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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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J.E. Bailey,
A.B. Filuk,
A.L. Carlson,
D.J. Johnson,
P. Lake, E.J. McGuire,
T.A. Mehlhorn,
T.D. Pointon,
T.J. Renk,
W.A. Stygar,
Y. Maron,
E. Stambulchik
[show abstract]
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ABSTRACT: Achieving inertial confinement fusion using a light-ion-beam driver requires continued improvement in understanding ion diode physics. The power delivered to a light-ion beam target is strongly influenced by the evolution of the charge-particle distributions across the ion beam acceleration gap. Our strategy is to determine this evolution from time- and space-resolved measurements of the electric field using Stark-shifted line emission. In addition to diode physics, the unique high-field (10 MV/cm, 6T) conditions in present experiments offer the possibility to advance basic atomic physics, for example by measuring field ionization rates for tightly bound low-principal-quantum-number levels. In fact, extension of atomic physics into the high-field regime is required for accurate interpretation of diode physics measurements. This paper describes progress in ion diode physics and basic atomic physics, obtained with visible-light atomic spectroscopy measurements in the 20 TW Particle Beam Fusion Accelerator II ion diode.
Laser and Particle Beams 11/1996; 14(04):543 - 553. · 1.62 Impact Factor
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J.P. Quintez,
R.G. Adams,
G.O. Allshouse,
L.D. Bacon,
J.E. Bailey,
D.D. Bloomquist,
G.A. Chandler,
R.S. Coats,
D.L. Cook,
M.E. Cuneo, [......],
R.P. Kensek,
M.L. Kiefer,
N.A. Krall,
R.J. Leeper,
T.R. Lockner,
J.E. Maenchen,
M.K. Matzen,
D.H. McDaniel, E.J. McGuire,
P.F. McKay
[show abstract]
[hide abstract]
ABSTRACT: Advances in ion beam theory, diagnostics, and experiments in the past two years have enabled efficient generation of intense proton beams on PBFA II and focusing of the beam power to 5.4 TW/cm{sup 2}. Improvements in the uniformity of the ion diode magnetic field and anode shaping produced a proton beam with good azimuthal symmetry. The beam was diagnosed using conical targets in concert with inner-shell excitation x-ray cameras and ion pinhole cameras. The measured asymmetry was less than 15 percent, a level adequate to begin initial studies of the beam/target interaction with proton beams. Substantial improvements in power density beyond the present level require an ion beam that is more magnetically stiff and has lower ion divergence. Thin-film-based lithium sources have produced more than 150 kJ of lithium energy above 6 MV. For the first 15 ns of the ion beam pulse, multiple diagnostics show a high purity lithium beam. Simulations using the three-dimensional electromagnetic particle-in-cell code QUICKSILVER have identified an early-time diocotron instability in the electron flow in the diode. Analytic calculations, which include a charge-neutral region in the diode inside the beam acceleration gap, give a growth rate for the diocotron instability that is in good agreement with the simulations. In the QUICKSILVER simulations, the early-time diocotron instability eventually gives way to a low-frequency instability with a period on the order of the ion beam transit-time'' time scale. When this occurs, the ion divergence increases substantially as a result of the enhanced coupling. Results from the ion diode simulations and analytic theory are discussed, as well as recent developments in diagnostics for the measurement of ion divergence.
12/1990
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J. Bailey,
A. L. Carlson,
G. Chandler,
M. S. Derzon,
R. J. Dukart,
B. A. Hammel,
D. J. Johnson,
T. R. Lockner,
J. Maenchen, E. J. McGuire,
T. A. Mehlhorn,
W. E. Nelson,
L. E. Ruggles,
W. A. Stygar,
D. F. Wenger
[show abstract]
[hide abstract]
ABSTRACT: We have made the first observation of Kα X-ray satellites from a target heated by an intense ion beam. The satellites are produced when thermal ionization due to beam heating is accompanied by inner-shell ionization from beam ion impact. The Particle Beam Fusion Accelerator II was used to irradiate a conical aluminum target with a proton beam. The nominal beam parameters were 50–75 kJ in a 1-cm spot, 15–20-ns pulse length, and 4–5-MeV protons at peak power. An elliptical crystal X-ray spectrograph inside a 1000-kg tungsten shield was used to record the spectra. The peak ion stage reached by the aluminum target was +8. Collisional radiative calculations were performed, which indicate a peak electron temperature of 20–60 eV.
Laser and Particle Beams 11/1990; 8(04):555 - 562. · 1.62 Impact Factor
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[show abstract]
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ABSTRACT: Designs are proposed, based on a series of one‐dimensional calculations, for layered, hollow cylindrical targets to be placed on the axis of an imploding, hollow Z‐pinch plasma that can create the approximate plasma conditions, as well as radiation spectrum, for a photoionization pumped, Ne‐like recombination laser. The lasant must reach the Ne‐like state and be at the appropriate density at the same time that the photoionizing pump radiation is present, placing severe constraints on designs for such targets. Target designs are further constrained by the fact that the 3s‐2p resonance line, which depopulates the lower lasing state, must not be highly trapped and by the fact that the upper lasing state must not be collisionally depopulated. We find that hollow, cylindrical targets consisting of a few‐micron‐thick CH strongback, coated on the inside with a thin layer of Ni lasant and on the outside with an Al converter layer, can be optimized to achieve appropriate conditions for lasing and modest levels of gain.
Journal of Applied Physics 12/1989; · 2.17 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Designs are proposed for layered, hollow cylindrical targets to be placed on the axis of an imploding, hollow Z-pinch plasma that can create the approximate plasma conditions, as well as radiation spectrum, for a photoionization pumped, Ne-like recombination laser. The lasant must research the Ne-like state and be at the appropriate density concurrent with the photoionizing pump radiation. This places severe constraints on designs for such targets with the vertical vacuum feed diode on Proto 2. Target designs are further constrained by the fact that the 3s--2p resonance line, which depopulates the lower lasing state, must not be highly trapped and by the fact that the upper lasing state must not be collisionally depopulated. We find that hollow, cylindrical targets consisting of a few micron CH strongback, coated on the inside with a thin layer of Ni lasant and on the outside with an Al converter layer, can be optimized to acheive appropriate conditions for lasing. We note that a trade-off exists between larger targets, which better isolate the target from the shock of stagnation, and smaller targets, which deliver a higher intensity pump flux. We also find that trapping, together with uncertainties in the inward expansion of the lasant layer, are significant, and may limit optium available gain. 30 refs., 22 figs., 1 tab.
04/1988;
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[show abstract]
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ABSTRACT: The heating of a planar multilayer (CH-Au-Al-CH) foil target by an intense lithium ion beam is measured using time-integrated spectroscopy of Kα x-ray satellite emission from the Al layer. The time-resolved beam irradiance, kinetic energy, and focal spot size are simultaneously measured using lithium ions Rutherford scattered from the foil. The approximately 20 ns full width at half maximum, 10 MeV peak kinetic energy, Li3+ ion beam deposited up to 435 TW/g (±30%) in the Al layer. The peak electron temperature reached in the Al layer is estimated to be 38–43 eV by comparing the relative emission intensities from the He-like and Li-like Al with collisional-radiative-equilibrium (CRE) calculations. The data are used to examine one-dimensional radiation-hydrodynamic simulations that calculate the target plasma temperature and density using the measured beam parameters as input. It was found that a detailed CRE treatment of the atomic level populations and the line transport is essential for accurate calculations of the radiation loss from the ion heated target. Simulations that include such a treatment embedded within the radiation-hydrodynamic calculations are in good agreement with the data, within the experimental uncertainties. The methods developed here for observation and analysis of Kα spectra provide a sensitive tool suitable for the more stringent examinations of intense ion beam-matter interaction models that will ultimately be required for light-ion driven fusion.
Phys. Rev. E. 56(6).
