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Abstract:
Conventional schemes for active detuning of
volume coils require high negative bias vo
ltages (>300V) to prevent distortion of RF pulses at power levels of 1-2 kW. To extend the power handling capacity and avoid using high DC bias voltages we developed an alternative method of detuning. In this method the PIN diodes in the detuning circuits are shorted when the coil is
tuned and negatively biased with -12 V when the coil is detuned. To preserve the high QU of the TEM and, therefore, the coil’s
performance, a high impedance (~200
Ω) lump-element quarter wavele
ngth transformer was utilized.
