A goal of the U.S. Magnet Development Program (US-MDP) is high-field magnets for accelerators with magnetic fields larger than 15 T, i.e., above the limits of Nb 3 Sn accelerator magnets. Composite ...round wires and Rutherford cables made of high temperature superconductor Bi2212 may achieve this goal. Bi2212 is sensitive to transverse stresses and strains, and this requires stress management in the coil design. A stress management approach was developed at Fermilab for high-field large-aperture Nb 3 Sn accelerator magnets. Now it is being applied to high-field dipole insert coils based on Bi2212 Rutherford cable. This paper describes the insert coil design and main parameters, including the superconducting wire and cable. The coil will be installed inside a 60-mm bore Nb 3 Sn dipole outsert coil and cold iron yoke. The Bi2212 coil will be tested individually and in series with the Nb 3 Sn outsert coil. The expected Bi2212 insert test parameters are reported and discussed.
This paper describes a 120-mm aperture 2-layer dipole coil with stress management (SM) developed at Fermilab based on cos-theta coil geometry. A model of the coil support structure made of plastic ...was printed using additive manufacturing technology and used for practice coil winding. The real coil support structure was printed using the 316 stainless steel. The results of the SM structure size control and the key coil fabrication steps are reported in the paper. The design of coil SM structure and the coil FEA in the dipole mirror test configurations are presented and discussed.
The U.S. Magnet Development Program (US-MDP) is developing high-field accelerator magnets with magnetic fields beyond the limits of Nb 3 Sn technology based on high temperature superconductor Bi 2 Sr ...2 CaCu 2 O 8-x (Bi2212). However, Bi2212 wires and cables are sensitive to transverse stresses and strains, which are substantial in high-field accelerator magnets. To prevent large degradation of the Bi2212 coils and achieve the required field quality, an innovative design which provides turn positioning during coil fabrication and operation and manage azimuthal and radial strains/stresses in the coil has been proposed at FNAL. This paper describes the development of a small-aperture two-layer Bi2212 dipole coil with stress management. The main parameters of the Bi2212 wire and Rutherford cable, the design of coil stress management structure and its plastic model, the coil mechanical analysis in the dipole mirror configuration are presented and discussed.
A novel Nb 3 Sn-based superconducting undulator (SCU) was developed and integrated into the Advanced Photon Source (APS) at Argonne National Laboratory. The SCU achieved user operation within an ...accelerator environment. Compared to its Nb-Ti counterpart, the Nb 3 Sn SCU operates at substantially higher currents. Thus, a detailed experimental evaluation of the SCU magnets' performance was necessary under both "wet" and indirectly cooled conditions to ensure its reliability during operation. Our study indicated that the cooling method has a noticeable influence on the magnet's behavior. Specifically, energy dissipation in the magnets during quenches was observed to be greater under indirect cooling than with "wet" cooling. This investigation provided insights into the safe operational limits. Guided by these insights the more challenging high-current tests were successfully carried out at the end of the user phase. The SCU achieved the design undulator field of 1.17 T at 820 A and 4.2 K, with a magnetic gap of 9.5 mm and a period of 18 mm. Actual performance exceeded the specifications, reaching 850 A.
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 Nb 3 Sn 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.
High-field accelerator magnets made of state-of-the-art Nb 3 Sn Rutherford cables demonstrate relatively long trainings due to sudden heat depositions originated by thermo-mechanical perturbations in ...the magnet coils. Coil sensitivity to these perturbations can be reduced by increasing the specific heat, C p , of major coil components - strands, or whole cable, or epoxy. The R&D on all these three approaches is in progress. This paper studies feasibility of increasing the C p of Rutherford-type cables by using a thin composite Cu/Gd 2 O 3 tape. The tape can be either wrapped around the cable, placed on the cable wide faces under the insulation, and/or inserted as a core. Cu/Gd 2 O 3 ribbons with ∼30% of Gd 2 O 3 powder and two different thicknesses were produced by Hyper Tech Research, Inc. Wire and cable samples outfitted with these high- C p ribbons, or tapes, were prepared and tested at FNAL for the Minimum Quench Energy ( MQE ). At 80% I c , the MQE gain average over the tested magnetic field range of the NbTi cable with high- C p tape on both sides was ∼1.3. The MQE gain average of the NbTi wire wrapped with the high- C p ribbon was 3.1.
MDPCT1 Quench Data and Performance Analysis Stoynev, S.; Baldini, M.; Barzi, E. ...
IEEE transactions on applied superconductivity,
09/2022, Letnik:
32, Številka:
6
Journal Article
Recenzirano
Odprti dostop
MDPCT1is a four-layer cos-theta Nb 3 Sn dipole demonstrator developed and tested at FNAL in the framework of the U.S. Magnet Development Program. The magnet reached record fields for accelerator ...magnets of 14.1 T at 4.5 K in the first test and 14.5 T at 1.9 K in the second test and then showed large degradation. While its inner coils performed exceptionally well with only two quenches up to 14.5 T and no evidence of degradation, the outer coils degraded over the course of testing. By adopting new measurement and analysis techniques at FNAL we are discussing in detail what happened. Both success and failure in our diagnostics are discussed. The evolution of techniques over the course of two tests (and three thermal cycles) shows the path to address challenges brought by the first four-layer magnet tested at FNAL. This paper presents the analysis of quench data along with diagnostic features and complementary measurements taken in support of the magnet performance analysis.
In the present work the electrochemical and thermal syntheses of superconducting Nb3Sn films are investigated. The Nb3Sn phase is obtained by electrodeposition of Sn layers and Cu intermediate layers ...onto Nb substrates followed by high temperature diffusion in inert atmosphere. Electrodeposition was performed from aqueous solutions at current densities in the 20-50 mA cm−2 range and at temperatures between 40 °C and 50 °C. Subsequent thermal treatments were realized to obtain the Nb3Sn superconductive phase. Glow discharge optical emission spectrometry demonstrated that after thermal treatment interdiffusion of Nb and Sn occurred across a thickness of about 13 m. Scanning electron microscopy allowed accurately measuring the thickness of the Nb3Sn phase, whose average for the various types of film samples was between 5.7 and 8.0 m. X-ray diffraction patterns confirmed the presence of a cubic Nb3Sn phase (A15 structure) having (210) preferred orientation. The maximum obtained Tc was 17.68 K and the Bc20 ranged between 22.5 and 23.8 T. With the procedure described in the present paper, coating complex shapes cost-effectively becomes possible, which is typical of electrochemical techniques. Furthermore, this approach can be implemented in classical wire processes such as 'jelly roll' or 'rod in tube', or directly used for producing superconducting surfaces. The potential of this method for superconducting radiofrequency structures is also outlined.
A major problem of state-of-the-art Nb 3 Sn accelerator magnets is their long training due to thermo-mechanical perturbations. Increasing the specific heat, C p , of the Rutherford cable would reduce ...and/or eliminate training by limiting the coils temperature rise. This paper studies feasibility of increasing the C p of Rutherford-type cables by using thin composite Cu/Gd 2 O 3 and Cu/Gd 2 O 2 S tapes produced by Hyper Tech Research, Inc. The tape can be either wrapped around the cable, placed on the cable wide faces under the insulation, and/or inserted as a core. Wire samples outfitted with these high- C p ribbons, or tapes, were prepared and tested at FNAL for their Minimum Quench Energy ( MQE ). At 90% I c and 15 T, the average gain of MQE of the Nb 3 Sn wire soldered to the Cu/Gd 2 O 2 S 55 μm thick ribbon was 2.5, and further increased at larger transport currents.
This work aims at contributing to the development of superconducting Nb3Sn thin films for possible applications, as for instance in superconducting radio frequency (SRF) cavities. The synthesis of ...Nb–Sn coatings was carried out on copper substrates by electrodeposition from 1-butyl-3-methylimidazolium chloride (BMIC) ionic liquids containing SnCl2 and NbCl5. Cyclic voltammetric curves were recorded to identify the reduction potentials of Nb and Sn ionic species. Electrodeposition was performed at 40 and 400mA/cm2 and 130°C. The CV demonstrated that BMIC has a suitable potential window for co-deposition of Nb and Sn. The electrodeposited coatings showed a cubic Nb3Sn phase with (211) preferred orientation, a disordered orthorhombic NbSn2 phase and Sn–Cu phases. Film thickness was from 200 to 750nm. These results suggest that electrodeposition of Nb–Sn coatings on copper substrates could be a suitable route to one day replace the current expensive Nb SRF cavities.
•Reproducible electrochemical process to synthesize Nb3Sn films onto Cu.•BMIC ionic liquids containing Sn and Nb chlorides.•Nb–Sn coatings containing the cubic Nb3Sn phase were obtained.•A maximum coating thickness of 750nm was obtained.
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