JP2006258313A - Pulse tube refrigerating machine and device mounted therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse tube refrigerating machine in which frequency-adjustable vibration is generated to give no influence to the vibration to be generated in the pulse tube refrigerating machine and achieve a smaller size, and to provide a device mounted with the same. <P>SOLUTION: The pulse tube refrigerating machine 1 comprises a refrigerating machine body 1a having a vibration type compressor 2 in which a pair of pistons 2a are arranged opposing each other, a frequency detecting control part 7 for detecting a regional commercial power source frequency and controlling change-over of the driving frequency of the vibration type compressor 2 corresponding to the commercial power source frequency, and a driving power source part 6 for supplying AC driving power with the changed-over driving frequency to drive the vibration type compressor 2. The device mounted the pulse tube refrigerating machine is mounted with the pulse tube refrigerating machine 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pulse tube refrigerator and a pulse tube refrigerator mounting device 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. 7 is an explanatory diagram of a sample analyzer equipped with a conventional EDS detector, and FIG. 8 is an explanatory diagram of the EDS detector. A sample analyzer 1000 ′ shown in FIG. 7 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. 8, 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 body 12a is an expander, and helium gas is supplied to the refrigeration unit body 12a from a compressor 90 (see FIG. 7), 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. 8, the cold finger 13 is formed, for example, in a substantially L shape 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 12b 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 the detected temperature signal to the controller 120 (see FIG. 7). 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.
In FIG. 7, the guide base 15 a extends in the direction of the electron microscope 20 and is attached to an attachment portion protruding 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. 7, 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. 7, 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. Furthermore, although not shown, necessary devices such as a power supply unit are housed on a vibration-proof basis.

  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 a configuration for the EDS detector 10 ′ to cope with movement in the direction of arrow F or arrow R as shown in FIGS. 7 and 8.

  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. Further, a plurality of weights 70 (for example, two in FIG. 7) 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. 7, and the analysis is started from an operation unit (not shown) of the controller 120 after the door is closed and isolated from the outside. 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, 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. Since it is 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 flexible metal flexible pipe to withstand the pressure (several MPa) of the working gas of the GM-type small gas circulation refrigerator 12. It becomes a vibration generation source having a frequency of several Hz to 10 Hz. Therefore, in order to reduce the vibration of the connecting pipe 50, it is necessary to increase the mass and increase the rigidity, which has been a heavy equipment and a large-scale device. 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.

  Therefore, the present invention has been made in view of the above-described problems, and the purpose thereof is to prevent the vibration generated by the pulse tube refrigerator from being affected and to realize downsizing. It is an object of the present invention to provide a pulse tube refrigerator capable of adjusting the frequency and a pulse tube refrigerator mounting device equipped with such a pulse tube refrigerator.

In order to solve the above problems, a pulse tube refrigerator of the invention according to claim 1 of the present invention provides:
A refrigerator main body having a vibration type compressor in which a pair of pistons are arranged opposite to each other;
A frequency detection control unit that detects a commercial power supply frequency in a region and switches and controls the drive frequency of the vibration type compressor so as to coincide with the commercial power supply frequency;
A drive power supply unit for driving the vibration type compressor by supplying AC drive power with the switched drive frequency;
It is characterized by providing.

The pulse tube refrigerator of the invention according to claim 2 of the present invention is
In the pulse tube refrigerator 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.

The pulse tube refrigerator of the invention according to claim 3 of the present invention is
In the pulse tube refrigerator according to claim 2,
The refrigerator main body is
A connecting pipe connected between the vibration type compressor and the expander is provided.

The pulse tube refrigerator of the invention according to claim 4 of the present invention is
In the pulse tube refrigerator 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.

The pulse tube refrigerator mounting device of the invention according to claim 5 of the present invention,
A pulse tube refrigerator mounting device on which the pulse tube refrigerator according to any one of claims 1 to 4 is mounted,
A signal processing unit that performs various signal processing at the same operating frequency as the commercial power supply frequency,
The commercial power supply frequency, the drive frequency, and the operating frequency are matched to reduce the influence of vibration in the signal processing unit.

Further, the pulse tube refrigerator mounting device of the invention according to claim 6 of the present invention,
A pulse tube refrigerator mounting device on which the pulse tube refrigerator according to any one of claims 1 to 4 is mounted,
A signal processing unit that performs various signal processing at a predetermined operating frequency,
The frequency detection control unit is connected to the signal processing unit, detects the commercial power supply frequency in the region, and controls the operation frequency of the signal processing unit so as to match the commercial power supply frequency. The frequency and the operating frequency are matched to reduce the influence of vibration in the signal processing unit.

Further, the pulse tube refrigerator mounting device of the invention according to claim 7 of the present invention,
A pulse tube refrigerator mounting device on which the pulse tube refrigerator according to claim 5 or 6 is mounted,
The signal processing unit has a built-in power supply noise removal unit that removes vibration noise that matches the drive frequency generated by mechanical vibration of the vibration type compressor of the pulse tube refrigerator, as well as power supply noise that vibrates at the commercial power supply frequency. In addition, various processes are performed on the signal from which power supply noise and vibration noise are removed.

  According to the present invention as described above, a pulse tube refrigerator capable of adjusting the frequency of the generated vibration, so as not to be affected by the vibration generated by the pulse tube refrigerator and to realize downsizing, and A pulse tube refrigerator mounting device equipped with such a pulse tube refrigerator can be provided.

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.
In this embodiment, a sample analyzer which is a specific example of a pulse tube refrigerator mounting device will be described.

The sample analyzer 1000 of this embodiment as shown in FIG. 1 is different from the sample analyzer 1000 ′ described with reference to FIGS. 7 and 8 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. 7 and 8, 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 1a, a drive power supply unit 6, a frequency detection control unit 7), a cold finger 13, an X-ray detection element unit 14, A moving unit 15 is provided. 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 denoted by the same reference numerals as those of the prior art described with reference to FIGS. 7 and 8, and redundant description thereof is omitted.

The pulse tube refrigerator 1 will be described.
2 and 3, the pulse tube refrigerator 1 includes a vibration type compressor 2, a connecting tube 3, an expander 4, a phase control unit 5, a drive power supply unit 6, and a frequency detection control unit 7, It can be divided into a refrigerator main body 1a composed of a circuit-type vibration compressor 2, a connecting pipe 3, an expander 4, and a phase control unit 5, a drive power supply unit 6 of a power supply system, and a frequency 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 frequency detection control unit 7 inputs a commercial power supply, detects the commercial power supply frequency, and controls the drive power supply unit 6 to generate AC drive power having the same drive frequency as the detected commercial power supply frequency. In Japan, a power supply frequency of 50 Hz is used as a commercial power supply in eastern Japan and 60 Hz in western Japan. In eastern Japan, the drive power supply unit 6 generates 50 Hz alternating current drive power, and in Western Japan generates 60 Hz alternating current drive power.
By this control, the drive power supply unit 6 outputs AC drive power having a frequency determined by the frequency detection control unit 7, and the vibration type compressor 2 vibrates the piston 2a. The vibration frequency of the piston 2a matches the drive frequency of the AC drive power, that is, the commercial power supply frequency.

  Next, the operation principle of the pulse tube refrigerator 1 will be described. When driving the pulse tube refrigerator 1, the driving power source 6 supplies AC driving power having a driving frequency that matches that of the commercial power source, so that the piston 2 a reciprocates in the cylinder 2 b of the vibration compressor 2, thereby The working gas in 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, since it changes at a substantially constant volume, no heat is generated or absorbed. 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 14 a is cooled via the cold finger 13.

  Next, the operation of the sample analyzer 1000 will be described in detail particularly from the viewpoint of vibration suppression. The frequency detection control unit 7 detects a commercial power supply frequency by inputting a commercial power supply when the apparatus is installed, and generates AC drive power having the same drive frequency as the detected commercial power supply frequency for the drive power supply unit 6. It is assumed that the control is finished as follows. In Japan, a power frequency of 50 Hz is used as a commercial power source in eastern Japan and 60 Hz in western Japan. In eastern Japan, the drive power supply unit 6 generates 50 Hz alternating current driving power, and in western Japan it generates 60 Hz alternating current driving power. It becomes.

  When the analysis is started, the electron microscope 20 and the EDS detector 10 are operated. In the EDS detector 10, the pulse tube refrigerator 1 is operated to cool the X-ray detection element 14a. At this time, since the same AC drive power as the commercial power supply frequency is supplied and the piston 2a reciprocates, mechanical vibration having the same frequency as the commercial power supply 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.

  Under such circumstances, the signal processing unit of the electron microscope 20 (which is a specific example of the signal processing unit of the present invention) emits an electron beam from the electron gun unit 21 as shown in FIG. Then, the beam 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. The scanning control unit 25 is also connected to a CRT display unit 26, and the CRT display unit 26 performs display corresponding to the scanning position. In this scanning, when the synchronizing frequency of the vertical synchronizing signal (which is a specific example of the operating frequency of the signal processing unit of the present invention) is, for example, 60 Hz, which is the same as the power supply frequency, the frequency detection control unit 7 has the same 60 Hz as the commercial power supply frequency. In order to control the drive power supply unit 6 so as to generate AC drive power with a drive frequency of 50 Hz, the synchronization frequency of the vertical synchronization signal, the power supply frequency, and the drive frequency of the AC drive power match at 60 Hz, and in particular, different frequencies to the vertical synchronization signal Therefore, it is possible to eliminate the fluctuation of the image due to the generated vibration and to obtain a clear image.

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. Although vibration noise and power supply noise resulting from mechanical vibration are superimposed on this detection signal, only the frequency (50 Hz in eastern Japan, 60 Hz in western Japan) is significantly increased in the frequency distribution. In the image signal processing unit 28 to which such a detection signal including noise is input, a power source noise removing unit (not shown) built in the image signal processing unit 28 performs processing for removing frequency components that match the power source frequency. Do. Such a power supply noise removing unit is, for example, a band pass filter or a high pass filter. Thereby, both power supply noise and vibration noise are removed. Since the image signal processing unit 28 performs image signal processing using the detection signal from which noise has been removed, a clear image can be obtained in this respect as well.
The present inventor conducted an experiment for verification, and confirmed that the sample analyzer 1000 of the present embodiment has no difference in image from the case of normal liquid nitrogen cooling stable (no bubbling state) even at a magnification of 100,000 times. did.

  Similarly, 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 unit 14a (see FIG. 2) detects characteristic X-rays and outputs an X-ray detection signal. Although vibration noise and power supply noise due to mechanical vibration are also superimposed on this X-ray detection signal, only the frequency that matches the power supply frequency (50 Hz in eastern Japan and 60 Hz in western Japan) is significantly large in frequency. In the detection signal processing unit 16 to which such a detection signal including noise is input, a power supply noise removal unit built in the detection signal processing unit 16 performs a process of removing a frequency component that matches the power supply frequency. Such a power supply noise removing unit is, for example, a band pass filter or a high pass filter. Thereby, both power supply noise and vibration noise are removed. Since the detection signal processing unit 16 performs the spectrum analysis process using the X-ray detection signal from which noise has been removed, the detection signal processing unit 16 can perform an accurate process that eliminates the influence of the generated vibration.

  The present embodiment has been described above. In this embodiment, the frequency detection control unit 7 is selected so as to match the commercial frequency of the area so that the drive frequency of the linear motor of the vibration type compressor 2 of the pulse tube refrigerator 1 can be changed. As a result, the main component of mechanical vibration is a substantially sine wave that matches the commercial power supply frequency, and vibration noise can be removed together with power supply noise during image processing of an electron microscope.

  The signal processing unit of the electron microscope 20 can be further improved. FIG. 5 is a circuit block diagram of another sample analysis circuit, FIG. 5 (a) is a circuit block diagram of an electron microscope, and FIG. 5 (b) is a circuit block diagram of an EDS detector. In this embodiment, compared with the embodiment described with reference to FIG. 4, the frequency detection control unit 7 is connected to the scan control unit 25, and the frequency detection control unit 7 inputs the commercial power supply to detect the commercial power supply frequency and scans. Control unit 25 is controlled to generate a vertical synchronization signal having the same synchronization frequency as the detected commercial power supply frequency. In Japan, a power supply frequency of 50 Hz is used as a commercial power source in eastern Japan and 60 Hz in western Japan. In eastern Japan, the scanning control unit 25 generates a vertical synchronizing signal of 50 Hz and generates a vertical synchronizing signal of 60 Hz in western Japan.

  Such a signal processing unit performs the following processing. As shown in FIG. 5A, when an electron beam is irradiated from the electron gun unit 21, it reaches the scanning coil 23 via the focusing lens 22, and its orbit is changed by the magnetic field or electric field in the scanning coil 23. 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. The scanning control unit 25 is also connected to a CRT display unit 26, and the CRT display unit 26 displays corresponding to the scanning position. Here, the frequency detection control unit 7 controls the drive power supply unit 6 so as to generate AC drive power having the same drive frequency as the commercial power supply frequency, and generates a vertical synchronization signal having the same synchronization frequency as the commercial power supply frequency. The scanning control unit 25 is controlled as described above. For this reason, in the scanning of the scanning control unit 25, the synchronizing frequency of the vertical synchronizing signal (the operating frequency of the signal processing unit of the present invention) is changed to, for example, the same as the power supply frequency (50 Hz in eastern Japan, 60 Hz in western Japan). Since the synchronization frequency, the power supply frequency, and the drive frequency of the AC drive power coincide with each other, noises of different frequencies are not mixed in the vertical synchronization signal, and the fluctuation of the image due to the generated vibration can be eliminated and a clear image can be obtained.

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. Although vibration noise and power supply noise resulting from mechanical vibration are superimposed on this detection signal, only the frequency (50 Hz in eastern Japan, 60 Hz in western Japan) is significantly increased in the frequency distribution. In the image signal processing unit 28 to which such a detection signal including noise is input, a power source noise removing unit (not shown) built in the image signal processing unit 28 performs processing for removing frequency components that match the power source frequency. Do. Such a power supply noise removing unit is, for example, a band pass filter or a high pass filter. Thereby, both power supply noise and vibration noise are removed. Since the image signal processing unit 28 performs image signal processing using the detection signal from which noise has been removed, a clear image can be obtained in this respect as well.
The inventor conducted an experiment for verification, and confirmed that there was no difference in image from the case of normal liquid nitrogen cooling when the liquid nitrogen cooling was stable (in the absence of bubbling).

  Similarly, in the EDS detector 10, as shown in FIG. 5B, when an 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 unit 14a (see FIG. 2) detects characteristic X-rays and outputs an X-ray detection signal. Although vibration noise and power supply noise due to mechanical vibration are also superimposed on this X-ray detection signal, only the frequency that matches the power supply frequency (50 Hz in eastern Japan and 60 Hz in western Japan) is significantly large in frequency. In the detection signal processing unit 16 to which such a detection signal including noise is input, a power supply noise removal unit built in the detection signal processing unit 16 performs a process of removing a frequency component that matches the power supply frequency. Such a power supply noise removing unit is, for example, a band pass filter or a high pass filter. Thereby, both power supply noise and vibration noise are removed. Since the detection signal processing unit 16 performs the spectrum analysis process using the X-ray detection signal from which noise has been removed, the detection signal processing unit 16 can perform an accurate process that eliminates the influence of the generated vibration.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 6 is an explanatory view of another type of sample analyzer. In this embodiment, a sample analyzer will be described as a specific example of the apparatus equipped with a pulse tube refrigerator. 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 in the previous embodiment and the prior art described with reference to FIGS. Description is omitted.

The vibration type compressor 2 is arranged on the main body 40 as shown in FIG. 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 detector can be cooled.

In the above, each form was demonstrated. In this embodiment, a sample analyzer, particularly an energy dispersive semiconductor X-ray detector, has been described as an example. However, the present invention is not limited to the sample analyzer, and a pulse tube refrigerator is mounted and various signal processing is performed. It can be applied to a device equipped with a pulse tube refrigerator.
Further, by optimizing the pulse tube refrigerator in the range of 50 to 60 Hz, the required refrigeration capacity may be obtained regardless of which frequency is selected.

  In the previous embodiment, the frequency detection control unit 7 automatically switches the operation frequency of the reciprocating motion of the piston in accordance with the local power supply frequency. However, the frequency detection control unit 7 includes a changeover switch (not shown). May be switched manually.

  As described above, according to the present invention, the reciprocating compressor includes a reciprocating compressor in which a pair of pistons are arranged opposite to each other, a reciprocating compressor including a heat exchanger, a regenerator, an expander including a pulse tube, and a phase controller. By providing a frequency detection control unit that switches the driving frequency of the dynamic compressor so as to coincide with the commercial power supply frequency in the region, the fundamental frequency of vibration generated by the generated force of the refrigerator can be matched with the commercial power supply frequency.

  As a result, the influence of the generated vibration can be reduced by the power noise canceling function used in the image processing of the electron microscope, so that the sample analyzer can obtain a compact and high-quality image compared with the conventional GM refrigerator system. Can be built. Further, since maintenance of the compressor oil and gas-liquid separation filter and the sliding piston of the expander, which are essential in the GM refrigerator, can be eliminated, the running cost can be reduced.

  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. FIG. 5A is a circuit block diagram of an electron microscope, and FIG. 5B 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: Frequency 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 part 16: Power supply noise removing part 17: Detection signal processing part 20: Electron microscope 21: Electron gun part 22: Focusing lens 23: Running 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 (7)

A refrigerator main body having a vibration type compressor in which a pair of pistons are arranged opposite to each other;
A frequency detection control unit that detects a commercial power supply frequency in a region and switches and controls the drive frequency of the vibration type compressor so as to coincide with the commercial power supply frequency;
A drive power supply unit for driving the vibration type compressor by supplying AC drive power with the switched drive frequency;
A pulse tube refrigerator comprising: In the pulse tube refrigerator 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 pulse tube refrigerator comprising: In the pulse tube refrigerator according to claim 2,
The refrigerator main body is
A pulse tube refrigerator comprising a connecting tube connected between a vibration type compressor and an expander. In the pulse tube refrigerator according to claim 3,
The connecting pipe includes a string-like spring-like portion,
A pulse tube refrigerator, 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. A pulse tube refrigerator mounting device on which the pulse tube refrigerator according to any one of claims 1 to 4 is mounted,
A signal processing unit that performs various signal processing at the same operating frequency as the commercial power supply frequency,
A pulse tube refrigerator mounting device characterized in that the influence of vibration in a signal processing unit is reduced by matching a commercial power supply frequency, a driving frequency, and an operating frequency. A pulse tube refrigerator mounting device on which the pulse tube refrigerator according to any one of claims 1 to 4 is mounted,
A signal processing unit that performs various signal processing at a predetermined operating frequency,
The frequency detection control unit is connected to the signal processing unit, detects the commercial power supply frequency in the region, and controls the operation frequency of the signal processing unit so as to match the commercial power supply frequency. An apparatus for mounting a pulse tube refrigerator, wherein the frequency and the operating frequency are matched to reduce the influence of vibration in the signal processing unit. A pulse tube refrigerator mounting device on which the pulse tube refrigerator according to claim 5 or 6 is mounted,
The signal processing unit has a built-in power supply noise removal unit that removes vibration noise that matches the drive frequency generated by mechanical vibration of the vibration type compressor of the pulse tube refrigerator, as well as power supply noise that vibrates at the commercial power supply frequency. And a pulse tube refrigerator mounting device that performs various types of processing on a signal from which power supply noise and vibration noise have been removed.

Images