JPH0431324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a displacement measuring device for cryogenic and strong magnetic fields that can satisfactorily measure displacement in special environments such as cryogenic temperatures and strong magnetic fields.

[Technical background of the invention and its problems]

When various materials are placed in a cryogenic liquid such as liquid helium and in a strong magnetic field, they are expected to exhibit mechanical properties that are different from those at room temperature. In this way, confirming the mechanical properties of various materials at extremely low temperatures and in strong magnetic fields has an important meaning in realizing nuclear fusion devices, which are seen as promising future energy sources.

By the way, the means for measuring the mechanical properties of various materials, such as fracture toughness, are determined in detail by JIS and the like. However, this method is based on room temperature conditions, and similar means cannot often be used in special environments such as extremely low temperatures and strong magnetic fields. That is, a cryogenic field is created by containing a cryogenic liquid such as liquid helium within a cryostat, and a strong magnetic field is created by the use of superconducting coils. Superconducting coils require a cryogenic liquid as a refrigerant, so by housing the cryogenic liquid and the superconducting coil in a cryostat, it is possible to maintain a cryogenic temperature inside a closed room called a cryostat. field and a strong magnetic field. In this way, it is relatively easy to simultaneously create a cryogenic field and a strong magnetic field. but,
To perform a fracture toughness test in such a field, it is necessary to measure the displacement of the sample. Clip-on gauges and capacitance detectors are normally used to measure this displacement, but these cannot be used because they are affected by the magnetic field. Therefore, the problem is how to measure the displacement of a sample located in a closed room without being influenced by the magnetic field. The reality is that no fracture toughness tests have been conducted.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to be able to satisfactorily measure mechanical displacement in a cryogenic strong magnetic field, and to conduct fracture toughness tests, etc. under the above environment. The object of the present invention is to provide a displacement measuring device for cryogenic strong magnetic fields that can contribute to the

[Summary of the invention]

According to the present invention, a means for positioning an object to be measured to be displaced in liquid helium and applying a strong magnetic field to the object to be measured to be displaced, and a means disposed outside the cryogenic strong magnetic field formed by the means, a light source device that sends out infrared cut illumination light; a light guide that guides the illumination light sent out from the light source device into the cryogenic strong magnetic field and irradiates the displaced object; and the displaced object. an image guide that transmits a reflected light image from the ultra-low temperature strong magnetic field to the outside of the cryogenic strong magnetic field; a television camera that photoelectrically converts the image of the displaced object transmitted through the image guide;
and a television receiver for projecting an image of the object to be displaced by introducing the video signal sent from the television camera, and detecting the displacement of the object to be displaced from the image projected on the television receiver. A displacement measuring device for a cryogenic strong magnetic field is provided.

〔Effect of the invention〕

According to the present invention, the image of the object to be displaced is guided outside the extremely low temperature strong magnetic field using a transmission system such as a light guide and an image guide that is unaffected by temperature and magnetic fields, and the image is projected onto a television receiver. The displacement is measured from this projected image. Therefore, displacement can be measured without being affected by temperature or magnetic field. Also,
Since the image guided through the image guide is captured by a television camera, a large magnification can be set, and as a result, highly accurate displacement measurement can be performed. In this case, since we are using particularly infrared-cut illumination light, that is, illumination light that does not have a wavelength range that is easily absorbed by liquid helium, many fine bubbles may be generated in liquid helium due to illumination light irradiation. As a result, the image of the object to be displaced can be clearly projected on the television receiver, so that displacement measurement can be performed with higher accuracy.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. Note that the figure shows an example in which the present invention is applied to a fracture toughness testing device.

In the figure, 1 is a cryostat;
This cryostat 1 has an inner tank 2, an outer tank 3,
It is comprised of a lid body 4 that selectively covers the upper opening of the inner tank 2. The space 5 existing between the inner tank 2 and the outer tank 3 is evacuated and formed into a vacuum insulation layer. A superconducting coil 6 excited by an external power source (not shown) is housed in the inner tank 2 with its axis facing upward and downward, and liquid helium 7 is provided at a level where the superconducting coil 6 is sufficiently submerged. It is accommodated.

A tensile force applying mechanism 8 is supported by a support column 9 above the cryostat 1 and is movable up and down along the support column 9 in the direction indicated by a solid arrow 10 in the figure. The tensile force applying mechanism 8 includes a fixed rod 1 that extends downward in parallel.
1 and a movable rod 12, and is configured to apply a tensile force by moving the movable rod 12 upward relative to the fixed rod 11 using a drive source (not shown). The fixed rod 11 and the movable rod 12 extend into the inner tank 2 through the lid 4 of the cryostat 1, and have their lower ends located within the area surrounded by the superconducting coil 6. A sample holding mechanism 14 is provided between the lower end of the fixed rod 11 and the lower end of the movable rod 12 to face each other vertically and to support the upper and lower ends of the sample piece 13 formed in a predetermined shape. .

On the other hand, one end of the light guide 21 and one end of the image guide 22 are inserted into the inner tank 2 through the lid 4 of the cryostat 1, respectively. The end portion 23 of the light guide 21 located inside the inner tank 2 is close to the notch P provided in the sample piece 13, and is arranged such that its optical axis faces the notch P at a predetermined angle. Image guide 22
An objective lens 24 is attached to the end located in the inner tank 2 of the sample piece 1.
It is located close to the notch P of No. 3 and in such a manner that its optical axis faces the notch P at a predetermined angle.
Then, the light guide 2 arranged as above
One end of the image guide 1 and one end of the image guide 22 are supported by the fixed rod 11 via supporting members 25 and 26, respectively. The other end of the light guide 21 located outside the cryostat 1 is the light source device 2.
7 is connected. This light source device 27 includes a light source device main body 28 that has a built-in lamp, and a filter 2 that introduces light that cuts out infrared rays from the light sent out from the light source device main body 28 into the light guide 21.
It consists of 9. An end of the image guide 22 located outside the cryostat 1 is connected via a connector 30 to a magnifying lens system of a television camera 31. A video signal sent from the television camera 31 is introduced into a television receiver 33 via a camera controller 32.

In the figure, numeral 34 indicates a magnetic shielding material that magnetically shields the television camera 31, camera controller 32, and television receiver 33.
Further, 35 indicates a valve for introducing liquid helium, and 36 and 37 indicate valves for exhaust.

Next, an example of use of the fracture toughness testing apparatus configured as described above will be described.

First, loosen and remove the bolts tightening the cover body 4 of the cryostat 1, and in this state raise the tensile force applying mechanism 8 along the support column 9 to the position where the sample holding mechanism 14 comes out of the cryostat 1. . Next, the sample piece 13 of which the width of the cut P is known is mounted on the sample holding mechanism 14. Next, the light guide 21 is positioned so that the light emitted from the tip 23 of the light guide 21 is irradiated onto the notch P, and the image is set so that the light reflected from the notch P can be received. The objective lens 24 of the guide 22 is aligned. In this state, the image of the notch P actually projected on the receiver 33 is observed, and the camera controller 32 is adjusted to set the magnification and the image projected on the receiver 33 is brought into focus. Objective lens 24
Fine-tune the position. Next, taking into account the distance from the notch P to the objective lens 24 and the refractive index of liquid helium, the calibration curve is determined in advance to avoid defocusing due to the influence of the refractive index of liquid helium. Then, the position of the objective lens 24 is further finely adjusted. When such adjustment is completed, the tensile force applying mechanism 8 is lowered to position the sample piece 13 in the inner tank 2 as shown in the figure, and the lid 4 is returned to its original state. Subsequently, the inside of the inner tank 2 is evacuated via the valve 36, and after the exhaust, the inner tank 2 is temporarily filled with helium gas, and then, while the helium gas is evacuated, liquid is filled into the inner tank 2 via the valve 35. A predetermined amount of helium 7 is stored. Next, the inside of the inner tank 2 is again evacuated for a predetermined period of time to remove air bubbles existing in the inner tank 2, and then the pressure is brought to atmospheric pressure.

When the liquid helium 7 is introduced into the inner tank 2 as described above, the wire forming the superconducting coil 6 is cooled to an extremely low temperature and becomes a superconducting wire. In addition, sample piece 1
3 is also cooled to a cryogenic temperature. Next, the superconducting coil 6 is excited by an external power source (not shown). This excitation places the sample piece 13 in a strong magnetic field. Note that, of course, the strength of the magnetic field is detected by a sensor (not shown). Further, at this time, the portion of the notch P is displayed on the receiver 33. This projected image is in focus because the position of the objective lens 24 is set taking into consideration the refractive index of the liquid helium 7 as described above. Also, since no load is applied to the sample piece 13 at this point, the image receiver 3
The image of the notch P shown in is an enlarged image of the actual notch P.
Since the actual dimensions are known, the magnification can be immediately determined. Therefore, from now on, by operating the tensile force applying mechanism 8 and plotting the load signal _S0 at this time and the average value of the spread distance of the cut P projected on the image receiver 33, the cryogenic strength is Fracture toughness tests can be performed in a magnetic field.

In this case, the light guide 21 and the image guide 22 are used to take out the image of the sample piece 13 out of the extremely low temperature strong magnetic field, and it is projected onto the image receiver 33, and the displacement of the sample piece 13 is determined from the projected image. , the displacement can be measured without being affected by extremely low temperatures or strong magnetic fields. Furthermore, since the image of the sample piece 13 transmitted through the image guide 22 is captured by the television camera 31 and displayed on the receiver 33, the magnification can be set freely, and as a result, measurement accuracy can be improved. As a result, the above-mentioned effects can be achieved.

Further, according to this embodiment, since the light source device 27 is equipped with a filter 29 that cuts out infrared rays, it is possible to prevent helium bubbles from being generated at the light transmission end of the light guide 21, and to achieve more accurate can contribute to measurements. In addition, taking into account the refractive index of liquid helium, the image guide 2
Since the second objective lens position is set, the outline of the image of the sample piece 13 projected on the image receiver 33 can be made clearer, and this can further contribute to more accurate measurement. Furthermore, with the magnetic shielding material 34,
Since the television camera 31, camera controller 32, receiver 33, etc. are magnetically shielded,
There is no risk that these will be affected by magnetism, and they can be operated stably.

Note that the present invention is not limited to the embodiments described above. That is, the above-mentioned embodiment is an example in which the present invention is applied to a fracture toughness test device, but
The present invention is not limited to this, but can of course be applied to displacement measurements in general at extremely low temperatures and in strong magnetic fields. Furthermore, a mechanism may be provided that allows the position of the tip of the light guide and the position of the objective lens of the image guide to be adjusted from the outside. Also,
The light guide and the image guide may be integrated. In this case, by setting a certain angle between the optical axis of the transmitter side and the optical axis of the light receiving axis, a clear image can be transmitted.

[Brief explanation of drawings]

The figure is a schematic configuration diagram of an example applied to the fracture toughness testing device of the present invention. DESCRIPTION OF SYMBOLS 1... Cryostat, 6... Superconducting coil, 7... Liquid helium, 8... Tensile force applying mechanism, 13... Sample piece, 21... Light guide, 2
2... Image guide, 27... Light source device, 31
...TV camera, 33...Television receiver.

Claims (1)

[Scope of Claims] 1. Means for positioning a displacement measurement object in liquid helium and applying a strong magnetic field to the displacement measurement object, and a means for placing a displacement measurement object in liquid helium and applying a strong magnetic field to the displacement measurement object; , a light source device that sends out infrared cut illumination light; a light guide that guides the illumination light sent out from the light source device into the cryogenic strong magnetic field and irradiates the object to be measured; and the object to be measured that is displaced. An image guide that transmits a reflected light image from an object to the outside of the cryogenic strong magnetic field, a television camera that photoelectrically converts the image of the displaced object transmitted through the image guide, and the television camera. and a television receiver for projecting an image of the object to be displaced by introducing a video signal sent from the television receiver, and for measuring the displacement of the object to be displaced from the image projected on the television receiver. A displacement measuring device for cryogenic strong magnetic fields, characterized by: 2. The displacement measuring device for a cryogenic strong magnetic field according to claim 1, wherein each of the elements arranged outside the cryogenic strong magnetic field is magnetically shielded. 3. Claim 1, wherein in the image guide, the position of the objective lens is set in relation to the refractive index of the liquid helium.
Displacement measuring device for cryogenic strong magnetic field as described in .