Hideaki MaedaRIKEN | RIKEN AICS
Hideaki Maeda
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June 2002 - June 2016
Publications
Publications (122)
REBCO wires have high critical current density and thermal stability, and are being applied in various fields such as NMR, MRI, and accelerators. We are currently designing a 1.3-GHz LTS/HTS NMR magnet that operates in a persistent current (PC) mode. However, there are issues with using REBCO coils that need to be resolved. One problem unique to RE...
The intra-layer no-insulation (LNI) method is effective for protecting a layer-wound REBCO coil from a quench. The most influential parameter is the electrical contact resistivity
ρ
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between the conductors and the copper sheets for current bypas...
This paper reviews recent developments in ultra-high field (UHF) superconducting magnets for nuclear magnetic resonance (NMR) in the Asia region, in particular those for high-resolution NMR magnets using high-temperature superconductor (HTS) coils. In Japan, a power supply driven-mode 1.02 GHz (24.0 T) NMR magnet using a Bi-2223 inner coil was deve...
Superconducting magnets used in applications such as magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) require significant temporal magnetic field stability, which can be achieved when the MRI and NMR magnets are operated in the persistent current mode (persistent-mode) using superconducting joints. However, the ultra-high field...
This paper overviews the combined effect of winding, cool-down, and screening current-induced stresses in REBCO coils. First, a simulation method to model the circumferential stress modification effect due to the screening-current is overviewed. The simulation includes coil winding, cooling down, and coil charge up to the operating current. Second,...
This paper describes the first persistent-mode medium magnetic field (400 MHz; 9.39 T) nuclear magnetic resonance (NMR) magnet which uses superconducting joints between high-temperature superconductors (HTSs). As the ultimate goal, we aim to develop a high-resolution 1.3 GHz (30.5 T) NMR magnet operated in the persistent-mode. The magnet requires s...
This paper presents experimental results on a quench of an intra-layer no-insulation (LNI) (RE: Rare earth)Ba2Cu3O7-δ (REBCO) coil in a 31.4 T central magnetic field and simulated results on the quench. We have been designing a persistent-mode 1.3 GHz (30.5 T) nuclear magnetic resonance (NMR) magnet with a layer-wound REBCO inner coil. Protection o...
The intra-layer no-insulation (LNI) method is effective for protecting a layer-wound REBCO coil from a quench. However, a recently reported hoop stress modification (both increase and decrease) due to screening currents is a potential problem causing conductor degradation during charging. Epoxy impregnation can suppress the hoop stress modification...
It is significantly difficult to develop a superconducting joint between REBCO and low-temperature superconductors (LTS) using a solder matrix replacement technique. This is because the REBCO superconducting layer is highly corrosive to Sn. In this work, TEM observations were first conducted on the reaction interface between the REBCO layer and Sn...
We have fabricated GdBa 2 Cu 3 O y (GdBCO) jointed coated conductors (CCs) using a method in which intermediate grown superconductive (iGS) layers of (Y,Gd)Ba 2 Cu 3 O y ((Y,Gd)BCO) are formed from an YBa 2 Cu 3 O y precursor material to investigate their growth mechanism in the superconducting joint. We characterized the nanostructural evolution o...
Degradation of a REBCO coil under external magnetic fields is one of the major technical problems in the field of HTS magnet technology. A possible cause of such degradation is an inhomogeneous hoop stress distribution, or hoop stress modification (both increase and decrease), induced by the screening current. In this work, we investigate such a ho...
The design and development for a compact 1 GHz (23.5 T)-class NMR magnet are presented. The magnet uses inner coils wound with Ni alloy-reinforced Bi-2223 conductors in combination with LTS outer coils. The series-connected coils are operated in a power supply-driven mode. The total magnet size is very compact, and is comparable to that of a curren...
Superconducting magnet technology changed dramatically with the discovery of high temperature superconductors (HTS) in 1986, an event which drove the development of much higher field magnets. However, this technology paradigm shift has been delayed by as much as a decade in the case of NMR magnets. In this paper, we will provide a historical perspe...
High-field high temperature superconducting (HTS) coils, in particular REBCO coils, tend to show electromagnetic force-induced degradation and premature thermal runaways. Operation of high-field HTS coils is practicable with resistive voltage if cooling power permits. In this light, understanding coil voltage and the corresponding Joule heating pow...
Magnets using low temperature superconducting (LTS) conductors require liquid helium cooling, yet can only generate a magnetic field < 24 T. For full-fledged commerciali-zation, high temperature superconducting (HTS) conductors are preferred as they can be cooled by liquid nitrogen, enabling electric power transmission lines. Furthermore, they can...
For application to ultrahigh-field nuclear magnetic resonance spectroscopy (e.g., 30 T), we have started to develop a
$\rm REBa_{2}Cu_{3}O_{7-\delta}$
(RE123, RE: rare earth) multi-core coated conductor in which the ceramic layers (RE123 and buffer layers) are electri-cally separated to create multiple filaments. This method is called electrical...
The terminal groups of natural rubber (NR) are widely believed to play a crucial role in defining the excellent mechanical and other physical properties of processed NR products. Despite their presumed importance, the chemical structures of the terminal groups are elusive in widely used NR species with a high degree of polymerization, such as Hevea...
The no-insulation (NI) technique is a very effective protection method for REBCO pancake coils. However, it is not suitable for a layer-wound coil, which is the optimum configuration for the persistent operation and generation of a homogeneous magnetic field, since an NI layerwound coil suffers from an extremely long magnetic field delay. Such a delay...
Recently, we proposed a method of forming superconducting joints between high-temperature superconducting wires based on the incongruent melting of an intermedium, called crystalline joint by melted bulk. Using this technique with GdBa 2 Cu 3 O 7-δ -coated conductors, a superconducting joint with a critical current of 7 A at 77 K was obtained. In t...
Recently, degradation of a high-field REBCO coil due to strong electromagnetic forces, has been identified. This issue is related to a conductor movement, forming a kink in the conductor body, and hence epoxy impregnation should be effective to prevent it. The purpose of this paper is to examine the effect of epoxy impregnation on the electromagnet...
Recently, we have proposed the concept of a crystalline joint by melted bulk (CJMB) for making a superconducting connection between GdBa
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Cu
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O
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A superconducting joint technology used for high-temperature superconductors (HTS) is the key for enabling persistent operation of HTS magnets. In the present work, we have succeeded in developing a superconducting joint between REBCO-coated conductors (CCs) using a joint strap with a microcrystalline GdBCO precursor intermediate layer. Heat treatm...
The influence of an axial tensile stress under edgewise bending on the current transport property of a REBCO-coated conductor is described from the viewpoint of it being one of the major stress modes of degradation in a high field REBCO coil's performance due to electromagnetic forces. A new type of a tensile experiment for the combination of an ax...
The tensile stress tolerance of a Bi-2223 conductor has been doubled by the use of a mechanically strong Ni-alloy reinforcement material and a pre-tension technique. It is possible that, however, in the case of overheating due to a thermal runaway in a coil, release of bending strain in the mechanically strong reinforcement tape buckles the conduct...
Solid-state NMR observations of low-gamma half-integer quadrupolar nuclei, ³⁵Cl and ³⁷Cl, were demonstrated using a 24 T hybrid magnet (¹H resonance frequency of 1.02 GHz) comprised of the high-temperature (HTS) and low-temperature (LTS) superconductors, and compared with results using a 14.1 T standard NMR magnet. While at 24 T the linewidth is 1....
As Yttrium-Barium-Copper Oxide (YBCO) high-temperature superconductors have a high critical current density at high magnetic fields and high mechanical strength, they are applicable to broad areas of electric machinery. However, the YBCO magnet technology is still insufficiently developed, as the YBCO conductors are only recently commercialized. Fr...
The characteristic magnetic field delay time for a no-insulation (NI) REBCO layer-wound coil is three orders of magnitude longer than that for a NI REBCO double-pancake coil. In a NI layer-wound coil, the circumferential current firstly flows along the periphery of the coil winding, and then it diffuses from the top and bottom turns into the middle...
We have developed the world's highest magnetic-field 1,020 MHz (1.02 GHz) NMR by using a Bi-2223 hightemperature superconducting inner coil and low-temperature superconducting outer coils. High resolution 2D solid-state NMR spectra were achieved for a membrane protein by using the 1.02 GHz NMR. The NMR spectral resolution achieved using the 1.02 GH...
Conventional low-temperature superconducting (LTS) NMR magnets cannot exceed 23.5 T, as the critical current density decreases steeply beyond 23 T. The high-temperature superconducting (HTS)magnet provides a high current density even at the field above 23 T, enabling ¹H NMR at a frequency above 1 GHz. Thus, super-high-field NMR magnets are possible...
A 1.02-GHz nuclear magnetic resonance (NMR) system was successfully operated in a driven-mode over a half year. A main coil of the 1.02-GHz NMR magnet consists of a Bi-2223 high-temperature superconducting (HTS) innermost coil and low-temperature s-uperconducting outer coils. The magnet including the HTS coil was designed to operate in the driven m...
In this study, we developed a new frequency-tuning method for 700-MHz nuclear magnetic resonance (NMR) pickup coils. We determined an optimal Helmholtz-type one-turn coil, by using an electromagnetic simulator, and fabricated a pickup coil using YBa2Cu3O7-δ (YBCO) thin films. We examined the resonance frequency shift of the pickup coils obtained wi...
We succeeded in upgrading the 920-MHz nuclear magnetic resonance (NMR) superconducting magnet (21.6 T) to 1020 MHz (24.0 T) by replacing the innermost Nb3Sn coil with a (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) coil. The 920-MHz NMR spectrometer had been installed in the National Institute for Materials Science, Tsukuba, Japan, in 2001. It has been operated i...
Recently, advanced research into fine filament technology for tape-shaped superconducting-coated conductors composed of REBa2Cu3O7–δ
(RE123, RE: rare earth such as Gd or Y, 0 < δ < 1) has been carried out to improve performance in high magnetic fields by reducing the large diamagnetism of the RE123 superconducting layer. The major challenge for hig...
This paper describes a field shimming technology to obtain a spatially homogeneous magnetic field required for a high-resolution nuclear magnetic resonance (NMR) magnet under the influence of a screening current in a (RE)Ba2Cu3O7–x
(REBCO) coil. Use of REBCO inner coils is one solution to realize a super-high field (>23.5 T, 1 GHz) NMR magnet. Howe...
The use of a Bi-2223 magnet provides a high current density above 23 T, enabling a nuclear magnetic resonance (NMR) magnet to exceed a magnetic field of 23.5 T (1 GHz). The development and perspectives of super high field (LTS)/Bi-2223 NMR spectrometers that can operate at fields as high as 1.2 GHz NMR are described. © 2016 by World Scientific Publ...
Recently, we have successfully developed a 1020 MHz (24.0 T) NMR system. The NMR magnet consists of low critical temperature and high critical temperature superconducting coils. It was confirmed that the specification of the magnet satisfies the requirements for NMR measurements. In this Letter, we present some solid-state NMR spectra acquired at 2...
Use of high-temperature superconducting (HTS) inner coils in combination with conventional low-temperature superconducting (LTS) outer coils for an NMR magnet, i.e. a LTS/HTS NMR magnet, is a suitable option to realize a high-resolution NMR spectrometer with operating frequency >1GHz. From the standpoint of creating a compact magnet, (RE: Rare eart...
An advanced Bi-2223 conductor with Ni-Cr reinforcement is a likely candidate to achieve a compact super-high field nuclear magnetic resonance (NMR) magnet capable of operation beyond 1 GHz (23.5 T). However, the conductors must show both high hoop stress tolerance, typically >300 MPa, and a small screening current-induced magnetic field, both of wh...
Abstract This study reports a first successful demonstration of a single channel proton 3D and 2D high-throughput ultrafast magic angle spinning (MAS) solid-state NMR techniques in an ultra-high magnetic field (1020 MHz) NMR spectrometer comprised of HTS/LTS magnet. High spectral resolution is well demonstrated.
Abstract Synchrotron X-rays have been used to observe strain distributions in composite materials such as superconducting wires with a thickness of less than about 2 mm. In applications that employ wound coils of superconducting wire, it is necessary to understand the strain distribution within the coiled wire. Superconducting wires such as Bi2223...
We have started to develop a superconducting bridge joint between two GdBa2Cu3O7−δ (Gd123)-coated conductors, where both conductors are placed in an end-to-end arrangement on the surface of a melt-textured YBCO (including Y2BaCuO5 and YBa2Cu3O7−δ ) bulk, which acts as a superconducting medium between the coated conductors. As a first step in the de...
In the Spring of 2013, NMR spectroscopists convened at the Weizmann Institute in Israel to brainstorm on approaches to improve the sensitivity of NMR experiments, particularly when applied in biomolecular settings. This multi-author interdisciplinary Review presents a state-of-the-art description of the primary approaches that were considered. Topi...
Im Frühling 2013 versammelten sich NMR-Spektroskopiker am Weizmann-Institut in Israel, um neue Ansätze zur Verbesserung der Empfindlichkeit von NMR-Experimenten zu diskutieren, besonders im Hinblick auf Experimente an biomolekularen Systemen. Der vorliegende Aufsatz ist von vielen Autoren mit unterschiedlichem fachlichem Hintergrund verfasst worden...
The screening current-induced magnetic field (screening field) for REBCO tape coils is a critical problem for superconducting coil systems which require accurate magnetic fields, such as NMR, MRI and accelerators. The magnitude of the screening field depends on the width of a REBCO layer in a tape. Therefore, a fundamental method to reduce the scre...
We propose a Helmholtz-type probe coil that uses a high-temperature superconductor (HTS) for use as 700-MHz nuclear magnetic resonance (NMR) RF coils with a high unloaded quality factor (Qu). We analyzed the microwave resonant properties of a one-turn coil set face-to-face. The coils were made of a YBa2Cu3O7-δ (YBCO) film deposited on an r-plane sa...
We have successfully developed a 1020MHz (24.0T) NMR magnet, establishing the world's highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-Tc superconductors NbTi and Nb3Sn) outer coils and an HTS (high-Tc superconductor, Bi-2223) innermost coil, being operated at superfluid liquid hel...
High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1 GHz (23.5 T). (RE)Ba2Cu3O7-x (REBCO, RE: rare earth) conductors have an advantage over Bi2Sr2Ca2Cu3O10-x (Bi-2223) and Bi2Sr2CaCu2O8-x (Bi-2212) conductors in that...
RE-Ba-Cu-O (REBCO) layer-wound coils were operated to investigate their properties under electromagnetic forces in an external magnetic field of up to 17.2 T. While REBCO coils were successfully operated under electromagnetic forces over 200 MPa, some showed degradation after quenching. To develop high-temperature superconducting (HTS) magnets, the...
The use of REBCO coils is a promising approach to achieve super-high field NMR magnets. As the first step in this direction, we have started to develop an LTS/REBCO NMR magnet operated at 400-600 MHz (9.4-14.1 T). In this paper, based on numerical simulations, we describe a study of the thermal runaway of the REBCO innermost coil, which is one of t...
In coils wound with high-temperature superconducting (HTS) tapes, large screening currents are induced in the tape by the radial component of the magnetic field. Furthermore, when a transport current is supplied to the HTS tape under a magnetic field, the total current (which consists of the transport and screening currents) flows inhomogeneously....
After the commercialization of REBCO-coated conductors, a number of REBCO coils have been fabricated targeted toward various magnet applications. One of the major technological problems is degradation in coil performance such as in the critical current, due to delamination of the REBCO-coated conductors in epoxy impregnated windings. A number of ef...
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, Clar...
Development for superconducting wires of materials such as Nb3Al and the high-temperature superconductors (HTS such as REBCO, Bi2223, and Bi2212) has been carried out for high-field magnet applications. It is known that these types of wire exhibit very different characteristics and performance for different applications. The development of Nb3Al wi...
This paper clarifies the basic mechanism of self-healing from natural thermal runaway for uninsulated REBCO pancake coils. Based on the numerical simulation and experimental results, it is demonstrated that current flow patterns for an uninsulated REBCO pancake coil sequentially changes with the overcurrent value. Due to natural thermal runaway abo...
One apparent shortcoming of REBCO conductor coils is an extremely low fraction of conductor in the coil winding, as the REBCO conductor is as thin as 100–150 μm, comparable to the insulation thickness. If we wish to achieve high overall current densities for REBCO coils, the insulation thickness on REBCO conductor must be substantially reduced. The...
REBCO superconductors are promising for coil applications such as MRI, NMR and Superconducting Energy Storage System One apparent shortcoming of REBCO conductor coils is an extremely low fraction of conductor in the coil winding, as the REBCO conductor is as thin as 100-150 μm, comparable to the insulation thickness. If we wish to achieve high over...
REBCO high temperature superconductors are promising for various superconducting coil systems such as MRI, NMR and Superconducting Energy Storage Systems. However, REBCO coils sometimes shows thermal runaway, resulting in meltdown of the coil in the worst case. In this paper, we investigate the effect of thermal grid method, in which heat channel o...
A practical size epoxy impregnated single pancake coil, 30 mm in inner diameter and 73 mm in outer diameter, was fabricated using a polyimide electro-deposited (PIED) YBCO-coated conductor. The voltage-current characteristics achieved at 77 and 4.2 K reached coil critical currents without any degradation of coil performance. We reported similar res...
RE-Ba-Cu-O (REBCO) high-temperature superconducting conductors have the advantage of high critical current density in a magnetic field above 10 T as well as tolerance to high tensile stress. REBCO high-temperature superconducting coils are expected to be applied to superconducting magnets using cryocoolers. While epoxy-resin-impregnated superconduc...
During the excitation of REBCO coils, premature thermal runaways occur. In the worst case, the conductor melts down. Premature thermal runaway is caused by partial conductor degradation in the coil winding, which sometimes occurs in coils fabricated from REBCO-coated conductors. In this paper, we have examined the use of a “thermal grid” method usi...
REBCO conductors were commercialized only recently in 2009 and therefore the magnet technology for REBCO conductors remains undeveloped. The major technological problems for REBCO coils encountered thus far are (a) degradation in the superconducting performance for mechanical reasons, (b) difficulty in protecting the magnet in the case of a super-n...
REBCO conductors were commercialized only recently in 2009 and therefore the magnet technology for REBCO conductors remains undeveloped. The major technological problems for REBCO coils encountered thus far are (a) degradation in the superconducting performance for mechanical reasons, (b) difficulty in protecting the magnet in the case of a super-n...
Conventionally, LTS magnets have been used in NMR systems. However, through use of HTS materials for the superconducting magnets, it will be possible to reduce the size of the magnet significantly. Reducing the size of the magnet will allow, high magnetic field NMR systems to be installed in a much wider range of environments, and thus widen their...
Achieving a higher magnetic field is important for solid-state nuclear magnetic resonance (NMR). But a conventional low temperature superconducting (LTS) magnet cannot exceed 1 GHz (23.5 T) due to the critical magnetic field. Thus, we started a project to replace the Nb(3)Sn innermost coil of an existing 920 MHz NMR (21.6 T) with a Bi-2223 high tem...
Though YBCO coils are stable against transient disturbances such as conductor motion, they suffer from thermal runaway at a current below the coil critical current due to continuous local disturbances attributed to partial degradation of the conductor in the coil winding. Continuous heat generation in the degraded layer induces thermal runaway in a...
A nuclear magnetic resonance (NMR) system using a high-temperature superconducting (HTS) magnet and a probe with an HTS radio frequency coil is currently under development. The HTS NMR magnet is expected to reduce the volume occupied by the magnet and to encourage users to install higher field NMR systems. RE-Ba-Cu-O-coated (REBCO-coated) conductor...
Degradation of the epoxy impregnated YBCO coil performance is due to tensile radial stress concentration on the outer edge of the conductor during cool down. This stress acts as a cleavage stress and opens the conductor edge, fracturing the YBCO layer. The fracture propagates to another edge of the conductor, resulting in degradation of the coil pe...
YBCO-coated conductors are promising for NMR
magnets. Their axial strength is up to 700 MPa and this allows for dramatically smaller high current density
magnets. One of the major problems of YBCO-coated conductor coils is screening current induced in the coil during charging. The screening current reduces the central magnetic field by <20% and c...
High-temperature superconducting (HTS) magnets are believed to be a practical option in the development of high field nuclear magnetic resonance (NMR) systems. The development of a 600 MHz NMR system that uses an HTS magnet and a probe with an HTS radio frequency coil is underway. The HTS NMR magnet is expected to reduce the volume occupied by the...
Cleavage strength for an YBCO-coated conductor at 77 K was investigated with a model experiment. The nominal cleavage strength for an YBCO-coated conductor is extremely low, typically 0.5 MPa. This low nominal cleavage strength is due to stress concentration on a small part of the YBCO-coated conductor in cleavage fracture. Debonding by the cleavag...
NMR magnets using high- T <sub>c</sub> superconductors (HTS) are currently by several organizations designed to generate high fields exceeding 25 T. In such designs, the HTS are used for the inner coils, and the outer coils consist of NbTi and Nb<sub>3</sub>Sn wires. A ReBCO wire with a Hastelloy substrate has excellent critical current performance...
Because of their high critical fields, high- T <sub>c</sub> superconductors (HTS) are considered to be the only solution to dramatically increase the highest fields of NMR magnets. We have successfully demonstrated that a 500 MHz HTS/LTS NMR system with a Bi-2223 innermost coil could be used for solution NMR in a driven-mode operation. As the next...
Screening current induced in a YBCO-coated conductor coil causes two major problems; (i) reduction in the central magnetic field and (ii) temporal magnetic field drift due to flux creep. They constitute disadvantages for YBCO coil applications such as NMR, MRI, accelerator and high field magnets. The second problem is effectively suppressed by curr...
Coated conductors are promising candidates for the construction of high-field magnets. In solenoid magnets built with coated conductors, large screening currents are induced in the superconducting layer by the radial component of the magnetic field. The screening currents generate a screening field that reduces the central magnetic field and affect...
Now that YBCO-coated conductors have been commercialized, a number of YBCO coils have been developed. However, their basic performances have not been systematically investigated so far. Here, we demonstrate that of a YBCO double pancake coil. The critical current of an epoxy impregnated YBCO double pancake coil was substantially degraded, i.e. the...
Using high-T<sub>c</sub> superconductors (HTS) is considered to be the only solution to dramatically increase the highest fields of NMR magnets because of their high critical fields. However, it is not easy to apply HTS to an NMR spectrometer (HTS-NMR) because a persistent-mode operation with HTS cannot satisfy the field stability of 0.01 ppm/h at...
A numerical simulation method which deals with the screening current-induced magnetic field for YBCO coils, including the self field effect induced by the transport current, has been developed. The simulation agrees well with the experimental results for an YBCO solenoid. Based on the numerical simulation, the effect of coil shape on the screening...
(33)S nuclear magnetic resonance (NMR) spectroscopy is limited by inherently low NMR sensitivity because of the quadrupolar moment and low gyromagnetic ratio of the (33)S nucleus. We have developed a 10 mm (33)S cryogenic NMR probe, which is operated at 9-26 K with a cold preamplifier and a cold rf switch operated at 60 K. The (33)S NMR sensitivity...
We have begun a project to develop an NMR spectrometer that operates at frequencies beyond 1 GHz (magnetic field strength in excess of 23.5 T) using a high temperature superconductor (HTS) innermost coil. As the first step, we developed a 500 MHz NMR with a Bi-2223 HTS innermost coil, which was operated in external current mode. The temporal magnet...
The effect of current sweep reversal on the temporal drift in magnetic field intensity for a Bi-2223 solenoid was investigated by experiment and using numerical simulation. Current sweep reversal, by as small as 1% of the peak current, was found to stabilize the drift in magnetic field intensity for a Bi-2223 tape solenoid. The field drift was due...
The screening current-induced magnetic field in the (Bi,Pb)2Sr2Ca2Cu3Ox (Bi-2223) insert coil proposed for a beyond 1 GHz nuclear magnetic resonance (NMR) spectrometer may generate a long-term field drift, resulting in a loss of field-frequency lock operation and an inability to make high resolution NMR measurements. The measured screening current-...
With the goal of a (33)S nuclear magnetic resonance (NMR) probe applicable to in vivo NMR on taurine-biological samples, we have developed the (33)S NMR cryogenic probe, which is applicable to taurine solutions. The NMR sensitivity gain relative to a conventional broadband probe is as large as 3.5. This work suggests that improvements in the preamp...
An NMR spectrometer over 1 GHz requires the contribution of high-T<sub>c</sub> superconductors(HTS). However, a persistent-mode operation with HTS cannot satisfy the field stability of 0.01 ppm/h at present. This is a great barrier for applying HTS to an NMR magnet. To overcome this problem, a new project was undertaken in Japan in October 2006. In...
We have commenced a project to develop a beyond-1 GHz solution NMR spectrometer using a HTS coil. Due to a small residual resistance present in the HTS conductor and joint resistance between conductors, a stable persistent current sufficient for NMR measurements is unlikely. Therefore, a current has to be supplied to the HTS coil from an external p...
We have developed a novel superconducting joint method for Nb<sub>3</sub>Al conductors, which can be used for the innermost coil of a 1-GHz NMR magnet. First, we optimized the joint property; then, we prepared a closed circuit with an NbTi coil and a pair of Nb<sub>3</sub>Al-NbTi joints; finally, we determined the joint resistance by using the fiel...
The innermost coil of a new high-field NMR magnet such as a 1-GHz NMR magnet is designed by using a new superconductor. It is therefore important that a superconducting joint between the new superconductor and the NbTi conductor was developed. We have developed a new superconducting joint method for the Nb<sub>3</sub>Al conductor, which is expected...
This paper describes the development of a 4 K cryogenic probe for 500 MHz Nuclear Magnetic Resonance
(NMR) analyses. As thermal noise is proportional to the square root of the RF coil temperature, sensitivity of a 4 K probe is expected to be double that of conventional 25 K probes. The 4 K probe apparatus consists of a closed‐cycle cooling system,...
A previous report by Kelly et al. [J. Am. Chem. Soc. 124 (2002) 12013] indicated that the ionic conductivity of aqueous solution produces a significant contribution to the sensitivity loss in high-resolution NMR equipped with a cryogenically cooled probe. The loss in a sample solution contains two contributions: one from the ionic conductivity and...
The first 920 MHz high-resolution NMR (nuclear magnetic resonance) magnet was successfully installed at the Tsukuba Magnet Laboratory of the National Institute for Materials Science. A persistent operation at 21.6 T has continued since April 2002 without any problems. Excellent field stability of 0.31 Hz/h was observed from December 2002 to January...
The feasibility of closed‐cycle 4.5 K cooling has been demonstrated for a cryogenically cooled probe for the world highest magnetic‐field 920 MHz Nuclear Magnetic Resonance
(NMR) operated at the National Institute for Materials Science (NIMS), by means of the following model experiments. The cooling system with a cooling capacity of 4.55 W compris...
This paper describes the development of a conductive-cooled superconducting magnet that uses no cryogen, such as liquid helium or liquid nitrogen. First, the history of the development is introduced. A conductive-cooled superconducting magnet was realized in the late 1980s for the first time and was commercialized about 10 years ago. The technical...
