Nuclear magnetic resonance magnetic-field fixation apparatus

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a nuclear magnetic resonance (NMR) measuring device, and more particularly to an NMR magnetic field fixing device that corrects a change in tuning frequency when a sample is rotated in an NMR detection coil.

【0002】

[Conventional technology]

FIG. 2 is a diagram illustrating a conventional NMR magnetic field fixing device. In the figure, an NMR measurement sample 1 and an NMR signal detection coil 2 are arranged in an NMR electromagnet 3 made of a superconducting magnet or the like, and a resonance signal when a high-frequency signal is applied to the measurement sample is detected. An electromagnetic correction coil 10 is arranged in the NMR electromagnet 3, and a magnetic field correction current is supplied from the magnetic field correction voltage generator 16 so that the magnetic field applied to the NMR measurement sample becomes uniform. The high frequency circuit A for fixing the magnetic field is controlled by the timing controller 15 and applies a high frequency signal to the NMR signal detection coil 2 through the distributor 8, the amplifier 9, and the switch 4 to apply the signal from the frequency generator 7, and at this time. Resonance signal is received through the switch 4 and amplifier 5, the detector 6 detects the signal from the frequency generator 7, and the magnetic field correction voltage generator 16 generates the correction signal based on the detection signal to generate the electromagnetic correction coil. A current is supplied to 10 and the magnetic field is controlled to be uniform. The switch 4 is switched by the timing control device 15 to supply the high frequency signal from the amplifier 9 to the NMR detection coil 2, and also switches the signal from the NMR signal detection coil 2 to the detector 9 through the amplifier 5. Is going. With such a configuration, a correction current is supplied to the electromagnetic correction coil 10 to secure a uniform magnetic field, and high-precision measurement is possible.

【0003】

[Problems to be Solved by the Invention]

By the way, since NMR uses a high-frequency resonance phenomenon caused in a strong uniform magnetic field, it is necessary to homogenize the magnetic field, and in order to average the non-uniformity of the magnetic field, an NMR sample is often included. The NMR signal is detected by rotating the sample tube in the NMR signal detection coil at about 15 Hz. However, since the sample tube rotates in the NMR detection coil, there is a problem that the tuning frequency of the detection circuit changes due to a change in the permittivity of the sample and the detection sensitivity decreases. As a countermeasure for this, it is necessary to correct the change in the tuning frequency, but such correction has not been performed in the conventional device.

【0004】

The present invention is intended to solve the above problems, and an object of the present invention is to constantly correct the deviation of the tuning frequency that changes due to the rotation of the sample so as not to lower the detection sensitivity.

【0005】

[Means for solving problems]

In the present invention, an NMR measurement sample and an NMR signal detection coil are arranged in a magnetic field generator, a magnetic field correction voltage is generated by the NMR signal detected when a high frequency signal is applied to the NMR measurement sample, and the magnetic field correction voltage is arranged in the magnetic field generator. In an apparatus in which a correction current is supplied to the magnetic field correction coil to homogenize the magnetic field, a tuning circuit is provided to apply a high-frequency signal to the NMR measurement sample and receive the output from the NMR signal detection coil. The reflected wave when a high-frequency signal is supplied to the circuit is detected, the constant of the tuning circuit is changed so that the detected reflected wave is minimized, and the change in tuning frequency due to the rotation of the sample in the NMR signal detection coil is changed. The feature is that it is corrected.

【0006】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a diagram illustrating an example of an embodiment of the present invention. In the figure, the same numbers as those in FIG. 2 indicate the same contents. It is the same as in FIG. 2 that the NMR measurement sample 1 and the NMR signal detection coil 2 are arranged in the NMR electromagnet 3 and the magnetic field is made uniform by the magnetic field correction coil 10. That is, the timing controller 15 switches and controls the switch 4, and the high frequency signal from the frequency generator 7 is added to the tuning circuit 11 via the distributor 8, the amplifier 9, the switch 4, and the directional coupler 12 to perform NMR. Irradiate the measurement sample 1 with a high frequency signal. At this time, the sample tube containing the sample that generates the NMR signal for fixing the magnetic field and the NMR signal detection coil 2 are placed at the center of the magnetic field for NMR generated by the NMR electromagnet 3. The resonance signal detected by the NMR signal detection coil 2 is received through the tuning circuit 11, the directional coupler 12, the switch 4, and the amplifier 5, and is detected by the detector 6 with the signal from the frequency generation 7, based on the detection output. The magnetic field correction voltage generator 16 supplies a correction signal to the magnetic field correction coil 10 to correct the magnetic field and secure a uniform magnetic field.

【0007】

The present invention further includes a tuning frequency correction circuit B. The excitation high frequency signal and the detection signal pass bidirectionally between the NMR signal detection coil 2, the tuning circuit 11, the directional coupler 12, and the switch 4, and the NMR detection guided from the tuning circuit 11 to the directional coupler 12 The signal is guided to the switch 4 and the amplifier 13, and the high frequency signal input from the switch 4 toward the directional coupler 12 is not output to the amplifier 13 side. The high-frequency reflected wave applied to the NMR signal detection coil 2 passes through the tuning circuit 11 and returns to the directional coupler 12 and is guided to the amplifier 13 and the error detector 14. In the error detector 14, the reference signal is sent from the distributor 8 in a time-divided manner only during the time of high frequency application, the detection output is sent to the tuning circuit 11, and in the tuning circuit 11, the output from the error detector 14 is minimized. The tuning frequency is controlled by changing the variable capacitor of the tuning circuit. In this way, even if the detection circuit is out of tune due to sample rotation, it can always be corrected to the tuned frequency.

【0008】

[Effect of the invention]

As described above, according to the present invention, it is possible to always correct the tuning deviation of the detection circuit that changes due to the rotation of the sample so as not to reduce the detection sensitivity.

[Simple explanation of drawings]

[Figure 1]

It is a figure explaining the operation of the Example of this invention.

[Figure 2]

It is a figure explaining the conventional NMR magnetic field fixation apparatus.

[Explanation of symbols]

1 ... NMR sample, 2 ... NMR detection coil, 3 ... NMR electromagnet, 4 ... switch, 5 ... amplifier, 6 ... detector, 7 ... frequency generator , 8 ... Distributor, 9 ... Amplifier, 10 ... Electromagnetic Correction Coil, 11 ... Tuning Circuit, 12 ... Directional Coupler, 13 ... Amplifier, 14 ... Error Detection Device, 15 ... Timing controller, 16 ... Magnetic resonance voltage generator.