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NASA NTRS2017

The Pulsed Fission-Fusion (PUFF) Concept for Deep Space Exploration and Terrestrial Power Generation

This team is exploring a modified Z-pinch geometry as a propulsion system, imploding a liner of liquid lithium onto a pellet containing both fission and fusion fuel. The plasma resulting from the fission and fusion burn expands against a magnetic nozzle, for propulsion, or a magnetic confinement system, for terrestrial power generation. There is considerable synergy in the concept; the lithium acts as a temporary virtual cathode, and adds reaction mass for propulsion. Further, the lithium acts as a radiation shield against generated neutrons and gamma rays. Finally, the density profile of the column can be tailored using the lithium sheath. Recent theoretical and experimental developments (e.g. tailored density profile in the fuel injection, shear stabilization, and magnetic shear stabilization) have had great success in mitigating instabilities that have plagued previous fusion efforts. This paper will review the work in evaluating the pellet sizes and z-pinch conditions for optimal PuFF propulsion. Trades of pellet size and composition with z-pinch power levels and conditions for the tamper and lithium implosion are evaluated. Current models, both theoretical and computational, show that a z-pinch can ignite a small (~1 cm radius) fission-fusion target with significant yield. Comparison is made between pure fission and boosted fission targets. Performance is shown for crewed spacecraft for high speed Mars round trip missions and near interstellar robotic missions. The PuFF concept also offers a solution for terrestrial power production. PuFF can, with recycling of the effluent, achieve near 100% burnup of fission fuel, providing a very attractive power source with minimal waste. The small size of PuFF relative to today's plants enables a more distributed power network and less exposure to natural or man-made disruptions.

Adams, Robert↗

NASA NTRS2018

Preliminary Analysis of the Gradient Field Imploding Liner Fusion Propulsion Concept

The advancement of human deep space exploration requires the continued development of energetic in-space propulsion systems, advancing from current chemical engines to nuclear thermal rockets to future high energy concepts such as nuclear fusion. This paper presents the initial results of a NASA Innovative Advanced Concepts (NIAC) Phase I study funded to investigate the feasibility of a new pulsed fusion propulsion concept based on the rapid implosion of a fuel target injected at high velocity into a strong stationary magnetic field. The proposed concept takes advantage of the significant advances in terrestrial magneto-inertial fusion designs while attempting to mitigate the most common engineering impediments to in-space propulsion applications. A semi-analytic numerical model used to estimate target compression physics and energy release is presented, leading to estimates for engine performance. A preliminary vehicle design concept is outlined, and representative trajectory analyses for rapid Mars and Saturn missions are provided. The paper concludes with an overview of proposed next steps for theoretical and experimental validation of the concept.

Propulsion↗

NASA NTRS2018

The Fusion Driven Rocket: Nuclear Propulsion through Direct Conversion of Fusion Energy

The future of manned space exploration and development of space depends critically on the creation of a dramatically more efficient propulsion architecture for in-space transportation. A very persuasive reason for investigating the applicability of nuclear power in rockets is the vast energy density gain of nuclear fuel when compared to chemical combustion energy. The Fusion Driven rocket (FDR) represents a revolutionary approach to fusion propulsion where the power source releases its energy directly into the propellant, not requiring conversion to electricity. It employs a solid lithium propellant that requires no significant tankage mass. The propellant is rapidly heated and accelerated to high exhaust velocity (> 30 km/s), while having no substantial physical interaction with the spacecraft thereby avoiding damage to the rocket and limiting both the thermal heat load and radiator mass. The key to achieving this stems from research at MSNW and the UW on the magnetically driven implosion of metal foils onto a magnetized plasma target to obtain fusion conditions. A logical extension of this work leads to a method that utilizes these metal shells (or liners) to not only achieve fusion conditions, but to serve as the propellant as well. Several low-mass, magnetically driven metal liners are inductively driven to converge radially and axially and form a thick blanket surrounding the target plasmoid and compress the plasmoid to fusion conditions. Virtually all of the radiant, neutron and particle energy from the plasma is absorbed by the encapsulating, thick metal blanket thereby isolating the spacecraft from the fusion. This energy, in addition to the intense Ohmic heating at peak magnetic field compression, is adequate to vaporize and ionize the metal blanket. The expansion of this hot, ionized metal propellant through a magnetically insulated nozzle produces high thrust at the optimal Isp. The energy from the fusion process, along with the waste heat, is thus utilized at very high efficiency. The basic scheme for FDR is illustrated and described in the report (see Fig. 2) The two most critical issues in meeting challenges introduced employing magneto-inertial fusion as the power source is driver efficiency and “stand-off” – the ability to isolate and protect fusion and thruster from the resultant fusion energy. By employing metal shells for compression, it is possible to produce the desired convergent motion inductively by inserting the metal sheets along the inner surface of cylindrical or conically tapered coils. Both stand-off and energy efficiency issues are solved by this arrangement. 3 This two year effort focused on achieving three key criteria for the Fusion Driven Rocket to move forward for technological development: (1) the physics of the FDR must be fully understood and validated, (2) the design and technology development for the FDR required for its implementation in space must be fully characterized, and (3) an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. A subscale, laboratory liner compression test facility was assembled at the University of Washington Plasma Dynamics Laboratory with sufficient liner kinetic energy (~ 0.5 MJ) to reach conditions required for fusion breakeven conditions. Detailed experimental studies of the dynamic behavior of the driven liners as well as liner convergence and magnetic compression were performed. The development of both the 1D liner dynamics code and the full 3D ANSYS® liner calculations was achieved. The characterization of both the FDR and spacecraft as well as a design architecture analysis was conducted that included an examination of a wide range of mission architectures and destinations for which this fusion propulsion system would be enabling or critical. In particular a rapid, single launch manned Mars mission was developed.

Energy↗

DOE OSTI2014

44th Annual Anomalous Absorption Conference

Conference Grant Report July 14, 2015 Submitted to the U. S. Department of Energy Attn: Dr. Sean Finnegan By the University of California, San Diego 9500 Gilman Drive La Jolla, California 92093 On behalf of the 44th Annual Anomalous Absorption Conference 8-13 June 2014, in Estes Park, Colorado Support Requested: $10,100 Amount expended: $3,216.14 Performance Period: 1 March 20 14 to 28 February 20 15 Principal Investigator Dr. Farhat Beg Center for Energy Research University of California, San Diego 9500 Gilman Drive La Jolla, California 92093-0417 858-822-1266 (telephone) 858-534-4543 (fax) fbeg@ucsd.edu Administrative Point of Contact: Brandi Pate, 858-534-0851, blpate®ucsd.edu I. Background The forty-fourth Anomalous Absorption Conference was held in Estes Park, Colorado from June 5-8, 2014 (aac2014.ucsd.edu). The first Anomalous Absorption Conference was held in 1971 to assemble experts in the poorly understood area of laser-plasma absorption. The goal of that conference was to address the anomalously large laser absorption seen in plasma experiments with respect to the laser absorption predicted by linear plasma theory. Great progress in this research area has been made in the decades since that first meeting, due in part to the scientific interactions that have occurred annually at this conference. Specifically, this includes the development of nonlinear laser-plasma theory and the simulation of laser interactions with plasmas. Each summer since that first meeting, this week-long conference has been held at unique locations in North America as a scientific forum for intense scientific exchanges relevant to the interaction of laser radiation with plasmas. Responsibility for organizing the conference has traditional rotated each year between the major Inertial Confinement Fusion (ICF) laboratories and universities including LANL, LLNL, LLE, UCLA UC Davis and NRL. As the conference has matured over the past four decades, its technical footprint has expanded beyond ICF-related laser-plasma interactions to encompass closely related technical areas including laser particle acceleration, high-intensity laser effects, short pulse laser interactions, PIC and Vlasov/rad-hydro modeling, inertial and magnetic fusion plasmas, advanced plasma diagnostics, alternate ignition schemes, EOS/transport/opacity, and this year, x ray free-electron lasers and their applications. The conference continues to be a showcase for the presentation and discussion of the latest developments in these areas. II. Meeting Report The conference was extremely successful with more than one hundred participants. There were ninety-nine (99) abstracts submitted. There were forty-four (44) presentations including eleven (11) invited talks. The following topics were covered: a) Radiation Hydrodynamics b) Implosion Plasma Kinetic Effects c) Alternate Ignition Schemes d) Astrophysical Phenomena e) Opacity/Transport/EOS f) High Power Lasers and Facilities g) High-Intensity Laser-Matter Interactions h) Hydrodynamics and Hydro-instabilities i) Hot Dense Plasma Atomic Processes j) High Energy Density Physics k) Laser Particle Acceleration Physics l) Advanced Plasma Diagnostics m) Advanced light sources and applications Despite significant advertising, there were two students who applied for the travel grants: Charlie Jarrott and Joohwan Kim. The total funds expended were $3,216.14.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2017

Staged Z-pinch for the production of high-flux neutrons and net energy

A fusible target is embedded in a high Z liner, ohmically heated and then shock wave heated by implosion of an enveloping high Z liner. The target is adiabatically heated by compression, fusibly ignited and charged-particle heated as it is being ignited. A shock front forms as the liner implodes which shock front detaches from the more slowly moving liner, collides with the outer surface of the target, accelerates inward, rapidly heating the target, adiabatically compressing the target and liner and amplifying the current to converge the liner mass toward a central axis thereby compressing the target to a fusion condition when it begins to ignite and produce charged particles. The charged particles are trapped in a large magnetic field surrounding the target. The energy of the charged particles is deposited into the target to further heat the target to produce an energy gain.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2015

Low Adiabat Compression of Liquid Deuterium Filled Cylindrical Liners to 0.1?2 Gbar.

We report on experiments where cylindrical beryllium liners filled with liquid deuterium were compressed to extreme pressure and density with current pulse shaping. In one set of experiments the pressure at stagnation is inferred to be & 100 Mbar using penetrating radiography. A peak liner convergence ratio (initial radius over final radius) of 7.6 was measured resulting in an average deuterium density of 10 g=cm 3 and areal density of 0.45 g=cm 2 . The stagnation shock propagating radially outward through the liner wall was directly measured with a strength of ≈ 120 Mbar. In a second set of experiments the liner was imploded to a peak convergence of 19 resulting in a density of 55 g=cm 3 and areal density of 0.5 g=cm 2 . The pressure at stagnation in this experiment is estimated to be 2 Gbar. This platform enables the study of high-pressure, high-density, implosion deceleration and stagnation dynamics at spatial scales that are readily diagnosable (R ~ 0.1 -- 0.4 mm). Thus, these experiments are directly relevant to both Inertial Con nement Fusion and the study of material properties under extreme conditions.

Knapp, Patrick↗

DOE OSTI2018

Methods and systems for imaging bulk motional velocities in plasmas

A method and apparatus for imaging the distribution of bulk motional velocities in plasmas such as inertial confinement fusion (ICF) implosions. This method and apparatus use multiple narrow-band x-ray crystal imaging systems, one or more of which have a bandpass tuned to lie within the Doppler-broadened emission line profile of a suitable plasma emission line. Crystals tuned on the one end of the profile will preferentially reflect x-rays from plasma ions moving towards the crystals, while crystals tuned to another end of the profile will preferentially reflect x-rays from plasma ions moving away from the crystals.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Development of Platforms for Nuclear Science Experiments at the National Ignition Facility

When neutrons are produced in nuclear processes such as fission or fusion, they can interact with any surrounding materials, inducing radioactivity through neutron capture reactions. Neutron reactions are fundamental to many areas of nuclear science, including studies of nuclear reactors, determining the formation of matter in stars, nuclear forensics, medical radiotherapy, and assessing the safety of our nuclear stockpile. The National Ignition Facility (NIF) offers a unique opportunity to use the inertial confinement fusion platform to measure neutron reactions essential to national security or fundamental and applied science applications. A typical fusion experiment at NIF currently produces approximately 10 16 neutrons through the fusion of deuterium and tritium in a target capsule. Materials introduced into the NIF target chamber in close proximity to the capsule will undergo neutron reactions such as capture or fission, and the resultant reaction rates can be evaluated. While neutron reactions can be measured at other facilities, NIF offers unique advantages. The flux of neutrons produced (number of neutrons per square centimeter per second) is much higher than any other available neutron source due to both the small size of the NIF capsule (2-mm diameter before implosion) and the short time (roughly 100 ps) over which the neutrons are produced. This results in less target material required to perform a reaction-rate study (less than or equal to 10 16 atoms) as compared to traditional particle accelerators, which require targets that are approximately 1 mg or roughly 10 20 atoms. Also, the NIF neutron spectrum is peaked at thermonuclear (14 MeV) neutron energy, which means that nuclear reactions with nonthermal energy thresholds can be studied at NIF, whereas neutron energies at a nuclear reactor are generally insufficient for studying higher-energy neutron reactions. Several experimental configurations have been developed that enable the use of NIF fusion capsules as powerful neutron sources for nuclear reaction measurements.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2018

Application of compressed magnetic fields to the ignition and thermonuclear burn of inertial confinement fusion targets

Application of axial seed magnetic fields in the range 20-100 T that compress to greater than 10,000 T (100 MG) under typical NIF implosion conditions may significantly relax the conditions required for ignition and propagating burn in NIF ignition targets that are degraded by hydrodynamic instabilities. Such magnetic fields can: (a) permit the recovery of ignition, or at least significant alpha particle heating, in submarginal NIF targets that would otherwise fail because of adverse hydrodynamic instability growth, (b) permit the attainment of ignition in conventional cryogenic layered solid-DT targets redesigned to operate under reduced drive conditions, (c) permit the attainment of volumetric ignition in simpler, room-temperature single-shell DT gas capsules, and (d) ameliorate adverse hohlraum plasma conditions during laser drive and capsule compression. In general, an applied magnetic field should always improve the ignition condition for any NIF ignition target design.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Is GW170817 a Multimessenger Neutron Star-Primordial Black Hole Merger?

We investigate the possibility of the gravitational-wave event GW170817 being a light, solar-mass black hole (BH) - neutron star (NS) merger. We explore two exotic scenarios involving primordial black holes (PBH) that could produce such an event, taking into account available observational information on NGC 4993. First, we entertain the possibility of dynamical NS-PBH binary formation where a solar-mass PBH and a NS form a binary through gravitational interaction. We find that while dynamical NS-PBH formation could account for the GW170817 event, the rate is highly dependent on unknown density contrast factors and could potentially be affected by galaxy mergers. We also find that PBH-PBH binaries would likely have a larger merger rate, assuming the density contrast boost factor of an order similar to the NS-PBH case. These exotic merger formations could provide new channels to account for the volumetric rate of compact-object mergers reported by LIGO/Virgo. Secondly, we consider the case where one of the NS's in a binary NS system is imploded by a microscopic PBH. We find that the predicted rate for NS implosion into a BH is very small, at least for the specific environment of NGC 4993. We point out that similar existing (e.g. GW190425 and GW190814) and future observations will shed additional light on these scenarios.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Evaluating turbulence models at high energy densities

The RESHOCK campaign at Lawrence Livermore National Laboratory has been working on increasing our understanding of the evolution of turbulent, unstable plasma interfaces which are applicable in various HED applications including ICF implosions. A common approach to model such interfaces involves the use of Renolds-Averaged-Navier-Stokes (RANS) models whose parameters have been constrained by theory and experiments. These parameter sets are not unique and the applicability of one set of tuned model parameters to systems with differing shock strengths or material densities has not been well tested. Our new NIF experiments, along with related studies of turbulent shear flows, provide data and model validation for plasma interfaces in the HED regime. Our experiments measure mixing-layer width at an unstable interface in the plasma regime and are specifically designed to challenge mix models of the Reynolds-Averaged-Navier-Stokes (RANS) type where turbulence is assumed to be fully developed, i.e. the flow exhibits a broad spectrum of length scales without memory of the initial condition.4 We utilize precise control of the initial interface conditions (densities on both sides of the interface, an initial rippled perturbation pattern consisting of equally weighted wavelengths between 10 and 20 microns, and initial material compositions) along with a repeatable drive history

36 MATERIALS SCIENCE↗

DOE OSTI2022

Hohlraum used as a single turn solenoid to generate seed magnetic field for inertial confinement fusion

Perkins, Lindsay John↗

DOE OSTI2023

Converging towards atomic and nuclear pressures (Final Report)

his report details the development of transformational tools and techniques, allowing the accurate characterization of matter at the most extreme conditions yet studied in the high energy density (HED) domain. Before this work, most experiments quantitatively mapping the nature of matter in the HED realm were performed using planar geometry, which allows for the isolation and measurement of variables in a single thermodynamic state. Such measurements include equation of state variables, optical conductivity, heat transport and more. However, due to a variety of plasma processes, such experiments are limited to below ~10 TPa (100 Mbar) pressures. To achieve higher pressures, convergent experiments are needed. Historically, convergent experiments have not been used for benchmark data because they are integral measurements. That is each part of a convergent target undergoes a time dependent wide range of states, making it difficult to accurately isolate any particular quantity for a given thermodynamic state. This effort developed innovative convergent HED platforms and techniques enabling the exploration of matter from atomic to nuclear scale pressures. This effort also performed pioneering experiments that yielded the first rigorous benchmark data at these extreme conditions. This funding award began with the overarching goal to understand the behavior of matter at extreme (atomic-to-nuclear scale) pressures. The motivation for these goals lie in the fact that every time scientists explore matter beyond the threshold of an atomic unit, there is a fundamental shift in science. The atomic unit for energy, mass, charge, length, and time have each been explored, and each time such a threshold was crossed, a new sequence of discoveries was made resulting in significant awards such as the Nobel Prize. The only unexplored atomic unit is pressure, and this effort set the course for exploring matter at and beyond such pressures. That most of the recently discovered extrasolar planets and stars, as well as matter in the late implosion stages of inertial fusion targets, have deep internal pressures at and beyond atomic pressures amplifies the importance of this effort. Much of the initial work in developing techniques to create these atomic-to-nuclear pressures already existed within the HED community, predominantly at large scale laser facilities such as the National Ignition Facility (NIF) and the Omega60 laser the University of Rochester and although these experiments were routinely performed the ability to extract information about the underlying physical states and processes remained elusive due to the complexity of the experiments, extreme scales in both time and space, and the integrated nature of all the measurements. This work built a rigorous framework so such measurements can routinely be made. This was done in part through the introduction of Bayesian inference techniques into the field of HED science. These techniques allow for the self-consistent extraction of the relevant variables and their explicit and implicit correlations, so as to make use of integrated experimental data to constrain physical models and provide accurate uncertainty bounds for the data. The techniques developed here are fully transparent and proved immediately useful providing quantitative rigorous benchmarks for physical states and processes at some of the most extreme conditions yet explored on Earth. This funding is directly or partly responsible for 7 publications in major peer-reviewed scientific journals, a doctoral thesis, 3 invited talks at major conferences, and the training of a post-doc, 2 graduate students, and 1 undergraduate student. Beyond the effort supported by this award launched the introduction of Bayesian inference into the HED physics community and helped push the usage if modern data-science techniques within the physics community at large.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2023

Hohlraum used as a single turn solenoid to generate seed magnetic field for inertial confinement fusion

Perkins, Lindsay John↗

DOE OSTI2022

Beam Spray Thresholds in ICF-Relevant Plasmas

Beam spray measurements suggest thresholds that are a factor of ≈2 to 15× less than expected based on the filamentation figure of merit often quoted in the literature. In this moderate-intensity regime, the relevant mechanism is forward stimulated Brillouin scattering (FSBS). Both weak ion acoustic wave damping and thermal enhancement of ion acoustic waves contribute to the low thresholds. FSBS imparts a redshift to the transmitted beam. Here, regarding the specific possibility of beam spray occurring outside the laser entrance holes of an indirectly driven hohlraum, this shift may be the most concerning feature owing to the high sensitivity of crossed-beam energy transfer to the interacting beam wavelengths in the subsequent overlap region.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound

Not Available

36 MATERIALS SCIENCE↗

DOE OSTI2024

How ignition and target gain > 1 were achieved in inertial fusion

For many decades the running joke in fusion research has been that “fusion” is twenty years away and always will be. Yet, in 2023 we find ourselves in a position where we can talk about the milestones of burning plasmas, fusion ignition, and target energy gain greater than unity in the past tense – a situation that is remarkable! Herein this paper tells some of the story of the applied physics challenges that needed to be overcome to achieve these milestones and the strategy our team followed. Things did not always go well and some practical lessons learned are part of this story. The data shows, getting to a burning plasma in late 2020 and early 2021 was a key tipping-point, after which ignition (August 8, 2021) and target gain (December 5, 2022) were rapidly achieved.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2013

Optimization of beam configuration in laser fusion based on the laser beam pattern

A simple method based on the laser beam pattern is proposed and numerically demonstrated to optimize a beam configuration for direct drive laser fusion. In this method, both the geometrical factor G{sub l} and the single beam factor B{sub l} are considered. By diminishing the product of B{sub l}·G{sub l}, the irradiation nonuniformity can be decreased to the order of 10{sup −5}. This optimization method can be applied on the design of irradiation systems for an arbitrary number of beams and any axially symmetric beam patterns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗