Wolfgang Stautner

Bio: Wolfgang Stautner is an academic researcher from General Electric. The author has contributed to research in topics: Superconducting magnet & Electromagnetic coil. The author has an hindex of 8, co-authored 17 publications receiving 180 citations.

Lightweight, compact, and high-performance 3T MR system for imaging the brain and extremities

Abstract: Purpose To build and evaluate a small-footprint, lightweight, high-performance 3T MRI scanner for advanced brain imaging with image quality that is equal to or better than conventional whole-body clinical 3T MRI scanners, while achieving substantial reductions in installation costs. Methods A conduction-cooled magnet was developed that uses less than 12 liters of liquid helium in a gas-charged sealed system, and standard NbTi wire, and weighs approximately 2000 kg. A 42-cm inner-diameter gradient coil with asymmetric transverse axes was developed to provide patient access for head and extremity exams, while minimizing magnet-gradient interactions that adversely affect image quality. The gradient coil was designed to achieve simultaneous operation of 80-mT/m peak gradient amplitude at a slew rate of 700 T/m/s on each gradient axis using readily available 1-MVA gradient drivers. Results In a comparison of anatomical imaging in 16 patients using T2 -weighted 3D fluid-attenuated inversion recovery (FLAIR) between the compact 3T and whole-body 3T, image quality was assessed as equivalent to or better across several metrics. The ability to fully use a high slew rate of 700 T/m/s simultaneously with 80-mT/m maximum gradient amplitude resulted in improvements in image quality across EPI, DWI, and anatomical imaging of the brain. Conclusions The compact 3T MRI system has been in continuous operation at the Mayo Clinic since March 2016. To date, over 200 patient studies have been completed, including 96 comparison studies with a clinical 3T whole-body MRI. The increased gradient performance has reliably resulted in consistently improved image quality.

Second Test Coil for the Development of a Compact 3 T $ \hbox{MgB}_{2}$ Magnet

Abstract: The authors have reported the results of low n -value from a MgB2 test coil developed a year ago. A second test coil has been developed with wire of different structure and manufacturing process. Although the n-value related voltage of the second test coil was lower than the first test coil at designed current, it still showed low n-value. A third test coil has been wound with reduced mechanical stress. It also showed very similar n-value related voltage and n-value. Investigation of voltage distribution over the coil indicated that magnetic field was the major factor causing degradation of the n-value and resulting in n -value related voltages. Since the n-value related coil voltages were on the order of 0.1 μV/cm, the usual short sample Ic test (1 μV/cm was the definition of Ic ) might not detect the n-value related voltage and might not be able to investigate the cause of low n -value. Therefore, the medium length ( ~ 10 m) samples were tested and they showed the wire's lengthwise nonuniformity both on n-value and Ic, which might be another potential cause of the low n-value of the coil. Along with the electrical investigation, the manufacturing process of the wire was carefully inspected for longitudinal uniformity. Some wire segment samples from the same batch exhibited nonuniformity in the particle size distribution resulting in nonuniform filaments. This might have occurred in the wire for the second and third test coils.

Test Coil for the Development of a Compact 3 T ${\rm MgB}_{2}$ Magnet

Abstract: An test coil was manufactured and tested as the first step in the development of a 3 T MgB2 magnet system. Due to the fact that MgB2 has a higher critical temperature, replacing conventional NbTi superconductor with MgB2, higher temperature operation will be possible. It will make the cryogenic design much simpler and less expensive. Furthermore, operating the magnet at higher temperature results in larger heat capacity of the materials and surrounding structures. Higher heat capacity, therefore, results in increased thermal stability of the magnet against quench initiation. The 3 T magnet design consists of several coils. One of the center coils was manufactured for testing the performance at higher temperatures. The test coil was conduction cooled and the quench performance of the coil was good, which means there were no critical issues during the coil manufacturing process. However, AC loss heating, as well as a small resistance of the coil was found, both of which might result from wire design, manufacture, and quality.

Superconducting Synchronous Motors for Electric Ship Propulsion

Abstract: This paper develops a notional design for a 36 MW, 120 rpm motor for ship propulsion. The design exhibits high torque density (66 Nm/kg) and high efficiency (99%). This synchronous motor uses LTS (low temperature superconducting) field coils to create a minimum of 2 T magnetic field in the air gap of the motor. The motor is substantially lighter, more compact, and far more cost effective than other compared approaches. A significant feature of the LTS motor is reduction in radial forces between the field and armature by two orders of magnitude compared to a conventional motor. The motor promises significant cost and performance improvement. Conductor requirements, options, and electromagnetic features such as quench protection and cryogenic support options are discussed.

A New Cooling Technology for the Cooling of HTS Magnets

Abstract: For decades, the cooling method of conventional superconducting magnets has been "pool-boiling" in liquid cryogen. The commercial availability of HTS superconductors with an operating temperature in the 20 K region however calls for a new cooling strategy due to cost and availability of the new coolants involved. In this paper an alternative to the traditional bath-cooling of magnets with liquid helium is presented by employing a network of dedicated cooling tube structures capable of satisfying the different operating conditions of the magnet as well as the conductor stability requirements. The proposed closed-loop cooling tube concept based on the thermosiphon principle without loss of coolants and minimizing the coolant inventory while at the same time requiring no operator intervention has been tested. The design and the test results are discussed.

Recent Developments in High-Temperature Superconducting Magnet Technology (Review)

Abstract: The use of magnets made of high temperature superconductors (HTS) such as BSCCO and REBCO easily provide higher magnetic fields and higher operating temperatures, enabling dramatic improvements in superconducting magnet technology. The LTS magnet technology is very well summarized in text books written by M. N. Wilson (Superconducting magnets, Clarendon Press Oxford, 1983) and Y. Iwasa (Case studies in superconducting magnets, 2nd edition, Springer, 2009), covering such topics as stability, protection, ac loss and so forth. To the contrary, HTS conductors were commercialized only recently and therefore the magnet technology for HTS conductors remains undeveloped, especially so in the case of REBCO conductors. The technological problems for HTS coils thus far encountered are 1) an enormous effect of a screening current-induced magnetic field, 2) degradation in the coil performance due to excessive mechanical stresses applied along the longitudinal and transverse direction, and 3) the difficulty in protecting the magnet in the case of an abrupt thermal runaway. This paper reviews recent progress in overcoming these technological problems for HTS magnets. Both BSCCO and REBCO conductors have been used for HTS magnets in areas such as high field facilities, NMR, MRI, magnetic levitation trains and so forth. The effect of the screening current is the major problem for NMR, MRI, and accelerators, as it substantially distorts spatial field homogeneity and temporal field stability; on the other hand, degradation due to excessive stresses is substantial for high field magnets. Additionally, coil protection is a common and substantive problem among high current density HTS magnets in general. World-wide activities in developing BSCCO and REBCO magnets are overviewed in this paper.

Novel technologies and configurations of superconducting magnets for MRI

Abstract: A review of non-traditional approaches and emerging trends in superconducting magnets for MRI is presented. Novel technologies and concepts have arisen in response to new clinical imaging needs, changes in market cost structure, and the realities of newly developing markets. Among key trends are an increasing emphasis on patient comfort and the need for ?greener? magnets with reduced helium usage. The paper starts with a brief overview of the well-optimized conventional MR magnet technology that presently firmly occupies the dominant position in the imaging market up to 9.4?T. Non-traditional magnet geometries, with an emphasis on openness, are reviewed. The prospects of MgB2 and high-temperature superconductors for MRI applications are discussed. In many cases the introduction of novel technologies into a cost-conscious commercial market will be stimulated by growing needs for advanced customized procedures, and specialty scanners such as orthopedic or head imagers can lead the way due to the intrinsic advantages in their design. A review of ultrahigh-field MR is presented, including the largest 11.7?T Iseult magnet. Advanced cryogenics approaches with an emphasis on low-volume helium systems, including hermetically sealed self-contained cryostats requiring no user intervention, as well as future non-traditional non-helium cryogenics, are presented.

A Study on the No Insulation Winding Method of the HTS Coil

Abstract: This paper reports a study on BSCCO and ReBCO HTS (high temperature superconducting) test coils, layer-wound and double-pancake, with and without turn-to-turn insulation. Over current tests were performed in a bath of liquid nitrogen to compare stabilities of the test coils at 77 K. Saturation of magnetic fields from the NI (no insulation) coils, both BSCCO and ReBCO, was observed owing to current bypassing through turn-to-turn contacts in local quenches at operating currents higher than their critical currents. In the NI ReBCO coils, global quenches occurred at operating currents higher than the coil critical currents and quench recoveries were observed during discharge of the coils. The experimental results, obtained to date, demonstrate that the NI winding method enables remarkable improvement of thermal stability of the HTS coils.

Accessible magnetic resonance imaging: A review.

Abstract: The role of MRI in diagnostics, prognostics, and discoveries in basic sciences has been well established. However, access to this life-saving technology is largely restricted to countries in upper-middle to high-income groups. In this article, we collate recent global MR scanner density data and group them into six geographical regions based on the WHO classification. We then analyze these data with respect to demographic factors such as population size, life expectancy, the percentage of internet users, and World Bank income grouping. We map these demographic factors to five dimensions or characteristics of accessible MRI, adapting definitions from the healthcare literature. With this background, the study then reviews recent demonstrations of accessible MRI categorized based on main magnetic field strength. We describe demonstrated examples for each of these categories, ranging from ultralow-field to ultrahigh-field MRI. Lastly, we review MR methods and associated developments impacting accessible MRI such as increasing/augmenting MR awareness and local expertise, incorporating hardware-cognizant methods, rapid quantitative imaging, and leveraging innovations from adjacent fields. Level of Evidence: 5 Technical Efficacy Stage: 6 J. Magn. Reson. Imaging 2019.

A portable scanner for magnetic resonance imaging of the brain.

Abstract: Access to scanners for magnetic resonance imaging (MRI) is typically limited by cost and by infrastructure requirements. Here, we report the design and testing of a portable prototype scanner for brain MRI that uses a compact and lightweight permanent rare-earth magnet with a built-in readout field gradient. The 122-kg low-field (80 mT) magnet has a Halbach cylinder design that results in a minimal stray field and requires neither cryogenics nor external power. The built-in magnetic field gradient reduces the reliance on high-power gradient drivers, lowering the overall requirements for power and cooling, and reducing acoustic noise. Imperfections in the encoding fields are mitigated with a generalized iterative image reconstruction technique that leverages previous characterization of the field patterns. In healthy adult volunteers, the scanner can generate T1-weighted, T2-weighted and proton density-weighted brain images with a spatial resolution of 2.2 × 1.3 × 6.8 mm3. Future versions of the scanner could improve the accessibility of brain MRI at the point of care, particularly for critically ill patients. A portable prototype scanner for brain MRI that uses a compact and lightweight permanent rare-earth magnet with a built-in readout field gradient generates clinically relevant images of the brain, as shown in adult volunteers.