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in creator/contributor: "Rothenberg, J."

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SSD with generalized phase modulation

Smoothing by spectral dispersion (SSD) with standard frequency modulation (FM), although simple to implement, has the disadvantage that low spatial frequencies present in the spectrum of the target illumination are not smoothed as effectively as with a more general smoothing method (eg, induced spatial incoherence method). The reduced smoothing performance of standard FM-SSD can result in spectral power of the speckle noise at these low spatial frequencies as much as one order of magnitude larg… more

Date: January 9, 1996

Creator: Rothenberg, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Two dimensional beam smoothing by spectral dispersion for direct drive inertial confinement fusion

Two dimensional smoothing by spectral dispersion is analyzed by using diffraction theory calculations. It is shown that by using standard frequency modulated light one can obtain bandwidth limited smoothing over integration times relevant to inertial confinement fusion (about 1 nsec) with modest induced beam divergence. At longer integration times one can obtain bandwidth limited smoothing by increasing the divergence and/or by using more advanced phase modulation methods.

Date: July 11, 1995

Creator: Rothenberg, J.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Improved beam smoothing with SSD using generalized phase modulation

The smoothing of the spatial illumination of an inertial confinement fusion target is examined by its spatial frequency content. It is found that the smoothing by spectral dispersion method, although efficient for glass lasers, can yield poor smoothing at low spatial frequency. The dependence of the smoothed spatial spectrum on the characteristics of phase modulation and dispersion is examined for both sinusoidal and more general phase modulation. It is shown that smoothing with non-sinusoidal … more

Date: January 1, 1997

Creator: Rothenberg, J.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electro-optical deflectors as a method of beam smoothing for Inertial Confinement Fusion

The electro-optic deflector is analyzed and compared to smoothing by spectral dispersion for efficacy as a beam smoothing method for ICF. It is found that the electro-optic deflector is inherently somewhat less efficient when compared either on the basis of equal peak phase modulation or equal generated bandwidth.

Date: January 1, 1997

Creator: Rothenberg, J.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Smoothing by spectral dispersion using random phase modulation for inertial confinement fusion

Numerical simulations of beam smoothing using random phase modulation and grating dispersion are presented. Spatial spectra of the target illumination show that significantly improved smoothing at low spatial frequency is achieved while maintaining uniform intensity in the laser amplifier.

Date: November 15, 1995

Creator: Rothenberg, J.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Impact of beam smoothing method on direct drive target performance for the NIF

The impact of smoothing method on the performance of a direct drive target is modeled and examined in terms of its l-mode spectrum. In particular, two classes of smoothing methods are compared, smoothing by spectral dispersion (SSD) and the induced spatial incoherence (ISI) method. It is found that SSD using sinusoidal phase modulation (FM) results in poor smoothing at low l-modes and therefore inferior target performance at both peak velocity and ignition. Modeling of the hydrodynamic nonlinea… more

Date: November 1, 1996

Creator: Rothenberg, J.E. & Weber, S.V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Impact of beam smoothing method on direct drive target performance for the NIF

The impact of smoothing method on the performance of a direct drive target is modeled and examined in terms of its 1-mode spectrum. In particular, two classes of smoothing methods are compared, smoothing by spectral dispersion (SSD) and the induced spatial incoherence (ISI) method. It is found that SSD using sinusoidal phase modulation (FM) results in poor smoothing at low 1-modes and therefore inferior target performance at both peak velocity and ignition. This disparity is most notable if the… more

Date: January 1, 1997

Creator: Rothenberg, J.E. & Weber, S.V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Configuring NIF for direct drive experiments

The National Ignition Facility (NIF) is a proposed 1.8 MJ laser facility for carrying out experiments in inertial confinement fusion, currently designed for indirect drive experiments. The direct drive approach is being pursued at the 30 kJ Omega facility at the University of Rochester. In this paper we discuss the modifications to the NIF laser that would be required for both indirect and direct drive experiments. A primary concern is the additional cost of adding direct drive capability to th… more

Date: July 11, 1995

Creator: Eimerl, D.; Rothenberg, J. & Key, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Polarization smoothing for the National Ignition Facility

Polarization smoothing (PS) is the illumination of the target with two distinct and orthogonally polarized speckle patterns. Since these two polarizations do not interfere, the intensity patterns add incoherently and thus the contrast of the intensity nonuniformity can be reduced by a factor of {radical}2 in addition to any reduction achieved by temporal smoothing techniques. Smoothing by PS is completely effective on an instantaneous basis and is therefore of particular interest for the suppre… more

Date: August 13, 1998

Creator: Rothenberg, J F

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Performance of smoothing by spectral dispersion (SSD) with frequency conversion on the Beamlet Laser for the National Ignition Facility

Simulations and ongoing measurements indicate that SSD results in small degradation to the near field beam quality. The measured effect of SSD bandwidth on conversion to the third harmonic and smoothing of the target illumination will also be described.

Date: November 4, 1997

Creator: Rothenberg, J.E.; Morgan, B.; Wegner, P. & Weiland, T.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Performance of smoothing by spectral dispersion (SSD) on Beamlet

The performance of the Beamlet laser with 1D SSD implemented is investigated. Simulations indicate that the critical issue for laser performance is the amount of additional divergence owing to SSD in comparison to the size of the spatial filter pinholes. At the current {plus_minus}200 {mu}rad pinholes used on Beamlet, simulations indicate that the levels of SSD divergence anticipated for the National Ignition Facility (NIF) results in a very slight degradation to the near field beam quality. Ex… more

Date: January 1, 1997

Creator: Rothenberg, J.E.; Moran, B.; Henesian, M. & Van Wonterghem, B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Progress at LLNL toward DPSSL-Driven Intertial Fusion Energy

We describe research indicating that a diode-pumped solid-state laser (DPSSL) can serve as a viable driver for an inertial fusion energy (IFE) power plant. The ongoing construction of the National Ignition Facility (NIF) sets the stage for a new era to start in the next decade for target research aimed at achieving the high gains necessary for both defense and energy applications. In addition, advances in DPSSL research show that this type of laser can have adequate efficiency and reliability, … more

Date: February 19, 2002

Creator: Orth, C D; Rothenberg, J E; Payne, S A & Powell, H T

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Illumination uniformity requirements for direct drive inertial confinement fusion

The requirements for laser uniformity are discussed in terms of the {ell}-mode spectrum. It is shown that the choice of smoothing methods can significantly alter this spectrum and that this choice should be made in the context of the target physics. Although two dimensional smoothing by spectral dispersion yields a high quality near field beam profile, it results in poor smoothing for low spatial frequency. The partially coherent light method (fiber smoothing) leads to superior smoothing at low… more

Date: July 11, 1995

Creator: Rothenberg, J. E.; Eimerl, D.; Key, M. H. & Weber, S. V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The issue of FM to AM conversion on the National Ignition Facility

The National Ignition Facility (NIF) baseline configuration for inertial confinement fusion requires phase modulation for two purposes. First, ~ 1Å of frequency modulation (FM) bandwidth at low modulation frequency is required to suppress buildup of Stimulated Brioullin Scattering (SBS) in the large aperture laser optics. Also ~ 3 Å or more bandwidth at high modulation frequency is required for smoothing of the speckle pattern illuminating the target by the smoothing by spectral dispersion meth… more

Date: August 13, 1998

Creator: Browning, D F; Rothenberg, J E & Wilcox, R B

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laser Imprint and Implications for Direct Drive Ignition With the National Ignition Facility

For direct drive ICF, nonuniformities in laser illumination can seed ripples at the ablation front in a process called imprint. Such nonuniformities will grow during the capsule implosion and can penetrate the capsule shell impede ignition, or degrade burn. We have simulated imprint for a number of experiments on tile Nova laser. Results are in generally good agreement with experimental data. We leave also simulated imprint upon National Ignition Facility (NIF) direct drive ignition capsules. I… more

Date: July 9, 1996

Creator: Weber, S. V.; Glendinning, S. G.; Kalantar, D. H.; Remington, B. A. & Rothenberg, J. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development system performance issues of the NIF master oscillator and pulse forming networking

A crucial step in the development of a complex laser system is initial testing of an integrated system. Issues arise at the system level which are not easily observed in component level testing. The NIF master oscillator room (MOR) contains a network of fiber and integrated optic components which can interact, potentially reducing system performance. Here we present some of the system problems we have seen in integrated tests and our solutions. Issues include ASE in the fiber amplifiers, filter… more

Date: October 29, 1998

Creator: Browning, D; Dreifuerst, G; Penko, F; Rothenberg, J & Wilcox, R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Exploring the Limits to NIF Capsule Coupling

Our original ignition ''point designs'' (circa 1992) for the National Ignition Facility (NIF) were made energetically conservative to provide margin for uncertainties in laser absorption, x-ray conversion efficiency and hohlraum-capsule coupling. Since that time, extensive experiments on Nova and Omega and their related analysis indicate that NIF coupling efficiency may be almost ''as good as we could hope for''. Given close agreement between experiment and theory/modeling, we can credibly expl… more

Date: November 3, 1999

Creator: Suter, L.; Rothenberg, J.; Munro, D.; Van Wonterghem, B. & Haan, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Feasibility of High Yield / High Gain NIF Capsules

Date: December 6, 1999

Creator: Suter, L.; Rothenberg, J.; Munro, D.; Van Wonterghem, B.; Haan, S. & Lindl, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Implementation and performance of beam smoothing on 10 beams of the Nova Laser

Recent simulations and experiments on Nova indicate that some level of smoothing may be required to suppress filamentation in plasmas on the National Ignition Facility (NIF), resulting in the addition of 1-D smoothing capability to the current baseline design. Control of stimulated Brillouin scattering (SBS) and filamentation is considered essential to the success of laser fusion because they affect the amount and location of laser energy delivered to the x-ray conversion region (hohlraum wall)… more

Date: March 11, 1997

Creator: Pennington, D. M.; Dixit, S. N.; Weiland, T. L.; Ehrlich, R. & Rothenberg, J. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laser techniques for extreme-ultraviolet spectroscopy

In this paper we describe several techniques for using lasers to study core-excited energy levels in the spectral region between 10 eV and 100 eV. We are particularly interested in levels that are metastable against autoionization and, in some cases, against both autoionization and radiation.

Date: June 1, 1983

Creator: Harris, S. E.; Young, J. F.; Caro, R. G.; Falcone, R. W.; Holmgren, D. E.; Walker, D. J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Implementation of smoothing by spectral dispersion on Beamlet and NIF

The performance of the Beamlet laser with one dimensional smoothing by spectral dispersion (1D SSD) implemented is investigated. Measurements of the near field beam quality, nonlinear breakup, and transmission through spatial filter pinholes show a modest effect only at large SSD divergence. No measurable effect was found at the divergence level planned for indirect drive ignition experiments. The efficiency of conversion to the third harmonic was also measured with SSD present and found to be … more

Date: June 9, 1999

Creator: Auerbach, J M; Moran, B D; Murray, J E; Rothenberg, J E; Wegner, P J & Weiland, T L

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Recent Developments in Ignition Target Designs for the National Ignition Facility

Work on design of ignition targets for the National Ignition Facility (NIF) has progressed in three areas. First, hohlraums have been re-optimized taking advantage of improvements in efficiency in several areas: use of high albedo material mixtures in the hohlraum wall; optimizing the laser entrance hole; optimizing the case-to-capsule ratio; and taking advantage of increased efficiency of longer pulses. These changes, in combination, allow for the possibility of quite high yields ({approx}100 … more

Date: September 20, 2000

Creator: Suter, L.; Haan, S.; Lindl, J.; Dittrich, T.; Hammel, B. A.; Hinkel, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulations of Laser Imprint for Nova Experiments and for Ignition Capsules. Revision 1

In direct drive ICF, nonuniformities in laser illumination seed ripples at the ablation front in a process called ``imprint``. These nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser at LLNL examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule puls… more

Date: December 1, 1996

Creator: Weber, S. V.; Glendinning, S. G.; Kalantar, D. H.; Key, M. H.; Remington, B. A.; Rothenberg, J. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulations of Laser Imprint for Nova Experiments and for Ignition Capsules

In direct drive ICF, nonuniformities in laser illumination seed ripples at the ablation front in a process called imprint. These non nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser at LLNL examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule puls… more

Date: November 8, 1996

Creator: Weber, S. V.; Glendinning, S. G.; Kalantar, D. H.; Key, M. H.; Remington, B. A.; Rothenberg, J. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department