JPH04110690A - Temperature control device of energy dispersion type x-rays detector - Google Patents

Abstract

PURPOSE:To enable temperature of a detector to be maintained to a constant value by providing a cooling control means, a temperature measuring means, a heating means, and a heating control means and then controlling temperature near the detector to a constant value. CONSTITUTION:Control temperature of a cooling control device 8 is set to a specified temperature range for performing interrupted operation of a cooling device 7 automatically, temperature is measured by a thermocouple 9 which is set near a detector 2, and current or voltage is supplied to a heater 11 which turns around a heat-conductive bar 3 so that temperature at the detection part becomes constant. With this configuration, temperature at the detection part is maintained to be constant while the cooling device is at halt, thus enabling fluctuation of noise or drift of spectrum of a semiconductor detection element 2a and its initial stage amplifier to be suppressed and accuracy of X-rays analysis to be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature control device for an energy dispersive X-ray detector.

[Prior art] Figure 4 shows an energy dispersive type X attached to an electron microscope, etc.
The configuration of the line detector is shown.

In Fig. 4, 1 is an electron microscope housing, 2 is a semiconductor X-ray detector, 3 is a heat conduction rod, 4 is a protection tube, 5 is a refrigerant tank (vacuum insulation container), 6 is liquid nitrogen, and 7 is a cooling device. , S is the sample.

Now, in the apparatus configured as described above, the refrigerant tank 5
A semiconductor X-ray detector 2 is attached to the tip of the heat conduction rod 3 via the heat conduction rod 3 due to the latent heat of the liquid nitrogen stored in the
is cooled to liquid nitrogen temperature. When the detector 2 is cooled only by the liquid nitrogen 6, the temperature of the liquid nitrogen is stabilized at the boiling point temperature (approximately 77 K at normal pressure), or consumption of the liquid nitrogen by evaporation cannot be avoided. Therefore, the refrigerant tank 5
A cooling device 7 is inserted into the tank, and the cooling device subcools the liquid nitrogen (to a temperature below its boiling point), thereby suppressing evaporation of the liquid nitrogen and reducing consumption.

However, when the X-ray detector is in use or the electron microscope image is being observed, the vibrations generated by the cooling device deteriorate the resolution of both the X-ray detector and the electron microscope, so the cooling device is stopped during analysis and microscopy. be done.

[Problems to be Solved by the Invention] As described above, when the detector is cooled only with liquid nitrogen without supercooling, consumption due to evaporation of liquid nitrogen cannot be avoided. is stabilized at the boiling point temperature, so the temperature of the detector section is also kept at a substantially constant temperature.

On the other hand, when the liquid nitrogen in the refrigerant tank is supercooled by the cooling device 7 using liquid helium or the like, the temperature of the liquid nitrogen fluctuates due to the inflow of heat from the refrigerant tank and the protective cylinder. In particular, the temperature of the liquid nitrogen rises during the period when the cooling device is stopped during the analysis and microscopy mentioned above, so the temperature of the detector attached to the tip of the heat conduction rod 3 will also fluctuate. Become. This temperature fluctuation causes a fluctuation in the noise of the semiconductor detection element 2a and its first-stage amplifier (FET), and causes spectrum drift, which is considered to be a problem in that it interferes with X-ray analysis.

The present invention takes the above-mentioned problems into consideration and aims to provide a temperature control device for an energy dispersive X-ray detector that can maintain the temperature of the detector at a constant temperature.

[Means for Solving the Problems] The first invention provides a refrigerant tank, a semiconductor X-ray detector connected to the refrigerant tank via a heat conduction rod, and a cooling means inserted into the refrigerant tank. and a cooling control means for intermittent operation of the cooling means so as to maintain the temperature of the refrigerant within a supercooled region, a means for measuring the temperature near the detector, and a means for heating the vicinity of the detector. and a heating control means for controlling the heating means based on the temperature measurement result of the measuring means, so that the temperature near the detector is maintained at a constant temperature by the heating means or the cooling means. It is characterized by the fact that it is controlled by

A second aspect of the present invention includes a refrigerant tank, a semiconductor X-ray detector connected to the refrigerant tank via a heat conduction rod, a cooling means inserted into the refrigerant tank, and a refrigerant in a supercooling region. a cooling control means for intermittent operation of the cooling means to maintain the temperature at a temperature of and a heating control means for controlling the heating means based on the temperature measurement result of the measuring means, the heating means controlling the amplifier to maintain a constant temperature within a supercooling region. It is characterized by what it did.

[Embodiments] Hereinafter, embodiments of the present invention will be described based on the drawings. 1st
The figure is an apparatus configuration diagram for explaining an embodiment of the first invention, FIG. 2 is a diagram for explaining the operation, and FIG. 3 is a diagram for explaining an embodiment of the second invention. It is a device configuration diagram.

In FIG. 1, the same components as in FIG. 4 are given the same numbers and their explanations are omitted. The first embodiment according to the present invention shown in FIG. 1 differs from the conventional example in that a cooling control device 8 for intermittent operation of a cooling device 7 so as to maintain the temperature of the refrigerant 6 within the supercooling region; A thermocouple 9 and a temperature detector 10 for measuring the temperature near the detector, and a heat conductive rod 3
In addition to providing a heater 11 for heating the thermocouple, a heating control means 12 is provided for controlling the heater current or voltage based on the output of the thermocouple.

The cooling control device 8 controls the cooling device 7 based on the temperature of the refrigerant detected by the thermocouple 13 and the temperature detector 14.
Automatically operates intermittently until the temperature of liquid nitrogen reaches 70~75.
It is maintained at any temperature between.

When the cooling device is operated at the same time that liquid nitrogen is injected into the refrigerant tank, the liquid nitrogen in the refrigerant tank is supercooled as shown by the solid line A in FIG. 2(a). This cooling can prevent evaporation by keeping the liquid nitrogen at a temperature below the boiling point 77. Therefore, in this embodiment, the control temperature of the cooling control device 8 is set between 70K and 75K to cool the liquid nitrogen. The device 7 is automatically operated intermittently. Therefore, when the temperature of liquid nitrogen reaches 70K, the cooling control device 8
A control signal as shown in Figure (b) is supplied to the pump of the cooling device 7, and the cooling device 7 is automatically stopped. When the cooling device 7 stops, the temperature of the liquid nitrogen starts to rise gradually, so while measuring the temperature with a thermocouple 9 installed near the detector 2, heat is added so that the temperature of the detection part remains constant. Current or voltage is supplied to the heater 11 which is rotated around the conduction rod 3. At this time, the current or voltage supplied to the heater is changed approximately as shown in FIG. 2(C).

As a result, while the temperature of liquid nitrogen rises to 75K,
The temperature of the detector 2 portion is maintained at a temperature of about 80° C., for example. Then, when the temperature of the liquid nitrogen reaches 75K, the operation of the cooling device is automatically restarted and the liquid nitrogen is cooled again, so that the heater current or voltage is increased to keep the temperature of the detection part constant.

In this way, by keeping the temperature of the detection part constant while the cooling device is stopped, it is possible to suppress noise fluctuations and spectral drifts of the semiconductor detection element 2a and its first stage amplifier (FET). The accuracy of X-ray analysis can be improved.

Now, it is structurally difficult to incorporate the entire X-ray detector, including the refrigerant tank, into the lens barrel used in electron microscopes, etc.
A heat conduction rod 3 is provided between the coolant tank 5 and the detector 2 so that only the X-ray detector portion is placed near the sample inside the lens barrel, and cooling is performed via the heat conduction rod 3. ing. Therefore, heat loss (inflow of heat) in the heat conduction rod portion is unavoidable, and when comparing the temperatures of the refrigerant tank 5 and the detector 2, the temperature on the detector portion side tends to be slightly higher. As described above, when the heater 11 rotated by the heat conduction rod 3 is controlled to keep the temperature of the detector portion constant by supplying current or voltage to the heater 11 while the cooling device 7 is stopped, the heater 11 If it is disposed near the middle of the heat conduction rod 3, the heat flowing into the refrigerant tank 5 through the heat conduction rod 3 will accelerate the temperature rise of the refrigerant. Therefore, the number of times the cooling device 7 is operated increases, resulting in a problem that the analysis time or electron microscope image observation time is restricted.

In addition, when the heater 11 is placed close to the detector section, an amplifier (FET) attached to the semiconductor detection element 2a
Although the temperature of the semiconductor detection element 2a, which is originally desirable to be kept at a low temperature, is kept at a relatively high temperature due to the heat of the heater 11 and the inflow of heat from outside the protective cylinder. .

Therefore, in the second aspect of the present invention, as shown in FIG.
T) A heater lla for heating the amplifier 1.5 is provided adjacent to the amplifier 15.

In this manner, when only the amplifier 15 is heated, the power consumption of the heater 11a can be made extremely small, so that the heat generated by the heating can be prevented from flowing into the refrigerant tank 5 via the heat conduction rod.

This makes it possible to lengthen the stop time of the cooling device 7, that is, the analysis time or the electron microscope image observation time. Furthermore, since only the amplifier 15 is heated with a small amount of electric power, it is possible to prevent the temperature of the semiconductor detection element from rising.

Note that the above-described embodiment is only one embodiment of the present invention, and the present invention can be implemented with various modifications. For example, in the above-described embodiment, when the refrigerant is liquid nitrogen, the cooling device is controlled to maintain the subcooling temperature between 70 and 75, but the temperature setting range is limited to the refrigerant. It is set arbitrarily depending on the type.

[Effects of the Invention] As is clear from the above description, according to the first invention, a refrigerant tank, a semiconductor X-ray detector connected to the refrigerant tank via a heat conductive rod, and a refrigerant tank are provided. and a cooling control means for intermittent operation of the cooling means so as to maintain the refrigerant at a temperature within a supercooled region, and means for measuring the temperature near the detector. , a heating means for heating the vicinity of the detector, and a heating control means for controlling the heating means based on the temperature measurement result of the measuring means, and the heating means or the cooling means heats the vicinity of the detector. By controlling the temperature to maintain a constant temperature, it is possible to suppress fluctuations in the thermal noise of the semiconductor detection element and its first stage amplifier (FET) and drift in the spectrum, improving the accuracy of X-ray analysis. can be done.

Further, according to the second aspect of the present invention, a refrigerant tank, a semiconductor X-ray detector connected to the refrigerant tank via a heat conduction rod, a cooling means inserted in the refrigerant tank, and a A cooling control means is provided for intermittent operation of the cooling means to maintain the temperature within a supercooled region, and a means for measuring the temperature near the detector and heating an amplifier attached to the detector. and a heating control means for controlling the heating means based on the temperature measurement result of the measuring means, and the amplifier is controlled to be kept at a constant temperature by the heating means. As a result, the electric power required for temperature control can be reduced, so that it is possible to suppress the heat generated by heating from flowing into the refrigerant tank portion through the heat conduction rod. This can improve the accuracy of X-ray analysis and lengthen the analysis time and electron microscope image observation time.

[Brief explanation of drawings]

FIG. 1 is an apparatus configuration diagram for explaining an embodiment of the first invention, FIG. 2 is a diagram for explaining the operation, and FIG. 3 is an illustration of an embodiment of the second invention. FIG. 4 is a diagram for explaining a conventional example. Electron microscope housing Heat conduction rod Refrigerant tank Cooling device Thermocouple heater Thermocouple amplifier Sample 4 : 6 : 8 : 10 : 14 : Semiconductor X-ray detector Protection tube Liquid nitrogen cooling control device Temperature detector Heating control means Temperature detector

Claims (2)

[Claims] (1) A refrigerant tank, a semiconductor X-ray detector connected to the refrigerant tank via a heat conduction rod, a cooling means inserted into the refrigerant tank, and maintaining the refrigerant at a temperature within a supercooling region. a cooling control means for intermittent operation of the cooling means, a means for measuring the temperature in the vicinity of the detector, a heating means for heating the vicinity of the detector, and a temperature measurement result of the measuring means. and a heating control means for controlling the heating means based on the above, and the heating means or the cooling means controls the temperature near the detector to be maintained at a constant temperature. Temperature control device for type X-ray detector. (2) A refrigerant tank, a semiconductor X-ray detector connected to the refrigerant tank via a heat conduction rod, a cooling means inserted into the refrigerant tank, and maintaining the refrigerant at a temperature within a supercooling region. a cooling control means for intermittent operation of the cooling means so as to perform the measurement; a means for measuring the temperature near the detector; a heating means for heating an amplifier attached to the detector; and a heating control means for controlling the heating means based on the temperature measurement result of the means, the energy dispersion type Line detector temperature control device.