Automated mesh production for limiter Wendelstein-7X configuration

A tool for automated mesh production for 3D multifluid plasma transport code Findif is presented. Mesh points for the code lie on magnetic field lines, which, in general, form a complicated tangle. Open field lines that end on solid parts of the machine are the source of difficulties. These lines are usually short and thousands of them are needed. A tool that helps to pick lines for the mesh that is described in this paper is based on calculation the distances of lines already admitted to the mesh and candidate ones. The results of the code run for the limiter configuration (OP-1.1 experimental phase) of the Wendelstein-7X device are shown here. Reasonably even coverage of space by points is achieved.Представлен трёхмерный код Findif для переноса многожидкостной модели плазмы как инструмент автоматизированного производства сетки. Сетка точек для кода лежит на магнитных силовых линиях, которые, вообще говоря, образуют сложную конфигурацию. Открытые силовые линии, которые ограничены твёрдыми частями механизма, являются источником сложностей. Эти линии, как правило, короткие, и нужны тысячи из них. Инструмент, который помогает подобрать линии для сетки, описан в этой статье и основан на вычислении расстояния линий уже допущенных к сетке и кандидатов из них. Представлены результаты прогона кода для конфигурации лимитера (OP-1.1 экспериментальная фаза) стелларатора Wendelstein-7X.Представлено тривимірний код Findif для перенесення багаторідинної моделі плазми як інструмент автоматизованого виробництва сітки. Сітка точок для коду лежить на магнітних силових лініях, які, взагалі кажучи, утворюють складну конфігурацію. Відкриті силові лінії, що обмежені твердими частинами механізма, є джерелом труднощів. Ці лінії, як правило, короткі, і потрібні тисячі з них. Інструмент, який допомагає підібрати лінії для сітки, описаний в цій статті і заснований на обчисленні відстані ліній вже допущених до сітки і кандидатів з них. Представлено результати прогону коду для конфігурації лимитера (OP-1.1 експериментальна фаза) стеларатора Wendelstein-7X

Findif code simulations of OP-1.1 Wendelstein 7-X discharges

The current development state of the finite difference, multi-fluid, 3D plasma code Findif is detailed. The code was run on four meshes prepared for the OP-1.1 wall geometry of the Wendelstein 7-X stellarator. The meshes were produced for 4 magnetic configurations; two of them are finite-beta (non vacuum). The simulated volume covers plasma edge; the computations of limiter heat load distributions were the main goal. Plasma radiation was not taken into account.Докладно наведено поточну стадію розробки кінцево-різницевого тривимірного коду Findif для багаторідинної моделі плазми. Код було запущено на чотирьох сітках, підготовлених для геометрії стінки OP-1.1 стеларатора Wendelstein 7-X. Сітки згенеровано для 4-х магнітних конфігурацій, дві з яких – зі скінченним бета (не вакуум). Змодельований об’єм охоплює край плазми; основна мета полягає в розрахунках розподілів теплових навантажень на лімітер. Випромінювання плазми не враховувалося.Подробно изложена текущая стадия разработки конечно-разностного трехмерного кода Findif для многожидкостной модели плазмы. Код был запущен на четырех сетках, подготовленных для геометрии стенки OP-1.1 стелларатора Wendelstein 7-X. Сетки сгенерированы для 4-х магнитных конфигураций, две из которых – с конечным бета (не вакуум). Смоделированный объем охватывает край плазмы; основная цель заключается в расчетах распределений тепловых нагрузок на лимитер. Излучение плазмы не учитывалось

Magnetic properties of exactly solvable doubly decorated Ising-Heisenberg planar models

Applying the decoration-iteration procedure, we introduce a class of exactly solvable doubly decorated planar models consisting both of the Ising- and Heisenberg-type atoms. Exact solutions for the ground state, phase diagrams and basic physical quantities are derived and discussed. The detailed analysis of the relevant quantities suggests the existence of an interesting quantum antiferromagnetic phase in the system.Comment: 9 pages, 9 figures, submitted to Physical Review

Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution

Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n  =  2 RMP maintaining good confinement ${{H}_{\text{H}\left(98,\text{y}2\right)}}\approx 0.95$ . Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes

A Model of Optical Bistability and Polarisation Evolution in Birefringent χ(2)\text{}^{(2)} Nonlinear Media

We present a model calculation of optical bistability and polarisation evolution in optically birefringent media based on the interaction of three waves. Second-order optical nonlinearity (described by the third rank susceptibility tensor) is assumed to be dominant. A bistable light transmission is analysed in terms of standard Fabry-Perot model of feedback, and is a direct consequence of the results obtained for a semi-infinite medium. A second effect considered in the paper is evolution of polarisation state of the waves involved in these processes. We derived a closed formula for intensity-dependent refractive index, which corresponds to that used in the case of third-order nonlinear media. As a result, we calculated both intensity and Stokes parameters of transmitted light

Aerospace Blockset for Xcos - Open source tool for aerospace systems numerical computation and simulation

Aerospace Blockset for Xcos is a free, open and extendible software tool for aerospace systems simulations. It is a part of the open source Scilab/Xcos simulation environment. It was envisioned as a tool that fills the gap between the free, single-purpose aerospace software (e.g.. Space Trajectory Analysis, etc.), and the very expensive professional tools (eg. AGI-STK, Matalb-Simulink). Aerospace Blockset provides wide capabilities and is available for free even for commercial use

Optical Polarisation Bistability in χ2\text{}^{2} Media at Large Desynchronisation Regime

In this work we present results of calculations concerning bistability of optical polarisation in birefringent media. Second-order optical nonlinearity is assumed to be dominant and represented by one parameter. In our model the second-harmonic generation regime is assumed. Light transmission is analysed in terms of standard Fabry-Perot model of feedback. We derived formulas for the Stokes parameters describing the polarisation state. Numerical results showed that three parameters may exhibit bistable behaviour. This creates new possibilities for optical switching