Application of dense plasma focus devices and lasers in the radiation material sciences for the goals of inertial fusion beyond ignition

Specimens of materials for prospective use in chambers of nuclear fusion reactors with inertial plasma confinement,namely,W,ODS steels,Eurofer 97 steel,a number of ceramics,etc.,have been irradiated by dense plasma focus devices and a laser in the Q-switchedmode of operation with a wide range of parameters,including some that noticeably exceeded those expected in reactors.By means of 1-ns laser interferometry and neutron measurements,the characteristics of plasma streams and fast ion beams,as well as the dynamics of their interaction with solid-state targets,have been investigated.3D profilometry,optical and scanning electron microscopy,atomic emission spectroscopy,X-ray elemental and structural analyses,and precise weighing of specimens before and after irradiation have provided data on the roughening threshold and the susceptibility to damage of the materials under investigation.Analysis of the results,together with numerical modeling,has revealed the important role of shock waves in the damage processes.It has been shown that a so-called integral damage factor may be used only within restricted ranges of the irradiation parameters.It has also been found that in the irradiation regime with well-developed gasdynamic motion of secondary plasma,the overall amount of radiation energy is spent preferentially either on removing large masses of cool matter from the material surface or on heating a small amount of plasma to high temperature(and,consequently,imparting to it a high velocity),depending on the power flux density and characteristics of the pulsed irradiation.

Scenario of a magnetic dynamo and magnetic reconnection in a plasma focus discharge

The paper discusses a possible energy transformation that leads to the acceleration of fast ions and electrons.In plasma-focus discharges that occur during deuteriumfilling,which have amaximumcurrent of about 1MA,the accelerated deuterons produce fast fusion neutrons and fast electrons hard X-ray emissions.Their total energy,which is of the order of several kilojoules,can be delivered by the discharge through a magnetic dynamo and selforganization to the ordered plasma structures that are formed in a pinch during the several hundreds of nanoseconds of the pinch implosion,stagnation,and evolution of instabilities.This energy is finally released during the decay of the ordered plasma structures in the volume between the anode face and the umbrella front of the plasma and current sheath in the form of induced electric fields that accelerate fast electrons and ions.