We successfully upgraded the 920 MHz NMR superconducting magnet (21.6 T) to 1020 MHz (24.0 T) by replacing the innermost Nb3Sn coil with (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀ (Bi-2223) one. The 920 MHz NMR system had been installed in National Institute for Materials Science (NIMS), Tsukuba, Japan on 2001. It had been operated by the persistent mode for six years. The upgrading project started on 2006 and would complete on 2011. Unfortunately the magnet was seriously damaged by the Great East Japan Earthquake on March 2011. After more than two year restoration and additional improvements of current leads, JT heat exchanger, and power supply system, the magnet was cooled down to below 1.8 K in August 2014. The newly installed Bi-2223 innermost coil is connected to Nb₃Sn and NbTi coils in series. Because a superconducting joint technique has not been established for Bi-2223, the HTS/LTS NMR system is operated by a driven mode, i.e. the magnet current is always supplied from a DC power source. The magnet successfully generated 24.0 T, corresponding to 1020 MHz, on October 2014. To achieve the required homogeneity and stability of the magnetic field, not only superconducting and room temperature shim coils but also ferromagnetic shims were used. Finally we achieved the field homogeneity of < 1ppb and field stability of < 1 ppb/10h under the operation of field frequency lock system, which are sufficient for high resolution NMR measurement.

This work is supported by the System Development Program for Advanced Measurement and Analysis (SENTAN) (Program-S), Japan Science and Technology Agency (JST).

Recently, the NI (no‐insulation) HTS (high temperature superconductor) winding technique has been actively studied to enable an HTS magnet highly compact, self‐protecting, and mechanically robust to a level that has never been achieved by the conventional insulated counterpart. Due to the intrinsic charging delay of an NI magnet, applications of the NI technique may be limited to “slow ramping” DC magnets; NMR magnets, typically energized over a few hours, are therefore a potential candidate of the NI technique. This presentation focuses on two issues relevant to NI HTS NMR magnets:
1) selfprotecting operation of high‐current‐density (>400 A/mm2) NI magnets;
2) mitigation of the screening current induced field (SCF) in NI magnets by the so‐called “field‐shaking” technique.
Two latest NI all‐ REBCO magnets are introduced: 1) a 7‐T/78‐mm NI REBCO magnet, designed and constructed by MIT that was demonstrated to be self‐protecting upon a quench at a coil current density of 870 A/mm2 in an over‐current test run in a bath of liquid helium (LHe) at 4.2 K; and 2) a 26‐T/35‐mm NI REBCO magnet, designed by MIT and constructed by SuNAM, that successfully generated 26 T in LHe at 4.2 K, a record
high in magnetic fields by all‐HTS magnets. Also presented are field‐shaking test results of NI REBCO coils, which demonstrate that the field shaking may be particularly effective on REBCO conductors having extremely thin (1~2 um) superconductor layers. Followed by the technical issues, a roadmap toward >1.5‐GHz NI all‐HTS NMR magnets is presented with focuses on new ideas, technical challenges, and
cost estimation.

The work presented here is chiefly performed while S. Hahn was at his former institute, the Francis Bitter Magnet Laboratory at MIT, and is partly supported by the National Center for Research Resources, the National Institute of Biomedical Imaging and Bioengineering, and the National Institute of GeneralMedical Sciences, all of the National Institutes of Health under Award Number (R01RR015034 and R21EB013764) and the KBSI grant (D35611) to S.‐G.L. and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & FuturePlanning (NRF‐2014R1A6B1A01048313).

A new innovative Whole Body 11.7 T MRI magnet which is currently being manufactured at Alstom Belfort as part the Iseult/Inumac project, a French-German initiative focused on very high magnetic-field molecular imaging.
It will be installed at the end of this year in a neuroscience research center with other very high field MRI equipment, operating in France at CEA Saclay since November 2006.

This actively shielded magnet system, manufactured from NbTi superconductor, will generate a homogeneous field level of 11.75 T within a 90 cm warm bore;operating at a current of 1483 A, in driven mode, in a bath of superfluid LHe at 1.8K. The stored energy is 338 MJ and the inductance 308 H. The cryostat has external dimensions of 5 m in diameter and 5.2 m in length, for a total magnet weight of 132 tons.

The main coil constructed from a stack of 170 double pancakes of 2 meters diameter with a finished height of 4 meters and 50 tones in weight has been completed within required tolerances. The two shielding coils, vacuum impregnated solenoids of 4 meters in diameter and 10 tons in weight, have also been completed within tolerances. A crack has been discovered inside the 2 meter diameter mandrel of the cryogenic correction coils. A new is under manufacture with delivery foreseen for mid-2015. The Main coil and shielding coils have then been integrated inside the helium vessel and the assembly of thermal shield and vacuum vessel started with completion expected by the end of 2015. The magnet will be serviced by a separate cryogenic and electrical facility; the installation of this external equipment will be completed mid-2015 when the first phase of the commissioning will start. Full tests and commissioning of the magnet at 1.8K are expected at NeuroSpin at the end of 2016.

Proton therapy is a rapidly developing technique for cancer treatment, since the radiation dose delivered to the target volume is maximized and the dose to surrounding healthy tissue is minimized. The three-dimensional scanning-irradiation method is performed by means of fast sweeper magnets for transverse scanning and the scanning in depth of the tumor is performed by fast energy changes in steps of 1% in less than 100ms. Therefore high magnetic field ramping speed is necessary. To aim the scanning beam from all directions to the tumor in the patient, the last part of the beam transport and scanning system are mounted on a rotatable gantry. The last bending magnet in the gantry is a major component that drives the weight, footprint and costs of the whole machine. Superconducting magnets have the potential to reduce the facility weight, volume and costs, maintaining at the same time a large scanning field size.
In this work a conceptual design of a 90° bending superconducting magnet for future compact iso-centric gantries is presented. The dipole geometry consists of racetrack coils to keep the magnet manufacturing as easy as possible. The design has been optimized to produce a field homogeneity of around 1% over a good field region (GFR) of 250 x 250 mm2, featuring also a modest harmonic distortion and a low peak field in the winding pack. Special attention was given to the design of a suitable superconducting cable for this geometry. It must be capable of minimizing the losses during the fast energy sweeps and guaranteeing a safe temperature margin during the operation.

High field compact superconducting magnets with wide bore access are needed by the research community in physical and life sciences to explore new areas in nanoscience, nanotechnology, and bioscience and materials research and will require new innovations in magnet technology and superconducting materials. This paper presents an update on the recent development and commissioning of a new class of high field wide bore superconducting magnets for research applications. The first one to be completed is the Low Temperature superconducting (LTS) 19T with 150mm bore magnet system for the Dresden High Field laboratory (HLD), the second system is the (LTS) 15T outsert with 250mm bore magnet system for the National High Magnet Field Laboratory (NHMFL) 32T all superconducting user magnet. Both systems operate at 4.2K, the temperature of liquid helium at atmospheric pressure. The new magnets are compact in size and realized by exploiting the advanced high-performance Re-stacked Rod Process (RRPTM) low temperature Niobium Tin (Nb3Sn) superconducting wires as well as new innovation in magnet engineering including the processing and integrating of large RRP coils, management of high stressed coils and the large stored energy in the magnet under quench conditions.

A project to develop the fundamental technologies for accelerator magnets using high Tc superconductors is currently underway. In this project, the conceptual design studies of fixed field alternating gradient (FFAG) accelerators for carbon cancer therapy and for accelerator-driven subcritical reactor were carried out. To establish technologies for cryocooler-cooled HTS accelerator magnets wound with coated conductors, a downscaled model magnet-system for the FFAG accelerator has been developed. The model magnet consisting of multiple coils with complicated shapes, including a negative-bend part or a three-dimensional bent part, was designed to demonstrate generation of the asymmetrical magnetic field on the midplane of the magnet bore as sort of the FFAG accerelator magnet. One issue is how to wind coils for the accelerator magnets by using tape-shaped coated conductors, which have anisotropic bending flexibility between the flatwise and edgewise directions. It is necessary to consider a method of winding the complicated shaped-coils while preventing degradation of the superconducting properties of the coated conductors. A part of the coils for the model magnet was wound using YBCO coated conductors with a length of about 100 m and excited to measure their voltage-current characteristics in liquid nitrogen. From the characteristics of the coil throughout an electric field range down to 10-9 V/cm, the characteristics before and after impregnation were approximately the same, demonstrating that the superconducting properties were not degraded. This paper also describes the assembling and the testing procedures of the model magnet.

This work was supported by the Japan Science and Technology Agency under the Strategic Promotion of Innovative Research and Development (S-Innovation) Program.

A 360 mm room temperature bore cryogen-free superconducting magnet (CSM), consisting of Nb₃Sn coils and NbTi coils, for a hybrid magnet (HM) has generated 8.5 T within 1 hour and the maximum magnetic field of 9.5 T. However, the magnetic field in the hybrid mode has been limited to 27.5 T because of a cooling problem. Therefore, we improved the CSM to upgrade the magnetic field higher than ever.
For the improvement of the cooling problem, Nb₃Sn coils were replaced, and a thermal conduction was improved between coils and a 4K-GM cryocooler. In addition, support structures with a tensile strength above 80 kN and a spring support were adopted against the magnetic force, to support self-weight of coils and to absorb stress caused by thermal contraction difference between each coils.
After the improvement, the CSM generated 9.5 T within 1 hour and the maximum magnetic field of 9.7 T in a 360 mm room temperature bore. The HM, consisting of the outer CSM and an inner water cooled magnet, also generated 28 T in a 32-mm room temperature bore when the CSM was operated at 9.0 T.

MgB2 is an attractive superconductor for application in MRI magnets because of its good critical current performance in the 10-30 K range and relatively low cost. The higher operating temperature opens the door to viable, cryogen free and thermally stable large scale superconducting magnets. This offers a step change in MRI superconducting magnet technology which is traditionally based on liquid He cooled Nb-Ti coils.

A multi-turn, multi-layer solenoid coil was tested in a variable temperature environment from 5 K to 30 K in order to validate the conductor’s long length critical current and n-value performance. The react and wind test coil was driven in constant current mode. The test coil had an inner diameter of 0.5 m and consisted of 30 layers thus totalling a 684 m wire length. The 3 mm x 0.5 mm MgB2 wire consisted of 19 twisted MgB2 filaments in a Nickel matrix, with a Cu strip of same size soldered to it. The wire was insulated with a polyester braid.

The reacted wire was successfully wound and impregnated without imparting noticeable strain damage to the MgB2 filaments as demonstrated by the consistency between measured long length wire performance of the coil and the short sample data from the wire manufacturer. The wound coil was instrumented with voltage taps in a way to obtain long length critical current and n-values based on the entire length of the coil as well as discrete coil layers. Critical current was determined using a 0.1 μV cm-1 electric field criterion. The critical current of the first coil layer which was 21.6 m in length was measured to be 390 A at 5 K, 290 A at 15 K and 145 A at 25 K. The n-value at 5 K was measured to be 80, decreasing to circa 35 above 10 K.