E. R. Koresheva

Free standing target technologies for inertial fusion energy: Target fabrication, characterization, and delivery

Abstract Inertialfusionenergy~IFE!researchindicatesthattheenergygenerationbymeansofcryogenicfueltargetcompressionrequiresthattargetsmustbeinjectedtothetargetchambercenteratarateofabout6Hz.Thisrequirementcanbefulfilledonlyifthetargetsarefree-standing.ThemostinterestingresultsconcerningtheactivityoftheLebedevPhysicalInstitutein the area of free-standing targets~FST! fabrication, characterization and delivery are presented. Keywords: Inertial Fusion; Targets 1. INTRODUCTION Inertial fusion energy is widely regarded as the energysource of the future ~Hora, 2004!, and intense laser andparticle beams are discussed as potential drivers. The fastignition concept is currently at the focus of the researcheffort ~Mulser & Bauer 2004; Deutsch, 2003; Koshkarev,2002!.The current status is still dominated by intense basicresearch of inter action phenomena of intense laser andparticle beams with ionized matter~Deutsch, 2004; Malka,2002; Hoffmann et al ., 1990!. The availability of suitabletargets was identified as a key issue for inertial fusion basicresearch with lasers and heavy ion beams ~Callahan

Free-standing targets for applications to ICF

In conventional inertial confinement fusion (ICF), a high power laser system is used to compress a cryogenic target and create energy. One of the challenges for ICF cryogenics is producing the homogeneous and uniform fuel on the inside surface of a spherical polymer shell. In this report, we will discuss a conceptual approach based on freestanding targets and the results of our recent and current developments.

Ultrafine Fuel Layers for Application to ICF/IFE Targets

Abstract We report on credible solutions for fabrication of isotropic ultrafine fuel layers within ICF/IFE targets. The layers have enhanced mechanical strength and thermal stability that is of critical importance for target fabrication, acceleration, and injection. The effects of the extent of microstructure irregularity and bulk fuel properties are demonstrated. Emphasis is given to isotropic properties of the ultrafine layers for avoiding instabilities caused by grain-affected shock velocity variations. The considered fuel layers have the potential to advance materials for application to fusion target fabrication in the form that meets the requirements of implosion physics.

Progress in the Development of Tomographic Information-Processing Methods for Application to ICF Target Characterization

Abstract A precise and accurate knowledge of the characteristics of three-dimensional micro-objects such as inertial confinement fusion (ICF) targets and laser-produced plasmas is required to analyze the results of laser fusion experiments. Significant advances have been made in the development of tomographic information-processing methods for application to ICF target characterization. Topics discussed include (a) new high-resolution algorithm obtained by symmetrizing a basic filtered backprojection algorithm, (b) algorithms for threshold target characterization, (c) new approach to micro-object scanning based on quasi-uniform geometry, (d) ICF target preparation for tomographic characterization.

On the possibility of developing the non-contact delivery system for cryogenic thermonuclear target transport to the IFE reactor

It is proposed to use the HTSC quantum levitation phenomenon in magnetic fields of various configurations to develop the systems of contact-free positioning and transport of cryogenic fuel targets (CFTs) to the focus of a high-power laser installation or the IFE reactor. The results are presented of a large cycle of experimental studies using YBa2Cu3O7−x superconducting ceramics and permanent magnet guideways based on various combinations of permanentmagnets to develop “CFT-MAGLEV” delivery systems.

Cryogenic hydrogen fuel for controlled inertial confinement fusion (formation of reactor-scale cryogenic targets)

In inertial fusion energy research, considerable attention has recently been focused on low-cost fabrication of a large number of targets by developing a specialized layering module of repeatable operation. The targets must be free-standing, or unmounted. Therefore, the development of a target factory for inertial confinement fusion (ICF) is based on methods that can ensure a cost-effective target production with high repeatability. Minimization of the amount of tritium (i.e., minimization of time and space at all production stages) is a necessary condition as well. Additionally, the cryogenic hydrogen fuel inside the targets must have a structure (ultrafine layers—the grain size should be scaled back to the nanometer range) that supports the fuel layer survivability under target injection and transport through the reactor chamber. To meet the above requirements, significant progress has been made at the Lebedev Physical Institute (LPI) in the technology developed on the basis of rapid fuel layering inside moving free-standing targets (FST), also referred to as the FST layering method. Owing to the research carried out at LPI, unique experience has been gained in the development of the FST-layering module for target fabrication with an ultrafine fuel layer, including a reactor- scale target design. This experience can be used for the development of the next-generation FST-layering module for construction of a prototype of a target factory for power laser facilities and inertial fusion power plants.

Cryogenic Hydrogen Fuel for Controlled Inertial Confinement Fusion (Cryogenic Target Factory Concept Based on FST-Layering Method)

A central element of a power plant based on inertial confinement fusion (ICF) is a target with cryogenic hydrogen fuel that should be delivered to the center of a reactor chamber with a high accuracy and repetition rate. Therefore, a cryogenic target factory (CTF) is an integral part of any ICF reactor. A promising way to solve this problem consists in the FST layering method developed at the Lebedev Physical Institute (LPI). This method (rapid fuel layering inside moving free-standing targets) is unique, having no analogs in the world. The further development of FST-layering technologies is implemented in the scope of the LPI program for the creation of a modular CTF and commercialization of the obtained results. In this report, we discuss our concept of CTF (CTF-LPI) that exhibits the following distinctive features: using a FST-layering technology for the elaboration of an in-line production of cryogenic targets, using an effect of quantum levitation of high-temperature superconductors (HTSCs) in magnetic field for noncontacting manipulation, transport, and positioning of the free-standing cryogenic targets, as well as in using a Fourier holography technique for an on-line characterization and tracking of the targets flying into the reactor chamber. The results of original experimental and theoretical investigations performed at LPI indicate that the existing and developing target fabrication capabilities and technologies can be applied to ICF target production. The unique scientific, engineering, and technological base developed in Russia at LPI allows one to make a CTFLPI prototype for mass production of targets and delivery thereof at the required velocity into the ICF reactor chamber.

On the cryogenic layer formation under conditions of high-frequency mechanical action

The results of a series of experiments using a piezovibration formation module for producing cryogenic targets with a given fuel layer structure are presented.

Diffusion filling with fuel gas of high-gain direct-drive cryogenic targets

To provide continuous operation of a reactor based on inertial confinement fusion (ICF), the thermonuclear burn region should be refilled with fuel with a frequency of 1 million targets per day. The first stage in the target production is diffusion filling of polymeric (CH) shells with fuel gas which is deuterium (D2) or deuterium–tritium (DT) mixture. The results of simulation of filling reactor-scale CH-shells (Ø ~ 4 mm) to a pressure of ~1100 atm at 300 K in the mode with a constant pressure gradient are presented. Simple and two-layer shells of compact and porous polymers are considered. The problems of constructing an optimum DT-filling scheme avoiding CH-shell fracture due to tritium beta decay are discussed.

Method of the phonon modulation of cryogenic hydrogen fuel structure in ITF targets

The possibility of spatial homogenization of the cryogenic hydrogen fuel structure in laser thermonuclear targets is considered. The results of a large cycle of experimental studies on low-temperature (T = 4.2 K) phonon modulation of the structure of solid hydrogen layers with various ortho-para compositions and its effect on the homogenization process rate are presented.