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The goal of the research is to expand the capabilities of the heavy ion beam probing (HIBP) diagnostic. HIBP is a unique diagnostic, capable to measure plasma potential, density and their fluctuations, as well as the poloidal magnetic field fluctuations in the core and edge plasmas. The sensitivity of the diagnostic is determined by the level of the output signal related to the instrumental noise. The level of the probing beam current should be as high as possible, especially for measurements at the periphery with low output signal due to low plasma density, and in the core, where the beam is attenuated due to the high plasma density. Optimization experiments have shown the possibility of ion beam forming in the current range from 40 to 800 µA.

TJ-II stellarator results on modelling and validation of plasma flow asymmetries due to on-surface potential variations, plasma fuelling physics, Alfvén eigenmodes (AEs) control and stability, the interplay between turbulence and neoclassical (NC) mechanisms and liquid metals are reported. Regarding the validation of the neoclassically predicted potential asymmetries, its impact on the radial electric field along the flux surface has been successfully validated against Doppler reflectometry measurements. Research on the physics and modelling of plasma core fuelling with pellets and tracer encapsulated solid pellet injection has shown that, although post-injection particle radial redistributions can be understood qualitatively from NC mechanisms, turbulence and fluctuations are strongly affected during the ablation process. Advanced analysis tools based on transfer entropy have shown that radial electric fields do not only affect the radial turbulence correlation length but are also capable of reducing the propagation of turbulence from the edge into the scrape-off layer. Direct experimental observation of long range correlated structures show that zonal flow structures are ubiquitous in the whole plasma cross-section in the TJ-II stellarator. Alfvénic activity control strategies using ECRH and ECCD as well as the relation between zonal structures and AEs are reported. Finally, the behaviour of liquid metals exposed to hot and cold plasmas in a capillary porous system container was investigated.

Significant progress has been reported regarding the physics understanding of empirical actuators like Electron Cyclotron Resonance Heating (ECRH) to avoid impurity accumulation, including a reduction of the background density gradient, an increase of turbulent diffusion, amplification of core temperature screening and the development of core plasma potential flux surface asymmetries. Furthermore, it has been shown that radial electric fields does not only affects the radial turbulence correlation length but it is also capable of reducing the propagation of turbulence. Determination of timescales and propagation involved in the influence of ECRH on transport and fluctuations can provide an additional critical test for model validation. We have investigated the influence of ECRH on plasma profiles and edge and core turbulence in the TJ-II stellarator. The machine is equipped with two ECRH beam lines (ECRH1 and ECRH2), delivering 300 kW each at a frequency of 53.2 GHz (X mode). In the present experiments, the ECRH1 power was kept constant whereas the ECRH2 power was modulated on/off. The level of broadband plasma fluctuations is significantly increased from the deep core (rho ≈ 0.3) up to edge (rho ≈ 0.9) as ECRH power increases [Fig.]. The evolution of plasma potential and fluctuations shows two times scales during on/off ECRH modulation experiments: a fast time scale in the order of 100 μs and a longer time transport scale in the range of milliseconds. Cross correlation studies between edge probes and core HIBP signals have shown radial propagation velocities in the order of 104 m/s. The influence of ECRH on the probability distribution function of ExB turbulence transport and radial propagation of plasma turbulence will be addressed [1]. Electron temperature driven instabilities [2] as well as ECRH induced kinetic effects [3] are candidates to explain the observed influence of ECRH on TJ-II fluctuation levels.

2D plasma potential ϕ distribution was measured in the electron cyclotron resonance heating (ECRH) and neutral beam injection (NBI) plasmas of the TJ-II stellarator with the heavy ion beam probe for the whole radial range and wide area of the poloidal angle, and supported by Langmuir probe data at the edge. The whole operation domain for the on-axis ECRH was explored ( n ˉ e = 0.45–0.8 ×1019 m−3, P EC = 220–470 kW), in addition, NBI plasmas with n ˉ e = 0.9–1.3 × 1019 m−3 and P NBI = 510 kW were studied. In ECRH plasmas the density ramp-up is accompanied by the evolution of the potential from the bell-like to the Mexican hat profile, while the density profiles were flat or slightly hollow. The potential has the positive peak at the centre, and LFS-HFS (low field—high field sides) and up-down symmetry. Equipotential lines are consistent with vacuum magnetic flux surfaces. In the high-density NBI scenario, the ϕ profile was fully negative with a minimum up to −300 V at the centre, while at low-density ECRH plasma, ϕ has a maximum up to +0.9 kV at the centre. Fluctuations of potential and density are stronger in low-density scenarios and not poloidally symmetric. At the mid-radius (area of the maximum density), root mean square (RMS) of fluctuations were up to ϕ ∼ 15 V at LFS vs ∼20 V at HFS; RMS n e ∼ 2% at LFS vs ∼3% at HFS. In the NBI plasmas with the density rise, the asymmetry decreases and finally vanishing at n ˉ e = 1.2 × 1019 m−3. 2D distribution of the NBI-induced Alfvén eigenmodes (AEs) shows asymmetric ballooning structure: contrary to broadband turbulence, AE-associated potential perturbation dominates in the LFS with a factor up to 1.7 respect to the HFS. The electrostatic mode, excited in ECRH plasmas by suprathermal electrons also shows asymmetric structures: density perturbation dominates in the top-bottom direction compared to LFS-HFS direction.

This work estimates the degree of turbulent intermittence of the plasma potential measured by a Heavy Ion Beam Probe in the core plasma region of the TJ-II stellarator. It is shown that the intermittence varies in a significant way with the plasma state (ion or electron root). In addition, radial minima of the intermittence are found to be associated with the location of topological structures of the flow associated with some important low-order rational surfaces. The local pressure gradient was also estimated, and a clear correlation was found between the steepening of the pressure gradient and the deepening of the minima of the intermittence, suggesting that the minima are associated with pressure gradient driven modes. By estimating the rotation velocity of the plasma from the measured plasma potential, it was possible to make a rough reconstruction of the twodimensional radial-poloidal map of intermittence, thus clarifying the topological structure of the intermittence. The experimental results were put into context by comparing with simulations performed using a resistive Magneto-Hydrodynamic turbulence model.

2D poloidal contour plots of plasma potential, plasma density, and their fluctuations have been measured in low density plasmas sustained by Electron Cyclotron Resonance Heating using a heavy ion beam probe (HIBP) system in the TJ-II stellarator. A HIBP has been used in the new energy scanning mode to obtain the measurements for a 2D poloidal cross section of the stellarator. The 2D map for the absolute plasma potential shows a local maximum in the plasma core as expected in low density plasma scenarios. Fluctuations in the HIBP secondary ion current, as a proxy of plasma density fluctuations, appear both in positive and negative density gradient regions, with a normalized level of density fluctuations higher in the negative density gradient region. The TJ-II innovative experimental setup developed using a dual HIBP diagnostic paves the way for model validation on core plasma potential asymmetries and particle transport and fluctuations under positive and negative density gradient scenarios.

The main results obtained in the TJ-II stellarator in the last two years are reported. The most important topics investigated have been modelling and validation of impurity transport, validation of gyrokinetic simulations, turbulence characterisation, effect of magnetic configuration on transport, fuelling with pellet injection, fast particles and liquid metal plasma facing components. As regards impurity transport research, a number of working lines exploring several recently discovered effects have been developed: the effect of tangential drifts on stellarator neoclassical transport, the impurity flux driven by electric fields tangent to magnetic surfaces and attempts of experimental validation with Doppler reflectometry of the variation of the radial electric field on the flux surface. Concerning gyrokinetic simulations, two validation activities have been performed, the comparison with measurements of zonal flow relaxation in pellet-induced fast transients and the comparison with experimental poloidal variation of fluctuations amplitude. The impact of radial electric fields on turbulence spreading in the edge and scrape-off layer has been also experimentally characterized using a 2D Langmuir probe array. Another remarkable piece of work has been the investigation of the radial propagation of small temperature perturbations using transfer entropy. Research on the physics and modelling of plasma core fuelling with pellet and tracer-encapsulated solid-pellet injection has produced also relevant results. Neutral beam injection driven Alfvénic activity and its possible control by electron cyclotron current drive has been examined as well in TJ-II. Finally, recent results on alternative plasma facing components based on liquid metals are also presented., Nuclear Fusion, 59 (11), ISSN:0029-5515, ISSN:1741-4326

The effects of 3D geometry are explored in TJ-II from two relevant points of view: neoclassical transport and modification of stability and dispersion relation of waves. Particle fuelling and impurity transport are studied considering the 3D transport properties, paying attention to both neoclassical transport and other possible mechanisms. The effects of the 3D magnetic topology on stability, confinement and Alfvén Eigenmodes properties are also explored, showing the possibility of controlling Alfvén modes by modifying the configuration; the onset of modes similar to geodesic acoustic modes are driven by fast electrons or fast ions; and the weak effect of magnetic well on confinement. Finally, we show innovative power exhaust scenarios using liquid metals.

Measurements of the relaxation of a zonal electrostatic potential perturbation in a non-axisymmetric magnetically confined plasma are presented. A sudden perturbation of the plasma equilibrium is induced by the injection of a cryogenic hydrogen pellet in the TJ-II stellarator, which is observed to be followed by a damped oscillation in the electrostatic potential. The waveform of the relaxation is consistent with theoretical calculations of zonal potential relaxation in a non-axisymmetric magnetic geometry. The turbulent transport properties of a magnetic confinement configuration are expected to depend on the features of the collisionless damping of zonal flows, of which the present letter is the first direct observation.

The heavy ion beam probe diagnostic is used in the TJ-II stellarator to study directly the plasma electric potential with good spatial (up to 1 cm) and temporal (up to 2 μs) resolution. Singly charged heavy ions, Cs + , with energies of up to 125 keV are used to probe the plasma column from the edge to the core. Both electron cyclotron resonance heating (ECRH) and neutral beam injection (NBI)-heated plasmas (P ECRH = 200 to 400 kW, P NBI = 200 to 400 kW, E NBI = 28 keV) have been studied. Low-density ECRH [n = (0.5 to 1.1) X 10 19 m -3 ] plasmas in TJ-II are characterized by positive plasma potential on the order of 1000 to 400 V. A negative electric potential appears at the edge when the line-averaged density exceeds 0.5 X 10 19 m -3 . Further density rises are accompanied by a decrease in the core plasma potential, which becomes fully negative for plasma densities n ≥ 1.5 X 10 19 m -3 . The NBI plasmas are characterized by a negative electric potential across the whole plasma cross section from the core to the edge. In this case, the absolute value of the central potential is on the order of -500 V. These results show a clear link between plasma potential and density in the TJ-II stellarator.

The link between edge sheared flows and turbulence is investigated in the plasma edge region of the TJ-II stellarator and the results are compared with results in other devices like JET tokamak. In the TJ-II stellarator there is a threshold density to trigger the development of edge shear flows. During sheared flow development the degree of turbulence anisotropy ((v ∥ v r )) is modified. The fact that different quadratic terms in fluctuating velocities ((v ∥ v r ) and (v ⊥ v r )) change during edge sheared flow generation means that shear flow physics involves 3D physics phenomena in which both perpendicular and parallel dynamics are involved. A new strategy has been recently applied to plasma physics to quantify the local energy transfer between flows and turbulence by computing the production term. Experimental results show that turbulence can act as an energy sink and energy source for the mean flow near the shear layer. Measurements of the turbulence production show the importance of 3D effects on the energy transfer between flows and turbulence.

The evolution of core quasi-coherent modes has been investigated during the formation of electron internal transport barriers (e-ITB) in the TJ-II stellarator. These modes have been characterized using heavy ion beam probe and electron cyclotron emission diagnostics. The quasi-coherent mode evolves during formation/annihilation of the e-ITB and vanishes as the transport barrier is fully developed. These observations can be interpreted in terms of the influence of sheared flows in the stability of quasi-coherent modes.

This paper describes a series of experiments performed in TJ-II stellarator with the aim of studying the influence of magnetic configuration on stability and transport properties of TJ-II plasmas. Plasma potential profiles have been measured in several configurations up to the plasma core with the heavy ion beam probe diagnostic. Low-order rational surfaces have been positioned at different plasma radii observing the effect on transport features. Plasma edge turbulent transport has been studied in configurations that are marginally stable due to decreased magnetic well. Results show a dynamical coupling between gradients and turbulent transport. Experiments on the influence of magnetic shear on confinement are reported. Global confinement issues as well as enhanced confinement regimes found in TJ-II are discussed as well.

The injection systems of heavy ion beam probe (HIBP) and beam emission spectroscopy plasma diagnostics must produce a beam with a high enough intensity to obtain a reliable secondary signal. In particular, it can be achieved by improvements and optimization of the ion sources. Among a variety of them, the sources with solid-state thermoionic emitters have strong advantages in simplicity and very small (0.1–1 eV) initial energy dispersion. High intensity alkali ion sources with solid-state thermoionic emitters of Li+, Na+, K+, Cs+, and Tl+ have been developed and investigated in IPP NSC “KIPT,” Kharkov, Ukraine. In a steady mode of operation the current densities up to 6 mA/cm2 are obtained with an emitter capacity up to 9 mA/h. With no significant design modifications, these ion sources are used on currently operating injectors of HIBP diagnostics on the TJ-II stellarator (Spain), tokamaks T-10, TUMAN-3M (Russia), and ISTTOK (Portugal), and the injector of the BES diagnostic on ASDEX-U tokamak (Germany).

This article presents long-focus ion beam injection systems developed for investigation of plasma parameters by heavy ion beam probing diagnostics in fusion devices. Ion beam parameters vary in a wide range of both beam intensity of alkali probing ions (1–100 μA) and initial energy (20–300 keV), determined by the experimental claims on each plasma device under study. This article describes the characteristics of beam extraction systems with transport ion optics and control, and accelerator power supplies with high stability (not worse than 10−5). Presented systems allow us a fine tuning of the beam focusing along the beam trajectory in plasmas studied. They provide an accurate spatial resolution of measurements in plasma of modern fusion devices up to 5 mm.

This work deals with the results on flow dynamics in TJ-II plasmas under Li-coated wall conditions, which produces low recycling and facilitates the density control and access to improved confinement transitions. The low-density transition, characterized by the emergence of the shear flow layer, is described from first principles and within the framework of neoclassical theory. The vanishing of the neoclassical viscosity when approaching the transition from below explains the observation of a number of turbulent phenomena reported in TJ-II in recent years; a unifying picture is provided in which zonal, i.e. large scale, radially structured, perturbations are observable when the neoclassical damping is sufficiently small. Preliminary linear, collisionless gyrokinetic simulations are carried out to assess that the measured time scale of relaxation of such perturbations is reasonably understood theoretically. In higher density regimes, the physical mechanisms behind the L–H transition have been experimentally studied. The spatial, temporal and spectral structure of the interaction between turbulence and flows has been studied close to the L–H transition threshold conditions. The temporal dynamics of the turbulence-flow interaction displays a predator–prey relationship and both radial outward and inward propagation velocities of the turbulence-flow front have been measured. Finally, a non-linear relation between turbulent fluxes and gradients is observed.

In European legal science a traditional division of the parliamentarian’s representative mandate into two types currently prevails: a free and imperative mandate. The type of a mandate determines the character of coop-eration of an elected representative with his electorate. The author of the article analyzed the key points of those concepts in Republic of Belarus and in some states of EU in comparative feature. The conclusion is made that the gradual transition to the normative regulation of the Chamber of representatives’ deputy status, the member of Republic Council, promoting the establishment of mixed type of parliamentarian’s mandate in Republic of Belarus is preferable. A number of progressive characteristics of the mixed type of mandate the parliamentarians are stated.

The development of light ion injector and neutralizer for the BES plasma diagnostic system and its first experimental results are presented in this work. This injector will be used for neutral beam plasma diagnostic systems. Diagnostic systems based on neutral beams of Li or Na atoms can be used to study the spatial plasma density profiles, impurity ions and magnetic field distribution in the border region of the plasma fusion devices. This method is based on the detection of the probe beam glow of atoms excited by the plasma electrons. These diagnostic systems consist of two main parts – the neutral beam injector (including the ion beam accelerator and neutralizer) and the secondary light signal registration system. Light ion beam accelerator based on the five-electrode ion-optical system, in contrast to the classical three-electrode system, delivers beams of lithium or sodium with current 3…5 mA at a beam energy 20…25 keV. The neutralizer is based on the supersonic jet of sodium vapor formed by Laval nozzle. The first experiments of neutralizing the ion beam with a transverse supersonic atomic jet was done. Представлена разработка инжектора легких ионов и нейтрализатора для ПЭС-системы диагностики плазмы и первые экспериментальные результаты. Этот инжектор будет использован для диагностики плазмы с помощью пучка нейтральных атомов. Диагностические системы, основанные на нейтральных пучках атомов Li или Na, могут быть использованы для исследования пространственных профилей плотности плазмы, примесей ионов и распределения магнитного поля в пограничных областях плазмы термоядерных установок. Этот метод основан на регистрации свечения атомов зондирующего пучка, возбуждаемых электронами плазмы. Эти диагностические системы состоят из двух основных частей: инжектора нейтральных атомов (включающего ускоритель пучка ионов и нейтрализатор) и системы регистрации излучения. Ускоритель легких ионов, базирующийся на пятиэлектродной ионно-оптической системе, в отличие от классической трехэлектродной, позволяет получать пучки ионов лития или натрия с током 3…5 мА при энергии пучка 20…25 кэВ. Нейтрализатор основан на сверхзвуковой струе паров натрия, формируемой с помощью сопла Лаваля. Проведены первые эксперименты по нейтрализации пучка ионов с помощью поперечной сверхзвуковой струи. Представлена розробка інжектора легких іонів і нейтралізатора для системи ПЕС діагностики плазми та перші експериментальні результати. Цей інжектор буде використаний для діагностики плазми за допомогою пучка нейтральних атомів. Діагностичні системи, засновані на нейтральних пучках атомів Li або Na, можуть бути використані для дослідження просторових профілів густини плазми, домішкових іонів і розподілу магнітного поля в приграничних областях плазми термоядерних установок. Цей метод заснований на реєстрації світіння атомів зондуючого пучка, збуджуваних електронами плазми. Ці діагностичні системи складаються з двох основних частин: інжектора нейтральних атомів (що включає прискорювач пучка іонів і нейтралізатор) та системи реєстрації випромінювання. Прискорювач легких іонів, який базується на п’ятиелектродній іонно-оптичній системі, на відміну від класичної трьохелектродної, дозволяє отримувати пучки іонів літію або натрію зі струмом 3…5 мА при енергії пучка 20…25 кеВ. Нейтралізатор заснований на надзвуковому струмені пари натрію, формованої за допомогою сопла Лаваля. Проведені перші експерименти з нейтралізації пучка іонів за допомогою поперечного надзвукового струменя.

TJ-II stellarator by HIBP diagnostics has been performed. The following similar features of potential were found: the scale of several hundred Volts; the negative sign for densities ne>1×10¹⁹ m⁻³ and comparable values in spite of the different heating methods. When ne or tE rises, the potential evolves to negative values. During ECR heating and associated Te rise, tE degrades and the potential evolves to positive direction. Oscillations of potential and density in the range of Geodesic Acoustic Modes in T-10 and Alfvén Eigenmodes in TJ-II were observed. На токамаці Т-10 і стелараторі TJ-II за допомогою пучка важких іонів в порівняних режимах досліджувалася поведінка потенціалу та його флуктуацій. Виявлені спільні властивості потенціалу: масштаб близько сотен вольт;негативний знак при щільності ne>1×10¹⁹ m⁻³ і порівнянні значення, незважаючи на різні методи нагріву. Коли n_е або t_Е зростають, потенціал зростае у негативну область. При ЕЦР-нагріві і відповідному рості Te, t_Е погіршується, і потенціал змінюється у позитивний бік. Спостерігається коливання потенціалу в діапазоні геодезичних акустичних мод у Т-10 та альфвеновських власних мод у TJ-II На токамаке Т-10 и стеллараторе TJ-II с помощью пучка тяжелых ионов в сравнимых режимах исследовалось поведение потенциала и его флуктуаций. Обнаружены общие свойства потенциала: масштаб порядка сотен вольт; отрицательный знак при плотностях n_е>1×10¹⁹ m⁻³ и сравнимые значения, несмотря на разные методы нагрева. Когда n_е или t_Е растут, потенциал растет в отрицательную область. При ЭЦР-нагреве и соответствующем росте Te, t_Е ухудшается, и потенциал меняется в положительную сторону. Наблюдались колебания потенциала в диапазоне геодезических акустических мод в Т-10 и альфвеновских собственных мод в TJ-II

The testing and first operations of the Heavy Ion Beam Probe (HIBP) plasma diagnostic injectors for stellarator Uragan-2M and TJ-ІІ is presented in this work. The increasing of plasma density in modern fusion devices up to (3...7)×10^19m^-3 (TJ-ІІ and T-10) leads to huge probing ion beam absorption in central plasma area. One way to obtain the HIBP information from plasma centre is the increasing of primary ion beam current. A new modification of HIBP injectors for TJ-ІІ and Uragan 2M stellarators was developed and tested in IPP NSC KIPT with energy up to 100 keV and ion current up to 300 μA.

[1] Calculations of the Doppler shift of the frequency (DSF) of a UHF signal under given models of a wave disturbance (WD), undisturbed medium, and particular orbits of low-orbiting (LO) satellites showed that there is an angle-of-approach effect. On the basis of the angle-of-approach effect a method of estimation of model parameters of medium-scale WD on the basis of measurements of DSF of signals from LO satellites in one observation point is developed. A trend in DSF variations is detected in the initial time series. Using this trend, the global model of the undisturbed ionosphere is corrected. For the parameters estimation, calculated trajectory parameters of the satellite and recordings of DSF variations are used. The numerical experiment carried out demonstrates the efficiency of the method developed. The method was tested at a series of DSF registrations received from LO satellites of the Tsykada type in 2002–2004. The analysis of DSF registrations showed that at high zenith angles for the orbits close to the central ones, WD disturbances with a vertical component are often observed. In such cases, the vertical wavelength can reach 140 km. For horizontal WD, the estimates of the wavelength give values >100 km. The range of variations of the maximum relative disturbance of the electron concentration is 1–7%.

The heavy ion beam probe (HIBP) is an established non perturbing diagnostic for measuring the spatial distributions of plasma potential, density, temperature and poloidal magnetic field (axial current) of magnetically confined fusion plasma. These are determined from the change in the primary ion beam parameters (charge, intensity and trajectory) passing through a plasma volume due to collisions with electrons and interactions with the confining magnetic field. A heavy ion beam probe plasma diagnostic system has been installed and tested on the WEGA stellarator in Greifswald, Germany in 2006–2007. The WEGA HIBP operates with a beam of singly charged sodium ions with an energy of up to 60 keV, ion current up to 100 μA, and beam diameter of 5–6 mm in the confined plasma region. Plasma experiments with the HIBP diagnostic system were carried out at a magnetic field strength of B0 = 0.489 T. In the experiments, an argon plasma was heated with ECRH at 28 GHz. In this work the first plasma potential and total c...

This work presents the results of the design study, investigations of the features and a calibration of double-slit ion energy analyzer prototype at the test-bench in IPP NSC KIPT, Kharkov, Ukraine, with beam energy up to 10 keV. Hitherto obtained accuracy for both analyzer slits is ΔG−2×10−3 and ΔF−3×10−3, which is limited by the existing step motor accuracy 0.1 mm for entrance slits moving. The presented study work is considered as the first step to the multi-slit analyzer elaboration.

The applicability of the HIBP diagnostics for the URAGAN-2M stellarator is described in this article. It is possible to use such diagnostics for local plasma electric field potential measurements. The necessary voltages on the primary ion beam accelerator, energy analyzer and deflecting plates are acceptable.

A conceptual design for a heavy ion beam probe diagnostic for the stellarator WEGA in Greifswald (Germany) is developed to provide measurements of the radial profiles of the electric plasma potential, density, and their fluctuations. Calculations of probing Na + beam trajectories were done for the various WEGA diagnostics ports with B 0 from 0.087 to 0.5 T. They show that satisfactory access may be possible for C+ C- port combinations.