A seemingly simple task: Filling a solenoid volume in vacuum with dense plasma

Space-charge neutralization of a pulsed, high-current ion beam is required to compress and focus the beam on a target for warm dense matter physics or heavy ion fusion experiments. We described attempts to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary charge-compensating electrons. Among the options are plasma injection from four pulsed vacuum arc sources located outside the solenoid, and using a high current (> 4 kA) pulsed vacuum arc plasma from a ring cathode near the edge of the solenoid. The plasma distribution is characterized by photographic means and by an array of movable Langmuir probes. The plasma is produced at several cathode spots distributed azimuthally on the ring cathode. Beam neutralization and compression are accomplished, though issues of density, uniformity, and pulse-to-pulse reproducibly remain to be solved

Innovative Vacuum Arc Thruster for CubeSat Constellations

Abstract: The University of the Federal Armed Forces (UniBwM) is currently developing an innovative electric propulsion system for small satellites with extremly low space, mass and power budget. Satellites with these characteristics were built by the JustusMaximilians-Universität Würzburg (JMUW) within the international CubeSat project. the Bavarian government UniBwM and JMUW are working together to equip the new pico satellite UWE-4 (Universität Würzburg Experimentalsatellit 4) with a sufficient propulsion system for fine positioning and attitude control. JMUW is responsible for the development of the satellite and the integration of the propulsion system which is currently under development at UniBwM based on the so called Vacuum Arc Thruster. To demonstrate the positioning ability of the system the mission of UWE-4 is to chase another CubeSat and to hold its relative position. Together with the strict restrictions of the CubeSat this gives some serious challenges to be solved

Інформаційна технологія для класифікації наукових текстів на основі методу модифікованої логістичної регресії

Об’єкт дослідження: процес класифікації наукових текстів та практичне використання технологій обробки природної мови в освітніх додатках, з метою підвищення ефективності освітнього процесу. Предмет дослідження: методи, моделі машинного навчання та обробки природньої мови у задачах класифікації наукових текстів. Мета магістерської роботи: вдосконалення та пришвидшення процесу класифікації текстів з допомогою моделі логістичної регресії, з метою застосування її у освітніх додатках для покращення освітнього процесу. Методи дослідження. Для створення рекомендаційного та навчального асистента були використані засоби та методи машинного навчання, теорії множин, лінейної алгебри й обробки природної мови. Наукова новизна полягає у тому, що вдосконалено та розширено можливості методу логістичної регресії на основі комбінування його з методом ранжування, що в результаті дозволило використати метод логістичної регресії для навчального асистенті. Практична цінність полягає у тому, що в результаті роботи, було створено прототип навчального асистента, що використовує скомбіновану з методом ранжування модель логістичної регресії для класифікації текстів. Використані методи та підходи у прототипі можуть застосовуватись як при розробці «інтелектуальних» навчальних систем, так й в практиці викладання дисциплін, пов’язаних з обробкою природної мови

Hollow Plasma in a Solenoid

A ring cathode for a pulsed, high-current, multi-spot cathodic arc discharge was placed inside a pulsed magnetic solenoid. Photography is used to evaluate the plasma distribution. The plasma appears hollow for cathode positions close the center of the solenoid, and it is guided closer to the axis when the cathode is away from the center

Dense Metal Plasma in a Solenoid for Ion Beam Neutralization

Space-charge neutralization is required to compress and focus a pulsed, high-current ion beam on a target for warm dense matter physics or heavy ion fusion experiments. We described approaches to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary space-charge compensating electrons. Among the options are plasma injection from pulsed vacuum arc sources located outside the solenoid, and using a high current (> 4 kA) pulsed vacuum arc plasma from a ring cathode near the edge of the solenoid. The plasma distribution is characterized by photographic means, by an array of movable Langmuir probes, by a small single probe, and by evaluating Stark broadening of the Balmer H beta spectral line. In the main approach described here, the plasma is produced at several cathode spots distributed azimuthally on the ring cathode. It is shown that the plasma is essentially hollow, as determined by the structure of the magnetic field, though the plasma density exceeds 1014 cm-3 in practically all zones of the solenoid volume if the ring electrode is placed a few centimeters off the center of the solenoid. The plasma is non-uniform and fluctuating, however, since its density exceeds the ion beam density it is believed that this approach could provide a practical solution to the space charge neutralization challenge

Vacuum Arc Plasma Coating for Polymer Surface Protection— A Plasma Enhanced In-Orbit Additive Manufacturing Concept

In-orbit additive manufacturing (AM) is a promising approach for fabrication of large structures. It allows to expand and accelerate human space exploration possibilities. Extrusion-based AM was demonstrated in zero gravity, while the realization of such a process in orbit-like vacuum conditions is currently under exploration. Still, a solution for protection of the UV and IR radiation sensitive polymers is needed in order to prevent their early mechanical failure under space conditions. Vacuum arc plasma based process is widely applied on earth for thin protective coating deposition. Its major advantage is its scalability—from tiny size used in electric propulsion to large scale coating devices. The usability of the vacuum arc process in space conditions was shown in electric propulsion applications in nano-satellites. In this work we discuss and demonstrate the integration of vacuum arc process as a post processing step after Fused Filament Fabrication (FFF) for additive manufacturing and functionalization of long polymer structures. Here we address the concept for technical realization, which integrates the vacuum arc into additive manufacturing process chain. More over we present a laboratory prototype, which implements this concept together with a use case, where a previously printed PEEK structure is coated with aluminum based coating suitable for UV radiation protection

Endothelialization and characterization of titanium dioxide-coated gas-exchange membranes for application in the bioartificial lung

Fouling on the gas-exchange hollow-fiber membrane (HFM) of extracorporeal membrane oxygenation (ECMO) devices by blood components and pathogens represents the major hurdle to their long-term application in patients with lung deficiency or unstable hemodynamics. Although patients are treated with anticoagulants, deposition of blood proteins onto the membrane surface may still occur after few days, leading to insufficient gas transfer and, consequently, to device failure. The aim of this study was to establish an endothelial cell (EC) monolayer onto the gas-exchange membrane of an ECMO device with a view to developing a hemocompatible bioartificial lung. Poly(4-methyl-1-pentene) (PMP) gas-exchange membranes were coated with titanium dioxide (TiO2), using the pulsed vacuum cathodic arc plasma deposition (PVCAPD) technique, in order to generate a stable interlayer, enabling cell adhesion onto the strongly hydrophobic PMP membrane. The TiO2 coating reduced the oxygen transfer rate (OTR) of the membrane by 22%, and it successfully mediated EC attachment. The adhered ECs formed a confluent monolayer, which retained a non-thrombogenic state and showed cell-to-cell, as well as cell-to-substrate contacts. The established monolayer was able to withstand physiological shear stress and possessed a ‘‘self-healing” capacity at areas of induced monolayer disruption. The study demonstrated that the TiO2 coating mediated EC attachment and the establishment of a functional EC monolayer