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Fast ignition, a pivotal concept in inertial confinement fusion, presents a departure from conventional methods by implementing a two-stage process for fuel compression and ignition. This novel approach minimizes driver requirements and enhances energy efficiency. Among the primary solutions for initiating fast ignition, the utilization of light ion beams, specifically protons, generated through the interaction of high-power lasers with convertor foils, emerges as a prominent strategy. Investigation into the transport of alpha particles produced by the deuterium-tritium fusion reaction plays a vital role in the formation of a hot spot within the fast ignition framework. The self-heating effect caused by the energy deposition of alpha particles triggers ignition in the fusion fuel. Thus, this study focuses on exploring the impact of modern stopping power models, specifically BPS and MD, on the ignition criteria and hot spot formation of pre-compressed DT fuel using a two-temperature model in a non-equilibrium state. These new models are compared and contrasted with previous ones. For this investigation, a DT equimolar fuel with a density of 300 g cm–3 and an incident proton beam featuring an average energy of 4 MeV and a Maxwellian energy distribution are employed. Our calculations demonstrate that the newer BPS and MD stopping power models slightly shift the ignition criterion towards higher ρR values. Furthermore, the thermal efficiency reduction of alpha particles in these stopping power models leads to a significant decrease in hot spot temperature when compared to older models. [ABSTRACT FROM AUTHOR]

Focused Energy is a new startup company with the goal of developing laser-driven inertial fusion energy for electrical power production. The company combines the results from decades of fundamental research in inertial confinement fusion at universities and national laboratories with the flexibility and the speed of a startup company. Focused Energy has chosen the direct-drive, proton fast ignition approach to reach ignition, burn and high gain as the most promising approach. Located in Austin/US and Darmstadt/Germany, supported by the science community and private investment Focused Energy is paving the way to inertial fusion energy combining the best skill set and state-of-the-art technology from both sides of the Atlantic Ocean. In this paper we discuss the details and reasoning for the approach and the technical directions we have chosen. We will outline our roadmap for getting to a fusion pilot plant in the mid to late 2030s. [ABSTRACT FROM AUTHOR]

We present findings from an experimental tuning campaign aimed at igniting larger DT cryogenic layered implosions using a dual frustum shaped hohlraum, denoted "frustraum". The frustraum's distinctive shape reduces hohlraum wall losses while concurrently enhancing minimum capsule clearance with the hohlraum wall and sensitivity to pointing changes. Compared to current cylindrical hohlraum (6.4 × 11.24 mm), the frustraum has a wall area approximately 20 % smaller, resulting in a measured improvement in efficiency of around 12 %. Consequently, 12 % less laser energy is required to implode a capsule within the same acceleration timeframe. Conversely, directing the same laser energy into the frustraum yields higher ion temperatures within symmetry capsules, along with increased radiation temperatures and reduced implosion acceleration times compared to current cylindrical hohlraums. [ABSTRACT FROM AUTHOR]

Laser-driven "inverted corona" fusion targets have attracted interest as a low-convergence neutron source and platform for studying kinetic physics. The scheme consists of a hollow or gas-filled spherical shell made of deuterated plastic. The shell has one or more laser entrance holes (LEH), resembling a spherical hohlraum. The laser passes through the LEH's and illuminates the interior surface of the shell, ablating a plasma that travels inward towards the target center. Long ion mean free paths in the converging plasma can lead to significant interpenetration, atomic mix, and other kinetic effects. In this work we report on numerical simulations of inverted corona targets using the kinetic-ion, fluid–electron hybrid particle-in-cell (PIC) approach in 2D RZ geometry. 2D simulations suggest that shape effects do not have a significant impact on plasma evolution and observed yield trends are primarily the result of 1D kinetic mix mechanisms. Simulations are also compared against available experimental data recorded at the OMEGA laser facility. In particular, synthetic x-ray emission images show good qualitative agreement with experimental results, albeit with an apparent timing discrepancy for the two-sided vacuum target. More generally, we demonstrate the potential of hybrid-PIC simulations for full-system modeling and experimental design, including collisional absorption of laser energy, plasma evolution, mix, and fusion burn. [ABSTRACT FROM AUTHOR]

Fusion ignition by inertial confinement requires compression and heating of the fusion fuel to temperatures in excess of 5 keV and densities exceeding hundreds of g/cc. In August 2021, this scientific milestone was surpassed at the National Ignition Facility (NIF), when the Lawson criterion for ignition was exceeded generating 1.37MJ of fusion energy (Abu-Shawareb et al 2022 Phys. Rev. Lett. 129 075001), and then in December 2022 target gain >1 was realized with the production of 3.1MJ of fusion energy from a target driven by 2.0MJ of laser energy (Abu-Shawareb et al 2024 Phys. Rev. Lett. 132 065102). At the NIF, inertial confinement fusion research primarily uses a laser indirect drive in which the fusion capsule is surrounded by a high-Z enclosure (‘hohlraum’) used to convert the directed laser energy into a symmetric x-ray drive on the capsule. Precise measurements of the plasma conditions, x-rays, γ -rays and neutrons produced are key to understanding the pathway to higher performance. This paper discusses the diagnostics and measurement techniques developed to understand these experiments, focusing on three main topics: (1) key diagnostic developments for achieving igniting plasmas, (2) novel signatures related to thermonuclear burn and (3) advances to diagnostic capabilities in the igniting regime with a perspective toward developments for intertial fusion energy.

This paper provides neutronics analyses of the Xcimer Energy Corporation (XEC) HYLIFE-III Inertial Fusion Energy Power Plant concept. This design is based on the thick-liquid-wall HYLIFE-II reactor, but with much larger fusion yield, due to enhanced driver energy. Although HYLIFE-II neutronics was extensively studied, the differences between the two concepts suggested new analyses are required. Further, computational advances in neutronics calculations also motivate updating results from more than 25 years ago. The neutron spectra emitted from the much larger yield hybrid Inertial Confinement Energy (IFE) target is presented. Selected breeding materials are compared by tritium breeding ratio (TBR), activation, and first wall protection where FLiBe is proposed as the overall best choice. The first wall neutron activation and structural damage, including gas generation in the wall, is presented for various FLiBe protective wet-wall thicknesses. Final optic neutron damage is also examined and results in optics long enough lifespan with moderate annealing temperatures. Some limited comparisons of first wall damage for ICF and Magnetic Confinement Fusion relevant conditions is presented. HYLIFE-III with FLiBe as the breeding material and first wall protection provides a very robust TBR above 1.2. [ABSTRACT FROM AUTHOR]

Fusion energy research is delivering impressive new results emerging from different infrastructures and industrial devices evolving rapidly from ideas to proof-of-principle demonstration and aiming at the conceptual design of reactors for the production of electricity. A major milestone has recently been announced in laser fusion by the Lawrence Livermore National Laboratory and is giving new thrust to laser-fusion energy research worldwide. Here we discuss how these circumstances strongly suggest the need for a European intermediate-energy facility dedicated to the physics and technology of laser-fusion ignition, the physics of fusion materials and advanced technologies for high-repetition-rate, high-average-power broadband lasers. We believe that the participation of the broader scientific community and the increased engagement of industry, in partnership with research and academic institutions, make most timely the construction of this infrastructure of extreme scientific attractiveness.

Fusion energy research is delivering impressive new results emerging from different infrastructures and industrial devices evolving rapidly from ideas to proof-of-principle demonstration and aiming at the conceptual design of reactors for the production of electricity. A major milestone has recently been announced in laser fusion by the Lawrence Livermore National Laboratory and is giving new thrust to laser-fusion energy research worldwide. Here we discuss how these circumstances strongly suggest the need for a European intermediate-energy facility dedicated to the physics and technology of laser-fusion ignition, the physics of fusion materials and advanced technologies for high-repetition-rate, high-average-power broadband lasers. We believe that the participation of the broader scientific community and the increased engagement of industry, in partnership with research and academic institutions, make most timely the construction of this infrastructure of extreme scientific attractiveness. [ABSTRACT FROM AUTHOR]

A simple model for the levelized cost of electricity (LCOE) of an inertial fusion power plant is developed. The model has 14 parameters. These have been designed to be technology agnostic, such that the model may be applied broadly to all variants of inertial fusion. It is also designed to allow easy use of proxies from existing technology. The variables related most intimately to the physics challenges of inertial fusion, such as gain and target cost, are treated as parameters such that requirements can be found without bringing complex physics into the model. A Monte Carlo approach is taken to explore the parameter space. The most important conclusion is that a combination of high gain (greater than 500) and high fusion energy yield per shot (greater than 5 GJ) together appear to unlock more cost competitive designs than those in the existing literature. Designs with LCOE as low as $25/MWh are found with optimistic but not obviously unrealistic inputs. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 1)'. [ABSTRACT FROM AUTHOR]

Our research was mainly concentrated on the physics of semiconductor diodes and especially on measuring the reverse recovery times and currents. In addition, we explored the effect of the reverse bias pulses on a diode still under reverse recovery times. Therefore, we tested the diode cartridges only up to 40% of the scale of that of LANL. We utilized our Component Test Stand (CTS-I) facility modified to power two diode cartridges connected in parallel to a common load (CTS-II). We varied the charge voltage and interpulse separations between the two diode cartridges. In this article, we will describe the modifications of CTS leading to CTS-II and present and analyze the obtained results. [ABSTRACT FROM AUTHOR]

This paper investigates an analytical illustration of ignition conditions for the aneutronic reaction of proton-boron plasma in the presence of the magnetic field for fusion. In particular, the criterion for this plasma target is derived through two-temperature Lindl–Widner diagrams. Since the heating and cooling terms in the energy balance equation are affected by inequality between ions and electrons temperature combined with the impact of the magnetic field, the reduction of energy loss as well as the areal density parameter will increase the fusion rate. It will also relax the requirements of ignition conditions. Therefore, numerical derivations of ignition conditions at stagnation are performed involving the energy balance equation. The additional parameter applied other than electron and ion temperature as well as areal density is the magnetic field dependent B/ρ. It is shown that as B/ρ develops the required areal density decreases. For ions temperature of Ti < 1000 keV and electrons temperature of Te < 110 keV, the equation has real solutions for the areal density of ρR < 6 g/cm2. Furthermore, it is shown that the B/ρ parameter can be set at approximately 106 G cm3/g value. It shows the magnetic field has more effect than DT case and can reduce the driver requirements significantly. A comparison of this model with DT magnetized case shows that this model of p11B fuel is intermediate between experimental results of p11B non-magnetized and DT magnetized in the two-temperature model. [ABSTRACT FROM AUTHOR]

The supply of the required energy to achieve the fuel ignition is one of great concern in a fusion reactor. High amount of energy is needed for the ignition of 3He-3He fuel in a fusion reactor which is due to the losses of radiation and the requirement for high-temperature electrons and ions. The fast ignition (FI) approach causes a decrease in the laser power required to reach a large energy gain in an inertial confinement fusion (ICF) reactor. Ions have the benefit of having classical interaction through Coulomb dispersion with the background plasma. In this method, it is suggested to use deuteron beam for decreasing the ignition energy of the 3He-3He fuel. The deuteron particles would fuse with ions into fuel (helium-3) and produce additional energy. This excess energy has a considerable role in increasing energy gain in an 3He-3He fusion reactor. In this paper, the value of the energy efficiency coefficient (Y-value) and the total deposited energy are computed at different deuteron beam energy and electron temperature. The results show that Y-value is independent of helium-3 numerical density in the 3He-3He plasma and increases slowly with an increase in ion temperature. This fact is substantial at little deuteron energy and high electron temperature. • It is suggested deuteron beam for decreasing the ignition energy. • Depending on the conditions, the extra gain can attribute an important contribution. • The energy efficiency is independent of and increases slowly with increasing. T i. • The energy benefit of this scheme could be significant at less E D and further T e. • The energy dispersion and charge exchange must be considered for exact calculations. [ABSTRACT FROM AUTHOR]

The effects of different nuclear reactions on thermonuclear burn-up conditions of equimolar mixture of deuterium–tritium are investigated. The minimum requirements are determined by three parameters: fuel initial density, initial temperature and hot spot size. The four-temperature theory is used to calculate the critical burn-up parameter or the product of the initial density and the minimum hot spot radius. It was shown that by considering the effect of all nuclear reactions, attaining the minimum conditions required for beginning of nuclear ignitions is faster than those cases in which the effect of reactions is considered individually. [ABSTRACT FROM AUTHOR]

Calculations of accurate opacities in X and XUV range are of high interest for several domains such as astrophysics or inertial fusion science. Such quantities may be investigated through laser‐plasma interaction in the indirect‐drive scheme. In this work absorption properties of such plasmas are analysed using the Flexible Atomic Code. Detailed and unresolved‐transition‐array modes are investigated, and some results obtained with the mixed mode recently developed are also proposed. For a carbon plasma the present approach agrees with the results obtained with the superconfiguration code SCO. Some results are provided about the X‐ray opacity of nickel, and a comparison with data from a recent campaign on LULI 2000 facility is done. This comparison demonstrates that the Unresolved Transition Array approach may be insufficient, e.g., to determinate the accurate position and shape of the 2p–3d structure in nickel at about 25 eV. The case of non‐electric‐dipole‐type transitions, such as magnetic dipole transitions is addressed. The electric‐dipole and magnetic‐dipole transitions are studied here in the case of the 3 * n complex of five tungsten ions, with charge states similar to those found in the tokamak divertors. It is demonstrated that the unresolved transition array formulas provide a fairly accurate description of the most important absorption structures, but fail to reproduce correctly the behavior of the opacity in the wings of these main structures. [ABSTRACT FROM AUTHOR]

This paper provides a summary of recent research connected with the shock ignition (SI) concept of the inertial confinement fusion which was carried out at PALS. In the experiments, Cu planar targets coated with a thin CH layer were used. Two-beam irradiation experiment was applied to investigate the effect of preliminary produced plasma to shock-wave generation. The 1ω or 3ω main beam with a high intensity >1015 W/cm2 generates shock wave, while the other 1ω beam with the intensity below 1014 W/cm2 creates CH pre-plasma simulating the pre-compressed plasma related to SI. Influence of laser wavelength on absorbed energy transfer to shock wave was studied by means of femtosecond interferometry and measuring the crater volume. To characterize the hot electron and ion emission, two-dimensional (2D) Kα-imaging of Cu plasma and grid collector measurements were used. In single 1ω beam experiments energy transport by fast electrons produced by resonant absorption made a significant contribution to shock-wave pressure. However, two-beam experiments with 1ω main beam show that the pre-plasma is strongly degrading the scalelength which leads to decreasing the fast electron energy contribution to shock pressure. In both the single 3ω beam experiments and the two-beam experiments with the 3ω main beam, do not show any clear influence of fast electron transport on shock-wave pressure. The non-monotonic behavior of the scalelength at changing the laser beam focal radius in both presence and absence of pre-plasma reflects the competition of plasma motion and electron heat conduction under the conditions of one-dimensional and 2D plasma expansion at large and small focal radii, respectively. [ABSTRACT FROM AUTHOR]

In fast ignition research, a divergence of laser-generated hot electrons is a serious problem. Using diamond like carbon (DLC) cones is one of the realistic solutions to this problem. However, it is difficult to make a stand-alone DLC cone because it needs a thick DLC layer. In this paper, we report survey findings of preparation conditions for a thick DLC layer. DLC layers were prepared by using plasma–based ion implantation and deposition system. Acetylene gas or toluene vapor was used as a source. After trials of many deposition conditions, it is found that low gas pressure and low RF power condition is suitable for a thick DLC deposition. Properties of the made DLC layers were measured by near edge X-ray absorption fine structures (NEXAFS) and elastic recoil detection analysis (ERDA). It is found that these DLC layers have typical hydrogenated amorphous DLC properties. Based on these results, we succeeded in making stand-alone DLC cones. [ABSTRACT FROM AUTHOR]

Fast ignition is a new scheme for inertial confinement fusion (ICF). In this scheme, at first the interaction of ultraintense laser beam with the hohlraum wall surrounding a capsule containing deuterium-tritium (D-T) fuel causes implosion and compression of fuel to high density and then laser produced protons penetrate in the compressed fuel and deposit their energy in it as the ignition hot spot is created. In this paper, following the energy gain of spherical target and considering relationship of the burn fraction to burn duration, we have obtained the energy gain of conical targets characterized by the angle β, and found a hemispherical capsule (β=π/2) has a gain as high as 96% of that of the whole spherical capsule. The results obtained in this study are qualitatively consistent with Atzeni et al.'s studies of simulations.

Two relatively simple analytic Models for investigation of fast ignition dynamics are developed, that are the subsonic and the supersonic models. On the basis of the subsonic model, which a pre-compressed fuel of density is heated by a subsonic thermal wave, the beam energy and the intensity required for ignition is closely related to proton range. Whereas, on the basis of supersonic model, for ranges shorter than 0.25 gr/cm2 , the mentioned energy remains constant and the intensity decreases. For ranges larger than this value, not only energy but also the beam intensity will increase with the proton range. Considering that proton pulse duration depend on proton range implicitly, these results allow for the determination of an optimum proton pulse duration value, that we have obtained this value equal to 2.14×103 po-1 ps.

This paper reports the discovery of a universal Z 2 -dependency of the binding energy of the homonucleus K-shell MIMS (K-MIMS: Metastable Innershell Molecular State bound by K-shell electrons), which has been established by analyzing extensive existing experimental data over several decades. An intuitive analytical theory on the K-MIMS has been developed for the homologous molecules to the He 2 ⁎ excimer, which elucidates the universal Z -dependent behavior of the K-MIMS. The theory predicts a 1 / Z -dependency of the K-MIMS bond length, which is in agreement with the quasimolecule sizes estimated from the x -ray generation cross-sections in H-like Bi 82+ and U 91+ impact on Au solids. [ABSTRACT FROM AUTHOR]

Over the years the author has written, coordinated, or contributed to numerous reviews of fusion energy. In revisiting them, he is encouraged by the tremendous progress that has been made across the board. Nevertheless, while he believes that a viable fusion reactor could be made in both magnetic and inertial fusion energy, he doesn't think the best approach has yet been identified in either area. Also there remain a number of critical, hardly-explored areas. The author identifies three key issues. Finally, he comments briefly on all the major confinement approaches. [ABSTRACT FROM AUTHOR]

Fusion, in all its varieties, is a very current subject of science and technology. The results of strongly exothermic reaction of thermonuclear fusion between nuclei of deuterium and tritium are: helium nuclei and neutrons, plus considerable kinetic energy of neutrons of over 14 MeV. DT nuclides synthesis reaction is probably not the most favorable one for energy production, but is the most advanced technologically. More efficient would be possibly an aneutronic fusion. The EU by its EURATOM agenda prepared a Road Map for research and implementation of Fusion as a commercial method of thermonuclear energy generation in the time horizon of 2050.The milestones on this road are tokomak experiments JET, ITER and DEMO, and neutron experiment IFMIF. There is a hope, that by engagement of the national government, and all research and technical fusion and plasma communities, part of this Road Map may be realized in Poland. The infrastructure build for fusion experiments may be also used for material engineering research, chemistry, biomedical, associated with environment protection, power engineering, security, etc. Construction of such research and industrial accelerator and tokomak infrastructure may have potentially a profound meaning for the development of science and technology in Poland. [ABSTRACT FROM AUTHOR]

Abstract: Induction accelerators are appealing for heavy-ion driven inertial fusion energy (HIF) because of their high efficiency and their demonstrated capability to accelerate high beam current (≥10kA in some applications). For the HIF application, accomplishments and challenges are summarized. HIF research and development has demonstrated the production of single ion beams with the required emittance, current, and energy suitable for injection into an induction linear accelerator. Driver scale beams have been transported in quadrupole channels of the order of 10% of the number of quadrupoles of a driver. We review the design and operation of induction accelerators and the relevant aspects of their use as drivers for HIF. We describe intermediate research steps that would provide the basis for a heavy-ion research facility capable of heating matter to fusion relevant temperatures and densities, and also to test and demonstrate an accelerator architecture that scales well to a fusion power plant. [Copyright &y& Elsevier]

Abstract: The University of Maryland Electron Ring (UMER) is a unique machine that uses scaled electron beams at nonrelativistic energies (10keV) to inexpensively model GeV beams of heavy ions over long path lengths (kilometers of transport distance). The UMER beam parameters correspond to space charge tune depressions, at injection, adjustable in the range of 0.14–0.85. Although a ring, many of the intense beam studies on UMER are applicable to linacs. This paper reviews the UMER program, which contains experimental, computational, and theoretical components. We outline the research areas of interest, recent accomplishments, and future plans, emphasizing the relevance to heavy ion drivers. Specific topics include longitudinal induction focusing and beam manipulations; generation and propagation of space charge waves, including large-amplitude solitons; bunch end interpenetration and observation of a multi-stream instability; beam halo studies; and diagnostic development. [Copyright &y& Elsevier]

Abstract: Inertial fusion ignition phenomena including effects of non-Maxwellian ion velocity distributions are studied by molecular dynamics particle simulation. 10,000 DT ions at a density 100g/cm3 and temperature ∼10keV are followed for 10 to 20ps. The simulations include ion collisions, electron–ion coupling and radiation emission and absorption. Fusion reactions produce energetic alphas and the plasma self-heats to 20–30keV. It is found that calculations starting from a variety of initial conditions evolve to approach a unique self-heating trajectory which can be called an ignition attractor. A calculation starting with 3keV DT ignites within a few ps after 2MeV alpha particles are injected and deposit ∼300MJ/g; this demonstrates that fast ions are highly effective for fast ignition of precompressed DT. [Copyright &y& Elsevier]

An initial study and design on ignition elliptical hohlraum (ellipraum) is given by using the expended plasma-filling model with criterions. As a result, in an ellipraum with a smaller ratio of major-to-minor axis (a/b), the radius ratio of ellipraum-to-capsule (b/RC) should be larger (hence more sphere-like) to meet the criterions of plasma-filling and laser deposition, meanwhile the required laser energy and peak power are lower and the coupling between different modes is weaker. To produce a 300 eV radiation pulse to ignite a capsule of 1 mm radius, an ellipraum of a/b = 1.6 and b/Rc = 2.8 is superior to a cylinraum with a length-to-diameter ratio of 1.81 and a cylinraum-to-capsule radius ratio of 2.54 in saving more than 10% laser energy and reducing 50% coupling between different modes. [ABSTRACT FROM PUBLISHER]

Abstract: The fast ignition realization experiment (FIREX) project is progressing. The new short pulse laser system, LFEX laser, has been completely assembled and one of the four beamlets is now in operation. A fast-ignition experiment was performed using this single short pulse combined with the Gekko XII implosion laser. The energy of the GXII implosion laser was about 2kJ and the pulse width was 1.5ns. The energy of the LFEX laser was increased upto 800J and two pulse durations 5 and 1.6ps were compared. Targets were deuterated plastic shells with gold cones. It was found that the neutron yield was increased by a factor of 30 as a result of the fast electron-induced heating in LFEX 1.6ps shot. The estimated coupling efficiency between the LFEX laser pulse and the compressed fuel was low (less than 5%). This may be due to pre-plasma formed by light arriving at the target before the main laser pulse. Further investigations and attempts to overcome these problems are now in progress. [Copyright &y& Elsevier]

We investigate the efficiency of inertial fusion target compression, where at the initial time moment the thermonuclear fuel is in a two-phase state and has the form of two adjacent layers - the external DT-liquid layer and the internal DT-ice layer. We study this problem for the fast ignition targets, where the ultimate final density of the thermonuclear matter is of a special importance. We take the simplest type of a fast ignition target, which corresponds to the technical justification of the HiPER Project aimed at demonstrating fast ignition at the compressing laser pulse energy ~100 kJ. Such a target presents a spherical DT-ice shell coated with a thin polymer film. We obtain the dependence of the final target density on the mass fraction of the DT-matter liquid phase and formulate the requirements on the admissible concentration of liquid phase if the decrease in the DT-fuel final density does not exceed 10%. We find the criterion for choosing the laser-pulse duration which provides the minimum decrease in the final density of the target containing DT-matter in the initial two-phase state. [ABSTRACT FROM AUTHOR]

Fuel supply is a fundamental issue in application of inertial nuclear fusion. To address this issue, we propose the use of an HTS superconductor capsule containing nuclear fuel, which can levitate in a magnetic field. During magnetic levitation, positional stability is important because it affects levitation accuracy to the focal point of giant lasers. We have developed a numerical simulation program based on a 3-D hybrid finite element and boundary element method to evaluate positional stability during magnetic levitation. Moreover, we have optimally designed and constructed a multi-coil system wherein spherical HTS bulk of 5 mm diameter can levitate stably. Finally, we have conducted the experiments for the evaluation of magnetic levitation, and compared the results with our simulation. [ABSTRACT FROM AUTHOR]

In this paper, the plasma-filling model was extrapolated to the case of a hohlraum driven by a shaped laser pulse, and this extended model was used to obtain an initial design of the hohlraum size. A density criterion of ne = 0.1 was used for designing hohlraums which have low plasma filling with maximum achievable radiation. The method was successfully used to design a half hohlraum size with a three-step laser pulse on SGIII prototype and a U hohlraum size with shaped laser pulse for ignition. It was shown that the extended model with the criterion can provide reasonable initial design of a hohlraum size for optimal designing with a two-dimensional code. [ABSTRACT FROM AUTHOR]

The results of experimental and numerical studies of high-intensity proton beam generation driven by a short laser pulse of relativistic intensity are reported. In the experiment, a 350 fs laser pulse of 1.06 or 0.53 μm wavelength and intensity up to 2×1019 Wcm-2 irradiated a thin (0.6-2 μm) plastic (PS) or Au/PS (plastic covered by 0.2 μm Au front layer) target along the target normal. The effect of laser intensity, the target structure and the laser wavelength on the proton beam parameters and laser-protons energy conversion efficiency were examined. Both the measurements and one-dimensional particle-in-cell simulations showed that MeV proton beams of intensity ∼1018 Wcm-2 and current density ∼1012 Acm-2 at the source can be produced when the laser intensity-wavelength squared product ILλ2 is ∼1019 Wcm-2 μm2 and the laser-target interaction conditions approach the skin-layer ponderomotive acceleration (SLPA) requirements. The simulations also proved that at ILλ2≥slant 5×1019 Wcm-2 μm2 and λ≤slant 0.53 μm, SLPA clearly prevails over other acceleration mechanisms and it can produce multi-MeV proton beams of extremely high intensities above 1020 Wcm-2. [ABSTRACT FROM AUTHOR]

In ignition targets designs, U or U based cocktail hohlraum are usually used because the Rosseland mean opacity of U is higher than for Au at the radiation temperature for ignition. However, it should be noted that the opacity of U is obviously lower than for Au when the radiation temperature falls into a low temperature region. Because the depth penetrated by radiation is only several micrometers under a 300eV drive, and also because there is a prepulse longer than 10 ns prepulse at temperatures lower than 170 eV in the radiation drive of ignition target designs. Therefore we propose an Au + U + Au sandwich hohlraum for ignition targets in this work. Compared to the cocktail, the sandwich not only remarkably simplifies the fabrication and uses less depleted U material, but also increases the albedo during the prepulse. [ABSTRACT FROM AUTHOR]

In contrast to the usual laser fusion scheme with spherical irradiation and very high compression and ignition of fuel, the alternative scheme with side-on ignition of uncompressed solid density of fuel (Chu) may lead to a solution by using the now available picosecond laser pulses with higher than petawatt power. A necessary condition is to use clean laser pulses with better than 108 contrast ratio for suppression of relativistic self-focusing. When updating the analysis of Chu for fusion of deuterium-tritium and proton-11B, one problem is that the correct use of the stopping power of the alpha particles had to be solved. Discrepancies are evaluated in view of the stopping power at the low temperature range of the plasmas where the change of the emitted bremsstrahlung is involved. [ABSTRACT FROM AUTHOR]

Results in some directions of the target technology for research on high energy density and laser fusion at the Russian Federal Nuclear Centre-All-Russia Research Institute of Experimental Physics for the last three years are presented. The results of development of optical and X-ray methods of characterization and manufacturing techniques of targets for studying the equation-of-state at high pressures and the condensed rare gas targets for the influence of pulse-repeated laser irradiation are given. [ABSTRACT FROM AUTHOR]

Hypervelocity (∼1000-km/s) impact of a macroscopic particle (macron) has profound influences in high energy density physics and inertial fusion energy researches. As the charge-mass ratio of macrons is too low, the length of an electrostatic accelerator can reach hundreds to thousands of kilometers, rendering macron acceleration impractical. To reduce the accelerator length, a much higher electric field than what the most powerful klystrons can provide is desired. One practical choice may be the high-intensity charged particle beam "blowing-pipe" approach. In this approach, a high-intensity (∼10-kA) medium-energy (0.5-2-MeV) long-pulse (10-1000-μs) positively charged ion beam shots to a heavily charged millimeter-size macron to create a local high-strength electric field (∼1010 V/rn), accelerating the macron efficiently. We will discuss the physics and challenges involved in this concept and give an illustrative simulation. [ABSTRACT FROM AUTHOR]

Intense ion beams from accelerators are now available to generate high energy density matter and to study astrophysical phenomena in the laboratory under controlled and reproducible conditions. A detailed understanding of interaction phenomena of intense ion- and laser radiation with matter is important for a large number of applications in different fields of science, extending from basic research of plasma properties to application in energy science and the investigation of processes occurring in stellar atmospheres or even in the interior of stars and planets. Energy loss processes of heavy ions in plasma and cold matter are important for the generation of high energy density states in general and especially in the hot dense plasma of an inertial fusion target. Of special interest are phase transitions and the associated time scales when matter passes the warm dense matter regime of the phase diagram at high density but relatively low temperature. We present an overview on recent results and developments of beam plasma, and beam matter interaction processes studied with heavy ion beams and laser beams combined with accelerator and nuclear physics technology. A natural example of hot dense plasma is provided by our neighbouring star the sun, and allows a deep insight into the physics of fusion, the properties of matter at high energy density, and is moreover an excellent laboratory for astroparticle physics. As such the sun’s interior plasma can even be used to probe the existence of novel particles and dark matter candidates with a combination of equipment and methods from accelerator technology and high resolution plasma spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Hypervelocity impact (HVI) is a very important workbench in high energy density (HED) physics studies. In this paper, we will discuss the physics of the impact of a macroscopic particle (macron) at the speed of up to () to an immobile target, and its differences from other HED drives. As HVIs can create ultra high energy density, we believe that with a proper design, they can be very efficient drives to inertial confinement fusion energy (IFE). We will propose a fusion scheme of this concept, investigate the physics involved in detail, and present the preliminary simulation results. These investigations show that the scheme is very promising. [Copyright &y& Elsevier]

Abstract: Uniformity of heavy ion beam (HIB) illumination is one of the key issues in HIB inertial confinement fusion (HIF): deviation from fuel implosion symmetry should be less than a few percent in order to compress a fuel sufficiently and release fusion energy effectively. In this paper, a new mitigation method of the Rayleigh–Taylor (R-T) instability growth is presented in order to make a HIF target robust against a non-uniform implosion. In this study a new mitigation method of R-T instability growth is proposed based on an oscillating perturbed acceleration, which can be realized by a rotating or oscillating HIB illumination onto a fuel pellet. The R-T instability analyses and fluid simulations demonstrate that the oscillating acceleration reduces the R-T instability growth significantly. In this paper a baseline steady acceleration g 0 is perturbed by a perturbed oscillating acceleration δg, which is spatially non-uniform and oscillates in time (g 0⪢δg). An example result shows 84% reduction of the R-T instability growth. [Copyright &y& Elsevier]

Abstract: Recent research activities in Japan relevant to heavy ion fusion (HIF) are presented. During the past two years, significant progress in HIF and high energy density (HED) physics research has been made by a number of research groups in universities and accelerator facilities. Evolutions in phase space during the longitudinal compression of intense beams were investigated at UU–NUT–TIT. Beam–plasma interaction experiments and related theoretical studies are in progress at RLNR-TIT. In the study, shock-heated hydrogen was used for the interaction experiments as a well-defined non-ideal-plasma target. In the beam–plasma interaction experiments, a special emphasis is placed on an evaluation of non-linear effects on the stopping power in a beam-heated plasma target. A direct–indirect hybrid scheme of a beam-driven ICF target has been proposed and discussed at UU. In the same group, a method for controlling the Rayleigh–Taylor instability in imploding fuel target has been proposed using oscillating heavy ion beams (HIBs). Core dynamics of the impact ignition has been investigated both experimentally and numerically at ILE—Osaka. Dense plasmas driven by intense ion beams and/or a pulse powered device, were evaluated by a group of DES-TIT, concerning the researches on HED and warm dense matter (WDM) physics. A quasi-statically tamped target was proposed to make a well-defined, warm dense state for equation-of-state (EOS) studies based on ion accelerators. The potentiality of the new facility planned at KEK was evaluated by a collaborating group of TIT–UU–KEK, which can extend the parameter regime for laboratory experiments to study the properties of matter under extreme conditions. A possible method to make a high-pressure condition for study of the planetary science was discussed as a short-term subject of intense HIBs. [Copyright &y& Elsevier]

We have been developing an active magnetic levitation system, which is composed of a field-cooled disk-shaped or sphere shaped high-temperature superconducting bulks (HTS bulks) and vertically piled ring-shaped electromagnets without an iron core. We suppose that this active magnetic levitation system can be applied to inertial nuclear fusion. In inertial nuclear fusion, one of the most important issues is to achieve high-accuracy position control of the fusion fuel, which consists of deuterium and tritium in order to evenly illuminate the entire surface of the target. Therefore, active magnetic levitation is applied to the levitation and position control of a sphere-shaped superconducting capsule containing nuclear fusion fuel. In this study, we designed and constructed a three-coil position control system in order to achieve the stable levitation of the sphere-shaped HTS bulk with a diameter of 5 mm by using the numerical simulation based on the hybrid finite element and boundary element analysis. Then, we carried out the experiments on the position control and restoring force characteristics of the sphere-shaped HTS bulk in the constructed levitation system. [ABSTRACT FROM AUTHOR]

Interaction of intense ion radiation with matter has numerous applications in different fields of science, ranging from basic research of plasma properties to application in energy science. Energy loss processes of heavy ions in plasma and cold matter are important to understand the generation of high energy density states in matter. The hot dense plasma of an inertial fusion target is just one example. Of special interest are phase transitions, when irradiated matter passes through the parameter regime of warm dense matter, which is located in the phase diagram at high density but relatively low temperature. Typical parameters are in the pressure range of kbar to Mbar and temperatures ranging into the few eV regime. We present an overview on recent results and developments of beam plasma, and beam matter interaction processes studied with heavy ion beams from the GSI accelerator facilities, which consist of an rf-accelerator (UNILAC: Universal Linear Accelerator), a heavy ion synchrotron (SIS 18) and an experimental storage ring (ESR). The synchrotron SIS18 currently delivers an intense uranium beam that deposits about 1 kJ/g specific energy in solid matter. Using this beam, high energy density states close to the critical point of lead, have been reached and solid lead foils have been heated to a measured brightness temperature on the order of 5000 K. [ABSTRACT FROM AUTHOR]

Abstract: We tested an experimental setup for measurement of non-linear stopping of low-energy heavy ions in non-ideal plasmas. In this setup, we used a silicon surface-barrier charged-particle detector (SSBD), which could measure the energy of single ions. For synchronization between the plasma production and the injection of single projectiles, a fast beam kicker was installed in front of the plasma target. In order to test this setup, we used a laser-produced polyethylene plasma target instead of a shock-driven plasma device, which is under R&D process. Results of a preliminary energy loss measurement for low-speed heavy ions in the laser plasma are reported. Performance on the time resolution evaluated by using a carbon-foil target is also presented. [Copyright &y& Elsevier]

Abstract: During the past 15 years, using the volume ignition model, a computational code has been designed and gradually developed with the purpose of simulating the laser or ion projectile driven nuclear fusion. Up to now using this code various calculations have been done in different conditions for evaluating fusion gain and time dependence of temperature of fuels such as DD, DT, H11B and D3He, respectively, and the results have been published in several papers [R. Khoda-Bakhsh, et al., Fusion Technol. 22 (1992) 50; R. Khoda-Bakhsh, Nucl. Instr. and Meth. A 330 (1993) 268; G.H. Miley, et al., Fusion Technol. 19 (1991) 50 ; R. Khoda-Bakhsh, et al., Fusion Technol. 24 (1993) 28; R. Khoda-Bakhsh, AIP Conf. Proc. 369 (Part One) (1996) 289 ]. Here, using this extended code and for the first time, we have simulated the conditions under which pure 3He fuel pellets with different volumes and initial compressions begin to ignite. Fusion gains of more than 50 are obtained with an ignition temperature decreased to only 22.9keV at an initial compression to 500000 times the solid-state density. Also calculations showed that for spin-polarized fuel, there is a driver energy reduction which for maximum gain condition, is less for low initial densities and a gain increase which varies irregularly for different initial conditions. [Copyright &y& Elsevier]

Abstract: The High Average Power Laser (HAPL) Program, directed by the Naval Research Laboratory (NRL) in Washington, DC, is pursuing an all-systems approach to inertial fusion energy (IFE) with lasers. Systems that will be needed for an IFE power plant, such as the laser drivers, cryogenic targets, target factory, target injection, target tracking and engagement, chamber design, and chamber materials to name a few, are all being developed in parallel at various laboratories, universities, and companies across the U.S. While all such systems in an IFE power plant are essential, at the heart of the energy production is the fuel, the cryogenic target. The emphasis at General Atomics is the development of cryogenic targets within physics specifications, the economical mass production of targets, and the delivery of the targets to the center of the chamber within tight tolerances. [Copyright &y& Elsevier]

Abstract: The high-current experiment (HCX) at LBNL is a driver scale single beam injector that provides a 1MeV K+ ion beam current of 0.18A for 5μs. It transports high-current beams with large fill factor (ratio of the maximum beam envelope radius to the beam pipe radius) and low emittance growth that are required to keep the cost of the power plant competitive and to satisfy the target requirements of focusing ion beams to high-power density. Beam interaction with the background gas and walls desorbs electrons that can multiply and accumulate, creating an electron cloud. This ubiquitous effect grows at higher fill factors and degrades the quality of the beam. We review simulations and diagnostics tools used to measure electron production, accumulation and its properties. [Copyright &y& Elsevier]

Abstract: We developed an experimental apparatus for the study of non-linear stopping of low-energy heavy ions in non-ideal plasmas. The target plasma was produced by an electromagnetically driven shock tube. A pair of 50--diameter beam apertures was attached to the shock tube wall. These apertures confined hydrogen gas of in the tube and sustained the pressure difference (–) between the tube and the beam line. In order to measure the energy loss in the plasma in the tube, we used a semiconductor charged-particle detector, which could directly measure the kinetic energy of single particles, since the beam transmission through these apertures was very small. To synchronize the plasma production in the shock tube and the injection of projectiles, a fast beam kicker was installed in front of the plasma target. Results of preliminary experiments using thin carbon foil targets showed that the measured energy loss of single projectiles after passing through the target was in agreement with other data. The time resolution of the energy-loss measurement system was , which is enough to measure the projectile energy loss during the life time of the target plasma. [Copyright &y& Elsevier]