Indirect-Drive ICF Ignition - Core Science, Technology Devel Plan
Tuning of the the symmetry of the hohlraum radiation drive for the first 2 ns of the ICF pulse on NIF will be assessed by the re-emit technique  which measures the instantaneous x-ray drive asymmetry based on soft x-ray imaging of the re-emission of a high-Z sphere surrogate capsule. We will discuss the design of re-emit foot symmetry tuning measurements planned on NIF and their surrogacy for ignition experiments, including assessing the residual radiation asymmetry of the patches required for soft x-ray imaging.
We will present the tuning strategy and expected accuracies based on calculations, analytical estimates and first results from scaled experiments performed at the Omega laser facility. Delamater, G. Magelssen, A. Hauer, Phys. E 53, Indirect drive ignition at the National Ignition Facility. This article reviews scientific results from the pursuit of indirect drive ignition on the National Ignition Facility NIF and describes the program's forward looking research directions. In indirect drive on the NIF, laser beams heat an x-ray enclosure called a hohlraum that surrounds a spherical pellet.
Requirements on velocity, symmetry, and compression have been demonstrated separately on the NIF but have not been achieved simultaneously. We now know that the RT instability, seeded mainly by the capsule support tent, severely degraded DT implosions from — Experiments using a 'high-foot' drive with demonstrated lower RT growth improved the thermonuclear yield by a factor of 10, resulting in yield amplification due to alpha particle heating by more than a factor of 2.
However, large time dependent drive asymmetry in the LPI-dominated hohlraums remains unchanged, preventing further improvements. High fidelity 3D hydrodynamic calculations explain these results. In conclusion, future research efforts focus on improved capsule mounting techniques and on hohlraums with little LPI and controllable symmetry. In parallel, we are pursuing improvements to the basic physics models used in the design codes through focused physics experiments.
Perkins, L. John; Logan, B. Imposed magnetic fields of tens of Tesla that increase to greater than 10 kT MGauss under capsule compression may relax conditions for ignition and propagating burn in indirect-drive ICF targets. This may allow attainment of ignition , or at least significant fusion energy yields, in presently-performing ICF targets on the National Ignition Facility that today are sub-marginal for thermonuclear burn through adverse hydrodynamic conditions at stagnation. Results of detailed 2D radiation-hydrodynamic-burn simulations applied to NIF capsule implosions with low-mode shape perturbations and residual kinetic energy loss indicate that such compressed fields may increase the probability for ignition through range reduction of fusion alpha particles, suppression of electron heat conduction and stabilization of higher-mode RT instabilities.
Optimum initial applied fields are around 50 T.
Off-line testing has been performed of a hohlraum coil and pulsed power supply that could be integrated on NIF; axial fields of 58T were obtained. Given the full plasma structure at capsule stagnation may be governed by 3-D resistive MHD, the formation of closed magnetic field lines might further augment ignition prospects. Work performed under auspices of U. The physics basis for ignition using indirect-drive targets on the National Ignition Facility.
Lindl, John D. Gail; Glenzer, Siegfried H. The National Academy of Science final report of its review of the Inertial Confinement Fusion Program recommended completion of a series of target physics objectives on the beam Nova laser at the Lawrence Livermore National Laboratory as the highest-priority prerequisite for proceeding with construction of an ignition -scale laser facility, now called the National Ignition Facility NIF.
These objectives were chosen to demonstrate that there was sufficient understanding of the physics of ignition targets that the laser requirements for laboratory ignition could be accurately specified. This research on Nova, as well as additional research on the Omega laser at the University of Rochester, is the subject of this review. The objectives of the U. The HLP program addresses laser-plasma coupling, x-ray generation and transport, and the development of energy-efficient hohlraums that provide the appropriate spectral, temporal, and spatial x-ray drive.
The HEP experiments address the issues of hydrodynamic instability and mix, as well as the effects of flux asymmetry on capsules that are scaled as closely as possible to ignition capsules hydrodynamic equivalence. The HEP program also addresses other capsule physics issues associated with ignition , such as energy gain and energy loss to the fuel during implosion in the absence of alpha-particle deposition.
The results from the Nova and Omega experiments approach the NIF requirements for most of the important ignition capsule parameters, including. Inertial confinement fusion ICF is an alternative way to control fusion which is based on scaling down a thermonuclear explosion to a small size, applicable for power production, a kind of thermonuclear internal combustion engine.
This book extends many interesting topics concerning the research and development on ICF of the last 25 years. It provides a systematic development of the physics basis and also various experimental data on radiation driven implosion. This is a landmark treatise presented at the right time. Lindl, published in Physics of Plasmas, Vol. As is well known, in the United States of America research on the target physics basis for indirect drive remained largely classified until The indirect drive approaches were closely related to nuclear weapons research at Lawrence Livermore and Los Alamos National Laboratories.
In these circumstances the international fusion community proposed the Madrid Manifesto in , which urged openness of ICF information to promote international collaboration on civil energy research for the future resources of the human race. This proposal was also supported by some of the US scientists. This first book from the USA treating target physics issues, covering topics from implosion dynamics to hydrodynamic stability, ignition physics, high-gain target design and the scope for energy applications is.
We have compared the compression of an indirectly driven cone-in-shell target, a type proposed for the fast ignition concept, with models. The implosion was backlit with 6. The collapsing structure was very similar to model predictions except that non-thermal m-band emissions from the hohlraum penetrated the shell and vaporized gold off the reentrant cone. This could be eliminated by changing the hohlraum composition. Hatchett, et al. Fusion and Plasma Phys. The simulations of indirect-drive targets for ignition on megajoule lasers. The analysis of published calculations of indirect-drive targets to obtain ignition on NIF and LMJ lasers has shown that these targets have very low margins for ignition : according to 1D-ERA code calculations it could not be ignited under decreasing of thermonuclear reaction rate less than in 2 times.
The purpose of new calculations is search of indirect-drive targets with the raised margins for ignition. The calculations of compression and thermonuclear burning of targets are carried out for conditions of X-ray flux asymmetry obtained in simulations of Rugby hohlraum that were performed with 2D-SINARA code.
The necessity of performed researches is caused by the construction of magajoule laser in Russia. Simakov, A. Current NIF plastic capsules are under-performing, and alternate ablators are being investigated. Beryllium presents an attractive option, since it has lower opacity and therefore higher ablation rate, pressure, and velocity. Previous NIF Be designs assumed significantly better hohlraum performance than recently observed e.
DCA , and thus an updated design is required. We present a new, Rev. Work supported by the US Department of Energy. We present results from simulations performed to study the radiative properties of dopants used in inertial confinement fusion indirect-drive capsule implosion experiments on NIF. Spectrally resolved emission from ablator dopants can be used to study the degree of mixing of ablator material into the ignition hot spot.
Here, we study the atomic processes that affect the radiative characteristics of these elements using a set of simulation tools to first estimate the evolution of plasma conditions in the compressed target, and then to compute the atomic kinetics of the dopant and the resultant radiative emission. Using estimates of temperature and density profiles predicted by radiation-hydrodynamics simulations, we set up simple plasma grids where we allow dopant material to be embedded in the fuel, and perform multi-dimensional collisional-radiative simulations using SPECT3D to compute non-LTE atomic level populations and spectral signatures from the dopant.
Recently improved Stark-broadened line shape modeling for Ge K-shell lines has been included. Macfarlane, J. Using estimates of temperature and density profiles predicted by radiation-hydrodynamics simulations, we set up simple 2-D plasma grids where we allow dopant material to be embedded in the fuel, and perform multi-dimensional collisional-radiative simulations using SPECT3D to compute non-LTE atomic level populations and spectral signatures from the dopant.
The potential of imposed magnetic fields for enhancing ignition probability and fusion energy yield in indirect-drive inertial confinement fusion.
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We examine the potential that imposed magnetic fields of tens of Tesla that increase to greater than 10 kT MGauss under implosion compression may relax the conditions required for ignition and propagating burn in indirect-drive inertial confinement fusion ICF targets. This may allow the attainment of ignition , or at least significant fusion energy yields, in presently performing ICF targets on the National Ignition Facility NIF that today are sub-marginal for thermonuclear burn through adverse hydrodynamic conditions at stagnation [Doeppner et al.
Results of detailed two-dimensional radiation-hydrodynamic-burn simulations applied to NIF capsule implosions with low-mode shape perturbations and residual kinetic energy loss indicate that such compressed fields may increase the probability for ignition through range reduction of fusion alpha particles, suppression of electron heat conduction, and potential stabilization of higher-mode Rayleigh-Taylor instabilities. Optimum initial applied fields are found to be around 50 T. Given that the full plasma structure at capsule stagnation may be governed by three-dimensional resistive magneto-hydrodynamics, the formation of closed magnetic field lines might further augment ignition prospects.
Experiments are now required to further assess the potential of applied magnetic fields to ICF ignition and burn on NIF. X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition. Dewald, E. The conversion efficiency of nm laser light to soft x rays 0. Miller, E. Moses, and C. Wuest, Nucl. Fusion 44, ]. The absolute time and spectrally resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses are subtracted.
Zimmerman and W. Kruer, Comm. Plasma Phys. Fusion 2, 51 ] show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0. Instability growth seeded by ablator material inhomogeneity in indirect drive implosions on the National Ignition Facility. Haan, Steven; Ali, S. Characterizing these seeds and estimating their growth is important in projecting performance.
This presentation summarizes the experiments for the three ablators, along with simulations thereof and projections of the significance for NIF. For CH, dominant seeds are photo-induced oxidation, which might be mitigated with alumina coating. For Be, perturbations result from Ar and O contamination. For HDC, perturbations are seeded by shock propagation around melt, depend on shock strength, and may constrain the adiabat of future HDC implosions.
Work performed under the auspices of the U. Capsule implosion optimization during the indirect-drive National Ignition Campaign. Landen, O. Capsule performance optimization campaigns will be conducted at the National Ignition Facility [G. Fusion 44, ] to substantially increase the probability of ignition. The campaigns will experimentally correct for residual uncertainties in the implosion and hohlraum physics used in our radiation-hydrodynamic computational models using a variety of ignition capsule surrogates before proceeding to cryogenic-layered implosions and ignition experiments.
The quantitative goals and technique options and down selections for the tuning campaigns are first explained. The computationally derived sensitivities to key laser and target parameters are compared to simple analytic models to gain further insight into the physics of the tuning techniques.
Soures et al. Plasmas 3, ] under scaled hohlraum and capsule conditions relevant to the ignition design are shown to meet the required sensitivity and accuracy. A roll-up of all expected random and systematic uncertainties in setting the key ignition laser and target parameters due to residual measurement, calibration, cross-coupling, surrogacy, and scale-up errors has been derived that meets the required budget. Finally, we show how the tuning precision will be improved after a number of shots and iterations to meet an acceptable level of residual uncertainty.
A simple method to prevent hard X-ray-induced preheating effects inside the cone tip in indirect-drive fast ignition implosions. During fast- ignition implosions, preheating of inside the cone tip caused by hard X-rays can strongly affect the generation and transport of hot electrons in the cone. Although indirect-drive implosions have a higher implosion symmetry, they cause stronger preheating effects than direct-drive implosions.
To control the preheating of the cone tip, we propose the use of indirect-drive fast- ignition targets with thicker tips. Experiments carried out at the ShenGuang-III prototype laser facility confirmed that thicker tips are effective for controlling preheating.
Moreover, these results were consistent with those of 1D radiation hydrodynamic simulations. Glenzer, S. We demonstrate the hohlraum radiation temperature and symmetry required for ignition -scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2. Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility NIF. This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition.
Probing the deep nonlinear stage of the ablative Rayleigh-Taylor instability in indirect drive experiments on the National Ignition Facility. Academic tests in physical regimes not encountered in Inertial Confinement Fusion will help to build a better understanding of hydrodynamic instabilities and constitute the scientifically grounded validation complementary to fully integrated experiments.
Casner et al. Plasmas 19, ]. This extended acceleration could eventually allow entering into a turbulent-like regime not precluded by the theory for the RTI at the ablation front. Simultaneous measurements of the foil trajectory and the subsequent RTI growth are performed and compared with radiative hydrodynamics simulations. We present RTI growth measurements for two-dimensional single-mode and broadband multimode modulations. The dependence of RTI growth on initial conditions and ablative stabilization is emphasized, and we demonstrate for the first time in indirect-drive a bubble-competition, bubble-merger regime for the RTI at ablation front.
There has been rapid progress in inertial fusion in the past few years. This progress spans the construction of ignition facilities, a wide range of target concepts, and the pursuit of integrated programs to develop fusion energy using lasers, ion beams and z-pinches.
Two ignition facilities are under construction NIF in the U. There is steady progress in the target science and target fabrication in preparation for indirect drive ignition experiments on NIF. Advanced target designs may lead to times more yield than initial target designs. There has also been excellent progress on the science of ion beam and z-pinch driven indirect drive targets.
Excellent progress on direct-drive targets has been obtained on the Omega laser at the University of Rochester. This includes improved performance of targets with a pulse shape predicted to result in reduced hydrodynamic instability. Rochester has also obtained encouraging results from initial cryogenic implosions. There is widespread interest in the science of fast ignition because of its potential for achieving higher target gain with lower driver energy and relaxed target fabrication requirements.
Researchers from Osaka have achieved outstanding implosion and heating results from the Gekko XII Petawatt facility and implosions suitable for fast ignition have been tested on the Omega laser. A broad based program to develop lasers and ions beams for IFE is under way with excellent progress in drivers, chambers, target fabrication and target injection. Lowdermilk, W. Research on Inertial Confinement Fusion ICF is motivated by its potential defense and civilian applications, including ultimately the generation of electric power. The U. Both committees issued final reports in which recommended that first priority in the ICF program be placed on demonstrating fusion ignition and modest gain G less than Results from Nova Upgrade Experiments will be used to define requirements for driver and target technology both for future high-yield military applications, such as the Laboratory Microfusion Facility LMF proposed by the Department of Energy, and for high-gain energy applications leading to an ICF engineering test facility.
The central role and modifications which Nova Upgrade would play in the national ICF strategy are described. Three-dimensional extended-magnetohydrodynamic simulations of the stagnation phase of inertial confinement fusion implosion experiments at the National Ignition Facility are presented, showing self-generated magnetic fields over T. Angular high mode-number perturbations develop large magnetic fields, but are localized to the cold, dense hot-spot surface, which is hard to magnetize.
However, Righi-Leduc heat transport effectively cools the hot spot and lowers the neutron spectra-inferred ion temperatures compared to the unmagnetized case. The Nernst effect qualitatively changes the results by demagnetizing the hot-spot core, while increasing magnetizations at the edge and near regions of large heat loss. We will show theoretical results on the behavior of SBS in the strong damping regime and CBET in mid-Z plasmas around 20 where ion Landau damping and collisional damping are both higher order effects and strong coupling is dominant in laser hot spots and near Mach -1 surfaces in appropriately tuned pairs of crossing beams.
The spatially dependent frequency shits that ensue and the reductions in growth rate allow the control of LPI even downstream beyond the crossing volumes. Multiple successive crossings between O beams can be used to change the space-time intensity distributions of lasers used entirely differently in direct and indirect drive geometries.
In the former case, due to the existence of many angles, a statistical Sqrt N gain is expected. On the other hand, for indirect drive , with cone angles to contend with, turning off interactions by staggering crossing beam spikes, achieved with STUD pulses, is a key deterministic element for the success of the plan. Changing the speckle statistics at will and with fine control is a grand challenge of this set of techniques. X ray spectroscopy is used on the NIF to diagnose the plasma conditions in the ignition target in indirect drive ICF implosions.
A platform is being developed at NIF where small traces of krypton are used as a dopant to the fuel gas for spectroscopic diagnostics using krypton line emissions. The fraction of krypton dopant was varied in the experiments and was selected so as not to perturb the implosion. Our goal is to use X-ray spectroscopy of dopant line ratios produced by the hot core that can provide a precise measurement of electron temperature. Simulations of the krypton spectra using a 1 in atomic fraction of krypton in direct-drive exploding pusher with a range of electron temperatures and densities show discrepancies when different atomic models are used.
We use our non-LTE atomic model with a detailed fine-structure level atomic structure and collisional-radiative rates to investigate the krypton spectra at the same conditions. Synthetic spectra are generated with a detailed multi-frequency radiation transport scheme from the emission regions of interest to analyze the experimental data with 0. X-ray and neutron radiography are currently used to infer residual ICF shell and fuel asymmetries and areal density non-uniformities near and at peak compression that can impede ignition.
Charged particles offer an alternative probe source that, in principle, are capable of radiographing the shell shape and areal density at arbitrary times, even in the presence of large x-ray self-emission. Monte Carlo simulations suggest that both the areal density and shell radius can be reconstructed for ignition -relevant capsules conditions between 0. This work was performed under the auspices of the U. The ablator couples energy between the driver and fusion fuel in inertial confinement fusion ICF. Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility.
We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated. Hydro-instability growth of perturbation seeds from alternate capsule-support strategies in indirect-drive implosions on National Ignition Facility. In other experiments, the perturbations from cantilevered fill tubes were measured and compared to the tent perturbations. In conclusion, the effects of x-ray shadowing during the drive and oxygen-induced perturbations during target assembly produced additional seeds for instabilities and were also measured in these experiments.
Martinez, D. Hydrodynamic instability growth of the capsule support membranes or "tents" and fill tubes has been studied in spherical, glow discharge polymer plastic capsule implosions at the National Ignition Facility NIF [Campbell et al. A new "sub-scale" version of the existing x-ray radiography platform was developed for measuring growing capsule perturbations in the acceleration phase of implosions.
The effects of x-ray shadowing during the drive and oxygen-induced perturbations during target assembly produced additional seeds for instabilities and were also measured in these experiments. The first experiments on the national ignition facility. A first set of shock propagation, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility NIF , in support of indirect drive Inertial Confinement Fusion ICF and High Energy Density Physics.
Positron radiography of ignition -relevant ICF capsules. Laser-generated positrons are evaluated as a probe source to radiograph in-flight ignition -relevant inertial confinement fusion capsules. Monte Carlo simulations suggest that the unique characteristics of such positrons allow for the reconstruction of both capsule shell radius and areal density between 0. The energy-downshifted positron spectrum and angular scattering of the source particles are sufficient to constrain the conditions of the capsule between preshot and stagnation.
We evaluate the effects of magnetic fields near the capsule surface using analytic estimates where it is shown that this diagnostic can tolerate line integrated field strengths of T mm. The present objective of the national Inertial Confinement Fusion ICF Program is to determine the scientific feasibility of compressing and heating a small mass of mixed deuterium and tritium DT to conditions at which fusion occurs and significant energy is released.
The potential applications of ICF will be determined by the resulting fusion energy yield amount of energy produced and gain ratio of energy released to energy required to heat and compress the DT fuel. Important defense and civilian applications, including weapons physics, weapons effects simulation, and ultimately the generation of electric power will become possible if yields of to 1, MJ and gains exceeding approximately 50 can be achieved.
Once ignition and propagating bum producing modest gain 2 to 10 at moderate drive energy 1 to 2 MJ has been achieved, the extension to high gain greater than 50 is straightforward. Therefore, the demonstration of ignition and modest gain is the final step in establishing the scientific feasibility of ICF. This report discusses this facility. BigFoot: a program to reduce risk for indirect drive laser fusion. The conventional approach to inertial confinement fusion ICF with indirect drive is to design for high convergence 40 , DT areal density, and target gain.
By construction, this strategy is challenged by low-mode control of the implosion Legendre P2 and P4 , instability, and difficulties interpreting data. Here we consider an alternative - an approach to ICF that emphasizes control. To begin, we optimize for hohlraum predictability, and coupling to the capsule. Though gain is reduced, this makes it possible to study and improve stagnation physics in a regime relevant to ignition 1EE Further improvements can then be made with small, incremental increases in areal density, target scale, etc.
Work that could enable additional improvements in capsule stability and hohlraum control will also be discussed. Laser hole boring and relativistic electron transport into plasma of 10 times critical density is studied by means of 2D particle-in-cell simulation. When penetrating the overdense region, it breaks up into several filaments at early times, but is channeled into a single magnetized jet later on.
These features are essential for fast ignition of targets for inertial confinement fusion ICF. Adiabat-shaping in indirect drive inertial confinement fusion. Adiabat-shaping techniques were investigated in this paper in indirect drive inertial confinement fusion experiments on the National Ignition Facility as a means to improve implosion stability, while still maintaining a low adiabat in the fuel. Adiabat-shaping was accomplished in these indirect drive experiments by altering the ratio of the picket and trough energies in the laser pulse shape, thus driving a decaying first shock in the ablator.
This decaying first shock is designed to place the ablation front on a high adiabat while keeping the fuel on a low adiabat. This platform enabled direct measurement of the shock velocities driven in the glow-discharge polymer capsule and in the liquid deuterium, the surrogate fuel for a DT ignition target. The measured shock velocities and radiation drive histories are compared to previous three and four shock laser pulses.
This comparison indicates that in the case of adiabat shaping the ablation front initially drives a high shock velocity, and therefore, a high shock pressure and adiabat. The shock then decays as it travels through the ablator to pressures similar to the original low-adiabat pulses when it reaches the fuel. Finally, this approach takes advantage of initial high ablation velocity, which favors stability, and high-compression, which favors high stagnation pressures.
Using a Z-pinch precursor plasma to produce a cylindrical, hotspot ignition , ICF. We show that if the same precursor plasma that exists in metal wire arrays can be generated with a Deuterium-Tritium plasma then this precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The precursor is generated from a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis. Later on, the main implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion.
A computational analysis of this approach is presented, including a study of the thermonuclear burn wave propagation. The robustness of the scheme with respect to instabilities, confinement time and drive parameters is examined. The results indicate that a high energy gain can be achieved using Z-pinches with MA currents and a few hundred nanosecond rise-times.
This work was partially supported by the U. Hotspot ignition using a Z-pinch precursor plasma in a magneto-inertial ICF scheme. Precursor plasma flow is a common feature of wire array Z-pinches. The precursor flow represents a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis.
Later on, the main implosion of the Z-pinch then compresses this precursor to substantially higher density. We show that if the same system can be generated with a Deuterium-Tritium plasma then the precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion.
The azimuthal magnetic field in the hotspot is sufficient to reduce the Larmor radius for the alpha particles to much less than the hotspot size, which dramatically reduces the pR required for ignition. The use of laser-driven Inertial Confinement Fusion ICF for space propulsion has been the subject of several earlier conceptual design studies, see: Orth, ; and other references therein. However, these studies were based on older ICF technology using either 'direct' or 'in-direct x-ray driven' type target irradiation.
Important new directions have opened for laser ICF in recent years following the development of 'chirped' lasers capable of ultra short pulses with powers of TW up to few PW which leads to the concept of 'fast ignition FI ' to achieve higher energy gains from target implosions. Subsequently the first author devised and presented concepts for imbedding high density condensed matter 'clusters' of deuterium into the target to obtain ultra high local fusion reaction rates Miley, Such rates are possible due to the high density of the clusters over an order of magnitude above cryogenic deuterium.
Once compressed by the implosion, the yet higher density gives an ultra high reaction rate over the cluster volume since the fusion rate is proportional to the square of the fuel density. The benefit of deuteron beam driven fast ignition is that its deposition in the target fuel will not only provide heating but also fuse with fuel as they slow down in the target. The preliminary results from recent laser-deuteron acceleration experiment at LANL were encouraging. Also, in most recent calculations, we found that a These results provide some insight into the contribution of the extra heat produced by deuteron beam-target fusion to the hot spot ignition process.
If the physics works as anticipated, this novel type of interaction foil can efficiently generate energetic deuterons during intense laser pulses. The massive yield of deuterons should turn out to be the most efficient way of igniting the DT fuel, making the dream of near-term commercialization of FI fusion more achievable. Kinetic physics in ICF : present understanding and future directions.
Kinetic physics has the potential to impact the performance of indirect-drive inertial confinement fusion ICF experiments. This review presents the assembled experimental data and simulation results to date, which indicate that the effects of long mean-free-path plasma phenomena and self-generated electromagnetic fields may have a significant impact in ICF targets.
Simulation and experimental efforts are proposed to definitively quantify the importance of these effects at ignition -relevant conditions, including priorities for ongoing study. Systematic anomalies in the National Ignition Facility implosion dataset have been identified in which kinetic physics may play a role, including inferred missing energy in the hohlraum, drive asymmetry in near-vacuum hohlraums, low areal density and high burn-averaged ion temperatures T i compared with mainline simulations, and low ratios of the DD-neutron and DT-neutron yields and inferred T i.
Finally, simulation and experimental efforts are proposed to definitively quantify the importance of these effects at ignition -relevant conditions, including priorities for ongoing study.
Inertial confinement fusion - Wikipedia
We report on investigations into the effects of suprathermal ion populations on neutron production in Inertial Confinement and Magneto-Inertial Fusion plasmas. In a recent article we showed that a suprathermal population taking the form of a power-law in energy will significantly modify the shape and width of the neutron spectrum and can dramatically increase the fusion reactivity compared to the Maxwellian case.
Specific diagnostic signatures are discussed in detail. We build on this work to include the effect of an applied magnetic field on the neutron spectra, isotropy and production rate. Finally, the impact that these modifications have on the ability to reach high fusion yields and ignition is discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. NIF has conducted beam implosion experiments with energies as high as 1.
The successful commissioning of the NIF laser is the first step in demonstrating inertial confinement fusion ICF ignition in the laboratory. The NIC relies on a novel integrated experimental and computational program to tune the target to the conditions required for indirect-drive ignition. This approach breaks the tuning process into four phases. The first two phases involve tuning of the hohlraum and capsule to produce the correct radiation drive, symmetry, and shock timing conditions.
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The reduced yield from these THD targets allows the full diagnostic suite to be employed and the presence of the required temperature and fuel areal density to be verified. The final step is DT ignition implosions with expected gains of Laser energies of 1. This talk will review the multi-phase tuning approach to the ignition effort, including the physics issues associated with the various steps, and current and future plans for the NIF ignition program.
Olson, R. An additional key physics issue relates to the complex process by which a hot spot must be dynamically formed from the inner ice surface in a DT ice-layer implosion. These physics issues have helped to motivate the development of a new liquid DT layer wetted foam platform at the NIF that provides an ability to form the hot spot from DT vapor and experimentally study and understand hot spot formation at a variety of CR's in the range of 12 ICF ignition. Low-mode asymmetries in the laser- indirect-drive inertial confinement fusion implosion experiments conducted on the National Ignition Facility [G.
Miller et al. Fusion 44, S ] are deemed the main obstacles hindering further improvement of the nuclear performance of deuterium-tritium-layered capsules. The dominant seeds of these asymmetries include the P2 and P4 asymmetries of x-ray drives and P2 asymmetry introduced by the supporting "tent. An oblate or toroidal hot spot, depending on the P2 amplitude of MFA, forms at stagnation. The energy loss of such a hot spot via electron thermal conduction is seriously aggravated not only due to the enlarged hot spot surface but also due to the vortices that develop and help transferring thermal energy from the hotter center to the colder margin of such a hot spot.
The cliffs of nuclear performance for the two methodologies of applying MFA i. ICF Annual Report The mission of the US Inertial Fusion Program is twofold: 1 to address high-energy-density physics issues for the SSP and 2 to develop a laboratory microfusion capability for defense and energy applications. The near-term goals pursued by the ICF Program in support of its mission are demonstrating fusion ignition in the laboratory and expanding the Program's capabilities in high-energy-density science.
It records absolutely-calibrated, time-integrated x-ray images with the same line-of-sight as the multi-channel, spatially integrating hard x-ray detector FFLEX [McDonald et al. The ICF program today is investigating three approaches to achieving multi-MJ fusion yields and ignition : 1 laser indirect x-ray drive on the National Ignition Facility NIF , 2 laser direct drive primarily on the Omega laser facility at the University of Rochester , and 3 magnetic direct drive on the Z pulsed power facility.
In this white paper we briefly consider a fourth approach, magnetic indirect drive , in which pulsedpower- driven x-ray sources are used in place of laser driven sources. We then show results from a series of 1D Helios calculations of double-shell capsules that suggest that these sources, scaled to higher temperatures, could be a promising path to achieving multi-MJ fusion yields and ignition.
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A review of laser-plasma interaction physics of indirect-drive fusion. Kirkwood, R. Fusion 51 , Collins et al Phys. Plasmas 19 and has recently received its most critical test yet with the inception of the NIF experiments with ignition -scale indirect-drive targets Landen et al Phys. Plasmas 17 , Edwards et al Phys.
Plasmas 18 , Glenzer et al Phys. Plasmas 18 , Landen et al Phys. Plasmas 18 , Lindl et al Nucl. Fusion 51 In this paper, the data obtained in the first complete series of coupling experiments in ignition -scale hohlraums is reviewed and compared with the preceding work on the physics of LPIs with the goal of recognizing aspects of our understanding that are confirmed by these experiments and recognizing and motivating areas that need further modeling.
Understanding these hohlraum coupling experiments is critical as they are only the first step in a campaign to study indirectly driven implosions under the conditions of ignition by inertial confinement at NIF, and in the near future they are likely to further influence ignition plans and experimental designs. New designs of LMJ targets for early ignition experiments. The LMJ experimental plans include the attempt of ignition and burn of an ICF capsule with 40 laser quads, delivering up to 1.
New targets needing reduced laser energy with only a small decrease in robustness are then designed for this purpose. A first strategy is to use scaled-down cylindrical hohlraums and capsules, taking advantage of our better understanding of the problem, set on theoretical modelling, simulations and experiments. Another strategy is to work specifically on the coupling efficiency parameter, i. An alternative design is proposed, made up of the nominal 60 quads capsule, named A, in a rugby-shaped hohlraum. Robustness evaluations of these different targets are in progress.
Boehly, D. Brown, S. Craxton et al. Cavailler, Plasma Phys. Controlled Fusion 47, ]. The modulated samples under study were made of germanium-doped plastic CHGe , which is the nominal ablator for future ignition experiments. The incident x-ray drive was provided using rugby-shaped hohlraums [M. Vandenboomgaerde, J. Bastian, A. Three-dimensional pattern growth is also compared with the 2D case. Finally the case of the feedthrough mechanism is addressed with rear-side modulated foils.
Based on time resolved imaging of the hard x-ray emission of the laser spots, this method will be used to infer hohlraum wall motion due to x-ray and laser ablation and any beam refraction caused by plasma density gradients. In this work we will compare the hard x-ray emission calculated by LASNEX and analytical modeling with thin wall imaging data recorded previously on Omega and during the first hohlraum experiments on NIF.
Effects of inhomogeneity at stagnation in 3D simulations of ICF implosions. The stagnation phase of an ICF implosion is characterized by a hotspot and dense fuel layer that are spatially and temporally inhomogeneous. Perturbation growth during the implosion results in significant asymmetry at stagnation while the hotspot size, density and temperature change rapidly, even in non- igniting capsules. Diagnosing these inhomogeneities is necessary to increase yield in ICF experiments. During the stagnation phase a suite of novel and computationally efficient simulation tools are used to produce synthetic time-resolved neutron spectra and images.
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These tools allow a detailed study of the effects of hotspot inhomogeneities on diagnostic signals. Results show that the burn-averaged ion temperature drops rapidly during thermonuclear burn as the hotspot evolves from a localised, shock-heated region to a more massive, non-uniform plasma.
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Primary DD and DT neutron spectra show that there is significant residual bulk fluid motion at stagnation, complicating the measurement of ion temperature. Different perturbation modes cause different levels of anisotropic spectra shifts and broadening. However, in all cases the discrepancies between the DD and DT spectra are a reliable indicator of residual motion at stagnation. Three measures of areal density are simulated: downscattered neutron ratio, attenuated primary neutron yield and nT backscatter edge.
A schematic of an ignition target is shown in Figure 1. The laser beams are focused through laser entrance holes at each end of a high-Z cylindrical case, or hohlraum. The lasers irradiate the hohlraum walls producing x-rays that ablate and compress the fuel capsule in the center of the hohlraum. The hohlraum is made of Au, U, or other high-Z material.
The DT fuel is in the form of a cryogenic layer on the inside of the capsule. X-rays ablate the outside of the capsule, producing a spherical implosion. The imploding shell stagnates in the center, igniting the DT fuel. NIC has overseen installation of all of the hardware for performing ignition experiments, including commissioning of approximately 50 diagnostic systems in NIF. The diagnostics measure scattered optical light, x-rays from the hohlraum over the energy range from eV to keV, and x-rays, neutrons, and charged particles from the implosion. MRS measures the neutron spectrum from the implosion, providing information on the neutron yield and areal density that are metrics of the quality of the implosion.
NIF can produce more than 50 times the laser energy and more than 20 times the power of any previous ICF facility. Ignition scale hohlraum targets are three to four times larger than targets used at smaller facilities, and the ignition drive pulses are two to five times longer. Signatures of asymmetry in neutron spectra and images predicted by three-dimensional radiation hydrodynamics simulations of indirect drive implosions. The results are post-processed using a semi-deterministic ray tracing model to generate synthetic deuterium-tritium DT and deuterium-deuterium DD neutron spectra as well as primary and down scattered neutron images.
Results with low-mode asymmetries are used to estimate the magnitude of anisotropy in the neutron spectra shift, width, and shape. Further calculations use high bandwidth multi-mode perturbations to induce multiple short scale length flows in the hotspot. The results indicate that the effect of fluid velocity is to produce a DT neutron spectrum with an apparently higher temperature than that inferred from the DD spectrum and which is also higher than the temperature implied by the DT to DD yield ratio.
To achieve hotspot ignition , inertial confinement fusion ICF implosions must achieve high hotspot internal energy that is inertially confined by a dense shell of DT fuel. To accomplish this, implosions are designed to achieve high peak implosion velocity, good energy coupling between the hotspot and imploding shell, and high areal-density at stagnation. However, experiments have shown that achieving these simultaneously is extremely challenging, partly because of inherent tradeoffs between these three interrelated requirements.
The Bigfoot approach is to intentionally trade off high convergence, and therefore areal-density, in favor of high implosion velocity and good coupling between the hotspot and shell. This is done by intentionally colliding the shocks in the DT ice layer. This results in a short laser pulse which improves hohlraum symmetry and predictability while the reduced compression improves hydrodynamic stability. The results of this campaign will be reviewed and include demonstrated low-mode symmetry control at two different hohlraum geometries 5.
Hydrodynamic instability growth from engineering features like the capsule fill tube are currently thought to be a significant perturbation to the target performance and a major factor in reducing its performance compared to calculations. Evidence supporting this hypothesis as well as plans going forward will be presented. Ongoing experiments are attempting to measure the impact on target performance from increase in target scale, and the preliminary results will also be discussed. A hybrid-drive nonisobaric- ignition scheme for inertial confinement fusion. He, X.
A new hybrid-drive HD nonisobaric ignition scheme of inertial confinement fusion ICF is proposed, in which a HD pressure to drive implosion dynamics increases via increasing density rather than temperature in the conventional indirect drive ID and direct drive DD approaches. In this HD combination of ID and DD scheme, an assembled target of a spherical hohlraum and a layered deuterium-tritium capsule inside is used.
The ID lasers first drive the shock to perform a spherical symmetry implosion and produce a large-scale corona plasma. The HD pressure is several times the conventional ID and DD ablation pressure and launches an enhanced precursor shock and a continuous compression wave, which give rise to the HD capsule implosion dynamics in a large implosion velocity.
The hydrodynamic instabilities at imploding capsule interfaces are suppressed, and the continuous HD compression wave provides main pdV work large enough to hotspot, resulting in the HD nonisobaric ignition. The ignition condition and target design based on this scheme are given theoretically and by numerical simulations. It shows that the novel scheme can significantly suppress implosion asymmetry and hydrodynamic instabilities of current isobaric hotspot ignition design, and a high-gain ICF is promising.
It requires direct-drive-specific beam smoothing, phase plates, and repointing the NIF beams toward the equator to ensure symmetric target irradiation. First experiments testing the performance of ignition -relevant PD implosions at the NIF have been performed. The goal of these early experiments was to develop a stable, warm implosion platform to investigate laser deposition and laser-plasma instabilities at ignition -relevant plasma conditions, and to develop and validate ignition -relevant models of laser deposition and heat conduction.
These experiments utilize the NIF in its current configuration, including beam geometry, phase plates, and beam smoothing. Warm, 2. Results from these initial experiments are presented, including the level of hot-electron preheat, and implosion symmetry and shell trajectory inferred via self-emission imaging and backlighting.
These simulations indicate that CBET affects the shell symmetry and leads to a loss of energy imparted onto the shell, consistent with the experimental data. Quantitative studies of kinetic effects in direct- and indirect-drive Inertial Confinement Fusion implosions. A comprehensive set of experiments using shock-driven implosions has been conducted to quantitatively study kinetic effects by exploring deviations from hydrodynamic behavior in plasmas relevant to inertial confinement fusion ICF.
In the thin-glass experiments, the gas pressure was varied from 1 to 25 atm to scan the ion-mean-free path in the plasma at shock burn. The observed nuclear yields and temperatures deviated more strongly from hydrodynamic predictions as the ion-mean-free path increased to the order of the plasma size. This result provides the first direct experimental evidence how kinetic effects impact yields and ion temperature. The ratio of D to 3He was also varied while maintaining the fuel mass density. As the D fraction was reduced, the DD and D3He fusion products displayed an anomalous yield reduction.
Finally, thin-CD shells filled with 3He produced significantly more D3He-protons when imploded than is explained by hydrodynamic mix models. This result suggests a kinetic form of mix dominates at the strongly-shocked shell-gas interface.leondumoulin.nl/language/speech/poet-tree.php
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This work was performed in collaboration with C. Li, M. Rosenberg, A. Zylstra, H. Sio, M. Gatu Johnson, F. Frenje, and R. Edward I. Moses, Robert L. McCrory, David D. Meyerhofer and Christopher J. The field of high-energy-density physics is on the verge of a revolutionary event—the achievement of fusion ignition in the laboratory. Research at the University of Rochester and Lawrence Livermore National Laboratory will enable new science to be conducted in astrophysics, materials science and laser-matter interactions.
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