NMR measurement method

Abstract

There is disclosed an NMR measurement method and NMR apparatus in which the temperature of the NMR detection coil or the RF irradiation coil hardly varies if pulsed RF power is applied to the coil during NMR measurements. The apparatus includes the detection coil or the RF irradiation coil, a first RF power application means for applying RF power of a frequency necessary for measurement of NMR signals, a second RF power application means for applying RF power of a frequency not affecting the measurement of NMR signals, and a control means for controlling the two power application means such that the sum of the RF power applied to the coil from the first application means and the RF power applied to the coil from the second application means is kept almost constant.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an NMR measurement method and NMR apparatus and, more particularly, to an NMR measurement method and NMR apparatus using a detector assembly that is cooled to a cryogenic temperature by low-temperature helium gas to thereby enhance the sensitivity with which NMR signals are detected. [0003] 2. Description of Related Art [0004] In an NMR apparatus, a strong static magnetic field is applied to a sample to induce a precessional motion of the magnetic moment of each atomic nucleus having a nuclear spin within the sample about the direction of the static field. Under this condition, an RF magnetic field is applied perpendicularly to the direction of the static field to induce a precessional motion of the magnetic moment of the atomic nucleus. Then, an NMR signal released when the precessional motion of the magnetic moment of the atomic nucleus returns to ground state from an excited state...

AI Technical Summary

Benefits of technology

[0043] In a still additional feature of the present invention, the RF power of the frequency not affecting the measurement of the NMR signal can be so adjusted that the ratio of the RF power reflected from the detection coil or the RF irradiation coil to the RF power applied to the detection coil or the RF irradiation coil is minimized.

[0049] In a still additional feature of the present invention, the RF power applied from the second RF power application means can be adjusted based on the value of the power meter such that the reflected RF power is minimized.

Problems solved by technology

The prior art low-temperature cooled NMR probe has one problem.

However, the cooling capability is limited.

Consequently, the low temperature can no longer be maintained.

As a result, RF magnetic fields of desired intensity cannot be produced within the detection coil.

This problem produces an adverse effect during reception of an NMR signal, as well as during excitation of nuclear spins.

Hence, normal NMR signals cannot be obtained.

The similar problem will also occur at the provided RF irradiation coils.

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