Proton traps for multi-nuclear RF coils: design analysis and practical implementation for 13C MRS in humans at 7T

Trapped coil designs allow the operation of lower-frequency coils in the presence of a proton coil. Adding a second capacitor to a trap in the non-proton RF coil allows control over the trap reactance at the low and high frequency (here 13C and 1H) and the frequency of the trap mode. We demonstrate the interdependence of the parameters controlled and show analytical and numerical solutions to fulfill the design constraints. Our experiments show that, using the simulations, it possible to construct an effective second order trap for 13C at 7T.