Susana Izquierdo Bermudez

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.

Progress on the Development of the Nb3Sn 11T Dipole for the High Luminosity Upgrade of LHC

The high-luminosity large hadron collider (LHC) project at CERN entered into the production phase in October 2015 after the completion of the design study phase. In the meantime, the development of the 11 T dipole needed for the upgrade of the collimation system of the machine made significant progress with very good performance of the first two-in-one magnet model of 2-m length made at CERN. The 11 T dipole, which is more powerful than the current main dipoles of LHC, can be made shorter with an equivalent integrated field. This will allow creating space for the installation of additional collimators in specific locations of the dispersion suppressor regions. Following tests carried out during heavy ions runs of LHC in the end of 2015, and a more recent review of the project budget, the installation plan for the 11 T dipole was revised. Consequently, one 11 T dipole full assembly containing two 11 T dipoles of 5.5-m length will be installed on either side of interaction point 7. These two units shall be installed during the long shutdown 2 in years 2019–2020. After a brief reminder on the design features of the magnet, this paper describes the current status of the development activities, in particular the short model programme and the construction of the first full scale prototype at CERN. Critical operations such as the reaction treatment and the coil impregnation are discussed, the quench performance tests results of the two-in-one model are reviewed and finally, the plan toward the production for the long shut down 2 is described.

Design Optimization of the Nb3Sn 11 T Dipole for the High Luminosity LHC

As a part of the large hadron collider luminosity upgrade (HiLumi-LHC) program, CERN is planning to replace some of the 8.33-T 15-m-long Nb-Ti LHC main dipoles with shorter 11 T Nb3Sn magnets providing longitudinal space for additional collimators. Whereas the present design of the 11 T dipole enables the use of RRP conductor with critical current degradation after cabling at the level of 5%, new cross sections of the cable have been studied in order to further decrease the degradation of both critical current and resistivity of the copper matrix. This change is particularly beneficial for the PIT conductor. The coil layout is reoptimized to accommodate the new cable geometry, using the ROXIE code. A set of additional design changes are implemented, such as reduction of the outer yoke diameter. In this paper, we review the main parameters of the present design, describe the changes implemented in the new design, and discuss their impact on both the electromagnetic and structural properties.

Magnetic Analysis of the Nb

As part of the Large Hadron Collider Luminosity upgrade (HiLumi-LHC) program, the US LARP collaboration and CERN are working together to design and build 150-mm aperture Nb3Sn quadrupoles for the LHC interaction regions. A first series of 1.5-m-long coils were fabricated, assembled, and tested in the first short model. This paper presents the magnetic analysis, comparing magnetic field measurements with the expectations and the field quality requirements. The analysis is focused on the geometrical harmonics, iron saturation effect, and cold-warm correlation. Three-dimensional effects such as the variability of the field harmonics along the magnet axis and the contribution of the coil ends are also discussed. Moreover, we present the influence of the conductor magnetization and the dynamic effects.

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In the framework of the high-luminosity upgrade of the large hadron collider, the U.S. LARP collaboration and CERN are jointly developing a 150-mm aperture Nb3Sn quadrupole for the Large Hadron Collider (LHC) interaction regions. Due to the large beam size and orbit displacement in the final focusing triplet, MQXF has challenging targets for field quality at nominal operation conditions. Three short model magnets have been tested and around 30 coils have been built, allowing a first analysis of the reproducibility of the coil size and turns positioning. The impact of the coil shimming on field quality is evaluated, with special emphasis on the warm magnetic measurements and the correlation to field measurements at cold and nominal field. The variability of the field harmonics along the magnet axis is studied by means of a Monte-Carlo analysis and the effects of the corrective actions implemented to suppress the low-order unallowed multipoles are discussed.

Sn low-beta Quadrupole for the High Luminosity LHC

A next step of energy increase of hadron colliders beyond the LHC requires high-field superconducting magnets capable of providing a dipolar field in the range of 16 T in a 50-mm aperture with accelerator quality. These characteristics could meet the requirements for an upgrade of the LHC to twice the present beam energy or for a 100-TeV center of mass energy future circular collider. This paper summarizes the activities and plans for the development of these magnets, in particular within the 16 T Magnet Technology Program, the WP5 of the EuroCirCol, and the U.S. Magnet Development Program.

Geometric field errors of Short Models for MQXF, the Nb3Sn low-beta Quadrupole for the High Luminosity LHC

High-field superconducting accelerator magnets are a key technology of the future circular collider. In order to master the technical challenges and achieve the performance targets, CERN has launched a technology development program. The first step of the program is to explore the Nb3Sn performance limits at 18 T field level and high stress, simplifying to the maximum the coil geometry. The first magnet to be built, the enhanced racetrack model coil (ERMC), aims at a mid-plane field of 16 T with 10% margin on the load line at 4.2 K. The ERMC is composed of two flat racetrack coils with no bore. To further develop the block-coil geometry, a second magnet, the racetrack model magnet (RMM), will be composed of two ERMC coils and a middle coil with a 50-mm closed cavity, addressing the issue of the design of an inner support to compensate for the preload forces. The RMM aims at a central field of 16 T in a 50-mm cavity, with 10% margin at 4.2 K. The next step is to develop a more compact and cost-effective design using two cable sizes, and therefore two different current densities. The coils will be assembled in a shell-based support structure using bladders and keys, which allows a precise control of the stress with minimal spring back and conductor overstress. This paper describes the magnetic and mechanical design of the ERMC and the RMM.

Status of the 16 T Dipole Development Program for a Future Hadron Collider

End parts are critical components for saddle-shaped coils. They have a structural function where the cables are deformed in order to cross over the magnet aperture. Based on the previous design of the US LARP program for 90-mm aperture quadrupoles (TQ/LQ) and 120 mm aperture quadrupoles (HQ/LHQ) using BEND, the coil ends of the low-β quadruples (MQXF) for the HiLumi LHC upgrade were developed. This paper shows the design of the MQXF coil ends, the analysis of the coil ends during the coil fabrication, the autopsy analysis of the coil ends, and the feedback to BEND parameters.

submitter : Design of ERMC and RMM, the Base of the

In 2023, the LHC luminosity will be increased, aiming at reaching 3000 fb-1 integrated over ten years. To obtain this target, new Nb3Sn low-β quadrupoles (MQXF) have been designed for the interaction regions. These magnets present a very large aperture (150 mm, to be compared with the 70 mm of the present NbTi quadrupoles) and a very large stored energy density (120 MJ/m3). For these reasons, quench protection is one of the most challenging aspects of the design of these magnets. In fact, protection studies of a previous design showed that the simulated hot spot temperature was very close to the maximum allowed limit of 350 K; this challenge motivated improvements in the current discharge modeling, taking into account the so-called dynamic effects on the apparent magnet inductance. Moreover, quench heaters design has been studied to be going into more details. In this paper, a protection study of the updated MQXF is presented, benefitting from the experience gained by studying the previous design. A study of the voltages between turns in the magnet is also presented during both normal operation and most important failure scenarios.

Nb_3Sn

The development of Nb3Sn quadrupole magnets for the High-Luminosity LHC upgrade is a joint venture between the US LHC Accelerator Research Program (LARP)* and CERN with the goal of fabricating large aperture quadrupoles for the LHC interaction regions (IR). The inner triplet (low-β) NbTi quadrupoles in the IR will be replaced by the stronger Nb3Sn magnets boosting the LHC program of having 10-fold increase in integrated luminosity after the foreseen upgrades. Previously, LARP conducted successful tests of short and long models with up to 120 mm aperture. The first short 150 mm aperture quadrupole model MQXFS1 was assembled with coils fabricated by both CERN and LARP. The magnet demonstrated a strong performance at Fermilabs vertical magnet test facility reaching the LHC operating limits. This paper reports the latest results from MQXFS1 tests with changed prestress levels. The overall magnet performance, including quench training and memory, ramp rate, and temperature dependence, is also summarized.