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We propose a new method to compute magnetic surfaces that are parametrized in Boozer coordinates for vacuum magnetic fields. We also propose a measure for quasisymmetry on the computed surfaces and use it to design coils that generate a magnetic field that is quasisymmetric on those surfaces. The rotational transform of the field and complexity measures for the coils are also controlled in the design problem. Using an adjoint approach, we are able to obtain analytic derivatives for this optimization problem, yielding an efficient gradient-based algorithm. Starting from an initial coil set that presents nested magnetic surfaces for a large fraction of the volume, our method converges rapidly to coil systems generating fields with excellent quasisymmetry and low particle losses. In particular for low complexity coils, we are able to significantly improve the performance compared with coils obtained from the standard two-stage approach, e.g. reduce losses of fusion-produced alpha particles born at half-radius from $$17.7\,\%$$ to $$6.6\,\%$$ . We also demonstrate 16-coil configurations with alpha loss $${<}1\,\%$$ and neoclassical transport magnitude $$\epsilon _{\text {eff}}^{3/2}$$ less than approximately $$5\times 10^{-9}$$ .
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NON-RESONANT VIBRATION ENERGY HARVESTER WITH WOUND MICRO-COIL ARRAYS
This paper describes a wrist-wearable non-resonant vibrational energy harvester (1.4 cc in volume and 3.2 gram in weight, with two arrays of wound copper coils adjacent to a movable array of magnets suspended by ferrofluid bearing) for generating power from a human's walking motion. Thousand-turn coils are wound with a customized coil winding machine, and two sets of such coils are mounted on the top and bottom of a movable magnet array to obtain 20% improvement (compared to the earlier version based on an electroplated coil array) on the figure of merit (FOM) defined to be the power (delivered to a matched load) divided by the device's volume for a given acceleration of 1 g at 2 Hz.
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- Award ID(s):
- 1911369
- PAR ID:
- 10512855
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- Transducers '23, The 22nd International Conference on Solid-State Sensors, Actuators and Microsystems
- Subject(s) / Keyword(s):
- Vibrational Energy Harvesters, Wearable Devices, Wearable Power Generator, Human Motion, Self-power, Sustainable Energy, Power MEMS, Non-Resonant Electromagnetic Harvester
- Format(s):
- Medium: X
- Location:
- Kyoto, Japan
- Sponsoring Org:
- National Science Foundation
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