Superconducting Test Facility Research Articles

Results of preliminary testing of Blip and cancellation coils for the samsung superconductor test facility (SSTF)

The background magnet system of SSTF (Samsung Superconductor Test Facility) for KSTAR (Korea Superconducting Tokamak Advanced Research) will be equipped with a pair of main coils (MC) and a pair of blip coils (BC). The main goal of the BC is to simulate electromagnetic disturbances (1 T amplitude and 20 T/s discharge rate), expected from the KSTAR operation. The coupling losses and magnetic interaction between MC and BC will be decreased by resistive cancellation coils (CC) wound onto a fiberglass bobbin. The BC is wound with a cable in conduit conductor (CICC) packed with Nb/sub 3/Sn strands. A set of BC and CC was tested in an open type cryostat. The BC is cooled with both boiling LHe in a container and pressurized helium passing through the CICC. The BC was charged up to 6.7 kA and discharged in 50 ms. During the discharge, the maximum field variation rate corresponds to 28 T/s in the BC center and 53 T/s on the BC conductor. No quench was observed and the BC was recharged in less than 1 minute. The measured shielding current in the CC is in a good agreement with the calculated value.

The comparison of active and passive cancellation coils for SSTF

The Samsung superconductor test facility (SSTF) at SAIT (Samsung Advanced Institute of Technology, Taejon, Korea) is to be equipped with a 740 mm inner diameter superconducting split magnet (MC), which provides the background field B/sub 0/ = 8 T with ramp rate up to 3 T/s at 250 mm gap between the magnet halves. A smaller superconducting split magnet (BC) with the diameter 400 mm will be installed coaxially inside of MC to produce an additional fast variation of magnetic field with ramp rate up to 20 T/s and amplitude /spl plusmn/1 T. In order to reduce the coupling between MC and BC magnets and to avoid the MC disturbance by the fast changing stray field from BC a cancellation coil (CC) is to be provided. The comparison of an active superconducting CC charged in series with BC and a passive cryoresistive, LHe cooled CC (PCC) of which the current is induced during the fast BC discharge only has been made. The advantages of the PCC concept are discussed. The amount of LHe evaporated by PCC (charged for a short time) is estimated to be 3 to 5 liter/pulse. Recovering time for PCC is 5 to 10 min.

Fabrication of cables for the background-field magnet system of SSTF

The Korea Superconducting Tokamak Advanced Research (KSTAR) device has a fully superconducting magnet system consisting of 16 Toroidal Field (TF) and 14 Poloidal Field (PF) coils. For the test of the KSTAR cable-in-conduit conductor (CICC), an ambient magnetic field of /spl plusmn/8 T with a maximum change rate of 20 T/s is required and a background-field magnet system is being developed for the Samsung Superconductor Test Facility (SSTF). The CICC for PF1-5 is used as the conductor for background-field coils to check the validity of the PF CICC design. Two pieces of cables have been fabricated and the cable has the length of 870 m and the diameter of 20.3 mm. Pitches are 40, 80, 145, and 237 mm at each cabling stage. The void fraction of the CICC is expected to be more than 36%.

Influence of inlet pressure and mass flow rate on the temperature rise of superconducting strands in SSTF under the normal operating conditions [of KSTAR

In order to estimate the operating characteristics of the main coils, blip and compensating coils of SSTF (Samsung superconducting test facility) which will be operated under the pulsed field to simulate the operating scenarios of KSTAR (Korean Superconducting Tokamak Advanced Research), an analysis has been performed to study the influence of cryogenic parameters, such as inlet temperature, pressure and mass flow rate on the temperature margin for the main, blip and compensating coils. The temperature margin is studied under the given operating scenarios. The reduction of mass flow rate and peak temperature rise, which are strongly depending on the inlet pressure and inlet position of supercritical helium in the CICC are studied. It is noticed that the initial mass flow rate remarkably influences on the peak temperature of superconducting strands. The large mass flow rate can reduce the temperature rise when the helium inlet is installed at the high field region. On the other hand, the small initial mass flow rate results in the low peak temperature in strands when the helium inlet is located at the low field region, since the heat induced flow occurs to improve the cooling condition of the superconducting strands.

The conductors of the 50 kA superconducting transformer for SSTF

The 50 kA transformer for Samsung Superconductor Test Facility (SSTF), which will charge the Korean Superconducting Tokamak Advanced Research cable-in-conduit conductor samples for 1 s is under design. The NbTi based conductors for primary and secondary windings are described. The primary winding conductor consists of six NbTi and six stainless steel strands cabled around rectangular copper core. Such a design was previously used by Kurchatov Institute in small SMES windings. The secondary winding conductor consists of 24 subcables wrapped around and soldered to a copper strip. Each subcable consists of six NbTi strands cabled around one copper strand. NbTi strands for both primary and secondary windings are 0.85 mm in diameter. NbTi wires have 8910 6-μm filaments. Both primary and secondary winding conductors have large current and temperature margins to ensure a reliable operation of the superconducting transformer.

AC losses and heat removal in three-dimensional winding pack of Samsung superconducting test facility under pulsed magnetic field operation

The Samsung superconducting test facility (SSTF) will be operated under the highly pulsed field to simulate the operating conditions of KSTAR. An analysis has been performed to study the transient heat removal characteristics and temperature margin for the main, blip and compensating coils in the SSTF. This method is based on a quasi-three-dimensional model, which the thermal coupling of turn-to-turn, pancake-to-pancake and channel-to-channel is taken into account, to simulate the conductor temperature rise and the thermal expansion of supercritical helium due to the high AC losses under the pulsed field. The local AC losses, which include coupling loss, eddy current loss and hysteresis loss in the cable-in-conduit conductor, are estimated. The temperature margin, mass flow rate, distribution of AC losses are studied under the given operating scenario. The mass flow reduction and peak temperature rise depending on the inlet pressure and inlet position of CICC are studied. It is shown that the initial mass flow rate remarkably influences on the peak temperature of superconducting strands. The large mass flow rate can reduce the temperature rise when the inlet of helium is located at the high field region. By contrast, because of heat induced flow to improve the cooling condition of the superconducting strands, the small initial mass flow rate results in the low peak temperature in strands when the inlet of helium is located at the low field region.

The background magnets of the Samsung Superconductor Test Facility (SSTF)

The background magnet system of SSTF (Samsung Superconductor Test Facility) for KSTAR (Korea Superconducting Tokamak Advanced Research) is now under design. The main coil (MC) is split solenoids and the gap can be changed from 0 to 750 mm. The ID of MC is 750 mm. It will be wound using a CICC (cable-in-conduit conductor) designed for the central solenoid of KSTAR. The central field is 8 T at 22.5 kA when the gap is 250 mm. The ramp rate of MC is 3 T/s. A pair of blip coils will simulate (during the discharge) 1 T amplitude and 20 T/s rate electromagnetic disturbances expected from the KSTAR operation. To compensate the inductive interaction between MC and blip coils during the discharge of the blip coils, a pair of cancellation coils is foreseen. Both blip and cancellation coils (BCC) are fed in series and generate 1 T central field at 7 kA and 250 mm gap. The BCC are wound with CICC and cooled internally and externally.

The superconducting transformer of the Samsung Superconductor Test Facility (SSTF)

In the frames of designing the SSTF (Samsung Superconductor Test Facility) for the KSTAR (Korea Superconducting Tokamak Advanced Research), the 50 kA transformer charging a CICC (cable-in-conduit conductor) short sample for one second is now under design. The primary winding conductor consists of six NbTi and six stainless steel strands tabled around a low RRR rectangular copper core, which was used by Kurchatov Institute in small SMES (superconducting magnetic energy storage) windings. The secondary winding consists of 24 subcables wrapped around and soldered to a low RRR copper strip. Each subcable consists of six NbTi strands cabled around a copper strand. The strands for primary and secondary windings are 0.85 mm diameter NbTi wires with six micrometer 8910 filaments. Both primary and secondary conductors have large current and temperature margins to ensure a reliable operation of the superconducting transformer. The primary coil is placed in a cylindrical LHe vessel. The four secondary turns are glued to the outer surface of the LHe vessel. The joints between the transformer and the sample are described.

Induced voltage and alternating current loss in superconducting magnet system for SSTF

The induced voltage in the Samsung Superconducting Test Facility (SSTF) is analyzed according to the calculation of self-inductance and mutual inductance. The voltage induced by blip and compensating coils in the main coils is about 6.4 V. In order to charge the main coils, the power supply must provide the minimum voltage of 1.1 kV. The compensating coils have an influence on the field distribution. The compensating coils result in the decreasing center field about 2.67%. AC losses that include the coupling, hysteresis and eddy losses are calculated in the main, blip and compensating coils. It leads to the temperature rise of about 8 K in main coils.

ＩＴＥＲ‐ＣＳモデル・コイルとＣＳインサート・コイルの実験結果 ＣＳモデル・コイル試験装置

To demonstrate the superconducting magnet technology applicable for the construction of the International Thermonuclear Experimental Reactor (ITER), a model coil simulating the ITER central solenoid coil has been fabricated. In this way, the world's largest superconducting pulse coil with supercritical helium forced-flow cooling was realized. To test the model coil, the Japan Atomic Energy Research Institute has developed and constructed a large superconducting coil test facility named the CS model coil test facility. This facility has a large power supply system with a maximum capacity of 225MVA and a 5kW helium cryogenic system with a 1.0kg supercritical helium circulation system, which is the world's largest superconducting test facility. Design features, specifications, and performances of the CS model coil test facility are described.

The test facility for the KSTAR superconducting magnets at SAIT

SSTF (Samsung Superconductor Test Facility) has been built with the primary goal of testing the KSTAR TF (Toroidal Field) and PF (Poloidal Field) magnets as well as CICC (Cable-in-Conduit Conductor) and superconducting strands in the most relevant manner. The facility is located at SAIT (Samsung Advanced Institute of Technology) near the KSTAR project home site. Two helium liquefiers of 120 liter/hr capacity have been utilized as refrigerators demonstrating simultaneous double mode operation of refrigeration and liquefaction. A forced flow supercritical helium cooling circuit allows the test facility to be operated at temperatures down to 4.5 K. Other major SSTF components are a large vacuum vessel (6 m diameter and 7.3 m height) with liquid nitrogen temperature shield, data acquisition and control system with EPICS (Experimental Physics and Industrial Control System), current leads, and 50 kA modular power supply with fast dump quench protection circuitry. SSTF has been used for the first test-phase of KSTAR CICC sample. The current status of SSTF as the KSTAR magnet test facility for components and qualification test is presented in detail.

High field magnet program at Brookhaven National Laboratory

The magnet program at Brookhaven National Laboratory (BNL) is focussed on superconducting magnets for particle accelerators. The effort includes magnet production at the laboratory and in industry, magnet R&D, and test facilities for magnets and superconductors. Nearly 2000 magnets-dipoles, quadrupoles, sextupoles and correctors for the arc and insertion regions-were produced for the Relativistic Heavy Ion Collider (RHIC), which is being commissioned. Currently, production of helical dipoles for the polarized proton program at RHIC, insertion region dipoles for the Large Hadron Collider (LHC) at CERN, and an insertion magnet system for the Hadron-Elektron-Ring-Analage (HERA) collider at Deutsches Elektronen-Synchrotron (DESY) is underway. The R&D effort is exploring dipoles with fields above 10 T for use in post-LHC colliders. Brittle superconductors-Nb/sub 3/Sn or HTS-are being used for these magnets. The superconductor test facility measures short-sample currents and other characteristics of samples up to 1 m in length, in liquid and superfluid helium, in dipole fields above 7.5 T at 4.2 K (8.7 T at 1.9 K), and up to 25 kA. This facility performed the short-sample testing of the productions runs of NbTi wires and cables for the HERA-p and RHIC magnets, and is preparing for similar work for the LHC project. The staff also tests samples of superconductors from government laboratories and industry around the world.

Superconducting test facility of NIFS for the Large Helical Device

For development of superconducting conductors and coils, the National Institute for Fusion Science prepared a new superconducting test facility which is a combination of an electro-mechanical testing device and a large cryogenic cooling system at the new Cryogenics and Superconductivity Building at the Toki site. The cryogenic cooling system has a capacity of 250 liters of liquid helium per hour or 500 W at 4.5 K, and can also supply supercritical helium up to 50 g/s. A dc power supply generates 75 kA current at 21 V. A split-type superconducting coil generates a magnetic field of 9 T of 100 mm in width. The mechanical testing machine has a capacity of 10 MN at liquid-helium temperature. The following R & D experiments for the Large Helical Device have been done using the facility: critical current and stability measurement of helical coil conductors of which the nominal current is 21 kA at 7 T, an elasticity measurement of a helical coil, and stability measurement of a cable-in-conduit conductor.

Status report on the 12 T split coil test facility SULTAN (for NET magnets)

The third phase of upgrading of the superconductor test facility SULTAN into a split coil system (SULTAN III) is in progress. SULTAN III consists of two coil packages, each containing three concentrically mounted superconducting solenoids. Together they will produce a field of nearly 12 T between the two coil packages, inside a solenoid bore of 58 cm. The outermost 6 T coils have NbTi conductors, whereas the inner 9 T and 12 T coils are made of A-15 cables. All Nb/sub 3/Sn coils are manufactured by the react-and-wind technique. The split coil arrangement, in connection with a sophisticated sample insert containing a 50 kA superconducting transformer, will allow testing of short samples of high-current-carrying superconductors, e.g. for fusion applications. The sample insert was designed to allow changing the samples within a few hours without warming up the whole magnet system. The authors discuss the present status and potential of SULTAN III. >

Critical current measurements using 13-T split coils and 100-kA superconducting transformer (for FER)

A description is given of a large scale superconductor test facility composed of a 13-T magnetic field and a 100-kA sample current. A superconductor transformer with a 100-kA secondary conductor was fabricated as a current amplifier in order to supply the 100-kA sample current. Superconducting split coils with 100-mm clear bore diameter were fabricated, and a 13-T available field was generated by these coils. Both the 100-kA superconducting transformer and the 13-T superconducting split coils were installed in a 2-m-diameter FRP dewar for the purpose of testing large-scale superconductors. A description is given of the performance of the 100-kA superconducting transformer and the 13-T superconducting split coils as well as the results from critical current measurements of prototype conductors for toroidal coils.

The LLNL HFTF-a flexible superconducting test facility for fusion magnet development

A description is given of the High-Field Test Facility providing the capabilities needed to develop the superconducting magnet systems of next-generation fusion machines. The magnet system of the HFTF comprises six superconducting solenoids, a quench detection system and energy dump circuitry. The superconducting coil set in HFTF has been operated successfully; the magnet system was designed to be fully cryostable and has never quenched. A new cryostat for the coil set allows the magnet system to remain cold indefinitely so that the system is available on short notice to provide high fields (about 11 T) inside a reasonably large test volume (0.3-m diam). The test volume is isolated physically and thermally from the coil volume allowing test articles to be inserted and removed without disturbing the coil cryogenic volume. The separate test volume also allows reduced-temperature operation without the expense and complication of subcooling the entire coil set (about 20-t cold mass). >

Computation of force distributions in the superconducting test facility SULTAN and their comparison with experimental values

The large-bore, high field superconducting magnet of the Test Facility SULTAN (1 m diameter, 8 T) is surrounded by a number of iron parts. The different forces generated have been calculated using 3-D field maps obtained by the GFUN code. Calculated and measured values of the forces are reported. The Facility has become operational in June 1983.

The impulse voltage flashover of dielectric spacers in a helium-insulated superconducting cable model

Phototypes of a helium-insulated superconducting cables, with conductors and dielectric of realistic geometry and construction, have been subjected to impulse voltage tests in a superconducting cable test facility. Five metre lengths of a co-axial pair of tubular conductors, separated by insulating spokes, were evaluated in helium at 5.5 K and 4 bar pressure. A pressure vessel was designed and built for this purpose and was accommodated in a horizontal cryostat, 8 m in length and 305 mm bore. Cooldown of the cable was achieved by a flow of cold helium circulated from an external refrigerator. Previous work had shown that dielectric spacers made from either polypropylene or a filled epoxy resin (Stycast 2850 FT) might perform well. First flashover voltages were 96 kVp for polypropylene spacers and 94 kVp for Stycast spacers. Flashover took place across spacers in the lower region of the cable; it is suggested that particulate contamination governed flashover. Polypropylene spacers deformed during test, but Stycast spacers only broke up at flashover sites and are preferred.