Halbach Magnets for Magnetic Resonance

This review is a compilation of relevant concepts in designing Halbach multipoles for magnetic resonance applications. The main focus is on providing practical guidelines to plan, design and build such magnets. Therefore, analytical equations are presented for estimating the magnetic field from ideal to realistic systems. Various strategies of homogenizing magnetic fields are discussed together with concepts of opening such magnets without force, or combining them for variable fields. Temperature compensation and other practical aspects are also reviewed. For magnetic resonance two polarities (di- and quadrupole) are of main interest, but higher polarities are also included.Comment: 37 pages, 17 Figure

Ultrasensitive 3He magnetometer for measurements of high magnetic fields

We describe a 3He magnetometer capable to measure high magnetic fields (B > 0.1 Tesla) with a relative accuracy of better than 10^-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2* being of order minutes which is achieved for spherical sample cells in the regime of motional narrowing where the disturbing influence of field inhomogeneities is strongly suppressed. The 3He gas is spin polarized in-situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T2* further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10^-4.Comment: 27 pages, 7 figure

Анализ электрической части Беловской ГРЭС и релейная защита блока генератор-трансформатор

Выпускная квалификационная работа 118 с., 24 рис., 21 табл., 17 источников, 6 прил. Объектом исследования является Беловская ГРЭС. Цель работы заключается в анализе электрической части Беловской ГРЭС (анализ структурной схемы, характеристики оборудования, расчет баланса мощностей и т.д.) и расчете релейной защиты блока генератор – двухобмоточный трансформатор. Для достижения поставленной цели использованы расчетные и графоаналитические методы, вычислительные расчетные комплексы CTCURR, программа для расчета продолжительных режимов электростанции «Исследование структурных схем КЭС с автотрансформаторами связи», пакеты программ Mathcad, Excel, графический редактор MS Visio. В процессе исследования проводились анализы продолжительных режимов электростанции и расчет токов коротких замыканий.Final qualifying work 118 p., 24 fig., 21 tab., 17 sources, 6 adj. The object of this study is to Belovo TPP. The purpose of work is to analyze the electrical Belovskaya GRES (analysis of structural scheme, the characteristics of the equipment, capacity balancing, etc.) and the calculation of relay protection unit generator - two-winding transformer. To achieve this goal and estimates used graphoanalitical method, computer systems design CTCURR, a program for calculating the continuous duty power "Research of structural schemes IES with autotransformers connection" packages Mathcad software, Excel, MS Visio editing. The study carried out extensive analyzes of power modes and calculation of short circuit currents

Возможности применения лазерной сварки для низкоуглеродистой промышленной стали X80

Объектом исследования является стали категории прочности Х80 после контролируемой продольной прокатки с окончанием прокатки в (?+?) – области и последующим ускоренным охлаждением. Цель работы – изучить микроструктуру промышленной трубной стали категории прочности Х80 после термомеханической обработки, а также особенности формирования структур в зоне сварного соединения стали Х80 под воздействием лазерной сварки и оценить механические свойства полученных сварных соединений. Значимость работы заключается в изучении новой технологии создания сварных соединений для газо- и нефтепроводов работающих в условиях низких температур.The object of research is steel of strength category X80 after controlled longitudinal rolling with the end of rolling in the (? + ?) region and subsequent accelerated cooling. The purpose of the work – is to study the microstructure of industrial pipe steel of strength category X80 after thermomechanical processing, as well as the features of the formation of structures in the weld zone of steel X80 under the influence of laser welding and to evaluate the mechanical properties of the welded joints. The significance of the work consists in the study of a new technology for creating welded joints in gas and oil pipelines working in difficult climatic conditions

Design and development of the re-entry sensor system for the CubeSat mission SOURCE

With the number of man-made objects being launched into orbit steadily increasing, space debris is one of the big challenges for future space flight. In order to better assess the danger to humans on Earth’s surface, re-entry should be researched in more detail. SOURCE serves as a 3U+ satellite platform designed and developed by the small satellite student society (KSat e.V.) and the Institute of Space Systems (IRS) at the University of Stuttgart. It was selected by ESA in 2020 to be part of the ‘Fly your Satellite’ program, has successfully completed the CDR and is currently preparing for the MRR. SOURCE’s objectives are education, verification of several cost-saving, not yet space-proven technologies for orbital use, capturing images of meteoroids entering Earth's atmosphere and documenting its own demise during re-entry by analysing atomic oxygen, heat flux- and pressure data. In order to receive data for as long as possible during re-entry, the satellite switches from S-band to Iridium (inter-satellite link) communication at an altitude below 200 km. For the in-situ measurement during the re-entry, SOURCE is equipped with two Flux-Phi-Probe (FIPEX) sensors for the measurement of atomic oxygen and five additional sensor arrays. Each array contains one pressure sensor and two heat flux sensors, one commercial and one developed by the IRS. The arrays are placed at five positions in-line across the satellite to reduce effects of tumbling during the re-entry and to allow for the measurement of gradients. For a first estimation of the expected value ranges, simulations were performed with the software PICLas, developed by the IRS and the Institute of Aero-and Gas Dynamics (IAG) at the University of Stuttgart. In an iterative process, the collected data will be used to further improve this simulation software after the re-entry of the SOURCE satellite. The aim of this paper is to describe the design philosophy and development process of the sensor readout electronics. The tests carried out are presented and the first results are presented