Decoupling of excitation and receive coils in pulsed magnetic resonance using sinusoidal magnetic field modulation.

摘要: In pulsed magnetic resonance, the excitation power is many orders of magnitude larger than that induced by spin system in receiving coil or resonator. The receiver must be protected during and immediately after pulse to allow for energy stored resonator dissipate a safe level. time which signal not detected, instrumental dead-time, can shortened using magnetically decoupled receive coils. Such coils are oriented, with respect each other, way minimizes total flux produced one other. We suggest isolated degree tuning them separate frequencies. Spins excited at frequency, echo detected another. Sinusoidal field modulation rapidly changes Larmor frequency spins between detection events used ensure resonance conditions both this study, relaxation times trityl-CD3 were measured field-modulated EPR experiment compared results obtained standard method. tuned 245 256.7MHz, respectively. Using an available rapid-scan, cross-loop resonator, we demonstrated isolation improvement approximately 20-30dB due decoupling. Theoretical analysis, numerical simulations, proof-of-concept experiments substantial excitation-detection decoupling achieved. A L-band system, including small volume bi-modal equipped coils, was constructed demonstrate fivefold dead-time reduction comparison experiment. This achieved detuning 26MHz sinusoidal 480kHz.