Fusion reactor with glowing plasma contained by superconducting coils

Fusion Breakthrough: How New Magnet Designs Could Power the Future

Lena Kashyap in Tech & Innovation August 2025 • 4 min read.

"Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design is optimized for maximum magnetic flux generation and extends plasma burn duration."

The quest for sustainable and clean energy sources has led researchers to explore the potential of nuclear fusion. One of the critical components in a fusion reactor is the Central Solenoid (CS) coil, which generates the intense magnetic fields required to contain and control the plasma. Recent advancements in coil design, particularly the use of high-temperature superconductors (HTS), promise to significantly enhance the performance and efficiency of fusion reactors.

A recent study focuses on maximizing the magnetic flux generated by a CS coil with a fixed outer radius, leveraging HTS conductors in the highest field layers and combining them with Nb3Sn and NbTi in intermediate and low field layers. This hybrid approach optimizes the use of different superconducting materials based on their performance characteristics at varying magnetic field strengths.

The goal is to achieve a design that not only maximizes magnetic flux but also manages the mechanical stresses within the coil, ensuring its structural integrity and longevity. This is achieved through a combination of advanced materials and innovative engineering techniques, paving the way for more efficient and sustainable fusion power.

Understanding the Hybrid HTS-Nb3Sn-NbTi DEMO CS Coil Design

Fusion reactor with glowing plasma contained by superconducting coils

The Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design represents a significant advancement in fusion reactor technology. This design strategically utilizes different superconducting materials—HTS, Nb3Sn, and NbTi—in specific layers of the CS coil to optimize performance and manage costs. This innovative approach aims to maximize the magnetic flux generated by the coil while ensuring its structural integrity and operational efficiency.

In this hybrid design, HTS conductors are used in the highest magnetic field layers, leveraging their superior high-field performance. These materials can maintain superconductivity at higher magnetic fields compared to traditional superconductors, allowing for more compact and powerful coil designs. The intermediate layers employ Nb3Sn, while the lower field layers use NbTi. This combination ensures that each material is used in the range where it performs most effectively, balancing cost and performance.

HTS (High-Temperature Superconductors): Used in the innermost layers where the magnetic field is strongest, offering high critical current densities at high fields.
Nb3Sn (Niobium-Tin): Positioned in the intermediate layers, providing a balance between cost and performance in moderately high magnetic fields.
NbTi (Niobium-Titanium): Located in the outermost layers where the magnetic field is weakest, offering a cost-effective solution for lower field applications.

The use of layer winding, as opposed to other winding techniques, allows for the strategic placement of these materials, optimizing the coil's overall performance. The inner radius of the CS coil is carefully optimized to maximize flux generation while considering the properties of the superconductors, hoop stress, and axial stress. This meticulous design process results in a coil that can generate a substantial magnetic flux, contributing to longer plasma burn times and improved power plant efficiency.

The Future of Fusion Energy

The development of hybrid coil designs represents a significant step forward in the pursuit of fusion energy. By optimizing the use of superconducting materials and carefully managing mechanical stresses, these designs pave the way for more efficient and sustainable fusion reactors. As research and development continue, the promise of clean, abundant fusion energy moves closer to reality, offering a potential solution to the world's growing energy needs.

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This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.fusengdes.2018.10.027, Alternate LINK

Title: Hybrid Hts-Nb3Sn-Nbti Demo Cs Coil Design Optimized For Maximum Magnetic Flux Generation

Subject: Mechanical Engineering

Journal: Fusion Engineering and Design

Publisher: Elsevier BV

Authors: Rainer Wesche, Xabier Sarasola, Ortensia Dicuonzo, Ilia Ivashov, Kamil Sedlak, Davide Uglietti, Pierluigi Bruzzone

Published: 2019-09-01

Everything You Need To Know

What is the primary function of the Central Solenoid (CS) coil in a fusion reactor?

The Central Solenoid (CS) coil generates the intense magnetic fields necessary to contain and control the plasma within a fusion reactor. These magnetic fields are crucial for maintaining the plasma's stability and allowing the fusion reaction to occur.

How does the Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design improve upon previous coil designs?

The Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design improves upon previous designs by strategically utilizing different superconducting materials: HTS (High-Temperature Superconductors), Nb3Sn (Niobium-Tin), and NbTi (Niobium-Titanium). HTS is used in the highest field layers for superior performance, Nb3Sn in intermediate layers for a balance of cost and performance, and NbTi in the outermost layers for cost-effectiveness. This hybrid approach optimizes magnetic flux generation, manages mechanical stresses, and contributes to longer plasma burn times and improved power plant efficiency.

Why are different superconducting materials like HTS, Nb3Sn, and NbTi used in the Hybrid DEMO CS coil?

Different superconducting materials are used in the Hybrid HTS-Nb3Sn-NbTi DEMO CS coil to optimize performance based on their characteristics at varying magnetic field strengths. HTS is employed in the highest field layers where its superior high-field performance is crucial. Nb3Sn is used in intermediate layers, balancing cost and performance, while NbTi is used in the outermost layers, providing a cost-effective solution for lower field applications. This strategic layering maximizes magnetic flux and ensures the coil's structural integrity.

What are the specific roles of HTS, Nb3Sn, and NbTi within the Hybrid DEMO CS coil design, and why are they positioned as such?

In the Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design, HTS (High-Temperature Superconductors) are used in the innermost layers where the magnetic field is strongest, providing high critical current densities at high fields. Nb3Sn (Niobium-Tin) is positioned in the intermediate layers, offering a balance between cost and performance in moderately high magnetic fields. NbTi (Niobium-Titanium) is located in the outermost layers where the magnetic field is weakest, providing a cost-effective solution for lower field applications. Their placement is based on their respective performance characteristics at different magnetic field strengths, ensuring optimal overall coil performance, maximizing magnetic flux and managing mechanical stress within the coil.

How does the Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design contribute to achieving longer plasma burn times in fusion reactors, and what are the implications of this?

The Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design contributes to longer plasma burn times by maximizing magnetic flux generation and ensuring structural integrity through its strategic use of HTS, Nb3Sn, and NbTi. The advanced coil design allows the reactor to maintain the plasma confinement for a longer duration, which is essential for sustained fusion reactions. Longer burn times are a key step towards achieving more efficient and sustainable fusion power, as they improve the overall energy output and efficiency of the reactor, moving the prospect of clean, abundant fusion energy closer to reality.