Fusion Energy Source Research Articles

Focus Fusion: Overview of Progress Towards p-B11 Fusion with the Dense Plasma Focus

LPPFusion is developing a source of fusion energy using the dense plasma focus device and p-B11 fuel, a combination we call Focus Fusion. So far, this project has led to the achievement of the highest confined ion energies of any fusion experiment (> 200 keV) as well as, recently, the lowest impurities of any fusion plasma. Among privately-funded fusion efforts, our experiments have achieved the highest ratio of fusion energy generation to device energy input (wall-plug efficiency) and the highest nτT product of 3.4 × 1020 keV-s/m3. Our calculations and simulations indicate that the quantum magnetic field effect will allow a great reduction in bremsstrahlung radiation with p-B11 fuel. For commercial fusion, this approach has several major advantages. The small size and simplicity of design of the DPF can lead to 5 MW generators that are much cheaper than any existing energy source, that can be manufactured by mass production and that can be located close to loads. It shares with other p-B11 approaches a lack of neutron damage and radioactive waste. Direct energy conversion of the ion beam and x-rays produced by the device avoids the high costs associated with thermal cycles. With adequate, but still modest, financial resources we anticipate working prototype generators could be ready for production by 2026–2030.

Proton-beam driver transport in the fast ignition of proton–boron-11 fuel plasma

The invention of Chirped Pulse Amplification lasers along with the development of fast ignition methods have made fuels such as proton–boron-11 seem promising nuclear fusion energy sources because of their lack of high-energy neutrons and abundance of constituent isotopes. This paper investigates the transport of charged particles in proton–boron-11 fuel. In this study, the confinement parameter has been estimated as [Formula: see text] g/cm2 with the help of a proton driver in the fast ignition method for proton–boron-11 fuel pellets, with a ratio of boron-11 to proton [Formula: see text]. Subsequently, using the Li–Petrasso stopping-power model, the energy deposition coefficients of the accelerated proton-beam driver were calculated by the Target Normal Sheath Acceleration method with 1 MeV energy. The obtained results show that at a temperature of about 65 keV, the proton-beam driver with 1 MeV energy deposits about 85% of its energy in the hot spot area of 2.5 [Formula: see text]m depth from the surface of the fuel pellet to ignite the proton–boron-11 fuel pellet.

Modeling the complete prevention of disruption-generated runaway electron beam formation with a passive 3D coil in SPARC

The potential formation of multi-mega-ampere beams of relativistic ‘runaway’ electrons (REs) during sudden terminations of tokamak plasmas poses a significant challenge to the tokamak’s development as a fusion energy source. Here, we use state-of-the-art modeling of disruption magnetohydrodynamics coupled with a self-consistent evolution of RE generation and transport to show that a non-axisymmetric in-vessel coil will passively prevent RE beam formation during disruptions in the SPARC tokamak, a compact, high-field, high-current device capable of achieving a fusion gain Q > 2 in deuterium–tritium plasmas.

Towards validated multiscale simulations for fusion.

Harnessing energy produced by thermonuclear fusion reactions has the potential to provide a clean and inexpensive source of energy to Earth. However, throughout the past seven decades, physicists learned that creating our very own fusion energy source is very difficult to achieve. We constructed a component-based, multiscale fusion workflow to model fusion plasma inside the core of a tokamak device. To ensure the simulation results agree with experimental values, the model needs to undergo the process of verification, validation and uncertainty quantification (VVUQ). This paper will go over the VVUQ work carried out in the multiscale fusion workflow (MFW), with the help of the EasyVVUQ software library developed by the VECMA project. In particular, similarity of distributions from simulation and experiment is explored as a validation metric. Such initial validation measures provide insights into the accuracy of the simulation results. This article is part of the theme issue 'Reliability and reproducibility in computational science: implementing verification, validation and uncertainty quantification in silico'.

Response to “Comment on ‘The staged Z-pinch as a potential fusion energy source’” [Phys. Plasmas 28, 014701 (2020)

Response to “Comment on ‘The staged Z-pinch as a potential fusion energy source’” [Phys. Plasmas <b>28</b>, 014701 (2020)

Comment on “The staged z-pinch as a potential fusion energy source” [Phys. Plasmas 27, 042709 (2020)

Analysis is presented that shows that the recent paper by Ruskov et al. [Phys. Plasmas 27, 042709, (2020)] has a number of errors. In particular, it is shown that the Mach2 code, as used in the paper, behaves in a number of nonphysical ways.

The staged Z-pinch as a potential fusion energy source

A staged Z-pinch is a fusion concept where a high atomic number liner compresses a fusion fuel (deuterium–deuterium or deuterium–tritium) target. Here, we report new results from Lagrangian, Eulerian, and Arbitrary Lagrangian–Eulerian simulations, which confirm that, with proper treatment of the vacuum region outside from the pinch, fusion energy production &amp;gt;1 MJ can be expected without alpha heating and significantly higher if alpha heating is included. It is shown that shock waves play an important role in preheating the target plasma and in piling up liner mass at the liner/target interface. This results in higher ram pressure just before the pinch stagnation time and ultimately in higher energy density target plasma.

The Solar Clock

AbstractThe Sun is powered by a very stable source of fusion energy in its core that radiates that energy outward in a constant flow. Yet it has a cycle of magnetic dynamo activity whose strength and duration are variable. This variability, which affects the Earth's “space climate,” points to temporal changes in the convective and diffusive transport of magnetic flux above the tachocline, where the flux is generated. The longest record we have of this variability is the time series of sunspot numbers. This record suggests that the interior of the Sun follows a clock‐like magnetic flux production cycle with a length of close to 11.05 years. The variations in sunspot cycle duration, as well as the sunspot number rise and fall times, their hemispheric asymmetries, and the maximum sunspot numbers of the individual cycles are likely produced in the process of the magnetic flux transport. Helioseismology continues to shed more light on the convection zone variabilities, including the “torsional oscillations” that seem to have a special connection to the emerging strong magnetic fluxes that produce the sunspots. These new observations may eventually lead to an explanation for the surprisingly good correlation between the rate of sunspot appearance and the maximum sunspot number and to a better understanding of the relationship between the solar dynamo and the sunspot number cycle. Better understanding of the polar regions awaits long‐term monitoring with a polar solar mission. Better predictions of near‐term space weather could be obtained from a permanent L5 monitor.

The staged z-pinch as a potential high gain fusion energy source: An independent review, a negative conclusion

Previously published calculations predict that the “staged z-pinch” (SZP) can achieve 400 MJ of fusion yield on a Z-class machine. The SZP is touted to need no external preheat mechanism and no external pre-magnetization method. Instead, it is claimed that the imploding liner can adequately “shock preheat” the fuel and magnetic field diffusion through the liner can adequately magnetize the fuel. In this paper, we analyze a number of published SZP calculations and demonstrate that the calculations have major errors—the computer code used to do the calculations does not appear to be accurately solving the physical model it is intended to solve. A variety of independent analyses lead to this conclusion. This conclusion is confirmed by detailed one-dimensional magnetohydrodynamic (MHD) calculations conducted on different computer codes using a variety of proposed SZP operating parameters. Although using parameters similar or identical to the published calculations, our MHD calculations do not reach fusion conditions; there is no conceivable modification of the parameters that would lead to high-gain fusion conditions using these other codes. Our analyses and a review of the magnetized target parameter space leads to further conclusion that the SZP should not be considered to be a potential high-gain fusion source.

Impurity transport and bulk ion flow in a mixed collisionality stellarator plasma

The accumulation of impurities in the core of magnetically confined plasmas, resulting from standard collisional transport mechanisms, is a known threat to their performance as fusion energy sources. Whilst the axisymmetric tokamak systems have been shown to benefit from the effect of temperature screening, that is an outward flux of impurities driven by the temperature gradient, impurity accumulation in stellarators was thought to be inevitable, driven robustly by the inward pointing electric field characteristic of hot fusion plasmas. We have shown in Helander et al. (Phys. Rev. Lett., vol. 118, 2017a, 155002) that such screening can in principle also appear in stellarators, in the experimentally relevant mixed collisionality regime, where a highly collisional impurity species is present in a low collisionality bulk plasma. Details of the analytic calculation are presented here, along with the effect of the impurity on the bulk ion flow, which will ultimately affect the bulk contribution to the bootstrap current.

Space development and space science together, an historic opportunity

The national space programs have an historic opportunity to help solve the global-scale economic and environmental problems of Earth while becoming more effective at science through the use of space resources. Space programs will be more cost-effective when they work to establish a supply chain in space, mining and manufacturing then replicating the assets of the supply chain so it grows to larger capacity. This has become achievable because of advances in robotics and artificial intelligence. It is roughly estimated that developing a lunar outpost that relies upon and also develops the supply chain will cost about 1/3 or less of the existing annual budgets of the national space programs. It will require a sustained commitment of several decades to complete, during which time science and exploration become increasingly effective. At the end, this space industry will capable of addressing global-scale challenges including limited resources, clean energy, economic development, and preservation of the environment. Other potential solutions, including nuclear fusion and terrestrial renewable energy sources, do not address the root problem of our limited globe and there are real questions whether they will be inadequate or too late. While industry in space likewise cannot provide perfect assurance, it is uniquely able to solve the root problem, and it gives us an important chance that we should grasp. What makes this such an historic opportunity is that the space-based solution is obtainable as a side-benefit of doing space science and exploration within their existing budgets. Thinking pragmatically, it may take some time for policymakers to agree that setting up a complete supply chain is an achievable goal, so this paper describes a strategy of incremental progress. The most crucial part of this strategy is establishing a water economy by mining on the Moon and asteroids to manufacture rocket propellant. Technologies that support a water economy will play an important role leading toward space development.

Design, microfabrication and measurement of cooling arm for fusion energy source application

The novel cooling arm plays an important role in thermal transfer in the production process of fusion energy. Its structure is designed and simulated by a finite element method. The result shows that the structure with two branches can obtain a temperature difference less than 1 mK among the grip surfaces of all the fingers. A (111) crystal orientation silicon is deployed to fabricate the cooling arm, because of its isotropic Young's modulus. The thermal conductivity of this material is measured by a Gifford-McMahon (GM) cooler. The result shows it has large thermal conductivity at cryogenic temperature, which excellently contributes to heat transfer. The cooling arm is obtained by a microfabrication process. With a uniform pattern width mask and optimised deep reactive ion etching process recipe, a nearly 90° vertical sidewall is obtained. The temperature distribution of the cooling arm is also measured by a GM cooler, and the result shows that the maximum temperature deviation is 0.48 mK among the 16 fingers. There is a good agreement between finite element analysis and the experimental result.

Microfabrication of cooling arm for fusion energy source application

The cooling arm plays an important role in the production process of fusion energy. The structure is designed with 16 fingers and is simulated by the finite-element method. The (111) crystal orientation silicon is deployed to fabricate a cooling arm, because of its isotropic Young's modulus. It can make the fingers generate a uniform force. The silicon also has a large thermal conductivity of 2400 W/mK measured by a Gifford-McMahon cooler, which contributes to heat transfer. The cooling arm is fabricated by the microfabrication process, and it has a high sidewall vertical degree of 90 ± 0.5° measured by scanning electron microscopy. The mechanical testing result shows that the maximum stress of the clamping arm was 0.209 GPa when it was in gripping state. The maximum stress is far smaller than the yield strength of 7 GPa of silicon material.

Value Modeling for a Space Launch System

Spacecraft and launch systems are examples of complex products which require a careful balance between competing concerns, such as performance, weight, and reliability, to serve their mission. This paper proposes that an economic analysis of all parties to spacecraft launch and operation can be used to construct a top-level value function on the launch system attribute space. A baseline value model was developed for a scenario involving a Lunar Helium-3 (He3) mining business venture, based on the potential for He3 as a source of fusion energy, and initial results show the model's viability. Continued effort on the model will determine the relationship between the attributes of a space launch system and overall value. These relationships will be captured on a response surface, identifying the direction of maximum value. This space launch system value model has implications for use in system trade studies, technology evaluation, and design optimization.

Module of lithium divertor for KTM tokamak

Activity on projects of ITER and DEMO reactors has shown that solution of problems of divertor target plates and other plasma facing elements (PFEs) based on the solid plasma facing materials cause serious difficulties. Problems of PFE degradation, tritium accumulation and plasma pollution can be overcome by the use of liquid lithium–metal with low Z. Application of lithium will allow to create a self-renewal and MHD stable liquid metal surface of the in-vessel devices possessing practically unlimited service life; to reduce power flux due to intensive re-irradiation on lithium atoms in plasma periphery that will essentially facilitate a problem of heat removal from PFE; to reduce Zeff of plasma to minimally possible level close to 1; to exclude tritium accumulation, that is provided with absence of dust products and an opportunity of the active control of the tritium contents in liquid lithium. Realization of these advantages is based on use of so-called lithium capillary-porous system (CPS) – new material in which liquid lithium fill a solid matrix from porous material. The progress in development of lithium technology and also activity in lithium experiments in the tokamaks TFTR, T-11M, T-10, FTU, NSTX, HT-7 and stellarator TJ II permits of solving the problems in development of steady-state operating lithium divertor module project for Kazakhstan tokamak KTM. At present the lithium divertor module for KTM tokamak is under development in the framework of ISTC project # K-1561. Initial heating up to 200°C and lithium surface temperature stabilization during plasma interaction in the range of 350–550°C will be provided by external system for thermal stabilization due to circulation of the Na–K heat transfer media. Lithium filled tungsten felt is offered as the base plasma facing material of divertor. Development, creation and experimental research of lithium divertor model for KTM will allow to solve existing problems and to fulfill the basic approaches to designing of lithium divertor and in-vessel elements of new fusion reactor generation, to investigate plasma physics aspects of lithium influence, to develop technology of work with lithium in tokamak conditions. Results of this project addresses to the progress in the field of fusion neutrons source and fusion energy source creation.

Diagnostics for magnetic confinement fusion research

Significant progress towards the development of an attractive fusion energy source based on magnetic or inertial plasma confinement has been achieved within the international fusion energy program. High-level diagnostics capabilities are required to characterize fusion plasmas and to achieve a sound physics basis to design a fusion power plant. A large variety of different measuring techniques is used, most of them based on the detection of electromagnetic radiation in a wide range of wavelengths or of particles emitted from the plasma. Active probing by laser and particle beams permits to measure local plasma parameters directly, whereas passive measurements and imaging methods require unfolding and tomographic reconstruction techniques in order to obtain the spatial source distribution. Most diagnostics systems are limited in the accessible parameter range, in accuracy, temporal and spatial resolution, energy resolution and hardiness in a harsh environment, so that redundancy and complementarity of different methods is desirable. A considerable synergy exists between plasma diagnostics for fusion and astrophysics research. In particular, novel imaging detectors developed for the observation of astrophysical objects may be applied to fusion devices, too. An overview of diagnostics requirements, measuring techniques and selected results are presented with an emphasis of imaging diagnostics in toroidal magnetic fusion devices.

Parameter study of the LIFE engine nuclear design

LLNL is developing the nuclear fusion based Laser Inertial Fusion Energy (LIFE) power plant concept. The baseline design uses a depleted uranium (DU) fission fuel blanket with a flowing molten salt coolant (flibe) that also breeds the tritium needed to sustain the fusion energy source. Indirect drive targets, similar to those that will be demonstrated on the National Ignition Facility (NIF), are ignited at ∼13 Hz providing a 500 MW fusion source. The DU is in the form of a uranium oxycarbide kernel in modified TRISO-like fuel particles distributed in a carbon matrix forming 2-cm-diameter pebbles. The thermal power is held at 2000 MW by continuously varying the 6Li enrichment in the coolants. There are many options to be considered in the engine design including target yield, U-to-C ratio in the fuel, fission blanket thickness, etc. Here we report results of design variations and compare them in terms of various figures of merit such as time to reach a desired burnup, full-power years of operation, time and maximum burnup at power ramp-down and the overall balance of plant utilization.

Fusion Peptide from Influenza Hemagglutinin Increases Membrane Surface Order: An Electron-Spin Resonance Study

A spin-labeling study of interactions of a fusion peptide from the hemagglutinin of the influenza virus, wt20, and a fusion-inactive mutant ΔG1 with dimyristoylphosphatidylcholine (DMPC) and 1-palmitoyl-2-oleoyl-phosphatdylcholine bilayers was performed. We found that upon binding of wt20, the ordering of headgroups and the ordering of acyl chains near the headgroup increased significantly, in a manner consistent with a cooperative phenomenon. However, changes in the order at the end of the acyl chains were negligible. The ordering effect of wt20 on the headgroup was much stronger at pH 5 than at pH 7. No effect of ΔG1 binding on the order of bilayers was evident. We also found that 1-palmitoyl-2-hydroxyl phosphatidylcholine, a membrane-fusion inhibitor, decreased the ordering of DMPC headgroups, whereas arachidonic acid, a membrane-fusion promoter, increased the ordering of DMPC headgroups. These results suggest that increases in headgroup ordering may be important for membrane fusion. We propose that upon binding of wt20, which is known to affect only the outer leaflet of the bilayer, this outer leaflet becomes more ordered, and thus more solid-like. Then the coupling between the hardened outer leaflet and the softer inner leaflet generates bending stresses in the bilayer, which tend to increase the negative curvature of the bilayer. We suggest that the increased ordering in the headgroup region enhances dipolar interactions and lowers electrostatic energy, which may provide an energy source for membrane fusion. Possible roles of bending stresses in promoting membrane fusion are discussed.

Photon coupling theory for plasmas with strong Compton scattering: Four temperature theory

When an equimolar mixture of deuterium (D) and tritium (T) at high density undergoes fusion burn, the system becomes extremely nonequilibrium. The ion temperature rises much higher than the electron temperature which, in turn, is much higher than the radiation temperature. Accurately simulating this nonequilibrium burn process has previously required a multigroup representation of the radiation field. Although simulating this D–T burn with a simple three temperature model (3T) also results in significant departures from thermal equilibrium, the ion and electron temperature histories from the 3T simulations are much lower than from the multigroup simulations. In this paper, a theory that overcomes the deficiencies of the 3T model in simulating burn of high density D–T is developed. The primary deficiency of the 3T model for this physical system is with the treatment of the Compton scattering energy exchange. The theory here developed culminates in a four temperature model (4T) which describes the radiation field with two temperatures. These are TR, which is the standard radiation temperature of the 3T model (proportional to the fourth root of the radiation energy density), and Tp, which is the true thermodynamic temperature of the photon distribution. This 4T theory gives excellent agreement with the multigroup model for the nonequilibrium burn of D–T. Further, the 4T model transitions smoothly to the 3T model when this is appropriate. Thus the kinetic theory derivation of the 4T model also provides a solid theoretical foundation for the 3T model. Extensions of the theory to inhomogeneous systems are under development to allow treatment of geometries where the computational efficiency of the 4T approach can convey a sizable advantage. There appear to be at least two important applications where the model can be applied. One is for inertial confinement fusion capsules that are optically thick and utilize volume ignition. The second application involves astrophysical accretion disks in the high temperature regime that also exhibit matter heating radiation, albeit without a fusion energy source. A reduced complexity radiation model with the associated reduced computer resource requirements has the potential to facilitate high resolution two dimensional and three dimensional simulations of these astrophysical objects.

Experience with a New Energy Source for Tissue Fusion in Pediatric Patients

Experience with a New Energy Source for Tissue Fusion in Pediatric Patients