Analysis of Nb3Sn Accelerator Magnet Training Stoynev, Stoyan; Riemer, Kevin; Zlobin, Alexander V. ...
IEEE transactions on applied superconductivity,
08/2019, Letnik:
29, Številka:
5
Journal Article
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Nb 3 Sn accelerator magnet technology has made significant progress during the past decades. For the first time, it is planned to be used in a real accelerator. A relatively small number of Nb 3 Sn ...quadrupoles and dipoles will be installed in the Large Hadron Collider (LHC) to increase machine luminosity. Although it will prove the possibility of using Nb 3 Sn magnets in real machines, many questions of scaling this technology up remain. One of them is related to slow training of Nb 3 Sn magnets compared to the traditional Nb-Ti accelerator magnets. Since the goal is to operate thousands of Nb 3 Sn magnets in a future post-LHC accelerator, the slow training will affect both the practical design margin and the nominal operation field. Consequently, the cost of the project to reach the design field level is also increased. To improve our understanding of slow magnet training the existing Fermilab data from Nb 3 Sn magnet tests were reanalyzed. A summary of coil training features and correlations with fabrication parameters observed is presented in this paper.
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 Nb 3 Sn 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.
The High Energy Accelerator Research Organization (KEK) has been developing a Nb 3 Al and Nb 3 Sn subscale magnet to establish the technology for a high-field accelerator magnet. The development ...goals are a feasibility demonstration for a Nb 3 Al cable and the technology acquisition of magnet fabrication with Nb 3 Al superconductors. KEK developed two double-pancake racetrack coils with Rutherford-type cables composed of 28 Nb 3 Al wires processed by rapid heating, quenching, and transformation in collaboration with the National Institute for Materials Science and the Fermi National Accelerator Laboratory. The magnet was fabricated to efficiently generate a high magnetic field in a minimum-gap common-coil configuration with two Nb 3 Al coils sandwiched between two Nb 3 Sn coils produced by the Lawrence Berkeley National Laboratory. A shell-based structure and a "bladder and key" technique have been used for adjusting coil prestress during both the magnet assembly and the cool down. In the first excitation test of the magnet at 4.5 K performed in June 2014, the highest quench current of the Nb 3 Sn coil, i.e., 9667 A, was reached at 40 A/s corresponding to 9.0 T in the Nb 3 Sn coil and 8.2 T in the Nb 3 Al coil. The quench characteristics of the magnet were studied.
High magnetic field dipole magnets are the enabling technology for future colliders surpassing the energy reach of LHC. The effectiveness of the common-coil layout, featuring flat racetrack coils ...shared between the two magnetic apertures, is investigated here. Potential advantages include the use of flat cables and larger bending radius at the coil ends. However, the vertical arrangement of the two apertures is less efficient than the traditional case with the two apertures placed side by side, from both the magnetic and mechanical standpoint. In this study, we attempt to address these challenges and provide an attractive and compact common-coil design in the field and aperture range of interest. The design choices aim at achieving a limited number of turns and layers, good quench protection performance, and low operating voltage. Key performance parameters such as maximum field as a function of superconductor volume and overall magnet size, field quality, Lorentz forces acting on the coils, and quench protection in the accelerator will be discussed.
Intensive magnet R&D efforts are underway to meet the requirements of future colliders and enable new discoveries in High Energy Physics. The LHC luminosity upgrade provides the opportunity to refine ...the results obtained in proof-of-principle high-field hbox Nb 3 hbox Sn models and extend them to full-size production magnets, suitable for operation in a challenging accelerator environment. Starting in 2004, the U.S. LHC Accelerator Research Program has developed large aperture hbox Nb 3 hbox Sn quadrupole models of progressively increasing performance and complexity, with particular emphasis on addressing length scale-up and accelerator quality issues. Significant contributions to this R&D effort were also provided by CERN, initially through magnet assembly and test, and later expanding to coil design and fabrication. At this time, the program is completing the technology demonstration phase and transitioning toward prototyping and production. Key achievements to date and remaining challenges are discussed.
Intensive magnet R&D efforts are underway to meet the requirements of future colliders and enable new discoveries in High Energy Physics. The LHC luminosity upgrade provides the opportunity to refine ...the results obtained in proof-of-principle high-field Formula Omitted models and extend them to full-size production magnets, suitable for operation in a challenging accelerator environment. Starting in 2004, the U.S. LHC Accelerator Research Program has developed large aperture Formula Omitted quadrupole models of progressively increasing performance and complexity, with particular emphasis on addressing length scale-up and accelerator quality issues. Significant contributions to this R&D effort were also provided by CERN, initially through magnet assembly and test, and later expanding to coil design and fabrication. At this time, the program is completing the technology demonstration phase and transitioning toward prototyping and production. Key achievements to date and remaining challenges are discussed.
This paper reports the commissioning of the vertical magnetic measurement system and the room temperature (warm) and cryogenic (cold) magnetic field measurements of the first full-length (4.2 m) ...quadrupole built by the U.S. Accelerator Upgrade Project (AUP) (formerly the LARP collaboration) for the high luminosity upgrade of the Large Hadron Collider at CERN. The magnet, designated MQXFAP2, is a prototype preceding production for the AUP which will provide ten sets of 8.4-m superconducting insertion region quadrupoles for the Hi-Lumi Upgrade. The quadrupoles will be built by assembling two 4.2-m magnets in a single cryostat. Agreement between Brookhaven National Laboratory's (BNL's) and Lawrence Berkeley National Laboratory's (LBNL's) warm measurement data has indicated that the upgraded vertical magnetic measurement system at Brookhaven National Laboratory is ready for MQXFA magnet production testing. The cold magnetic measurement has been performed and preliminary data analysis has been conducted.
Cable and magnet applications require bending REBa 2 Cu 3 O 7-δ (REBCO, RE = rare earth) tapes around a former to carry high current or generate specific magnetic fields. With a high aspect ratio, ...REBCO tapes favor the bending along their broad surfaces (easy way) than their thin edges (hard way). The easy-way bending forms can be effectively determined by the constant-perimeter method that was developed in the 1970s to fabricate accelerator magnets with flat thin conductors. The method, however, does not consider the strain distribution in the REBCO layer that can result from bending. Therefore, the REBCO layer can be overstrained and damaged even if it is bent in an easy way as determined by the constant-perimeter method. To address this issue, we developed a numerical approach to determine the strain in the REBCO layer using the local curvatures of the tape neutral plane. Two orthogonal strain components are determined: the axial component along the tape length and the transverse component along the tape width. These two components can be used to determine the conductor critical current after bending. The approach is demonstrated with four examples relevant for applications: a helical form for cables, forms for canted cos θ dipole and quadrupole magnets, and a form for the coil end design. The approach allows us to optimize the design of REBCO cables and magnets based on the constant-perimeter geometry and to reduce the strain-induced critical current degradation.
The Nb<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>Sn based test facility dipole magnet (TFD), with a rectangular aperture of 100 × 150 mm, and an operation target bore ...field of 15 T at 1.9 K, is designed to provide a background dipole field for cables and inserts. The design of the magnet is based on four double-layer coils and an aluminum shell-based structure, using key-and-bladder technology, with axial pre-load. The status of the magnet design, and optimization analyses, are here presented. The results of the initial prototyping, initial winding tests, characterization of cable hard-way bend curvature, and layer jump prototype test are also discussed.
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