JPH04361182A - Correction method of rotation vibration of sample tube in nmr device - Google Patents

Abstract

PURPOSE:To reduce the magnitude of SSB caused by rotational vibration hard to dissolve by mechanical accuracy. CONSTITUTION:In an NMR device to do the NMR observation by holding a sample tube 3 in a rotor 1 supported with an air bearing and rotating a sample tube 3 in a probe 5 together with a rotor 1, two oscillators 8, 9 are used for driving one with the pulse corresponding to the repetition period of the NMR observation using a CPU 1 and for irradiating the other with two signals of continuous wave with frequency adjacent to each other, then NMR signals are observed. Then, beat signals of the two frequencies and their spinning side band signals are taken in, the repetition period resulting in the least spinning side band and the pressure of the air bearing is detected and the correction of rotation vibration of the sample tube 3 is done. As a result, the NMR observation can be done with the condition of the least SSB magnitude caused by the rotational vibration hard to dissolve by mechanical accuracy.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a rotational shake correction method for a sample tube in an NMR apparatus in which the sample tube is held on a rotor supported by an air bearing and rotated integrally with the rotor within a probe for NMR observation. .

0002

[Prior Art] In an NMR apparatus for observing a liquid sample,
The sample tube is supported within the probe with an air bearing and is rotated at a frequency of about 10 to 20 Hz for observation in order to eliminate sample non-uniformity. In this case, there is a limit to eliminating warpage and maintaining concentricity due to the mechanical finishing and assembly accuracy of the sample tube and rotor that make up the rotating body, which causes rotational wobbling in the sample tube. Normally, the sample has a unique dielectric constant, which causes tuning deviation due to rotational vibration within the resonator. This dielectric constant becomes more effective as the frequency increases. This kind of synchronization error due to rotational vibration of the sample tube is caused by
This occurs depending on the rotation speed of the rotating body including the sample, and appears in the spectrum as a so-called spinning side band (SSB) signal. In addition, SSB is caused by non-uniformity in the static magnetic field or high-frequency magnetic field, and fluctuations in the internal electric field.

[0003] The sample rotating within the resonator acts as a dielectric and becomes part of the capacitance component of the resonator, and fluctuations in rotational motion act as changes in capacitance. Therefore, in an NMR apparatus, the stronger the magnetic field, the higher the need for tuning at a higher frequency, which increases the influence of fluctuations in rotational motion.

0004

[Problem to be Solved by the Invention] In order to reduce the influence of the above-mentioned fluctuations in rotational motion on the NMR apparatus, conventional methods have been used to mechanically finish warpage and concentricity of the sample tubes and rotors that make up the rotating body.・We tried to maximize assembly accuracy and paid particular attention to the materials used to maintain that accuracy.

[0005] However, there is a limit to the mechanical precision described above. Incidentally, the tolerance of runout for the rotating shaft of a rotating body required from experiments is approximately 10 μm when using a frequency of several hundred MHz, but this is at an extremely difficult level at this stage.

An object of the present invention is to reduce the amount of SSB caused by rotational runout that is difficult to eliminate due to mechanical accuracy.

[0007]

[Means for Solving the Problems] To this end, the present invention provides an NMR apparatus in which a sample tube is held on a rotor supported by an air bearing, and the sample tube is rotated integrally with the rotor within a probe for NMR observation. By observing the NMR signal by driving it with a pulse corresponding to the observation repetition period and irradiating it with two adjacent frequency signals, one of which is a continuous wave, the beat signal of two frequencies and the signal of its spinning sideband can be detected. The system is characterized in that it captures the amount of spinning sidebands, detects the repetition period and air bearing pressure that minimize the amount of spinning sidebands, and performs corrections due to rotational runout of the sample tube.

[0008]

[Operation] In the rotational shake correction method of the sample tube in the NMR apparatus of the present invention, one is driven with a pulse corresponding to the repetition period of NMR observation, and the other is irradiated with two adjacent frequency signals as a continuous wave. By observing the NMR signal, we capture the beat signal of two frequencies and its spinning sideband signal, and detect the repetition period and air bearing pressure that minimize the amount of the spinning sideband. N under conditions that minimize the amount of SSB caused by rotational runout that is difficult to eliminate with
MR observation can be performed.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining one embodiment of a rotational shake correction method for a sample tube in an NMR apparatus of the present invention.

[0010] In FIG. 1, a rotor 1 includes, for example, a holder 2 and is integrally constructed, and is supported by an air bearing (not shown) and a sample tube 3 is attached to the holder 2.
The sample tube 3 is held in the resonator 4 of the probe 5 and rotates integrally at a frequency of about 10 to 20 Hz. The duplexer or gate 6 separates the irradiation system on the power amplifier 7 side from the observation system on the head amplifier 12 side. Transmitter 8, 9
generate signals of frequencies fA and fB that are close to each other, and the emission is controlled by the pulser 10. The CPU 11 applies signals of two adjacent frequencies fA and fB to the probe 5 while controlling them according to the repetition period of NMR observation through the pulser 10, and observes the NMR signals through the head amplifier 12, thereby detecting the SS.
This is to detect the conditions under which the amount of B is the minimum.

As mentioned above, SSB is caused by the eccentricity of the holder and sample tube, and has periodicity. Therefore, the amount changes depending on the repetition period of NMR observation. The rotational shake correction method of the sample tube in the NMR apparatus of the present invention focuses on this point, detects the period in which SSB is minimum when changing the repetition period, and reduces SSB by adopting that period. It is something. The detection operation will be explained below.

[0012] The CPU 11 receives the frequency fA from the oscillator 8.
The pulser 10 is controlled so that the signal of frequency fB from the oscillator 9 is applied to the probe in the form of a continuous wave. In this case, the signal of frequency fA has a period t1 as shown in (b).
The pulse width is on the order of time giving the so-called flip angle. On the other hand, CPU11
Now, by performing FT (Fourier transform) processing on the signal taken in from the observation system, the beat signal S1 of |fA - fB | and the SSB signal S2 on both sides are generated in synchronization with the pulse period as shown in (c). It is captured. Therefore,
The CPU 11 integrates these signals and counts them as SS.
As the amount of B, α1 = |S2 |/S1 is calculated and stored. Similarly, the pulse period t1 is t2, t
3, ..., tn and set the frequency fA to probe 4.
, fB are applied, and the SSB amounts α2, α3, . . . , αn in each period are determined and stored. Then, the minimum value αx is detected from α1 to αn, and the corresponding period tx is determined.

By determining the repetition period of pulse excitation during actual observation using the period tx determined as described above, it is possible to reduce the amount of SSB caused by rotational runout. In addition, when observing actual samples,
If the period tx is not appropriate, a similar effect can be obtained by adopting a period that is an integral multiple of the period tx.

The amount of SSB is linked to changes in the repetition period of irradiation as described above, but also changes depending on the pressure of the air bearing. Focusing on this point and making this adjustment, SS
By detecting a condition in which the amount of B is the minimum and adopting that condition, it is possible to reduce the amount of SSB caused by rotational runout that is difficult to eliminate in terms of mechanical accuracy. Examples thereof will be described below.

FIG. 2 is a diagram for explaining another embodiment of the sample tube rotational shake correction method in the NMR apparatus of the present invention, in which instead of changing the excitation repetition period shown in FIG. It is configured to control the pressure and detect the condition that minimizes the amount of SSB. P1, P2, P3, and P4 indicate the pressures of each part of the air bearing 22, and the pressure controller 24 controls the pressures P1, P2, P3, and P4. Then, the CPU 25 sequentially calculates the pressure P1 of the air bearing 22, while fixing the excitation repetition period Tc through the same pulser 31, transmitters 30, 31, duplexer, or gate 28 as shown in FIG. 1, for example.
The pressure controller 24 is controlled to change P2, P3, and P4. On the other hand, the NMR signal after FT is observed through the duplexer or gate 28 and head amplifier 33 of the observation system, and the values of pressures P1, P2, P3, and P4 at each part of the air bearing that minimize the amount of SSB are determined.

That is, the CPU 25 controls the pressure P1 through the pressure controller 24 as explained in FIG.
, P2, P3, and P4 under the respective pressures, and by performing FT processing from the observation system, |fA as shown in Fig. 1(C) is synchronized with the pulse period.
The beat signal S1 of -fB | and the SSB signal S2 on both sides thereof are taken in. Then, these signals are integrated and counted, and the amount of SSB under each pressure α2, α
3,..., αn is determined and stored, the minimum value αx is detected from α1 to αn, and the corresponding pressures P1, P2 are calculated.
, P3 and P4 are determined.

Note that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in the above embodiment, explanation was given using a rotational shake correction sample, but an actual observation sample may also be used, or the NMR signal S1
It may be configured to monitor the SSB signal S2 and the SSB signal S2 to detect a condition in which the amount of SSB is minimized.

Furthermore, in the embodiment of FIG. 2, the repetition period T
Although an arbitrary value is used for c, the embodiment shown in FIG. 2 may be applied by applying the embodiment shown in FIG. 1 and setting the period tx at which the amount of SSB is the minimum. By doing so, the amount of SSB can be further reduced.

[0019]

[Effects of the Invention] As explained above, according to the present invention,
The repetition period of the high-frequency signal in NMR observation and the pressure of the air bearing are selected to minimize the amount of SSB, thereby reducing the amount of SSB caused by rotational runout that cannot be eliminated due to limits such as mechanical processing accuracy. Therefore, the spectral assignment can be easily determined in NMR observation.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of a rotational shake correction method for a sample tube in an NMR apparatus of the present invention.

FIG. 2 is a diagram for explaining another embodiment of the sample tube rotational shake correction method in the NMR apparatus of the present invention.

[Explanation of symbols]

1...Rotor, 2...Holder, 3...Sample tube, 4...Resonator, 5
...Probe, 6...Duplexer or gate, 7...Power amplifier, 8 and 9...Transmitter, 10...Pulser, 11...CP
U, 12...Head amplifier

Claims (1)

[Claims] Claim 1: In an NMR device that performs NMR observation by holding a sample tube on a rotor supported by an air bearing and rotating the sample tube integrally with the rotor within a probe, one side is
By observing the NMR signal by driving it with a pulse corresponding to the repetition period of R observation and irradiating it with signals of two adjacent frequencies, the other of which is a continuous wave, the beat signal of the two frequencies and its spinning sideband can be detected. A method for correcting rotational shake of a sample tube in an NMR apparatus, which captures a signal, detects the repetition period and air bearing pressure that minimize the amount of spinning sidebands, and performs correction due to rotational shake of the sample tube.