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Partial wave analysis of the reaction. pi. /sup +/p. -->. pi. /sup +/. pi. /sup -/. pi. /sup 0/. delta. /sup + +/ at 7 GeV/c. [Isobar model]

Description: An amplitude analysis of the reaction ..pi../sup +/p ..-->.. ..pi../sup +/..pi../sup -/..pi../sup 0/..delta../sup + +/ at 7 GeV/c was performed using the isobar model for the 3..pi.. system. The 3..pi.. mass covers the range 0.82 to 1.9 GeV. No significant A/sub 1/ production can be seen. The spin-parity of the ..omega..*(1700) is determined to 3/sup -/. Properties of A/sub 2/ and ..omega..* production are determined and compared with theoretical models. The background is similar to that seen in analyses of charged 3..pi.. systems.
Date: September 1, 1975
Creator: Tabak, M.
Partner: UNT Libraries Government Documents Department

Nuclear interactions of heavy ions

Description: A possible source of preheat for heavy ion driven inertial fusion targets is the production of fast precursors by nuclear interactions between the incident heavy ions and the outer parts of the target. A model has been developed which roughly describes these interactions for all beam-target combinations for all incident energies. This interaction model has been applied to a specific capsule design. The resultant preheat is an order of magnitude below the level which could impair target performance.
Date: February 24, 1982
Creator: Tabak, M. & Bangerter, R.
Partner: UNT Libraries Government Documents Department

Target Physics

Description: Inertial fusion targets can be categorized by the ignition scheme, the implosions mechanism and the driver technology used to supply the compression and the ignition energy. We will briefly review each of these elements. There are two ignition methods currently being considered. The first, called hotspot ignition, heats a central core of the compressed fuel to ignition temperatures. The assembly of a sufficiently large hotspot is accomplished by stagnation of a convergent flow. The assembled configuration of the hotspot, and surrounding compressed, low temperature fuel, will be approximately isobaric. The second ignition technique, called fast ignition, heats cold compressed fuel to ignition temperatures directly with an external source of heat. This technique has become practicable by the advent of short-pulse, high-intensity lasers using chirped-pulse-amplification (CPA), that can compress laser pulses to extremely high power. If focused appropriately, these fast-ignition laser beams can provide the same power densities as result from the hydrodynamic flow stagnation of the first technique. Inertial fusion fuel can be compressed by two techniques, referred to as direct and indirect drive. Directly driven capsules directly absorb energy delivered by the external compression driver and use it to implode the fusion fuel. Indirectly driven targets absorb the external energy in material away from the capsule, which converts it into x-rays. The x rays are contained in a hohlraum fabricated from high atomic weight material, that symmetrizes the x rays. The capsule then absorbs these x-rays to compress the fuel.
Date: July 20, 2002
Creator: Tabak, M
Partner: UNT Libraries Government Documents Department

Design of a distributed radiator target for inertial fusion driven from two sides with heavy ion beams

Description: We describe the status of a distributed radiator heavy ion target design. In integrated calculations this target ignited and produced 390-430 MJ of yieldwhen driven with 5.8-6.5 MJ of 3-4 GeV Pb ions. The target has cylindrical symmetry with disk endplates. The ions uniformly illuminate these endplates in a 5mm radius spot. We discuss the considerations which led to this design together with some previously unused design features: low density hohlraum walls in approximate pressure balance with internal low-Z fill materials, radiationsymmetry determined by the position of the radiator materials and particle ranges, and early time pressure symmetry possibly influenced by radiation shims. We discuss how this target scales to lower input energy or to lower beam power. Variant designs with more realistic beam focusing strategies are also discussed. We show the tradeoffs required for targets which accept higher particle energies.
Date: November 10, 1997
Creator: Tabak, M. & Callahan-Miller, D.
Partner: UNT Libraries Government Documents Department

Fast ignitor coupling physics

Description: The Fast Ignitor is an alternate approach to ICF in which short pulse lasers are used to initiate burn at the surface of the compressed DT fuel. The aim is to avoid the need for careful central focusing of final shocks, and possibly to lower substantially the energy requirements for ignition. Ultimately, both goals may prove crucial to Science Based Stockpile Stewardship (SBSS). This will be the case should either emerging energetic needs, or funding difficulties render the presently planned radiative fusion approach to ignition with the NIF impractical. Ignition is a first step towards the achievement of substantial energy and neutron outputs for such Stewardship. For success with the Fast Ignitor, the laser energy must be efficiently deposited into megavolt electrons (suprathermal), which must, in turn, couple to the background ions within an alpha particle range. To understand the electron fuel coupling, we have used ANTHEM plasma simulation code to model the transport of hot electrons generated by an intense short pulse laser into plasma targets over a broad range of densities. Our study will spell out the acceleration and transport mechanisms active in the Fast Ignitor environment.
Date: October 1, 1997
Creator: Mason, R.J. & Tabak, M.
Partner: UNT Libraries Government Documents Department

Fast Ignitor coupling physics

Description: The Fast Ignitor is an alternate approach to ICF in which short pulse lasers are used to initiate burn at the surface of the compressed DT fuel. The aim is to avoid the need for careful central focusing of final shocks, and possibly to lower substantially the energy requirements for ignition. Ultimately, both goals may prove crucial to Science Based Stockpile Stewardship (SBSS). This will be the case should either emerging energetic needs, or finding difficulties render the presently planned radiative fusion approach to ignition with the NIF impractical. Ignition is a first step towards the achievement of substantial energy and neutron outputs for such Stewardship.
Date: October 1, 1997
Creator: Mason, R.J. & Tabak, M.
Partner: UNT Libraries Government Documents Department

Short-Pulse Laser-Matter Computational Workshop Proceedings

Description: For three days at the end of August 2004, 55 plasma scientists met at the Four Points by Sheraton in Pleasanton to discuss some of the critical issues associated with the computational aspects of the interaction of short-pulse high-intensity lasers with matter. The workshop was organized around the following six key areas: (1) Laser propagation/interaction through various density plasmas: micro scale; (2) Anomalous electron transport effects: From micro to meso scale; (3) Electron transport through plasmas: From meso to macro scale; (4) Ion beam generation, transport, and focusing; (5) ''Atomic-scale'' electron and proton stopping powers; and (6) K{alpha} diagnostics.
Date: November 2, 2004
Creator: Town, R & Tabak, M
Partner: UNT Libraries Government Documents Department

Nonlinear Rayleigh-Taylor growth in convergine geometry

Description: The early nonlinear phase of Rayleigh-Taylor growth is typically described in terms of the classic Layzer model in which bubbles of light fluid rise into the heavy fluid at a constant rate determined by the bubble radius and the gravitational acceleration. However, this model is strictly valid only for planar interfaces and hence ignores any effects which might be introduced by the spherically converging interfaces of interest in inertial confinement fusion. Here a generalization of the Layzer nonlinear bubble rise rate is given for a self-similar spherically converging flow of the type studied by Kidder. A simple formula for the bubble amplitude is found showing that, while the bubble initially rises with a constant velocity similar to the Layzer result, during the late phase of the implosion, an acceleration of the bubble rise rate occurs. The bubble rise rate is verified by comparison with numerical hydrodynamics simulations.
Date: April 26, 2004
Creator: Clark, D S & Tabak, M
Partner: UNT Libraries Government Documents Department

Acceleration and deceleration phase nonlinear Rayleigh-Taylor growth at spherical interfaces

Description: The Layzer model for the nonlinear evolution of bubbles in the Rayleigh-Taylor instability has recently been generalized to the case of spherically imploding interfaces [D. S. Clark and M. Tabak, to appear, PRE (2005).]. The spherical case is more relevant to, e.g., inertial confinement fusion or various astrophysical phenomena when the convergence is strong or the perturbation wavelength is comparable to the interface curvature. Here, the model is further extended to the case of bubble growth during the deceleration (stagnation) phase of a spherical implosion and to the growth of spikes during both the acceleration and deceleration phases. Differences in the nonlinear growth rates for both bubbles and spikes are found when compared with planar results. The model predictions are verified by comparison with numerical hydrodynamics simulations.
Date: April 8, 2005
Creator: Clark, D S & Tabak, M
Partner: UNT Libraries Government Documents Department

Linear and nonlinear Rayleigh-Taylor growth at strongly convergent spherical interfaces

Description: Recent attention has focused on the effect of spherical convergence on the nonlinear phase of Rayleigh-Taylor growth. For instability growth on spherically converging interfaces, modifications to the predictions of the Layzer model for the secular growth of a single, nonlinear mode have been reported [D. S. Clark and M. Tabak, Phys. Rev. E 72, 0056308 (2005).]. However, this model is limited in assuming a self-similar background implosion history as well as only addressing growth from a perturbation of already nonlinearly large amplitude. Additionally, only the case of single-mode growth was considered and not the multimode growth of interest in applications. Here, these deficiencies are remedied. First, the connection of the recent nonlinear results including convergence to the well-known results for the linear regime of growth is demonstrated. Second, the applicability of the model to more general implosion histories (i.e., not self-similar) is shown. Finally, to address the case of multimode growth with convergence, the recent nonlinear single mode results are combined with the Haan model formulation for weakly nonlinear multimode growth. Remarkably, convergence in the nonlinear regime is found not to modify substantially the multimode predictions of Haan's original model.
Date: December 22, 2005
Creator: Clark, D S & Tabak, M
Partner: UNT Libraries Government Documents Department

Isochoric Implosions for Fast Ignition

Description: Various gain models have shown the potentially great advantages of Fast Ignition (FI) Inertial Confinement Fusion (ICF) over its conventional hot spot ignition counterpart [e.g., S. Atzeni, Phys. Plasmas 6, 3316 (1999); M. Tabak et al., Fusion Sci. & Technology 49, 254 (2006)]. These gain models, however, all assume nearly uniform-density fuel assemblies. In contrast, conventional ICF implosions yield hollowed fuel assemblies with a high-density shell of fuel surrounding a low-density, high-pressure hot spot. Hence, to realize fully the advantages of FI, an alternative implosion design must be found which yields nearly isochoric fuel assemblies without substantial hot spots. Here, it is shown that a self-similar spherical implosion of the type originally studied by Guderley [Luftfahrtforschung 19, 302 (1942)] may be employed to yield precisely such quasi-isochoric imploded states. The difficulty remains, however, of accessing these self-similarly imploding configurations from initial conditions representing an actual ICF target, namely a uniform, solid-density shell at rest. Furthermore, these specialized implosions must be realized for practicable drive parameters and at the scales and energies of interest in ICF. A direct-drive implosion scheme is presented which meets all of these requirements and reaches a nearly isochoric assembled density of 300 g=cm{sup 3} and areal density of 2.4 g=cm{sup 2} using 485 kJ of laser energy.
Date: April 4, 2007
Creator: Clark, D S & Tabak, M
Partner: UNT Libraries Government Documents Department

Isochoric implosions for fast ignition

Description: Fast Ignition (FI) exploits the ignition of a dense, uniform fuel assembly by an external energy source to achieve high gain. In conventional ICF implosions, however, the fuel assembles as a dense shell surrounding a low density, high-pressure hotspot. Such configurations are far from optimal for FI. Here, it is shown that a self-similar spherical implosion of the type originally studied by Guderley [Luftfahrtforschung 19, 302 (1942).] may be employed to implode a dense, quasi-uniform fuel assembly with minimal energy wastage in forming a hotspot. A scheme for realizing these specialized implosions in a practical ICF target is also described.
Date: June 5, 2006
Creator: Clark, D S & Tabak, M
Partner: UNT Libraries Government Documents Department

Target Designs for an Inertial Fusion Energy Power Plant Driven by Heavy Ions

Description: We present two indirect drive inertial fusion targets driven by heavy ions beams for fusion energy production. Because there are uncertainties in the ion beam focal spot size and uncertainties in the accelerator cost, we have tried to design targets that cover a large parameter space. One of the designs requires small ion beam focal spots but produces more than adequate gain at low driver energy (gain 130 from 3.3 MJ of beam energy). The other design allows a large beam spot, but requires more driver energy (gain 55 from 6.7 MJ of beam energy). Target physics issues as well as the implications for the accelerator from each design are discussed.
Date: August 23, 2001
Creator: Callahan, D A & Tabak, M
Partner: UNT Libraries Government Documents Department

Distributed radiator, heavy ion driven inertial confinement fusion target with realistic, multibeam illumination geometry

Description: This paper presents a series of heavy ion driven, inertial confinement fusion targets that all have adequate gain (> 50) for inertial fusion energy. These targets are based on the distributed radiator concept in which much of the hohlraum is filled with low density converter material in approximate pressure balance. This target is driven by heavy ion beams with a Gaussian spatial distribution in a multibeam geometry that is consistent with the number of beams needed by the accelerator and the space needed by the final focusing system. Because the optimal ion species and kinetic energy depend on the integrated system of accelerator, final focusing, chamber transport, and target, we have extended the distributed radiator target to accept ions with range of 0.035 g/cm2 to 0.08 g/cm 2. In addition, a �close coupled� version of the target, in which the hohlraum wall is brought in closer to the capsule to increase the coupling efficiency, has produced gain > 130 from 3.3 MJ of beam energy.
Date: September 18, 1998
Creator: Callahan-Miller, D & Tabak, M
Partner: UNT Libraries Government Documents Department

Fast ignitor coupling physics

Description: The Fast Ignitor is an alternate approach to ICF in which short pulse lasers are used to initiate burn at the surface of the compressed DT fuel. The aim is to avoid the need for careful central focussing of final shocks, and possibly to lower substantially the energy requirements for ignition. Ultimately, both goals may prove crucial to Stockpile Stewardship. For success with the Fast Ignitor, the laser energy must be efficiently deposited into megavolt electrons, which must, in turn, couple to the background ions within an alpha particle range. To understand this coupling, we have used ANTHEM plasma simulation code to model the transport of hot electrons generated by an intense ({ge} 3 x 10{sup 18} W/cm{sup 2}) short pulse 1.06 {mu}m laser into plasma targets over a broad range of densities (0.35 to 10{sup 4} x n{sub crit}). Ponderomotive effects are included as a force on the cold background and hot emission electrons of the form, F{sub h,c} = -({omega}{sup 2}{sub Ph,c}/2{omega}{sup 2}){del}I, in which I is the laser intensity and {omega}{sub p}{sup 2} = 4{pi}e{sup 2}n/m{sub 0}{gamma} with m{sub 0} the electron rest mass.
Date: October 1, 1997
Creator: Mason, R.J. & Tabak, M.
Partner: UNT Libraries Government Documents Department

Inertial Fusion Energy (IFE) concepts, target physics subgroup

Description: The target physics subgroup met for three days of three hour sessions and discussed several questions: Session 1A: What are the key scientific issues for validating each target concept and how can they be resolved; Session 1B: How can existing (and new?) facilities be used to test each concept; Session 1C: (1) What IFE target physics issues will not be resolved on NIF; (2) What is required to get to high yield; and (3) What is the significance to IFE of experimentally demonstrating high yield/high gain? During the discussions, the third question actually turned into a debate concerning the related question of whether or not a single-shot high yield facility is necessary prior to the ETF.
Date: July 1, 1999
Creator: Tabak, M
Partner: UNT Libraries Government Documents Department

On the Utility of Antiprotons as Drivers for Inertial Confinement Fusion

Description: By contrast to the large mass, complexity and recirculating power of conventional drivers for inertial confinement fusion (ICF), antiproton annihilation offers a specific energy of 90MJ/{micro}g and thus a unique form of energy packaging and delivery. In principle, antiproton drivers could provide a profound reduction in system mass for advanced space propulsion by ICF. We examine the physics underlying the use of antiprotons ({bar p}) to drive various classes of high-yield ICF targets by the methods of volumetric ignition, hotspot ignition and fast ignition. The useable fraction of annihilation deposition energy is determined for both {bar p}-driven ablative compression and {bar p}-driven fast ignition, in association with 0-D and 1-D target burn models. Thereby, we deduce scaling laws for the number of injected antiprotons required per capsule, together with timing and focal spot requirements. The kinetic energy of the injected antiproton beam required to penetrate to the desired annihilation point is always small relative to the deposited annihilation energy. We show that heavy metal seeding of the fuel and/or ablator is required to optimize local deposition of annihilation energy and determine that a minimum of {approx}3x10{sup 15} injected antiprotons will be required to achieve high yield (several hundred megajoules) in any target configuration. Target gains - i.e., fusion yields divided by the available p - {bar p} annihilation energy from the injected antiprotons (1.88GeV/{bar p}) - range from {approx}3 for volumetric ignition targets to {approx}600 for fast ignition targets. Antiproton-driven ICF is a speculative concept, and the handling of antiprotons and their required injection precision - temporally and spatially - will present significant technical challenges. The storage and manipulation of low-energy antiprotons, particularly in the form of antihydrogen, is a science in its infancy and a large scale-up of antiproton production over present supply methods would be required to embark ...
Date: October 20, 2003
Creator: Perkins, L J; Orth, C D & Tabak, M
Partner: UNT Libraries Government Documents Department

Radiation-driven targets for heavy-ion fusion

Description: The baseline hohlraum configuration for heavy-ion fusion has the radiation converters placed at opposite ends. For a capsule that absorbs about 1 MJ and has an initial radius of 0.234 cm, the minimum initial capsule to hohlraum surface area ratio that can provide an adequate time-dependent symmetry requirement for a capsule implosion is about 0.075, based on calculations using the view factor code GERTIE. The capsule implosion is calculated using the hydrodynamic code HYADES. The energy coupling efficiency between the hohlraum and the capsule is 21%, the peak hohlraum temperature is 260 eV, and the gain of this target system can be as high as 80. By placing the converters outside the hohlraum, the radii of the converters can be varied according to the beam focusing requirements while the hohlraum dimensions remain unchanged. By bending the radiation converters by 90{degree}, one can obtain a hohlraum configuration that requires the ion beams to come in from only one direction.
Date: August 1994
Creator: Ho, D. D. M.; Harte, J. A. & Tabak, M.
Partner: UNT Libraries Government Documents Department

Progress in Target Design for IFE for Ion Beams and Lasers

Description: Critical to the success of high gain ion beam driven targets for IFE is the tradeoff between target gain and the required focal spot size. A target design has been developed which uses the internal structure of the hohlraum to achieve radiation symmetry using beam spots with almost triple the allowed focal spot area relative to the earlier distributed radiator designs at comparable driver energy. An analysis is presented of the tradeoff between implosion robustness and the target fabrication specifications for survival against hydrodynamic instabilities during the implosion. A key issue for laser driven direct drive (DD) targets is control of hydrodynamic instability growth while achieving adequate gain for IFE. The goal of DD targets for IFE is to maximize gain through use of features such as wetted foams and laser zooming to increase absorption and use of a high-z coating to reduce laser imprint and achieve optimal control of instability growth. Because of advances in hohlraum design, laser driven indirect drive targets may have adequate gain for IFE for laser drivers with an efficiency of 10% or more. A key issue for the fast ignition concept is the ability to couple the hot electrons produced in high intensity laser matter interaction into the dense imploded core of an implosion. Indirect drive designs with a re-entrant cone make it possible to keep the dense core within about 100 {micro}m of the laser absorption point.
Date: November 5, 2001
Creator: Lindl, J D; Tabak, M; Callahan-Miller, D; Hermann, M & Hatchett, S
Partner: UNT Libraries Government Documents Department

Studies of Indirect Drive IFE Capsules in Two and Three Dimensions

Description: We study in detail the properties of a 265eV peak temperature indirect drive IFE capsule design. The capsule has a plastic ablator covering a layer of DT ice; with a DT gas fill and an outer radius of 2.3 mm. We give linear growth rate curves for single modes for a range of wave numbers, paying particular attention to the reduction of ''chevron modes'' that can occur as a result of numerical instabilities. We compare the two and three-dimensional behavior of single modes.
Date: September 1, 2003
Creator: Koniges, A E; Marinak, M M; Tabak, M & Herrmann, M C
Partner: UNT Libraries Government Documents Department