Home | Fields
of Research | Members
"Composite 90° and 180° Pulses to Compensate
for Radiofrequency Gradients in Toroid NMR Detectors"
K. Woelk and J.
W. Rathke, J. Magn. Reson. A 115, 106-115 (1995).
-
Two new pulse sequences, a composite 90° pulse and a composite 180°
pulse, have been developed to compensate for the extremely large radiofrequency
gradients in toroid NMR detectors. The composite 90° pulse has the
ability to transfer more than 98% of the equilibrium magnetization phase-correlated
into the xy plane of the rotating frame, even if the strongest B1
field is nine times the weakest. The composite 180° pulse attains 99%
inversion of the equilibrium magnetization in the same B1
gradient.
-
Trajectory calculations that follow the fate of the magnetization during
the new pulse sequences and during composite pulses reported in the literature
compared favorably with results derived from NMR experiments performed
within a toroid cavity probe.
-
Also, the T1 relaxation time of
chloroform was measured by using the inversion-recovery procedure in a
toroid cavity probe. When the standard pulses were substituted by the new
composite pulses, the dynamic range in signal intensity was increased by
a factor greater than two.
Back to Recent Publications
K. Woelk, October
20, 1998