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This article reports the design, three-dimensional magnetostatic simulation results, coil fabrication, assembly, and low-temperature test results of a C-frame, iron-dominated high-temperature superconductor dipole magnet for ultra high vacuum magnetic-sensitive spectroscopy techniques at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. The magnet is required to provide fields up to ~1 T along two spatial directions. With an added capability to rotate about its vertical axis of symmetry, the magnet system is capable of delivering field along all three principal axes. The combination of this magnet and fast-switched, elliptically polarized soft X-rays produced by the NSLS elliptically polarized wiggler forms the basis for an excellent tool for polarization-sensitive studies of magnetic materials. The prototype magnet consists of a set of pancake coils fabricated from BSCCO tape reinforced with stainless steel. Those pancake coils are clamped in a low-carbon AISI 1006 grade steel pole and yoke assembly. For testing purposes, a cold He gas environment provided cooling the superconducting magnet to subtransition temperatures; for operation in an ultra high vacuum endstation environment, cooling can be provided by an external cryocooler. The low-temperature tests establish the safe-operating parameters needed to achieve the target magnetic field values. The measured magnetic field values are in close agreement with the magnetic simulation results, thereby confirming that the magnet design fulfills the performance requirements. The final section of this article lists some suggestions to improve the magnet performance.

Author(s): Cooley, LD; Ghosh, AK; Dietderich, DR; Pong, I | Abstract: The high-luminosity upgrade of the large hadron collider (HL-LHC) at CERN will replace the main ring inner triplet quadrupoles, identified by the acronym MQXF, adjacent to the main ring intersection regions. For the past decade, the U.S. LHC Accelerator RaD Program, LARP, has been evaluating conductors for the MQXFA prototypes, which are the outer magnets of the triplet. Recently, the requirements for MQXF magnets and cables have been published in [P. Ferracin et al., IEEE Trans. Appl. Supercond., vol. 26, no. 4, Jun. 2016, Art. no. 4000207], along with the final specification for Ti-alloyed Nb3Sn conductor determined jointly by CERN and LARP. This paper describes the rationale beneath the 0.85-mm-diameter strand's chief parameters, which are 108 or more subelements, a copper fraction not less than 52.4%, strand critical current at 4.22 K not less than 631 A at 12 T and 331 A at 15 T, and residual resistance ratio of not less than 150. This paper also compares the performance for ∼100 km production lots of the five most recent LARP conductors to the first 163 km of strand made according to theHL-LHCspecification.Two factors emerge as significant for optimizing performance and minimizing risk: a modest increase of the subelement diameter from 50 to 55 μm, and a Nb:Sn molar ratio of 3.6 instead of 3.4. The statistics acquired so far give confidence that the present conductor can balance competing demands in production for the HL-LHC project.

Author(s): Wang, X; Ambrosio, G; Chlachidze, G; DiMarco, J; Ghosh, AK; Holik, EF; Prestemon, SO; Sabbi, G; Stoynev, SE | Abstract: The U.S. large hadron collider (LHC) Accelerator Research Program, in close collaboration with The European Organization for Nuclear Research (CERN), has developed three generations of high-gradient quadrupole (HQ) Nb3Sn model magnets, to support the development of the 150 mm aperture Nb3Sn quadrupole magnets for the high-luminosity LHC. The latest generation, HQ03, featured coils with better uniformity of coil dimensions and properties than the earlier generations. The HQ03 magnet was tested at fermi national accelerator laboratory (FNAL), including the field quality study. The profiles of low-order harmonics along the magnet aperture observed at 15 kA, 1.9 K can be traced back to the assembled coil pack before the magnet assembly. Based on the measured harmonics in the magnet center region, the coil block positioning tolerance was analyzed and compared with earlier HQ01 and HQ02 magnets to correlate with coil and magnet fabrication. To study the capability of correcting the low-order nonallowed field errors, magnetic shims were installed in HQ03. The expected shim contribution agreed well with the calculation. For the persistent-current effect, the measured a4 can be related to 4% higher in the strand magnetization of one coil with respect to the other three coils. Finally, we compare the field errors due to the interstrand coupling currents between HQ03 and HQ02.

The High Luminosity (HiLumi) Large Hadron Collider (LHC) project has, as the main objective, to increase the LHC peak luminosity by a factor five and the integrated luminosity by a factor ten. This goal will be achieved mainly with a new interaction region layout, which will allow a stronger focusing of the colliding beams. The target will be to reduce the beam size in the interaction points by a factor of two, which requires doubling the aperture of the low-β (or inner triplet) quadrupole magnets. The use of Nb3Sn superconducting material and, as a result, the possibility of operating at magnetic field levels in the windings higher than 11 T will limit the increase in length of these quadrupoles, called MQXF, to acceptable levels. After the initial design phase, where the key parameters were chosen and the magnet's conceptual design finalized, the MQXF project, a joint effort between the U.S. LHC Accelerator Research Program and the Conseil Europeen pour la Recherche Nucleaire (CERN), has now entered the construction and test phase of the short models. Concurrently, the preparation for the development of the full-length prototypes has been initiated. This paper will provide an overview of the project status, describing and reporting on the performance of the superconducting material, the lessons learnt during the fabrication of superconducting coils and support structure, and the fine tuning of the magnet design in view of the start of the prototyping phase.

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 a 150 mm aperture Nb$_{3}$Sn quadrupole for the LHC interaction regions. A first series of 1.5 m long coils were fabricated and assembled in a first short model. A detailed visual inspection of the coils was carried out to investigate cable dimensional changes during heat treatment and the position of the windings in the coil straight section and in the end region. The analyses allow identifying a set of design changes which, combined with a fine tune of the cable geometry and a field quality optimization, were implemented in a new, second-generation, coil design. In this paper we review the main characteristics of the first generation coils, describe the modification in coil lay-out, and discuss their impact on parts design and magnet analysis. As part of the Large Hadron Collider (LHC) Luminosity upgrade program, the U.S.-LHC Accelerator Research Program collaboration and CERN are working together to design and build a 150-mm aperture Nb_3Sn quadrupole for the LHC interaction regions. A first series of 1.5-m-long coils was fabricated and assembled in a first short model. A detailed visual inspection of the coils was carried out to investigate cable dimensional changes during heat treatment and the position of the windings in the coil straight section and in the end region. The analyses allow identifying a set of design changes which, combined with a fine tune of the cable geometry and a field quality optimization, were implemented in a new second-generation coil design. In this paper, we review the main characteristics of the first generation coils, describe the modification in coil layout and discuss their impact on parts design and magnet analysis.

Construction and test results of a 100-mm-bore solenoid made with the high-temperature superconductor (HTS) producing a peak field of over 10 T are presented. This is the first step toward building a very high field solenoid (35-40 T)-one of the key components of the proposed state-of-the-art facility for dark matter search at the Center for Axion and Precision Physics Research, Institute for Basic Science in Korea. The coils made with HTS are expected to provide a field of ~25 T, and the coils made with low-temperature superconductors are expected to provide a field of 10-15 T. REBCO HTS tapes were provided by SuNAM along with the measurements at 20 K in 3.5- to 4-T applied field. The Brookhaven National Laboratory measured several samples at 4 K in the applied field of 4-8 T. This paper will present a series of test results of the conductor, six pancake coils, and the fully assembled solenoid.

Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, particularly at low field, where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb 3 Sn accelerator magnets. Here, a finite-element method based on the measured strand magnetization is validated using three state-of-the-art Nb 3 Sn accelerator magnets featuring different subelement diameters, conductor critical currents, magnet designs, and test temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent-current effects is discussed. The strengths, limitations, and possible improvements of the approach are also discussed.

The HQ magnet is a 120 mm aperture, 1-meter-long Nb$_{3}$Sn quadrupole developed by the LARP collaboration in the framework of the High-Luminosity LHC project. A first series of coils was assembled and tested in 5 assemblies of the HQ01 series. The HQ01e model achieved a maximum gradient of 170 T/m at 4.5 K at LBNL in 2010-2011 and reached 184 T/m at 1.9 K at CERN in 2012. A new series of coils incorporating major design changes was fabricated for the HQ02 series. The first model, HQ02a, was tested at Fermilab where it reached 98% of the short sample limit at 4.5 K with a gradient of 182 T/m in 2013. However, the full training of the coils at 1.9 K could not be performed due to a current limit of 15 kA. Following this test, the azimuthal coil pre-load was increased by about 30 MPa and an additional current lead was installed at the electrical center of the magnet for quench protection studies. The test name of this magnet changed to HQ02b. In 2014, HQ02b was then shipped to CERN as the first opportunity for full training at 1.9 K. In this paper, we present a comprehensive summary of the HQ02 test results including: magnet training at 1.9 K with increased pre-load, quench origin and propagation, and ramp rate dependence. A series of powering tests was also performed to assess changes in magnet performance with a gradual increase of the MIITs. We also present the results of quench protection studies using different setting for detection, heater coverage, energy extraction and the Coupling-Loss Induced Quench (CLIQ) system.

Next-generation particle accelerators, such as the proposed Large Hadron Collider (LHC) energy upgrade (highenergy LHC), will require very-high-field (> 20 T) superconducting magnets. This paper describes the progress toward this goal made to date as a part of a collaborative work between Particle Beam Lasers, Inc., and Brookhaven National Laboratory. To reduce the cost, high-temperature superconductors (HTSs) are used in a hybrid design with conventional low-temperature superconductors (LTSs) Nb3Sn and NbTi. The focus of this paper is on using a second generation (2G) ReBCO HTS tape in cosine-theta coil geometry. The complex ends of the cosine-theta geometry are particularly challenging for a brittle HTS tape. We report the construction and 77-K test results, one with a 4-mm and another with a 12-mm ReBCO tape, neither showing measurable degradation. This paper also presents the first successful use of Kapton CI on an HTS tape, which offers many advantages. Future plans include the construction and 4-K testing of a full cosine-theta HTS coil (first in a stand-alone mode and then in a hybrid structure with LTS coils) and the modeling and measurements of magnetization. This paper is a part of comprehensive research and development toward eventually building a high-field accelerator-quality dipole magnet.

The development of $Nb_3Sn$ 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 in-teraction regions (IR). The inner triplet (low-β) NbTi quadrupoles in the IR will be replaced by the stronger Nb$_{3}$Sn magnets boosting the LHC program of having 10-fold increase in integrated luminos-ity after the foreseen upgrades. Previously LARP conducted suc-cessful 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 strong performance at the Fermilab’s verti-cal 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 depend-ence, is also summarized. The development of Nb$_{3}$Sn 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 Nb$_{3}$Sn 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 Fermilab's 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.

The U.S. LHC Accelerator Research Program (LARP) and CERN combined their efforts in developing Nb3Sn magnets for the high-luminosity LHC upgrade. The ultimate goal of this collaboration is to fabricate large aperture Nb 3Sn 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 × 1034 cm –2s–1 or more. Over the past decade, LARP successfully fabricated and tested short and long models of 90 and 120-mm-aperture Nb3Sn 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.

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 is first validated on short, one meter models (MQXFS) developed as part of the longstanding Nb$_{3}$Sn 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, water jet cut and analyzed 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.

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 U.S. LHC Accelerator Research Program has been developing Nb3Sn quadrupole magnets of progressively increasing performance and complexity for the High-Luminosity LHC project. The magnets are wound with Rutherford cables following the wind-and-react process. The resulting inter-strand coupling can generate strong field distortions during current ramp. The latest series of 120 mm aperture magnets (HQ) are designed and built for high field quality, offering an opportunity for detailed studies of these effects. Magnetic measurements of first-generation HQ magnets showed strong ramp-rate dependence. A stainless-steel core was introduced for the second generation of magnet coils to control the inter-strand coupling currents and the resulting dynamic multipoles. We report the observed dynamic effects and compare with calculations taking into account the coil geometry and cross-contact resistance in the Rutherford cable. In particular, the dependence of field quality on width and position of the stainless steel core is discussed.

The proposed muon collider requires very high field solenoids in the range of 30-50 T. The use of High Temperature Superconductors (HTS) operating at low temperature (~ 4 K) is essential for achieving such high fields in a superconducting magnet. As a part of this program, we have built and successfully tested a 25 mm aperture HTS insert generating 16 T peak field (the highest field ever achieved in an all-HTS magnet), a 100 mm aperture HTS midsert generating 9 T peak field, and designed an outsert with a conventional Low Temperature Superconductor (LTS) to provide additional field. In addition to presenting the test results and progress made in support technologies, we will also discuss a number of challenges associated with the high field HTS magnets. Finally, we present a set of strategies to overcome some of those challenges.

In preparation for the high luminosity upgrade of the Large Hadron Collider (LHC), the LHC Accelerator Research Program (LARP) is developing a new generation of large aperture high-field quadrupoles based on Nb3Sn technology. One meter long and 120 mm diameter HQ quadrupoles are currently produced as a step toward the eventual aperture of 150 mm. Tests of the first series of HQ coils revealed the necessity for further optimization of the coil design and fabrication process. A new model (HQ02) has been fabricated with several design modifications, including a reduction of the cable size and an improved insulation scheme. Coils in this magnet are made of a cored cable using 0.778 mm diameter Nb3Sn strands of RRP 108/127 subelement design. The HQ02 magnet has been fabricated at LBNL and BNL, and then tested at Fermilab. This paper summarizes the performance of HQ02 at 4.5 K and 1.9 K temperatures.

ICU remains for Intensive Care Unit, a place in the recuperating office where wiped out patients are checked eagerly. Commonly, the patient-staff extent is low and the LIFE-SAVING EQUIPMENT used is outstandingly bleeding edge Generally ICU is a healing facility for course of action of genuine nursing and remedial consideration of essentially wiped out patients, depicted by high bore and measure of unending nursing and restorative supervision and by use of cutting edge checking and resuscitative equipment The patients in the ICU require a predictable seeing of their Temperature and pulse circulatory strain. This undertaking is a working model, which wires sensors to evaluate imperative parameters specifically the Temperature, Respiratory temperature and Heart Beat. The sensors are interfaced to PC, with the objective that the condition of a patient can be explored by masters in any bit of the center wherever they are. At whatever point there is a variety from the standard felt by the patient, the particular patient will give an alert movement, by which the pro can race to the patient. Despite when the patient is in a careless condition, each one of the parameters will be identified and pro will be admonished, thusly it diminishes master's remaining task at hand and besides gives more correct results .Our endeavor is a working model which wires sensors to measure each one of these parameters like body temperature, Respiratory Temp and Heart Beat rate and trade it to the PC, with the objective that the patient condition can be examined to by authorities in any bit of the recuperating focus wherever they are. In this way it decreases experts work stack and besides gives more exact results, wherever there is a variety from the standard felt by the patient, we have in like manner combined saline watching system which gives an alert when the saline container going to cleanse.

The US LHC Accelerator Research Program (LARP) has been developing $Nb_3Sn$ quadrupoles of progressively increasing performance for the high luminosity upgrade of the Large Hadron Collider. The 120 mm aperture High-field Quadrupole (HQ) models are the last step in the R&D; phase supporting the development of the new IR Quadrupoles (MQXF). Three series of HQ coils were fabricated and assembled in a shell-based support structure, progressively optimizing the design and fabrication process. The final set of coils consistently applied the optimized design solutions, and was assembled in the HQ03a model. This paper reports a summary of the HQ03a test results, including training, mechanical performance, field quality and quench studies. The U.S. LHC Accelerator Research Program (LARP) has been developing Nb_3Sn quadrupoles of increasing performance for the high-luminosity upgrade of the large hadron collider. The 120-mm aperture high-field quadrupole (HQ) models are the last step in the R&D; phase supporting the development of the new IR Quadrupoles (MQXF). Three series of HQ coils were fabricated and assembled in a shell-based support structure, progressively optimizing the design and fabrication process. The final set of coils consistently applied the optimized design solutions and was assembled in the HQ03a model. This paper reports a summary of the HQ03a test results, including training, mechanical performance, field quality, and quench studies.

In high field magnet applications, Nb$_{3}$Sn coils undergo a heat treatment step after winding. During this stage, coils radially expand and longitudinally contract due to the Nb$_{3}$Sn phase change. In order to prevent residual strain from altering superconducting performances, the tooling must provide the adequate space for these dimensional changes. The aim of this paper is to understand the behavior of cable dimensions during heat treatment and to provide estimates of the space to be accommodated in the tooling for coil expansion and contraction. This paper summarizes measurements of dimensional changes on strands, single Rutherford cables, cable stacks, and coils performed between 2013 and 2015. These samples and coils have been performed within a collaboration between CERN and the U.S. LHC Accelerator Research Program to develop Nb$_{3}$Sn quadrupole magnets for the HiLumi LHC. The results are also compared with other high field magnet projects. In high field magnet applications, Nb_3Sn coils undergo a heat treatment step after winding. During this stage, coils radially expand and longitudinally contract due to the Nb_3Sn phase change. In order to prevent residual strain from altering superconducting performances, the tooling must provide the adequate space for these dimensional changes. The aim of this paper is to understand the behavior of cable dimensions during heat treatment and to provide estimates of the space to be accommodated in the tooling for coil expansion and contraction. This paper summarizes measurements of dimensional changes on strands, single Rutherford cables, cable stacks, and coils performed between 2013 and 2015. These samples and coils have been performed within a collaboration between CERN and the U.S. LHC Accelerator Research Program to develop Nb_3Sn quadrupole magnets for the HiLumi LHC. The results are also compared with other high field magnet projects.

The Great East Japan earthquake that occurred on March 11, 2011 resulted in devastating damages to J-PARC. Although damages to the superconducting magnet system for the J-PARC neutrino beam line appeared to be relatively small, a long recovery procedure was required to resume the operation. Except for this long shutdown period, the system has been operated stably ensuring good accumulation of the physics data. The paper reports on the operation status including the damages by the earthquake and its recovery process. Repair of the insufficient cooling of steering corrector coils, which was present prior to the earthquake, was also performed during the recovery process. The paper also reports on the repair.

This paper presents the goal and status of the high field High Temperature Superconductor (HTS) solenoid program funded through a series of SBIRs. The target of this R&D program is to build HTS coils that are capable of producing fields greater than 20 T when tested alone and approaching 40 T when tested in a background field magnet. The solenoid will be made with second generation (2G) high engineering current density HTS tape. To date, 17 HTS pancake coils have been built and tested in the temperature range from 20 K to 80 K. Quench protection, high stresses and minimization of degradation of conductor are some of the major challenges associated with this program.

Quadrupoles in the fragment separator region of the Facility for Rare Isotope Beams (FRIB) will be subjected to very large heat loads (over 200 Watts) and an intense level of radiation (~10 MGy per year) into the coils of just the first magnet. Magnets made with High Temperature Superconductors (HTS) are advantageous over conventional superconducting magnets since they can remove these heat loads more efficiently at higher temperatures. The proposed design is based on second generation (2G) HTS which allows operation at ~50 K. 2G has been found to be highly radiation tolerant. The latest test results are summarized. The goal of this R&D program is to evaluate the viability of HTS in a real machine with magnets in a challenging environment where HTS offers a unique solution.

Nb3Sn strands extracted from a 20-strand rectangular Rutherford cable were reacted on either stainless steel or Ti-alloy barrels and the critical current, Ic , in the field range of 8-11.5 T was measured on ITER-type barrels made from Ti-6Al-4V alloy, 304 stainless steel and G-10. Measurements on the “standard” Ti-alloy barrel using the test procedure employed at BNL are shown to reproduce Ic for extracted strands to ±2%. The Ic data for the sample mounted on the “standard” Ti-alloy are fit to the deviatoric strain scaling model developed for Nb3Sn by the University of Twente group using an arbitrary pre-strain. Using the parameters for this fit, the Ic data for the other barrels are fitted by only adjusting the strain. Using this procedure, the strain difference due to the barrel material is determined. Assuming a thermal pre-strain of -0.2% for the sample measured on the Ti-alloy barrel, the use of stainless steel barrel increases the compressive strain by -0.07%, that of G-10 by -0.10%. With the wire soldered to the stainless steel barrel, the strain increases to -0.15%. Details of this study are presented.

In support of the luminosity upgrade of the Large Hadron Collider (LHC), the US LHC Accelerator Research Program (LARP) has been developing a 1-meter long, 120 mm bore Nb3Sn IR quadrupole magnet (HQ). With a short sample gradient of 219 T/m at 1.9 K and a conductor peak field of 15 T, the magnet will operate under higher forces and stored-energy levels than that of any previous LARP magnet models. In addition, HQ has been designed to incorporate accelerator quality features such as precise coil alignment and adequate cooling. The first 6 coils (out of the 8 fabricated so far) have been assembled and used in two separate tests-HQ01a and HQ01b. This paper presents design parameters, summary of the assemblies, the mechanical behavior as well as the performance of HQ01a and HQ01b.

Previous studies on V3Ga assert its suitability for use in proposed fusion reactors. V3Ga may outperform Nb3Sn in a fusion reactor environment based on its relatively flat critical-current profile in the 15 T-20 T range, resilience to applied strain, and reduced risk of induced radioactivity. A multifilament powder-in-tube V3Ga conductor was designed, fabricated and tested with a focus on evaluating critical current versus applied field and applied strain performance, wire drawing difficulties, heat-treatment optimization, and overall feasibility of the concept.

We report the effect of titanium on the transport properties of multifilament PIT strand. In addition, the effect of second phase yttrium additions on the microstructure and the bulk pinning force are reported for PIT Nb3Sn mono-core wires. High resolution SEM, EDS, magnetization, and transport measurements were utilized to evaluate the superconducting properties.

A tubular technique for economical production of Nb3Sn material with large numbers of subelements is being explored by Supergenics I LLC and Hyper Tech Research Inc. The number of subelements was increased to 919 (744 subelements plus 175 Cu filaments) by increasing the size at which restacking is carried out. The product exhibited no fabrication problems and was drawn down and tested at a wire diameter of 0.42 mm, where the subelements are 10 μm in diameter. Recently we increased the subelement number to 1387 (1248 subelements plus 139 Cu filaments), which gives a subelement size of 12 μm in 0.7 mm diameter wires. Heat treatment (HT) of different subelement restacks has been investigated, and the best results of critical current and stability are presented. The strain tolerance of the strands with 192 and 744 subelements was also tested, and the strand with fine subelement size showed a high intrinsic irreversible strain limit.

High-Jc Nb3Sn strands often exhibit instabilities in 4.2 K liquid helium at low fields ~ 0.5 to 3 T which are associated with magnetization flux-jumps. However at 1.9 K in superfluid helium, a minimum in premature quench currents at intermediate fields of 5 to 7 T has been observed in voltage-current measurements. These measurements are typically used for critical current determinations, and the premature quenching is driven by current redistribution within the strand as the current is increased and is termed “self-field” instability. In this paper, the magnetization and self-field stability of Nb3Sn strands with Jc ~ 2000 A/mm2 at 12 T are described for a series of wires made using the Sn-tube approach with filament diameters ranging from 13 to 65 μm. The copper stabilizer of these wires after reaction has residual resistivity ratio, RRR, of ~5, which in effect means that any dynamic stabilization from thermal conduction effects is negligible. In this regime of RRR, we find that the magnetization stability with transport current increases with decreasing filament diameter as predicted by simple adiabatic theory. We also observed that at 4.2 K the self-field stability improved with decreasing filament size, but became worse with decreasing temperature as seen in measurements at 2.0 K.

Research and development of Nb3Al strands and cables for a high field accelerator magnet is ongoing under the framework of the CERN-KEK collaboration. In this program, new Ta-matrix Nb3Al strands were developed and their mechanical properties and superconducting properties were studied. The non-Cu Jc values of these strands were 750 ~ 800 A/mm2 at 15 T and 4.2 K. Using these strands, test fabrication of 27-strand Rutherford cable was carried out in collaboration with NIMS and Fermilab. The properties of the strands extracted from the cable were examined and it was found that there was no degradation of the superconducting properties of the strands. In this paper, we report the fabrication of the strands and the cable in brief and present some of the results obtained by studying their properties.

Pancake coils are being fabricated using second generation (2G) High Temperature Superconductor (HTS) for a prototype 10 T solenoid. The length of conductor in each coil is 100 m and the inner diameter of the coil is 101 mm. The critical current of each coil was measured at 77 K in liquid nitrogen and down to ~20 K in helium gas. It has been observed that the effect of thermal shock during cool-down may cause coil performance to degrade irreversibly. The detailed results and the improvements to achieve 10 T will be discussed.

In December 2009 during its first cold test, LQS01, the first Long Nb$_3$Sn Quadrupole made by LARP (LHC Accelerator Research Program, a collaboration of BNL, FNAL, LBNL and SLAC), reached its target field gradient of 200 T/m. This target was set in 2005 by the US Department of Energy, CERN and LARP, as a significant milestone toward the development of Nb$_3$Sn quadrupoles for possible use in LHC luminosity upgrades. LQS01 is a 90 mm aperture, 3.7 m long quadrupole using Nb$_3$Sn coils. The coil layout is equal to the layout used in the LARP Technological Quadrupoles (TQC and TQS models). Pre-stress and support are provided by a segmented aluminum shell pre-loaded using bladders and keys, similarly to the TQS models. After the first test the magnet was disassembled, reassembled with an optimized pre-stress, and reached 222 T/m at 4.5 K. In this paper we present the results of both tests and the next steps of the Long Quadrupole R&D;.

A copper coil dipole magnet from the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL) has been retrofitted by HTS-110 Ltd with coils made from Bi-2223 wire and a self-contained cryogenic cooling system, while keeping the magnet's original iron yoke. This modified bending dipole, which is the first such known retrofit HTS-based accelerator magnet, provides the benefits of a compact coil design to accommodate space-limited experimental issues and a significant reduction in power costs as compared to the original copper magnet. In order to validate this modified design for use in the synchrotron, a detailed magnetic field map has been measured using a multiple-Hall probe assembly and transporter system. The results are discussed in this paper, along with the performance of the closed circuit cryogenics system in keeping the coils below 45 K.

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.

Future upgrades to machines like the Large Hadron Collider (LHC) at CERN will push accelerator magnets beyond 10 T forcing the replacement of NbTi superconductors with advanced superconductors such as Nb3Sn. In support of the LHC Phase-II upgrade, the US LHC Accelerator Research Program (LARP) is developing a large bore (120 mm) Nb3Sn Interaction Region (IR) quadrupole (HQ) capable of reaching 15 T at its conductor limit and gradients of 199 T/m at 4.4 K and 219 T/m at 1.9 K. The 1 m long, two-layer magnet, addresses coil alignment and accelerator quality features while exploring the magnet performance limits in terms of gradient, stress and structure. This paper summarizes and reports on the design, mechanical structure, coil windings, reaction and impregnation processes.

The tubular technique for economical production of Nb3Sn material with large numbers of subelements is being explored further by Supergenics I LLC and Hyper Tech Research Inc. The number of subelements has been raised to 271 (246 + 25) by increasing the size at which the restacking is carried out. The product exhibited no fabrication problems and was drawn down and tested at a wire diameter of 0.42 mm, where the subelements are 18 mum in diameter. Heat treatment of a 271 subelement restack has been varied and a pre heat treatment of 48 h at 575degC followed by long times at 635degC has been shown to be advantageous. Restacks with 217 subelements have been subjected to both compositional and heat treatment changes and the best results, closely approaching those found on PIT materials, have been found on samples given 500 h at 625degC.

In support of the Large Hadron Collider luminosity upgrade, a large bore (120 mm) Nb3Sn quadrupole with 15 T peak coil field is being developed within the framework of the US LHC Accelerator Research Program (LARP). The 2-layer design with a 15 mm wide cable is aimed at pre-stress control, alignment and field quality while exploring the magnet performance limits in terms of gradient, forces and stresses. In addition, HQ will determine the magnetic, mechanical, and thermal margins of Nb3Sn technology with respect to the requirements of the luminosity upgrade at the LHC.

We report on a multi-institute comparison of critical current data measured on a modern NbTi wire for the Large Hadron Collider (LHC), which has shown a standard deviation below 1% in critical current density spread in more than 1500 measurements. Interlaboratory comparisons on Nb3Sn wires have shown ambiguities that could be attributable to strain related differences in critical current density, originating from differences in sample handling, reaction, and mounting techniques, or also to differences in the magnetic field and current calibrations between the institutes. A round robin test of a well characterized NbTi wire provides a baseline variance in critical current results that is presumed to be attributable only to differences in the characterization systems. Systematic differences on the order of 3.5% are found in the comparison. The most likely cause for the observed differences is a small diameter holder that brings the wire into a strain regime in which strain effects can no longer be ignored. A NbTi round robin test, when performed properly, will separate system differences from sample specific differences and provide laboratories with an opportunity to calibrate equipment against a standard measurement.

Reaction heat treatments spanning 605 to 750degC and 24 to ~400 hours were applied to several sets of RRP strands. Magnetization and transport measurements were used to track the changes of superconducting properties and the amounts of Nb3Sn formed. The experiments showed that temperature increases of 15degC produced equivalent properties in half the time within the temperature range 620-680degC. This result was the same whether Ta or Ti was used to alloy the Nb3Sn. The bulk pinning force Fp for Ta-alloyed wires displayed a significant drop for temperatures outside the range above, due to tin gradients at low temperatures and grain growth at high temperatures. The Fp drop at high reaction temperatures prevents wire technology from taking advantage of the significantly higher Kramer-plot intercept H K for high-temperature reactions. On the other hand, Ti alloying provides a quick and potent means to increase H K at reaction temperatures for which Fp remains high.

As part of the LHC Accelerator Research Program (LARP) to build a high performance quadrupole magnet with Nb3Sn conductor, a pair of 3.6 m-long Nb3Sn racetrack coils has been made at Brookhaven National Laboratory (BNL) and installed in two shell-type support structures built by Lawrence Berkeley National Laboratory (LBL). These magnet assemblies have been tested at 4.5 K at BNL to gauge the effect of extended length and prestress on the mechanical performance of the long structure compared to earlier short models. This paper presents the results of quench testing and compares the overall performance of the two versions of the support structure. We also summarize the shell strain measurements and discuss the variation of quench current with ramp rate.

Amongst the magnet development program of a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider luminosity upgrade, six quadrupole magnets were built and tested using a shell based key and bladder technology (TQS). The 1 m long 90 mm aperture magnets are part of the US LHC Accelerator Research Program (LARP) aimed at demonstrating Nb3Sn technology by the year 2009, of a 3.6 m long magnet capable of achieving 200 T/m. In support of the LARP program the TQS magnets were tested at three different laboratories, LBNL, FNAL and CERN and while at CERN a technology-transfer and a four days magnet disassembly and reassembly were included. This paper summarizes the fabrication, assembly, cool-down and test results of the six magnets and compares measurements with design expectations.

In support of the development of a large-aperture Nb$_3$Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, several two-layer technological quadrupole models of TQC series with 90 mm aperture and collar-based mechanical structure have been developed at Fermilab in collaboration with LBNL. This paper summarizes the results of fabrication and test of TQC02a, the second TQC model based on RRP Nb3Sn strand, and TQC02b, built with both MJR and RRP strand. The test results presented include magnet strain and quench performance during training, as well as quench studies of current ramp rate and temperature dependence from 1.9 K to 4.5 K.

Brookhaven National Laboratory (BNL) has built a prototype superconducting dipole for the Facility for Antiproton and Ion Research (FAIR) at GSI that can be ramped at a high rate (1-4 T/s). To characterize the field quality at such high ramp rates, a measurement system consisting of 16 printed circuit windings was developed. In this system, the signals induced in all the windings as the magnet is ramped are analyzed to obtain the field harmonics. Initial measurements with this system suffered from somewhat poor resolution of the ADCs used for data acquisition. Also, only a few low order harmonics could be obtained with the 16 signals. These drawbacks have been addressed by replacing the ADCs with HP3458A voltmeters and by combining data taken with two different orientations of the probe. This has allowed us to measure very precisely (10 ppm of the dipole field) all the harmonics up to the 26-pole at ramp rates up to 4.3 T/s. The data analysis and results with this improved system are presented.

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 were made in order to check the fabrication steps for long Nb3Sn 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 Nb3Sn 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.

Test results are reported on four quadrupole magnet model tests (TQS01a, TQS01b, TQS01c, TQS02) in support of the development of a large-aperture 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) conductor, and addressed TQS01's quench-training pattern, by utilizing titanium alloy (TiAl6V4) 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.

A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4 m-long quadrupole magnets (LQ) wound with Nb3Sn conductor. The goal of these magnets is to be a proof of principle that Nb3Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.

The first quadrupole in the fragment separator region of the proposed Facility for rare isotope beams would be subjected to extremely high radiation and heat loads (~15 kW in the magnet and 5 kW/m in the coil). As a critical part of this proposal, a radiation resistant quadrupole made with first generation high temperature superconductor (HTS) has been built and tested. This paper summarizes design, construction and test results of this magnet that has been designed to operate at ~30 K to remove this heat economically. Of particular interest are the simulated energy deposition experiments that demonstrate the stable operation of this HTS magnet in the presence of these unprecedented loads. The next quadrupole will use second generation HTS and is expected to operate at 50 K or above for even more efficient energy removal.

Restack Rod Process (RRP) strands with 54 and 108 sub-elements were rolled from 0.7 mm diameter to 0.45 mm thickness to simulate the deformation of strands at the edges of Rutherford cables. Various diagnoses were then applied to assess performance and stability. Transport measurements were used to assess the effect of rolling on the critical current. Magnetization measurements were used to probe superconducting pathway bridging between deformed sub-elements. The copper residual resistivity ratio was also measured to assess tin contamination due to thinned or ruptured diffusion barriers. While systematic changes were observed in all three measurements with increasing deformation, showed the strongest changes. The implications of these measurements for cable stability, and their relationship to observations of the strand cross section by light microscopy, are discussed.

The NbSn strand chosen for the next step in the magnet R&D of the U.S. LHC Accelerator Research Program is the 54/61 sub-element Restacked Rod Process by Oxford Instruments, Superconducting Technology. To ensure that the 0.7 mm RRP strands to be used in the upcoming LARP magnets are suitable, extensive studies were performed. Measurements included the critical current, Ic, using the voltage-current (V-I)method, the stability current, IS, as the minimal quench current obtained with the voltage-field (V-H) method, and RRR. Magnetization was measured at low and high fields to determine the effective filament size and to detect flux jumps. Effects of heat treatment temperature and durations on Ic and IS were also studied. Using strand billet qualification and tests of strands extracted from cables, the short sample limits of magnet performance were obtained. The details and the results of this investigation are herein described.

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.