V. V. Kurkuchekov

Temporal structure of double plasma frequency emission of thin beam-heated plasma

In the work presented here dynamics of spiky microwave emission of a beam-heated plasma near the double plasma frequency in ∼100 GHz band was studied. The plasma is heated by 80 keV, ∼2 MW, sub-ms electron beam that is injected into the multiple-mirror trap GOL-3. The beam-heated plasma diameter is of the order of the emitted wavelength. Modulation of individual emission spikes in the microwave radiation is found. The radiation dynamics observed can be attributed to a small number of compact emitting zones that are periodically distorted.

Heating of tungsten target by intense pulse electron beam

A test facility for experimental simulation of transient heat loads in ITER divertor with the use of high power electron beam is developed at the Budker Institute of Nuclear Physics. This report presents an experimental study of the absorption of the electron beam with an incident heat power flux of 10-50 GW/m2 on the area of about 2 cm2 of a tungsten target. The electron beam has duration of 0.1-0.3 ms and electron energy of 80-95 keV, Diagnostics for measuring of the beam parameters on the target are briefly discussed. Results of measurement of the beam profile and calorimetry of beam energy deposited in tungsten sample at ELM-like heat load are presented.

Development of Extended Heating Pulse Operation Mode at GOL-3

Novel technology of electron beam generation for plasma heating in GOL-3 was developed and for the first time used in the experiment. The distinctive features of the new beam are non-relativistic energy, medium power and sub-ms duration. The experiments were done at the following beam and plasma parameters: ~100 keV, ~10 MW, >100 μs, ~1020 m-3. The beam was safely transported through the 13-m-long deuterium-filled multiple-mirror solenoid. The plasma was created and then heated by the beam. Main physical task for the reported experiments was to reach quasi-stationary plasma conditions during the long-pulse beam injection.

Microwave Generation During 100 keV Electron Beam Relaxation in GOL-3

First experimental results on microwave radiation at double plasma frequency from plasma heated by ~100 keV, 2-10 MW electron beam of ~100 μs duration in GOL-3 are presented. Measurements were done in 75-200 GHz band. The spectrum was peaked at ~94 GHz at ~3·1013 cm-3 plasma density, the temporal behavior of radiated power was spiky. The generation efficiency reached ~1% of total beam power.

Observation of dust particles ejected from tungsten surface under impact of intense transient heat load

A test facility for experimental simulation of transient heat load expected for ELMs type I events in ITER is developed at BINP SB RAS. Dynamics of tungsten particles in the ablation plume is investigated by small-angle light scattering technique and using fast CCD and ICCD cameras. The threshold of intense particle generation, sizes and velocities of particles ejected from the surface are estimated.

Novel Injector of Intense Long Pulse Electron Beam for Linear Plasma Devices

A novel high-power (10 MW) sub-millisecond electron beam is developed for injection into the open (linear) plasma devices. The beam is produced by extraction of electrons from a plasma of pulsed arc discharge in hydrogen. The beam is extracted and accelerated with multiaperture diode-type electron optical system with 241 small round apertures, which are arranged in a hexagon-al pattern. The injector prototype was installed into the end plasma tank of GOL-3 multiple mirror trap and tested to produce an electron beam with up to 100 keV electron energy, about 100 A total beam current and 0.7 ms or longer pulse duration. In a series of preliminary experiments the electron beam was injected into the GOL-3 plasma chamber filled with deuterium gas with a density of 1014-1015cm-3 and transported in a corrugated magnetic field ( up to 1.4 T) along the trap at a distance of 12 m.

Submillisecond Electron Beam for Plasma Heating in Multi-Mirror Trap GOL-3

Abstract Experiments on plasma heating in open magnetic traps require a powerful electron beam with pulse length of 0.1–1 ms. Such a beam is expected to obtain in the source with a plasma cathode and high perveance multiaperture electron optical system. An appropriate technology is being developed at Budker Institute of Nuclear Physics (BINP), Novosibirsk. Here we introduce a prototype electron beam injector with the following design parameters: energy of electrons up to 150 keV, pulse duration of >0.1 ms and beam current up to a few hundred amperes. The injector is intended to operate in an external axial magnetic field of ~0.1 T. In this paper, the design of injector prototype is described and the first test experiments are presented.

Observation of the tungsten surface damage under ITER-relevant transient heat loads during and after electron beam pulse

Wide-area (2 cm2) high-power (up to 7 MW) submillisecond electron beam source was applied for generation of intense pulsed heat loads on tungsten sample. Various diagnostics sets were used for in-situ research of the surface damage: IR imaging of the front view of the target, capturing of the reflection pattern of continuous wave laser radiation, recording of intensity of thermal radiation from several spots of the surface. Sample was exposed to a various heat loads near and above melting threshold. Formation of the crack network on the surface and its development with successive pulses was observed. Two-dimensional temperature distribution was obtained after heating at the cooling stage. Melting and spalling of material were shown on severe damaged target. Propagation of the cracks along the surface at a depth of 0.1 – 0.2 mm was revealed with transverse microsections. Circular motion of the molten layer was found with subsequent exposures.

MHD Activity in GOL-3 During Injection of Long-Pulse Electron Beam

Magnetic activity of plasma during the injection of 2-8 MW non-relativistic electron beam of sub-millisecond duration in GOL-3 is studied. The main parameters of fluctuations of the magnetic field are discussed. In most experiments the m = 1 azimuthal mode has the largest value, although, higher modes stay significant. Amplitude of the largest perturbations is ~1/2 of the beam radius. The phase grows monotonically, rotational velocity agrees well with the expected E×B drift. Longitudinal velocity of the fluctuations was also measured, its value v ~ 107 cm/s is close to the ion sound speed for Te ~ 100 eV.

Multiple pulse magnetized electron beam injection in deuterium gas

Results of experiments on injection of a sequence of several electron beam pulses (80–90 keV, 20–75 A, ∼30 μs) into 1019–1021 m−3 deuterium plasma are presented. The first beam pulse was injected into deuterium gas, the following pulses propagated through residual plasma that survived the inter-pulse periods. A typical pulse duration was of the order of 106 ω p − 1 that is much longer than most of the interaction-related processes. However, we noticed significant differences in plasma processes between the first pulse and the rest ones. A suggested physical factor behind those differences is longitudinal plasma current that develops during the first beam pulse.