JP2007003397A - Sample analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample analyzer capable of making compatible both reduction of an influence by vibration and enhancement of cooling performance, by switching an operation of a refrigerator main body in response to an analytical content. <P>SOLUTION: This sample analyzer 1000 is provided with an operation condition detection control part 7 for detecting an operation condition where either of an electron microscope 20 or an EDS detector 10 is operated, and for outputting an operation switching signal to the refrigerator main body 1a; and a driving electric power source part 6 for controlling driving of the refrigerator main body 1a, based on the operation switching signal. An analytical operation is carried out by elevating a temperature up to an allowable upper limit temperature of an X-ray detecting element when the electron microscope 20 is operated, and by making the temperature low to an operation temperature of the X-ray detecting element when the EDS detector 10 is operated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sample analyzer for eliminating the influence of mechanical vibration.

  The pulse tube refrigerator has a function of generating cold and is applied to various devices. As an example of the application of such a pulse tube refrigerator, an energy dispersive semiconductor X-ray detector using an EDS (Energy Dispersive X-ray Fluorescence Spectrometer: sometimes abbreviated as EDX). Application of (EDS detector) to a cooling system is being studied. For example, Patent Document 1 discloses a conventional technique of an energy dispersive semiconductor X-ray detector using such a pulse tube refrigerator.

  A conventional EDS detector and an energy dispersive semiconductor X-ray detector (hereinafter simply referred to as a sample analyzer) on which the EDS detector is mounted will be described with reference to the drawings. FIG. 6 is an explanatory diagram of a sample analyzer equipped with a conventional EDS detector, and FIG. 7 is an explanatory diagram of the EDS detector. A sample analyzer 1000 ′ shown in FIG. 6 includes an EDS detector 10 ′, an electron microscope 20, a sample chamber 30, a main body 40, a connecting pipe 50, a vibration isolation stand 60, a weight 70, a pressure conversion valve unit 80, a compressor 90, a high pressure. A helium pipe 100, a low-pressure helium pipe 110, and a controller 120 are provided.

Next, the configuration of each part will be described.
As shown in FIG. 7, the EDS detector 10 ′ further includes a cryostat 11, a small gas circulation refrigerator 12, a cold finger 13, an X-ray detection element unit 14, and a moving unit 15.

  The cryostat 11 further includes a main body portion 11a, a cylindrical portion 11b, and an X-ray window 11c. A horizontal cylindrical portion 11b is connected to the main body portion 11a, which is an L-shaped cylinder, and an X-ray window 11c is provided in the cylindrical portion 11b. The X-ray window 11c has a strength capable of maintaining a vacuum and has a function of transmitting characteristic X-rays emitted from the sample. The inside of the cryostat 11 is shut off from the outside air during use and is kept in a vacuum by a vacuum pump (not shown).

  The small gas circulation refrigerator 12 further includes a refrigeration unit main body 12a and a cooling / heating unit 12b. A refrigeration unit main body 12a is provided at the upper end of the main body 11a of the cryostat 11, and the refrigeration unit main body 12a has a cooling / heating unit 12b. It extends inside the cryostat 11. The small gas circulation refrigerator 12 is, for example, a GM (Gifford-McMahon cycle) type pulse tube refrigerator in which a compressor and an expander are separated. In this case, the refrigeration unit main body 12a is an expander, and helium gas is supplied to the refrigeration unit main body 12a from a compressor 90 (see FIG. 6) which is a compressor via a connecting pipe 50. A structure for supplying helium gas to the small gas circulation refrigerator 12 will be described later.

  As shown in FIG. 7, the cold finger 13 is formed, for example, in a substantially L shape by using a material having excellent thermal conductivity such as copper. The cold finger 13 is provided in a space that extends over the main body portion 11a of the cryostat 11 and the horizontal cylindrical portion 11b that is connected to the main body portion 11a. One end side of the cold finger 13 is thermally coupled to the cooling unit 12 b of the small gas circulation refrigerator 12.

  The X-ray detection element unit 14 further includes an X-ray detection element 14a and a temperature sensor 14b. The X-ray detection element 14a has a function of detecting characteristic X-rays emitted from the sample and outputting them as detection signals to a detection signal processing unit (not shown). An X-ray window 11c for transmitting characteristic X-rays is located in front of the X-ray detection element 14a. The temperature sensor 14b has a function of detecting the temperature of the X-ray detection element 14a and outputting it as a temperature signal to the controller 120 (see FIG. 6). Such an X-ray detection element unit 14 is provided in a state of being thermally coupled to the tip side of the cold finger 13.

The moving part 15 further includes a guide base 15a, guide parts 15b and 15c, a guide rod 15d, an actuator 15e, and a guided part 15f.
As shown in FIG. 6, the guide base 15 a extends in the direction of the electron microscope 20 and is attached to an attachment portion that protrudes from the body portion of the electron microscope 20. The guide portions 15b and 15c are fixed to the guide base 15a.
The guide rod 15d is slidably inserted in the bearing portions in the guide portions 15b and 15c.
Actuator 15e drives guide rod 15d to move in the direction of arrow F (forward direction) or in the direction of arrow R (reverse direction).
The guided portion 15f is fixedly attached to the main body portion 11a of the cryostat 11 and the guide rod 15d. As a result, the EDS detector 10 ′ moves together with the guided portion 15f, and moves the EDS detector 10 ′ in the direction of arrow F (forward direction) or in the direction of arrow R (reverse direction) in accordance with the movement of the guide rod 15d. Move to slide.
As shown in FIG. 6, the controller 120 is placed on the upper surface of the main body 40 and controls cooling of the EDS detector 10 ′ (X-ray detection element 14 a) and its movement forward or backward.
The EDS detector 10 'is like this.

Returning to FIG. 6, the electron microscope 20 is specifically a scanning electron microscope (SEM).
The sample chamber 30 is a partition space for placing a sample. In the sample chamber 30, in order to prevent the operator from being adversely affected by the electron beam and the characteristic X-ray, and to reliably detect the secondary electrons, the reflected electrons, and the characteristic X-ray, the external environment and the internal space are separated. It is designed to ensure isolation.
The main body 40 is made of a mechanically high-rigidity material in order to be strong against vibration. Further, although not shown, necessary devices such as a power supply unit are accommodated after taking a vibration-proof measure.

  The connecting pipe 50 further includes a main body portion 51 and a flexible portion 52. The main body portion 51 is connected to the pressure conversion valve unit 80, and the flexible portion 52 is connected to the refrigeration unit main body 12a. The connecting pipe 50 secures a flow path between the pressure conversion valve unit 80 and the refrigeration unit main body 12a, and supplies helium gas adjusted to a predetermined pressure to the refrigeration unit main body 12a. The reason why the flexible portion 52 is employed here is the configuration for the EDS detector 10 'to cope with movement in the direction of arrow F or arrow R as shown in FIGS.

  The anti-vibration stand 60 is erected in the vicinity of the main body 40, and the main body portion 51 of the connecting pipe 50 is fixedly held by the fixing portion 62 along the vertical direction of the rod-shaped stand main body 61. Furthermore, a plurality of weights 70 (for example, two in FIG. 6) for suppressing vibration are attached to the flexible portion 52 of the connecting pipe 50.

  The pressure conversion valve unit 80, the compressor 90, the high pressure helium pipe 100, and the low pressure helium pipe 110 are helium gas supply systems to the small gas circulation refrigerator 12, and the pressure conversion valve unit 80 and the compressor 90 are the high pressure helium pipe 100 and The low pressure helium pipe 110 is connected.

  Next, the operation during analysis will be described. A sample is placed on a sample stage (not shown) in the sample chamber 30 of the sample analyzer 1000 ′ shown in FIG. 6, and after the door is closed and isolated from the outside, analysis is started from an operation unit (not shown) of the controller 120. The actuator 15e is driven so as to move the EDS detector 10 ′ (X-ray detection element 14a) in the direction of arrow F (forward direction). Then, the EDS detector 10 'moves in the arrow direction F (forward direction) to bring the X-ray detection element 14a closer to the sample.

  Subsequently, when analysis is started, an electron beam is output from the electron gun of the scanning microscope 20, and secondary electrons and reflected electrons are emitted from the sample. Secondary electrons are pulled to a positive potential of 10 KV (acceleration voltage normally used for SEM observation) applied to the detector, and reflected electrons are their own energy, both of which are phosphor screens applied to the detector surface. And is converted into light, the light is amplified by a photomultiplier tube (PMT), and an image signal is generated and output by an image signal processing unit. This image signal is output to a display unit such as a CRT for observation and photographing.

At the same time or at different times, the EDS detector 10 ′ performs elemental analysis of a minute portion on the sample surface. The controller 120 inputs a temperature signal from the temperature sensor 14b described above, and controls the temperature of the small gas circulation refrigerator 12 so as to maintain a predetermined temperature. The X-ray detection element 14a maintains a predetermined temperature. Under such circumstances, when the electron beam from the electron gun of the scanning microscope 20 hits the sample, characteristic X-rays also jump out of the sample. This characteristic X-ray has its own wavelength depending on the type of element. The X-ray detection element 14a detects such characteristic X-rays and outputs them to the detection signal processing unit. The detection signal processing unit is, for example, a computer, detects an element contained in a sample from the detection signal, and displays, for example, a spectrum distribution. Moreover, quantitative analysis is also possible by measuring the intensity of each energy and comparing it with the standard intensity.
At the end of the analysis, the actuator 15e is driven so that the EDS detector 10 '(X-ray detection element 14a) is automatically moved in the direction of arrow R (retreat direction).
The sample analyzer 1000 ′ is like this.

  As a feature of this sample analyzer, particularly in the EDS detector 10 ′, the main body portion 51 of the connecting pipe 50 for supplying the pressure-adjusted helium gas to the freezer main body 12 a of the small gas circulation refrigerator 12 is prevented. While being fixed to the stand main body 61 of the shaking stand 60 and the vibration-proof weight 70 is provided at the flexible portion 52 at the tip thereof, the vibration of the connecting tube 50 is suppressed. Therefore, even if the pressure-adjusted helium gas flows in the connecting pipe 50, the vibration of the connecting pipe 50 is suppressed, and the vibration is not transmitted to the EDS detector 10 ′, the electron microscope 20, etc.・ Image acquisition is performed.

  As a similar conventional technique, for example, the invention described in Patent Document 2 is known.

Japanese Patent Laid-Open No. 10-311877 (paragraph numbers 0011 to 0022, FIGS. 1 and 2) Japanese Utility Model Publication No. 5-17584 (paragraph numbers 0009 to 0017, FIG. 1)

  As described above, in Patent Document 1, the GM (Gifford-McMahon cycle) type small gas circulation refrigerator 12 in which the compressor and the expander are separated is adopted, and the expander (refrigeration unit main body 12a and cooling unit). 12b) is mounted on the sample analyzer 1000 ', and the compressor (pressure conversion valve unit 80, compressor 90, high-pressure helium pipe 100, helium gas supply system using the low-pressure helium pipe 110) is arranged beside the sample analyzer 1000'. Then, helium gas which is a working gas is supplied through the connecting pipe 50, and the X-ray detection element 14a is cooled by the expansion work of the expander.

  Here, the compressor 90 of the GM small gas circulation refrigerator 12 is a low-cost compressor that generates large vibrations, such as a reciprocating compressor using an induction motor or a scroll compressor. Further, the pressure conversion valve unit 80 uses a rotary motor type or a solenoid valve type, and is switched at an operating frequency close to the resonance frequency (2 to 4 Hz) of a vibration isolation mechanism (not shown) of the electron microscope 20. Generates vibrations close to the resonance frequency. When these vibrations are transmitted to the electron microscope 20, even a slight generated vibration adversely affects the image of the electron microscope 20 that is several tens of thousands of times. It is also affected by X-ray detection.

  Therefore, in order to prevent the vibration of the compressor 90 and the pressure conversion valve unit 80 from being transmitted, in the apparatus of Patent Document 1, the flexible portion 52 of the connecting pipe 50 is interposed as described above, so that the compressor 90 and the pressure conversion valve unit are interposed. The vibration generated at 80 is cut off. Further, the vibration 70 is adjusted to change the natural frequency by adjusting the weight 70 so as to prevent resonance and reduce the generated vibration.

However, such a connecting pipe 50 must also be composed of a relatively rigid metal flexible pipe in order to withstand the pressure (several MPa) of the working gas of the small gas circulation refrigerator 12 of the GM system. It becomes a vibration generating source having a frequency of several Hz to 10 Hz. In order to reduce the vibration of the connecting pipe 50, it is necessary to increase the mass and increase the rigidity, and the apparatus is heavy and large. In addition, since the natural frequency varies depending on the mounting length and direction, there is a limit to reducing the generated force and displacement.
Such a problem is the same in the apparatus described in Patent Document 2.
As described above, in Patent Documents 1 and 2, in order to increase the detection accuracy, a large structure / heavy object structure cannot be avoided, and the entire apparatus vibrates due to vibration that cannot be removed if it is downsized. There was a risk of adverse effects such as X-ray detection.

Although not shown in the figure, when a method of cooling with liquid nitrogen instead of a refrigerator is used, it seems that vibration does not occur, but bubbling that occurs randomly for a certain period of time from liquid nitrogen injection until boiling stops. Due to (bubble generation), the image of the electron microscope may be similarly adversely affected during this period. In addition, the liquid nitrogen method needs to be replenished about twice a week, and there is a problem that the running cost such as liquid nitrogen consumption cost, storage cost and labor cost becomes high.
Thus, in the prior art, there is a problem that vibration generated during cooling adversely affects the sample analyzer. In addition, a large configuration as in the prior art is adopted to suppress this vibration, and there is a problem that miniaturization is difficult.

A method of driving the pulse tube refrigerator only when the EDS detector 10 ′ is operating is also conceivable. However, since it is difficult to immediately operate the pulse tube refrigerator, the EDS detector 10 ′ is operated. There was a problem that it took time to do.
In addition, complete countermeasures such as reducing the unbalance of the moving mass of the linear motor of the opposed compressor of the refrigerator, ensuring the rectilinear movement of the piston reciprocating movement, and controlling the motive force of the piston's amplitude and phase are used to reduce the generated vibration. Although it may be possible to eliminate the influence of the generated vibration by bringing it to “zero” as much as possible, the cost becomes high.

  Therefore, the present invention has been made in view of the above-described problems, and its purpose is to switch the operation of the refrigerator main body according to the analysis contents to achieve both reduction of the influence of vibration and improvement of cooling performance. An object of the present invention is to provide a sample analyzer.

In order to solve the above problem, a sample analyzer of the invention according to claim 1 of the present invention provides:
An electron microscope that obtains an image signal from the emitted electrons by irradiating the sample with an electron beam;
An EDS detector for analyzing a sample from characteristic X-rays emitted by irradiating the sample with an electron beam;
A refrigerating machine main body having a vibration type compressor having a pair of pistons opposed to each other and cooling an X-ray detection element of an EDS detector;
An operation state detection control unit that detects an operation state of whether an electron microscope or an EDS detector is operated and outputs an operation switching signal;
A drive power supply unit for controlling the drive of the refrigerator based on the operation switching signal;
With
During the operation of the electron microscope, the temperature is increased to an allowable upper limit temperature of the X-ray detection element, and the pre-cooling operation is performed. When the EDS detector is operated, the temperature is decreased to the operation temperature of the X-ray detection element and the main operation is performed.

Further, the sample analyzer of the invention according to claim 2 of the present invention provides:
The sample analyzer according to claim 1,
The refrigerator main body is
A linear motor including a piston and a drive unit that reciprocates the piston, and a cylinder in which the linear motor is housed, and the piston is reciprocated inside the cylinder to define a compression space. An oscillating compressor that periodically compresses the fluid inside;
An expander coupled to the vibratory compressor;
A phase control unit coupled to the expander;
It is characterized by providing.

Moreover, the sample analyzer of the invention according to claim 3 of the present invention provides:
The sample analyzer according to claim 2,
The refrigerator main body is
A connecting pipe connected between the vibration type compressor and the expander is provided.

Moreover, the sample analyzer of the invention according to claim 4 of the present invention provides:
The sample analyzer according to claim 3,
The connecting pipe includes a string-like spring-like portion,
The piston drive direction of the vibration type compressor and the central axis direction of the spring-like portion are arranged substantially in parallel.

  According to the present invention as described above, it is possible to provide a sample analyzer that switches the operation of the refrigerator main body in accordance with the analysis contents and reduces the influence on the generated vibration.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a sample analyzer. 2 is an explanatory diagram of an EDS detector, FIG. 3 is an explanatory diagram of a pulse tube refrigerator, FIG. 4 is a circuit block diagram of a sample analysis circuit, FIG. 4A is a circuit block diagram of an electron microscope, and FIG. (B) is a circuit block diagram of an EDS detector.

The sample analyzer 1000 of this embodiment as shown in FIG. 1 is different from the sample analyzer 1000 ′ described with reference to FIGS. 6 and 7 in that a vibration isolation mechanism 130 is provided between the sample chamber 30 and the main body 40. The point which intervened and the point which employ | adopted the EDS detector 10 which improved the structure differ.
Hereinafter, the differences will be described with emphasis, and other configurations will be denoted by the same reference numerals as those of the prior art described with reference to FIGS. 6 and 7, and redundant description thereof will be omitted.

As shown in FIG. 2, the EDS detector 10 includes a cryostat 11, a pulse tube refrigerator 1 (a refrigerator main body 1 a, a drive power supply unit 6, an operation state detection control unit 7), a cold finger 13, and an X-ray detection element unit 14. The moving unit 15 is provided. Here, the temperature sensor 14b of the X-ray detection element unit 14 is connected to the operating state detection control unit 7 via the hermetic terminal 16, as shown in FIG. Instead of using the hermetic terminal 16, although not shown, the operating state detection control unit 7 and the temperature sensor 14b may be connected via the controller 120 as in the prior art.
Thus, instead of the EDS detector 10 ′ using the GM-type small gas circulation type refrigerator 12 of the prior art, the EDS detector 10 of the present embodiment includes a pulse tube refrigerator 1 equipped with the vibration type compressor 2. The point of use is different. The components other than the pulse tube refrigerator 1 in the EDS detector 10 are the same as those in the prior art described with reference to FIGS.

The pulse tube refrigerator 1 will be described.
2 and 3, the pulse tube refrigerator 1 includes a vibration type compressor 2, a connecting pipe 3, an expander 4, a phase control unit 5, a drive power supply unit 6, and an operation state detection control unit 7. It can be divided into a refrigerating machine main body 1a composed of a refrigeration circuit type vibration compressor 2, a connecting pipe 3, an expander 4, and a phase control unit 5, a power source drive power source unit 6, and an operating state detection control unit 7.

Specifically, the vibration type compressor 2 includes a linear motor including a piston 2a and a drive unit (not shown) that reciprocates the piston 2a, and a cylinder 2b in which the linear motor is accommodated. A pair of pistons 2a face each other in the cylinder 2b.
The connecting pipe 3 is interposed between the vibration type compressor 2 and the expander 4. In this embodiment, since the vibration type compressor 2 and the expander 4 are in close contact with each other, they are formed short.
Specifically, the expander 4 includes a heat exchanger 4a, a regenerator 4b, a cooling end 4c, and a pulse tube 4d.
Specifically, the phase control unit 5 includes an inertance tube 5a and a buffer tank 5b.
The refrigeration circuit system is formed by the vibration type compressor 2, the connecting pipe 3, the expander 4, and the phase controller 5 as described above. For example, helium gas is sealed as working gas (refrigerant gas) in the flow path.

The drive power supply unit 6 receives commercial power and generates and supplies AC drive power driven by the vibration compressor 2.
The operation state detection control unit 7 detects an operation state indicating which of the electron microscope and the EDS detector is operated and outputs an operation switching signal. In such an operation state detection, for example, a switch for operating the electron microscope 20 and a switch for operating the EDS detector 10 are connected to the operation state detection control unit 7, and the electron microscope 20 is operated. When the switch to be operated is turned on, it can be detected that the electron microscope 20 is in an operating state, and when the switch for operating the EDS detector 10 is turned on, it can be detected that the EDS detector 10 is in an operating state. .
By this control, the drive power supply unit 6 receives the operation switching signal output from the operation state detection control unit 7 and outputs AC driving power having a frequency, and the vibration type compressor 2 vibrates the piston 2a. As will be described later, a pre-cooling operation for increasing the temperature to the allowable upper limit temperature of the X-ray detection element is performed during operation of the electron microscope, and a main operation for decreasing the temperature to the operation temperature of the X-ray detection element is performed during operation of the EDS detector.

  Next, the operation principle of the pulse tube refrigerator 1 will be described. As shown in FIG. 3, when driving the pulse tube refrigerator 1, the drive power supply unit 6 reciprocates the piston 2 a in the cylinder 2 b of the vibration compressor 2 when supplying AC drive power with a predetermined drive frequency. As a result, the working gas in the cylinder 2b is compressed and expanded. Such working gas reaches the connecting pipe 3, the heat exchanger 4a, the regenerator 4b, the cooling end 4c, the pulse tube 4d, the heat exchanger 4a, the inertance tube 5a, and the buffer tank 5b from the vibration type compressor 2. The working gas flows as a reciprocating flow in a series of systems between the vibration compressor 2 and the phase controller 5.

  Here, the working gas flows in the inertance tube 5a and the buffer tank 5b of the phase control unit 5 with a pressure amplitude substantially sinusoidally, thereby causing a phase difference between the pressure change and the flow rate change. Can be generated. When these refrigeration circuits are compared with electric circuits, the inertance tube 5a corresponds to an inductance component and a resistance component, and the buffer tank 5b corresponds to a capacitance component. Such a phase control unit 5 can change the phase difference of the flow rate with respect to the pressure of the working gas from −90 ° to + 90 °.

  As described above, when the pulse tube refrigerator 1 is operated, a phase difference is generated between the pressure and the flow rate of the working gas in the pulse tube 4d due to the phase control effect by the pulse tube 4d and the phase control unit 5, and the pressure and the flow rate. The work that is made becomes PV work at the cooling end 4c, and cold is generated at the cooling end 4c. This generated cold is called low-temperature PV work.

  Here, the cooling end 4c is interposed between the regenerator 4b and the pulse tube 4d as described above. During operation of the pulse tube refrigerator 1, the working gas sent out in the compression process of the vibration type compressor 2 becomes a low temperature in the regenerator 4b, flows into the pulse tube 4d, and adiabatically expands inside the pulse tube 4d. As a result, heat is absorbed at the cooling end 4 c, and the working gas flows out to the phase controller 5. Contrary to the above, in the process in which the working gas passes from the phase control unit 5 through the pulse tube 4d and recirculates to the cooling end 4c, heat is not generated or absorbed because it changes with a substantially constant volume. That is, there is no heat generation at the cooling end 4c, only heat absorption is performed, and cold is generated. Due to this cooling, the X-ray detection element 14a is cooled via the cold finger 13 (see FIG. 2).

Next, the operation of the sample analyzer 1000 will be described in detail particularly from the viewpoint of vibration suppression.
When the main power of the sample analyzer 1000 is turned on, the pulse tube refrigerator 1 is operated. The pulse tube refrigerator 1 cools the X-ray detection element 14a of the EDS detector 10 in particular. In addition, since neither the electron microscope 20 nor the EDS detector 10 is operating at the beginning of the operation, a pre-cooling operation is performed.

  At this time, since AC driving power having a predetermined frequency is supplied and the piston 2 a is reciprocating, mechanical vibration having a predetermined frequency is transmitted to the sample chamber 30 and the electron microscope 20. This mechanical vibration is generated vibration due to an imbalance between the linear motor of the vibration type compressor 2 and the piston amplitude, mass, and phase. Such a situation seems less desirable than the prior art, but it is not. Mechanically, since it deviates from the resonance frequency (2 to 4 Hz) of the vibration isolation mechanism 130 of the electron microscope 20, this vibration is suppressed by the vibration isolation mechanism 130 without causing mechanical resonance, and the electron microscope 20 and Mechanical vibrations to the EDS detector 10 can be prevented from occurring. In this embodiment, it is operated at such a frequency.

Subsequently, the analysis is started. First, it is assumed that the electron microscope 20 is operated. The operation state detection control unit 7 outputs an operation switching signal that detects an operation state that the electron microscope 20 is operated and causes the drive power supply unit 6 to perform a pre-cooling operation. Since the pre-cooling operation has already been performed at the beginning of operation, the pre-cooling operation is continued as it is even when the operation switching signal is received.
Here, when the electron microscope 20 is used for microscopic observation at a high magnification, the EDS detector 10 is not used, that is, the X-ray detection element 14a that needs to be cooled is not used. Prioritizing the suppression, the temperature is increased to an allowable upper limit temperature at which the X-ray detection element 14a does not deteriorate, and the pre-cooling operation is performed. In this pre-cooling operation, the amount of movement of the piston 2a is reduced (the operation amplitude is reduced), and the temperature of the fluid in the compression space is increased to the allowable upper limit temperature by reducing the compression amount, that is, reducing the cooling capacity. The operating state detection control unit 7 registers the allowable upper limit temperature in advance, and performs the pre-cooling operation while controlling the drive power supply unit 6 so as not to exceed the allowable upper limit temperature based on the temperature signal output from the temperature sensor 14b. Do.
In this way, when the electron microscope 20 is used, vibration of the vibration compressor 2 is suppressed and a clear image can be obtained.

Under such circumstances, in the signal processing unit of the electron microscope 20, as shown in FIG. 4A, when the electron beam is irradiated from the electron gun unit 21, it reaches the scanning coil 23 via the focusing lens 22, The trajectory is changed by the magnetic field or electric field in the scanning coil 23, and the electron beam can be converged to one point by the objective lens / aperture 24. A scanning control unit 25 is connected to the scanning coil 23 and performs deflection control of the scanning coil 23 to scan the sample surface in two directions of X and Y. Further, secondary electrons and reflected electrons are emitted from the sample irradiated with the electron beam. The detection unit 27 detects these electrons and outputs a detection signal. The image signal processing unit 28 to which the detection signal is input performs image signal processing using the detection signal.
The scanning control unit 25 is also connected to a CRT display unit 26, and the CRT display unit 26 performs display using the image signal from the image signal processing unit 28 in correspondence with the scanning position.

  The present inventor conducts an experiment for verification, and in the electron microscope 20 of the sample analyzer 1000 in the precooling operation as in this embodiment, even when the liquid nitrogen cooling is stable (with no bubbling) even at a magnification of 100,000 times. It was confirmed that there was no difference between the case and the image.

Subsequently, the EDS detector 10 is operated. The operation state detection control unit 7 detects an operation state that the EDS detector 10 is being operated, and outputs an operation switching signal that causes the drive power supply unit 6 to perform the main operation. The drive control unit 6 switches from the pre-cooling operation to the main operation. In this case, since an X-ray detection element that needs to be cooled is used, during the operation of the EDS detector 10, the temperature is lowered to the operation temperature of the X-ray detection element 14a and the main operation is performed. In general, when analysis is performed using the EDS detector 10, focusing is performed at a low magnification, so even if some generated vibrations occur, the measurement of the EDS detector 10 is not affected. Therefore, in this actual operation, the amount of movement of the piston 2a is increased (the operation amplitude is increased), and the temperature of the fluid in the compression space is increased to the operating temperature by increasing the amount of compression, that is, increasing the cooling capacity. The operation state detection control unit 7 registers the operation temperature in advance, and performs the main operation while controlling the drive power supply unit 6 so as to maintain the operation temperature based on the temperature signal output from the temperature sensor 14b.
In this way, when the EDS detector 10 is used, even if the vibration type compressor 2 vibrates, the detection is not affected, so that the X-ray detection element 14a can be sufficiently cooled to perform highly accurate detection. And

  Also in the EDS detector 10, as shown in FIG. 4B, when the electron beam is irradiated from the electron gun unit 21 of the electron microscope 20 toward the sample, characteristic X-rays are emitted from the sample. The X-ray detection element 14a (see FIG. 2) detects characteristic X-rays and outputs an X-ray detection signal. The detection signal processing unit 17 to which such an X-ray detection signal is input performs spectrum analysis processing using the X-ray detection signal.

  The present embodiment has been described above. In this embodiment, the operation state of whether the electron microscope or the EDS detector is operated is detected, and an operation switching signal is output to the drive power supply unit 6. When the electron microscope is used, the vibration type compressor of the pulse tube refrigerator 1 is used. The drive current of the linear motor 2 is reduced to reduce the amount of amplitude to lower the refrigeration capacity and to reduce the generated vibration. When the EDS detector is used, the vibration compressor 2 of the pulse tube refrigerator 1 is used. The drive current of the linear motor was increased to increase the amount of amplitude to increase the refrigeration capacity so that it could be changed according to circumstances. With such two-stage operation control, when the electron microscope is operating, the EDS detector 10 can be pre-cooled under operating conditions that do not affect the image observation, and when the operation is switched from the electron microscope 20 to the EDS detector 10. However, the necessary sensor temperature can be obtained immediately when detecting EDS in the shortest time, and the EDS detector 10 can be used. In this way, the influence of the generated vibration of the refrigerator main body 1a that cools the EDS detector 10 on the observation of the electron microscope 20 can be minimized.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 5 is an explanatory view of another type of sample analyzer. In this embodiment, the structure of the pulse tube refrigerator 1 is different from that of the sample analyzer described above, and the pulse tube refrigerator shown in FIG. The expander 4 and the phase control unit 5 are integrally formed, but the present embodiment is different in that the connection pipe 3 is lengthened and the mechanical vibration is not transmitted because the vibration type compressor 2 is disposed elsewhere. To do.
Hereinafter, the differences will be described with emphasis, and other configurations will be denoted by the same reference numerals as those of the previous embodiment and the prior art described with reference to FIGS. Description is omitted.

As shown in FIG. 5, the vibration type compressor 2 is disposed on the main body 40. Although not shown, an anti-vibration mechanism (not shown) may be disposed between the main body 40 and the vibration type compressor 2 so that mechanical vibration from the vibration type compressor 2 is not transmitted to the main body 40.
As shown in the figure, the connecting pipe 3 is formed with a string-like spring-like portion 3a, and connects a pipe extending perpendicularly to the vibration direction from the vibration compressor 2 and a pipe extending from the expander in the vibration direction. ing. In this way, the spring-like portion 3a changes the direction of the connecting pipe 3 (changes by 90 degrees in the figure) and also has a function of absorbing vibration in the direction of arrow A, that is, in the mechanical vibration direction. The spring-like portion 3a can change its spring constant by changing its diameter, and can also be used to adjust the frequency so as to avoid the resonance frequency of the vibration isolation mechanism 140.

  In such a sample analyzer 2000, the vibration obtained in the previous embodiment can be obtained by interposing the connecting tube 3 that separates the vibration type compressor 2 and the expander 4 of the pulse tube refrigerator 1 and is vibration-insulated. In addition to the effect of eliminating the influence of, the electron microscope 20 can further reduce the influence of mechanical vibration from the vibration type compressor 2. Further, since the vibration type compressor 2 is provided separately, the EDS detector 10 can be reduced in size, and the expander 4 can be installed in the vicinity of the X-ray detection element 14a. Thus, the X-ray detection element 14a can be cooled.

  In the above, each form was demonstrated. In this embodiment, the operation state detection control unit 7 detects switching on and switches to automatic operation. However, the operation state detection control unit 7 is equipped with a changeover switch (not shown) to manually perform the precooling operation and the main operation. May be switched.

  As described above, according to the present invention, at the time of microscopic observation that requires low vibration, the amplitude of the compressor of the refrigerator is reduced to reduce the refrigerating capacity, and the sensor temperature is increased to the allowable temperature of the sensor by, for example, 10K. During EDX observation where the vibration level is allowed to some extent, the refrigerator is operated so that the X-ray sensor is cooled to a predetermined temperature in a short time. As described above, a refrigerator cooling system with good cost performance can be provided by operating the generated vibration level of the refrigerator so as to match the level required by the electron microscope and EDX.

  Moreover, according to this invention, the refrigerator operation according to each allowable vibration state at the time of microscope use and EDX use can be performed, and the system which operates the refrigerator with a good balance of cost and generated vibration can be provided. .

  In addition, when a GM refrigerator is used for cooling, it can be controlled only by turning the refrigerator on and off due to restrictions on the configuration principle, but the operation control of this pulse tube refrigerator that can control the operation of the refrigerator stepwise. In the method, even if it is not the main operation, the pre-cooling operation can minimize the increase in the sensor temperature of the EDX, so that it is possible to construct a system with good responsiveness.

In addition, it is possible to eliminate the waiting time for stabilization after replenishment of liquid nitrogen that has been caused by cooling of liquid nitrogen and the influence of bubbling that occurs randomly. Furthermore, since the supply of liquid nitrogen and the supply work can be eliminated, the running cost can be reduced.

It is explanatory drawing of a sample analyzer. It is explanatory drawing of an EDS detector. It is explanatory drawing of a pulse tube refrigerator. FIG. 4A is a circuit block diagram of an electron microscope, and FIG. 4B is a circuit block diagram of an EDS detector. It is explanatory drawing of the sample analyzer of another form. It is explanatory drawing of the sample analyzer which mounts the EDS detector of a prior art. It is explanatory drawing of an EDS detector.

Explanation of symbols

1000, 2000: Sample analyzer 10: EDS detector 11: Cryostat 11a: Main part 11b: Cylindrical part 11c: X-ray window 1: Pulse tube refrigerator 1a: Refrigerator main body 2: Vibratory compressor 2a: Piston 2b : Cylinder 3: Connection pipe 3a: Spring-like part 4: Expander 4a: Heat exchanger 4b: Regenerator 4c: Cooling end 4d: Pulse tube 5: Phase control part 5a: Inertance tube 5b: Buffer tank 6: Drive power supply Part 7: Operation state detection control part 13: Cold finger 14: X-ray detection element part 14a: X-ray detection element 14b: Temperature sensor 15: Moving part 15a: Guide base 15b, 15c: Guide part 15d: Guide rod 15e: Actuator 15f: guided portion 16: hermetic terminal 17: detection signal processing unit 20: electron microscope 21: electron gun unit 22: focusing lens 23: Inspection coil 24: Objective lens 25: Scanning control unit 26: CRT display unit 27: Detection unit 28: Image signal processing unit 30: Sample chamber 40: Main body 50: Connecting tube 51: Main body portion 52: Flexible portion 60: Anti-vibration Stand 70: Weight 80: Pressure conversion valve unit 90: Compressor 100: High pressure helium piping 110: Low pressure helium piping 120: Controller 130: Vibration isolation mechanism

Claims (4)

An electron microscope that obtains an image signal from the emitted electrons by irradiating the sample with an electron beam;
An EDS detector for analyzing a sample from characteristic X-rays emitted by irradiating the sample with an electron beam;
A refrigerating machine main body having a vibration type compressor having a pair of pistons opposed to each other and cooling an X-ray detection element of an EDS detector;
An operation state detection control unit that detects an operation state of whether an electron microscope or an EDS detector is operated and outputs an operation switching signal;
A drive power supply unit for controlling the drive of the refrigerator based on the operation switching signal;
With
Pre-cooling operation by raising the temperature to the allowable upper limit temperature of the X-ray detection element during operation of the electron microscope, and performing the main operation by lowering the temperature to the operating temperature of the X-ray detection element during operation of the EDS detector apparatus. The sample analyzer according to claim 1,
The refrigerator main body is
A linear motor including a piston and a drive unit that reciprocates the piston, and a cylinder in which the linear motor is housed, and the piston is reciprocated inside the cylinder to define a compression space. An oscillating compressor that periodically compresses the fluid inside;
An expander coupled to the vibratory compressor;
A phase control unit coupled to the expander;
A sample analyzer comprising: The sample analyzer according to claim 2,
The refrigerator main body is
A sample analyzer comprising a connecting pipe connected between a vibration type compressor and an expander. The sample analyzer according to claim 3,
The connecting pipe includes a string-like spring-like portion,
The sample analyzer according to claim 1, wherein a piston driving direction of the vibration type compressor and a central axis direction of the spring-like portion are arranged substantially in parallel.

Images