Characterization of insulating coatings for wind-and-react coil fabrication

Electrical insulation breakdown between conductor and coil parts and structures is a limiting factor in the performance of high-field magnets. We have evaluated various insulation coatings for possible application in both Nb Sn and Bi-2212 coil fabrication. Such coatings must be robust to maintain structural integrity and provide adequate voltage standoff after the wind-and-react coil fabrication process. Such processes are characterized by reaction temperatures of 650°C in an inert atmosphere for Nb Sn and 890°C in a pure oxygen atmosphere for Bi-2212, and down to cryogenic temperatures when coils are in service. We present a method of testing standardized samples and report the performance characteristics of oxide layers produced (or applied) by plasma-spray, surface conversion, and "paintable" coatings in common areas of voltage breakdown in coil parts. We also address material compatibility and durability during high-temperature heat treatment and cryogenic shock. Suitable coatings selected in the testing process will be instrumental in improving the performance of future wind-and-react coils. © 2014 AIP Publishing LLC. 3

Mechanical Study of a Superconducting 28-GHz Ion Source Magnet for FRIB

The superconducting electron cyclotron resonance (ECR) source magnet for the facility for rare isotope beams at Michigan State University was designed and built by the Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) in 2017. The 28 GHz NbTi ion source magnet features a sextupole-in-solenoids configuration which is comparable to the VENUS ECR magnet operated at LBNL. However, the mechanical design of this magnet utilizes a shell-based support structure which allows fine adjustments to the sextupole preload and reversibility of the magnet assembly process. The magnet has been assembled and tested to operational currents at LBNL. This paper describes the mechanical analyses performed to estimate the sextupole's and solenoids' preloads. We will report on the 3-D finite element analysis during room temperature assembly, cool-down, and magnet excitation, and then describe the magnet preload operations. Finally, we will describe the performance of the support structure during the quench training

Performance of the First Short Model 150-mm-Aperture Nb3Sn Quadrupole MQXFS for the High-Luminosity LHC Upgrade

The U.S. LHC Accelerator Research Program (LARP) and CERN combined their efforts in developing Nb Sn magnets for the high-luminosity LHC upgrade. The ultimate goal of this collaboration is to fabricate large aperture Nb Sn quadrupoles for the LHC interaction regions. These magnets will replace the present 70-mm-Aperture NbTi quadrupole triplets for expected increase of the LHC peak luminosity up to 5 × 10 cm s or more. Over the past decade, LARP successfully fabricated and tested short and long models of 90 and 120-mm-Aperture Nb Sn quadrupoles. Recently, the first short model of 150-mm-diameter quadrupole MQXFS was built with coils fabricated both by LARP and CERN. The magnet performance was tested at Fermilab's vertical magnet test facility. This paper reports the test results, including the quench training at 1.9 K, ramp rate and temperature dependence, as well as protection heater studies. 3 3 3 34 -2 -

Axial-Field Magnetic Quench Antenna for the Superconducting Accelerator Magnets

We have developed and tested a novel magnetic inductive antenna for detecting and localizing quenches and flux jumps in superconducting accelerator magnets during ramping and steady-state operations. The antenna principle is based upon sensing temporal variation of the axial field gradient in the magnet bore that is specific to propagating quench. Two antenna configurations were developed and built, optimized respectively for sensing disturbances of the off-axis (for the dipole magnet) and axial (for the quadrupole magnet) gradient of the axial field. The antennas were qualified during tests of LBNL's high-field dipole, HD3b, and LARP's Nb3Sn quadrupole HQ02b. A reliable and accurate localization of quenches and flux jumps was demonstrated. Upon ramping up the magnet current, we observed peculiar dynamics of the magnetic disturbances travelling along the cable at velocities of ∼800 m/s. Also, details of slow quench propagation in the HQ02 quadrupole at a small fraction of operational current were detected and recorded

Design and fabrication experience with Nb3 Sn block-type coils for high field accelerator dipoles

For the last several years, the Lawrence Berkeley National Laboratory has been engaged in the development of Nb3Sn block-type accelerator quality dipoles with operational bore fields in the range of 13-15 T. The magnet design features two coil modules wound around a titanium-alloy pole with a clear aperture of 43 mm. The latest model, HD3, incorporates several new features to overcome the limitations observed in previous tests. Among the key objectives are improved conductor positioning at critical transitions between straight section and end regions, and a more robust fabrication process. To date, several coils have been fabricated and we describe their performance with respect to these design and process changes. Additionally, we present our experience in design and fabrication of a new generation of magnet coils that introduce a two-piece pole design that allows for cable growth during reaction. These experiences are intended to form the basis for scale-up to longer lengths and larger aperture magnets. © 2002-2011 IEEE

Characterization of insulating coatings for wind-and-react coil fabrication

Electrical insulation breakdown between conductor and coil parts and structures is a limiting factor in the performance of high-field magnets. We have evaluated various insulation coatings for possible application in both Nb3Sn and Bi-2212 coil fabrication. Such coatings must be robust to maintain structural integrity and provide adequate voltage standoff after the wind-and-react coil fabrication process. Such processes are characterized by reaction temperatures of 650°C in an inert atmosphere for Nb3Sn and 890°C in a pure oxygen atmosphere for Bi-2212, and down to cryogenic temperatures when coils are in service. We present a method of testing standardized samples and report the performance characteristics of oxide layers produced (or applied) by plasma-spray, surface conversion, and "paintable" coatings in common areas of voltage breakdown in coil parts. We also address material compatibility and durability during high-temperature heat treatment and cryogenic shock. Suitable coatings selected in the testing process will be instrumental in improving the performance of future wind-and-react coils. © 2014 AIP Publishing LLC

Quench Protection of a Nb3Sn Superconducting Magnet System for a 45-GHz ECR Ion Source

Lawrence Berkeley National Laboratory in collaboration with the Institute of Modern Physics has developed a Nb3Sn-based superconducting magnet system for a fourth-generation electron cyclotron resonance source, with a goal of achieving the magnetic field required for operating at the microwave frequency of 45 GHz. The magnet system is composed of one sextupole magnet inside three solenoids of different sizes manufactured from Nb3Sn Sn round wire. Given the high stored energy density and relatively low wire copper fraction, the coils are not self-protected in the case of a quench. The study of the transient following a quench is carried out by means of the lumped-element dynamic electro-thermal program, which includes a detailed simulation of the interfilament coupling losses developing in the wire. Nonlinear effects occurring in the magnet, such as coupling loss and differential inductance reduction, have a significant impact on protecting these magnets. The resulting baseline quench protection strategy based on four independent energy extraction systems protecting the four magnets meets the quench protection requirements. Furthermore, in order to enhance the redundancy of the quench protection system and reduce the peak voltages to ground, the implementation of a coupling-loss induced quench (CLIQ) system is considered

Quench Protection of a Nb3Sn Superconducting Magnet System for a 45-GHz ECR Ion Source

Lawrence Berkeley National Laboratory in collaboration with the Institute of Modern Physics has developed a Nb Sn-based superconducting magnet system for a fourth-generation electron cyclotron resonance source, with a goal of achieving the magnetic field required for operating at the microwave frequency of 45 GHz. The magnet system is composed of one sextupole magnet inside three solenoids of different sizes manufactured from Nb Sn Sn round wire. Given the high stored energy density and relatively low wire copper fraction, the coils are not self-protected in the case of a quench. The study of the transient following a quench is carried out by means of the lumped-element dynamic electro-thermal program, which includes a detailed simulation of the interfilament coupling losses developing in the wire. Nonlinear effects occurring in the magnet, such as coupling loss and differential inductance reduction, have a significant impact on protecting these magnets. The resulting baseline quench protection strategy based on four independent energy extraction systems protecting the four magnets meets the quench protection requirements. Furthermore, in order to enhance the redundancy of the quench protection system and reduce the peak voltages to ground, the implementation of a coupling-loss induced quench (CLIQ) system is considered. 3

Mechanical Study of a Superconducting 28-GHz Ion Source Magnet for FRIB

The superconducting electron cyclotron resonance (ECR) source magnet for the facility for rare isotope beams at Michigan State University was designed and built by the Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) in 2017. The 28 GHz NbTi ion source magnet features a sextupole-in-solenoids configuration which is comparable to the VENUS ECR magnet operated at LBNL. However, the mechanical design of this magnet utilizes a shell-based support structure which allows fine adjustments to the sextupole preload and reversibility of the magnet assembly process. The magnet has been assembled and tested to operational currents at LBNL. This paper describes the mechanical analyses performed to estimate the sextupole's and solenoids' preloads. We will report on the 3-D finite element analysis during room temperature assembly, cool-down, and magnet excitation, and then describe the magnet preload operations. Finally, we will describe the performance of the support structure during the quench training