Figure 1 Circuit diagrams of RF-only coil, RF coil + DC coil, and RF coil + “RF transparent” DC coil. Note that in practice, feed wires of DC coils are typically twisted to cancel the Lorentz force. For simplicity, straight feed wires were shown here. For Bazooka-feedline [5] few-turn “RF transparent” DC coil, the shield of twisted wires (could be one shield for each wire or one shield for both wires) was shorted at the position that is 1/4 wavelength away from the DC coil, forming open circuits and block RF signal going through.

Figure 2 Circuit diagrams of many-turn “RF transparent” DC coil using float trap design. For many-turn DC coil, it may resonate close to the RF frequency even the feed port is broken using the bazooka feedline method (A). In this case, it still can be seen as a coupled lossy resonator and leads to SNR loss. The float trap [6] is a concentric resonator that inductively couples and traps the RF signal going through it. It is expected to break every turn of the DC coil that goes through the trap and thus avoid unwanted resonate modes.