High Magnetic Field Laboratory Research Articles

Bi-2223 Test Coils for High Resolution NMR Magnets.

Recently, significant improvement in the strain tolerance of Bi-2223 conductor has been achieved by lamination with high strength nickel alloy. The conductor, supplied by Sumitomo Electric and designated Type HT-NX, is now commercially available in lengths sufficient for manufacture of high-homogeneity solenoids. A program to fully exploit the improved conductor properties is now underway at the National High Magnetic Field Laboratory (NHMFL). Five coils are being made, the last of which is to demonstrate an NMR measurement approaching 1 GHz and 1 ppm over 10 mm volume. In so doing, we expect to demonstrate critical current fraction, and strain similar to that expected in 30 T NMR magnets. The coils will be tested inside an existing 16 Tesla large-bore background magnet at the NHMFL. The design of the NMR demonstration coil is presented first, with expected values for field, homogeneity and strain given. A technology development program is then outlined, which includes fabrication of four test coils to test various design features, develop fabrication tooling and train personnel.

Experimental Study on Potential Heat Treatment Issues of Large Bi-2212 Coils.

The route to 30 T NMR endorsed by a recent National Academy report clearly still has many challenges to achieve high stability and homogeneous high temperature superconducting (HTS) magnet. As the only HTS conductor with round wire (RW) geometry, Bi2Sr2CaCu2O8-x (Bi-2212) RW conductor is very attractive for NMR magnet applications. At present, an NMR quality demonstration magnet with Bi-2212 RW wound insert coils is under development at the National High Magnetic Field Laboratory (NHMFL). The target of this demonstration magnet is to generate a total field of 23+ T with ppm level homogeneity. Since Bi-2212 coils require Wind-and-React (W&R) technology, our initial major concern was that large Bi-2212 coils might deform during the typical partial melt Bi-2212 heat treatment (HT) due to their large self-weight. To experimentally mimic the HT of large Bi-2212 coil, several small test coils were heat treated under deadweight loads. After 1 bar Bi-2212 full reaction, these coils were characterized in terms of coil geometry, transport critical current properties, oxygenation status and insulation performance. Coil geometry and individual wire shape was in fact not distorted, nor was transport properties degradation was induced by mechanical loading. Uniform oxygen equilibration was achieved in these coils even though they were coated with dense oxide insulation. However, although the TiO2-based insulation coating was well preserved on the wire surface, several coils developed electrical shorts.

Identification and Characterization of Human Proteoforms by Top-Down LC-21 Tesla FT-ICR Mass Spectrometry.

Successful high-throughput characterization of intact proteins from complex biological samples by mass spectrometry requires instrumentation capable of high mass resolving power, mass accuracy, sensitivity, and spectral acquisition rate. These limitations often necessitate the performance of hundreds of LC-MS/MS experiments to obtain reasonable coverage of the targeted proteome, which is still typically limited to molecular weights below 30 kDa. The National High Magnetic Field Laboratory (NHMFL) recently installed a 21 T FT-ICR mass spectrometer, which is part of the NHMFL FT-ICR User Facility and available to all qualified users. Here we demonstrate top-down LC-21 T FT-ICR MS/MS of intact proteins derived from human colorectal cancer cell lysate. We identified a combined total of 684 unique protein entries observed as 3238 unique proteoforms at a 1% false discovery rate, based on rapid, data-dependent acquisition of collision-induced and electron-transfer dissociation tandem mass spectra from just 40 LC-MS/MS experiments. Our identifications included 372 proteoforms with molecular weights over 30 kDa detected at isotopic resolution, which substantially extends the accessible mass range for high-throughput top-down LC-MS/MS.

Field-stepped broadband NMR in pulsed magnets and application to SrCu2(BO3)2 at 54 T

Pulsed magnets generate the highest magnetic fields as brief transients during which the observation of NMR is difficult, however, this is the only route to unique insight into material properties up to the regime of 100T. Here, it is shown how rather broad NMR spectra can be assembled in a pulsed magnet during a single field pulse by using the inherent time dependence of the field for the recording of field-stepped free induction decays that cover a broad frequency range. The technique is then applied to 11B NMR of the spin-dimer system SrCu2(BO3)2, a magnetic insulator known to undergo a series of field-driven changes of the magnetic ground state. At peak fields of about 54T at the Dresden High Magnetic Field Laboratory, 11B NMR spectra spanning a total of about 9MHz width are reconstructed. The results are in good accordance with a change from a high-temperature paramagnetic state to a low-temperature commensurate superstructure of field-induced spin-dimer triplets.

Progress in the Development of the HFML 45 T Hybrid Magnet

To extend its user's facilities, the High Field Magnet Laboratory (HFML-EMFL) at the Radboud University is in the process of building a 45-T hybrid magnet. The magnet system will consist of a 22 MW 32.7 T resistive insert and a 600-mm-bore 12.3 T superconducting outsert magnet, and the design was significantly adjusted after a thorough design revision in 2011. The HFML hybrid magnet will be operated with separate current sources for the superconducting and resistive coils (20 kA at 10 V and 40 kA at up to 550 V, respectively). The outsert coil is a solenoid layer wound with all-Nb 3 Sn/Cu cable-in-conduit conductor (CICC), cooled by a forced flow of supercritical helium and operated at 20 kA. Similar to the series-connected hybrids for the HZB (Berlin, Germany) and the NHMFL (Tallahassee, FL, USA), the HFML outsert coil contains three grades of conductor. All CICC grades are based on high-current density Nb3Sn strand produced by Oxford Superconducting Technology. The CICC production and qualification program has been completed successfully. The coil will be wound at the NHMFL and, after heat treatment and impregnation, sent to Nijmegen for integration into the cryostat. In this paper, the design choices and current status of the program are presented.

Fabrication and Testing of the 20 kA Binary Current Leads for the NHMFL Series-Connected Hybrid Magnet

A pair of binary vapor-cooled/high-temperature-superconducting current leads were fabricated at the National High Magnetic Field Laboratory (NHMFL) and tested at the High Field Magnet Laboratory (HFML) at the Radboud University Nijmegen. The leads supply current to the NHMFL series-connected hybrid magnet. Details of the fabrication are discussed, including that of the resistive and high-temperature-superconducting parts and the integration of the two sections. A test assembly was made, including the pair of current leads, a jumper made from NbTi cable-in-conduit, instrumentation, and mounting hardware. The test facility includes a liquid nitrogen supply vessel and a closed-loop supercritical helium supply system, to replicate the cooling used in the magnet assembly. Results from the testing of the leads to the full operating current, and under simulated loss-of-cooling conditions are presented.

Upgrade of the NHMFL Cryogenic System and the Index Heating Test Results on the 45-T Hybrid

The 45-T Hybrid at the National High Magnetic Field Laboratory (NHMFL) has been the only facility in the world capable of providing a dc field of above 40 T. The 45-T hybrid magnet, consisting of a superconducting outsert and resistive insert, was commissioned in 2000 reaching a field of 45 tesla. The cryogenic system for the NHMFL has been in service since 1994 and has provided cryogenic service for the 45-T hybrid superconducting outsert since testing in 1998. It was recently upgraded, replacing a majority of the original system. The 45-T Hybrid was cooled down successfully with the new cryogenic system in February 2014. The new cryogenic system has been proved more efficient and reliable in the past years, providing increased availability to the users. After the upgrade of the cryogenic system, a standard index heating test was performed on the outsert of the hybrid. This test is mainly for evaluating the performance of the outsert, particularly the degradation of the innermost Nb3Sn coil of the outsert that suffered an unprotected quench in 2000 and degradation since then. The results of index heating tests in the past are compared and presented.

Resistive Insert Magnet Designs for the Series-Connected Hybrids Developed at the NHMFL

The National High Magnetic Field Laboratory (NHMFL) has developed series-connected hybrids (SCHs) each comprising of a superconducting outsert built with Nb3Sn cable-in-conduit conductor and a resistive insert using Florida Bitter technology. The first SCH, to be operated at the Helmholtz Center Berlin, has been tested successfully generating a central field above 25 T in a horizontal conical warm bore with a 30° opening angle suitable for neutron scattering experiments. The resistive insert contributing 13 T includes two coils electrically in series with a total power consumption of 4.4 MW. The second SCH, to be installed and operated at the NHMFL, has a target to provide 1-ppm maximum field inhomogeneity in a 36-T 40-mm bore for medium-resolution nuclear magnetic resonance science. The resistive insert contributes 23 T and includes four coils electrically in series with a total power consumption of 14 MW. The innermost two resistive coils include axial current grading targeting unshimmed field uniformity below 100 ppm over a 10-mm-diameter spherical volume. The design of the resistive insert for the second SCH was completed in mid-2014, and this project is currently in the final construction phase.

First Hybrid Magnet for Neutron Scattering at Helmholtz-Zentrum Berlin

Helmholtz-Zentrum Berlin (HZB) operates two large-scale facilities: the research reactor BER 2 and the synchrotron source for soft X-rays BESSY 2. This year HZB's neutron instrument suite around BER 2 has been strengthened by a unique high-magnetic-field facility for neutron scattering. Its main components are the High Field Magnet (HFM), which is the most powerful dc magnet for neutron scattering worldwide, and the Extreme Environment Diffractometer (EXED), which is a dedicated neutron instrument for time-of-flight technique. The hybrid magnet system is projected according to the special geometric constraints of analyzing samples by neutron scattering in a high field magnet. Following our past experience, only steady-state fields are adequate to achieve the goals of the project. In particular, inelastic scattering studies would virtually be excluded when using pulsed magnets. The new series-connected hybrid magnet with a horizontal field orientation was designed and constructed in collaboration with the National High Magnetic Field Laboratory (NHMFL), Tallahassee, FL, USA. With a set consisting of a superconducting cable-in-conduit coil and different resistive coils of conical shape, maximum fields between 26-31 T are possible with cooling power between 4 and 8 MW for the resistive part. A series of commissioning activities of the magnet components and the technical infrastructure systems (20-kA power supply, water cooling, and 4-K Helium refrigerator) was completed at HZB. The maximum field achieved with a 4-MW resistive coil was 26 T.

Structural Integrity of the NHMFL Series-Connected Hybrid Magnet Cryostats

The National High Magnetic Field Laboratory has designed and built cryostats for two series-connected hybrid (SCH) magnets. The first one is for the Helmholtz Center Berlin. Its cryostat is designed to support up to 8 MW of resistive insert inside a water-cooled housing that has a conical warm bore with a 30-degree opening angle and a 5-ton superconducting outsert coil that is housed in a vacuum vessel. Normal operation includes 28 bar of water pressure and 52 kN of side load between the resistive insert coils and the superconducting outsert coils due to a potential 3-mm coil misalignment. Under a fault condition, the resistive coils can generate axial loads of up to 1.1 MN. The second cryostat for the Florida State University SCH houses the same superconducting outsert, but its resistive insert is a high-homogeneity solenoid. The system is designed to support a high-field 14-MW insert, operated at 30-bar water pressure, up to 42-kN side load, and 2.6-MN fault forces. Numerous complex two-dimensional and three-dimensional finite-element models have been developed and used for a systematic optimization of all critical load path items.

Design Study of a 10-T REBCO Insert Solenoid

As a first step to develop HTS insert technology, we plan to build a 10-T REBCO solenoid that will be tested at the French National High Magnetic Field Laboratory of Grenoble in France (LNCMI) at 4.2 K, in the aperture of a 20-T resistive magnet. Two winding approaches are being considered for the HTS insert, i.e., the no-insulation (NI) and metallic insulation (MI) winding technics. Both methods allow turn-to-turn bypassing current but differ in their turn-to-turn resistance value by three orders of magnitude. In this paper, we provide a comparative study between the two winding options using numerical simulations applied to a preliminary design of the insert, which features a cold bore diameter of 50 mm and is made of 15 double-pancake coils wound from a 6-mm REBCO tape.

Status and Development of Pulsed Magnets at the NHMFL Pulsed Field Facility

The National High Magnetic Field Laboratory's Pulsed Field Facility at Los Alamos National Laboratory is one of few research centers in the world that can create and use ultrahigh pulsed magnetic field for scientific research. The facility houses several types of nondestructive pulsed magnets which can provide the peak fields ranging from 60 to 100 T for users. This paper will report the status of the user magnets and recent magnet developments to improve the quality and magnetic fields of our user magnets. In particular, this paper will present a new cooling technique that significantly reduces the cooling time without affecting the mechanical performance of the magnets. A possible upgrade of our facility with a new duplex magnet that is powered by a 4-MJ capacitor bank to deliver 80 T for users will be also reported. In addition, we will discuss some valuable lessons learned from magnet failures at our facility and possible further magnet design improvements to increase the magnet longevity or peak magnetic fields.

Test of the MF-CICC Conductor Designed for the 12-T Outsert Coil of the HFML 45-T Hybrid Magnet

A 45-T hybrid magnet is being built at the High Field Magnet Laboratory of the Radboud University in Nijmegen, The Netherlands. The hybrid magnet consists of a 12-T cable-in- conduit-conductor (CICC) Nb 3Sn superconducting outsert and a 33-T resistive insert magnet. To verify the CICC design, a thorough testing has been completed in the SULTAN facility at Swiss Plasma Center, EPFL in Villigen (Switzerland) for the medium- grade conductor of the outsert. In two test campaigns, the dc cable performance (current-sharing temperature, critical current), the ac loss, and the conductor's performance stability during cyclic loading and after one warmup and cooldown cycle have been investigated. Two different cable layouts were tested—one with a very short twist pitch (STP) and the second one with a long twist pitch (LTP) cabling pattern. As both conductors were made of the same Nb 3Sn strand and underwent the same heat treatment and sample preparation procedure, the effect of the twist pitch on the ac loss and on the dc performance with respect to cyclic loading could be reliably evaluated. The test results show that both cable layouts are actually very robust. The cable could withstand 2000 load cycles and the warmup and cooldown cycle without any significant degradation of the dc performance, and even the overloading at BI product (field multiplied by current) approximately two times larger than those foreseen during magnet operation did not lead to a big performance change. Small differences between the STP and LTP options have been observed, indicating that the STP conductor withstands high electromagnetic loads better than the LTP one.

Analysis of quench in the NHMFL REBCO prototype coils for the 32 T Magnet Project

A 32 T all-superconductive magnet with high field REBCO inner coils is under development at the National High Magnetic Field Laboratory, Tallahassee, Florida, USA. As part of the development activity, two prototype coils with full scale radial dimensions and final design features, but with reduced axial length were constructed. The prototype coils consist of six dry-wound double pancakes modules with uninsulated conductor and insulated stainless steel cowind. Quench studies on one of the prototype coils at 4.2 K in self-field and in a background magnetic field of 15 T were performed by activating a set of quench protection heaters. In this paper, we present a numerical analysis of the experimental results of the quench tests of one of the prototype coils. The numerical analysis was carried out through a coupled electro-thermal FEM model developed at the University of Bologna. The model is based on the coupling with distributed contact resistances of the coil pancakes described as 2D elements. A homogenization procedure of the REBCO tape and other coil materials is presented, which allows reducing the number of degrees of freedom and the computational effort. The model is applied to the analysis of the current and voltage evolutions during the experimental quench tests on the prototype coil.

Water Cooled Resistive Magnets at CHMFL

The steady high magnetic field facility was founded by the National Development and Reform Commission of China (NDRC) in 2008 and is undertaken by the High Magnetic Field Laboratory of the Chinese Academy of Sciences. The project includes the construction of a series of water-cooled resistive magnets, superconducting magnets, and a hybrid magnet. Up-to-date, five water-cooled resistive magnets have been successfully installed. In addition, the six coils of the resistive magnet insert for the 45-T hybrid magnet have also been assembled and will be tested early next year. Two new world records of water-cooled resistive magnets have been achieved, i.e., 38.5 T/O32 and 35 T/O50 mm. Design, optimization, and assembly of the magnets, as well as their characterization are described in detail in this presentation.

Construction and performance of a 38 T resistive magnet at the Nijmegen High Field Magnet Laboratory

In 2011, we have presented the design of a 38-T resistive magnet with a 32-mm bore, which has been designed to satisfy the users' demand for higher magnetic fields. Manufacturing of the parts started in 2012 and has been completed in early 2013. In this paper, we present the final design specifications and report on the construction, commissioning, and performance of the magnet. The five Florida–Bitter coils and the outer Bitter coil of this magnet consume 20.5 MW at 40 kA and generate a magnetic field of 37.5 T. The outer coil has a diameter of 1 m and weighs just over 3000 kg. Key ingredients in the design of this magnet are the modified Weggel stacking scheme, the modifications to the cooling hole shape, and a new compact housing.

NMR shift and relaxation measurements in pulsed high-field magnets up to 58 T

Nuclear magnetic resonance (NMR) experiments at fields up to 58T in pulsed magnets at the Dresden High Magnetic Field Laboratory are reported. The challenge to resolve NMR shifts in these time-dependent fields is addressed for the first time, and it is shown that this can indeed be accomplished with high precision with an internal reference. As a result, signal averaging is possible during a single magnetic field pulse, but also for multiple pulses. Thus, even very weak signals can in principle be recorded and their shifts can be determined. In a second set of experiments, the measurement of nuclear relaxation is investigated. Using adiabatic inversion with the inherent time dependence of the magnetic field and small-angle inspection, it is shown that relaxation measurements are possible, as well. The shift experiments were performed with 27Al NMR on a mixture of aluminum metal and a Linde type A zeolite. For the relaxation studies, 27Al NMR and 69Ga NMR on the metals aluminum and gallium were preformed, respectively.

A facility for X-ray diffraction in magnetic fields up to 25 T and temperatures between 15 and 295 K.

A facility for X-ray diffraction has been developed at the National High Magnetic Field Laboratory. It brings diffraction capability to the 25 T Florida split coil magnet and implements temperature control in a range of 15-295 K using a cold finger helium cryostat. This instrument represents an alternative to pulsed magnetic field systems, and it exceeds the static magnetic fields currently available at synchrotron facilities. Magnetic field compatibility of an X-ray source and detectors with the sizable magnetic fringe fields emanating from the magnet constrained the design of the diffractometer.

An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability.

RationaleDetermining the chemical constituents of natural organic matter (NOM) by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICRMS) remains the ultimate measure for probing its source material, evolution, and transport; however, lability and the fate of organic matter (OM) in the environment remain controversial. FTICRMS-derived elemental compositions are presented in this study to validate a new interpretative method to determine the extent of NOM lability from various environments.MethodsFTICRMS data collected over the last decade from the same 9.4 tesla instrument using negative electrospray ionization at the National High Magnetic Field Laboratory in Tallahassee, Florida, was used to validate the application of a NOM lability index. Solid-phase extraction cartridges were used to isolate the NOM prior to FTICRMS; mass spectral peaks were calibrated internally by commonly identified NOM homologous series, and molecular formulae were determined for NOM composition and lability analysis.ResultsA molecular lability boundary (MLB) was developed from the FTICRMS molecular data, visualized from van Krevelen diagrams, dividing the data into more and less labile constituents. NOM constituents above the MLB at H/C ≥1.5 correspond to more labile material, whereas NOM constituents below the MLB, H/C <1.5, exhibit less labile, more recalcitrant character. Of all marine, freshwater, and glacial environments considered for this study, glacial ecosystems were calculated to contain the most labile OM.ConclusionsThe MLB extends our interpretation of FTICRMS NOM molecular data to include a metric of lability, and generally ranked the OM environments from most to least labile as glacial > marine > freshwater. Applying the MLB is useful not only for individual NOM FTICRMS studies, but also provides a lability threshold to compare and contrast molecular data with other FTICRMS instruments that survey NOM from around the world. Copyright © 2015 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.

Helium recovery at the National High Magnetic Field Laboratory

Helium conservation is becoming increasingly important as helium availability is on the decline and prices are on the rise. The Florida State University National High Magnetic Field Laboratory has taken several steps over the past five years to increase the percentage of helium recovered. These include the installation of a standalone purifier, recovery flow meters, contamination meters, and a new piping system. The improvements to the recovery system have reduced the amount of helium purchased by the Mag Lab by 60% while helium usage has increased by roughly 40%. This article will provide details about the recovery system as a whole and describe some of the main components. There will also be some examples of the problems we've had to overcome, and some that we are still working on. Finally, there will be an update on the current status of the recovery system and a description of our plans for the future.