Resistive Insert Research Articles

Progress Report on the 43 T Hybrid Magnet of the LNCMI-Grenoble

A CEA-CNRS French collaboration is currently developing a new hybrid magnet to produce in a first step a continuous magnetic field of 43 T in a 34-mm warm bore aperture. This magnet combines a resistive insert, composed of Bitter and polyhelix coils, and a large bore superconducting “outsert.” The superconducting coil is based on the novel development of a Nb-Ti/Cu Rutherford Cable On Conduit Conductor (RCOCC) cooled down to 1.8 K by a bath of superfluid helium at atmospheric pressure. It aims at producing a nominal magnetic field of 8.5 T in a 1.1-m cold bore diameter. The specifications of the RCOCC will be presented together with the design and parameters of the cryogenic system. The solution to reduce the coupling between resistive and superconducting coils will be recalled as well as the constraints for designing the mechanical structure. The design study phase is coming to an end. The status of the conductor production and the next steps of the project are presented.

Homogeneity Study for the NHMFL Series Connected Hybrid Magnet System

The first Series Connected Hybrid (SCH) Magnet presently being designed and built at the NHMFL has targeted 36 T with 1 ppm maximum inhomogeneity over a 10-mm-diameter spherical volume at the midplane of a 40-mm clear bore for scientific users interested in medium resolution NMR studies. The SCH comprises a 13T superconducting outsert built with Nb3Sn cable-in-conduit conductors, a 23 T resistive insert using Florida-Bitter technology, and water-cooled resistive shims providing up to 90 ppm correction. The insert and outsert are connected electrically in series. Inhomogeneity predictions for the unshimmed SCH were made using various finite element analyses on a preliminary SCH design. Manufacturing tolerances were benchmarked by performing a sensitivity analysis and comparing the finite element analyses results to inhomogeneity measurements on the Keck and Cell 2 magnets, two NHMFL magnets, which represent the state-of-the-art for producing high homogeneity fields with resistive Florida-Bitter technology. Next, the shim terms from the measured and predicted 3-D field maps were analyzed with an NHMFL in-house code, which provided the inhomogeneity specification of the unshimmed SCH. Finally, a design of the SCH water-cooled resistive shims was developed based on all the measured and calculated data including additional engineering safety factors. This analysis is an essential step for achieving the targeted overall performance of a record 1 ppm inhomogeneity at 36 T.

Final Design of the 40 T Hybrid Magnet Superconducting Outsert

A 40 T hybrid magnet is being developed at the High Magnetic Field Laboratory of the Chinese Academy of Sciences. The magnet consists of a resistive insert and a superconducting outsert providing nominally 29 T and 11 T, respectively. The super-conducting outsert with a room temperature bore diameter of 800 mm is composed of three Nb3Sn coils wound from four grades of cable-in-conduit conductor cooled with forced-flow supercritical helium at an inlet temperature of 4.5 K. This paper gives the final design of coils and support structure of the superconducting outsert. Finite element analyses has been performed for normal operational and fault loads. We also describe the cooling scheme, quench detection, and protection.

Mutation design and strain background influence the phenotype of Escherichia coli luxS mutants

Previous analyses of luxS in Escherichia coli have used different strain backgrounds and design formats to produce the luxS mutation, resulting in luxS mutants with confusingly dissimilar phenotypes. This study therefore investigates the roles that strain background and mutational design strategy have upon the phenotype of the pathogenic E. coli luxS mutant. We inactivated luxS in three E. coli backgrounds: enteropathogenic E. coli E2348-69, and enterohaemorrhagic strains Sakai and NCTC12900. To investigate the influence of mutational design strategy, four mutation formats were used: antibiotic resistance insertion methodologies as previously employed, using tetracycline and chloramphenicol resistance cassettes, and non-polar strategies creating deletion and premature termination mutations. Our study showed that the E. coli luxS phenotype was markedly dependent on strain background: in some strains disruption of luxS caused significant metabolic stress or no stress at all. How the luxS mutation was constructed also shaped its phenotype: non-polar mutants were very similar to wild type, while mutations made using the antibiotic insertion methodologies produced phenotypes defective in growth and virulence. Proteomic profiling of our luxS mutants showed only a few proteins were differentially expressed and those that were altered suggested a metabolic rather than communication role for the E. coli luxS gene product.

영구 자석형 동기전동기(PMSM)의 직렬저항을 이용한 제동력 운전 확보에 관한 연구

본 논문에서는 공기제동의 문제점을 보완하기 위한 유지보수와 환경문제, 효율성, 경제성 등을 개선하기 위하여 정지에서 고속영역까지의 전 영역에서 전기제동을 사용하는 방법이 제시되었다. 전기적으로 완전제동을 위한 2가지 방법으로 인버터 출력전압의 증대에 의한 방법과 전동기와 인버터 사이에 직렬저항을 삽입하는 방법을 통하여 경제적이며 실제 적용이 가능한 제어방법인 직렬저항을 삽입하는 방법을 적용하기로 하였다. 직렬저항에 의한 전력손실을 감소시키기 위한 직렬저항을 단락 하는 방법을 사용하여 효율을 개선하고 전 영역에서의 제동력확보는 실험환경 내에서 우수한 인버터의 단자전압을 상승시키는 방법과 동일한 특성을 보였다. In this paper, method using electric braking from stop area to high-speed area was presented in order to improve air-brake. And electric braking method can be improved environmental problems, efficiency, economy, etc. Method for electrical complete braking are two ways that method of inserting series resistance between the motor and the inverter, and method of inverter output voltage increase. In this paper, use series resistance insert method because economical and easy to apply. In addition, Series resistor is used short circuit method for reduce the power loss. In improved efficiency and the laboratory environment for secure braking, resistance insert method and inverter output voltage increase method showed same characteristics in all areas.

DC and RF characteristics of bilayer Schottky metal contact on n-GaN Schottky diode

In device technology, the multilayer contacts provide improved performance. The comparative study of different high work function bilayer Schottky metal (Pt/Pd, Pt/Ni and Pt/Ti) contact has been taken to study the DC and RF performance of n -GaN Schottky diode. The fabricated Schottky metal contact Pt/Pd, Pt/Ni and Pt/Ti annealed from room temperature to 800 °C studied shows that Pt/Pd Schottky metal contact on n -GaN shows high thermal stability and maximum barrier height 1.10 eV, ideality factor 1.001, lower series resistance and lower insertion loss (S 21 dB) at high frequency compared to Pt/Ni and Pt/Ti bilayer Schottky metal contact.

Wide Variety of Experiments Using a Cryogen-Free 27.5 T Hybrid Magnet and a Cryogen-Free 18.1 T Superconducting Magnet

A cryogen-free hybrid magnet without liquid helium for operation, generating 27.5 T in a 32 mm room temperature bore of an 8 MW water-cooled resistive insert magnet in an 8.5 T background field of a cryogen-free superconducting outsert magnet, is being operated for basic research at low temperatures down to 17 mK in combination with a dilution refrigerator. In addition, we are developing functional materials using a differential thermal analysis DTA at high temperatures up to 1473 K in high fields up to 27 T. This cryogen-free hybrid magnet will be upgraded to generate 29 T by improving the outer superconducting magnet. A cryogen-free 18.1 T superconducting magnet with a 52 mm room temperature experimental bore, consisting of a Bi2Sr2Ca2Cu3O10 (Bi2223) insert coil, has been developed using a GM-JT cryocooler. Recently, bronze-tape-laminated Bi2223 has revealed excellent irreversible stress tolerance of 250 MPa at 77 K. In addition, the critical current properties for recent Bi2223 tapes are largely improved from 200 to 400 A/cm-width at 77 K in a self-field. Therefore, the stainless steel reinforcement tape incorporated for the previous Bi2223 insert coil is no longer needed for a new Bi2223 one. A new Bi2223 insert coil with almost the same size as the existing insert coil can generate two times higher fields at the elevated operation current from 162 to 191 A. An upgraded cryogen-free superconducting magnet can offer a long-term experiment at the constant magnetic field of 20 T for an in-field heat-treatment investigation.

Final Design of the New Grenoble Hybrid Magnet

A CEA-CNRS French collaboration is currently developing a new hybrid magnet; this magnet combines a resistive insert composed of Bitter and polyhelix coils and a new large bore superconductor outsert to create an overall continuous magnetic field of 42+ T in a 34 mm warm aperture. The design of the superconducting coil outsert has been completed after thorough studies and successful experimental validation phases. Based on the novel development of a Nb-Ti/Cu Rutherford Cable On Conduit Conductor (RCOCC) cooled down to 1.8 K by the mean of a bath of superfluid helium at atmospheric pressure, the superconducting coil aims to produce a continuous magnetic field of 8.5 T in a 1.1 m cold bore diameter. The main results of the final design studies of the superconducting coil are presented including the 2D and 3D mechanical stress analysis, the conductor and coil specifications, the coil protection system as well as the required cryogenics infrastructure. The final design of the resistive insert coils is also described.

Hybrid Magnet Design Consisting of a 20 T Superconducting Outsert and a 15 MW Resistive Insert

Internally reinforced Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands with CuNb-reinforcing stabilizer have been developed for realizing a compact high-field superconducting magnet. The Rutherford flat cables composed of sixteen strands were made with a 0.8 mm diameter CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand. The designed critical current of the CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford flat cable is I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 1890 A at 13 T and 4.2 K in case of an ordinary heat-treatment at 670 for 96 h, which is two times higher than an operation current desired for safety margin. In addition, mechanical characteristics for CVD-processed YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> (YBCO) coated-conductor tapes were measured at 4.2 K in fields up to 18 T. It was found that YBCO tape exhibits the irreversible strain 0.5% and the irreversible stress 1140 MPa for the critical current at 4.2 K and 18 T for B//c. The cabling-and-react+prebending-processed CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford flat cables and CVD-processed YBCO tapes will be used as a react-and-wind method for the development of a 20 T superconducting magnet with a wide room temperature bore. We design a 20 T-440 mm warm-bore superconducting magnet consisting of YBCO inner coils, middle coils, and NbTi outer coils, which has the coil parameters of inner diameter 480 mm, outer diameter 1283 mm, and coil height 1302 mm. Since the coil inductance is estimated to be 232 H, the magnetic stored energy is 94 MJ at an operation current 900 A. An energy-saving 47 T hybrid magnet can be constructed in combination with a wide-bore 20 T superconducting outsert and a 15 MW-27 T water-cooled resistive insert.

Design of the Outsert Coil of the 45 T Hybrid Magnet at the Nijmegen High Field Magnet Laboratory

The Nijmegen High Field Magnet Laboratory (Nijmegen HFML) is developing a 45 T hybrid magnet consisting of a 12 T CICC <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\rm Nb}_{3}{\rm Sn}$</tex></formula> superconducting outsert magnet and a 33 T Florida-Bitter resistive insert magnet. After a thorough review last year of the conceptual design of the superconducting outsert magnet in particular, the conductor and coil design for the outsert magnet have been adapted to create a larger performance margin so as to meet more adequately the possible uncertainties especially in CICC performance.

Investigation of 15 to 24 MW Resistive Insert Magnets Built Into a 20 T $\varnothing$440 mm Room-Temperature Bore Superconducting Outsert Magnet

The Tsukuba Magnet Laboratory and the High Field Laboratory for Superconducting Materials collaborated on developing the next-generation 50 T-class hybrid magnet. One of the properties to be incorporated into this next-generation hybrid magnet is energy-saving operation in generating a high-strength magnetic field. This report presents the estimated performance of this hybrid magnet, on the basis of a 20 T O440 mm room temperature bore for the superconducting outsert magnet, DC power of 15-24 MW for a three-layered Bitter resistive insert magnet, and a O32 mm room-temperature bore for the resistive insert magnet. Cu-Zr (Cu-Ag) alloy is assumed material to be used for the outermost layer (inner two layers) of the Bitter magnet. The estimation indicates that the hybrid magnet generates magnetic fields beyond 47.9 T (49.1 T) for a resistive insert magnet operation power of 15 MW (24 MW) in a 20 T background magnetic field, where the upper-limit design stress on the innermost Bitter coils is tentatively assumed to be 800 MPa. An ultimate tensile strength exceeding 1140 MPa with a conductivity of 72% International Annealed Copper Standard (IACS) for a Cu-Ag alloy plate would be necessary to meet the design stress of 800 MPa. Using this material, we could make the 15 MW water-cooled resistive insert magnet (WM) for this energy-saving, compact hybrid magnet that generates magnetic fields of 47 T and beyond. For a moderated upper-limit design stress of 760 MPa, the corresponding magnetic fields of the hybrid magnet are 47.5 and 48.5 T.

Conical Insert Design for the HZB Series-Connected Hybrid

The National High Magnetic Field Laboratory (NHMFL) is designing series-connected hybrid magnets for the Helmholtz Center Berlin (HZB). The hybrid has a horizontal, conical warm bore with a 30 degree opening angle for neutron scattering experiments. The resistive insert includes two coils. The outer coil is a regular bitter coil, while the inner one has a varied inner radius to meet the requirement of large opening angle. Such technology as in the inner coil was developed in the NHMFL, and called Florida conical bitter technology. The conical configuration makes the cooling hole length varied with radius causing unique hydraulic design challenge. This paper presents the detail design features of the conical insert along with many analysis results.

Joint Design and Test for the SCH

The NHMFL Series Connected Hybrid (SCH) magnet will provide an energy-efficient 36 T to the DC user facility by employing a 20 kA superconducting outsert coil in series with a resistive insert. The magnet outsert consists of three concentric layer-wound sub-coils using three different grades of Nb3Sn Cable-in-Conduit Conductors (CICC). The electrical joints in the superconducting outsert require low DC resistance to minimize the refrigeration requirement at the operational 4.5 K temperatures and low AC losses to ensure good stability against ramping operation required by the users. There are four internal splice joints in the outsert, which are Nb3Sn to Nb3Sn joints with the same design configuration. There are another two terminal joints between the Nb3Sn outsert and the two NbTi buslines, which connect the outsert terminals to the two current leads. The two Nb3Sn to NbTi terminal joints are of identical configurations. All of the joints will be praying-hands configuration with an operation current of 20 kA. The R&D for the joins has been carried out at the NHMFL. The joints design and test results are discussed in this article.

Protection System for the Superconducting Outsert Coils of the HFML 45 T Hybrid Magnet

The High Field Magnet Laboratory of the Radboud University Nijmegen is developing a 45 T hybrid magnet consisting of a 33 T resistive insert magnet and a 12 T, all Nb3Sn-Cu Cable-In-Conduit Conductor (CICC) based superconducting outsert magnet. Standard quench protection of the outsert coils is achieved with a permanently connected external dump resistor parallel to the coils. A major challenge is to prevent a quench of the outsert magnet during spurious trips of the insert circuit that may occur. Such an event is characterized by a fast decay of the insert current generating field changes at the windings of the outsert coils of a few T/s. Without precautions, the resulting AC losses in the superconducting strands would quench the inner windings. Here we present a model to analyse the effectiveness of an adapted protection scheme in terms of system and component characteristics and the required AC loss properties of the proposed CICC design.

Eddy-Current Analysis of Cold Mass and Thermal Shield for Series-Connected Hybrid Magnet

The National High Magnetic Field Laboratory currently has three series-connected hybrid (SCH) magnet projects, where resistive coils are connected in series with superconducting coils using cable-in-conduit-conductor (CICC) underway: first for the magnet laboratory in Tallahassee, FL; second for the Helmholtz Zentrum Berlin for Materials and Energy (HZB), Germany; and the third for the Spallation Neutron Source at the Oak Ridge National Laboratory, TN. The one for HZB has a horizontal conical bore with a 30^ opening angle for neutron scattering experiments. During power supply trip, superconducting magnet quench, resistive insert short, and insert fault, transient electromagnetic effects as a result of fast decay of the coil current introduce a significant amount of eddy current and Lorentz force on the conductive components of the cryostat such as the metallic cold-mass magnet frame and the 50-K thermal radiation shield. Although the eddy-current heating is not a concern during quench and fault operations, the eddy-current-induced Lorentz forces need to be taken into account in the structural design of the SCH cryostat. In this paper, a detailed eddy-current analysis for the HZB magnet during abnormal operations has been performed for its cryostat based on the dry magnet design concept. The nonuniform eddy-current distribution from the finite-element analysis implies that local hot spots may develop under abnormal operations. The eddy-current-induced Lorentz forces are quantified to ensure the strength and stability of the cryostat structure and, most importantly, safety of the SCH magnet during abnormal conditions.

Cloning of the nptII gene of Escherichia coli and construction of a recombinant strain harboring functional recA and nptII antibiotic resistance

In an attempt to clone the ORF of the nptII gene of Escherichia coli K12 (ATCC 10798), two degenerate primers were designed based on the nptII sequence of its Tn5 transposon. The nptII ORF was placed under the control of the E. coli hybrid trc promoter, in the pKK388-1 vector, transformed into E. coli DH5α ΔrecA (recombinant, deficient strain). Transferred cells were tested for ampicillin, tetracycline, kanamycin, neomycin, geneticin, paromomycin, penicillin, and UV resistance. The neomycin phosphotransferase gene of E. coli was cloned successfully and conferred kanamycin, neomycin, geneticin, and paromomycin resistance to recombinant DH5α; this did not inhibit insertion of additional antibiotic resistance against ampicillin and tetracycline, meaning the trc promoter can express two different genes carried by two different plasmids harbored in the same cell. This resistance conferral process could be considered as an emulation of horizontal gene transfer occurring in nature and would be a useful tool for understanding mechanisms of evolution of multidrug-resistant strains.

Carbon “Onions” as Point Electron Sources

The novel type of an electron field emitter is demonstrated by welding a single carbon "onion" onto the end of a tungsten tip inside a high-resolution transmission electron microscope. Such merged structure is found to markedly reduce the onset voltage peculiar to a standard tungsten field emitter due to the small size of the onion and its highly curved surface. Similar to short carbon nanotubes, individual C-onion emitters can sustain large emission currents, more than 100 muA, and exhibit good long-term emission stability. Moreover the insertion of a high electrical resistance in series can suppress the current fluctuation to only 1.9%. All these properties make these newly created field emitters promising candidates for the advanced point electron sources.

Recent Progress of the Series-Connected Hybrid Magnet Projects

The National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida has designed and is now constructing two Series Connected Hybrid (SCH) magnets, each connecting a superconducting outsert coil and a resistive Florida Bitter insert coil electrically in series. The SCH to be installed at the NHMFL will produce 36 T and provide 1 ppm maximum field inhomogeneity over a 1 cm diameter spherical volume. The SCH to be installed at the Helmholtz Center Berlin (HZB) in combination with a neutron source will produce 25 T to 30 T depending on the resistive insert. The two magnets have a common design for their cable-in-conduit conductor (CICC) and superconducting outsert coils. The CICC outsert coil winding packs have an inner diameter of 0.6 m and contribute 13.1 T to the central field using three grades of CICC conductors. Each conductor grade carries 20 kA and employs the same type of Nb3Sn superconducting wire, but each grade contains different quantities of superconducting wires, different cabling patterns and different aspect ratios. The cryostats and resistive insert coils for the two magnets are different. This paper discusses the progress in CIC conductor and coil fabrication over the last year including specification, qualification and production activities for wire, cable, conductor and coil processing.

Engineering Design of the Superconducting Outsert for 40 T Hybrid Magnet

A 40 T hybrid magnet system will be built at the Chinese High Magnet Field Laboratory (CHMFL), Chinese Academy of Sciences. It will include a 29 T resistive insert with a clear bore of 32 mm and a 11 T superconducting outsert with a room temperature bore of 580 mm. The superconducting outsert, which will be wound with cable-in-conduit conductors (CICC), is graded in function of the magnetic field. The high field section of the superconducting outsert will use superconductors and the low field section will be made of NbTi superconductors. At present, the preliminary design of the superconducting outsert has almost been completed. This paper describes features, such as conductor design, coil winding, heat treatment, support structure design, mechanical stress analysis.

A 40 T Hybrid Magnet Under Construction in China

The Chinese National Project to develop new high magnetic field facilities began in 2008. It includes the construction of a 40 T hybrid magnet. The magnet will be built at the Chinese High Magnetic Field Laboratory (CHMFL) of the Chinese Academy of Sciences. It consists of a superconducting outsert magnet and a resistive insert magnet. The outsert magnet with a bore diameter of 580 mm at room temperature is expected to provide 11 T. It is composed of two coils: the inner coil is made of cable-in-conduit-conductor (CICC), the outer coil of NbTi CICC. The insert magnet, which will be a 20 MW Florida-Bitter-type resistive magnet with a clear bore diameter of 32 mm, will produce 29 T. The construction of the hybrid magnet is scheduled to be completed in 2013.