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Laser imprint and implications for direct drive ignition with the National Ignition Facility

Description: 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. Imprint modulation amplitude comparable to the intrinsic surface finish of {approximately}40 nm is predicted for a laser bandwidth of 0.5 THz. Ablation front modulations experience growth factors up to several thousand, carrying modulation well into the nonlinear regime. Saturation modeling predicts that the shell should remain intact at the time of peak velocity, but penetration at earlier times appears more marginal.
Date: July 9, 1996
Creator: Weber, S.V.; Glendinning, S.G.; Kalantar, D.H.; Remington, B.A. & Rothenberg, J.E.
Partner: UNT Libraries Government Documents Department

Design of an electronic charged particle spectrometer to measure ({rho}R), yield, and implosion symmetry on the OMEGA Upgrade

Description: The preliminary design for a state-of-the-art diagnostic that will measure a broad energy spectrum of charged particles generated in the OMEGA Upgrade facility is investigated. Using a set of photodiodes ({approximately}10) and a 0.8 Tesla permanent magnet, the diagnostic will uniquely determine particle energies and identities from 0.2 MeV up to the maximum charged particle energies (10.6 MeV tritons, 12.5 MeV deuterons and 17.4 MeV protons). With its high density picture elements, each photodiode has 10{sup 6} single-hit detectors, giving the spectrometer a dynamic range of 1 {minus} 10{sup 5} particles/shot. For example, in the case of a DT yield of 10{sup 9} neutrons, about 100 knock-on charged particles will be detected when the spectrometer aperture is 60 cm from the implosion. Furthermore, the measurement of knock-on D and T spectra will allow {rho}R`s up to 0.15 g/cm{sup 2} to be measured (for a 1 keV plasma), or 0.3 g/cm{sup 2}2 if hydrogen doping is used. In addition, the yield and slowing down of secondary protons may be used to determine {rho}R up to 0.3 g/cm{sup 2}. Significantly, this diagnostic will also directly measure the DD fusion yield and energy degradation of nascent 3 MeV protons. By using two such compact spectrometers to measure the yield and spectra on widely separated ports around the OMEGA Upgrade target chamber, the implosion and bum symmetry can be determined. Furthermore, the ion temperature, and, in principle, even the electron temperature can be measured. The diagnostic and its development will be fully tested at several critical steps, utilizing 0.2-16 MeV protons (and several other charged particles and neutrons) from our absolutely calibrated Cockcroft-Walton facility.
Date: November 1, 1994
Creator: Hicks, D.G.; Li, C.K.; Petrasso, R.D.; Wenzel, K.W. & Knauer, J.P.
Partner: UNT Libraries Government Documents Department

Affordable Near-term Burning-plasma Experiments

Description: Fusion energy is a potential energy source for the future with plentiful fuel supplies and is expected to have benign environmental impact. The issue with fusion energy has been the scientific feasibility, and recently the cost of this approach. The key technical milestone for fusion is the achievement of a self-sustained fusion fire, ignition, in the laboratory. Despite 40 years of research and the expenditure of almost $20B worldwide, a self-sustained fusion fire has not yet been produced in the laboratory. The fusion program needs a test bed, preferably more than one, where the dynamics of a burning plasma can be studied, optimized and understood so that the engineering requirements for an engineering test reactor can be determined. Engineering and physics concepts must be developed within the next decade that will lead to an Affordable Burning Plasma Experiment if fusion is going to be perceived as making progress toward a potential long-range energy source.
Date: April 1, 1998
Creator: Meade, D.M. & Wooley, R.D.
Partner: UNT Libraries Government Documents Department

NIF capsule design update

Description: We describe several ignition capsule designs, for use in the National Ignition Facility. We will compare these designs for ablator efficiency, ignition margin, implosion and stability performance. This study includes capsule designs driven by x-ray drive profiles with both 300 eV and 250 eV peak temperatures. All of the 300 eV designs are tuned to implode the DT fuel in a nearly identical manner. Capsule designs consist of an ablator material (CH with Br dopant; Be with Cu dopant; and B{sub 4}C) encasing a layer of solid DT. The dopants alter material opacities sufficiently to (1) shield the DT fuel from preheat effects; and (2) develop an ablation front density profile favorable to implosion stability. B{sub 4}C has sufficient opacity at 300 eV that a dopant is not necessary. Issues relating to material properties and fabrication will be described.
Date: October 1, 1996
Creator: Dittrich, T.R.; Haan, S.W.; Pollaine, S.; Burnham, A.K. & Strobel, G.L.
Partner: UNT Libraries Government Documents Department

Results from D-T Experiments on TFTR and Implications for Achieving an Ignited Plasma

Description: Progress in the performance of tokamak devices has enabled not only the production of significant bursts of fusion energy from deuterium-tritium plasmas in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) but, more importantly, the initial study of the physics of burning magnetically confined plasmas. As a result of the worldwide research on tokamaks, the scientific and technical issues for achieving an ignited plasma are better understood and the remaining questions more clearly defined. The principal research topics which have been studied on TFTR are transport, magnetohydrodynamic stability, and energetic particle confinement. The integration of separate solutions to problems in each of these research areas has also been of major interest. Although significant advances, such as the reduction of turbulent transport by means of internal transport barriers, identification of the theoretically predicted bootstrap current, and the study of the confinement of energetic fusion alpha-particles have been made, interesting and important scientific and technical issues remain for achieving a magnetic fusion energy reactor. In this paper, the implications of the TFTR experiments for overcoming these remaining issues will be discussed.
Date: July 14, 1998
Creator: Hawryluk, R.J. and the TFTR Group
Partner: UNT Libraries Government Documents Department

Magnetic-compression/magnetized-target fusion (MAGO/MTF): A marriage of inertial and magnetic confinement

Description: Intermediate between magnetic confinement (MFE) and inertial confinement (ICF) in time and density scales is an area of research now known in the US as magnetized target fusion (MTF) and in Russian as MAGO (MAGnitnoye Obzhatiye--magnetic compression). MAGO/MTF uses a magnetic field and preheated, wall-confined plasma fusion fuel within an implodable fusion target. The magnetic field suppresses thermal conduction losses in the fuel during the target implosion and hydrodynamic compression heating process. In contrast to direct, hydrodynamic compression of initially ambient-temperature fuel (i.e., ICF), MAGO/MTF involves two steps: (a) formation of a warm (e.g., 100 eV or higher), magnetized (e.g., 100 kG) plasma within a fusion target prior to implosion; (b) subsequent quasi-adiabatic compression by an imploding pusher, of which a magnetically driven imploding liner is one example. In this paper, the authors present ongoing activities and potential future activities in this relatively unexplored area of controlled thermonuclear fusion.
Date: December 31, 1996
Creator: Lindemuth, I.R.; Ekdahl, C.A. & Kirkpatrick, R.C.
Partner: UNT Libraries Government Documents Department

Fusion Ignition Research Experiment System Integration

Description: This paper describes the current status of the FIRE configuration and the integration of the major subsystem components. FIRE has a major radius of 2 m, a field on axis of 10T, a plasma current of 6.4 MA. It is capable of 18 second pulses when operated with DT and 26 s when operated with DD. The general arrangement consists of sixteen wedged TF coils that surround a free standing central solenoid, a double wall vacuum vessel and internal plasma facing components that are segmented for maintenance through horizontal ports. Large rings located outside the TF coils are used to obtain a load balance between wedging of the intercoil case structure and wedging at the upper/lower inboard corners of the TF coil winding. The magnets are liquid nitrogen cooled and the entire device is surrounded by a thermal enclosure. The double wall vacuum vessel integrates cooling and shielding in a shape that maximizes shielding of ex-vessel components. Within the vacuum vessel, plasma-facing components frame the plasma. First wall tiles are attached directly to inboard and outboard vacuum vessel walls. The divertor is designed for a high triangularity, double-null plasma with a short inner null point-to-wall distance and near vertical outer divertor flux line. The FIRE configuration has been developed to meet the physics objectives and subsystem requirements in an arrangement that allows remote maintenance of in-vessel components and hands-on maintenance of components outside the TF boundary.
Date: October 17, 2000
Creator: Brown, T.
Partner: UNT Libraries Government Documents Department

Mathematical modeling plasma transport in tokamaks

Description: In this work, the author applied a systematic calibration, validation and application procedure based on the methodology of mathematical modeling to international thermonuclear experimental reactor (ITER) ignition studies. The multi-mode plasma transport model used here includes a linear combination of drift wave branch and ballooning branch instabilities with two a priori uncertain constants to account for anomalous plasma transport in tokamaks. A Bayesian parameter estimation method is used including experimental calibration error/model offsets and error bar rescaling factors to determine the two uncertain constants in the transport model with quantitative confidence level estimates for the calibrated parameters, which gives two saturation levels of instabilities. This method is first tested using a gyroBohm multi-mode transport model with a pair of DIII-D discharge experimental data, and then applied to calibrating a nominal multi-mode transport model against a broad database using twelve discharges from seven different tokamaks. The calibrated transport model is then validated on five discharges from JT-60 with no adjustable constants. The results are in a good agreement with experimental data. Finally, the resulting class of multi-mode tokamak plasma transport models is applied to the transport analysis of the ignition probability in a next generation machine, ITER. A reference simulation of basic ITER engineering design activity (EDA) parameters shows that a self-sustained thermonuclear burn with 1.5 GW output power can be achieved provided that impurity control makes radiative losses sufficiently small at an average plasma density of 1.2 X 10{sup 20}/m{sup 3} with 50 MW auxiliary heating. The ignition probability of ITER for the EDA parameters, can be formally as high as 99.9% in the present context. The same probability for concept design activity (CDA) parameters of ITER, which has smaller size and lower current, is only 62.6%.
Date: December 31, 1995
Creator: Quiang, Ji
Partner: UNT Libraries Government Documents Department

Fusion ignition research experiment

Description: Understanding the properties of high gain (alpha-dominated) fusion plasmas in an advanced toroidal configuration is the largest remaining open issue that must be addressed to provide the scientific foundation for an attractive magnetic fusion reactor. The critical parts of this science can be obtained in a compact high field tokamak which is also likely to provide the fastest and least expensive path to understanding alpha-dominated plasmas in advanced toroidal systems.
Date: July 18, 2000
Creator: Meade, Dale
Partner: UNT Libraries Government Documents Department

Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

Description: Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5{times}10{sup 17} W/cm{sup 2}) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime.
Date: April 1, 1995
Creator: Wilks, S. C.; Kruer, W. L.; Young, P. E.; Hammer, J. & Tabak, M.
Partner: UNT Libraries Government Documents Department

The Implicit Hyprid/PIC Code AMTHEM.

Description: Recent inventions in pulse power switching, fast laser-driven thermonuclear ignition, and short pulse radiography have demanded a dramatic increase in the capabilities of plasma simulation tools. Multifluid, multi-component, fluid and kinetic models are needed for plasmas spanning thousands of Debye lengths and thousands of plasma periods. Such plasmas manifest both dense and tenuous regions, including or excluding magnetic fields and collisional resistivity. The problems of interest can dwell in a transition regime with limits traditionally treated by resistive MHD and and/or collisional particle-in-cell (PIC) methods. The ANTHEM implicit hybrid simulation model is under development to meet these challenges. This presentation will outline its past and current features, and review results typical of short-pulse laser applications.
Date: January 1, 2002
Creator: Mason, R. J. (Rodney J.)
Partner: UNT Libraries Government Documents Department

The National Ignition Facility: The Path to a Carbon-Free Energy Future

Description: The National Ignition Facility (NIF), the world's largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory (LLNL). The NIF will enable exploration of scientific problems in national strategic security, basic science and fusion energy. One of the early NIF goals centers on achieving laboratory-scale thermonuclear ignition and energy gain, demonstrating the feasibility of laser fusion as a viable source of clean, carbon-free energy. This talk will discuss the precision technology and engineering challenges of building the NIF and those we must overcome to make fusion energy a commercial reality.
Date: March 16, 2011
Creator: Stolz, C J
Partner: UNT Libraries Government Documents Department

Results from D-T experiments on TFTR and implications for achieving an ignited plasma

Description: Progress in the performance of tokamak devices has enable not only the production of significant bursts of fusion energy from deuterium-tritium plasmas in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) but, more importantly, the initial study of the physics of burning magnetically confined plasmas. As a result of the worldwide research on tokamaks, the scientific and technical issues for achieving an ignited plasma are better understood and the remaining questions more clearly defined. The principal research topics which have been studied on TFTR are transport, magnetohydrodynamic stability, and energetic particle confinement. The integration of separate solutions to problems in each of these research areas has also been of major interest. Although significant advances, such as the reduction of turbulent transport by means of internal transport barriers, identification of the theoretically predicted bootstrap current, and the study of the confinement of energetic fusion alpha-particles have been made, interesting and important scientific and technical issues remain. In this paper, the implications for the TFTR experiments for overcoming these remaining issues will be discussed.
Date: July 1, 1998
Creator: Hawryluk, R.J.; Blanchard, W. & Batha, S.
Partner: UNT Libraries Government Documents Department

Target requirements on the path to ignition

Description: The Los Alamos ICF program has made several advances in learning what is required for ignition on NIF. This work continues to focus on beryllium--understanding why it appears less sensitive to DT ice roughness, the feed-out/feed-in phenomena, applying that understanding to new designs, performing experiments to confirm this mechanism, and studying the effects of joints in beryllium components.
Date: December 31, 1998
Creator: Wilson, D.C.; Bradley, P.A.; Barnes, C.W.; Caldwell, S.E.; Chrien, R.E.; Goldman, S.R. et al.
Partner: UNT Libraries Government Documents Department

Turbulent mix study of a double shell capsule

Description: Double shell capsules present an alternative, non-cryogenic design for NIF ignition targets. Such capsules have received little interest because it was assumed that hydrodynamic instabilities would forestall ignition. The authors used a K-L turbulent mix model, integrated into a hydro code, to evaluate a series of double shell implosions. The double shell implosions were laser-driven experiments performed at the OMEGA laser. They briefly review the turbulent mix model. The model has adjustable parameters for the growth and dissipation terms. These are initially set by comparison to classical experiments. The model also requires an initial length scale and an initial wavelength scale. Next the authors briefly describe the experiment. The target assembly consists of an inner shell of glass and an outer shell of brominated plastic. They present the analysis of the hydrodynamic implosion, using the turbulent mix model. The agreement between experiment and calculation suggests that the model could be successfully applied to ignition targets.
Date: November 16, 1999
Creator: Vantine, H C & Tipton, R E
Partner: UNT Libraries Government Documents Department

Physics basis for the Fusion Ignition Research Experiment (FIRE)

Description: Understanding the properties of high gain (alpha-dominated) fusion plasmas in an advanced toroidal configuration is a critical issue that must be addressed to provide the scientific foundation for an attractive magnetic fusion reactor. The functional fusion plasma objectives for major next physics steps in magnetic fusion research can be described as: Burning Plasma Physics - The achievement and understanding of alpha-dominated plasmas that have characteristics similar to those expected in a fusion energy source, and Advanced Toroidal Physics - The achievement and understanding of bootstrap-current-dominated plasmas with externally controlled profiles and other characteristics (e.g. confinement and beta) similar to those expected in an attractive fusion system.
Date: July 7, 2000
Creator: Meade, D. M.; Thome, R. J.; Sauthoff, N. R.; Heitzenroeder, P. J.; Nelson, B. E.; Ulrickson, M.A et al.
Partner: UNT Libraries Government Documents Department

Wire-number effects on high-power annular z-pinches and some characteristics at high wire number

Description: Characteristics of annular wire-array z-pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high x-ray power generation, and have initiated a renaissance in z-pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by x-rays from a z-pinch, and are commented on here.
Date: May 23, 2000
Creator: SANFORD,THOMAS W. L.
Partner: UNT Libraries Government Documents Department

Integrated ignition calculations for indirectly driven targets

Description: We present two-dimensional LASNEX calculations of the hohlraum and ignition capsules proposed for the National Ignition Facility (NIF). Our current hohlraum design is a 2.76 mm radius, 9.49 mm long gold cylinder with 1.39 mm radius laser entrance holes (LEH) which are covered by 1 {mu}m thick polyamide foils. Laser beams with less that 1.4 MJ total energy and less than 400 TW peak power irradiate the cylinder wall from two separate cones entering each LEH. The hohlraum interior is filled with hydrogen-helium gas (50-50 atomic) at a density of 0.83 mg/cm{sup 3} to suppress the inward expansion of the wall. The capsule uses either a 160 {mu}m plastic ablator doped with bromine (the baseline design), or a 155 {mu}m beryllium ablator doped with copper (the beryllium design). The ablator surrounds an 80 {mu}m thick deuterium-tritium (DT) ice layer with an inner radius of 0.87 mm. We will show the results of integrated, two-dimensional calculations of the hohlraum and the capsule. Plasma conditions within the hohlraum will be described. Peak radiation temperatures in the hohlraum are about 300 eV. These calculations proceed through the implosion, ignition, and burn of the DT capsule. Current peak calculated yields are 12 MJ for the baseline design and 6.9 MJ for the capsule with the beryllium ablator, although higher yields should be achievable with improved ``tuning`` of the laser power levels.
Date: July 1, 1995
Creator: Krauser, W.J.; Wilde, B.H.; Wilson, D.C.; Bradley, P. & Swenson, F.
Partner: UNT Libraries Government Documents Department

Proposed generation and compression of a target plasma for MTF

Description: Magnetized target fusion (MTF), in which a magnetothermally insulated plasma is hydrodynamically compressed to fusion conditions, represents an approach to controlled fusion which avoids difficulties of both traditional inertial confinement and magnetic confinement approaches. The authors are proposing to demonstrate the feasibility of magnetized target fusion by: (1) creating a suitable magnetized target plasma, (2) performing preliminary liner compression experiments using existing pulsed power facilities and demonstrated liner performance. Once the target plasma and the means for its generation have been optimized, the authors plan to conduct preliminary liner compression experiments aimed at demonstrating the near-adiabatic compression of the target plasma desired for MTF. Relevant liner compression experiments have been performed at Los Alamos in the Scyllac Fast Liner Program and, more recently, in the Pegasus facility and the Procyon explosive pulsed power program. In a series of liner experiments they plan to map out the dependence of temperature and neutron production as functions of the initial plasma conditions and the liner compression achieved. With the above research program, they intend to demonstrate most of the key principles involved in magnetized target fusion, and develop the experimental and theoretical tools needed to design and execute fully integrated MTF ignition experiments.
Date: September 1, 1995
Creator: Kirkpatrick, R.C.; Thurston, R.S. & Chrien, R.E.
Partner: UNT Libraries Government Documents Department

Experimental measurements of the 15O(alpha,gamma)19Ne reaction rate and the stability of thermonuclear burning on accreting neutron stars

Description: Neutron stars in close binary star systems often accrete matter from their companion stars. Thermonuclear ignition of the accreted material in the atmosphere of the neutron star leads to a thermonuclear explosion which is observed as an X-ray burst occurring periodically between hours and days depending on the accretion rate. The ignition conditions are characterized by a sensitive interplay between the accretion rate of the fuel supply and its depletion rate by nuclear burning in the hot CNO cycle and the rp-process. For accretion rates close to stable burning the burst ignition therefore depends critically on the hot CNO breakout reaction {sup 15}O({alpha}, {gamma}){sup 19}Ne that regulates the flow between the hot CNO cycle and the rapid proton capture process. Until recently, the {sup 15}O({alpha}, {gamma}){sup 19}Ne reaction rate was not known experimentally and the theoretical estimates carried significant uncertainties. In this paper we perform a parameter study of the uncertainty of this reaction rate and determine the astrophysical consequences of the first measurement of this reaction rate. Our results corroborate earlier predictions and show that theoretically burning remains unstable up to accretion rates near the Eddington limit, in contrast to astronomical observations.
Date: May 8, 2007
Creator: Fisker, J; Tan, W; Goerres, J; Wiescher, M & Cooper, R
Partner: UNT Libraries Government Documents Department

Nondimensional transport experiments on DIII-D and projections to an ignition tokamak

Description: The concept of nondimensional scaling of transport makes it possible to determine the required size for an ignition device based upon data from a single machine and illuminates the underlying physics of anomalous transport. The scaling of cross-field heat transport with the relative gyroradius {rho}*, the gyroradius normalized to the plasma minor radius, is of particular interest since {rho}* is the only nondimensional parameter which will vary significantly between present day machines and an ignition device. These nondimensional scaling experiments are based upon theoretical considerations which indicate that the thermal heat diffusivity can be written in the form {chi} = {chi}{sub B}{rho}*{sup x{sub {rho}}} F({beta}, v*, q, R/a, {kappa}, T{sub e}/T{sub i},...), where {chi}{sub B} = cT/eB. As explained elsewhere, x{sub {rho}} = 1 is called gyro-Bohm scaling, x{sub {rho}} is Bohm scaling, x{sub {rho}} = {minus}1/2 is Goldston scaling, and x{sub {rho}} = {minus}1 is stochastic scaling. The DIII-D results reported in this paper cover three important aspects of nondimensional scaling experiments: the testing of the underlying assumption of the nondimensional scaling approach, the determination of the {rho}* scaling of heat transport for various plasma regimes, and the extrapolation of the energy confinement time to future ignition devices.
Date: July 1, 1996
Creator: Petty, C.C.; Luce, T.C.; Balet, B.; Christiansen, J.P. & Cordey, J.G.
Partner: UNT Libraries Government Documents Department