Squashed liquid NMR sample tubes and RF coils
AssigneeVarian, Inc.
InventorThomas de Swiet
Life of this patent
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Abstract
Nuclear magnetic resonance (NMR) systems and methods employing squashed (transversely-elongated) sample vessels (sample tubes or flow cells) for holding liquid NMR samples, and matching squashed saddle-shaped RF coils allow reducing sample and/or coil losses and increasing the RF circuit quality factors (Q). In a present implementation, the RF coils and sample vessels have rectangular cross-sections. Rounded (e.g. ellipsoidal) or other squashed cross-sections may also be used. The coil corresponding to the highest sample losses is positioned such that the magnetic field generated by the coil is along the major axis of the sample vessel. Squashed sample vessels may also be used with conventional circular coils, particularly for low-temperature measurements where sample losses dominate.
Claims10
An NMR probe for coupling an RF circuit to nuclei of a sample, said probe comprising,
- a sample containing vessel, said vessel having an extension along a symmetry axis, z, and a cross section σ(x,y) transverse to said axis z, wherein said cross section σ(x,y) has an aspect ratio x/y greater than 1.2, and
- an RF resonator comprising a saddle coil surrounding said sample containing vessel for coupling RF energy between said sample in said sample vessel and said RF circuit.
The method of coupling an RF circuit to a sample for NMR analysis comprising the steps of
- a) imposing a unidirectional polarizing field on said sample,
- b) confining said sample to occupy a volume having a long axis z, parallel with said polarizing field and said volume further characterized by a cross section σ(x,y) transverse to z wherein x/y≧1.2,
- c) orienting a RF magnetic field coupled to said sample along said x axis whereby the greater thickness of said sample is interposed along the direction of said RF magnetic field.
Dependencies are inferred from the claim text.