JP3887066B2 - Energy dispersive semiconductor X-ray detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is, for example, an energy dispersive element analyzer such as an X-ray microanalyzer that is combined with an electron microscope and that measures characteristic X-rays excited by an electron beam and emitted from a sample, and a fluorescent X-ray analyzer by X-ray excitation. In particular, the present invention relates to an EDS detector in which an X-ray detection element is cooled by a small gas circulation refrigerator controlled by a controller.
[0002]
[Prior art]
Conventionally, lithium drift silicon semiconductor X-ray detectors (Si (Li) detectors) have been widely used as EDS detectors used in energy dispersive elemental analyzers that require high resolution. In this Si (Li) detector, when Li ions drifted inside Si move due to thermal diffusion, the characteristics of the X-ray detection element deteriorate, so it is necessary to constantly cool using liquid nitrogen, There is a problem that liquid nitrogen needs to be replenished and is troublesome for daily maintenance.
[0003]
On the other hand, small gas circulation refrigerators such as the Joule-Thomson method and the pulse tube method have been developed as an alternative to the liquid nitrogen. This small gas circulation refrigerator has sufficient refrigeration capacity, has no mechanical drive in the low temperature generating part, and has a simple structure, so it has extremely low vibration and high reliability for long-time operation. It has a feature that it is easy to maintain.
[0004]
In the EDS detector in which the X-ray detector is cooled by the small gas circulation refrigerator, the small gas circulation refrigerator is turned on by a controller provided separately from the EDS detector. The X-ray detection element is cooled by this. In this case, although the cooling characteristics of the EDS detector cooled by the small gas circulation refrigerator are slightly different depending on the shape of the EDS detector, for example, as shown in FIG. The EDS detector can be used (measured) about 90 minutes after the power is turned on.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional EDS detector, when the power switch provided in the controller is turned on, the power-on lamp provided on the front panel of the controller is turned on, and the X-ray detection element reaches a predetermined measurable temperature. since the lamp representing the measurable state was only turned on when, it was not possible to grasp the descending variation of the temperature conditions of the X-ray detecting element of a power on subsequent EDS detector from the outside.
[0006]
The present invention has been made in consideration of the above-described matters, and an object of the present invention is to provide an EDS detector that can grasp the state of the EDS detector after power-on at a glance from the outside.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in the EDS detector in which the X-ray detection element is cooled by a small gas circulation refrigerator controlled by the controller, the small gas circulation refrigerator is disposed in front of the controller. A lamp that is turned on when the refrigerator power switch for turning on / off the machine power switch is turned on and a plurality of lamps that indicate the temperature drop state of the X-ray detection element are provided. The lamps are arranged so that the lamps are sequentially lit downward from the upper lamp in accordance with a state in which the temperature of the X-ray detection element is lowered with time , and the X-ray detection element reaches a predetermined temperature. A lamp that is turned on when cooled and indicates that the X-ray detection element has reached a predetermined measurable temperature state is provided at the lowest position of the plurality of lamps. It is characterized in that.
[0008]
Since the plurality of lamps for displaying the temperature decrease state of the X-ray detection element are arranged in the right-down state as shown in FIG. 1, for example, the temperature of the X-ray detection element 16 (see FIG. 3) is changed over time. As it decreases with time, the lamps are sequentially turned on from the upper left lamp 31a in the lower right direction, and the lamps are turned on in accordance with the cooling state of the X-ray detection element 16. That is, it is possible to grasp at a glance from the outside that the temperature of the X-ray detection element 16 is decreasing with time. When the temperature is cooled to a predetermined temperature, the “READY” lamp 32 is turned on to indicate that the X-ray detection element 16 has reached a predetermined measurable temperature state. After this state, measurement can be performed arbitrarily.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention will be described with reference to the drawings. 1 to 3 show an embodiment of the present invention. First, FIG. 2 shows an example of an energy dispersive element analyzer incorporating the EDS detector of the present invention. In this figure, reference numeral 1 is a scanning electron microscope, for example, a holding base containing a power supply unit and the like. 2 is placed on the upper surface. An EDS detector 3 is slidably attached to a predetermined position of the electron microscope 1.
[0010]
The schematic configuration of the EDS detector 3 will be described with reference to FIG. 3 as well. 4 is a cryostat, which is composed of an L-shaped main body 4a and a horizontal cylindrical portion 4b connected to the main body 4a. It is shut off and kept in a vacuum. Reference numeral 5 denotes a pulse tube refrigerator which is a kind of a small gas circulation refrigerator provided at the upper end of the main body 4a of the cryostat 4. A cooling part 5b extends from the freezer main body 5a to the inside of the cryostat 4. .
[0011]
As shown in FIG. 2, the pulse tube refrigerator 5 supplies high pressure and low pressure helium gas produced by a compressor 6 to a pressure conversion valve 9 through a high pressure helium pipe 7 and a low pressure pipe 8, thereby A wave is generated and sent to the freezing unit main body 5a through the connecting pipe 11 and the flexible pipe 12 fixed so as to follow the anti-vibration stand 10, and has sufficient refrigerating capacity. The low temperature generator does not have a mechanical drive and has a simple structure, so it has extremely low vibration, high reliability for long-time operation, and easy maintenance. is there. Reference numeral 13 denotes a vibration isolating weight that is detachably attached to the flexible tube 12.
[0012]
Reference numeral 14 denotes a cold finger provided in a space extending over the main body portion 4a of the cryostat 4 and the horizontal cylindrical portion 4b connected to the main body portion 4a. The cold finger 14 is made of a material having excellent thermal conductivity such as copper, and is formed in an L shape, for example. The one end side is thermally coupled to the cooling unit 5b of the pulse tube refrigerator 5.
[0013]
Reference numeral 15 denotes an X-ray detection element portion provided on the tip side of the cold finger 14 in a state of being thermally coupled thereto. Reference numeral 16 denotes an X-ray detection element which is a main component of the X-ray detection element section 15, and an X-ray window 18 for transmitting the X-ray 17 is formed on the front surface thereof. Reference numeral 19 denotes a temperature sensor that detects the temperature of the X-ray detection element 16.
[0014]
The X-ray detection element 16 is composed of a high-purity n-type Si wafer having a thickness of 2 to 5 mm and a specific resistance of 30 kΩ · cm, for example. By using a high-purity Si wafer in this way, a detection element having an intrinsic region with a sufficient thickness can be obtained without performing Li drift. The X-ray detection element 16 made of a high-purity Si wafer has a characteristic deterioration even if the pulse tube refrigerator 5 becomes inoperable due to a power failure or the like so that the cooling cannot be obtained and the temperature becomes high in a vacuum. Therefore, it is not necessary to provide a backup power source such as a battery.
[0015]
The detailed configuration of the X-ray detection element unit 15 is described in detail in the patent application “Energy dispersive semiconductor X-ray detector” dated March 7, 1997, which was filed by the applicant of this application. .
[0016]
Then, the EDS detector 3 as a whole is shown by an arrow F (forward direction) in FIG. 3 so that the detection element unit 15 approaches or moves away from a sample stage (not shown) in the electron microscope 1. ) Or R (retracting direction). That is, in FIG. 2, reference numeral 20 denotes a guide base extending in the direction of the electron microscope 1. Inside the guide base, as shown in FIG. 3, a guide rod 21 is provided. The bottom guided portion 22 is provided to be guided. Reference numeral 23 denotes a guide portion for inserting and guiding the horizontal cylindrical portion 4b of the cryostat 4. Reference numeral 24 denotes a linear actuator composed of a driving stepping motor or the like.
[0017]
In FIG. 2, reference numeral 25 denotes a controller for controlling the cooling of the EDS detector 3 (X-ray detection element 16 ) and its movement forward or backward, and is placed on the upper surface of the holding base 2. FIG. 1 shows a configuration of the front panel 25a of the controller 25. Reference numeral 26 denotes a power lamp which lights up when a power switch (not shown) provided on, for example, the rear panel of the controller 25 is turned on. Reference numeral 27 denotes a refrigerator power switch for turning on / off the power of the pulse tube refrigerator 5. Reference numeral 28 denotes a lamp that is turned on when the refrigerator power switch 27 is turned on.
[0018]
A check lamp 29 blinks when the pressure of the helium gas in the compressor 6 deviates from a set value. A room temperature lamp 30 is lit when the temperature of the X-ray detection element 16 is room temperature. Reference numeral 31 denotes a lamp that displays a state in which the temperature of the X-ray detection element 16 is decreasing , and a plurality of lamps 31a to 31d are arranged in a right-down state so that the lamps 31a to 31d are lit in accordance with the state in which the temperature of the X-ray detection element 16 decreases. Thus, the curve obtained by sequentially connecting the centers of these lamps 31a to 31d is substantially the same as the result of folding the cooling characteristic curve shown in FIG. 4 with reference to the horizontal axis. Reference numeral 32 denotes a “READY” lamp which is lit when the temperature of the X-ray detection element 16 decreases and reaches a measurable temperature.
[0019]
Reference numerals 33 and 34 denote switches for moving the EDS detector 3 forward and backward, respectively. While the switch 33 or 34 is being pressed, the linear actuator 24 operates to move the EDS detector 3 forward or backward. Then, the movement status is displayed on the lamp 35 or 36. Therefore, by operating the switch 33 or 34, the position of the detection element unit 15 with respect to the sample stage can be adjusted to be optimum.
[0020]
In the EDS detector 3 configured as described above, when a power switch (not shown) in the controller 25 is turned on, the power lamp 26 is turned on, and when the temperature of the X-ray detection element 16 is room temperature, The lamp 30 is turned on. When the refrigerator power switch 27 is continuously pressed for a predetermined time (for example, about 3 seconds), the motor of the compressor 6 and the motor of the valve unit 7 are turned on, and the compressor 6 and the valve unit 7 are in a predetermined operation state. . As a result, the pulse tube refrigerator 5 starts a cooling operation, the temperature of the X-ray detection unit 15 provided on the tip side of the cold finger 14 is lowered, and the X-ray detection element 16 is cooled.
[0021]
Then, the temperature of the X-ray detection element 16 at this time is detected by a temperature sensor 19 provided in the vicinity thereof, and this detection output is signal-processed by the controller 25. First, the lamp 31a is lit yellow, for example. Thereafter, each time the temperature of the X-ray detection element 16 decreases, the lamps 31b, 31c, and 31d are sequentially lit in yellow. When the temperature of the X-ray detection element 16 is cooled down to a predetermined measurable temperature, the “READY” lamp 32 is also turned on, indicating that the EDS detector 3 has reached a measurable temperature state. . After this state, measurement can be performed arbitrarily.
[0022]
In this case, if the “READY” lamp 32 is lit in a color different from that of the lamps 31a to 31d, for example, green, the temperature of the X-ray detection element 16 is in the process of decreasing, and a predetermined measurable temperature. It is possible to display clearly distinguishing the state from the state.
[0023]
As understood from the above description, in the EDS detector 3 having the above-described configuration, the lamps 31 a to 31 d and 32 for displaying the temperature of the X-ray detection element 16 are provided by the controller 25 that controls the EDS detector 3. Since the front panel 25a is arranged in a right-down state, as the temperature of the X-ray detection element 16 decreases as time elapses, the lamps 31b to 31d are turned on sequentially from the upper left lamp 31a to the lower right direction. The lamp is turned on in accordance with the cooling state of the X-ray detection element 16. That is, it is possible to grasp at a glance how the temperature of the X-ray detection element 16 decreases with time.
[0024]
The present invention is not limited to the above-described embodiment, and can be implemented with various modifications .
[0025]
For example , instead of the pulse tube refrigerator 5, other types of small gas circulation refrigerators such as Joule-Thomson method may be used.
[0026]
Further, the X-ray detection element 16 may be constituted by a conventional Si (Li) element. In this case, since the performance of the Si (Li) element deteriorates when the vacuum degree of the cryostat 4 is lowered (becomes worse) at room temperature, the evacuation pump of the electron microscope 1 (not shown) It is necessary to exhaust regularly.
[0027]
【The invention's effect】
Above In this EDS detector of the present invention, a plurality of lamps for displaying the lowered position of the temperature of the X-ray detection elements on the front of the controller, in accordance with the state of the temperature of the X-ray detection element is lowered with the passage of time Since the lamps are arranged so that the lamps are lit in the downward direction sequentially, the change in the temperature drop state of the X-ray detection element after power-on can be grasped at a glance, and the state of the EDS detector is externally Can be grasped at a glance.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of a configuration of a front panel of a controller of an EDS detector according to the present invention.
FIG. 2 is a diagram showing an example of an energy dispersive element analyzer incorporating the EDS detector.
FIG. 3 is a cross-sectional view schematically showing a configuration of a main part of the EDS detector.
FIG. 4 is a diagram showing cooling characteristics of an EDS detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Energy dispersive type | mold semiconductor X-ray detector, 5 ... Small gas circulation refrigerator, 16 ... X-ray detection element, 25 ... Controller, 31a-31d, 32 ... Temperature state display lamp.

Claims (1)

In an energy dispersive semiconductor X-ray detector that cools an X-ray detection element by a small gas circulation refrigerator controlled by a controller, a power switch of the small gas circulation refrigerator is turned on in front of the controller There are provided a lamp that is turned on when a refrigerator power switch for turning on / off is turned on and a plurality of lamps that indicate a temperature drop state of the X-ray detection element. The lamps are arranged so that the lamps are lit in the downward direction sequentially from the upper lamps in accordance with the state where the temperature is lowered with time, and the lamps are lit when the X-ray detection element is cooled to a predetermined temperature. the X-ray detecting elements, characterized in that the lamp to indicate that reaches a predetermined measurable temperature state are provided at the lowest position of the plurality of lamps Te Energy dispersive semiconductor X-ray detector.

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