JPH0377455B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sample heating device for analyzing or observing a sample in vacuum.

Conventional sample heating equipment in vacuum
It was difficult to heat it to around 800℃ to 1000℃, and it was not possible to continuously control the temperature from room temperature to high temperature. In other words, the conventional vacuum sample heating apparatus employs a method in which the sample holder 2 is heated by a heating furnace 8 heated by a heat source, as shown in FIG. 1A or B. The temperature that can be reached is limited by the heat transfer efficiency between the heating furnace 8 and the sample holder 2, and in a vacuum, the heat transfer between the heating furnace and the sample holder is mainly due to thermal radiation. Since the heating process is carried out using a heating furnace, the temperature of the heating furnace must be considerably higher than that of the sample, and the heat resistance of the heating furnace has limited the upper limit of the sample temperature. To explain in more detail, 5 in FIG. 1 is a filament, and a voltage is applied between the heating furnace 8 and the filament 5 to accelerate the electrons emitted from the filament 5. It is heated by radiant heat and the impact of electrons emitted from the filament 5. The sample holder 2 is fitted into the heating furnace 8, but in order to make it replaceable, the fitting is loose, and the contact surface between the sample holder 2 and the heating furnace 8 is slightly uneven, so they are in full contact. Then, it is impossible to say that, in reality, they only touch at a decimal point, and there is a gap between them. Moreover, since it is in a vacuum, the only way for heat to be transferred in this gap is through thermal radiation, and the amount of heat transferred by conduction is very small. The temperature reached by the sample holder is determined by the balance between the amount of heat dissipated by its own thermal radiation and the amount of heat transferred from the heating furnace by the above-mentioned thermal radiation, and is determined by the balance between the total area of the sample holder and the heat transfer area between the heating furnace. ratio
Assuming a ratio of about 10:1 and calculating it using Stephan-Boltzmann's law, the ratio of sample holder 2 to 1000
In order to maintain the temperature at 1,550 °C, the temperature of the heating furnace 8 must be set at about 1550 °C, and the high temperature limit of the sample is determined by the heat resistance of the heating furnace 8, and that temperature is considerably lower than the heat resistance limit temperature of the heating furnace. Conventionally, the temperature of the heating furnace was controlled by changing the electron acceleration voltage applied between the filament 5 and the heating furnace 8. Therefore, even if the electron accelerating voltage is set to 0, the filament 5 remains energized, and the sample holder 2 is kept at 100°C or higher just by the heat generated by the filament 5. Therefore, analysis and measurement at temperatures below 100°C are possible. I couldn't.

The purpose of the present invention is to solve the above-mentioned two problems in the conventional example, namely, that the high temperature limit is limited at a low temperature and that it cannot be used for analysis and measurement in a region around room temperature. That is.

In the sample heating device of the present invention, the sample holder is directly opposed to the filament, and the temperature of the sample holder is controlled by applying an electron acceleration voltage between the filament and the sample holder and adjusting the filament current. It is characterized by
Since the sample holder is heated directly, the sample holder can be heated to the temperatures of the conventional furnaces mentioned above, and the filament current can be adjusted, so lowering the filament current reduces thermionic emission and reduces heating due to electron bombardment. The temperature of the sample holder decreases due to the additive effect of lowering the temperature of the filament, and if the filament current is reduced to 0 as a downward extension of temperature control, electron emission disappears, even if the electron acceleration voltage remains applied. Heating of the sample holder is stopped, and the sample temperature can be continuously controlled from the maximum temperature to room temperature. Furthermore, since no heating furnace is required, the structure is simple and the sample heating device can be provided at low cost.

The present invention will be explained below with reference to Examples. FIG. 2 shows an embodiment of the present invention. A sample 1 is placed on a sample holder 2 . The sample holder 2 is made of stainless steel, for example, and has a cylindrical shape with a hole 22 bored in the center from below. Reference numeral 4 denotes a sample support stand made of stainless steel or the like, and a ceramic tube 3 is fitted and fixed in a through hole in the center. This tube 3
The outer diameter of the sample holder 2 is such that it can be loosely fitted into the hole 22 of the sample holder 2, and is suitable for positioning the sample holder 2 when it is placed on the stand 4 and for adjusting the position between the sample holder 2 and the filament 5. It provides electrical insulation. The filament 5 is inserted into the tube 3, and 6 is a variable voltage power source for heating the filament. Reference numeral 7 denotes a voltage source that heats electrons emitted from the filament 5, which is connected between the filament 5 and the sample support stand 4. The sample temperature is controlled by adjusting the power supply 6.

In the above-mentioned sample heating device, the electron accelerating voltage power supply 7 is used to adjust the sample temperature as well as the filament current adjustment.
You may change the voltage, but the temperature can be adjusted sufficiently without changing the voltage. First, in the low-temperature range up to about 300°C, the filament current is low and the filament is relatively low temperature, so there is very little emission of thermionic electrons, and even if the electron accelerating voltage remains applied, there is almost no heating of the sample holder 2 due to electron impact. Filament 5
The sample holder is heated only by radiant heat from the sample holder. In a high temperature range, the filament temperature rises due to an increase in the filament current, thermionic emission increases, and heating due to electron bombardment becomes active.Furthermore, the thermal radiation of the filament aids in heating, making it possible to control the temperature over a very wide range.

[Brief explanation of drawings]

FIG. 1 is a longitudinal side view of a conventional example, and FIG. 2 is a longitudinal side view of an apparatus according to an embodiment of the present invention. 1...sample, 2...sample holder, 4...sample support stand,
5... Filament, 6... Power source for heating the filament, 7... Voltage power source for electron acceleration.

Claims (1)

[Claims] 1 Place the sample holder and filament facing each other, connect a variable power source for filament current to the filament, and connect a power source for electron acceleration voltage that accelerates electrons emitted from the filament between the sample holder and filament to generate electron impact. A vacuum sample heating device that directly heats the sample holder using the heating action of the filament and radiant heat from the filament, and adjusts the temperature by changing the filament current and the amount of radiant heat and electron emission from the filament. .