A. Terashima

Design study of a superconducting insertion quadrupole magnet for the Large Hadron Collider

The conceptual design study of a high gradient superconducting insertion quadrupole magnet has been carried out in collaboration between KEK and CERN for the Large Hadron Collider (LHC) to be built at CERN. A model magnet design has been optimized to provide a nominal design field gradient of 240 T/m with a bore aperture of 70 mm and an operational field gradient of 225 T/m at 1.9 K under radiation environment with a deposition of several watts per meter in the superconducting coils. The design and its process are discussed.

Progress of LHC low-/spl beta/ quadrupole magnets at KEK

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.

Design of superconducting combined function magnets for the 50 GeV proton beam line for the J-PARC neutrino experiment

Superconducting combined function magnets will be utilized for the 50 GeV-750 kW proton beam line for the J-PARC neutrino experiment and an R&D program has been launched at KEK. The magnet is designed to provide a combined function with a dipole field of 2.59 T and a quadrupole field of 18.7 T/m in a coil aperture of 173.4 mm. A single layer coil is proposed to reduce the fabrication cost and the coil arrangement in the 2D cross-section results in left-right asymmetry. This paper reports the design study of the magnet.

Superconducting magnet system at the 50 GeV proton beam line for the J-PARC neutrino experiment

A neutrino oscillation experiment using the J-PARC 50 GeV 0.75 MW proton beam is planned as a successor to the K2K project currently being operated at KEK. A superconducting magnet system is required for the arc section of the primary proton beam line to be within the space available at the site. A system with 28 combined function magnets is proposed to simplify the system and optimize the cost. The required fields for the magnets are 2.6 T dipole and 19 T/m quadrupole. The magnets are also required to have a large aperture, 173.4 mm diameter, to accommodate the large beam emittance. The magnets will be protected by cold diodes and cooled by forced flow supercritical helium produced by a 4.5 K, 2/spl sim/2.5 kW refrigerator. This paper reports the system overview and the design status.

Development of Nb/sub 3/Al superconducting wire for accelerator magnets

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.

AC loss measurements of Rutherford type superconducting cables under mechanical stresses

Experimental apparatus for measurements of AC losses in Rutherford type cable conductors has been constructed. A number of compacted cable samples have been measured. Hysteresis loss, loss from coupling within strands and loss from interstrand coupling are distinguished from each other. The results show that even for cables without soldering and coating, the AC losses may be quite different from each other due to interstrand coupling loss. As the curing temperature increases, interstrand coupling loss tends to increase. For some cables, interstrand coupling loss increases nearly geometrically with the increase of curing temperature. Most of the samples did not show dependence of loss on mechanical pressure.<<ETX>>

Production and measurement of the MQXA series of LHC low-/spl beta/ insertion quadrupoles

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.

Status of the LHC low-beta insertion quadrupole magnet development at KEK

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.

Analysis of mechanical tolerances of a low-/spl beta/ quadrupole magnet for the LHC

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.

Construction of Superconducting Magnet System for the J-PARC Neutrino Beam Line

Following success of a prototype R&D, construction of a superconducting magnet system for J-PARC neutrino beam line has been carried out since 2005. A new conceptual beam line with the superconducting combined function magnets demonstrated the successful beam transport to the neutrino production target.