FARADAY SHIELDING OF SOLID STATE NMR SAMPLES

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FARADAY SHIELDING OF SOLID STATE NMR SAMPLES

S. Saha, E.Y. Chekmenev, C. Li,
P.L. Gorkov, T.A. Cross and W.W.
Brey NATIONAL HIGH MAGNETIC FIELD LABORATORY,
1800 E. PAUL DIRAC DR., TALLAHASSEE, FL 32310.
ABSTRACT RF Heating of aligned membrane
samples is significant problem for static protein
structure experiments. Sample heating inside the
RF coil takes place due to the well known
inductive and dielectric losses. However,
inductive losses in a conducting sample volume
can not avoided as it results from the
alternating B1 field produced by the RF coil. D.
G. Gadian 1 has shown that by implementing
electrical screens, the dielectric loss resulting
from strong electric fields in the sample volume
can be eliminated to a great extent. We present
here the simulation results of the shielding
effect of solid state NMR protein membrane
samples at frequencies ranging from 400 MHz to
900 MHz. The simulations were performed in Ansoft
HFSS, which is based on the Finite-Element
Method. The use of Faraday shields (FS) around
the oriented protein membrane sample reduces the
heating by approximately half, with significant
improvement in B1 field intensity and
homogeneity.
Table 1a. Simulation results
Table 1b. Experimental results
Note The sample size in the experiments were
slightly different from the simulated sample.