Y. Ajima

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.

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.

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.

Test Results of Superconducting Combined Function Prototype Magnets for the J-PARC Neutrino Beam Line

Superconducting combined function magnets are adopted for the 50 GeV, 750 kW proton beam line for the J-PARC neutrino experiment, and two full-scale prototype magnets have been developed successfully at KEK. In the cold tests, both prototypes were excited up to 7700 A without spontaneous quenches. The measured field quality of the both prototypes agreed well with the design field, indicating that the fabrication process has no major problem. The heater quench tests of the first prototype, however, showed that the magnet was not self-protected. Consequently, the design was revised and quench protection heaters were adopted. In quench heater tests of the second prototype magnet using small sheet heaters, the fundamental characteristics of the quench protection heaters were studiedSuperconducting combined function magnets for the J-PARC (Japan Proton Accelerator Research Complex) neutrino experiment have been successfully developed at High Energy Accelerator Research Organization, KEK. The first prototype magnet reassembled for the quench protection studies, and the cold test result indicated that the eight quench protection heaters are effective for the safe protection of the magnet. Three production magnets have been fabricated and tested at 4.5 K, 1 atm, in a vertical cryostat, and the excellent excitation and quench performances are observed. In the field measurement during cold tests, all the magnets indicated the field qualities good enough to fulfill the specification. The field measurement at room temperature has been also performed with the three production magnets for checking the dipole field component. The results are consistent with the computation.

Development of a prototype of Superconducting combined function magnet 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 of a dipole field of 2.6 T with a quadrupole field of 19 T/m in a coil aperture of 173.4 mm. Critical magnet components including glass-fiber reinforced phenolic plastic spacers have been successfully developed. The mechanical design has been verified by a 100 mm long short-cut model, and coils have been wound for the first full-length prototype.

Superconducting combined function magnet system for J-PARC neutrino experiment

The J-PARC Neutrino Experiment, the construction of which starts in JFY 2004, will use a superconducting magnet system for its primary proton beam line. The system, which bends the 50 GeV 0.75 MW proton beam by about 80 degrees, consists of 28 superconducting combined function magnets. The magnets utilize single layer left/right asymmetric coils that generate a dipole field of 2.6 T and a quadrupole field of 18.6 T/m with the operation current of about 7.35 kA. The system also contains a few conduction cooled superconducting corrector magnets that serve as vertical and horizontal steering magnets. All the magnets are designed to provide a physical beam aperture of 130 mm in order to achieve a large beam acceptance. Extensive care is also required to achieve safe operation with the high power proton beam. The paper summarizes the system design as well as some safety analysis results.

Magnetic field measurements of the prototype LHC-IR MQXA at 1.9 K

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.