JPS6080727A - Method for measuring temperaturae without contacting - Google Patents

Abstract

PURPOSE:To measure a temp. independently of emissivity, shape and surroundings of a material whose temp. is to be measured by making positrons incident on the material to be measured, and measuring the temp. in accordance with gamma-ray intensity due to the positron disappearance. CONSTITUTION:The positrons are made incident on an extremely small part position of the material 1 whose temp. is to be measured from a position source 5 using unclide <22>Na, etc. by using a condensing lense 18, so that the positrons impinge to electrons in the material 1 and disappear, and two gamma-rays having 0.511MeV energy are jumped out in the opposite directions with each other. The energies of the gamma-rays made incident on gamma-rays detectors 8, 9 through slits 6, 7 are discriminated by preamplifiers 10, linear amplifier 11 and single channel crest analyzers 12, and are measured by a circuit 13, a counter circuit 14, and the temp. information is obtained basing on a calibration curve obtained previously in a computer 15. The temp. of an arbitrary surface of the material 1 is measured by moving a sample driving apparatus 16 by a command from the computer 15 through a driving apparatus control system 17.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a non-contact surface temperature measurement method, and particularly to a method for measuring a surface temperature without being influenced by the emissivity of an object to be measured or the surrounding environment of the object to be temperature measured. This invention relates to a non-contact surface temperature measurement method.

[Background of the invention]

Infrared thermometers are known as thermometers that can measure temperature without contact, and are useful for measuring the surface temperature of steel plates and other objects that are heated while stationary or running in industrial furnaces such as continuous annealing furnaces, and for industrial purposes. Not just a furnace.

Infrared temperature needles are used for process temperature control in many fields.

An infrared thermometer determines the surface temperature T of an object to be measured by measuring the radiant energy E emitted from the object, which is incident on the detection element of the infrared temperature needle. There is a difference between (1) and the surface temperature T of the temperature measuring object.
) holds true.

E=g・K−T” ・・・・・・・・・(1) Here,
ε is the emissivity of the object to be measured, K is a constant, T is the absolute temperature of the object to be measured, and n is a value calculated as a function of the radiation constant and the measurement wavelength.

As mentioned above, the infrared temperature needle measures the radiant energy E. Therefore, in order to determine the temperature T of the heated object by using the infrared temperature needle, as is clear from equation (1), Either the emissivity ε of the object to be measured must be known, or the emissivity ε at the time of temperature measurement must be known. In addition, if a heating device is installed around the object to be measured, the infrared temperature needle receives the radiant energy from the heater as well as the radiant energy from the object. There is a possibility that an error may be included in the temperature evaluation of the object to be measured.

To solve this problem, infrared temperature needles and surface roughness measuring instruments (
A method of simultaneously measuring emissivity and surface temperature using a roughness meter (roughness meter) has been proposed (Japanese Patent Application Laid-open No. 85079/1983).
In addition, several other proposals have been made regarding surface temperature measurement methods using infrared temperature needles, but all of them have the problem that it is necessary to measure the emissivity of the object to be temperature measured. Furthermore, in these methods, if the surface condition of the heated object changes from time to time due to oxidation or adhesion of impurities, and the emissivity changes accordingly, the surface temperature is continuously adjusted. The drawback is that it cannot be measured. In addition, since infrared thermometers are based on the principle of measuring radiant energy from the temperature-measuring object, they require a measurement area of a certain size or more (approximately 1 mφ or more). Alternatively, there has been a problem in that it is difficult to apply when measuring the temperature at an arbitrary position of an object to be measured.

As a proposal to solve these problems and drawbacks, a surface temperature measurement method using an infrared thermometer as shown in FIG. 1 has recently been proposed. In this measurement method, as shown in Fig. 1, an artificial blackbody cover 3 is placed above the object L to be measured, and the emissivity of the object L to be measured is adjusted to the desired level. This is a method of measuring the surface temperature of the object to be measured 1 using an emissivity that is preset to a constant value determined only by the shape of the space between the body cover 3 and the surface of the object to be measured 1. Second, it has the effect of being able to measure the temperature regardless of the emissivity of the object 1 to be measured. However, the emissivity of the sensor is a function of the emissivity of the object to be measured 1 and the reflectance of the artificial fish body cover 3.
As shown in the figure, the area in which the emissivity of the mitsume can be considered to be substantially constant is limited to the shaded area in Figure 2, and for this reason, the range of the temperature measurement method shown in Figure 1 is limited to some extent. There is a problem with receiving it.

[Purpose of the invention]

An object of the present invention is to provide a non-contact temperature measurement method that can measure the surface temperature of an object, regardless of the emissivity and shape of the object to be measured, and the surrounding environment of the heated object, and that has high positional resolution. The purpose is to provide a method.

[Summary of the invention]

By using the fact that the intensity of the gamma rays generated when a positron is annihilated with a negative electron in the object to be measured by shooting a positron into the hot object to be measured depends on the temperature of the object to be measured, this gamma ray is Measures the surface temperature of an object based on intensity.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In this embodiment, positron source 5. First slit 6, second slit 7, first gamma ray detector 8. Second gamma ray detector9. Preamplifier 10. Linear amplifier 11. Single channel pulse height discriminator 12. Simultaneous circuit 13. Counting circuit 14. Calculator 15. Sample drive device 16. Drive device control system 17. Focusing lens 18
, and a high voltage power supply 19.

The positron source 5 emits positrons in order to inject the positrons into the temperature-measuring object 1, and the positron source 5 is made of a nuclide that emits positrons by nuclear decay (positron decay), such as "Na1B1CO". ,'7Nil I
In the present invention, it is convenient to use Na, which has a relatively long half-life of about 2.6 years and a high positron decay rate of about 91%. ing.

In this embodiment, a focusing lens 18 is used for the purpose of increasing the number of positrons incident on the object 1 to be temperature measured. A high electric field is formed in the focusing lens 18 by the voltage power source 19, and it is also possible to cause the positrons emitted from the positron source 5 to enter a minute portion of the temperature-measuring object l. Note that depending on the intensity of the positron source 50 or the distance between the positron source 5 and the object to be measured 1, the focusing lens 18 may not be used.
Needless to say, it is possible to use only the positron source 5.

Positrons emitted from the positron source 5 or focused by the focusing lens 18 and incident on the temperature-measuring object IK collide with electrons in the temperature-measuring object 1 and are annihilated. At this time, 0.
Two gamma rays with an energy of 511 MeV are emitted in opposite directions. In order to detect the two gamma rays emitted when positrons and electrons annihilate, two gamma ray detectors 8゜9 are placed on a straight line through the object to be measured. The annihilation gamma rays emitted from the object 1 to be temperature measured in opposite directions pass through the gap between the slits 6.7 placed in front of the gamma ray detector 8.9, and pass through the gamma ray detector 8.9.
, 9.

In Fig. 3, reference numerals 10 to 12 are ordinary gamma ray detection threads, and a preamplifier 1o and a linear amplifier 11 amplify the r# pulse signal incident on the detector 8.9 for single-channel pulse height analysis. The energy of the incident gamma rays is discriminated by the device 12. Signals from the two Fi single-channel pulse height analyzers are input to the simultaneous (b) path 13, and only the simultaneously input signals are measured by the counting circuit 14. Counting circuit 14
The counted value is input to the calculator 15, and is converted into temperature within the calculator 15 based on a predetermined calibration curve according to the principle of the present invention, which will be described later, and is output as temperature information.

The object to be measured l is placed on a sample drive device 16 that can be moved slightly in the X and Y directions, and the sample drive device 16 is connected to a computer 16 via a drive device control system 17. , has a function that allows temperature measurement at any position on the surface of the heated object 1 according to instructions from the computer 15.

Next, the principle of the temperature measurement method according to the present invention will be described below.

Positrons have the same rest mass as electrons (negative electrons).

A particle that has a charge that is equal in absolute value and opposite in sign to the charge (negative charge) of an electron. When a positron enters a substance,
It is decelerated to the level of thermal energy in a short time of about to-H seconds, is repelled by Coulomb interaction with the positively charged atomic nucleus in the substance, and as it moves relatively far from the atomic nucleus, Ki ! At this time, two (Dr rays) with energy (0,511 MeV) that reverberate with the rest mass of the electron are emitted in opposite directions (180').Positron movement in matter As mentioned above, the energy is approximately thermal energy (~0.025 eV), and strictly speaking, the kinetic energy of the electron is not necessarily 0, so the directions in which the two annihilation gamma rays are emitted are 180 degrees from each other.
'It will deviate slightly from the direction.

Figure 4 is a diagram showing the principle of the positron annihilation experiment, in which positrons emitted from the positron source 5 enter the sample 2° and annihilate with electrons in the sample. The two gamma rays emitted in opposite directions are each passed through the first slit 6.
The light passes through the gap between the second slits 7 and enters the gamma ray detector 8.9 provided at the rear of each slit. 1st
The gamma ray detector 8.9 passes through the slit 6 and the second slit 7.
If the input pulses are simultaneous, consider that the γ-rays are the same annihilation phenomenon, that is, the γ-rays are emitted at the same time as one electron annihilates in response to one incident positron. I can do it.

Now, if the first slit 6 is fixed, the second slit 7 is rotated around the sample 20, and the number of simultaneous measurements N(θ) is measured as a function of the rotation angle θ, a curve as shown in Fig. 5 is obtained. is obtained. The curve shown in FIG. 5 is called a γ-γ angular correlation intensity curve, and since the kinetic energy of electrons is not necessarily O, rotation angle dependence appears in the γ-ray intensity.

By the way, in the γ-r angle correlation strength curve, an experimental fact has been found that the number of simultaneous measurements N(0) at θ = 0 depends on the sample temperature (B, T, A, Mckeeeta
l, phys, 11. ev, I, ett, 28.3
58 (1972) l. FIG. 6 is a diagram showing the relationship between the number of simultaneous measurements N(0) and temperature for some metals, and it can be seen that the sample temperature can be evaluated based on the number of simultaneous measurements N(0). The details of the reason why the number of simultaneous measurements N (0) has temperature dependence are described in several papers (Masao Doyama, Applied Physics 41, 684 (1972), etc.), so the details will be omitted.

The present invention measures the temperature of an object to be measured by utilizing the fact that the number N(0) of coincidence j curves at θ = 0 of the r-r angle correlation strength curve with is dependent on temperature. It is based on a phenomenon that is physically completely different from that of infrared thermometry.

In the temperature measurement method of the present invention, positrons are injected from the outside of the temperature-measuring object and annihilation gamma rays with electrons in the temperature-measuring object are measured. It has an O-U point that is completely unaffected by the environment surrounding the temperature measuring object, and because it simultaneously measures annihilation gamma rays emitted in opposite directions, it is possible to measure only the annihilation phenomenon that represents temperature information. It has the advantage of a good /N ratio. Furthermore, the energy of the annihilation gamma ray is the energy equivalent to the rest mass of an electron (0,511 MeV).
Since this value does not change, it is not necessary to adjust the energy discrimination range in the single channel pulse height analyzer to the energy of the annihilation gamma rays, but it has the advantage of being able to selectively measure only the annihilation gamma rays. The S/N ratio is further improved, and it is possible to perform highly accurate measurements even with a small number of measurements.

Next, the time required for temperature measurement when using the temperature measurement method of the present invention will be discussed.

In FIG. 7, the positron source 5 is a point source, and the positron source 5
The solid angle at which the focusing lens 19 is viewed from is ΩI, and the solid angle at which the vanishing point 21 faces the detector 8 (or 9) is Ω! , if we allow ±2 milliradians from θ=0 as the width of the peak value in the γ-γ angle correlation strength curve, we get (3). Here, γ is the radius of the focusing lens 18, and t is the distance between the positron source 5 and the focusing lens 18. If the intensity of the positron source 5 is AC; (Curie), then the number of r-ray particles X entering the detector 8.9 can be expressed as:

On the other hand, the detection efficiency of the detector is, in the case of a NaI scintillator, if the total efficiency is Et and the peak-to-total ratio is P.
For a γ-ray with energy E, Etf(E J=P (
E) Calculated from XEt (E) - (5). For a 3 inch diameter x 3 inch thick NaI scintillator,
Energy of annihilation gamma ray (at 0,511 MeVl, P=
0.65, Ei (E) = 0.15 (#) (Masayasu Noro, γ-ray spectrometry, Nikkan Kogyo Shimbun) Therefore, the detection efficiency of the detector is Erf (E) = 0.1... (6) becomes. The compensation rate of annihilation γ-rays is calculated from equations (4) and (6).

Even if the ratio between the distance t between the positron source 5 and the focusing lens 18 and the radius of the focusing lens is 1:1, the counting rate of annihilation gamma rays is about 0.
At 28 CpS, for example, as shown in FIG. 6, the time required to obtain 100 simultaneous counts is about 6 minutes, making it possible to measure temperature in a relatively short time.

Next, regarding resolution, infrared thermometers measure the radiant energy from the object being measured, so to a certain extent (1 fin φ
In contrast, in the temperature measurement method according to the present invention, the positrons emitted from the positron source can be incident on a minute part (< 1 wanφ) of the object to be temperature measured using a focusing lens. Even if the positrons are not focused and are incident on the sample surface, the sample driving device
For example, if a device used in a microscope etc. is used, 0.1
Since it is sufficiently possible to move the sample in fin steps, it is possible to obtain a positional resolution that is at least about 10 times higher than that of an infrared thermometer.

As described above, the temperature measurement method according to the present invention is based on utilizing the temperature dependence of the number of simultaneous measurements N(0) at θ=0. Therefore, first measure the number of simultaneous measurements N(0) and the temperature (measuring with a thermocouple or the like) for a sample having the same composition as the hot object on the side, and create a curve as shown in Figure 6. It is necessary to Once the relationship between the number of simultaneous measurements N (0) and the sample temperature is established, the sample temperature can be determined by the number of simultaneous measurements N (0).
By inputting the relational expression as a function of (0) into the computer, it is possible to automatically convert the simultaneous clock value input into the computer while measuring the temperature of the object to be measured into temperature and output it.

As described above, this embodiment has the effect of overcoming all of the disadvantages of infrared thermometers, namely emissivity, stray light, and low resolution, and also has the following advantages: 1) Coincidence 11) Positron annihilation γ Line energy is constant (0,511M
eV), it has the advantage of having a good S/N ratio because of two points: by adjusting the incident energy width of the single channel pulse height analyzer, only the annihilation gamma rays can be placed on the needle side.

[Modifications/Applications]

FIGS. 8 to 10 show a modification of the present invention. 8th
The figure shows an example in which a positron focusing lens system is installed in order to increase the number of positrons incident on the object 1 to be temperature measured, with a positron reflector electrode 22 at the rear of the positron source 5 and an extraction electrode 23 at the front. A focusing lens 18 is provided. The positron reflector electrode 22 has a paraboloid of revolution shape, and the positron source 5 is placed at its focal point. By applying a positive voltage to the positron reflector electrode 22, positrons emitted in the 4π direction from the positron source 5 placed at the focal point of the paraboloid of revolution are transferred to the positron reflector electrode 22.
2 and is guided in the direction of the temperature measurement object 1,
The number of positrons incident on the object to be measured 1 increases.

FIG. 9 and FIG. 1θ show a modification example for improving the gain on the detector side, and in FIG. 9, a plurality of γ-ray detectors 9 are set as one set to constitute a γ-ray detector group. , one or more pairs of gamma ray detectors are arranged in a straight line with the temperature measured object l interposed therebetween. Further, FIG. 10 shows an example in which one or more pairs of γ-ray detectors are arranged in a straight line with the temperature measurement object 1 interposed therebetween.

〔Effect of the invention〕

According to the present invention, since it is not affected at all by the emissivity and shape of the temperature-measuring object and the surrounding environment of the temperature-measuring object, it is effective in measuring the surface temperature and the temperature of a minute part.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of an infrared temperature measurement method. Fig. 2 is a schematic diagram showing the region where the emissivity can be regarded as constant, using the emissivity of the object to be measured and the reflectance of the artificial blackbody cover, and Fig. 3 is a schematic cross-section of the temperature measuring device according to the present invention. Figure 4 shows the principle of positron annihilation experiment, Figure 5 shows the γ-γ angle correlation strength curve, and Figure 6 shows the annihilation γ
A diagram showing the relationship between the coincident value of the line and the temperature of the object to be measured, Figure 7 is a schematic diagram of how to calculate the number of particles incident on the detector,
FIGS. 8 to 10 are schematic sectional views showing modifications of the present invention. 1...Temperature measured object, 2...Infrared thermometer, 3...
Artificial black body cover, 4... Objective auxiliary cover, 5... Positron source, 6... First slit, 7... Second slit, 8.9... γ-ray detector, 10...・Preamplifier, 1
DESCRIPTION OF SYMBOLS 1... Linear amplifier, 12... Single channel pulse height analyzer, 13... Simultaneous circuit, 14... Counting circuit,
15... Computer, 16... Sample drive device, 17...
- Drive device control system, 18... Focusing lens, 19...
High voltage source, 20... Sample, 21... Vanishing point, 22.
...Positron reflector - Figure 1 Figure 2 Rotating tube (Figure 6) C'1r) x toooo (W- Figure 7

Claims (1)

[Scope of Claims] 1. A non-contact temperature measuring method of an object, characterized by injecting positrons into the object to be temperature measured and measuring the temperature based on the annihilation r-ray intensity of the positrons. 2. In the method according to claim 1, γ-r
A non-contact temperature measurement method characterized by using an angular correlation intensity curve. 3. A non-contact temperature measuring method according to claim 2, characterized in that the temperature dependence of the r-ray peak intensity is used.