,
R.B. Spielman,
T.J. Nash,
M. Douglas,
C. Deeney,
K. Struve,
R.C. Mock, J.F. Seamen,
J.S. McGurn, [......],
P.E. Pulsifer,
K.G. Whitney,
J. Davis,
S.L. Cochran,
K.G. Velikovich,
B.V. Weber,
G. Peterson,
D. Mosher,
J.S. De Groot,
J.H. Hammer
[show abstract]
[hide abstract]
ABSTRACT: Summary form only given. The radiation from uniform-fill argon gas
puffs on the Saturn accelerator with a 4.5-cm diameter nozzle are
compared with that generated from a previously optimized 2.5-cm diameter
annular nozzle. The pressure range of the uniform fill spanned 1300 to
2900 Torr and that of the annular nozzle was set to 1650 Torr-the
pressure that previously maximized the K-shell radiation yield. B-dot
monitors measured current in the MITLs and 4.5 cm upstream of the load.
A bolometer and duplicate sets of filtered XRDs and PCDs, spanning the
energy range of 200 eV to 6 keV, monitored the temporal characteristics
of the radiation. A suite of time-integrated and time-resolved,
filtered, fast-framing, X-ray pinhole cameras, and crystal spectrometers
monitored the spatial and spectral structure of the radiation. The
radial density profile of the initial gas profile was measured on a test
stand at NRL using a two-color interferometer
Plasma Science, 1996. IEEE Conference Record - Abstracts., 1996 IEEE International Conference on; 07/1996
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Pulsed Power Conference, 1993. Digest of Technical Papers. Ninth IEEE International; 07/1993
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Pulsed Power Conference, 1991. Digest of Technical Papers. Eighth IEEE International; 07/1991
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[show abstract]
[hide abstract]
ABSTRACT: We have developed a new multiple-stage laser-triggered SF/sub 6/ spark gap, which has performed well in tests at nearly 6 megavolts and half a megampere. It has survived many hundreds of shots between 5 and 5.7 MV, the highest voltage tested. A 25 millijoule ultraviolet laser pulse arriving in its trigger gap reliably closes the whole switch in 20 nanoseconds with 0.4 ns 1-sigma jitter. The closing time has a low dependence on the applied voltage, about 0.9 ns/% of self-break voltage. For a 10 mJ laser pulse, the jitter is 1.5 ns and the slope is 1.0 ns/%. No prefires have occurred; the estimated prefire rate at 90% of self-breaking voltage is less than 0.1%. The switch inductance is 400 nanohenries, of which about 100 nh comes from the spark channels. The switch is 68 cm long and 61 cm in diameter.
12/1984
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ABSTRACT: A single-module demonstration experiment for the Particle Beam Fusion Accelerator (PBFA-II) is nearing completion. The pulse-forming line for this module uses traveling wave charging, and the energy efficiency of the module varies from 22% for a 40 ns power pulse to 35% for a 55 ns power pulse. With a 370 KJ Marx generator, this module can deliver up to 130 KJ into a matched 2.2 ohm output line. 6 references, 6 figures, 2 tables.
12/1983
