Initial stage of interaction between gyrating relativistic electron beam and long-wavelength electromagnetic surface waves in cylindrical metallic waveguides partially filled with plasma

Azimuthal surface waves are eigen electromagnetic waves of cylindrical metallic waveguides with plasma filling. Azimuthal surface waves of extraordinary polarization are known to be effectively excited by a beam of electrons gyrating in an axial external static magnetic field along large Larmor radii around the plasma column. Beam excitation of azimuthal surface waves was well studied theoretically in both linear and nonlinear approaches. An important limitation of the earlier studies was the approximation of zero axial wavenumber. In the present paper, perturbation theory is applied to account for finite magnitude of the axial wavenumber of electromagnetic surface waves in studying their excitation by an electron beam. The dependence of the wave growth rate on the axial wavenumber and parameters of the plasma waveguide is studied. The results obtained in this paper are of interest for application in plasma electronics

Drift resonance and particle removal from helical plasma

The effect of magnetic field perturbation on motion of deuterium, tritium and helium ions is studied theoretically and by numerical simulation of the charged particle motion in electromagnetic field. A method for alpha-particles (fusion reaction product) removal from plasma in helical device due to drift resonance formation is proposed. The point is that helium ion escapes from the confinement volume due to the natural drift in inhomogeneous magnetic field.Теоретически и с помощью численного моделирования движения заряженных частиц в электромагнитном поле изучено влияние возмущения магнитного поля на движение ионов дейтерия, трития и гелия. Предложен метод удаления альфа-частиц (продуктов реакции синтеза) из плазмы винтовой ловушки с помощью формирования дрейфового острова. Основной особенностью является то, что ион гелия уходит из объёма удержания благодаря естественному дрейфу в неоднородном магнитном поле.Теоретично та за допомогою числового моделювання руху заряджених частинок в електромагнітному полі вивчено вплив збурення магнітного поля на рух іонів дейтерію, тритію та гелію. Запропоновано метод видалення альфа-частинок (продуктів реакції синтезу) з плазми гвинтового пристрою за допомогою формування дрейфового острова. Головною особливістю є те, що іон гелію виходить з об’єму утримання завдяки природньому дрейфу в неоднорідному магнітному полі

Electromagnetic surface wave excitation and energy transport along a plane plasma boundary

A simple construction for excitation of Surface Wave (SW) in plasmas is proposed. The metal plate is used both as an antenna with surface current and as a wall of the waveguide structure. Second wall of the waveguide structure is a plasma boundary. Electromagnetic wave which is incident on plasma surface initiates the plasma oscillations which form an electromagnetic field of surface type in plasma if the characteristics of the incident field (wave frequency and wave vector direction) are chosen properly. It is shown that SWs can exist in high and low frequency ranges. The SW from high frequency range can have large penetration depth into plasma and large power flux along plasma surface inside plasma. The SW from low frequency range can have large tangential electric field on plasma surface. The paper answers the questions which geometry and surface current have to be chosen to see the SW in the structure with the preferable characteristics.Запропоновано просту конструкцію для збудження поверхневої хвилі (ПХ) у плазмі. Металеву пластину використано одночасно як антену з поверхневим струмом та як стінку хвилеводної структури. Другою стінкою хвилеводної структури є поверхня плазми. Електромагнітна хвиля, яка падає на поверхню плазми, ініціює плазмові коливання, які формують у плазмі електромагнітне поле поверхневого типу, якщо характеристики поля, що падає на плазму (частота та напрямок хвильового вектора), підібрані належним чином. Показано, що ПХ можуть існувати у високочастотному та низькочастотному діапазонах. ПХ з високочастотного діапазону можуть мати велику глибину проникнення до плазми та великий потік енергії уздовж поверхні в самій плазмі. ПХ з низькочастотного діапазону можуть мати велике тангенційне електричне поле на поверхні плазми. Робота відповідає на питання оптимального вибору геометрії задачі та поверхневого струму для спостерігання в структурі ПХ з бажаними характеристиками.Предложена простая конструкция для возбуждения поверхностной волны (ПВ) в плазме. Металлическая пластина использована одновременно как антенна с поверхностным током и как стенка волноводной структуры. Второй стенкой волноводной структуры является поверхность плазмы. Электромагнитная волна, которая падает на поверхность плазмы, инициирует плазменные колебания, которые формируют в плазме электромагнитное поле поверхностного типа, если характеристики падающего поля (частота и направление волнового вектора) подобраны нужным образом. Показано, что ПВ могут существовать в высокочастотном и низкочастотном диапазонах. ПВ из высокочастотного диапазона могут иметь большую глубину проникновения в плазму и большой поток энергии вдоль поверхности внутри плазмы. ПВ из низкочастотного диапазона могут иметь большое тангенциальное электрическое поле на поверхности плазмы. Работа отвечает на вопросы оптимального выбора геометрии задачи и поверхностного тока для наблюдения в структуре ПВ с предпочтительными характеристиками

Extraction of fusion relevant ion species from discharge of focused anode layer thruster

The modification of anode layer thruster, which utilizes the focusing with reversed magnetic field (FALCON ion source), has been investigated for operation with H, He and Ar working gases. Current efficiency was measured to be in the range of 30…40% for H and Ar ion beam, while for He gas it varies from 10 to 20%.Досліджувалася модифікація прискорювача з анодним шаром з використанням фокусування реверсивним магнітним полем (іонне джерело FALCON) для застосування з воднем, гелієм та аргоном в якості робочих газів. Струм легких іонів не перевищував 12 мА, в той час як струм іонного пучка аргону сягав 25…65 мА. Виміряна струмова ефективність була в діапазоні 30...40% для водню та аргону, 10…20% для гелію.Исследовалась модификация ускорителя с анодным слоем с использованием фокусировки реверсивным магнитным полем (ионный источник FALCON) для применения с рабочими газами водородом, гелием и аргоном. Ток легких ионов не превышал 12 мА, в то время как ток ионного пучка аргона достигал 25…65 мА. Измеренная токовая эффективность находилась в диапазоне 30...40% для водорода и аргона, 10…20% для гелия

BREMSSTRAHLUNG FORMATION IN THE DUAL ENERGY METHOD FOR RADIOGRAPHY OF THE UNAUTHORIZED EMBEDDING

The possibility of an effective method of dual-energy radiography unauthorized inclusions containing heavy elements in cargo containers has been investigated. A method for optimizing the energy performance of the bremsstrahlung radiation: low-energy beam (containing the maximum number of photons in the energy range, which is dominated by Compton effect) and high energy beam (with a maximum number of high-energy photons, electron-positron pairs) has been developed. The influence of the converter thickness and converter material on the spectral characteristics of the beams of photons has been investigated. The variants of treelayers efficient converters have been proposed. On the basis of the Monte Carlo and quasi-analytical method a numerical experiment radiography investments has been completed. It is shown that the use of optimally shaped beams can reliably distinguish embedding from lead to masking the background of steel structures up to 25 c

Overview of ASDEX upgrade results in view of ITER and DEMO

Experiments on ASDEX Upgrade (AUG) in 2021 and 2022 have addressed a number of critical issues for ITER and EU DEMO. A major objective of the AUG programme is to shed light on the underlying physics of confinement, stability, and plasma exhaust in order to allow reliable extrapolation of results obtained on present day machines to these reactor-grade devices. Concerning pedestal physics, the mitigation of edge localised modes (ELMs) using resonant magnetic perturbations (RMPs) was found to be consistent with a reduction of the linear peeling-ballooning stability threshold due to the helical deformation of the plasma. Conversely, ELM suppression by RMPs is ascribed to an increased pedestal transport that keeps the plasma away from this boundary. Candidates for this increased transport are locally enhanced turbulence and a locked magnetic island in the pedestal. The enhanced D-alpha (EDA) and quasi-continuous exhaust (QCE) regimes have been established as promising ELM-free scenarios. Here, the pressure gradient at the foot of the H-mode pedestal is reduced by a quasi-coherent mode, consistent with violation of the high-n ballooning mode stability limit there. This is suggestive that the EDA and QCE regimes have a common underlying physics origin. In the area of transport physics, full radius models for both L- and H-modes have been developed. These models predict energy confinement in AUG better than the commonly used global scaling laws, representing a large step towards the goal of predictive capability. A new momentum transport analysis framework has been developed that provides access to the intrinsic torque in the plasma core. In the field of exhaust, the X-Point Radiator (XPR), a cold and dense plasma region on closed flux surfaces close to the X-point, was described by an analytical model that provides an understanding of its formation as well as its stability, i.e., the conditions under which it transitions into a deleterious MARFE with the potential to result in a disruptive termination. With the XPR close to the divertor target, a new detached divertor concept, the compact radiative divertor, was developed. Here, the exhaust power is radiated before reaching the target, allowing close proximity of the X-point to the target. No limitations by the shallow field line angle due to the large flux expansion were observed, and sufficient compression of neutral density was demonstrated. With respect to the pumping of non-recycling impurities, the divertor enrichment was found to mainly depend on the ionisation energy of the impurity under consideration. In the area of MHD physics, analysis of the hot plasma core motion in sawtooth crashes showed good agreement with nonlinear 2-fluid simulations. This indicates that the fast reconnection observed in these events is adequately described including the pressure gradient and the electron inertia in the parallel Ohm’s law. Concerning disruption physics, a shattered pellet injection system was installed in collaboration with the ITER International Organisation. Thanks to the ability to vary the shard size distribution independently of the injection velocity, as well as its impurity admixture, it was possible to tailor the current quench rate, which is an important requirement for future large devices such as ITER. Progress was also made modelling the force reduction of VDEs induced by massive gas injection on AUG. The H-mode density limit was characterised in terms of safe operational space with a newly developed active feedback control method that allowed the stability boundary to be probed several times within a single discharge without inducing a disruptive termination. Regarding integrated operation scenarios, the role of density peaking in the confinement of the ITER baseline scenario (high plasma current) was clarified. The usual energy confinement scaling ITER98(p,y) does not capture this effect, but the more recent H20 scaling does, highlighting again the importance of developing adequate physics based models. Advanced tokamak scenarios, aiming at large non-inductive current fraction due to non-standard profiles of the safety factor in combination with high normalised plasma pressure were studied with a focus on their access conditions. A method to guide the approach of the targeted safety factor profiles was developed, and the conditions for achieving good confinement were clarified. Based on this, two types of advanced scenarios (‘hybrid’ and ‘elevated’ q-profile) were established on AUG and characterised concerning their plasma performance