N. Ohuchi

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.

Magnetic design of a low-/spl beta/ quadrupole magnet for the LHC interaction regions

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.

Performance of the eight superconducting quadrupole magnets for the TRISTAN low-beta insertions

The low-beta insertion quadrupoles are iron-free superconducting magnets with an inner coil diameter of 140 mm, an effective length of 1.14 m, and a nominal gradient of 70 T/m. The coils, which are of the cos 2 Theta type, are made from four layers of 27-strand NbTi Rutherford-type cable with Kapton insulation and are firmly clamped with 316LN stainless steel collars. Following the development of prototype magnets, eight magnets have been produced and were thoroughly tested and measured prior to installation in the TRISTAN main ring. A brief description of the design and manufacturing technique and the results of tests and measurements are presented.

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.

The interaction region of KEKB

Abstract An asymmetric-energy collider of 8 GeV electrons and 3.5 GeV positrons, KEKB, has been operating at KEK since 1998. On July 9, 2001 it achieved the highest record of luminosity, 4.5×10 33 cm −2 s −1 . This paper describes the interaction region (IR) extending about 8 m from the interaction point (IP) along each beam direction. The main machine components in the IR are focusing quadrupole magnets, compensation solenoids, and vacuum chambers, which are positioned on movable stages. They are designed to focus both beams into collisions with a finite angle crossing.

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.

Production and performance of the LHC interaction region quadrupoles at KEK

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.