Revolutionary Magnet Technologies
In the late 1990s, motivated by a vision, and equipped with unique knowledge and experience in superconductivity, magnetics and manufacturing automation, AML began a new paradigm in magnetic design and manufacturing. Challenged by highly complex magnet applications for U.S. and International laboratories, we at AML were convinced there was a better way to address the cost, reliability and capability of superconducting magnets.
So, AML developed CoilCADTM, the world’s most advanced magnet design software, and used this powerful tool to explore how radical new coil winding configurations could affect magnetic field characteristics. This created the opportunity to finally design superconducting magnets capable of unprecedented performance and reliability.
Then it happened. In 2002, we determined the operational “physics” of this remarkable approach and, in 2005, patented the technology as “Double-HelixTM“–the most significant advance in electromagnet technology in over a century.
With precise tilting or modulation of solenoid windings, Double-HelixTM provides virtually unlimited options in designing magnetic fields, so it can serve as a building block for bold new magnet and magnetic field configurations. As a result, the theoretical “perfect field” for any specific application can now be made a reality. This technology is a radical departure from conventional coil configurations, and has changed the performance standards for magnet field design, including:
- Enabling –the creation of complex 3D coils, and the application of advanced materials
- Configurations—allowing virtually unlimited design geometries and manufacturing solutions
- Field Quality—-assuring the “Perfect Field” of any multi-pole order with zero systematic errors
- Optimization—of field geometry, quality and performance
- Flexibility—including curved, twisted, straight, flared and “combined function”
- Reliability—robust, temperature stable, conductor stabilized and short-free
- Scalability—of size, field strength and variable aperture
- Manufacturing—automated, with no tooling or complex inserts
- Packaging—tailored to customer requirements and products
- Low Cost—rapid design, prototype development and economical automated manufacturing
How does Double-Helix™ work?
Double-Helix™ magnets consist of tilted solenoid winding planes. By varying the tilt angles, number of winding layers and modulation of wires within a layer, Double-Helix™ magnets can be designed to provide pure magnetic fields of any multi-pole order.
The simplest form of a Double-Helix™ magnet is shown below. In this configuration, the windings in the first layer (shown in blue) produce a transverse (or dipole) field component and an axial (or solenoidal) field component. The second layer (shown in green) also produces a transverse field component and an axial field component in the opposite direction. When combined, the pair of such windings with opposite tilt angles, assembled concentrically, result in axial field components that cancel and transverse components that add to produce a pure dipole field.
By reversing the current in the second layer of windings (shown in green), the transverse field component is now in the opposite direction compared to the first layer. The transverse field components now cancel and the axial components now add to produce a pure solenoid field.
Double-Helix™ is not limited to any pole configuration
Any number of higher-order multipole fields, such as quadropoles or sextupoles, can be obtained by a sinusoidal modulation of the axial position of the winding. The modulation of windings is independent of the geometry around which the windings are routed. This feature provides remarkable flexibility in packaging Double-HelixTM (DH) magnets while simultaneously obtaining a very well-defined and high-quality field.
Double-Helix™ is not constrained by geometry
DH is applicable to straight, bent, twisted or any other desired geometry magnet with virtually unlimited length. The ability to accommodate almost any shape enables novel uses and integration of magnets.
Combined functions, such a dipole with a small amount of sextupole, can also be implemented into the same coil winding by modulating the conductor path at more than one frequency.
AML’s Double-HelixTM discovery suddenly enabled previously unimaginable magnet configurations of virtually any shape and any number of magnetic poles. It was the first in a growing portfolio of revolutionary magnet innovations—which now also includes AML Direct Double-HelixTM, Stacked Saddle CoilsTM, Expandable CoilsTM and Transparent CoilsTM
AML Direct Double-Helix™
With Direct Double-HelixTM (DDH), we took our revolutionary configuration approach one step further by enabling coil, conductor and winding to be created “directly,” and in a single automated process. For resistive magnets, the coil can be optimized to change the cross section of the conductor along the coil path. This significantly reduces the coil resistance and accommodates very efficient cooling.
Direct Double-Helix™ magnet coils are designed to achieve optimum performance based on the unique capability to vary the conductor cross-section along a 3D path – significantly reducing coil resistance. Cooling is optimized by putting conductors in direct contact with coolant, which boosts “current density” of resistive copper magnets by a factor of 20X, approaching superconductor levels.
A game-changing technology, DDH enables the use of advanced materials, such as nanomaterials (and future superconductors), which may have ideal electrical or thermal performance characteristics, but are incapable of being fabricated into a conductor format. In the simplest application of DDH, the coil configuration is machined out of conductive material. A one-step process, the conductor is generated in-situ in a 3D like “printing” process, which gives the additional freedom of varying the conductor width and thickness throughout the winding–enabling complete optimization of the conductor power density.
Stacked Saddle Coils™
AML’s 21st century approach of unconstrained magnet design has led to amazing new geometries. Prior to this new paradigm, the only option was to apply 1800s electromagnetic technology, configured as saddle coils. This traditional configuration has been the reliable and long-serving mainstay of magnet-based solutions, but one of its key unresolved shortcomings is the fact that the coil ends negatively impact the quality of the field.
Using the capabilities of AML’s proprietary CoilCADTM software, and the ability to control all aspects of three-dimensional magnet winding configuration, AML set out to create the “perfect-field” saddle coil. If achievable, it would lead to very small, short and lightweight magnet-based products.
Today, this technology has been fully qualified and applied in complex superconducting magnets used in high-energy physics. With our built-in manufacturing process and proprietary “stacked” arrangement of the conductor, we achieved a number of important “firsts” in this application. Among them: a highly pure field in the coil ends, and a new standard for reliability and performance–including zero quench training and fast ramp rates.
In a call for innovative concepts, NASA rated space radiation mitigation as the “highest priority technology for human spaceflight.”1 In response, AML developed and prototypically demonstrated ultra-light and expandable superconducting coils as a portable means to deploy extremely large magnets for radiation shielding and energy storage.
Once again, AML has defied the impossible. As noted in published NASA reports, “However, the concept of expandable, superconducting magnets seems to violate all experience with existing superconducting magnets used for research and medical applications. Such (existing) magnets require support structures to avoid even microscopic movements of the superconductor, which are known to initiate quenching of the superconductor (i.e., transitions from the superconducting to the normal conducting state). Since Lorentz forces acting on the conductors in high-field magnets lead to a large”magnetic pressure” similar to forces acting in conventional pressure vessels, support structures of utmost stability are required for these magnets.”2
AML’s Expandable CoilsTM have significantly changed the paradigm of high-field magnets, with configurations that are launchable and deployable using magnetic pressure to expand large diameter coils.
Like so many of AML innovations, the development of a “transparent” coil is the result of tackling a very complex problem. In this case, an application called for superconducting-level magnetic field strengths, but operational specifications required the use of a copper-based magnet. An additional requirement was the ability to rotate the magnetic field and switch field directions–all via electronics and software.
The result—an extraordinary magnet offering the unique capabilities of Double-HelixTM geometries, but designed and manufactured in a configuration that yielded “current densities” over 200 A/mm2—approaching superconductor performance with a copper conductor and water cooling.