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The objective of this work is to discuss the prospects of the formation of cryogenic shock ignition targets based on the FST-layering method (FST—free-standing target) proposed and developed at the Lebedev Physical Institute (LPI). The targets are designed to study alternative fuel ignition schemes at intermediate and megajoule-scale ICF laser facilities. [ABSTRACT FROM AUTHOR]

The Lebedev Physical Institute (LPI) actively develops innovative technologies for creating the HTSC—MAGLEV accelerator for delivering a cryogenic fuel target (CFT) placed in a levitating HTSC-carrier to the ICF chamber for interacting with laser radiation. The LPI approach is based on the phenomenon of HTSC quantum levitation in a gradient magnetic field. Acceleration is provided by a sequence of current-carrying solenoids, and HTSC-carrier levitation occurs due to the use of a magnetic rail, along which the solenoids are placed. A prototype of an elementary block for accelerating an HTSC-carrier is developed and its motion control processes are studied. For this purpose, a special system of operational control of the acceleration block is developed and tested. The HTSC-carrier acceleration up to 1 m/s at the acceleration length La = 20 cm is demonstrated using only one pair of matched solenoids. The results obtained are of practical importance in the area of creating noncontact systems for CFT delivery due to constructing a linear magnetic track by connecting one elementary acceleration unit with many others to achieve a required CFT injection rates from 20 to 200 m/s and higher. [ABSTRACT FROM AUTHOR]

Magnetic levitation technologies are studied as an innovative basis for developing contactless systems for delivering cryogenic targets to the laser focus of an ICF facility or future power plant. A necessary element of such systems is a special target carrier made of high-temperature superconductors (HTSC) with high vortex pinning. It is shown experimentally that an HTSC carrier in the form of an outer coating of the target makes it possible to completely eliminate mechanical friction during target acceleration due to its levitation in gradient magnetic fields. The prospects for further development of this direction in the area of creating HTSC nanostructured films and coatings are discussed. [ABSTRACT FROM AUTHOR]

Fuel magnetization significantly lowers the required radial convergence, enabling cylindrical implosions to become a promising approach for inertial confinement fusion. The Nernst effect on the two-layer single shell magnetized target design applied to a Z-pinch benefits from a gold layer that decreases fuel demagnetization and serves as a magnetothermal insulation layer, preventing magnetothermal losses. The resistive diffusion and Nernst advection of the magnetic field are considered in the radiation magnetohydrodynamic model, which alter the evolution of magnetic flux in the magnetized target and result in plasma demagnetization. The results demonstrate that targets with a wide range of parameters can achieve ignition conditions under a 30 MA driven current. A two-layer single shell magnetized target for lessening the Nernst effect has the potential to achieve ignition conditions. The fusion yield of the optimal target increases by 168% from 0.71 MJ to 1.90 MJ, compared to a one-layer single shell target.

Hybrid fluid-PIC simulations aimed at a better understanding of the implosion physics and the material mixing into the hot spot are described. The application of a hybrid fluid-PIC code is motivated by the difficulty of modeling the material mixing by the commonly used radiation hydrodynamic simulations. Hybrid fluid-PIC techniques, which treat the ions with the traditional particle-in-cell method, and electrons with a massless fluid, are more adaptable to handle the heating of DT fuel through PdV work and the material mixing near the DT ice-gas interface and ablator-fuel interface of a compressed capsule. During implosion shock convergence, significant reactant temperature separation and a noticeable amount of material mixing are observed, both of which have important consequences for estimating neutron yield and the understanding of implosions. Physical explanations for these phenomena are discussed, with the non-equilibrium effect in the hotspot and hydrodynamic instabilities at the interface as the likely explanation, respectively. The hybrid fluid-PIC method would be helpful to test the phenomenological fluid model describing the material mixing in ICF implosion.

The enhancement of fusion reaction rates in a thermonuclear plasma by electron screening of the Coulomb barrier is an important plasma-nuclear effect that is present in stellar models but has not been experimentally observed. Experiments using inertial confinement fusion (ICF) implosions may provide a unique opportunity to observe this important plasma-nuclear effect. Herein, we show that experiments at the National Ignition Facility (NIF) have reached the relevant physical regime, with respect to the density and temperature conditions, but the estimated impacts of plasma screening on nuclear reaction rates are currently too small and need to be increased to lower the expected measurement uncertainty. Detailed radiation hydrodynamics simulations show that practical target changes, like adding readily available high-Z gases, and significantly slowing the inflight implosion velocity, while maintaining inflight kinetic energy, might be able to push these conditions to those where plasma screening effects may be measurable. We also perform synthetic data exercises to help understand where the anticipated experimental uncertainties will become important. But challenges remain, such as the detectability of the reaction products, non-thermal plasma effects, species separation, and impacts of spatial and temporal gradients. This work lays the foundation for future efforts to develop an important platform capable of the first plasma electron screening observation.

The challenge in the field of inertial confinement fusion (ICF) research is related to the study of alternative schemes for fuel ignition on laser systems of medium and megajoule scales. At the moment, it is considered promising to use the method of shock ignition of fuel in a pre-compressed cryogenic target using a focused shock wave (shock- or self-ignition (SI) mode). To confirm the applicability of this scheme to ICF, it is necessary to develop technologies for mass-fabrication of the corresponding targets with a spherically symmetric cryogenic layer (hereinafter referred to as SI-targets). These targets have a low initial aspect ratio Acl (Acl = 3 and Acl = 5) because they are expected to be more hydrodynamically stable during implosion. The paper discusses the preparation of SI-targets for laser experiments using the free-standing target (FST) layering method developed at the Lebedev Physical Institute (LPI). It is shown that, based on FST, it is possible to build a prototype layering module for in-line production of free-standing SI-targets, and the layering time, τform, does not exceed 30 s both for deuterium and deuterium-tritium fuel. Very short values of τform make it possible to obtain layers with a stable isotropic fuel structure to meet the requirements of implosion physics. [ABSTRACT FROM AUTHOR]

Inertial confinement fusion (ICF) experiments create a unique laboratory environment in which thermonuclear fusion reactions occur within a plasma, with conditions comparable to stellar cores and the early universe. In contrast, accelerator-based measurements must compete with bound electron screening effects and beam stopping when measuring fusion cross sections at nucleosynthesis-relevant energies. Therefore, ICF experiments are a natural place to study nuclear reactions relevant to nuclear astrophysics. However, analysis of ICF-based measurements must address its own set of complicating factors. These include: the inherent range of reaction energies, spatial and temporal thermal temperature variation, and kinetic effects such as species separation. In this work we examine these phenomena and develop an analysis to quantify and, when possible, compensate for their effects on our inference. Error propagation in the analyses are studied using synthetic data combined with Markov Chain Monte Carlo (MCMC) machine learning. The novel inference techniques will aid in the extraction of valuable and accurate data from ICF-based nuclear astrophysics experiments.

• A novel design with a grooved aluminum-alloy jacket is proposed to improve the thermal uniformity in a compact fusion target. • The thermal-structural performance at the adhesive interface has been found with significant impact on achieving target thermal uniformity. • Silver-doped adhesive at the arm-jacket interface can improve the robust of circumferential uniformity, as well as a high conductive diagnosis band. • The spherical symmetry of the deuterium-tritium ice layer has been significantly improved under the new design. The roughness of the fuel ice layer at low modes significantly impacts the hydrodynamic instability in inertial confinement fusion experiments with indirect-drive cryogenic targets. It is primarily determined by the thermal uniformity of the capsule. Due to the β-decay heat of tritium, the temperature profiles of targets filled with deuterium-tritium differ from those filled with deuterium-deuterium in a cylindrical hohlraum. The cylindrical shape causes the equator of the capsule to be cooler than the two poles in the steady state without any intervention. Tuning the vertical temperature distribution is essential and requires a high thermal resistance in the target thermal mechanical package. It is very difficult for a compact target which is just half of the National Ignition Facility (NIF) target scale, and is contrary to the previous design of deuterium- deuterium target, which used a high-conductive jacket made from Oxygen-Free Copper (OFC), to provide a relatively uniform thermal field around the capsule. To realize the vertical tuning capability and achieving global thermal uniformity of the capsule, we propose in this paper a novel design featuring a grooved aluminum-alloy jacket, as well as the methods to improve thermal contact reliability and conductivity, including decreasing the width of arm-jacket interface, enhancing the adhesive conductivity by doping silver, and replacing the aluminum diagnosis band with conductive OFC. We further verified this design through experiments. It has reduced the global temperature difference of the capsule by about 70 % and significantly improved the quality of the deuterium-tritium ice layer. [ABSTRACT FROM AUTHOR]

The challenge in the field of inertial confinement fusion (ICF) research is related to the study of alternative schemes for fuel ignition on laser systems of medium and megajoule scales. At the moment, it is considered promising to use the method of shock ignition of fuel in a pre-compressed cryogenic target using a focused shock wave (shock- or self-ignition (SI) mode). To confirm the applicability of this scheme to ICF, it is necessary to develop technologies for mass-fabrication of the corresponding targets with a spherically symmetric cryogenic layer (hereinafter referred to as SI-targets). These targets have a low initial aspect ratio Acl (Acl = 3 and Acl = 5) because they are expected to be more hydrodynamically stable during implosion. The paper discusses the preparation of SI-targets for laser experiments using the free-standing target (FST) layering method developed at the Lebedev Physical Institute (LPI). It is shown that, based on FST, it is possible to build a prototype layering module for in-line production of free-standing SI-targets, and the layering time, τform, does not exceed 30 s both for deuterium and deuterium-tritium fuel. Very short values of τform make it possible to obtain layers with a stable isotropic fuel structure to meet the requirements of implosion physics.

A deuterated-tritiated polymer was prepared via addition reaction and isotopic exchange between a deuterated polycyclooctene and tritium in the presence of a Pd/BaSO 4 catalyst, free of solvents. After reaction, the gas sample from the vessel was analyzed with mass spectrometer, and compared with the raw T 2 /Ar mixture. It was demonstrated that isotopic exchange as well as hydrogen addition reaction occurred in the tritiation experiment. The abundance of tritium in the deuterated-tritiated polymer was determined to be 17.7%. The deuterated-tritiated polymer dissolved in CDCl 3 was characterized by 2H NMR and 3H NMR spectra. By using the solvent-free tritiation method, the generation of waste radioactive liquids can be avoided, and the deuterated-tritiated polymer can be kept away from the protiums of solvents. [ABSTRACT FROM AUTHOR]