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Due to global issue of energy shortage, alternative energy such as solar and wind energy has to be introduced to the commercial electricity grid. A hybrid energy storage system which is able to convert unstable alternative energy into constant electricity has been proposed. The hybrid energy storage system is composed of hydrogen system and SMES system. This research concerns on the issue of continuous operation of SMES system by introducing a threshold voltage range into the SMES control method. This control method was applied to an SMES coil in a 1-kW-class hybrid energy storage model system. Using the control method, we could restrain the temperature rise of the SMES coil. An experiment has been carried out to confirm the effectiveness of the control method in continuous operation of the hybrid energy storage system. The fluctuation output of a solar power generator was appropriately compensated by electrolyzer and SMES systems.

MgB2 round wires are now commercially available with applicable critical current density in magnetic fields up to 5 T. One of the promising applications using MgB2 is a superconducting magnetic energy storage (SMES) coil. In our project, multi-strand cables with 600 A nominal current are designed for double-pancake (DP) coils with 400 mm inner diameter. The coil production processes in our project are wind-and-react (W&R) and react-and-wind (R&W) methods, in which a Rutherford-type cable consisting of eight (W&R) or ten wires (R&W) with specific twist pitch is reacted and then used to wind the DP coils, to investigate the suitable manufacturing process for MgB2 coils. The final goal is to fabricate five-stacked DP coils, made up of four DP coils by the R&W method and one DP by the W&R method with a total number of 512 turns, forming a 30 kJ SMES coil and to demonstrate compensation of voltage fluctuation on the BUS line of 48 V DC in a micro grid consisting of renewable energy source and liquid hydrogen supply system in our project. The first DP coils made by the two manufacturing processes are constructed and tested with regard to their properties such as critical current density in liquid helium to keep uniform temperature distribution throughout the coils.

A large heat load caused by thermal radiation through a metal shield pipe was observed in a cooling test of a cryostat for a prototype of a cryogenic interferometric gravitational wave detector. The heat load was approximately 1000 times larger than the value calculated by the Stefan-Boltzmann law. We studied this phenomenon by simulation and experiment and found that it was caused by the conduction of thermal radiation in a metal shield pipe., 7 pages, 4 figures, 2 tables, Submitted to Jpn. J. Appl. Phys

Current status of TAMA and CLIO detectors in Japan is reported in this article. These two interferometric gravitational-wave detectors are being developed for the large cryogenic gravitational wave telescope (LCGT) which is a future plan for detecting gravitational wave signals at least once per year. TAMA300 is being upgraded to improve the sensitivity in low frequency region after the last observation experiment in 2004. To reduce the seismic noises, we are installing new seismic isolation system, which is called TAMA Seismic Attenuation System, for the four test masses. We confirmed stable mass locks of a cavity and improvements of length and angular fluctuations by using two SASs. We are currently optimizing the performance of the third and fourth SASs. We continue TAMA300 operation and R&D studies for LCGT. Next data taking in the summer of 2007 is planned. CLIO is a 100-m baseline length prototype detector for LCGT to investigate interferometer performance in cryogenic condition. The key features of CLIO are that it locates Kamioka underground site for low seismic noise level, and adopts cryogenic Sapphire mirrors for low thermal noise level. The first operation of the cryogenic interferometer was successfully demonstrated in February of 2006. Current sensitivity at room temperature is close to the target sensitivity within a factor of 4. Several observation experiments at room temperature have been done. Once the displacement noise reaches at thermal noise level of room temperature, its improvement by cooling test mass mirrors should be demonstrated., 6 pages, 5 figures, Proceedings of GWDAW-11

Magnetic field decay of superconducting magnets during the particle injection period and subsequent snapback, which is a rapid magnetic field change at the beginning of acceleration, are issues to be solved for stable operation of high-energy accelerators. In order to simulate and understand the phenomena, we made model calculations using a Monte Carlo method. The calculation results were consistent with the magnetic field measurement results of periodic magnetic patterns and the allowed multipole field drift. Using our simulation we also investigated the impact of conductor magnetization on these effects. We calculated the scaling law that predicts the snapback parameters and may be adopted for rapid magnetic field correction in superconducting accelerators. We report the simulations and the analysis

The LHC performance depends critically on the low- beta triplets, located on either side of the four interaction points. Each triplet consists of four superconducting quadrupole magnets, which must operate reliably at up to 215 T/m, sustain extremely high heat loads and have an excellent field quality. A collaboration of CERN, Fermilab and KEK was formed in 1996 to design and build the triplet systems, and after nine years of joint effort the production will be completed in early 2006. We retrace the main events of the project and present the design features and performance of the low- beta quadrupoles, built by KEK and Fermilab, as well as of other vital elements of the triplet. The tunnel installation of the first triplet and plans for commissioning in the LHC are also presented. Apart from the excellent technical results, the construction of the LHC low- beta triplets has been a highly enriching experience combining harmoniously the different competences and approaches to engineering in a style reminiscent of high energy physics experiment collaborations

Rectangle-shaped YBCO bulk conductors 20 mm wide, 140 mm long and 10 mm thick were manufactured from square-pillar-shaped YBCO bulk materials for supplying a 20 kA current into a pressurized superfluid cooling region at a temperature of 1.8 K. An assembled 1.8 K current feedthrough was mounted in the λ -plate of a pressurized superfluid cooling cryostat. Current-feed experiments into the 1.8 K region were carried out by operating the 20 kA current feedthrough. In the experiments, the transport current was kept at 20 kA for longer than 1200 s. Contact resistance and Joule heat generation in the joint region between the YBCO bulk conductors and the copper electrode were 1.45 nΩ and 0.72 W, respectively, in the 20 kA operation.

High-performance superconducting quadrupole magnets, MQXA, for the LHC low-beta insertions have been designed, manufactured in series and tested. The design field gradient of the quadrupole, which has a coil aperture of diameter 70 mm, was 240 T/m at 1.9 K; its effective length is 6.37 m, and it is required to operate reliably at up to 215 T/m when subjected to radiation heat deposit in the coils of up to 5 W/m. The series of 20 magnets has been produced in industry, and tested at KEK. The magnet design is explained, and the construction and performance of the series units, in terms of training, field quality and geometry, are presented.

The inner triplet quadrupole magnets (MQXA) for the LHC low-beta insertion have been developed. The quadrupoles provide a field gradient of 215 T/m at 1.9 K in a coil aperture of 70 mm diameter and with an effective magnetic length of 6.37 m. The series of 20 magnets have been produced in industry, and full testing has been done at KEK. We present an overview of the production and the results from mechanical and magnetic measurements.

A fine-grained steel has the same components and weldability as a mild steel, whereas a conventional high-strength steel has lower weldability due to its alloying elements. The occurrence of softening caused by coarsening in the heat-affected zone (HAZ) of welded parts of the fine-grained steels and mechanical design of welded parts including weld HAZ-softening becomes much important. Mechanical properties of the HAZ-softening joint are examined by considering the characteristics of the tensile strength under the theory of the strength of undermatched joints. The effects of the mechanical and geometrical heterogeneity on tensile strength of the HAZ-softened joint are studied by using the large-deformation finite-element analysis. The design of the HAZ-softened joint is possible considering welding conditions and tensile strength of the joint that mostly overreach the strength of the base metal. The deformation behaviour and the fracture characteristics in HAZ-softened joints under the consideration of the actual use are furthermore investigated.

Time-varying magnetic field quality of superconducting accelerator magnets is a important issue of accelerator operation at particle injection. This is induced by magnetization changes of superconductors due to redistributions of imbalance current of superconducting strands in cables. Because the imbalance current and its redistributions induce time variations of magnetic periodic patterns, to clarify the mechanism of time-varying magnetic field, we performed periodic pattern measurements on quadrupole magnets for the LHC insertion regions developed by KEK in collaboration with CERN. We report the results of the measurements with various excitation processes, and describe estimation of imbalance current using numerical calculation.

Nb/sub 3/Al superconductors have shown promising performance compared to Nb/sub 3/Sn conductors when processed by rapid heating/quenching process. Therefore we have started an R&D program of Nb/sub 3/Al conductors for future accelerator magnets. Several test wires of around 0.8 mm diameter, which have relatively small filament (/spl sim/50 micron diameter) and low matrix ratio (/spl sim/1.0), were fabricated, and the heat treatment and area reduction conditions after the rapid quenching process were studied. The highest noncopper J/sub c/ achieved during this study was 1734 A/mm/sup 2/ at 10 T and 4.2 K.

In Phase II experiment of a large helical device (LHD) of the National Institute for Fusion Science (NIFS), the helical coils are planned to be operated at 1.8 K by employing pressurized superfluid cooling to raise the magnetic field up to 4 T using a current of 17.3 kA. It is important to develop a 20 kA-class current feedthrough into the 1.8 K region with high current capacity and low heat leakage in the maximum leakage magnetic field of 1 T. The YBCO bulk conductors of 20 mm in width, 140 mm in length and 10 mm in thickness were assembled into a prototype 1.8 K current feedthrough. The current transport tests of the prototype 1.8 K current feedthrough were carried out successfully for currents up to 20 kA with liquid helium bath cooling at 4.2 K. The transport current was held at 20 kA for longer than 300 seconds. During the 20 kA operation, the current transport section of the YBCO bulk conductor remained in the superconducting state and the voltage drop between the YBCO bulk conductors and the copper electrode was constant. The contact resistance and the Joule heat generation in the joint region between the YBCO bulk conductors and the copper electrode were 1.8 n/spl Omega/ and 0.72 W, respectively when operated at 20 kA. We demonstrated the feasibility of a 1.8 K HTS current feedthrough using large-sized YBCO bulk conductors for the Phase II experiment of the LHD.

The possibility of superferric accelerator and beam line magnets is described. A cooling system that is not helium and nitrogen based, but one based on hydrogen, is proposed to make full use of the recent MgB/sub 2/ superconductor around 20 K. A hydrogen cooling system is more effective than the nitrogen cooling for usual high T/sub c/ superconductors around 70 K. Liquid hydrogen is also excellent as refrigerant for high T/sub c/ superconducting apparatus to increase the critical current and to provide a self-sustained cooling system by means of a combination of evaporated hydrogen and a fuel cell. This paper also discusses hydrogen safety issues, as compared to that of helium and nitrogen. It is expected that dipole magnets for a synchrotron would be good candidates for a superferric design based on these principles.

As a part of the collaboration program between CERN and KEK for the LHC, KEK has developed a superconducting low-beta quadrupole magnet, MQXA. KEK will supply 18 MQXA magnets, and 16 magnets will be installed in total in the four interaction regions. The cold tests of 13 magnets have been completed. Systematic field measurements were performed on these magnets, and these 13 magnets had satisfactory field quality for the requirement of beam optics. This paper describes the magnetic field behavior of the 13 MQXA magnets from the viewpoint of accelerator operation.

KEK has completed 13 of the 18 MQXA quadrupole magnets supplied for the LHC interaction region. The field measurements at room temperature were performed before and after the cold test. The multipole components by the warm measurements showed a good correlation with those by the cold measurements. It is concluded that field quality of the magnets can be evaluated by the warm measurements.

The voltage–current characteristics of commercial multifilamentary NbTi wires have been examined in the magnetic fields from 0 to 10 T. The measurements were performed using a specimen holder made of a fiberglass epoxy cylinder of 50 mm in diameter. The specimens of 300 mm length were spirally wound on it and the normal-state transition was measured over the central 150 mm of the specimen. The results show that in the field above 3 T the n-values determined from the V –I traces for the electric field higher than 10 lV/m increase with decreasing field, but below 2 T the n-values begin to decrease and take a minimum at about 0.5 T. 2003 Elsevier B.V. All rights reserved.

Superconducting quadrupole magnets for the LHC-IR have been developed and tested by KEK in collaboration with CERN. Magnetic field measurements of the magnets were performed. The magnets satisfy the requirements for the accelerator operation. In addition to the field quality measurements, fine structures of the magnetic field along the magnet axis were measured at the beam injection current using a 25 mm long rotating harmonic coil. Periodic patterns of the magnetic field were observed in higher order multipole coefficients. The pitch of the periodic patterns is equal to the cable twist pitch. The time dependent change of the amplitude of the periodic pattern was also observed. In this paper, the measurement and results are reported.

The power supply for high intensity synchrotron magnet draws large amount of power from utility network. The JHF 50-GeV main ring will require 104 MW of total active power and 28.8 MW of dissipation power by estimation. Moreover, the charging and discharging cycle is repeated with 3.64 s of the cycle time at the initial operation, and the repeating frequency will be raised up by twice in future. Taking this situation into consideration, energy storage system using adjustable speed type flywheel and IGBT power converter are studied in the JHF project. In this paper, the power supply using SMES is proposed. The power supply can absorb the fluctuation of active and reactive power caused by charging and discharging the synchrotron magnet. The system is composed of current source ac/dc converter, chopper circuits and superconducting magnets. The chopper circuits for superconducting magnets and synchrotron magnets can be connected to the same dc bus of the power supply and this feature can reduce the power rating of ac/dc converters.

The MQXA superconducting low-beta quadrupole magnets for the LHC interaction regions are required to generate a field gradient of up to 215 T/m at 1.9 K along an effective magnetic length of 6.37 m. After completion of an R&D program on short models and full length prototypes, the series production of magnets has started, with to date five series magnets subsequently tested at KEK. Basic characteristics such as normal training, subsequent full energy dump, thermal cycle, ramp rate dependence and temperature dependence have been studied and results indicate that magnets have satisfactory quench performance. Magnetic field measurements performed at 1.9 K show the field quality to be uniform and to satisfy the stringent beam optics requirements.

When a small normal zone is produced in a strand in a superconducting cable by a local disturbance, current redistribution occurs and can help the recovery of its superconducting state. This effect of the current redistribution depends on the initial current distribution. In this paper, the initial current distribution in a triplex cable is controlled artificially to study its influence on the stability against local disturbances. A heat pulse is applied to a strand by a carbon paste heater to initiate the quench. Transient current distributions during quench or recovery process are measured by sets of Hall sensors placed at several locations along the cable axis. When the transport current is less than a threshold value, the stability is improved by the current redistribution from the heated strand to the others, even if the initial current distribution is not uniform. This threshold is related to the current margin of the heated strand, rather than to the current margin of the whole cable. Above this threshold current, the MQE against local disturbances is smaller in the cable with the non-uniform current distribution than in the cable with the uniform current distribution, when the total transport current is identical. If the current of the heated strand is identical and above the threshold, the MQE against local disturbances does not depend on the current distribution and agrees with the MQE of the single isolated strand. It means that the quench of one strand leads to the quench of the cable, and that the stability of one strand in the cable is not influenced by interaction with the others.

The development of the LHC low-beta insertion quadrupole magnets has been conducted at KEK since 1996. After the successful development of short model magnets, the first prototype magnet has been built by Toshiba and is tested at KEK. Although the quench performance and the field quality of the magnet are satisfactory, a design problem is found in one of the end spacers. The problem increases the risk of a turn-to-turn and in fact causes shorts in the second prototype magnet, and in the trial coil of the first production magnet. The design is modified and the problem appears to be resolved. The construction of the production magnets is now started and lasts till the summer of 2004.

A good field quality is always requested to achieve for the low-/spl beta/ quadrupole magnet being used in the accelerator projects. To meet the requirement, people are always managing to reduce the field errors from its magnetic design and construction. In order to obtain a basic understanding for various known multipolar field errors, some calculation evaluations have been performed. Based on the results, the possible origins and corresponding correction methods of the deviation were briefly discussed in the paper.

A pair of 8 kA HTS current leads for an accelerator magnet test facility at KEK has been designed and fabricated. The HTS current lead is composed of a copper section in the high temperature region and a HTS section in the low temperature region. The copper section of the lead consists of copper wires bundled into a stainless steel pipe. The HTS section consists of 12 HTS tape units made by Bi2223/Ag-1 at% An tapes arrayed onto the outer surface of a stainless steel tube with a diameter of 54 mm. The whole length and the maximum diameter of the lead are 1465 mm and 71 mm, respectively. The entire length of the current lead is cooled with helium gas. The design heat load and the helium gas flow rate of the lead in a steady state 8 kA-operation are less than 0.2 W and 0.4 g/sec, respectively and temperatures of the high and low temperature ends of the HTS section under the condition are 50 K and 4.4 K, respectively. The thermal performance test was carried out, and the results agreed well with the calculated values. So, we verified the validity of the thermal analysis and design. The corresponding heat load is estimated to be 0.15 W. These values of 0.4 g/s and 0.15 W are only 89% and 1.5% of the conventional gas cooled current lead, respectively.

Superconducting low-beta quadrupole magnets for the LHC insertion regions are being developed at KEK as part of the collaboration between CERN and KEK. Magnet production technology developed at KEK has been transferred to a manufacturer of production magnets. In order to verify the production technology, fabrication jigs, tools, and procedures, the first full-scale prototype, MQXA-P1, was fabricated. Mechanical characteristics of MQXA-P1 were measured during the magnet assembly process, and it satisfied specifications needed for the production magnets. The validity of the magnet design and fabrication method was confirmed.

KEK has developed a prototype of the 6.6 m long MQXA quadrupole for the LHC interaction region. After the first cool-down to 1.9 K, the magnetic field measurements were performed. The prototype could produce a field gradient of 215 T/m corresponding to the operating point of the LHC flat top. The field quality of the magnet was sufficiently good to satisfy the requirement of the accelerator beam optics.

A warm magnetic field measurement system has been designed and constructed for the low-/spl beta/ quadrupole magnet (MQXA) for the LHC interaction regions. The field quality of the first prototype of MQXA has been evaluated at room temperature with this system. According to the field measurement, we found a quite good correlation between the warm and the cold measurements and good performance of the warm measurement system. The magnet twist angle along the magnet axis was also measured with the system, and the obtained results were consistent with the measurement result of mechanical fiducials on the shell surface of the magnet.

In the National Institute for Fusion Science (NIFS), the following three research items are being advanced as application of high temperature superconductor (HTS) to an experimental fusion plasma system, through collaboration with universities and laboratories. The first is an application of HTS in the large current feedthrough to a superconducting coil cooled with superfluid helium in order to reconcile low heat load and stable large current transport capability. A 20 kA current feedthrough from 4.4 K to 1.8 K has been being developed using YBCO bulk superconductors manufactured by the QMG process. The second is the development of a 30 kA HTS current lead. The Bi2212 bulk material fabricated by the diffusion process is considered as a candidate material for HTS current leads. The third is the development of the superconducting magnetic-levitation coil for Mini-RT wound with Bi2223 tape conductor. A magnetic-levitation coil operated in persistent-current mode has to levitate for 8 hours without a feed of refrigerant. Present status of these HTS application researches in NIFS is reported.

The magnetic field of superconducting accelerator magnets is mainly determined by the current distribution. A distortion of current distribution induces unexpected multipole fields. A simple analytical field calculation with radial distortions, which are described by Fourier series, is developed. Analytical equations which give the correlation between the deformation patterns and the multipole field components are found. The equations are applied to the measurement results for the LHC-MQXA magnets developed by KEK. The radial distortions which introduces normal octupole and twelvepole fields are estimated. The direction of distortions follows the magnet mechanical tendency. The amplitude of those is within the construction errors. A numerical computation applying the distortions to the real cross section is performed. The computation results prove that the analytical equations give the good approximation.

AC loss due to coupling currents in a Rutherford cable can be modified by changing the interstrand contact resistance (ICR) by: adjusting the level of native oxidation of the strand, coating it, or by inserting a ribbon-like core into the cable itself. With regard to cored cables further effective-ICR adjustments can be achieved by changing: (i) the degree of compaction during manufacture, (ii) the thickness of the core at fixed overall thickness, and (iii) the width of the core. We report on the results of magnetic and calorimetric AC loss measurements on stainless-steel-cored stabrite cables which had been: (i) externally compacted by rolling to thicknesses of 0%, 6%, 9%, and 11% below the standard thickness, (ii) internally compacted by being furnished with cores of thicknesses 1 mil (25 μm) and 2 mil (50 μm), and (ii) furnished with cores whose widths, wcore, were about 20%, 50%, 75% and 100% of the maximum available width. The measurements were made in applied AC fields that were directed perpendicular (face-on, FO) and parallel (edge-on, EO), respectively, to the broad cables faces.

Quench propagation velocity is one of the most important parameters for the quench protection of superconducting magnets. We examined the relations between the current redistribution and the quench propagation velocity in a Rutherford cable made of non-insulated strands. Measurements were performed in the cables with three contact conditions between strands, and it was found that the quench propagation velocity and the current redistribution depended on the contact conditions between strands. A numerical simulation of the current redistribution using a simple model was performed. We made comparisons between the test and numerical results, and there was good agreement. We analyzed the numerical results in detail, and found that the current redistribution caused by the magnetic field distribution in the cable cross-section around the boundary of the normal zone, called normal front, enhanced the quench propagation velocity.

Development of the LHC low-/spl beta/ insertion quadrupole magnet has been in progress at KEK since 1995 as a cooperative program between CERN and KEK. Five 1-m short model magnets have been fabricated and three of them have been tested. From the various test results of the first two models, the coil configuration was further optimized to reduce the higher magnetic field harmonic coefficients. The cold test of the third model showed satisfactory performances of the field harmonics. After this R&D work, the authors are at a stage for the fabrication of two prototype magnets which have the same scale as the production magnets. The status of the R&D for the LHC low-beta insertion quadrupole magnet at KEK is described.

In superconducting magnets with large energies, quench protection heaters (QPHs) are necessary to prevent localized quenches. If the full energy of a magnet is dissipated into a small volume, the magnet may suffer irreparable damage. The QPHs are used to heat the surface of the coil to increase the size of the normal zone so the heat is dissipated over a larger volume. As a result, the maximum temperature after a quench will be reduced. The KEK low-/spl beta/ quadrupole 1-m model magnets for the Large Hadron Collider (LHC) have four QPHs on the outer surface of the coil. A capacitive power supply with 7.2 mF/channel and a maximum charge of 400 V is used to fire the heaters, yielding a maximum energy of 576 J/channel. The QPH set-up used at CERN has an initial current of 54 A and a time-constant of 118 ms. Because the power supply used for the KEK 1-m model is not identical to the power supplies used at CERN for the 6-m production magnets, a similar set-up is achieved by connecting two power supply channels in parallel and adding an external resistor to each circuit giving an initial current of 52.6 A with a time-constant of 109 ms. Several aspects of the performance of the QPHs for the third 1-m model magnet (LHCIRQ03) have been studied: full energy dump (compared with 2nd model, LHCIRQ02), full charge on QPHs at 215 T/m, determine the minimum magnet current at which the QPHs can initiate a quench, and spot heater tests (both with and without the QPHs).

The National Institute for Fusion Science (NIFS), in collaboration with universities and laboratories in Japan, the Forschungszentrum Karlsruhe (FZK) and the Max-Planck Institut fur Plasma Physik (IPP) in Germany, is planning to develop high temperature superconducting (HTS) current feeders for large-scale superconducting coils. Two programs are being progressed: one is a current feedthrough for superfluid helium (He II) cooled superconducting coils; the other is current leads for experimental fusion system. The paper describes the present status of the two programs, including joint experiments of a 20 kA Bi-2223 current lead developed by FZK and development of a prototype YBCO bulk current feedthrough for He II cooled superconducting coils. In addition, the test results of Bi-2212 tubes fabricated by diffusion process, applicable to HTS current leads, are described Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/.

High gradient 70 mm aperture superconducting low-beta quadrupole magnets have been developed at KEK as part of the collaboration between CERN and KEK for the Large Hadron Collider (LHC). After development of two 1 m model magnets, the third model magnet with the new coil design was built and excitation tests were completed. The third model successfully reached the design field gradient of 240 T/m and showed training memory after full thermal cycles. Other quench tests were performed and it was verified that the third model exhibited reliable quench performance and sufficient safety margin during operation.

A mechanical quality factor of $1.1 \times 10^{7}$ was obtained for the 199 Hz bending vibrational mode in a monocrystalline sapphire fiber at 6 K. Consequently, we confirm that pendulum thermal noise of cryogenic mirrors used for gravitational wave detectors can be reduced by the sapphire fiber suspension., Comment: To be published to Physiscs Letters A. Number of pages: 10 Number of figures: 5 Number of tables: 1

For accelerator dipole magnets, the study on multipole coefficients in a local region is useful for understanding magnet characteristics and checking construction procedure. The multi-probe pulsed-NMR method is a candidate for measurement of the local multipole coefficients. For the absolute fields measured by the multi-probe pulsed-NMR method, a rigorous application of the Fourier expansion is found to yield multipole coefficients. It is made clear that the direction of the dipole field is unable to be determined by the Fourier expansion alone. For estimating alignment accuracy of pulsed-NMR probes, the relationship between errors of multipole coefficients and those of probe position is derived by the Fourier expansion method. For applying of multi-probe pulsed-NMR method to accelerator dipole magnets, we designed and fabricated a field measuring system using two probes. The probes had NMR coils wound around glass ampoules with a diameter of about 1.4 mm. The NMR signal was processed with a phase lock loop circuit to produce the NMR frequency. Dipole field uniformity and multipole coefficients were measured at 0.35 T for a 1.5 m long dipole magnet. It was confirmed that the field data by this NMR system had an accuracy of 10/sup -6/.

As part of the collaboration program between CERN and KEK for the LHC, we have been developing a high field gradient superconducting insertion quadrupole magnet with a field gradient of 240 T/m in an aperture of 70 mm. To date two model magnets have been built and their quench characteristics and field qualities have been studied. Based on these results. We have performed the final adjustment of the magnet design. In this paper we present the summary of the design which includes short sample limits and field quality analysis for both the straight section and the end regions.

In superconducting magnets with large energies, quench protection heaters (QPHs) are necessary to prevent localized quenches. If the full energy of a magnet is dissipated into a small volume, the magnet may suffer irreparable damage. The QPHs are used to heat the surface of the coil to increase the volume of the normal zone so the heat is dissipated over a larger area. As a result, the maximum temperature after a quench will be reduced. The KEK low-/spl beta/ quadrupole magnets for the Large Hadron Collider (LHC) have four QPHs on the outer surface of the coil. Several aspects of the performance of the QPHs for the KEK-LHC insertion quadrupole magnets have been studied. The time from firing the QPHs to quench vs. QPH-input-energy, the effects of varying quench-detection time on the magnet power supply, and the results of a normal training quench with no dump resistor and using the QPHs are reported and compared to a quench simulation code.

Two 1-m model magnets for the LHC low-/spl beta/ quadrupoles were constructed and tested in KEK. They were energized to over 240 T/m. The field quality was measured by two harmonic coils. The multipole components were estimated along the straight section and the magnet ends. The results obtained show that the effect of the thermal cycle on the magnetic field is negligible. The time dependence of the multipole components were also measured at 420 A and it was found that b/sub 6/ changed 0.8 units over 3 hours. This paper describes the magnetic field quality of the two magnets.

The development of high-gradient superconducting quadrupole magnets for the LHC interaction regions has been carried out. The mechanical design has been optimized with the two-shell coil structure tightly fixed by thin non-magnetic collars and by iron-yoke with keys. The mechanical rigidity is fully achieved at room temperature. The paper describes the mechanical design characteristics and analysis of mechanical tolerances and the influence on the field quality.

Two models of the high gradient 70 mm aperture superconducting low-/spl beta/ quadrupole magnets were developed at KEK as part of the collaboration between CERN and KEK for the Large Hadron Collider (LHC). The training tests of both model magnets have been carried out at 1.9 K and both models successfully reached the design field gradient of 240 T/m, and the training memory partially remained after thermal cycles. General characteristics of the training curve for the models seemed to be similar. In this paper, training results of the model magnets is described and discussed.

In order to study the relationship between quench propagation velocity and current redistribution during a quench, heater quench tests were performed. The cable used was eight-strand Rutherford cable coated with Sn-5Ag, which was subjected to a uniform magnetic field of 4 T. The quench process was measured by using voltage taps and sets of pickup coils. The authors found that, over a certain transport current, the quench propagation velocity accelerated as the normal zone propagated. The relationship between the quench propagation velocity and the current redistribution is discussed.

A one meter model of the high gradient 70 mm aperture superconducting low-/spl beta/ quadrupole has been developed at KEK. The design field gradient is 240 T/m at a current 7677 A with a superconducting load line ratio of 92% and peak field of 9.64 T in the coil. A first series of training tests of the magnet was carried out at 1.9 K including a full thermal cycle to room temperature. The highest quench current was 8007 A corresponding to a field gradient of 250 T/m. The magnet was subsequently reassembled to improve its longitudinal mechanical structure. In this paper, quench characteristics and mechanical behavior of the first model magnet are presented.

The magnetic field measurements of the first l-m long model magnet for the LHC interaction region were performed at 1.9 K. The measured field gradient of the magnet was 227.7 T/m at 7200 A. The multipole fields as a function of axial position and magnet current were measured. The major higher multipole at the magnet center was the sextupole and the ratio to the quadrupole field was 1.4/spl times/10/sup -4/ at 7200 A and at a reference radius of 17 mm.

A melt-textured YBCO bulk material was employed to obtain high current transport characteristics of a bulk high temperature superconductor. A disk-shaped YBCO bulk material 65 mm in diameter and 15 mm thick was fabricated by a modified quench and melt growth (QMG) process. An "H" shaped bulk conductor was cut from the YBCO disk. The cross sectional area and length of the conductor were 7 mm/spl times/7 mm and 20 mm, respectively. The bulk conductor was mounted in a high current bus line with a conductor-holder which allows high current feed and mechanical support against the thermal stress and electromagnetic force. Both ends of the conductor were soldered to electrodes of the conductor-holder. At 4.2 K, high current transport experiments were carried out up to 25 kA.

The superconducting wire with approximately 10 /spl mu/m diameter filaments of Nb-41 wt%Ti-28 wt%Ta alloy was fabricated from our standard production billet. Critical current densities and upper critical fields after various heat treatments were measured in the temperature range of 4.2 K to 1.6 K. Thermo-mechanical treatments for /spl alpha/-Ti precipitates were optimized to improve critical current densities. A 27-strand Rutherford type cable having a large keystone angle was trial-fabricated using the optimized-processed wires. The achieved J/sub c/s were 1383 A/mm/sup 2/ (10 T and 1.9 K) and 602 A/mm/sup 2/ (12 T and 1.9 K). The fabricated wire was proved to have high homogeneity and good workability.