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The development of Nb3Sn quadrupole magnets for the High-Luminosity LHC upgrade is a joint venture between the US LHC Accelerator Research Program (LARP)1 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 150mmaperture quadrupole modelMQXFS1 was assembled with coils fabricated by both CERN and LARP. The magnet demonstrated a strong performance at Fermilab's vertical magnet test facility reaching the LHC operating limits. This paper reports the latest results from MQXFS1 tests with changed pre stress levels. The overall magnet performance, including quench training and memory, ramp rate, and temperature dependence, is also summarized. [ABSTRACT FROM AUTHOR]

We report test results for the one meter long dipole HD3b, a block-type accelerator quality \Nb3\Sn magnet built at LBNL with operational bore fields in the range of 13–15 T. The magnet is an upgrade of the previously reported HD2 and HD3a versions, with several modifications implemented to improve conductor positioning, reduce cable “hard-way” bending radius, and strengthen electrical insulation between cables and coil parts. The magnet exhibited long training behavior, but showed a good “memory” of the trained state upon thermal cycling. Ramp-rate dependence of the quench current, field quality performance characteristics, and protection heater studies were conducted. Quench propagation velocity and quench locations were determined based on the voltage signals; quench localization was further improved using inductive quench antenna and acoustic emission sensors. Short- and long-term acoustic precursors to quenching were observed. [ABSTRACT FROM PUBLISHER]

In the framework of the Large Hadron Collider Luminosity upgrade (HiLumi-LHC) project, the US LHC accelerator research program is developing high-gradient, large-aperture \Nb3 \Sn quadrupole magnets for the LHC interaction regions. The fabrication and tests of a first series of 120-mm-aperture “HQ01” coils revealed design issues that resulted in limited performance. A second series of coils was fabricated in which a number of improved features were implemented (HQ02 coils). The improvements were partly validated with the successful test of an HQ02 coil in a mirror structure, which reached 97% of the short sample. Here, we review the modifications in the coil design and the coil fabrication process, report the issues met during the fabrication, give details of the few differences that exist within the set of HQ02 coils, and discuss a list of further improvements that will be implemented in a third series of HQ coils. [ABSTRACT FROM PUBLISHER]

The LHC Accelerator Research Program (LARP) has been engaged in the fabrication of the 3.7 m long quadrupole magnet LQS01 in order to demonstrate that Nb3Sn magnets are a viable option for future LHC Luminosity upgrades. The LQS01 design, a scale-up of the 1 m long Technology Quadrupole TQS, includes four 3.4 m long cos(theta) coils contained in a support structure based on four 1 m long aluminum shells pre-tensioned with water-pressurized bladders (shell-type structure). In order to verify assembly procedures and loading operations, the structure was pre-stressed around solid aluminum "dummy coils" and cooled-down to 77 K. Mechanical behavior and stress variations were monitored with strain gauges mounted on the structure and on the dummy coils. The dummy coils were then replaced with Nb3Sn coils in a second assembly and loading procedure, in preparation for the cool-down and test. This paper reports on the cool-down test with dummy coils and on the assembly and loading of LQS01, with a comparison between 3D finite element model predictions and strain gauge data. [ABSTRACT FROM AUTHOR]

The 3.7 m long quadrupole magnet LQS01 represents a major step of the US LHC Accelerator Research Program (LARP) towards the development of long Nb3Sn accelerator quadrupole magnets for a LHC Luminosity upgrade. The magnet support structure is a scale up of the 1 m long Technology Quadrupole TQS design with some modifications suggested by TQS model test results. It includes an aluminum shell pre-tensioned over iron yokes using pressurized bladders and locking keys (bladder and key technology). The axial support is provided by two stainless steel end plates compressed against the coil ends by four stainless steel rods. The structure, instrumented with strain gauges, has been fabricated and assembled around four aluminum "dummy coils" to determine pre-load homogeneity and mechanical characteristics during cool-down. After presenting the main magnetic and mechanical parameters of LQS01, we report in this paper on the design, assembly, and test of the support structure, with a comparison between strain gauges data and 3D finite element model results. [ABSTRACT FROM AUTHOR]

A series of tests has been performed at Lawrence Berkeley National Laboratory (LBNL) and Fermi National Accelerator Laboratory (FNAL) with the goal of assessing the influence of coil axial pre-load on Nb3 Sn magnet training. The tests involved two subscale Nb3 Sn magnets: SQ02, a quadrupole magnet fabricated as part of the US LHC Accelerator Research Program (LARP), and SD01, a dipole magnet developed in collaboration between CEA/Saclay and LBNL. Both magnets used similar Nb3 Sn flat racetrack coils from LBNL Subscale Magnet Program, and implemented an axial support system composed of stainless steel end-plates and aluminum rods. The system was designed to withstand full longitudinal electro-magnetic forces and provide controllable preloads. Quench performances, training, and quench locations have been recorded in various axial loading conditions. Test results are reported. [ABSTRACT FROM AUTHOR]

This paper describes the development and test of TQC01b and TQC02E, the second and third models in the TQC series. ANSYS analysis of the mechanical structure, its underlying assumptions, and changes based on experience with TQC01 are presented and discussed. Construction experience, in-process measurements, and modifications to the assembly since TQC01 are described. The test results presented here include magnet strain and quench performance during training of TQC01b and TQC02E. [ABSTRACT FROM AUTHOR]

The LHC Accelerator Research Program (LARP) is currently developing 4 m long Nb3 Sn quadrupole magnets for a possible upgrade of the LHC Interaction Regions (IR). In order to provide a reliable test bed for the fabrication and test of long Nb,3Sn coils, LARP has started the development of the long racetrack magnet LRS01. The magnet is composed of two 3.6 m long racetrack coils contained in a support structure based on an aluminum shell pre-tensioned with water-pressurized bladders and interference keys. For the phase-one test of the assembly procedure and loading operation, the structure was pre-stressed at room temperature and cooled down to 77 K with instrumented, solid aluminum "dummy coils". Mechanical behavior and stress homogeneity were monitored with strain gauges mounted on the shell and the dummy coils. The dummy coils were replaced with reacted and impregnated Nb3 Sn coils in a second assembly procedure, followed by cool-down to 4.5 K and powered magnet test. This paper reports on the assembly and loading procedures of the support structure as well as the comparison between strain gauge data and 3-D model predictions. [ABSTRACT FROM AUTHOR]

Test results are reported on four quadrupole magnet model tests (TQS01a, TQS01b, TQS01c, TQS02) in support of the development of a large-aperture Nb3 Sn superconducting quadrupole for the US LHC Accelerator Research Program (LARP). All four magnet assemblies used key and bladder technology to compress and support the coils within an iron yoke and an aluminum shell. The first three models tested different magnet assemblies of several coils, having MJR conductor, and gapped segmented bronze pole-islands. TQS02's coils utilized improved (RRP) Nb3 Sn conductor, and addressed TQS01's quench-training pattern, by utilizing titanium alloy (TiA16V4) pole-islands, with no axial gaps during reaction. This paper summarizes the assembly, cool-down and performance of TQS01a, TQS01b, TQS01c, and TQS02 and compares measurements with design expectations. [ABSTRACT FROM AUTHOR]

Development of high-performance Nb3 Sn quadrupoles is one of the major goals of the LHC Accelerator Research Program (LARP). As part of this program, long racetrack magnets were made in order to ~heck the fabrication steps for long Nb3 Sn coils, that the changes in coil length that take place during reaction and cooldown are correctly accounted for in the quadrupole design, and the use of a long aluminum shell for the support structure. This paper reports the construction of the first long Nb3 Sn magnet with racetrack coils 3.6 m long. The magnet reached a nominal "plateau" at 9596 A after five quenches. This is about 90% of the estimated conductor limit. The peak field in the coils at this current was 11 T. [ABSTRACT FROM AUTHOR]

It can be shown that, by superposing two solenoid-like thin windings that are oppositely skewed (tilted) with respect to the bore axis, the combined current density on the surface is ‘cos-theta’ like and the resulting magnetic field in the bore is a pure dipole. As a proof of principle, such a magnet was designed, built and tested as part of a summer undergraduate intern project. The measured field in the 25 mm bore, 4 single strand layers using NbTi superconductor, exceeded 1 T. The simplicity of this high field quality design, void of typical wedges end-spacers and coil assembly, is especially suitable for insert-coils using High Temperature Superconducting wire as well as for low cost superconducting accelerator magnets for High Energy Physics. Details of the design, construction and test are reported. [ABSTRACT FROM AUTHOR]

Development of high-performance Nb3Sn quadrupoles is one of the major goals of the LHC Accelerator Research Program (LARP). As part of this program, long racetrack magnets are being made in order to check that the change in coil length that takes place during reaction is correctly accounted for in the quadrupole design and to check for length effects in implementing the ‘shell’ method of coil support. To check the racetrack magnet manufacturing plan, a short racetrack magnet is being made. This magnet will be the first to use restack-rod process Nb3Sn, making it a ‘long sample’ test vehicle for this new material. The paper reports the reaction and characterization of the Nb3Sn, and construction features and test results from the short racetrack magnet. The paper also reports on the status of the construction of the first long racetrack magnet. [ABSTRACT FROM AUTHOR]

As part of the LHC Accelerator Research Program (LARP), three US national laboratories (BNL, FNAL, and LBNL) are currently engaged in the development of superconducting magnets for the LHC Interaction Regions (IR) beyond the current design. As a first step towards the development of long Nb3Sn quadrupole magnets, a 3.6 m long structure, based on the LBNL Subscale Common-Coil Magnet design, will be fabricated, assembled, and tested with aluminum-plate ‘dummy coils’. The structure features an aluminum shell pre-tensioned over iron yokes using pressurized bladders and locking keys (bladder and key technology). Pre-load homogeneity and mechanical responses are monitored with pressure sensitive films and strain gauges mounted on the aluminum shell and the dummy coils. The details of the design and fabrication are presented and discussed, and the expected mechanical behavior is analysed with finite element models. [ABSTRACT FROM AUTHOR]

The US LHC Accelerator Research Program (LARP) is developing Nb3Sn accelerator magnets for a possible LHC luminosity upgrade. As part of the LARP supporting R&D, a subscale racetrack quadrupole magnet (SQ) has been developed in order to provide a cost effective tool for technology development studies. The first magnet (SQ01), reported earlier, was tested as a proof-of-principle model that applied for the first time LBNL shell-based loading structure to Nb3Sn racetrack coils in a quadrupole configuration. The new loading structure, pre-loaded with water-pressurized bladders and keys, provided predictable and controllable pre-stress to four subscale racetrack coils, both in the end region and across the straight section. A second magnet (SQ02) has been recently completed, with the goal of assessing the conductor performance and the influence of the coil axial support on training. SQ02 implements four new coils wound around aluminum bronze islands and instrumented with voltage taps and spot heaters, in order to monitor quench locations and propagation velocities. This paper reports the SQ02 test results, including magnet quench performance with respect to short sample expectations, training history, and quench locations. [ABSTRACT FROM AUTHOR]

As a first step toward the development of a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, two-layer technological quadrupole models (TQS01 at LBNL and TQC01 at Fermilab) are being constructed within the framework of the US LHC Accelerator Research Program (LARP). Both models use the same coil design, but have different coil support structures. This paper describes the TQC01 design, fabrication technology and summarizes its main parameters. [ABSTRACT FROM AUTHOR]

The US LHC Accelerator Research Program (LARP) is developing Nb3Sn accelerator magnet technology for the LHC luminosity upgrade. Two 90 mm ‘Technology Quadrupole’ models (TQS01, TQC01) are being developed in close collaboration between LBNL and FNAL, using identical coil design, but two different support structures. The TQS01 structure was developed and tested at LBNL. With this approach coils are supported by an outer aluminum shell and assembled using keys and bladders. In contrast, the second model TQC01, utilize stainless steel collars and a thick stainless steel skin. This paper describes the TQS01 model magnet, its 3D ANSYS stress analysis, and anticipated instrumentation and assembly procedure. [ABSTRACT FROM AUTHOR]

The US LHC Accelerator Research Program (LARP) consists of four US laboratories (BNL, FNAL, LBNL, and SLAC) collaborating with CERN to achieve a successful commissioning of the LHC and to develop the next generation of Interaction Region magnets. In 2004, a large aperture Nb3Sn racetrack quadrupole magnet (SQ01) has been fabricated and tested at LBNL. The magnet utilized four subscale racetrack coils and was instrumented with strain gauges on the support structure and directly over the coil's turns. SQ01 exhibited training quenches in two of the four coils and reached a peak field in the conductor of 10.4 T at a current of 10.6 kA. After the test, the magnet was disassembled, inspected with pressure indicating films, and reassembled with minor modifications. A second test (SQ01b) was performed at FNAL and included training studies, strain gauge measurements and magnetic measurements, Magnet inspection, test results, and magnetic measurements are reported and discussed, and a comparison between strain gauge measurements and 3D finite element computations is presented. [ABSTRACT FROM AUTHOR]

In 2004, the US DOE established the LHC Accelerator Research Program (LARP) with the goal of developing a technology base for future upgrades of the LHC. The focus of the magnet program, which is a collaboration of three US laboratories, BNL, FNAL and LBNL, is an development of high gradient quadrupoles using Nb3Sn superconductor. Other program components address issues regarding magnet design, radiation-hard materials, long magnet scale-up, quench protection, fabrication techniques and conductor and cable R&D. This paper presents an overall view of the program with emphasis on the current quadrupole project and outlines the long-term goals of the program. [ABSTRACT FROM AUTHOR]

The strain in a high field Nb3Sn coil was measured during magnet assembly, cool-down, excitation and spot heater quenches. Strain was measured with a full bridge strain gauge mounted directly over the turns and impregnated with the coil. Two such coils were placed in a "common coil" fashion capable of reaching 11 T at 4.2 K. The measured steady state strain in the coil is compared with results obtained using the FEM code ANSYS. During quenches, the transient strain (due to temperature rise) was also measured and compared with the calculated mechanical time response to a quench. [ABSTRACT FROM AUTHOR]

Building accelerator quality magnets using Nb3Sn for next generation facilities is the challenge of the next decade. The Superconducting Magnet Group at LBNL has developed an innovative support structure for high field magnets. The structure is based on an aluminum shell over iron yokes using hydraulic bladders and locking keys for applying the pre-stress. At cool down the pre-stress is almost doubled due to the differences of thermal contraction. This new structure allows precise control of the pre-stress with minimal spring back and conductor over-stress. At present the support structure has been used with prototype magnets up to one meter in length. In this paper, the design of a 4-meter long, 11 Tesla, wind-and-react racetrack dipole will be presented as a possible step toward the fabrication of long Nb3Sn accelerator magnets. [ABSTRACT FROM AUTHOR]

The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb3Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb3Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are pre-stressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed. [ABSTRACT FROM AUTHOR]

During a quench, significant temperatures can arise as a magnet's stored energy is dissipated in the normal zone. Temperature gradients during this process give rise to localized strains within the coil. Reactive forces in the magnet structure balance the electromagnetic and thermal forces and maintain on equilibrium. In this paper we present a complete 3D finite element analysis of a racetrack coil. Specifically, the analysis focuses on thermal, electrical and mechanical conditions in a 10 T Nb3Sn coil built and tested as part of LBNL's Subscale Magnet Program. The study at- tempts to simulate time history of the temperature and voltage rise during quench propagation. The transient thermal stress after the quench is then evaluated and discussed. [ABSTRACT FROM AUTHOR]