JP3160089B2 - Tuning method of NQR probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear quadrupole resonator.
The present invention relates to a tuning method of a QR probe, and more particularly, to a tuning method that enables tuning of a probe having a wide tuning frequency range in a short time.

[0002]

2. Description of the Related Art NQR (Nuclear Quadrupole Resonanc)
e) The device is a device for observing resonance due to the interaction between the quadrupole moment of the nucleus and the electric field gradient generated by the structure of the crystal. The width of the NQR signal is approximately 10 MHz to 100 MHz.
There are up to about MHz, and the frequency width is very wide. Therefore, it is necessary to measure the signal strength one by one while sequentially changing the observation frequency. Depending on the measurement sample, 500 to 1000 points must be measured.
Then, after the measurement is completed, one data as illustrated in FIG. 7 is obtained by connecting the peaks of the measurement signals one by one by data processing with a computer.

[0003]

As described above, when taking NQR data one by one while changing the observation frequency,
An operation for adjusting the resonance frequency of the QR probe to the observation frequency, that is, tuning is required. Performing all of these operations manually is extremely poor in operability.
The following problems occur.

A) An operator must be present at the time of measurement. b) Measurement takes time. c) Since the number of operations is large, operation errors are likely to occur, and the measurement accuracy of the obtained NQR signal is poor.

[0005] The present invention has been made in view of such a situation, and an object thereof is to provide an NQR having a wide tuning frequency range.
It is an object of the present invention to enable tuning of a probe in a short time and to enable automation.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, a method of tuning an NQR probe according to the present invention is to apply a variable frequency observation frequency to an NQR probe having an adjustable capacitor, and adjust the capacitor to adjust the frequency to each frequency. In the tuning method of the NQR probe set at the best tuning point, the resonance frequency range of the target probe is divided into three or more points in advance, and the position of the capacitor and the tuning frequency at each of the dividing points are obtained in advance. seek tuning expected position X _d of the capacitor in the observation frequency of a specific frequency f _m based on the position and the tuning frequency of the capacitor, then, moved to the tuning expected position X _d determined the position of the capacitor, the frequency f _m The best tuning point near the position _Xd is obtained while applying the observation frequency.

[0007]

According to the present invention, in advance, divides the resonance frequency range of interest the probe above three points, to previously obtain the position and the tuning frequency of the capacitors in each segment point, in the observed frequency of a particular frequency f _m, determined Using the relationship between the position of the capacitor at each section point and the tuning frequency, the expected tuning position _Xd of the capacitor at that frequency is determined, and then the position of the capacitor is moved to the determined expected tuning position _Xd. ,
Its position X while applying the observation frequency of the frequency f _m
Since the best tuning point near _d is obtained, the range for obtaining the tuning point at each frequency is reduced, and the tuning speed is increased. Therefore, it is possible to shorten the time for the comprehensive NQR measurement. Further, tuning can be automated.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tuning method of the NQR probe according to the present invention will be described below based on embodiments. FIG. 1 is a block diagram of a configuration for automatically performing the tuning method of the present invention.
In the figure, 1 is an oscillator, 2 is a gate circuit, 3 is a power amplifier, 4 is a directional coupler, 5 is an NQR probe, 6 is AD
A converter, 7 is a detector, 8 is an MPU, 9 is a pulse generator,
10 is a motor driver and 11 is a motor. NQR
A high frequency of a frequency for tuning the probe 5 is generated by the oscillator 1, and the oscillation output of the oscillator 1 is output to the gate circuit 2.
, And amplify by the power amplifier 3. The output signal of the power amplifier 3 is supplied to the NQ through the directional coupler 4.
Applied to the R probe 5. The power reflected by the NQR probe 5 is detected by the directional coupler 4 and detected by the detector 7. The detection output is converted into a digital signal by the AD converter 6 and taken into the MPU 8. MPU8 is
An appropriate pulse is generated from the pulse generator 9 so that the detection output is minimized, the pulse is applied to the motor driver 10, the motor 11 is rotated, the variable condenser of the NQR probe 5 is adjusted, and its tuning is performed. do. After this tuning is completed, NQR measurement is performed, and the process moves to the next frequency. The change of the frequency oscillated from the oscillator 1 is performed based on, for example, a command from the MPU 8.

The variable condenser of the NQR probe 5 and the motor 11 are connected by a flexible wire or the like.
The rotation of one rotates the volume. The NQR probe 5 is provided with a dial whose display value changes in conjunction with the tuning knob.
The mechanical position of the variable condenser can be known from the dial value. In order to cover a wide frequency range, the resonance coil of the NQR probe 5 has a replaceable structure.

Now, in such an arrangement, the oscillator 1
FIG. 2 shows a basic flow for matching the observation frequency oscillated by the NQR probe 5 with the resonance frequency.

As is apparent from FIG. 2, the tuning method of the present invention is roughly divided into pre-tuning in FIG. 2 b) and final tuning in d), the details of which will be described later. The pre-tuning is for completing the final tuning performed for each frequency in a short time.

Now, the contents performed in each step of the flow of FIG. 2 will be described. The reading of the condition given from the outside of a) and the checking of the value are performed by reading the condition used in the pretuning of the next b) and checking whether the value of the given condition is appropriate. The conditions given are as follows.

[0013]-variable capacitor of the resonance of the probe in the dial value X _min of the current value X _r · variable capacitor of the dial frequency f resonance frequency of _min · variable capacitor probe in the dial value X _max of f _max · resonance frequency of the set value f _x (f ₁ , f ₂ , f ₃ ) where f _min , f at X _min , X _max
The value of _max is obtained by previously measuring the resonance frequency of the NQR probe 5 using a network analyzer or the like under the same conditions as the NQR measurement conditions. The resonance circuit of the NQR probe 5 has different resonance frequencies at room temperature and nitrogen temperature, for example, even if the dial value of the variable condenser is the same. Therefore, for example, when measurement is performed at the temperature of liquid nitrogen, measurement must be performed under such conditions. Then, N with respect to the dial values X _min and X _max of the variable condenser of the NQR probe 5
The relationship between the resonance frequencies f _min and f _max of the QR probe 5 is shown in FIG. 3, and the range between the dial values X _min and X _max indicates the mechanically usable range of the variable condenser (for example,
If the variable condenser value can be displayed from 0000 to 9999, 0500 is selected as X _{min and} 9500 is selected as X _max . ). In this case, the observation frequency is f _min
To f _max .

The current value X _r of the variable condenser dial is X
Any position between _min and _Xmax .

Also, set values f ₁ , f ₂ , f of the resonance frequency
₃ will be described later.

Next, the pre-tuning of FIG.
This is a preprocessing part for completing the final tuning of d) in a short time. This will be described below.

The relationship between X _min and f _min Dial variable capacitor, and, X _max and f from the relationship _max, setting the resonance frequency _{f x (f 1, f 2} , f 3) the expected value of the dial variable capacitor in X _d Is calculated from equation (1).

[0018] X _d = {X _{min ^{[(1 / f x 2) -}} (1 / f max 2) ] -X _{max ^{[(1 / f x 2) -}} (1 / f min 2) ]} ÷ [( ^{_{1 / f min 2) - (}} 1 / f max 2) ] + α ... (1) where, X _d: expected dial value of variable capacitor at the frequency f _x X _min: variable condenser mechanical limit minimum dial value X _max of : variable capacitor of the mechanical limitations of the maximum dial value f _min: resonance frequency in X _min f _max: resonance frequency in the X _max f _x: setting the resonant frequency _{(f 1, f 2, f} 3) α: a correction value. The above equation (1) is obtained as follows.

The parallel resonance frequency f _x of the coil L and the capacitor C is expressed by f _x = 1 / [2π (LC) ^1/2].
By transforming this equation, LC = 1 / (4π ² f _x ² ) (2) L and C in the equation (2) are expressed by the following equations (3) and (4).
It is represented by

L = L ₀ + X _d L ₁ (3) C = C ₀ + X _d C ₁ (4) where L ₀ : inductance of the coil at a dial value of zero X _d L ₁ : at a dial value X _d Increase in inductance of coil C ₀ : capacitance of variable capacitor at dial value zero X _d C ₁ : increase in capacitance of variable capacitor at dial value X _d Therefore, LC = L ₀ C ₀ + X _d (L ₁ C ₀ + L ₀ C) ₁ ) + X _d ² (L ₁ C ₁ ) (5) where L ₀ C ₀ = A, L ₁ C ₀ + L ₀ C ₁ = B, and X _d ² (L ₁ C ₁ ) ≒ 0. And Equation (5) is as follows: LC = A + X _dB B (6) Substituting equation (6) into equation _{(2), A + X d} B = 1 / (4π 2 f x 2) ... obtain (7).

When the dial values are X _min and X _max , they are expressed by equations (8) and (9), respectively.

A + X _min B = 1 / (4π ² f _min ² ) (8) A + X _max B = 1 / (4π ² f _max ² ) (9) Equations (8) and (9) When solved, A = {1 / [4π ² (X _max −X _min )]} × [(X _max / f _min ² ) − (X _min / f _max ² )] (10) B = {1 / [ 4π ² (X _max −X _min )]｝ × [(1 / f _min ² ) − (1 / f _max ² )] (11) Equation (10) and substituting equation (11) into equation _{(7), X d = {} X min ^{_{[(1 / f x 2) -}} (1 / f max 2) ] -X _max [(1 / f _x ² ) − (1 / f _min ² )]｝ ÷ [(1 / f _min ² ) − (1 / f _max ² )]. This equation is the same as equation (1) except for the correction term α. The correction term α is for correcting an error based on the stray capacitance of the NQR probe 5 and the like, and is obtained experimentally.

When the expected value X _d of the variable condenser dial is obtained by using the equation (1), the variable condenser is immediately replaced with X.
moves to the position of the _d, searches the neighborhood of X _d, looking for the best point of tuning NQR probe 5, the dial of the resulting best point to X _d '.

[0024] In the pre-tuning b) of FIG. 2, this way, obtains three dial value at the resonance frequency _{f x (f 1, f 2} , f 3). That is, the set resonance frequency f _x is f ₁ , f ₂ , f ₃ and the best point X
₁ ', X ₂ ' X ₃ '

Here, as a method of selecting f ₁ , f ₂ and f ₃ , f ₁ is selected to be higher than f _min and lower.

F ₃ is smaller than f _max and chooses a higher frequency.

F ₂ selects an intermediate point between f ₁ and f ₃ .

The above f ₁ , f ₂ , f ₃ are given by the following equations (12):
Expressions (13) and (14) are used.

F ₁ = [(f _max −f _min ) × a ₁ + f _min ] (12) f ₂ = [(f _max −f _min ) × a ₂ + f _min ] (13) f ₃ = [( f _max −f _min ) × a ₃ + f _min ] (14) As the above a _{1 to} a ₃ , for example, the following values are taken.

A ₁ = 0.1 a ₂ = 0.5 a ₃ = 0.9 X ₁ ′, X ₂ ′, X ₃ ′ obtained by pre-tuning
And Figure 4 shows the relationship between _{f 1, f 2, f 3} .

As long as the components of the coil and the capacitor used in the resonance circuit of the NQR probe 5 are not replaced, only one pre-tuning operation is required. However, since the NQR measurement has a wide observation frequency, the measurement may be performed by exchanging a coil for tuning. If the relationship between the dial value and the resonance frequency is different, after this replacement, pre-tuning must be performed from the beginning in the same manner as described above.

FIG. 5 shows a flowchart of the pre-tuning described above.

Next, in step c) of FIG. 2, the reading of the externally applied condition and checking of the value are performed in the following step d) of reading the condition used in the final tuning. It is also checked for suitability. Specifically, the condition given from the outside, only the set value f _m of the resonance frequency.

Next, in the final tuning step d) of FIG. 2, in the condition of _{f 1 ≦ f m <f 2} ,
Equation (15), and in the condition of _{f 2 ≦ f m ≦ f 3} , using equation (16), to calculate a predicted value X _d Dial variable capacitor in the setting value f _m of the resonance frequency. Equations (15) and (16) are derived in the same manner as equation (1).

[0035] X _d = {X _{1 ^{'[(1 / f m 2) -}} (1 / f 2 2) ] -X _{2' ^{[(1 / f m 2) -}} (1 / f 1 2) ]} ÷ ^{_{[(1 / f 1 2) -}} (1 / f 2 2) ] _{+ α 1 ... (15) X} d = {X 2 ' ^{_{[(1 / f m 2) -}} (1 / f 3 2) ] -X _{3 ^{'[(1 / f m 2) -}} (1 / f 2 2) ]} ÷ ^{_{[(1 / f 2 2) -}} (1 / f 3 2) ] + α ₂ ... (15) wherein, alpha _1, alpha ₂ : Correction value When the expected value X _d of the variable condenser dial is obtained, the variable condenser is immediately moved to the position of X _d , similar to the pre-tuning, the vicinity of X _d is searched for the best point, and the dial value is changed. Set at that point. That point is the point tuned to the observation frequency. FIG. 6 shows a flowchart of the above final tuning.

Then, in FIG. 2 e), N of the observed frequency
After performing the QR measurement, it is determined whether or not the measurement of f) is completed. Unless the measurement is completed, the MPU 8 instructs the oscillator 1 to change the observation frequency in g), and changes the observation frequency to the next observation frequency. The NQR measurement of the final tuning operation c), d) and e) of the probe 5 is repeated.

While the embodiment of the tuning method for the NQR probe and the like of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made. For example, the configuration for automatically performing the present tuning method shown in FIG. 1 is an example, and is not necessarily required to be this circuit. For example, although a stepping motor has been described as a means for rotating the variable condenser of the NQR probe 5, another motor may be used. Further, a flexible wire is used as a means for connecting the variable condenser and the motor, but the same applies to this. In addition, three points of X ₁ ′, X ₂ ′ and X ₃ ′ at the set resonance frequencies f ₁ , f ₂ , and f ₃ are obtained by pre-tuning in step b) of FIG.
It does not need to be a point, but may be found in more points.
In this pre-tuning, the relationship between the dial value at three or more points and the resonance frequency at that position can be measured using other means, for example, a network analyzer. In Equations (1), (15), and (16) for obtaining the expected tuning point, the correction values α, α ₁ , and α ₂ are given. However, when the error between the expected point and the best point is small, zero is set. May be set.

[0038]

[0039]

As is apparent from the above description, according to the tuning method of the NQR probe of the present invention, the resonance frequency range of the target probe is divided into three or more points in advance, and the resonance position is tuned to the position of the capacitor at each point. The frequency is determined, and at the observation frequency of the specific frequency, the expected tuning position of the capacitor at that frequency is determined using the relationship between the determined capacitor position at each section point and the tuning frequency. Since the position is moved to the calculated expected tuning position and the best tuning point near the position is obtained while applying the observation frequency of that frequency, the range for obtaining the tuning point at each frequency is reduced, and the tuning speed is increased. Therefore, it is possible to shorten the time for the comprehensive NQR measurement. Further, tuning can be automated.

[Brief description of the drawings]

FIG. 1 is a block diagram of a configuration of an embodiment that automatically performs a tuning method of the present invention.

FIG. 2 is a flowchart showing a basic flow of tuning in the configuration of FIG. 1;

FIG. 3 is a diagram showing a relationship between a dial value of a variable condenser and a resonance frequency of a probe.

FIG. 4 is a diagram showing a relationship between a dial value of a variable capacitor obtained by pre-tuning and a resonance frequency of a probe.

FIG. 5 is a flowchart showing a pre-tuning flow.

FIG. 6 is a flowchart showing a flow of final tuning.

FIG. 7 is a diagram showing an example of NQR data after data processing by a computer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Oscillator 2 ... Gate circuit 3 ... Power amplifier 4 ... Directional coupler 5 ... NQR probe 6 ... AD converter 7 ... Detector 8 ... MPU 9 ... Pulse generator 10 ... Motor driver 11 ... Motor

Claims (1)

(57) [Claims] 1. A observation frequency of the variable frequency applied to NQR probe having an adjustable capacitor, to set the best tuning point for each frequency by adjusting the capacitor NQ
In the tuning method of the R probe , the resonance frequency range of the target probe is divided into three or more points in advance, and the position of the capacitor and the tuning frequency at each point are determined, and the position of the capacitor and the tuning frequency at each determined point are determined. tuning expected position X _d of the capacitor in the observation frequency of a particular frequency f _m determined, then, to move the tuning expected position X _d determined the position of the capacitor on the basis of the frequency f _m
A tuning method for an NQR probe , characterized in that the best tuning point near the position _Xd is obtained while applying the observation frequency.