S. V. Polosatkin

Direct observation of anomalously low longitudinal electron heat conductivity in the course of collective relaxation of a high-current relativistic electron beam in plasma

The experimental results on a multiple-mirror trap GOL-3 with a short section of reduced magnetic field (“magnetic pit”) are presented. The reduced specific energy release from a relativistic electron beam in the pit brings about a region with a temperature several times lower than in the surrounding plasma. The existence of the low-temperature region directly demonstrates that the longitudinal electron heat conductivity is suppressed in the collective electron-beam interaction with plasma.

Study of the mechanism for fast ion heating in the GOL-3 multimirror magnetic confinement system

Results are presented from experimental studies of ion heating in the GOL-3 device. The experiments were carried out in a multimirror configuration with a local magnetic well. It was found that, during the injection of a relativistic electron beam, a decrease in the local density of the beam in a magnetic well, which is proportional to the decrease in the strength of the longitudinal magnetic field, results in the formation of a short plasma region with a low electron temperature. The measured longitudinal gradient of the plasma pressure corresponds to an electron temperature gradient of ∼2–3 keV/m. Axially nonuniform heating of the plasma electrons gives rise to the macroscopic motion of the plasma along the magnetic field in each cell of the multimirror confinement system. The mixing of the counterpropagating plasma flows inside each cell leads to fast ion heating. Under the given experimental conditions, the efficiency of this heating mechanism is higher than that due to binary electron-ion collisions. The collision and mixing of the counterpropagating plasma flows is accompanied by a neutron and γ-ray burst. The measured ratio of the plasma pressure to the vacuum magnetic field pressure in these experiments reaches 0.2.

Experimental study of the dynamics of neutron emission from the GOL-3 multimirror trap

In experiments on the plasma heating and confinement in the GOL-3 multimirror trap, a deuterium plasma with a density of ∼1015 cm−3 and an ion temperature of 1–2 keV is confined for more than 1 ms. The plasma is heated by a relativistic electron beam. The ion temperature, which was measured by independent methods, reached 1.5–2 keV after the beginning of the beam injection. Since such a fast ion heating cannot be explained by the classical energy transfer from electrons to ions through binary collisions, a theoretical model of collective energy transfer was proposed. In order to verify this model, a new diagnostics was designed to study the dynamics of neutron emission from an individual mirror cell of the multimirror trap during electron beam injection. Intense neutron bursts predicted by this model were detected experimentally. Periodic neutron flux modulation caused by the macroscopic plasma flow along the solenoid was observed. The revealed mechanism of fast ion heating can be used to achieve fusion temperatures in the multimirror trap.

Advanced Neutral Particle Analyzer for Fusion Plasma Diagnostics

Abstract An advanced neutral particle analyzer for the diagnostics of hot plasma has been designed and fabricated in the Budker Institute of Nuclear Physics. The analyzer measures the ion energy distributions of both bulk plasma ions as well of fast ions created by neutral beam injection. The main feature of the analyzer is the ability to simultaneously measure hydrogen and deuterium atoms. The design of the analyzer, calculation of registration efficiency, and possible applications for plasma diagnostics on GOL-3 and GDT facilities are presented.

Multichannel Thomson scattering diagnostics for the GOL-3 facility

A multichannel Thomson scattering diagnostics for measuring the plasma parameters in the GOL-3 facility was designed and created at the Budker Institute of Nuclear Physics of the Siberian Division of the Russian Academy of Sciences. The diagnostics operates at the fundamental harmonic of a neodymium laser (1.06 µm) and allows one to perform measurements over a wide range of electron temperatures and densities with high spatial and time resolutions. A special multipulse oscillator is developed that makes it possible to perform up to 20 measurements of the plasma temperature and density over a period of 300 µs during one shot. The laser used to generate probing radiation, the recording system, and the calibration procedure are described. Results from measurements of the temporal evolution of the plasma density in the GOL-3 in different stages of the discharge are presented to illustrate the system operation.

Investigation of subterhaertz emission from turbulent plasma heated by powerful REB at multimirror trap GOL-3

Study of Langmuir turbulence (LT) in plasma and LT-induced nonlinear phenomena remains an important topic of the fundamental plasma science. A distinctive LTs feature is possibility of electromagnetic radiation emission on plasma frequency (νp) and dual plasma frequency (2νp) due to processes of plasmon conversion on plasma density fluctuations and plasmon-plasmon merging respectively. Well-identified in solar radio-flares, these processes remained weakly studied in laboratory plasmas.

Features of high-power E-beam application for plasma heating in long open trap GOL-3

Recent results of experiments on high-energy content E-beam application for plasma heating in a multimirror trap GOL-3 are presented. Conditions for optimal neutralization of injected beam and its stable transport through long plasma column are defined. Effective electron and ion heating of plasma is observed.

Dense plasma heating by 200 kJ electron beam at the GOL-3-II facility

Collective interactions of a microsecond electron beam with a plasma and its fast heating is being investigated at the GOL-3-II facility. This activity is mainly directed for production of a hot dense (10/sup 15/-10/sup 17/ cm/sup -3/) plasma in long open trap in order to study the multimirror and wall confinement of such a plasma. The plasma that is already obtained and can in principle be obtained in this facility is of interest for a broad spectrum of applications, like controlled fusion, a pulsed neutron source, X-ray flash lamps, UV laser etc. Recent results performed at the GOL-3-II facility are presented. These are beam energy losses, plasma heating and electron and ion temperature measurements.