Multi-layer resonator for magnetic resonance applications with the resonator structure itself allowing equal magnitude current during active operation
A resonator for magnetic resonance applications has a conductor element proceeding in an extension direction, that operates with a resonance current at a resonance frequency oscillating therein in the extension direction. The conductor element is tuned to the resonance frequency and has an overall length in the extension direction that is smaller than half of the wavelength of the resonance frequency. The conductor element is a multi-layer conductor with layers that are electrically insulated from each other that, in said extension direction, have layer ends that are capacitively coupled with each other. During operation of the conductor element at the resonance frequency, respective layer currents flow in the layers in the extension direction that are substantially equal in magnitude.
1. A resonator configured for magnetic resonance applications comprising:
a conductor element extending in an extension direction between opposite free ends of said conductor element and configured to operate with a resonance current at a resonance frequency oscillating in the conductor element in the extension direction, said conductor element being tuned to said resonance frequency and having a total length in said extension direction that is smaller than half of a wavelength of the resonance frequency;
said conductor element being a multi-layer conductor comprising a plurality of layers that are electrically insulated from each other;
in said extension direction, the respective layers having layer ends that are capacitively coupled with each other; and
said multi-layer conductor itself being structurally configured between said opposite free ends to cause layer currents, forming said resonance current at said resonance frequency, to flow in the respective layers in said extension direction that are substantially equal in magnitude relative to each other.
2. A resonator as claimed in claim 1 wherein said layer ends are located respectively at first and second conductor ends of the conductor element, and wherein said layers are cyclically interchanged at a plurality of interchange points.
3. A resonator as claimed in claim 2 wherein said interchange points are uniformly distributed along said extension direction.
4. A resonator as claimed in claim 2 wherein V=k·S/2, wherein V is the number of said interchange points, S is the number of said layers, and k is a whole number.
5. A resonator as claimed in claim 2 wherein V=(k ·S−1)/2, wherein V is the number of said interchange points, S is the number of said layers, and k is a whole number.
6. A resonator as claimed in claim 2 wherein said layers are planar layers, and wherein at least one of said planar layers is folded at said interchange points to produce said cyclical interchange of the layers.
7. A resonator as claimed in claim 1 wherein said layer ends are located at respective first and second conductor ends of the conductor element, and wherein each of said layers has notches therein proceeding transversely to said extension direction.
8. A resonator as claimed in claim 1 wherein said conductor element forms a torus, and comprising dielectric material between the respective layers, and wherein each layer has layer ends separated from each other by a gap in said extension direction, the respective gaps being non-overlapping along said extension direction.
9. A resonator as claimed in claim 8 wherein pairs of said gaps that are immediately adjacent to each other are offset along said extension direction by an angle slightly less than 180°.
10. A resonator as claimed in claim 8 wherein said dielectric material is selected from the group consisting of SiO 2 and Al 2 O 3 .