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At least 55 records · Page 3

Fusion Development and Technology (Final Technical Report for FC02-93ER54186)

The project is divided into three major tasks: 1) Magnet R&D i) Magnets Task 1 - Development of HTS Twisted Stacked-Tape Cable (TSTC) conductors for high field, high current magnets ii) Magnets Task 2– Development of Cryogenic Magnet Cooling Technology iii) Magnets Task 3 - National and International Collaboration 2) Electron Cyclotron Heating (ECH) of plasmas 3) FNSF Liquid Metals Study.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

SMART conductor on round core (CORC ® ) wire via integrated optical fibers

Superconducting cables based on high temperature superconductors (HTS) are necessary for applications requiring large currents and low inductance, such as compact fusion reactors. In this paper, we report the proof-of-concept of a SMART Conductor on Round Core (CORC ® ) wire realized via integration of optical fibers into the copper core. A SMART CORC ® wire with integrated optical fibers was manufactured and its capabilities have been experimentally demonstrated. Results show that by interrogating the optical fibers via Rayleigh backscattering, a Spectral Shift signal as a function of time and position along the cable can be used to detect and locate hot-spots that are developed within the wire or its terminations. It has been found that highly localized current injection into the terminations could initiate hot-spots within the cable at locations where current redistribution between tapes occur. This effect is virtually eliminated when adequate current connections are used that inject current evenly along the cable terminations. Normal zone propagation velocities have been calculated as a function of time using Spectral Shift data for a heater-induced quench as well as a quench induced by overcurrent. In both cases the normal zone propagation velocity was about 6 cm s -1 , but in the heater-induced experiment it was preceded by 500 ms of slower propagation at 2.5 cm s -1 .

Physics↗

A Low Loss, Fast Ramp HTS Solenoid Prototype for Compact Spherical Tokamaks

To explore AC loss characteristics of commercial Bi-2212 conductors made in the USA, a small ohmic heating (OH) prototype coil is being developed for compact tokamaks using high performance Bi-2212 wires newly manufactured by Bruker EST. Here, the goal is to build and test Bi-2212 prototype coils for fast ramp central solenoid (CS) operation of spherical tokamaks (ST). For a ST pilot plant, one of the key challenges is the tight space available for CS in a center column where in-board legs of the toroidal field (TF) and OH coils are assembled into a cryostat with a few millimeters clearance. A high current density Rutherford cable consisting of 17 legacy Bi-2212 wires, a contribution of the US Magnet Development Program (MDP), was fabricated at the Lawrence Berkeley National Laboratory (LBNL) for the development of fast ramp CS magnets in the ST Advanced Reactor (STAR) designed by PPPL. Characterization of the new and legacy HTS wires is presented, along with the coil design wound directly with new wire, and a Rutherford cable-wound solenoid using the legacy wire. A comparison of AC losses is made based on expected performance for a fast ramp ST operation. The HTS cable and cabled coil fabrication issues such as the heat treatment, coil mandrel design, assembly and 2212 quench characteristics are discussed, along with a test plan for CS design validation.

Zhai, Yuhu [Princeton Plasma Physics Laboratory (P↗

Development and performance of high-temperature superconducting CORC ® cables with CFD REBCO tapes

Abstract Increasing the normal zone propagation velocity (NZPV) in superconducting cables based on rare earth barium copper oxide (REBCO) tapes is expected to cause a paradigm shift by enabling the development of faster and more reliable quench detection systems to mitigate the development of destructive hot spots. Furthermore, a higher NZPV is beneficial in terms of fault current limitation capabilities by accelerating the homogenization of the quench in superconducting power devices. One way envisioned to increase the NZPV of cables based on REBCO tapes is the current flow diverter (CFD) concept. A Conductor on Round Core (CORC ® ) cable made with CFD REBCO tapes, called CFD CORC ® cable, and a CORC ® cable made with regular REBCO tapes, were fabricated and tested. The critical current of the CFD and regular CORC ® cables were obtained at temperatures ranging from 67 to 77 K in self-field. Measurements showed that the NZPV was increased by a factor of 4–4.5 in the case of the CFD CORC ® cable. Furthermore, the results suggest that the NZPV depends only on the applied current, similar to what has been observed previously on single REBCO tapes. These results demonstrate the successful integration of CFD REBCO tapes in CORC ® cables, without compromising their superconducting properties or their enhanced NZPV. The possibility of enhancing the NZPV of REBCO-based cables could facilitate quench detection, which remains an important issue in HTS magnet applications. This advancement also holds promise for the fault current limitation functionality of CORC ® cables.

Ben Saâd, Haïfa (ORCID:0000000216205364)↗

Conceptual design of HTS magnets for fusion nuclear science facility

Second-generation high temperature superconductors (HTS) are available for producing >20 T at the magnet bore compared to 13–16 T for lower temperature superconducting (LTS) toroidal field magnets proposed in recent fusion energy systems studies (FESS) of Fusion Nuclear Science Facility (FNSF). HTS may enable higher fusion power density and smaller device size. High current density cables of multi-layered REBCO tapes have achieved >10 kA at 4–20 K operation in short sample tests for fusion. High current density cables are required for engineering design of FNSF to allow space for interior plasma components. High current density HTS magnets are particularly attractive in reducing the size of a fusion device, beneficial for compact tokamaks, due to their space constraints. Successful HTS magnet development may enable the design of smaller and cheaper fusion pilot plants with a mission of demonstrating net electricity. It may also offer significant cost and performance advantages in non-fusion applicants such as nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). Furthermore, we developed HTS magnet design concepts for a compact FNSF radial build in order to define the coil size, winding pack mechanical loading and engineering requirements. Partnering with vendors in the US, PPPL is also testing high current cable prototypes aiming at enabling low cost cable technology toward 100 A/mm 2 engineering current density over the winding pack desired in high field model coil development for compact fusion pilot plants.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Modeling of Bi-2212 strand and Rutherford cable in a dipole coil insert

The U.S. Magnet Development Program (US-MDP) explores high-field accelerator magnets compatible with op- erational conditions beyond the limits of Nb3Sn technology. The ongoing R&D High-Temperature Superconductors (HTS) suggests using Bi2Sr2CaCu2O8−x (Bi-2212) as superconducting element. Bi-2212 Rutherford cables maintain a high critical current (IC ) when exposed to a large external magnetic field. However, Bi-2122 exhibits an oversensitive stress-strain response when subject to large Lorentz forces. This paper reports on the magnetic and mechanical analysis of the Bi-2212 cosine-theta insert being developed at Fermilab for a hybrid magnet composed of 2 external layers of Nb3Sn and 2 internal layers of Bi-2212. We performed a FEM analysis of the insert to estimate the HTS stress state in the coil s strands under magnetic and mechanical loads.

D'Agliano, A.↗

Conceptual Design of A 20 T Dipole Based on Hybrid REBCO/Nb 3 Sn Cos-theta Coil

This paper presents a design concept of an HTS/LTS hybrid dipole with 50 mm aperture and 20 T nominal field based on a cos-theta coil and a cold iron yoke. The HTS part of magnet coil uses REBCO Twisted Stacked Tape cable. The LTS part is graded and made of two Nb3Sn Rutherford cables. Due to high sensitivity of HTS/LTS coils to large stresses and strains at high fields, a Stress Management (SM) concept combined with the cos-theta coil geometry is used. The results of magnet magnetic analysis are presented and discussed.

43 PARTICLE ACCELERATORS↗

Magnetic and Mechanical Analysis of Bi-2212 Rutherford Cable in a Cos-Theta Sub-Scale Dipole Coil

The U.S. Magnet Development Program (US-MDP) explores high-field accelerator magnets compatible with operational conditions beyond the limits of Nb$_3$Sn technology. The ongoing R&D High-Temperature Superconductors (HTS) suggests using Bi$_2$Sr$_2$CaCu$_2$O$_{8-x}$ (Bi-2212) as superconducting element. Bi-2212 Rutherford cables maintain a high critical current (I$_C$) when exposed to a large external magnetic field. However, Bi-2212 exhibits an oversensitive stress-strain response when subject to large Lorentz forces. This paper reports on the magnetic and mechanical analysis of the Bi-2212 cosine-theta insert being developed at Fermilab for a hybrid magnet composed of two external layers of Nb$_3$Sn and two internal layers of Bi-2212. We performed a FEM analysis of the insert to estimate the HTS stress state in the coil's strands under magnetic and mechanical loads.

43 PARTICLE ACCELERATORS↗

The application of high temperature superconductors to space electrical power distribution components

Some important space based electrical power distribution systems and components are examined to determine what might be achieved with the introduction of high temperature superconductors (HTS). Components that are compared in a before and after fashion include transformers, transmission lines, and capacitors. It is concluded that HTS has its greatest effect on the weight associated with transmission lines, where the weight penalty could be reduced by as much as 130 kg/kW/km of cable. Transformers, because 28 percent of their mass is in the conductor, are reduced in weight by the same factor. Capacitors are helped the least with only negligible savings possible. Finally, because HTS can relax the requirement to use alternating current in order to reduce conductor mass, it will be possible to generate significant savings by eliminating most transformers and capacitors.

Aron, Paul R.↗

The application of high temperature superconductors to space electrical power distribution components

Some important space based electrical power distribution systems and components are examined to determine what might be achieved with the introduction of high temperature superconductors (HTS). Components that are compared in a before-and-after fashion include transformers, transmission lines, and capacitors. It is concluded that HTS has its greatest effect on the weight associated with transmission lines, where the weight penalty could be reduced by as much as 130 kg/kW/km of cable. Transformers, because 28 percent of their mass is in the conductor, are reduced in weight by the same factor. Capacitors are helped the least with only negligible savings possible. Finally, because HTS can relax the requirement to use alternating current in order to reduce conductor mass, it will be possible to generate significant savings by eliminating most transformers and capacitors.

Aron, Paul R.↗

Cost-effective Conductor, Cable, and Coils for High Field Rotating Electric Machines

The purpose of the DOE-AMMTO-funded project was to significantly reduce industrial energy intensity through manufacturing innovations. The project focused on superconducting technology for industrial motors to dramatically increase efficiency. The bottleneck in deploying high temperature superconducting (HTS) motors was high cost and low yield of the conductor manufacturing process. The process yield is low because of the defects in the conductor, forcing the manufacturers to cut off defective sections after characterizing each millimeter. Additionally, the piece lengths tend to be low because of the defects. The project tackled the low-yield manufacturing process challenge by devising an innovative method to use defective conductors in bundled cables without losing performance by engineering current sharing among the conductors. The innovation not only lowers the cost of the conductor but also enhances the reliability of HTS motors and other devices to mitigate the defects that might form during the fabrication and operation of the device. With the increasing interest in REBa2Cu3O7-x (REBCO)-coated conductors for various power, energy, and magnet applications, ensuring the reliability of HTS devices is of significant interest. The EERE funding allowed us to make significant progress in understanding the defects in manufactured conductors and the implications of the defects in superconducting electric motors and other superconducting power and energy applications.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Elliptic Aperture CCT Coils for HTS Dipole Magnets

High-temperature REBa$_{2}$Cu$_{3}$O$_{7-x}$ (REBCO) superconductors are a route to increase the field of accelerator magnets beyond the 15-16T practical limit of Nb$_{3}$Sn. REBCO cabled in a CORC geometry is a promising fit for this application, enabling the design of low inductance magnets with conductor transposition. However, the use of CORC in coils with the tight conductor bending radii typical of accelerator magnets remains a key challenge, with on-going research both on the conductor development and coil design fronts seeking to address this issue. Here, in this work we explore the tradeoffs between circular and elliptic aperture canted-cosine-theta (CCT) coils when the conductor minimum bending radius is a key consideration, concluding that aperture ellipticity is an important free parameter in the optimization of magnetically efficient CORC dipole magnets. In particular, we show that elliptic bore designs enable a regime of smaller aperture HTS coils, an important result for LTS-HTS hybrid magnets and more generally for accelerator applications benefiting from non-circular magnet apertures. To this end we present an elliptic aperture dipole design optimized for hybrid testing within the US Magnet Development Program (US-MDP) and share 77 K test results of a prototype coil which provides first experimental confirmation of the advantages.

Brouwer, L. [Lawrence Berkeley National Laboratory↗

An Acoustic Quench Detection Method for CICC Conductor Operating in Gas or Liquid

A method using micro-electro-mechanical system (MEMS) acoustic sensor technology to detect a quench and abnormal behavior of a superconductor is discussed. MEMS of microphone chips are installed along the coolant space of a superconducting conductor to monitor the coolant condition. By arranging the acoustic sensor array in a coolant flow channel, it is possible to quickly detect a change in the local condition of the coolant with precise spatial resolution. This method is useful for monitoring superconducting magnets and power cables, especially those made with a cable-in-conduit-conductor (CICC) configuration. The methodology described in this work will also be very useful for a high temperature superconducting (HTS) conductor, such as REBCO tape conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Comparison of Multi-Scale Nonlinear and Conventional Linear Methods for Stress Analysis of Nb 3 Sn Superconducting Magnets

Here this is an extension of the work on a multi-scale nonlinear procedure that demonstrated how to conduct nonlinear stress analysis of Nb 3 Sn superconducting accelerator magnets. The nonlinear procedure uses measured stress-strain curves of annealed copper, Nb 3 Sn strands and coil samples as inputs, which reduces the number of assumptions made for material properties—key uncertainties of any engineering analysis. The results from nonlinear analysis, semi-nonlinear analysis, and linear analysis of the same QFFB2 Nb 3 Sn quadrupole magnet under the same temperature and loads, were compared and discussed. The comparison illustrates that nonlinear stress analysis is significantly more accurate than other methods. As the superconducting coil block is a complex, composite material, it would be inadequate to assume the whole coil block to be linear, either isotropic or orthotropic. It is imperative to conduct nonlinear analysis by simulating the superconducting coil to the level of detail of the individual cables and individual strands. The nonlinear stress analysis procedure can be used to simulate not only Nb 3 Sn magnets, but also NbTi and HTS magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Record High Ramping Rates in HTS Based Superconducting Accelerator Magnet

Here we report results of experimental test of the High Temperature Superconductor (HTS) based fast-cycling prototype accelerator magnet capable to operate up to about 300 T/s field ramping rate with some 0.5 T B-field in the magnet gap. The measured upper limit for the cryogenic cooling power required to support magnet conductor operation at high ramping rates indicates great potential for such type of magnets in rapid cycling synchrotrons for neutrino research or acceleration of very short-lived muons. The test magnet design, construction and supporting cryogenic and power systems are briefly described. The magnet's power test results are discussed in terms of a possible upgrade of this magnet design to 2 T B-field, a maximum feasible with super-ferric magnet.

43 PARTICLE ACCELERATORS↗

Development of a high current density, high temperature superconducting cable for pulsed magnets

Abstract A low AC loss Rare Earth Barium Copper Oxide (REBCO) cable, based on the VIPER cable technology has been developed by Commonwealth Fusion Systems for use in high field, REBCO based tokamaks. The new cable is composed of partitioned and transposed copper ‘petals’ shaped to fit together in a circular pattern with each petal containing a REBCO tape stack and insulated from each other to reduce AC losses. A stainless steel jacket adds mechanical robustness—also serving as a vessel for solder impregnation—while a tube runs through the middle for cooling purposes. Additionally, fiber optic sensors are placed under the tape stacks for quench detection. To qualify this design, a series of experiments were conducted as part of the SPARC tokamak Central Solenoid Model Coil program—to retire the risks associated with full scale, fast ramping, high flux HTS Central Solenoid (CS) and Poloidal Field (PF) coils for tokamak fusion power plants and net energy demonstrators. These risk study and risk reduction experiments include (1) AC loss measurement and model validation in the range of ~5 T/s, (2) an IxB electromagnetic loading of over 850 kN/m at the cable level and up to 300 kN/m at the stack level, (3) a transverse compression resilience of over 350 MPa, (4) manufacturability at tokamak relevant speeds and scales, (5) cable to cable joint performance, (6) fiber optic based quench detection speed, accuracy, and feasibility, and (7) overall winding pack integration and magnet assembly. The result is a cable technology, now referred to as PIT VIPER, with AC losses that measure fifteen times lower (at ~5 T/s) than its predecessor technology; a 2% or lower degradation of critical current (Ic) at high IxB electromagnetic loads; no detectable Ic degradation up to 570 MPa of transverse compression on the cable unit cell; end to end magnet manufacturing, consistently producing Ic values within 7% of the model prediction; cable to cable joint resistances at 20 K on the order of ~15 nΩ; and fast, functional quench detection capabilities that do not involve voltage taps. This cable technology will be tested comprehensively in a Central Solenoid Model Coil to prove its readiness for compact, high field tokamak operation.

Sanabria, Charlie (ORCID:0000000150175309)↗

Conductor on molded barrel magnet assembly and associated systems and methods

A Conductor on Molded Barrel (COMB) magnet assembly optimized for High Temperature Superconducting (HTS) materials. The magnet assembly comprises a magnetic coil(s) carried by a conductor support structure and configured in cosine-theta geometry. Created using additive manufacturing, the conductor support structure features a continuous cable channel that fittedly carries and positions elongated straight portion(s) of the magnetic coil(s) parallel to a magnetic axis. The conductor support structure may be cylindrically shaped and longitudinally bored, with the continuous cable channel comprising an outer channel portion (distal on the cylinder) and an inner channel portion (proximal on the cylinder). A transition hole that joins the outer channel portion and the inner channel portion allows a single magnetic coil to be wound along both the outer and inner surfaces of the conductor support structure. The conductor support structure may be fabricated as longitudinally-symmetrical halves, and secured for operation using azimuthal and/or midplane shims.

Kashikhin, Vadim V.↗

What is needed for BISCO to work in a dipole insert for 20 tesla hybrid accelerator magnets

Developing HTS dipole inserts producing fields larger than 5 T within 15 T Nb3Sn outserts is necessary to generate 20 T or higher fields for future high energy colliders. Dipole inserts based on the cos-theta coil geometry with various stress management concepts and Bi2212 super-conducting strand and cable are being developed at Fermilab both within and beyond the U.S. national effort. On paper, the potential reach for the maximum magnetic field in existing or planned Nb3Sn outserts is close to 20 T, thanks to the progress realized in Bi2212 wires’ critical current density. To achieve the Bi2212 potential in accelerator magnets, however, a number of technological challenges still have to be faced. These for instance include the need to design billets that are adequate for Rutherford cabling; developing insulation processes and materials that prevent leaks, which reduce transport current and increase the risk of shorts; control and limit Bi2212 coils’ stresses and strains; reconsider the Split Melt Process (SMP) to lower costs and simplify the processing. This paper reviews Bi2212 conductor properties and coil technolo-gies, and proposes new ideas to face the challenges that Bi2212 still presents as an accelerator magnet conductor.

43 PARTICLE ACCELERATORS↗