Generation and measurement of multi megagauss fields in inertial magnets

We present here the development of a facility to generate high (multi megagauss) magnetic field of 4 to 5μs rise time, using inertial magnets. The facility includes a low inductance, high current capacitor bank (280 kJ/40 kV) and an inertial magnet, which is a copper disk machined to have a keyhole in it. As the high current from the capacitor bank is discharged through the copper disk, a high magnetic field is produced along its axis, before it is destroyed by the combined effect of the dynamic loading and skin effect. A maximum peak magnetic field of 257 T is realized, when the magnet with 3.6mm inner diameter, 35mm outer diameter and 5mmlength, is powered by the capacitor bank charged to 28 kV (134 kJ). The transient magnetic field is measured using a B dot probe with an error of ±25 T. The probe in most of high field shots (> 200 T) got destroyed before recording the peak field and the trailing edge of the magnetic field. Experimental evidence of enhancement of the probe survival for longer time in copper disks using spatial non-uniform conductivity with 1mm thick SS brazed to the inner wall of the inertial magnet is also reported.     

Characterisation of the IRSN CANEL/T400 facility producing realistic neutron fields for calibration and test purposes

The new CANEL/T400 facility has been set-up at the Institute for Radiological Protection and Nuclear Safety (IRSN) to produce a realistic neutron field. The accurate characterisation of this neutron field is mandatory since this facility will be used as a reference neutron source. For this reason an international measuring campaign, involving four laboratories with extensive expertise in neutron metrology and spectrometry, was organised through a concerted EUROMET project. Measurements were performed with Bonner sphere (BS) systems to determine the energy distribution of the emitted neutrons over the whole energy range (from thermal energy up to a few MeV). Additional measurements were performed with proton recoil detectors to provide detailed information in the energy region above 90 keV. The results obtained by the four laboratories are in agreement with each other and are compared with a calculation performed with the MCNP4C Monte-Carlo code. As a conclusion of this exercise, a reliable characterisation of the CANEL/T400 neutron field is obtained.     

The High Field Project at Dresden/Rossendorf: A Pulsed 100 T/10 ms Laboratory at an Infrared Free-Electron-Laser Facility

This article describes the project to build a pulsed magnetic field user laboratory at the Forschungszentrum Rossendorf near Dresden. Using a 50 MJ/24 kV capacitor bank, pulsed fields and rise times of 100 T/10 ms, 70 T/100 ms, and 60 T/1 s should be achieved. The laboratory will be built next to a free-electron-laser-facility for the middle and far infrared (5 to 150 µm, 2 ps, cw). We describe the work which has been performed until now to start the construction of the laboratory in 2003: coil concepts and computer simulations, materials development for the high field coils, and design of the capacitor bank modules. In addition, a pilot laboratory has been set up where fields up to 62 T/15 ms have been obtained with a 1 MJ/10 kV capacitor module. It is used to gain experience in the operation of such a facility and to test various parts of it. In this test laboratory special devices have been developed for measurements of magnetization and magnetoresistance, and have been successfully used to investigate various materials including semiconductors and Heavy Fermion compounds. In particular, metamagnetic transitions in intermetallic compounds and the irreversibility field of a high-T _c superconductor have been determined. Shubnikov–de Haas oscillations have been observed in the semimetallic compound CeBiPt. Resistance relaxation has been observed to start less than 1second after the field pulse. It could be shown for the first time that nuclear magnetic resonance (NMR) is detectable in pulsed fields.     

Analysis of observations during operation of the NHMFL 45-T hybrid magnet system

The NHMFL hybrid magnet system, which was designed to produce steady field in excess of 45 T in a 32-mm, room-temperature bore, was first tested in December 1999. Since then, the system has served users of the NHMFL at the full design currents in both the superconducting outsert (10 kA) and the resistive insert (67 kA), reaching a combined field of 45.2 T. This magnet system combines both superconducting and resistive magnet technologies, which, whether taken together or separately, define new states of the art. Operating alone, the superconducting outsert has been charged repeatedly to 10 kA, corresponding to a maximum field of nearly 16 T at its 710-mm winding i.d. More recently, operation of the outsert has been limited to 8 kA as a consequence of degradation suffered during an “unprotected” quench, but insert upgrades and higher-current operation (up to 74 kA) have allowed the system to provide 45 T to users still. Because the system was designed from the outset as a facility rather than an experiment, there is a minimum of instrumentation––in fact there is none internal to the steel vessel housing the superconducting magnet. Therefore, projections of internal conditions in the superconducting magnet are deduced from detailed analysis of observations from coil voltage taps and various external temperature sensors and pressure transducers. We present these with comments regarding their value in future magnet design as well as an introduction for more complete analysis by complex computer codes.     

Conductor and joint test results of JT-60SA CS and EF coils using the NIFS test facility

In 2007, JAEA and NIFS launched the test project to evaluate the performance of cable-in-conduit (CIC) conductors and conductor joints for the JT-60SA CS and EF coils. In this project, conductor tests for four types of coil conductor and joint tests for seven types of conductor joint have been conducted for the past eight years using the NIFS test facility. As a result, the test project indicated that the CIC conductors and conductor joints fulfill the design requirement for the CS and EF coils. In addition, the NIFS test facility is expected to be utilized as the test facility for the development of a conductor and conductor joint for the purpose of the DEMO nuclear fusion power plant, provided that the required magnetic field strength is within 9 T.     

A Review of the Discrete Facility Location Problem

In this paper we attempt to classify discrete facility location problems in the right perspective and propose discrete facility location problems that include： median problems, covering problems, center problems, multi-commodities problems and dynamic problems on the basis of former research by other scholars. We consider vehicle muting location problems, inventory-location problems and hub problems as a recent research field of discrete facility location problems according to literature from the last 10 years.     

Fabrication experiences and performance tests of the coal-fired flow facility superconducting dipole magnet

The Argonne National Laboratory has designed, constructed and tested a large aperture superconducting MHD magnet for use in the coal-fired flow facility at Tullahoma, Tennessee. The magnet generates a peak on-axis field of 6 T in a MHD warm bore of 80 cm diameter at inlet, 100 cm diameter at outlet, and 300 cm effective length. The stored energy of the magnet is 210 MJ, the cold mass (4.2 K) is 131 metric tons and the ampere-turns, 13.7 × 10⁶. The final design of the magnet will be briefly introduced. Described in detail are the experiences of coil winding and coil assembly, the assembly of force-containment superstructure, assembly of magnet cryostat and results of magnet performance tests.     

Cluster test facility for superconducting tokamak toroidal magnet system development

As the step of development of superconducting tokamak toroidal magnet system, a Cluster Test system is being constructed. The test facility has two coils, called cluster test coil (CTC), in a sector position, which provides back-ground field to a test module coil (TMC). The oval-shaped TMC has a mean width of 1.5 m and a mean height of 2.0 m. And it is designed to operate at a peak field of 8 T and an average current density of 3 KA/cm²on the winding space when CTC, operated with rated current, has 7 T as a peak field with current density of 3 KA/cm². Experience on the Cluster Test will provide fabrication techniques and verifications of computer codes for future toroidal coil design principles.     

General atomic's superconducting high field test facility and initial performance

General Atomic has established a high field test facility whose primary mission is to investigate the J-B-T and stability performance margins of commercial NbTi superconductor in the 10 tesla, 4.2 K region. This work is part of the overall DOE/MFE/MAGNETIC SYSTEMS effort to provide an adequate technological base for construction of superconducting toroidal field coils for the next generation of large tokamak fusion devices. The principal components of the facility are the coil/cryostat assembly, the helium refrigerator-liquefier/compressor system, and the gaseous helium recovery and storage system. The epoxy impregnated, layer wound main background field coil generates 8 tesla within its 40 cm diameter bore. The insert background field coil was layer wound with cooling channels provided by "barber pole" mylar conductor insulation. Ten tesla is generated within its 22 cm bore. The initial performance of the facility will be discussed. Future testing calls for operating test coils with implanted heating elements to simulate mechanically induced perturbations. The normal zone growth and recovery behavior will be observed for various disturbance energies. This data will then be compared with results obtained from the transient recovery analysis developed at General Atomic.     

Operation of superconducting magnet with dilution refrigerator insert in zero boil-off regime

The combination of high magnetic field and ultra-low temperatures has proved to be indispensable for a broad range of condensed matter physics experiments. However problems with the global helium supply have raised significant concern about affordability of conventional cryogenic equipment. The latest developments in cryo-cooler technology offer a new generation of cryogenic systems in which the cryogen consumption can be significantly reduced and in some cases completely eliminated. We have demonstrated a new high magnetic field - ultra-low temperature neutron scattering sample environment system based on re-condensing technology. In our tests we have shown that the 9 T superconducting magnet, built for the ISIS facility, can be run with a dilution refrigerator insert in continuous zero boil-off regime without any additional cooling.     

Magnetic Compensation of Gravity: Experiments with Oxygen

The CEA Grenoble, through the ESEME/SBT team, has developed a new ground based facility providing magnetic compensation of gravity in oxygen. A 2T superconducting magnetic coil has been used to create the magnetic field. The installation is described. Well adapted to the heat and mass transfer studies, for example of the various boiling regimes, it permits to enhance the understanding of these phenomena in reduced gravity and gives a convenient way to reproduce space conditions on the ground. The first experimental results are presented.     

Magnet-Technology Development at the Dresden High Magnetic Field Laboratory

The Dresden High Magnetic Field Laboratory (HLD) is a user facility which provides scientists with the possibility to perform a broad range of experiments in pulsed magnetic fields. Recent progress in the magnet-technology development at the HLD has led to significant advances in achieving non-destructive pulsed magnetic fields close to the megagauss mark. Using 9.5 MJ dual-coil magnets with 16 mm bore, in 2011 a world-record field of 91.4 T has been achieved. Later 94.2 T have been reached. We report on the magnet design and performance of these magnets as well as on the design for the next generation of dual-coil magnets characterized by interchangeable inner sub-coils and improved control of the axial preload.     

Bias and uncertainty of penetrating photon dose measured by film dosemeters in an epidemiological study of US nuclear workers

A retrospective exposure assessment of 1269 study subjects was completed for use in a multi-site case-control study of the relationship between protracted workplace external radiation exposure and leukaemia mortality. The majority of exposure data result from film badge monitoring programmes at the four US weapons production facilities and a US Naval shipyard. Bias and uncertainty in reported exposures among study facilities and across time were as result of differences in incident photon energy, exposure geometry, dosemeter type and dosimetry methods. These sources of measurement uncertainty were examined by facility and time to derive bias factors (B) for normalising exposures. In conjunction with facility reported results, the bias factors provide a means to estimate the equivalent dose, penetrating to a depth of 10 mm [H(p)(10)] and the equivalent dose to the active bone marrow for use in the epidemiological study. Uncertainty was expressed as the constructed 95% confidence interval (i.e. the 2.5th-97.5th% range) of the estimated parameter. The bias factors indicate that recorded exposures provide a reasonable estimate of H(p)(10) (bias factor near unity) and overestimate equivalent dose to active bone marrow (H(T)) by a factor between 1.2 and 1.7. On average, dosemeter-response uncertainties estimated using Monte Carlo simulation were approximately +/-19 and +/-33% for H(p)(10) and H(T), respectively.     

Performance test of personal RF monitor for area monitoring at magnetic confinement fusion facility

For safety management at a magnetic confinement fusion-test facility, protection from not only ionising radiation, but also non-ionising radiation such as the leakage of static magnetic and electromagnetic fields is an important issue. Accordingly, the use of a commercially available personal RF monitor for multipoint area monitoring is proposed. In this study, the performance of both fast- and slow-type personal RF monitors was investigated by using a transverse electromagnetic cell system. The range of target frequencies was between 10 and 300 MHz, corresponding to the ion cyclotron range of frequency in a fusion device. The personal RF monitor was found to have good linearity, frequency dependence and isotropic response. However, the time constant for the electric field sensor of the slow-type monitor was much longer than that for the fast-type monitor. Considering the time-varying field at the facility, it is found that the fast-type monitor is suitable for multipoint monitoring at magnetic confinement fusion test facilities.     

Irradiation facility and physical characteristics of a 18.5 MeV/n alpha beam for cell killing experiments

A simple irradiation facility for biological experiments using a 18.5 MeV/n alpha beam has been developed. This compact irradiation facility provides a sufficiently uniform irradiation field. Physical characteristics of the alpha beam, such as a dose distribution and LET (linear energy transfer), were measured in this field. The results were consistent with theoretically calculated results.     

强磁场条件下电磁流体推进器性能的试验研究

介绍了中日合作的强磁场条件下磁流体推进器试验研究，包括试验装置的结构，试验研究的程序以及试验结果。对试验结果的初步分析表明，当磁场强度为14特斯拉，电流密度为1000安培／平方米时，推进器电磁效率可达23％，比日本“大和一号”提高10倍，电磁力密度约为10000牛顿／立方米，比“大和一号”高出一个数量级。这次试验的成功，不仅首次实现了高场强条件下磁流体推进的试验研究，为理论分析提供了颇有价值的试验数据，而且进一步演示了螺管磁体螺旋通道磁流体推进器的一些优越性，为制定该技术早日实用化的研究目标提供了可靠的依据。     

Superconductivity of the bulk MgB(2)+nano(n)-SiC composite system: a high field magnetization study

We study the effect of nano(n)-SiC addition on the crystal structure, critical temperature (T(c)), critical current density (J(c)) and flux pinning in MgB(2) superconductors. X-ray diffraction patterns show that all the samples have MgB(2) as the main phase with a very small amount of MgO; further, with n-SiC addition the presence of Mg(2)Si is also noted and confirmed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The T(c) value for pure MgB(2) is 18.9?K under 8?T applied field, while it is 20.8?K for the 10?wt% n-SiC doped sample under the same field. This points towards the increment in the upper critical field value with n-SiC addition. The irreversibility field (H(irr)) for the 5% n-SiC added sample reached 11.3, 10 and 5.8?T, compared to 7.5, 6.5, and 4.2?T for the pure MgB(2) at 5, 10 and 20?K, respectively. The critical current density (J(c)) for the 5?wt% n-SiC added sample is increased by a factor of 35 at 10?K and 6.5?T field and by a factor 20 at 20?K and 4.2?T field. These results are understood on the basis of superconducting condensate (sigma band) disorder and ensuing intrinsic pining due to B-site C substitution clubbed with further external pinning due to available n-SiC/Mg(2)Si pins in the composite system.     

Forced flow He vapor cooled critical current testing facility for measurements of superconductors in a wide temperature and magnetic field range

As superconducting materials find their way into applications, there is increasing need to verify their performance at operating conditions. Testing of critical current with respect to temperature and magnetic field is of particular importance. However, testing facilities covering a range of temperatures and magnetic fields can be costly, especially when considering the cooling power required in the cryogenic system in the temperature range below 65 K (inaccessible for LN₂). Critical currents in excess of 500 A are common for commercial samples, making the testing of such samples difficult in setups cooled via a cryocooler, moreover it often does not represent the actual cooling conditions that the sample will experience in service. This work reports the design and operation of a low-cost critical current testing facility, capable of testing samples in a temperature range of 10–65 K, with magnetic field up to 1.6 T and measuring critical currents up to 900 A with variable cooling power.     

Test results and analyses of conductor short samples for China first PF conductor

The first China PF conductor sample (CNPF1) which was made of one single cable section with hairpin configuration and without bottom joint was fabricated with Chinese NbTi strands and assembled at ENEA and CEA according to the requirements of the SULTAN test facility. The sample was equipped with temperature sensors and voltage taps at CEA according to the test program. The test program included DC performance, cyclic loading, AC loss, and MQE test. The sample exhibited a good performance which fit well with the requirement in the procurement arrangement (PA). But most of the current sharing temperature (T_cs) tests showed a suddenly voltage take-off or fast voltage transition with take-off electric field below the threshold of 10 μV/m. The temperature could be considered as quench temperature (T_q) but not exactly T_cs. At 35 kA and background field of 3.5 T, the temperature T_q was 6.94 K. Even after 2000 cycles at the condition of 6.5 T and 19 kA, the T_q remained unchanged.     

The International MegaGauss Laboratory at ISSP, The University of Tokyo

Recently, much progress has been made in generation of high magnetic fields in the International MegaGauss Science Laboratory at ISSP of the University of Tokyo. The electro-magnetic flux compression method has been improved to establish the world highest indoor-field of about 730 T. In addition to the destructive methods, a new project aiming at the non-destructive generation of both long pulsed- and 100 T-fields is progressing. The long pulse project is introduced. Not only for the highest field but also for various experiments, many kinds of coils have been developed. A microscope imaging system under pulsed fields, and miniature magnets for the X-ray measurements at the synchrotron radiation facility are also presented.