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LLE Review, Quarterly Report: Volume 49, October-December 1991 (open access)

LLE Review, Quarterly Report: Volume 49, October-December 1991

This volume of the LLE Review, covering the period October-December 1991, contains articles on the analysis of argon-filled target experiments, and a theoretical analysis of the impact of nonlocal heat transport in laser filamentation in plasmas. In the Advanced Technology section there is an article on mechanisms that affect thin-film conductivity, and a report on the gain characteristics of the 20-cm SSA prototype amplifier to be used in the OMEGA Upgrade. Finally, the activities of the National Laser Users Facility and the GDL and OMEGA laser facilities are summarized. Highlights of the research reported in this issue are: argon radiation from argon-filled, polymer-shell targets is used as a core-temperature diagnostic and density diagnostic of the surrounding region in a regime where the argon line radiation is strongly absorbed. A theoretical analysis of the impact of nonlocal heat transport on laser filamentation in plasmas is developed. The resulting model is compared with experimental observations and the implications for ICF are discussed. A study of thermal conductivity in thin films seeks to identify mechanisms that result in degradation of thin-film conductivity. Identifying these mechanisms can lead to changes in the thin-film manufacture that will improve their resistance to laser damage.
Date: January 1, 1991
Creator: Keck, R. L.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 54, January-March 1993 (open access)

LLE Review, Quarterly Report: Volume 54, January-March 1993

This volume of the LLE Review covers the three-month period January--March 1993. The OMEGA laser facility was decommissioned during this quarter to make room for the OMEGA Upgrade laser facility. The decommissioning is described in this volume. Electron thermal transport in the corona and laser-irradiation uniformity are related issues for direct-drive laser fusion. Thermal transport can affect the laser-irradiation uniformity requirements. The status of Fokker-Planck modeling of electron transport at LLE is reviewed and is followed by a description of a new technique for achieving high laser uniformity using zero-correlation phase masks. The use of fast, optically triggered, superconducting opening switches can, in principle, reduce the peak electrical load requirements of systems like the OMEGA Upgrade. Recent research in this area is described. The last three articles discuss vacuum ultraviolet and x-ray emission from short-pulse, laser-matter interactions. The generation of a high spectral brightness, picosecond K{alpha} source is described. The subsequent articles describe the generation of high-order harmonics of a high-intensity laser system laser system in low- density, laser-atom interactions and the novel gas target used.
Date: July 1, 1993
Creator: Meyerhofer, D. D.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 43, April-June 1990 (open access)

LLE Review, Quarterly Report: Volume 43, April-June 1990

This volume of the LLE Review, covering the period April--June 1990, contains articles in two main sections, Progress in Laser Fusion and Advanced Technology Developments. The first article presents the theoretical interpretation of the glass-ablator cryogenic-implosion experiments recently conducted on OMEGA. It is followed by an article describing the analysis of neutron time-of-flight data taken during DT and DD experiments; and a discussion of the improvements to laser diagnostics that now provide for precise control of the OMEGA laser is given. This paper contains a report on the development of transparent conductive coatings for KDP crystals, and a discussion of the study of the transient-surface Debye-Waller effect in materials irradiated with an ultrafast laser.
Date: January 1, 1990
Creator: Kumpan, S. A.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 55, April-June 1993 (open access)

LLE Review, Quarterly Report: Volume 55, April-June 1993

This volume of the LLE Review, covering the period April--June 1993, contains articles on spectral features from argon-filled target implosions on OMEGA, and on the theory of an implicit difference scheme for the Fokker-Planck equation. The advanced technology section includes reports on a novel polymer liquid-crystal wave plate and a new scheme for phase conversion of the OMEGA Upgrade beams that results in greater, smoother energy deposition on fusion targets. Finally, reports on the as-designed configuration of the OMEGA newly configured glass development laser system are summarized.
Date: October 1, 1993
Creator: Hutchison, R. J.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 58, January-March 1994 (open access)

LLE Review, Quarterly Report: Volume 58, January-March 1994

This volume of the LLE Review, covering the period Jan - Mar 1994, contains articles on backlighting diagnostics; the effect of electron collisions on ion-acoustic waves and heat flow; using PIC code simulations for analysis of ultrashort laser pulses interacting with solid targets; creating a new instrument for characterizing thick cryogenic layers; and a description of a large-aperture ring amplifier for laser-fusion drivers. Three of these articles - backlighting diagnostics; characterizing thick cryogenic layers; and large-aperture ring amplifier - are directly related to the OMEGA Upgrade, now under construction. Separate abstracts have been prepared for articles from this report.
Date: July 1, 1994
Creator: Simon, A.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 62, January-March 1995 (open access)

LLE Review, Quarterly Report: Volume 62, January-March 1995

This volume of the LLE review, covering the period of January-March 1995, contains articles on the evaluation of the mechanism for laser damage in OMEGA UV multilayer coatings using a combination of conventional laser-damage characterization methods and atomic force microscopy; a dual-amplitude, fiber-coupled waveguide integrated-optic modulation device for generating temporally shaped optical pulses in OMEGA-, a proposal for modifying the indirect-drive irradiation geometry of the National Ignition Facility (NIF) to provide the additional flexibility for performing direct-drive experiments; direct measurements of terminal-level lifetime in several different Nd:YLF laser media; an overview of the materials science issues, basic mechanisms, and potential device applications for light-emitting porous silicon; and a study of the time-dependent reflection and surface temperatures for laser-irradiated dental hard tissue at two CO{sub 2} laser wavelengths.
Date: July 1, 1995
Creator: unknown
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 69, October-December 1996 (open access)

LLE Review, Quarterly Report: Volume 69, October-December 1996

This volume of the LLE Review, covering the period October-December 1996, includes a review of 2-D SSD as implemented on the OMEGA laser system. A summary of the detailed mathematical formalism is shown, and the predicted level of uniformity achievable on OMEGA is given. The first experimental results on uniformity using narrow-band 2-D SSD are compared to theoretical calculations. Excellent agreement between experiment and theory is found, which gives confidence that broadband 2-D SSD with polarization wedges should achieve an rms nonuniformity in the 1%-2% level necessary for cryogenic implosion experiments.
Date: April 1, 1997
Creator: Town, Richard
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 68, July-September 1996 (open access)

LLE Review, Quarterly Report: Volume 68, July-September 1996

This volume of the LLE Review, covering the period of July-September 1996, includes a description of an important experiment carried out on OMEGA by researchers from LANL, LLNL, and LLE to demonstrate the feasibility of using OMEGA for indirect drive. Additional topics include tetrahedral hohlraums, the speckle properties of phase- converted laser beams, design criteria for SSD phase modulators, and the design of slab amplifiers. Highlights of the research presented in this issue are (1) Results from the proof-of-principle indirect- drive experiments in which up to 40 OMEGA beams were used to irradiate cylindrical hohlraums. Nova results were reproduced, and new capabilities not available on other lasers were demonstrated. (2) A discussion of tetrahedral hohlraums (spherical hohlraums with four laser entrance holes) as a means of achieving better capsule irradiation uniformity. Tetrahedral hohlraums also allow the use of all 60 OMEGA beams and may provide an alternate route to ignition on the NIF. (3) An analysis of the residual target irradiation nonuniformity due to the fine laser speckle remaining on the beam after being phase converted by the DPP`s. A model shows how a uniformly ablating plasma atmosphere reduces the speckle contribution to the effective time-averaged irradiation nonuniformity. (4) A …
Date: July 1, 1996
Creator: Skledon, Mark E.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 67, April-June 1996 (open access)

LLE Review, Quarterly Report: Volume 67, April-June 1996

This volume contains articles detailing several nonlinear processes associated with lasers and their use, as well as an article describing the computer control systems necessary to maintain and operate a large laser system such as the 60-beam OMEGA laser. The specific topics discussed in this issue include stimulated scattering in laser plasmas, power exchange between interacting laser beams, charged particles interacting with a laser pulse, thermal equilibration of optically excited states, an overview of the laser control system software in OMEGA, and a technique for cancellation of the nonlinear phase accumulation in short-pulse lasers.
Date: November 1, 1996
Creator: Skeldon, Mark D.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 66, January-March 1996 (open access)

LLE Review, Quarterly Report: Volume 66, January-March 1996

This volume of the LLE Review, covering the period January-March 1996, contains three articles related to spherical implosions and their diagnosis, one article that provides an analysis of laser-plasma interactions, and three articles on advanced technologies developed at LLE.
Date: June 1, 1996
Creator: Boehly, T. R.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 71, April-June 1997 (open access)

LLE Review, Quarterly Report: Volume 71, April-June 1997

This volume of the LLE Review, covering the period April-June 1997, includes an article discussing the results from recent experiments performed on OMEGA. These experiments used a new beam-smoothing device-distributed polarization rotators-in concert with existing techniques to improve the on-target uniformity of each beam. The result of this improved radiation uniformity was a substantive reduction in imprinting-the nonuniformity caused by the laser. A novel way to study the time dependence of this imprinting is also presented in this article.
Date: October 1, 1997
Creator: Harding, David
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 72, July-September 1997 (open access)

LLE Review, Quarterly Report: Volume 72, July-September 1997

This volume of the LLE Review, covering the period July--September 1997, begins with a general introduction to LLE`s experimental physics program and a report on recent results. This article includes a useful summary of the system`s operational capabilities and system parameters. Other highlights of the wide variety of research presented in this issue are: a promising method to directly observe the cold compressed shell of an imploding target. The shell is normally observed by backlighting. The proposal described here is to use a high-Z dopant that fluoresces under radiation from the hot core in the K{alpha} line. A study of the instabilities associated with near-forward stimulated Brillouin scattering. It includes a calculation of the saturation times and steady-state gain exponents. A successful program of pulse shaping for the OMEGA laser system. Examples of a variety of pulse shapes that can be programmed are presented. A description of the angular-scattering characteristics of ferroelectric liquid crystal electro-optical devices operating in transient and extended scattering modes. The possibility of applying these devices as modulators in practical IR imaging systems is evaluated. A faster method of shaping and finishing IR materials by the use of magnetorheological fluids. Detailed specifications and test results are included. …
Date: February 1, 1998
Creator: unknown
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 84, July-September 2000 (open access)

LLE Review, Quarterly Report: Volume 84, July-September 2000

This volume of the LLE Review, covering July-September 2000, begins with an article by T. R. Boehly, V. N. Goncharov, O. Gotchev, J. P. Knauer, D. D. Meyerhofer, D. Oron, S. P. Regan, Y. Srebro, W. Seka, D. Shvarts, S. Skupsky, and V.A. Smalyuk, who describe measurements of the effect of beam smoothing and pulse shape on imprinting. (Imprinting is defined as the imposition of pressure perturbations on the target by spatial variations in the laser intensity.) A principal result is the observation of reduced levels of imprint with the higher beam smoothing afforded by 1-THz smoothing by spectral dispersion (SSD). Additional highlights of research presented in this issue are: (1) P. W. McKenty, V. N. Goncharov, R. P. J. Town, S. Skupsky, R. Betti, and R. L. McCrory describe calculations of directly driven ignition capsule performance on the National Ignition Facility (NIF). The authors detail how the various contributors to implosion disruption (laser imprint, power imbalance, and target roughness) affect target performance and final gain. The conclusions are obtained by examining the simulated target evolution with the two-dimensional hydrodynamics computer code ORCHID. (2) D. D. Meyerhofer, J. A. Delettrez, R. Epstein, V. Yu. Glebov, V. N. Goncharov, R. L. …
Date: December 1, 2000
Creator: Marshall, Frederic J.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 79, April-June 1999 (open access)

LLE Review, Quarterly Report: Volume 79, April-June 1999

This volume of the Laboratory for Laser Energetics (LLE) Review, covering the period April-June 1999, features a theoretical analysis of direct-drive target performance on National Ignition Facility (NIF). In this article R. P. J. Town, J. A. Delettrez, R. Epstein, V. N. Goncharov, R. L. McCrory, P. W. McKenty, R. W. Short, and S. Skupsky detail ignition target designs developed at LLE specifically to achieve successful direct-drive ignition on the NIF facility. A baseline ''all-DT'' target design is described along with a two shock compression analysis, which includes discussion of the parameters leading to variability in shock timing. The modeling and analysis presented flow down to specification requirements for the laser and target parameters to ignite this baseline target design with the NIF laser.
Date: April 1, 1999
Creator: Morse, Samuel F. B.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 73, October-December 1997 (open access)

LLE Review, Quarterly Report: Volume 73, October-December 1997

This progress report contains discussion on the following topics: A high-bandwidth electrical-waveform generator based on aperture-coupled striplines for OMEGA pulse-shaping applications; sweep deflection circuit development using computer-aided circuit design for the OMEGA multichannel streak camera; D-{sup 3}He protons as a diagnostic for target {rho}R; growth rates of the ablative Rayleigh-Taylor instability in inertial confinement fusion; three-dimensional analysis of the power transfer between crossed laser beams; characterization of freestanding polymer films for application in 351-nm, high-peak-power laser systems; subsurface damage in microgrinding optical glasses; bound-abrasive polishers for optical glass; and color gamut of cholesteric liquid crystal films and flakes by standard colorimetry.
Date: April 1, 1998
Creator: Jacobs, Stephen D.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 65, October-December 1995 (open access)

LLE Review, Quarterly Report: Volume 65, October-December 1995

This volume of the LLE Review, covering the period October-December 1995, contains a description of the generation and characterization of continuous, deep-surface-relief phase plates that are more efficient and versatile than previous designs. The LLE program plan has scheduled a number of enhancements to OMEGA`s performance and uniformity, the first of which is the implementation of these new distributed phase plates. Other articles in this volume include the discussion of an x-ray diagnostic method to measure shell-fuel mixing, the theoretical analysis of ablation-front stability, a description of a major subsystem in the OMEGA control system software, a study of the population inversions in intensely pumped Nd:YLF, and a description of a new ultrafast laser system and its uses.
Date: June 1, 1996
Creator: Boehly, T. R.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 64, July-September 1995 (open access)

LLE Review, Quarterly Report: Volume 64, July-September 1995

This volume of the LLE Review, covering the period July--September 1995, includes a description of the first target experiments performed on the upgraded OMEGA laser system. These experiments, carried out to active and test several diagnostics systems, have demonstrated successful functioning of the overall experimental system and have produced high neutron yields and high core temperatures. Other articles in this volume describe the diagnosis of core conditions using krypton line spectroscopy, a mix model for LILAC that can be applied to study the deceleration instability at the pusher-core interface, a simulated-annealing algorithm for improved phase-plate design, a simple method for characterizing the thickness and uniformity of transparent laser-fusion targets, and femtosecond pump-probe experiments on semiconducting YBCO.
Date: September 1, 1995
Creator: Craxton, R. S.
System: The UNT Digital Library
LLE Review, Quarterly Report: Volume 74, January-March 1998 (open access)

LLE Review, Quarterly Report: Volume 74, January-March 1998

This volume of the LLE Review covers the period January--March 1998. The first of eight articles documents the in-house development, scale-up, and manufacture of 60 continuous distributed phase plates with high laser-damage resistance. D.J. Smith et al. describe how inert ion beams were used to etch a continuously varying pattern into the surface of fused silica to form these devices. Other highlights of research presented in this issue are: (1) a soft x-ray microscope with high spatial resolution has been characterized and used for initial experiments on the OMEGA laser system, F.J. Marshall et al. give details of the testing, calibration, and initial use of this microscope for studying the hydrodynamic stability of directly driven planar foils; (2) D.K. Bradley et al. report on a series of experiments designed to investigate hydrodynamic instability growth in direct-drive capsule implosions; (3) C.J. McKinstrie et al. report on the use of systematic perturbation methods to derive formulas for the Landau damping rates of electron-plasma and ion-acoustic waves; (4) high efficiency and good beam quality are potential advantages of the end-pumped solid-state lasers over the side-pumped ones, A. Babushkin et al. describe their successful use of a transport fiber to end-pump a Nd:YLF laser, …
Date: July 1, 1998
Creator: Jacobs, S. D.
System: The UNT Digital Library