Probe head for an NMR spectrometer
First Claim
1. Probe head for a NMR-spectrometer comprising at least one transmitter unit for generating electromagnetic excitation waves of high frequencies and at least one preamplifier unit (V) for amplification of signals emanating from a sample which has been excited by means of the excitation waves, with a cryogenically cooled primary detection circuit including at least a first antenna (1) and a first waveguide (2), whereby said first antenna (1) is connected to said preamplifier unit (V) via said first waveguide (2), characterized in that at least said first waveguide (2) operates in the range of the anomalous skin effect, whereby the mean free path of the charge carriers at least in said first waveguide (2) being larger than the electromagnetic skin-depth, and whereby said primary detection circuit is provided with means for temporarily matching it with its own characteristic impedance.
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Abstract
A probe head for an NMR spectrometer that provides enhanced signal to noise ratio in NMR measurements. The probe head uses at least a first waveguide to irradiate an NMR sample with an excitation wave and to conduct the emitted sample signal to the preamplifier and subsequent electronic signal processing equipment. The electrical conducting elements of the waveguide are constructed and operated under conditions such that the conductors operate in the regime defined by the anomalous skin effect and preferably in the regime defined by the extreme anomalous skin effect. The reduction in electrical resistance afforded by such construction and operation enables a reduction signal-to-noise ratio in the NMR signal detected by the probe. The invention includes in the preliminary detection circuit means for temporarily matching it with its characteristic impedance.
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Citations
27 Claims
- 1. Probe head for a NMR-spectrometer comprising at least one transmitter unit for generating electromagnetic excitation waves of high frequencies and at least one preamplifier unit (V) for amplification of signals emanating from a sample which has been excited by means of the excitation waves, with a cryogenically cooled primary detection circuit including at least a first antenna (1) and a first waveguide (2), whereby said first antenna (1) is connected to said preamplifier unit (V) via said first waveguide (2), characterized in that at least said first waveguide (2) operates in the range of the anomalous skin effect, whereby the mean free path of the charge carriers at least in said first waveguide (2) being larger than the electromagnetic skin-depth, and whereby said primary detection circuit is provided with means for temporarily matching it with its own characteristic impedance.
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11. Probe head for a NMR-spectrometer comprising at least one transmitter unit for generating electromagnetic excitation waves of high frequencies and at least one preamplifier unit (V) for amplification of signals emanating from a sample which has been excited by means of the excitation waves, with a cryogenically cooled primary detection circuit including at least a first antenna (1) and a first waveguide (2), whereby said first antenna (1) is connected to said preamplifier unit (V) via said first waveguide (2), characterized in that a second wave guide (3′
- , 3″
) is coupled in particular via at least one aperture to said first waveguide (2), that said second waveguide (3′
, 3″
) is connected with said transmitter unit, and means are provided for coupling the excitation wave from said second waveguide (3′
, 3″
) to said first wave guide (2), by which means the propagation of the excitation wave is suppressed in direction to said preamplifier unit. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
- , 3″
- 22. Probe head for a NMR-spectrometer comprising at least one transmitter unit for generating electromagnetic excitation waves of high frequencies and at least one preamplifier unit (V) for amplification of signals emanating from a sample which has been excited by means of the excitation waves, with a cryogenically cooled primary detection circuit including at least a first antenna (1) and a first waveguide (2), whereby said first antenna (1) is connected to said preamplifier unit (V) via said first waveguide (2), characterized in that a second antenna is provided, whereby said antennas are arranged such, that said first antenna (1) receives the NMR signal and the noise of said sample in the equatorial near-field of the like a Hertzian dipole radiating said sample and said second antenna receives only the noise of said sample in the axial near-field of said sample.
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27. Use of helium-II in a probe head for a NMR-spectrometer comprising at least one transmitter unit for generating electromagnetic excitation waves of high frequencies and at least one preamplifier unit (V) for amplification of signals emanating from a sample which has been excited by means of the excitation waves, with a cryogenically cooled primary detection circuit including at least a first antenna (1) and a first waveguide (2), whereby said first antenna (1) is connected to said preamplifier unit (V) via said first wave guide (2).
Specification