JPS5922172B2 - Fragmentation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring thermal diffusivity using a flash method using xenon light, laser pulse light, or other light pulses as an instantaneous heat source.

Originally, the operating principle of this type of device was to maintain an adiabatically held sample (for example, a disk with a diameter of 8 to 10 nm and a thickness of 1 to 3 mm) at a predetermined temperature, and then instantaneously apply a light pulse to the front surface of the sample. The material is irradiated and heated, and the temperature rise on the back surface is detected through a thermocouple welded or bonded to the back surface and recorded on a cathode ray tube oscilloscope, electromagnetic oscilloscope, or other measuring instrument to obtain an appropriate temperature rise curve.

On the other hand, the thermal diffusivity α is “
■1'370-0.139-π is expressed as 1/2.

Here, L is the thickness of the sample -) tV2 is the length of time from the start of irradiation of the light pulse until the temperature on the back surface of the sample reaches the maximum value of 1/2. In this way, it is necessary to accurately determine the starting point of irradiation of a light pulse, that is, = 0. Conventionally, this has been accomplished by using a cathode ray tube switch, which controls the trigger voltage for activating an instantaneous heat source, such as a flash wrap, through a voltage attenuator. It is applied to the trigger input of a scope or other measuring instrument so that the above-mentioned curve appears at the same time as this trigger.In other words, when the trigger pulse is oscillated, =0, but this is not necessarily accurate. That is, the time point at which the trigger pulse is oscillated and the time point at which the light pulse is irradiated onto the sample surface do not exactly coincide, and there is generally a time difference of several hundred microseconds.

This time difference corresponds to an error of 14% when tl/2=36 milliseconds, and when the thermal diffusivity α is even larger, l/2 becomes even shorter, so the error increases further. Furthermore, if the measuring instrument is an electromagnetic oscillograph, it is even more difficult to set =0 because it does not have a mechanism to start recording upon trigger input. The object of the present invention is to obtain a device that reduces such inconveniences as much as possible, and includes an instantaneous heat source that generates a light pulse, and a back surface of a sample that is heated by irradiating the light pulse onto the front surface. A photoelectric conversion circuit comprising a thermoelectric conversion element that detects temperature, a measuring device that expresses the output of the thermoelectric conversion element as a temperature rise curve, and a photoelectric conversion circuit that includes a photoelectric element that converts a part of the optical pulse into an electric pulse. It is characterized in that the electric pulse is set to 0 as the temperature rise curve of the measuring device.

An example of implementing the present invention will be explained with reference to the attached drawings. In the drawing, reference numeral 1 indicates an instantaneous heat source which is a light source of laser pulse light using a ruby rod, and has a sample 2 to be irradiated by this on its front side, and a thermocouple conversion element consisting of a thermocouple 3 on its back side through an amplifier 4. and is connected to input terminals 6, 6 of a measuring instrument 5 consisting of a flow tube oscilloscope. In the drawing, T indicates a trigger input terminal in the measuring device 5. Although the above is not particularly different from the conventional one, according to the present invention, a part of the light pulse irradiated from the heat source 1 to the sample 2 is used. A translucent mirror 9 made of A photoelectric conversion circuit 11 is connected to the element 10 on its output side.
It is connected to the above-mentioned trigger input terminal 7 via.

The photoelectric conversion circuit 11 includes, for example, an IC amplifier 12, a 6-clipper circuit 13, and a one-shot multipipulator circuit 14.
and a line driver circuit 15.The electrical signal obtained at the output side of the photoelectric element 10 is amplified and shaped, and is applied as a trigger input pulse to the measuring instrument 5, where t=O is set. I made it so that it would be done. In the drawing, 16 is a temperature rise curve obtained by the measuring device 5. To explain its operation, when six optical pulses are irradiated, a part of the pulses simultaneously enters the photoelectric element 10 and is converted into an electrical signal, which is then passed through the photoelectric conversion circuit 11 to the trigger input terminal of the measuring instrument 5. 7, thus setting t=0 to it. Considering the time difference in this case, conversion in the 6 photoelectric elements 10 takes about 50 microseconds, and then the photoelectric conversion circuit 11
In this case, the time difference is within about 1 microsecond, and the time difference throughout is about 50 microseconds, which is about 1/10 of the conventional method described above. In this way, according to the present invention, a part of the light pulse irradiated to the sample is used to generate an electric pulse, and this sets t=o in the measuring instrument, compared to the conventional method described above. This has the effect of significantly reducing time differences and significantly improving measurement accuracy.

[Brief explanation of the drawing]

The drawing is a diagram of an example of the device of the present invention. 1... Instantaneous heat source. 2...Sample 610.
...Photoelectric element, 11...Photoelectric conversion circuit.

Claims (1)

[Claims] 1. An instantaneous heat source that generates a light pulse, a thermoelectric conversion element that detects the temperature of the back side of the sample that is heated by irradiating the light pulse on the front side, and a measuring device that expresses the output of the thermoelectric conversion element as a temperature rise curve. and a photoelectric conversion circuit including a photoelectric element that converts a part of the optical pulse into an electric pulse, and the electric pulse is used as a setting input at t=0 of the temperature rise curve of the measuring instrument. Flash method thermal diffusivity measuring device.