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The notable feature of cadmium tungstate (CWO) is quite long ( ∼ 14. 5 μ s ) decay time of its brightest scintillation component. In this paper, the technique and results of high dynamic range measurements of CWO afterglow are discussed. Samples were irradiated by bremsstrahlung of a ∼ 0.5 MeV, 6 μ s electron beam. The afterglow tail of the scintillation curve was measured down to the relative amplitude

The paper presents experimental results from the SMOLA device that is the first facility with a helical mirror section of the magnetic field. This device is built in the Budker Institute of Nuclear Physics for the verification of the helical mirror confinement idea that is the recently introduced technique of the active control of axial losses from a confinement zone. Theory predicts that with rotating plasma, a helical mirror will provide suppression of the axial plasma flow and, simultaneously, density pinching to the axis. Experiments demonstrated that plasma density at the exit from the transport section is suppressed with activation of the helical field, the effect is significant and highly reproducible. The most pronounced effect is observed on the plasma periphery, where the mirror ratio is the highest. The integral suppression ratio reaches 2–2.5 in the discussed experiments. Experimental results are compared with simplified theoretical estimates. The integral suppression ratio matches the simple theoretical estimates even if the transversal diffusion is neglected.

Results, obtained during the last decade on linear traps in Novosibirsk, verified the original concepts and led to discovery of new ways of plasma confinement in linear traps. It turns out that the multiple-mirror confinement, once thought to be suitable for pulsed fusion only, can work in tandem with gas-dynamic traps. Its helical-mirror variant can provide additional advantages for confinement of rotating plasmas such as radial and axial plasma pinch fluxes. The specially designed gas-dynamic mirrors can be run in the high-β “diamagnetic” regime, closely resembling the field-reversed configurations both in shape and in the quality of axial confinement. These new ideas form the groundwork of the possible road for linear traps to fusion.

Novel concept of the longitudinal plasma flow suppression by active plasma pumping in helicoidal magnetic field in mirror traps was proposed recently. Concept exploration device SMOLA is now being constructed to prove the possibility of the suppression and determine basic scalings of ist effectiveness. Technical solutions of the SMOLA device are described in the article. Vacuum system, magnetic system, plasma source and the source of the radial electric field are discussed. Estimations of the biasing required for optimal confinement are given. Physical program fort he first experiments is also proposed.

A new control system for capacitive energy storage with a rated energy content as high as 16 MJ is described. Capacitive energy storage has been used since 1987 to supply power for the pulsed magnetic system of the GOL-3 multiple-mirror trap. It has an operating voltage of 6 kV and consists of 6000 IK-6-150 capacitors that are located in six remote rooms together with the necessary infrastructure. The system for control and data acquisition was built using Arduino microcontroller boards operating as a distributed network of remote servers. The client part of the control system uses a personal computer with a standard configuration; communication with remote servers is effected by the TCP/IP protocol. The control system was put into regular operation at devices of the GOL-3 facility in the early 2016.

Results of spectral and magnetic diagnostics of plasma differential rotation in the GOL-3 multiplemirror trap are presented. It is shown that the maximum frequency of plasma rotation about the longitudinal axis reaches 0.5 MHz during the injection of a relativistic electron beam into the plasma. The data of two diagnostics agree if there is a region with a higher rotation frequency near the boundary of the electron beam. Plasma differential rotation can be an additional factor stabilizing interchange modes in the GOL-3 facility.

The review presents experimental studies of plasma-surface interaction and materials behavior under plasma loads done in the multiple-mirror trap of the GOL-3 facility. In the experiments for the PSI, the energy density in the extracted plasma stream varies from 0.5 to 30 MJ/m2. Parameters of near-surface plasma measured by a set of diagnostics are reviewed. Surface patterns of targets exposed to the plasma are analyzed. The erosion depth depends on the energy loads—it rises from 0 to 600 μm at 0.5 and 30 MJ/m2, correspondingly. Cracking and evolution of graphite and tungsten surface morphology are discussed. The enthalpy of brittle destruction of graphite (10 kJ/g), which determines the threshold of bulk damage of targets irradiated with a charged-particle flux with large penetration depth, was determined. Comparison of different facilities for PSI studies are presented. Heat flux play a key role to the target surface erosion.

The study is devoted to tungsten surface modification after irradiation at the GOL-3 facility with plasma loads corresponding to the ITER type I ELMs. In order to emulate heating with a steady plasma flux in the ITER divertor, some of the tungsten samples were preheated up to 500 °C. It was found out that the behavior of the surface modification (the crack pattern and the number of bubbles) depends on the initial temperature of the targets. While the orientation of major crack networks correlates with the direction of machining of the samples. Afterwards we have observed the process of craters’ formation caused by dust particle impacts.

Currently, the GOL-NB multiple-mirror trap is being developed at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. The main scientific goal pursued by building GOL-NB is direct demonstration of suppression of longitudinal losses of particles and energy from the trap by using sections with a multiple-mirror magnetic field, which can be attached to the central gas-dynamic trap. Plasma heating in GOL-NB will be accomplished by neutral beam injection with a power of up to 1.5MW. The paper presents the first results of modeling the dynamics of the plasma parameters and fast ions under the reference operating scenario of the trap in which traditional short magnetic mirrors, rather than multiple-mirror sections, are attached to the central trap. In such a configuration, the plasma lifetime in the trap is expected to be minimal. The modeling was performed by using the DOL kinetic code. As a result, the initial conditions of the experiments are refined and the requirements to the system of maintaining the particle balance in the trap are determined.

A novel concept of helical mirror confinement with active axial and radial plasma flow control is discussed. The idea relies on the retarding force that appears when biased plasma experiences rotation in crossed electrical and helical mirror magnetic fields. Preparations for its experimental study started in Budker Institute of Nuclear Physics, Novosibirsk. Possible parameter space for a concept-exploration-class device SMOLA is identified. Details of numerical optimization of the magnetic structure of the device are presented. The main physical task for the SMOLA experiment will be direct demonstration of the helical mirror performance in simple experimental conditions at reasonably low plasma parameters.

The program of the deep upgrade of the GOL-3 multiple-mirror trap is presented. The upgrade is aimed at creating a new GOL-NB open trap located at the GOL-3 site and intended to directly demonstrate the efficiency of using multiple-mirror magnetic cells to improve longitudinal plasma confinement in a gasdynamic open trap. The GOL-NB device will consist of a new central trap, adjoint cells with a multiple-mirror magnetic field, and end tanks (magnetic flux expanders). Plasma in the central trap will be heated by neutral beam injection with a power of up to 1.5 MW and duration of 1 ms. At present, physical experiments directed at developing plasma technologies that are novel for this facility are being carried out using the 6-m-long autonomous part of the GOL-3 solenoid. The aim of this work was to develop a method for filling the central trap with a low-temperature start plasma. Transportation of a plasma stream from an arc source over a distance of 3 m in a uniform magnetic field with an induction of 0.5–4.5 T is demonstrated. In these experiments, the axial plasma density was (1–4) × 1020 m–3 and the mirror ratio varied from 5 to 60. In general, the experiments confirmed the correctness of the adopted decisions for the start plasma source of the GOL-NB device.

This paper describes results of GOL-PET experiments on subterahertz (0.1–0.5 THz) emission from a magnetized plasma column during passing of a high-current $(\sim \hbox{10 kA})$ relativistic $(\sim \hbox{0.6 MeV})$ electron beam. The subterahertz radiation is generated in the plasma due to high-level turbulence induced by two-stream instability of the electron beam. These experiments are carried out at the specialized GOL-3T device. For the plasma density range 10 $^{14}\hbox{–10}^{15}~\hbox{cm}^{-3}$ , we have studied emission dynamics from the plasma column in its transverse and longitudinal directions. The spectral composition and polarization of the radiation was also investigated.

New plans for next-step experiments on a multiple-mirror confinement in GOL-3 are discussed. The proposed changes in the hardware configuration include separation of the existing GOL-3 device into two independent plasma facilities. The first device will continue research on physics of highly turbulent electron-beam-heated plasma. It will use the existing generator of the electron beam and a shortened part of the existing solenoid. The second device will be devoted to a new experimental program on studies of efficiency of multiple-mirror end sections that should decrease power and particle losses from the trap. Details of the physics and upgrade plans for the new device, tentatively named GOL-NB, are discussed.

The first plasma campaign was completed in a start configuration of the GOL-NB multiple-mirror trap. The device included a 4-m-long high-field section, two end sections of magnetic flux expanders and a short temporary section for commissioning of two 25 keV, 0.75 MW neutral beams. Low-temperature start plasma was created by a coaxial arc plasma gun. The main objective of the first experiments is to develop and characterize the low-temperature plasma stream that will be used later for filling the central trap of GOL-NB with the start plasma. Plasma parameters and operation regimes are reported.

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...

The paper summarizes recent advances in physics of multiple-mirror confinement. GOL-3 in Novosibirsk is the only existing large-scale device of this type. Achieved plasma parameters are: n ~ 1021 m...

The paper presents experimental investigations of plasma-surface interaction and materials behavior under plasma loads relevant to type I ITER ELMs. The experiments were performed with quasi-statio...

Investigation results for electromagnetic radiation emission induced by strong Langmuir turbulence driven by a microsecond relativistic electron beam are presented. The radiation is associated with...

The latest experimental campaign at the GOL-3 multiple-mirror trap was mainly aimed at features of heating and stability of the electron-beam-heated turbulent plasma. The discussed experiments feat...

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.

The paper reviews recent experimental results from GOL-3. Currently efforts are focused on further development of a physical database for multiple-mirror confinement systems and also on an upgrade of plasma heating systems of GOL-3 device. In general, current GOL-3 parameters demonstrate good prospects of a multiple-mirror trap as a fusion reactor.

New operation regime with a high-mirror-ratio corrugation at first 2 meters of GOL-3 plasma was studied. Five corrugation periods of 44 cm length were created with mirror ratio R ≈ 2.7 by means of special configuration of a power feed of existing solenoid coils. First data on the plasma heating, confinement and features of neutron emission from the strongly corrugated plasma in the above conditions are presented.

Main results of researches on plasma heating and confinement of dense plasma in the multimirror trap GOL-3 are presented.Recently magnetic system of the facility was converted into completely multimirror one. This results in further improvement of energy confinement time of plasma with ion temperature {approx}1 keV. Collective plasma heating by {approx}120 kJ ({approx}8 {omega}s) relativistic electron beam results in T{sub e} {approx} 2 keV at {approx}10{sup 21} m{sup -3} density. High T{sub e} exists for {approx}10 {mu}s. To this time T{sub i} reaches {approx}2 keV. Ion temperature keeps at the high level during {approx}1 ms. The energy confinement time sufficiently increases and a value of n{tau}{sub E} = (1.5-3).10{sup 18} m{sup -3}s.

Study of a dense ({approx}10{sup 21} m{sup -3}) plasma heating by a relativistic electron beam and confinement of the plasma in multimirror magnetic field is carried out at the GOL-3 facility. The high-resolution spectral system in the visible region is used for investigation of plasma parameters.The analysis of the shape of D{sub {alpha}} spectral line shows that wings of this line are determined by the Doppler broadening from atoms being in the hot plasma core at high-temperature operation regime. A survey spectrometer with spatial and time resolution was used in addition to high-resolution spectrometer for detail study of this regime. Results of radial distribution measurements of D{sub {alpha}} line radiation show the presence of neutral deuterium in the hot plasma core. Ion temperature of the hot plasma achieves 2 keV.The evolution of radial distribution of D{sub {alpha}} line radiation, diagnostics features and results on ion temperature dynamics in the hot plasma core are presented in the paper.

Dense plasma heating by a relativistic electron beam and its confinement are studied in the multiple mirror trap GOL-3. Axial currents, which exist in the system, cause helical structure of the magnetic field. The safety factor q is shown to be below unity on the axis. Experimental data on the distribution and evolution of currents, structure of the magnetic field, and their influence on confinement and on MHD activity are discussed.

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 a...

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...

Experiments on plasma heating by a high power electron beam at the GOL-3 facility have shown, that ion temperature with a multiple mirror configuration of the magnetic field is much higher than for plasma heating in a simple solenoid. A new mechanism of fast collective heating of a plasma ions is suggested. The efficiency of the heating depends on local density of the beam electrons. In the corrugated magnetic field this creates a periodical longitudinal variation of plasma pressure during the beam injection. Then the pressure gradients result in plasma motion towards the midplane of each magnetic cell. Numerical simulations and special experiments demonstrate that fast thermalization of the energy of the directed plasma motion occurs. This mechanism requires about one ion-ion collision time that is much faster than usual electron-to-ion energy transfer time.

New experimental results on magnetic compression and transport of low-temperature arc plasma are presented. In the experiments, the transport efficiency of the plasma stream in a multiple-mirror configuration was compared with the same in a uniform solenoidal field. The magnetic compression ratio of the plasma stream varied from 5 to 60 at the initial diameter of 5 cm. As the result, the plasma with (1 – 4)×1020 m-3 density at the axis was obtained at ∼3 m distance from the plasma source. Theory predicted that a multiple-mirror magnetic field should not significantly decelerate and weaken collisional plasma. The experiment confirmed this prediction. In the presented work, we simulated the baseline scenario of GOL-NB filling by cold start plasma.

Recently high plasma parameters were reached in experiments on plasma heating in the multi-mirror open trap GOL-3. In these experiments deuterium plasma with density 10-10 cm in the 12-m trap with corrugated magnetic field of 4.8T/3.2T was heated by a relativistic electron beam of eU ≤ 0.8 MeV, I ≤ 20 kA, j ~ 1-2 kA/cm, pulse duration ~ 9 μs and angular spread θ ≤ 0.2 rad. The electron temperature Te ~ 1-4 keV and ion one to Ti ~ 1-2 keV were reached. After the beam pulse the electron temperature of the plasma quickly (~ 20 μs) decreased to ~100 eV. In turn, this leads to an increase in the rate of cooling of ions through the ion-electron collisions, which, together with particle losses determines the energy confinement time of plasma as 0.5-1 ms. To increase the plasma parameters a prolonged heating of the plasma by the electron beam is proposed. The paper considers basic physical phenomena in the beamplasma interaction and required parameters of the longpulse beam. A choice of long pulse beam parameters is based on the obtained experimental results and scalings. Then estimates of the expected plasma parameters under the influence of the new beam have been done.

Thomson scattering diagnostics has been updated to allow measurements at two instants of time for either of two spatial points in plasma during a single plasma discharge. Laser produces now two 15J...

The paper presents new experimental results from the GOL-3 facility on stabilization of some beam instability modes by controlled conditions at an exit beam receiver. In the experiments the space n...

Boreskov Institute of Catalysis, 5 Lavrentjev Avenue, Novosibirsk, 630090, Russia e-mail: A.A.Shoshin@inp.nsk.su The studies of exposing of targets by hot-electron plasma exhaust from the multi-mirror trap GOL-3 are carried out. The results of Raman and SEM studies of surface modification of carbon materials with different ordering range of sp2 fraction (different graphite and glassy carbon) exposed by pulsed hot hydrogen plasma with energy density up to 8 MJ/m

Experiments on fast plasma heating by the relativistic electron beam in the GOL-3 facility succeeds in the creation of a 10 15 cm -3 plasma with electron temperature of up to a few keV. The heating is produced due to two-stream instability of the beam that causes high level of plasma microturbulence. The experiments show some specific features of plasma behaviour during the beam injection. The beam-induced turbulence is the reason of non-classical transport processes in the plasma. Anomalies in longitudinal thermal conductivity, resistivity of the plasma and in lifetime of hot electrons are observed. Transition to classical transport coefficients occurs when the plasma turbulence disappears after the beam injection stops.

This contribution presents recent results of pellet technologies development for plasma fuelling in magnetic confinement machines with open or closed magnetic configuration. The current status of ITV7 pellet injector for GOL3 multimirror linear machine, PGS2.2 pellet guide system of ITV4 in-situ pellet injector for TUMAN-3M tokamak and ITV5 centrifuge pellet injector for Globus-M spherical tokamak is reported. New results on modeling of tangential pellet injection into TUMAN-3M tokamak are discussed as well.

Recently GOL-3 has been reconfigured to a multimirror trap with improved confinement and high ion temperature. A dense plasma is created with a life time in the millisecond range. BTI neutron bubbl...

The GOL-3-II facility was used for the investigation of the interaction of a high-power plasma stream with solids. The experiments allowed the study of the properties of the dense plasma formed in front of materials under action of the fast electrons flowing out the open trap. Target plasma from entrance foil with density 10 16 cm -3 has the expansion velocity 2-4 10 6 cm/c. Explosive-like erosion of the exit graphite receiver was been observed. Formation of a dust cloud is a feature of this phenomenon. Properties of the dusty particles are discussed.

Review of the experimental results for the last two years on study of dense plasma heating and confinement in a long multimirror trap GOL-3 is presented. This facility is an open trap for confineme...

Recent results of the experiments at GOL-3 facility are presented. In present configuration of the device, plasma with a density of 10 14 ÷10 16 cm -3 is confined in a 12-meter-long solenoid, which comprises 55 corrugation cells with mirror ratio B max /B min =4.8/3.2 T. The plasma in the solenoid is heated up to 2-4 keV temperature by a high power relativistic electron beam (∼1 MeV, ∼30 kA, ∼8 μs, ∼120 kJ) injected through one of the ends. Mechanism of experimentally observed fast ion heating, issues of plasma stability and confinement are discussed.

A short review of recent results obtained at the GOL-3-II facility is presented. This facility is an open trap with 12 m long plasma column with a longitudinal magnetic field of 4.5 T in the unifor...