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A test facility dipole is being developed at LBNL, targeting a 16 T field in a 144 mm wide aperture. The magnet uses a block design, with two double-pancake coils. In order to minimize motion under the large Lorentz forces, the coils are preloaded against a thick aluminum shell and iron yoke using bladder and key technology. It is then crucial to verify that the performance of the magnet is not degraded due to strain induced on the Nb3Sn conductor during assembly, cool-down and powering. The critical current of extracted strands was measured in a varying background magnetic field and as a function of the applied longitudinal strain. Finite element analysis was used to extract the strain state inside the superconducting strands during magnet assembly and operation. This strain was then compared to the measurements to evaluate potential reversible and irreversible effects on the magnet performances. The results suggest that the magnet can reach 16 T with sufficient margin, with no irreversible degradation in the high field region.

The U.S. High-Luminosity LHC Accelerator Upgrade Project (HL-LHC AUP) is developing MQXFA magnets, a series of 4.5 m long 150 mm aperture high-field Nb$_{3}$Sn quadrupole magnets for the HL-LHC upgrade at CERN. Five pre-series magnets, MQXFA03 through MQXFA07, have been developed. During the magnet assembly stage, we perform magnetic measurements on the coil-pack sub-assembly and magnets after loading to track the field quality for two purposes. First, it serves as a quality assurance tool to check if the magnet field quality is on track to meet the acceptance criteria. Magnetic measurements are used to understand if magnetic shims are needed to compensate low-order field errors and to meet the field quality targets. Second, the measurements during the assembly stage can also help understand the field quality, especially the geometric field errors, for Nb$_{3}$Sn accelerator magnets. Here we summarize the measurement results of the pre-series MQXFA magnets, including the magnetic axis and twist angle. The results will provide useful feedback for the series production of Nb$_{3}$Sn magnets and on the optimization of field quality of accelerator magnets based on the wind-and-react Nb$_{3}$Sn technology.

Fast quench detection is a key requirement for the successful implementation of superconducting magnet technology. In high temperature superconductor magnets, this issue is especially challenging due to the low quench propagation velocity, and presently represents one of the main factors limiting their application. A new detection technique based on stray-capacitance monitoring is proposed. The capacitance between electrically-insulated magnet elements, such as magnet structure and end parts, is utilized as an indication of local heat deposition in the conductor. In fact, the relative permittivity of helium drops when it changes from the liquid to the gaseous phase. Thus, when heating occurs, part of the helium impregnating the insulation layers boils off, and the monitored stray-capacitance decreases. The proposed technique is successfully demonstrated on three small-scale Bi-2212 magnets manufactured at the Lawrence Berkeley National Laboratory. Results from the detection of thermal runaways and spot-heater induced quenches are reported and discussed. Advantages and limitations of the stray-capacitance method with respect to conventional quench detection methods are assessed.

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.

A large aperture Nb 3 Sn dipole is proposed to replace the magnet assembly of EDIPO, which was irreversibly damaged in 2016. The goal is to generate a background field of 15 T at 4.2 K in a clear aperture of approximately 100×150 mm 2 and over a uniform length of 1000 mm in order to test superconducting cables for both fusion and high-energy physics applications. The magnet features a block-type coil design wound with wide Rutherford cable (two alternative coil cross sections are considered) and supported by a mechanical structure based on keys-and-bladders technology. In the end regions, the coils tilt up (flare) through a hard-way bend of the cables to provide room for the test well, following a layout already adopted in the LBNL HD2 and CERN-CEA FRESCA2 magnets. The two considered coil design alternatives aim at minimizing the mechanical stress in the coil windings. One coil pack design makes the use of two double pancake coils per pole, whereas the other alternative features three double pancakes per pole. Both design options are presented focusing on the results of numerical computations carried out with finite-element models to investigate peak stresses in the coils during room-temperature pre-loading, cool down, and powering.

Among the components to be upgraded in LHC interaction regions for the HiLumi-LHC projects are the inner triplet (or low-β) quadrupole magnets, denoted as Q1, Q2a, Q2b, and Q3. The new quadrupole magnets, called MQXF, are based on Nb3Sn superconducting magnet technology and operate at a gradient of 132.6 T/m, with a conductor peak field of 11.4 T. Q1 and Q3 are composed of magnets (called MQXFA) fabricated by the U.S. Accelerator Upgrade Project (AUP), with a magnetic length of 4.2 m. Q2a and Q2b consist of magnets (called MQXFB) fabricated by CERN, with a magnetic length of 7.15 m. After a series of short models, constructed in close collaboration by the US and CERN, the development program is now entering in the prototyping phase, with CERN on one side and BNL, FNAL, and LBNL on the other side assembling and testing their first long magnets We provide in this paper a description of the status of the MQXF program, with a summary of the short model test results, including quench performance, and mechanics, and an update on the fabrication, assembly, and test of the long prototypes.

The U.S. High-Luminosity LHC Accelerator Upgrade Project, in collaboration with CERN, is developing Nb 3 Sn quadrupole magnets (MQXFA) to be installed at the interaction region of the LHC. The project will deliver 20 MQXFA magnets in 10 cold masses. These magnets need to meet the stringent requirements on field quality at the nominal operating current. Compared to the mature NbTi accelerator magnet technology, achieving excellent field quality can be challenging for Nb 3 Sn magnets. To help track, understand, and allow effective correction of geometric field errors, field quality measurements at room temperature during the MQXFA assembly stage was planned for the project. The measurements also intend to evaluate the magnetic axis and twist angle along the magnet aperture. We report the first measurement on a prototype MQXFA magnet using a recently developed measurement system. The magnetic axis and twist angle met the acceptance criteria. Further development needs for the room-temperature measurements were discussed. We expect that statistics obtained from such measurements throughout the project will provide insight into future applications of high-performance Nb 3 Sn accelerator magnets.

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.

The European Organization for Nuclear Research (CERN) and U.S. LHC Accelerator Research Program (LARP) are jointly developing Nb-3Sn quadrupole magnets to be installed in the LHC for its upgrade to higher luminosity. These magnets' quench protection system will include a combination of quench heaters attached to the coil surfaces and coupling-loss-induced quench (CLIQ) units electrically connected to the magnets. Different protection elements have been characterized separately and simultaneously by implementing them on two 1.2-m-long model quadrupole magnets, tested at Fermi National Acceleration Laboratory and CERN, and one 4-m-long mirror magnet tested at Brookhaven Nation Laboratory. After analyzing the test data, their performances have been positively evaluated. Furthermore, the electrothermal transients occurring after a quench have been simulated with the LEDET software and the results are compared to experimental results. The preferred quench protection system configuration relies both on heaters and CLIQ. This solution is based on electrically robust components, achieves an effective reduction of the coils hot spot temperature after a quench, and offers increased redundancy against component failures.

Cable and magnet applications require bending REBa2 Cu3O 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 U.S. LHC Accelerator Research Program (LARP) quadrupole HQ02 was designed and fully tested as part of the low-beta quad development for Hi-Lumi LHC. HQ02's design is well documented with full fabrication accounting along with full field analysis at low and high current. With this history, HQ02 is an excellent test bed for developing a methodology for measuring turn locations from magnet cross sections and comparing with CAD models and measured field. All four coils of HQ02 were cut in identical locations along the magnetic length corresponding to magnetic field measurement and coil metrology. A real-time camera and coordinate measuring equipment was used to plot turn corners. Measurements include systematic and random displacements of winding blocks and individual turns along the magnetic length. The range of cable shifts and the field harmonic range along the length are in agreement, although correlating turn locations and measured harmonics in each cross section is challenging.

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.

The US LHC Accelerator Research Program is constructing prototype interaction region quadrupoles as part of the US in-kind contribution to the Hi-Lumi LHC project. The low-beta MQXFA Q1/Q3 coils have a 4-m length and a 150 mm bore. The design was previously validated on short, one meter models (MQXFS) developed as part of the longstanding Nb3Sn quadrupole R&D by LARP in collaboration with CERN. In parallel, facilities and tooling are being developed and refined at BNL, LBNL, and FNAL to enable long coil production, assembly, and cold testing. Long length scale-up is based on the experience from the LARP 90-mm aperture (TQ-LQ) and 120-mm aperture (HQ and Long HQ) programs. A 4-m long MQXF practice coil was fabricated to verify procedures, parts, and tooling. In parallel, the first complete prototype coil (QXFP01a) was fabricated and assembled in a long magnetic mirror, MQXFPM1, to provide early feedback on coil design and fabrication following the successful experience of previous LARP mirror tests.

Chapter 3 in High-Luminosity Large Hadron Collider (HL-LHC) : PreliminaryDesign Report. The Large Hadron Collider (LHC) is one of the largest scientificinstruments ever built. Since opening up a new energy frontier for explorationin 2010, it has gathered a global user community of about 7,000 scientistsworking in fundamental particle physics and the physics of hadronic matter atextreme temperature and density. To sustain and extend its discovery potential,the LHC will need a major upgrade in the 2020s. This will increase itsluminosity (rate of collisions) by a factor of five beyond the original designvalue and the integrated luminosity (total collisions created) by a factor ten.The LHC is already a highly complex and exquisitely optimised machine so thisupgrade must be carefully conceived and will require about ten years toimplement. The new configuration, known as High Luminosity LHC (HL-LHC), willrely on a number of key innovations that push accelerator technology beyond itspresent limits. Among these are cutting-edge 11-12 tesla superconductingmagnets, compact superconducting cavities for beam rotation with ultra-precisephase control, new technology and physical processes for beam collimation and300 metre-long high-power superconducting links with negligible energydissipation. The present document describes the technologies and componentsthat will be used to realise the project and is intended to serve as the basisfor the detailed engineering design of HL-LHC.

The U.S. LHC Accelerator Research Program (LARP) and CERN are combining efforts for the HiLumi-LHC upgrade to design and fabricate 150-mm-aperture interaction region quadrupoles with a nominal gradient of 130 T/m using Nb3Sn. To successfully produce the necessary long MQXF triplets, the HiLumi-LHC collaboration is systematically reducing risk and design modification by heavily relying upon the experience gained from the successful 120-mm-aperture LARP HQ program. First-generation MQXF short (MQXFS) coils were predominately a scaling up of the HQ quadrupole design, allowing comparable cable expansion during Nb3Sn formation heat treatment and increased insulation fraction for electrical robustness. A total of 13 first-generation MQXFS coils were fabricated between LARP and CERN. Systematic differences in coil size, coil alignment symmetry, and coil length contraction during heat treatment are observed and likely due to slight variances in tooling and insulation/cable systems. Analysis of coil cross sections indicate that field-shaping wedges and adjacent coil turns are systematically displaced from the nominal location and the cable is expanding less than nominally designed. A second-generation MQXF coil design seeks to correct the expansion and displacement discrepancies by increasing insulation and adding adjustable shims at the coil pole and midplanes to correct allowed magnetic field harmonics.

A robust fabrication technology is critical to achieve the high performance in YBa2Cu3O (YBCO) coils as the critical current of the brittle YBCO layer is subject to the strain-induced degradation during coil fabrication. The expected current-carrying capability of the magnet and its temperature dependence are two key inputs to the coil technology development. However, the expected magnet performance is not straightforward to determine because the short-sample critical current depends on both the amplitude and orientation of the applied magnetic field with respect to the broad surface of the tape-form conductor. In this paper, we present an approach to calculate the self-field performance limit for YBCO racetrack coils at 77 and 4.2 K. Critical current of short YBCO samples was measured as a function of the applied field perpendicular to the conductor surface from 0 to 15 T. This field direction limited the conductor critical current. Two double-layer racetrack coils, one with three turns and the other with 10 turns, were wound and tested at 77 and 4.2 K. The test coils reached at least 80% of the expected critical current. The ratio between the coil critical currents at 77 and 4.2 K agreed well with the calculation. We conclude that the presented approach can determine the performance limit in YBCO racetrack coils based on the short-sample critical current and provide a useful guideline for assessing the coil performance and fabrication technology. The correlation of the coil critical current between 77 K and 4.2 K was also observed, allowing the 77 K test to be a cost-effective tool for the development of coil technology.

A robust fabrication technology is critical to achieve the high performance in YBa2Cu3O (YBCO) coils as the critical current of the brittle YBCO layer is subject to the strain-induced degradation during coil fabrication. The expected current-carrying capability of the magnet and its temperature dependence are two key inputs to the coil technology development. However, the expected magnet performance is not straightforward to determine because the short-sample critical current depends on both the amplitude and orientation of the applied magnetic field with respect to the broad surface of the tape-form conductor. In this paper, we present an approach to calculate the self-field performance limit for YBCO racetrack coils at 77 and 4.2 K. Critical current of short YBCO samples was measured as a function of the applied field perpendicular to the conductor surface from 0 to 15 T. This field direction limited the conductor critical current. Two double-layer racetrack coils, one with three turns and the other with 10 turns, were wound and tested at 77 and 4.2 K. The test coils reached at least 80% of the expected critical current. The ratio between the coil critical currents at 77 and 4.2 K agreed well with the calculation. We conclude that the presented approach can determine the performance limit in YBCO racetrack coils based on the short-sample critical current and provide a useful guideline for assessing the coil performance and fabrication technology. The correlation of the coil critical current between 77 K and 4.2 K was also observed, allowing the 77 K test to be a cost-effective tool for the development of coil technology.

Large-aperture, high-field, Nb3Sn quadrupoles are being developed by the U.S. LHC accelerator research program (LARP) for the High luminosity upgrade of the Large Hadron Collider (HiLumi-LHC). The first 1 m long, 120 mm aperture prototype, HQ01, was assembled with various sets of coils and tested at LBNL and CERN. Based on these results, several design modifications have been introduced to improve the performance for HQ02, the latest model. From the field quality perspective, the most relevant improvements are a cored cable for reduction of eddy current effects, and more uniform coil components and fabrication processes. This paper reports on the magnetic measurements of HQ02 during recent testing at the Vertical Magnet Test Facility at Fermilab. Results of baseline measurements performed with a new multilayer circuit board probe are compared with the earlier magnet. An analysis of probe and measurement system performance is also presented.

Large-aperture, high-field, Nb3Sn quadrupoles are being developed by the U.S. LHC accelerator research program (LARP) for the High luminosity upgrade of the Large Hadron Collider (HiLumi-LHC). The first 1 m long, 120 mm aperture prototype, HQ01, was assembled with various sets of coils and tested at LBNL and CERN. Based on these results, several design modifications have been introduced to improve the performance for HQ02, the latest model. From the field quality perspective, the most relevant improvements are a cored cable for reduction of eddy current effects, and more uniform coil components and fabrication processes. This paper reports on the magnetic measurements of HQ02 during recent testing at the Vertical Magnet Test Facility at Fermilab. Results of baseline measurements performed with a new multilayer circuit board probe are compared with the earlier magnet. An analysis of probe and measurement system performance is also presented.

The discovery of a Higgs-like boson with mass near 126 GeV, at the LHC, hasreignited interest in future energy frontier colliders. We propose here aproton-proton (pp) collider in a 100 km ring, with center of mass (CM) energyof ~100 TeV which would have substantial discovery potential for new heavyparticles and new physics beyond the Standard Model. In the case that LHCexperiments have already found exotic resonances or heavy "partner" particles,this collider could fill out the "tower" of resonances (thus e.g. confirming anextra dimension) or the full suite of partner particles (e.g. forsupersymmetry). The high luminosity of the new collider would enable uniqueprecision studies of the Higgs boson (including Higgs self coupling and rareHiggs decays), and its higher energy would allow more complete measurements ofvector boson scattering to help elucidate electroweak symmetry breaking. Wealso discuss an e+e- collider in the same 100 km ring with CM energies from 90to 350 GeV. This collider would enable precision electroweak measurements up tothe ttbar threshold, and serve as a Higgs factory.

With the first test of LQS03, the long quadrupole (LQ) R&D by LARP (the US LHC Accelerator Research Program, a collaboration of BNL, FNAL, LBNL, and SLAC) is approaching conclusion. LQS03 is the third 3.7-m-long quadrupole, with 90 mm aperture, using a full new set of Nb3Sn coils. The LQS03 coils were made using 108/127 RRP strand (with 108 Nb3Sn subelements) produced by Oxford Superconducting Technology, whereas both previous models used 54/61 RRP strand (with 54 larger Nb3Sn subelements). In this paper, LQS03 test results are presented and discussed. The test results are also compared with the performances of the previous models. Observations are made for the future use of Nb3Sn in accelerator magnets. © 2002-2011 IEEE.

With the first test of LQS03, the long quadrupole (LQ) R&D by LARP (the US LHC Accelerator Research Program, a collaboration of BNL, FNAL, LBNL, and SLAC) is approaching conclusion. LQS03 is the third 3.7-m-long quadrupole, with 90 mm aperture, using a full new set of Nb3Sn coils. The LQS03 coils were made using 108/127 RRP strand (with 108 Nb3Sn subelements) produced by Oxford Superconducting Technology, whereas both previous models used 54/61 RRP strand (with 54 larger Nb3Sn subelements). In this paper, LQS03 test results are presented and discussed. The test results are also compared with the performances of the previous models. Observations are made for the future use of Nb3Sn in accelerator magnets. © 2002-2011 IEEE.

After the successful test of the first long Nb 3Sn quadrupole (LQS01) the US LHC Accelerator Research Program (LARP, a collaboration of BNL, FNAL, LBNL and SLAC) is assessing training memory, reproducibility, and other accelerator quality features of long Nb 3Sn quadrupole magnets. LQS01b (a reassembly of LQS01 with more uniform and higher pre-stress) was subjected to a full thermal cycle and reached the previous plateau of 222 T/m at 4.5 K in two quenches. A new set of four coils, made of the same type of conductor used in LQS01 (RRP 54/61 by Oxford Superconducting Technology), was assembled in the LQS01 structure and tested at 4.5 K and lower temperatures. The new magnet (LQS02) reached the target gradient (200 T/m) only at 2.6 K and lower temperatures, at intermediate ramp rates. The preliminary test analysis, here reported, showed a higher instability in the limiting coil than in the other coils of LQS01 and LQS02. © 2011 IEEE.

After the successful test of the first long Nb 3Sn quadrupole (LQS01) the US LHC Accelerator Research Program (LARP, a collaboration of BNL, FNAL, LBNL and SLAC) is assessing training memory, reproducibility, and other accelerator quality features of long Nb 3Sn quadrupole magnets. LQS01b (a reassembly of LQS01 with more uniform and higher pre-stress) was subjected to a full thermal cycle and reached the previous plateau of 222 T/m at 4.5 K in two quenches. A new set of four coils, made of the same type of conductor used in LQS01 (RRP 54/61 by Oxford Superconducting Technology), was assembled in the LQS01 structure and tested at 4.5 K and lower temperatures. The new magnet (LQS02) reached the target gradient (200 T/m) only at 2.6 K and lower temperatures, at intermediate ramp rates. The preliminary test analysis, here reported, showed a higher instability in the limiting coil than in the other coils of LQS01 and LQS02. © 2011 IEEE.

Lawrence Berkeley National Laboratory (LBNL) is developing Wind-and-React (W&R) Bi2sr2cacu2o8+δ (Bi-2212) accelerator magnet technology for insert coils, to surpass the intrinsic limitations of Nb-based magnets, and eventually develop hybrid systems that can approach 20 T dipole fields. The Bi-2212 technology is being developed in close collaboration with industry, and has been partly supported by the US Very High Field Superconducting Magnet Collaboration (VHFSMC). Steady improvements were made over the last several years, with coil HTS-SC08 reaching 2636 A, or about 85% of its witness sample critical current (Ic). Though this is still a factor 3 to 4 too low to be competitive with Nb-based materials, it is expected that the required Ic can be achieved through further conductor optimizations. Recent developments include the commissioning of infrastructure for the reaction of coils at LBNL. Earlier coils were fabricated and tested at LBNL, but were reacted at the wire manufacturer. We describe in detail the furnace calibrations and heat treatment optimizations that enable coil reactions at temperatures approaching 890 °C with a homogeneity of ± 1 °C in a pure oxygen flow. We reacted two new coils at LBNL, and tested the performance of coil HTS-SC10 at 4.2 K in self-field using a superconducting transformer system. We find that its performance is consistent with witness samples, and comparable to coil HTS-SC08, which is an identical coil that was reacted at Oxford Instruments Superconductor Technology (OST), thereby validating the in-house reaction process.

The test of the first LARP (LHC Accelerator Research Program) Long Quadrupole is a significant milestone toward the development of Nb3Sn quadrupoles for LHC (Large Hadron Collider) Luminosity Upgrades. These 3.7-m long magnets, scaled from the 1-m long Technological Quadrupoles, are used to develop our capabilities to fabricate and assemble Nb3Sn coils and structures with lengths comparable to accelerator magnet dimensions. The long quadruples have a target gradient of 200 T/m in a 90-mm aperture. Pre-stress and support are provided by an Al-shell-based structure pre-loaded using bladders and keys. The coils were fabricated at BNL and FNAL, the hell-based structure was designed and assembled at LBNL, the test is performed at FNAL. In this paper we present the final steps of the development of the first model (LQS01), several upgrades to the test facility, the test results of witness cables, and the short sample limit © 2006 IEEE.

The design of a class of short period superconducting undulators is presented. We begin with a parameter-based analysis that provides insight into potential device performance as a function of the properties of superconducting materials. We present data on candidate low-temperature superconducting materials and the motivation to consider low-copper fraction, high Jc materials. Measured data on recent Nb3Sn conductors is provided, together with wire and cable design issues that are tailored for undulator applications. Key design concerns are then addressed, in particular the quench protection system limitations and the system performance. Progress on the construction and testing of a prototype 30mm period device is described.

Lawrence Berkeley National Laboratory in collaboration with the Institute of Modern Physics has developed a Nb3 Sn-based superconducting magnet system for a fourthgeneration 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 Nb3 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. [ABSTRACT FROM AUTHOR]

A fourth generation electron cyclotron resonance ion source with an operating frequency between 40 and 56 GHz has the potential to quadruple the heavy-ion beam currents and provide a cost effective upgrade path for heavy ion drivers in use or in the planning stage at radioactive beam facilities. Design studies show it is feasible to produce the required magnetic fields in the plasma chamber, 7 T axially and 4 T in the radial direction with a magnetic structure using commercially available Nb(3)Sn superconducting materials. In this paper we describe the design of such a magnet structure including a 3D analysis of the Lorentz forces generated by the magnetic fields and the necessary clamping structure to stabilize the conductor against these forces.

Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb(3)Sn superconducting technology for several years. At the moment, Nb(3)Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb(3)Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6-7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb(3)Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13-15 T. Because of the brittleness and strain sensitivity of Nb(3)Sn, particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell pretensioned with water-pressurized bladders, and we analyze the expected coil stresses with a two-dimensional finite element mechanical model.