The system integration of a 36 T high field resistive-superconducting hybrid magnet system which will be used primarily for NMR studies is being finalized at the National High Magnetic Field Laboratory in Tallahassee, Florida. The hybrid magnet consists of a 23 T resistive insert coil set nested inside of a 13 T superconducting coil wound with high JC Nb3Sn/Cu cable-in-conduit conductor. The resistive and superconducting coils are connected electrically in series and operate at 20 kA. The combined system will enable 1-ppm level uniformity in a 1 cm DSV for condensed-matter NMR at a record level of 1.53 GHz. The resistive insert has four concentric Florida-Bitter coils and operates at 14 MW. The superconducting outsert operates with forced flow supercritical helium at 4.5 K and 3.5 bar. The superconducting protection system consists of two fully independent circuits, one employing voltage averaging comparisons between winding layers and the other a voltage comparison with a co-wound coil. Initial magnet testing of the resistive coils has been completed. The superconducting cold mass has been cooled to 4.5 K and the system is being prepared for combined hybrid magnet testing.

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.

The cable-in-conduit conductors (CICC) designed for the National High Magnetic Field Laboratory (NHMFL) and Helmholtz Zentrum Berlin (HZB) Series-Connected Hybrid magnets have been qualified. The superconducting coils for the hybrid magnets consist of three CICC configurations graded for different designed fields. Representative samples with the same Nb3Sn type, cable pattern, and CICC configuration were fabricated and the current sharing temperature (TCS) and critical current were measured with the intention to quantify the level of degradation from cyclic, transverse electromagnetic loads. In addition the intrinsic strain for the CICC was determined by measuring the TCS and IC as a function of applied longitudinal strain. Two conductor grades, for the middle and low fields regions of the coil (MF and LF), are tested at the NHMFL in a split magnet that is equipped with a system that can apply up to 250 kN force in a direction longitudinal to the samples. The samples are hydraulically connected to a cryogenic system which delivers temperature controlled supercritical helium. The reduction in TCS from electromagnetic load cycling is shown to be insignificant and measurements as a function of strain shown that the MF and LF CICC have intrinsic strains of approximately 0.65% and 0.70% respectively.

The National High Magnetic Field Laboratory (NHMFL) is designing two series-connected hybrid magnets, one for the Helmholtz Center Berlin (HZB) and the other for the NHMFL. The one for HZB has a horizontal, conical warm bore with a 30 degree opening angle for neutron scattering experiments. The one for the NHMFL has a 40 mm diameter vertical warm bore with a cylindrical profile. The design of the HZB cryostat will be completed this year. In this paper the design of the HZB cryostat is presented. The results of a structural analysis performed for normal operation and for fault scenario are discussed. The main features of the NHMFL cryostat are described shortly in the introduction section.

Two Series Connected Hybrid (SCH) magnets are under construction at the National High Magnetic Field Laboratory. In the SCH system, consisting of a resistive insert and a superconducting outsert, the outsert superconducting coil is wound with Cable in Conduit Conductor (CICC) and cooled with forced-flow supercritical helium at 4.5 K. The forced-flow helium is supplied from a helium refrigerator. In the design of the cryogenic system for the series-connected hybrid, the possible failure of the magnet system should be considered and the cryogenic system should be safely protected in the event of failure. In the SCH system, a protected quench of the superconducting magnet, a loss of vacuum in the cryostat and an unprotected quench were analyzed. Active venting valves, safety valves and burst disks are used for the protection of the cryogenic system and cryostat in the case of the occurrence of failure modes. The design of the safety protection system and the analysis results in the failure modes are discussed.

A parametric study has been conducted to quantify the effect in performance of cable-in-conduit conductors (CICC's) to changes in cable and conduit design. Measurements of current sharing temperature and critical current as a function of electromagnetic cycling and longitudinal strain were systematically performed on CICC's with common Nb3Sn internal tin strand. The designs varied in void fraction (0.30 or 0.36), long or short cable twist pitch, cable core patterns (6 around 1 or triplet), and conduit material property (stainless steel 316 or Haynes 242). Measurements were performed at the NHMFL in a test facility for conductor characterization with capability to 12 T, 20 kA, and 250 kN axial tensile load now modified to deliver temperature controlled supercritical helium to the CICC samples.

A parametric study has been conducted to quantify the effect in performance of cable-in-conduit conductors (CICC's) to changes in cable and conduit design. Measurements of current sharing temperature and critical current as a function of electromagnetic cycling and longitudinal strain were systematically performed on CICC's with common Nb3Sn internal tin strand. The designs varied in void fraction (0.30 or 0.36), long or short cable twist pitch, cable core patterns (6 around 1 or triplet), and conduit material property (stainless steel 316 or Haynes 242). Measurements were performed at the NHMFL in a test facility for conductor characterization with capability to 12 T, 20 kA, and 250 kN axial tensile load now modified to deliver temperature controlled supercritical helium to the CICC samples.Small differences have been measured in the current sharing temperature between CICC's with stainless steel jackets. However dramatic improvements in Nb3Sn of over 1 K have been found when Haynes 242 is used as the jacket material.

A pair of binary current leads has been constructed with a nitrogen vapor cooled resistive section and a stainless steel shunted HTS lower section. These leads are intended as replacement leads for the NHMFL 45 T Hybrid and also serve as half-current prototypes for the 20 kA leads foreseen for the Series Connected Hybrids that are under development at the NHMFL. An amount of liquid nitrogen is maintained in a reservoir at the bottom of the resistive section such that vapor flow is determined by self- demand. The liquid nitrogen delivery system and properties of the vapor cooled section of the leads are described. A comparison is made between the measured and calculated properties of the resistive section in steady state and transient conditions.

MS&T is funded by the Advanced Photon Source (APS) at the Argonne National Laboratory to demonstrate the feasibility of short-period Nb3Sn undulators. To that end we are developing a 30-period magnet consisting of an upper and lower yaw mounted around a mock beam liner. The primary challenges that are addressed with this demonstration are current density in the windings, maximizing thermal insulation between the windings and beam tube while minimizing their distance, and finding a suitable assembly method.

The National High Magnetic Field Laboratory (NHMFL) has embarked on an innovative program to develop a number of Series-Connected-Hybrid magnetic systems. In this novel concept, a set of resistive coils (insert) and a set of superconducting cable-in-conduit conductor (CICC) coils (outsert) are electrically driven in series, rather than independently as in previous hybrid systems. Presently NHMFL is working on 3 different projects. The first, funded by the National Science Foundation (NSF) with an $11.7 million grant, is related to the construction of a cylindrical-bore Series-Connected Hybrid (SCH), for high field nuclear magnetic resonance (NMR), condensed matter physics, biology and chemistry, to be located at the Magnet Lab's Tallahassee location. The second, funded by the Hahn-Meitner Institute (HMI) in Berlin, relates to the engineering design for a horizontal bore Series-Connected Hybrid to be used in a neutron diffraction experimental system. Finally, the third, also funded by NSF, is a conceptual and engineering study for an SCH that would be used for neutron scattering experiments at Oak Ridge National Laboratory's Spallation Neutron Source (SNS), similar to the HMI version. Because of the main points in common between the 3 different systems, our final goal is to develop a superconducting magnetic system suitable for the 3 applications. We believe this is possible for the magnet although, due to the different field/bore orientations, some differences in the mechanical design of the cryostat and resistive inserts will exist. In this paper we will give an overview of the R&D strategy devised to develop these superconducting magnetic systems, together with a report on the present status of such program.

An Nb3Sn planar undulator demonstration magnet is under development at the NHMFL. Key technological aspects include a 15 mm period, a target of 0.8 T on the beam and a beam tube that is thermally isolated from the windings. Two yoke assembly procedures are explored. First, a modular approach in which each racetrack is wound, reacted and impregnated separately before assembly with iron pole pieces and the creation of joints between the racetracks. The second approach is based on the more traditional single-piece yoke on which the conductor is wound on a fully iron yoke, followed by heat treatment and impregnation of the entire assembly. Each approach is used to build a 10-racetrack coil; both coils are tested at 4.2 K in liquid helium. Results of the coil tests are discussed, as well as joint development and testing, leading to a choice of assembly method for the demonstration magnet.

With the intention to develop a technology suitable for a 2.4 m magnetic length, superconducting undulator with 0.8 T on the beam and a 15 mm period for the IXS beam line at the Advanced Photon Source at the Argonne National Lab, USA, a 0.6-m Nb 3 Sn undulator demonstration magnet is under development at the NHMFL. The intent is to investigate the applicability of Nb 3 Sn superconductor, in combination with soft magnetic materials, for a 15 mm period planar superconducting undulator. The demonstration requirements include a peak undulator magnetic field of at least 0.8 T and a vertical stay-clear aperture for the beam of at least 7 mm. In concept, the beam tube will be thermally isolated from the windings and operated at LN 2 temperature to promote system reliability. Liquid helium and nitrogen reservoirs provide conduction cooling and the former also acts as a basic structural element. A brief description of a design is presented. A comparative study of fully and partly iron yokes and their effect on the required current density is performed. The results have implications for the yoke assembly procedure. Finally, a new yoke-winding geometry is presented

The National High Magnetic Field Laboratory (NHMFL) has identified as one of its next high-field persistent-magnet targets a 21 T superconducting magnet system to be used in a Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometer. The required fundamental parameters of a 21 T central field and 110 mm warm bore diameter are similar to those already successfully demonstrated in the NHMFL's Ultra-Wide Bore 900 MHz Nuclear Magnetic Resonance magnet system. However, there are several ancillary requirements of the FT-ICR spectrometer that require technical attention such as fringe field restrictions requiring shielding, length of uniformity zone, magnitude of inhomogeneity, horizontal orientation of the magnet axis and a limitation on the length of the cryostat. This paper describes the overall system requirements, features and status of the superconducting magnet conceptual design proposed for meeting these requirements