Energy Gain at the Impact Initiation of a Fusion Reaction
Energy Gain Optimization in the Fast Ignition Concept at the Impact Initiation of a Fusion Reaction
Tech Area / Field
- FUS-ICS/Inertial Confinement Systems/Fusion
- FUS-PLA/Plasma Physics/Fusion
- PHY-NGD/Fluid Mechanics and Gas Dynamics/Physics
3 Approved without Funding
FIAN Lebedev, Russia, Moscow
- VNIITF, Russia, Chelyabinsk reg., Snezhinsk
- Osaka University / Institute of Laser Engineering, Japan, Osaka
Project summaryThe Project is devoted to theoretical and numerical investigation of the physics of fast ignition of an inertial confinement fusion (ICF) target by impact of a laser-accelerated macroparticle. Fast ignition is considered now as the most perspective method to realize the controlled thermonuclear fusion basing on inertial confinement principles. The basic thesis of the fast ignition concept consists in temporal separation of thermonuclear fuel compression and heating processes. The essence of the approach is to slowly compress thermonuclear fuel of a spherical or cylindrical target by a pulse of the first energy source (driver) up to high density (several hundred of g/cm3), and then, under an action of the second driver pulse, to provide fast heating of a small part of compressed thermonuclear fuel and to initiate propagation of a fusion reaction wave from this area to the whole plasma mass. The heating of initiation area up to thermonuclear temperature (10 keV) should be carried out during the time while the compressed and heated substance of this area will not disintegrate. This circumstance makes rather hard requirements to the parameters of igniting driver which should ensure coming of energy of several tens kilojoules in a target area with the size of several tens microns at energy flux density not less than 1018-1019 W/cm2. The main advantage of fast ignition scheme is an opportunity to minimize the energy, which is needed for a target ignition, and to provide considerably (by the order of magnitude) higher coefficient of thermonuclear gain in comparison with a traditional scheme of a single driver irradiation of a target.
Realization of fast ignition scheme requires the solution of two main problems: the problem of generation of the igniting driver pulse with the above mentioned parameters, and the problem of efficient transmission of igniting pulse energy to the desired mass of the dense thermonuclear fuel. In the leading scientific institutions the researches in the fast ignition physics are fulfilled in the direction of usage of three types of igniting drivers: beams of fast electrons and fast ions generated under action of a high-power short laser pulse of 1018-1021 W/cm2 intensity on a target, and a macroparticle accelerated by a laser pulse. To provide the deposition of igniting driver energy into a target there were offered various constructions of spherical targets supplied with conical channels, and of cylindrical targets with specific edge walls.
The laser-accelerated macroparticle and the charged particle beams emitted from laser-produced plasma have, in potential, close capability to transform laser energy to self-energy and to pass this energy to compressed thermonuclear plasma. But for all that, from the point of view of facilitation of technical aspect of the igniting driver problem, the accelerated macroparticle is distinguished from charged particle beams by the fact, that for its acceleration up to velocity about 1000 km/s, which is necessary for an ignition, the usage of a short laser pulse with ultrahigh flux density is not required. The macroparticle can be accelerated by a laser pulse of nanosecond duration with moderate intensity about 1014–1015 W/cm2.
Interest to use the laser-accelerated macroparticle as the igniting driver especially increased after the publications made in 2005 by the scientists of the Institute of laser engineering of Osaka University (Japan) where a new perspective implementation of such ignition method was offered. According to this proposal, the macroparticle represents a constituent of a ICF-target, it itself contains thermonuclear substance and can be accelerated, basically, by the same laser pulse by which the main portion of a thermonuclear fuel is compressed. The part of a target containing main portion of thermonuclear fuel (a thermonuclear capsule) does not differ from suggested earlier fast ignition ICF-target construction with the channel for input of an igniting driver pulse radiation. It represents a spherical shell with a layer of DT-ice frozen on its interior surface. The shell is supplied with the conical channel whose narrow part is located inside the shell at certain distance from shell's center, and the wide part is placed outside of the shell. The distinction of the design is, that inside the channel,, the segment of concentric (relative to the thermonuclear capsule) spherical shell is located, which is the macroparticle to be accelerated. The distance between the segment of the shell and the center of a thermonuclear capsule exceeds radius of the latter and is chosen reasoning from the requirement that macroparticle to be accelerated up to necessary velocity.
For a physical justification of the fast ignition by impact of a macroparticle, one should investigate the complex of processes of macroparticle acceleration by a laser pulse up to a hypervelocity exceeding 1000 km/s, and hydrodynamics of its inelastic collision with a dense substance. Besides it, with reference to a target as a thermonuclear capsule with the conical channel, it is required to study the whole complex of problems related to the interaction of a macroparticle with walls of the channel, including hydrodynamic streams in both objects and the development of hydrodynamic instabilities. For an ignition of fusion reaction the macroparticle should be not only accelerated up to velocity not less than 1000 km/s, but also should have as high density as it is possible to efficiently transmit its energy during collision with preliminarily compressed thermonuclear fuel. Some of these processes were explored earlier, however only for velocities not exceeding 200 km/s. The problem of acceleration of a macroparticle by a laser pulse up to so high velocities is at the initial stage of investigation. The maximal velocity of laser-accelerated projectile reached in contemporary experiments is 600 km/s. The problem of a state of substance of a macroparticle accelerated up to so high velocity remains not investigated yet.
The main goals of the Project are:
- theoretical justification of the conception of fast ignition of an ICF-target by a laser-accelerated projectile;
- the definition of the optimal parameters of laser and ICF target which provide the realization of fast ignition concept by impact of a laser-accelerated projectile in the conical channel of a spherical thermonuclear capsule at maximal thermonuclear gain.
The scope of activity includes:
- investigation of the physics of laser-driven acceleration of macroparticle up to velocities exceeding 1000 km/s and physics of the macroparticle collision with a dense target;
- investigation of the physics of laser-driven acceleration and compression of a thermonuclear capsule and segment of a spherical along the conical channel;
- investigation of the physics of edge initiation of thermonuclear burning wave at high-speed impact by projectile.
- investigation of the physics of fast ignition at thermonuclear burning initiated by impact of macroparticle accelerated in the conical channel of a spherical thermonuclear capsule.
The following main results of Project fulfillment are expected:
- physical and mathematical models of processes of low-entropy acceleration of a macroparticle by a laser pulse up to velocity exceeding 1000 km/s will be built;
- physical and mathematical models of transfer of energy from a macroparticle to a dense substance, and initiation of self-sustaining wave of fusion reactions in the latte, will be built;
- the parameters of a laser pulse and a target which provide the maximal value of thermonuclear gain with reference to the above enunciated concept of fast ignition by the impact of a macroparticle laser-accelerated in the conical channel of a spherical thermonuclear capsule will be defined.
The basic research approach will be carrying out the numerical simulations of the following processes: thermonuclear capsule compression and acceleration of a macroparticle by a laser pulse, collision of a macroparticle with a massive target. Such a simulations will be carried out using most advanced mathematical codes for the calculation of one-dimensional, two-dimensional and three-dimensional hydrodynamics, which are in possession of the research teams, P.N. Lebedev Physical Institute of Russian Academy of Sciences (LPI) and Russian Federal Nuclear Center – Ye.I. Zababakhin All-Russian Scientific Research Institute for Technical Physics (RFNC-VNIITF). These codes provide numerical calculation of all most important processes of laser radiation interaction with matter as well as plasma, nuclear, radiation, relaxation and hydrodynamics processes. The codes were designed, permanently perfected and used by participants of the Project, especially, for numerical simulation of hydrodynamics of laser-produced plasma. The codes were multiply tested on the experimental data.
The competence of Project's participants based on their vast previous experience of the work in the fields related to the Project subject. The team of Russian participants of the Project includes leading theoreticians in the physics of laser radiation interaction with matter, hydrodynamics of plasma and physics of inertial fusion targets. In their previous researches the well-known in Russia and abroad results were obtained, which have a key importance for investigation on Project. Among them there are: theory of acceleration of thin plane and spherical targets under an action of a laser pulse, the efficiency of laser pulse energy transformation to the energy of hydrodynamic motion of a plane layer of the arbitrary width, theory of hydrodynamic instabilities development at impact of a plane macroparticle with the dense target, fast ignition criteria for ICF-targets and others.
It is supposed, that the Project will be fulfilled in tight cooperation with Collaborating Institution of the Project - Institute of laser engineering of Osaka University (Japan). By preliminary arrangement with collaborating institution forms of co-operation will include not only discussions of the Project working plan and the exchange of the scientific information, but also will include the concrete joint researches, namely, the numerical simulations will be carried out by Participating Institutions to support the experiments of Collaborating Institution, and experiments will be performed by the collaborating institution on the basis of conclusions and guidelines from the results of theoretical investigations of Participating Institutions.
The principal goals and tasks of ISTC will be realized in the process of project fulfillment, namely:
- the scientists of RFNC-VNIITF engaged earlier in the development of nuclear weapon in Russia will be given an opportunity to apply their efforts to the development of civil fundamental scientific problems and to integrate, by this way, into the international scientific community;
- a support will be given to the solution of a national and international technical problem, namely, the development and creation of new ecologically pure energy sources on the base of of effective method of realization of controlled thermonuclear reaction.
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