T. Ogitsu

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.

Quench antenna for superconducting particle accelerator magnets

We report on the design, fabrication, and test of an assembly of stationary pickup coils which can be used to localize quench origins. After describing the pickup coils configuration, we develop a simple model of current redistribution which allows interpretation of the measured voltages and determination of the turn of the magnet coil in which the quench started. The technique is illustrated by analyzing the data from a quench of a 5-cm-aperture, 15-m-long SSC dipole magnet prototype. >

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.

Investigation of wire motion in superconducting magnets

A technique was developed which allows the direct observation of the EMF induced by wire motion and the calculation of the energy release resulting from the motion. Measurements made on a superconducting quadrupole magnet showed that the excitation is accompanied by a great number of wire-motion events of a typical duration of 100 mu s and a typical energy release per unit cross section of 1 mJ/mm/sup 2/. A simple stability model based on the motion of a single strand over a half-twist pitch was then developed. The model could account for the order of magnitude of the energies involved.

Design Optimization of the New D1 Dipole for HL-LHC Upgrade

The High-Luminosity Large Hadron Collider upgrade (LHC) project aims to increase the peak luminosity of the LHC to 5 ×1034 cm - 2s - 1, and a total integrated luminosity of 3000 fb - 1 from 2020 to 2030 by upgrading the low-beta insertion system for the ATLAS and CMS experiments. The aperture of the insertion magnets including the focusing/defocusing quadrupoles and separation dipoles will be doubled to achieve a smaller β*. This paper presents the latest design updates of the separation dipole D1 magnet, including the study of the different cable types to vary the main field; the modifications of the iron shape for the new design options to minimize the iron saturation effect on field quality; and the optimization of the coil ends to reduce the peak field and higher order harmonic field integrals in the ends.

Influence of current re-distribution on minimum quench energy of superconducting triplex cable against local disturbance

Abstract Stability of multi-strand superconducting cable against local disturbances has been studied experimentally and theoretically. Quench experiments have been made with a superconducting triplex cable made of chrome-plated strands. A heat pulse is applied to a short part of one strand, and the minimum quench energy (MQE) against that local disturbance and the temporal evolution of the strand current during the quench or recovery process are measured. When the transport current divided by the critical current ( I t / I c ) is large, the MQE against a local disturbance almost equals the MQE of the single strand. When the overall I t / I c is less than 0.4, the MQE against a local disturbance is much larger than the MQE of the single strand. In this small I t / I c region, when a heat pulse whose energy is slightly less than the MQE is applied, current re-distribution is observed during the recovery process. Numerical simulations of the quench or recovery process have been made with a computer code named MST. The dependence of the calculated MQE on the I t / I c qualitatively agrees with the experimental result. The numerical and experimental results prove that the stability against local disturbances is improved by the current re-distribution when the I t / I c is less than some threshold value. This threshold appears to be influenced by the contact thermal conductance between strands.

The 16 T Dipole Development Program for FCC

A key challenge for a future circular collider (FCC) with centre-of-mass energy of 100 TeV and a circumference in the range of 100 km is the development of high-field superconducting accelerator magnets, capable of providing a 16 T dipolar field of accelerator quality in a 50 mm aperture. This paper summarizes the strategy and actions being undertaken in the framework of the FCC 16 T Magnet Technology Program and the Work Package 5 of the EuroCirCol.

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.