A. V. Anikeev

Spatial profiles of fusion product flux in the gas dynamic trap with deuterium neutral beam injection

Recently, a plasma with energetic deuterons has been produced in the gas dynamic trap (GDT) experiment under skew injection of 4 MW, 15–17 keV deuterium neutral beams. The GDT is a long, axially symmetric magnetic mirror device with a high mirror ratio. The deuterium neutral beams have been injected at the mid-plane of the device under 45° to the axis. High anisotropy of the fast ion angular distribution results in a strong peaking of the fast ion density at the turning points near the end mirrors. The axial profile of DD fusion product fluxes has been measured and found to be strongly peaked in the same regions. The characteristics of the profiles are consistent with the classical mechanism of fast ion relaxation caused by two-body Coulomb collisions with plasma particles. This observation validates an approach used in a GDT based neutron source, in which the regions of high neutron flux would be surrounded by the testing zones for fusion material irradiations.

Confinement of Hot Ion Plasma with β = 0.6 in the Gas Dynamic Trap

Abstract A so called vortex confinement of plasma in axially symmetric mirror device was studied. This recently developed approach enables to significantly reduce transverse particle and heat losses typically caused by MHD instabilities which can be excited in this case. Vortex confinement regime was established by application of different potentials to the radial plasma limiters and end-plates. As a result, the sheared plasma flow at periphery appears which wraps the plasma core. Experiments were carried out on the gas dynamic trap device, where hot ions with a mean energy of Eh ≈ 9 keV and the maximum density of energetic ions nh ≈ 5·1019m-3 were produced by oblique injection of deuterium or hydrogen neutral beams into a collisional warm plasma with the electron temperature up to 250 eV and density nw ≈ 2·1019m-3. Local plasma β approaching 0.6 was measured. The measured transverse heat losses were considerably smaller than the axial ones. The measured axial losses were found to be in a good agreement with the results of numerical simulations. Recent experimental results support the concept of the neutron source based on the gas dynamic trap.

Novosibirsk Project of Gas-Dynamic Multiple-Mirror Trap

Development of a new linear device for confinement of fusion plasmas is under way in the Budker Institute of Nuclear Physics, Novosibirsk. The new device combines features of existing GOL-3 and GDT traps, namely, the central GDT-like cell with sloshing ions produced by intense neutral beam injection, and the multiple-mirror end sections for suppression of axial plasma losses. It is designed as a prototype of an energy-efficient neutron source and a testbed for development of mirror-based fusion reactors.

Progress in Mirror-Based Fusion Neutron Source Development

The Budker Institute of Nuclear Physics in worldwide collaboration has developed a project of a 14 MeV neutron source for fusion material studies and other applications. The projected neutron source of the plasma type is based on the gas dynamic trap (GDT), which is a special magnetic mirror system for plasma confinement. Essential progress in plasma parameters has been achieved in recent experiments at the GDT facility in the Budker Institute, which is a hydrogen (deuterium) prototype of the source. Stable confinement of hot-ion plasmas with the relative pressure exceeding 0.5 was demonstrated. The electron temperature was increased up to 0.9 keV in the regime with additional electron cyclotron resonance heating (ECRH) of a moderate power. These parameters are the record for axisymmetric open mirror traps. These achievements elevate the projects of a GDT-based neutron source on a higher level of competitive ability and make it possible to construct a source with parameters suitable for materials testing today. The paper presents the progress in experimental studies and numerical simulations of the mirror-based fusion neutron source and its possible applications including a fusion material test facility and a fusion-fission hybrid system.

The GDT Experiment: Status and Recent Progress in Plasma Parameters

Abstract This paper presents a brief review of experimental results obtained on the Gas Dynamic Trap (GDT) device during the last few years. Special attention is paid to the problems of longitudinal plasma confinement and suppression of transverse transport caused by magnetohydrodynamic instabilities in mirror traps with an axisymmetric magnetic field configuration. We also consider problems of auxiliary electron cyclotron resonance heating in the GDT plasma. Electromagnetic fluctuations driven by anisotropic high pressure plasma in GDT will be discussed as well as influence of these fluctuations on plasma confinement.

Mirror based fusion neutron source: Current status and prospective

The paper presents a recent progress in experimental studies and status of numerical simulations of the mirror based fusion neutron source developed by the Budker Institute of Nuclear Physics (Novosibirsk, Russia) and its possible applications including a fusion material test facility and a fusion-fission hybrid system. Current research activity is supported by the Russian Science Foundation (project N 14-50-00080).

Recent progress of plasma confinement and heating studies in the gas dynamic trap

The paper includes a brief overview of previous researches on the stabilization of MHD instabilities, study of micro-instabilities, and demonstration a tangible increase of the electron temperature with application of auxiliary ECR heating. A review of the results of recent researches related to application of microwave radiation for plasma generation, and plasma heating in the GDT device is presented. The paper summarizes also recent results of researches that oriented on study of expander physics.

Parameters of a Fusion Neutron Source Based on the Recent GDT Experimental Data and Possible Applications

Abstract Substantial progress in experimental results was demonstrated over the last three years at the GDT facility (a hydrogen prototype of a fusion neutron source) in the Budker Institute: the electron temperature has been increased up to 0.6 keV, and the relative plasma pressure β has exceeded 0.5 in a quasi-stationary regime. These parameters are records for axisymmetric open mirror traps. The first part of this paper presents the results of numerical simulations for a moderate fusion neutron source based on the achieved GDT experimental data. The second part of the paper is focused on the latest numerical studies of a fusion-fission hybrid system with a mirror-based neutron source.

Study of Microinstabilities in Anisotropic Plasmoid of Thermonuclear Ions

Abstract The following work presents the results of investigation of microinstabilities in the anisotropic synthesized hot ion plasmoid (SHIP). Plasmoid is located in a small mirror section that is installed at one side of the GDT facility, which is an axially symmetric magnetic mirror device of gas dynamic trap type. To define the type and the parameters of the developing microinstability a set of high-frequency electrostatic and magnetic probes was used. The microinstability observed in the additional section of GDT is the Alfven ion cyclotron instability (AIC), because of small azimuthal wave numbers, magnetic field vector rotating in the direction of ion gyration and oscillation frequency below the actual ion cyclotron frequency. AIC instability threshold was registered at the following plasma parameters: fast ion density n > 3 × 1013 cm-3, ratio of ion pressure to magnetic field pressure β ≈ 0.02, anisotropy A = 40, ai/Rp ≈ 0.23, where ai is the ion gyroradius and Rp is the plasmoid radius.

IMPROVED REGIMES IN HIGH PRESSURE MAGNETIC DISCHARGES

Field-Reversed Configuration (FRC) [1] and Gas-Dynamic Tr ap (GDT) [2] represent compact system, which is a special magnetic geometry for plasma confinement. Theoretical and experimental study of gas-dynamic regimes with high energy content is carried out. The approach to a high beta (b is the ratio of plasma pressure to magnetic pressure) magnetic systems assumed different regimes of plasma with beta > 0.5 that is proper to compact devices such as tori and mirror traps. Both FRC and GDT traps are axial symmetric configurations, has open field lines and poloidal magnetic field only. Last experimental results on GDT have shown the po ssibility to build the stationary system with high beta. Analysis of the global energy and particle balance together with the Monte-Carlo equilibrium modelling allowed to conclude that two-component plasma confined in a steady-state regime. The characteristic plasma lifetimes are 4 to 5 times less then the experiment duration. A peripheral gas-puff near the mirror region enabled to maintain the radial profile of background plasma during the all neutral beam injection (NBI) pulse. This report is focused mainly on ambipolar effect and the po ssibility of further increasing the fast ion energy content and β. Improved gas-dynamic regimes in high pressure magnetic discharges and microinstabilities arising are described. Synthesized hot ion plasmoid (SHIP) experiment in the compact mirror section attached to the GDT central cell and the scheme of compact tori (FRC formation) for the compact mirror cell of GDT device are presented. Fusion prospects (reactor, neutron source, material studies) of such systems with high-energy (fast) particles [3, 4] and hybrid FRC + GDT scheme proposed by author from Bauman Moscow State Technical University (BMSTU) are discussed. NOMENCLATURE AND ABBREVIATION b = ratio of plasma pressure to magnetic pressure τE = energy lifetime