JPH10311879A - Energy dispersion type semiconductor x-ray detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy dispersion type semiconductor X-ray detector which allows the state of an EDS detector to be grasped at a glance from the outside after power is on. SOLUTION: In an energy distribution type semiconductor X-ray detector 3 so designed that an X-ray detecting device 16 is cooled by a small gas circulation type refrigerator 5 controlled by a controller 25, lamps 31a-31d, 32 indicating the temperature condition of the X-ray detecting element 16 are placed on the front of the controller 25 in such a way as to be turned on according to the state of change of the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray microanalyzer for measuring characteristic X-rays emitted from a sample excited by an electron beam in combination with an electron microscope, and a fluorescent X-ray analyzer by X-ray excitation. In particular, the present invention relates to an energy dispersive X-ray detector (hereinafter, referred to as an EDS detector) used in an energy dispersive elemental analyzer, and particularly to cooling an X-ray detecting element by a small gas circulation refrigerator controlled by a controller. EDS
Related to the detector.

[0002]

2. Description of the Related Art Conventionally, an EDS detector used for an energy dispersive element analyzer requiring high resolution has been known as a lithium drift type silicon semiconductor X-ray detector (S
i (Li) detector) has been widely used, but in this Si (Li) detector, when Li ions drifted inside Si move by thermal diffusion, the characteristics of the X-ray detecting element deteriorate. Therefore, there is a problem that it is necessary to constantly cool using liquid nitrogen and liquid nitrogen must be supplied, which is troublesome for daily maintenance.

On the other hand, as a substitute for the liquid nitrogen, a small gas circulation type refrigerator such as a Joule-Thomson system or a pulse tube system has been developed. This small gas circulation type refrigerator has sufficient refrigeration capacity, has no mechanical drive unit in the low-temperature generation unit, and has a very simple structure, so it has extremely low vibration and high reliability for long-time operation. It has the feature that maintenance is easy.

In the EDS detector in which the X-ray detecting element is cooled by the small gas circulation refrigerator, the power of the small gas circulation refrigerator is turned on by a controller provided separately from the EDS detector. In this case, the X-ray detection element is cooled. 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, FIG. EDS is represented as shown in Figure 4.
The detector is ready for use (measurement) about 90 minutes after the power is turned on.

[0005]

The conventional ED
In the S detector, when a power switch provided on the controller is turned on, a power-on lamp provided on a front panel of the controller is turned on, and measurement is possible when the X-ray detection element reaches a predetermined measurable temperature. Since only the lamp indicating the status was turned on, the EDS after the power was turned on
The state of the detector could not be grasped at a glance from the outside.

The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to provide an EDS detector which can grasp at a glance the state of the EDS detector after the power is turned on. is there.

[0007]

In order to achieve the above object, the present invention provides an EDS detector in which an X-ray detecting element is cooled by a small gas circulation refrigerator controlled by a controller. A lamp for displaying the temperature state of the X-ray detecting element is arranged on the front surface so as to light up in accordance with the state where the temperature changes.

[0008] For example, as shown in FIG.
When the temperature of the X-ray detection element 16 (see FIG. 3) 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 the lower right direction. The lamp is turned on according to 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 the passage of time. When the temperature is cooled to the predetermined temperature, the "READY" lamp 32 is turned on to indicate that the X-ray detecting element 16 has reached the predetermined measurable temperature state. After this state, measurement can be performed arbitrarily.

[0009]

Embodiments of the present invention will be described with reference to the drawings. 1 to 3 show one embodiment of the present invention. First, FIG. 2 shows the EDS of the present invention.
FIG. 1 shows an example of an energy dispersive elemental analyzer incorporating a detector. In this figure, reference numeral 1 denotes, for example, a scanning electron microscope which is mounted on the upper surface of a holding base 2 containing a power supply unit and the like. Reference numeral 3 denotes an EDS detector slidably attached to a predetermined position of the electron microscope 1.

The schematic structure of the EDS detector 3 will be described with reference to FIG. 3. Reference numeral 4 denotes a cryostat.
It comprises a main body portion 4a in the shape of a letter and a horizontal tubular portion 4b connected to the main body portion 4a. Reference numeral 5 denotes a pulse tube refrigerator which is a kind of a small gas circulation refrigerator provided at an upper end portion inside the main body 4a of the cryostat 4. .

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, as shown in FIG. Generates a pressure wave, which is sent to the freezing section main body 5a through the connecting pipe 11 and the flexible pipe 12 fixed along the vibration isolating stand 10 for cooling, and has a sufficient freezing capacity. In addition to having a mechanical drive unit in the low-temperature generation unit and having a simple structure, it has extremely low vibration, high reliability for long-time operation, and easy maintenance. Have Reference numeral 13 denotes a vibration-proof weight detachably attached to the flexible tube 12.

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 thereto, and is made of a material having excellent heat conductivity such as copper, and is formed in, for example, an L shape. One end side thereof is thermally connected to the cooling / heating unit 5b of the pulse tube refrigerator 5.

Reference numeral 15 denotes an X-ray detecting element provided on the distal end 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. An X-ray window 18 for transmitting X-rays 17 is formed on the front surface thereof. Also,
Reference numeral 19 denotes a temperature sensor that detects the temperature of the X-ray detection element 16.

The X-ray detecting element 16 has a thickness of, for example, 2
It is composed of a high-purity n-type Si wafer having a specific resistance of 30 kΩ · cm, which is 〜5 mm. Thus, high purity S
By using an i-wafer, 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 does not operate due to a power failure or the like and cooling due to the operation cannot be obtained. Therefore, there is no need to provide a backup power source such as a battery.

The detailed configuration of the X-ray detection element section 16 is described in detail in the March 7, 1997 filed by the present applicant.
This is described in detail in a dated patent application entitled "Energy dispersive semiconductor X-ray detector".

The whole of the EDS detector 3 is indicated by an arrow F in FIG. 3 so that the detection element 15 is moved closer to or away from a sample stage (not shown) in the electron microscope 1. It is configured to slide in a direction indicated by (forward direction) or R (retreat direction).
That is, in FIG. 2, reference numeral 20 denotes a guide base extending in the direction of the electron microscope 1. A guide rod 21 is provided inside the guide base, as shown in FIG. Guided part 2 at the bottom
2 are provided so as to be guided. Reference numeral 23 denotes a guide portion for inserting the horizontal cylindrical portion 4b of the cryostat 4 and guiding it. Reference numeral 24 denotes a linear actuator composed of a driving stepping motor or the like.

In FIG. 2, reference numeral 25 denotes a controller for controlling the cooling of the EDS detector 3 (X-ray detecting element 15) and the movement thereof forward or backward.
It is placed on the upper surface of. FIG. 1 shows this controller 2
5 shows the configuration of the front panel 25a of FIG.
Is a power lamp, which is turned on when a power switch (not shown) provided on, for example, a 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. 28
Is a lamp that lights when the refrigerator power switch 27 is turned on.

Reference numeral 29 denotes a check lamp, and the compressor 6
Blinks when the pressure of the helium gas is out of the set value. A room temperature lamp 30 is turned on when the temperature of the X-ray detecting element 16 is room temperature. Reference numeral 31 denotes a lamp for displaying the temperature state of the X-ray detection element 16, and a plurality of lamps 31a to 31d.
These lamps are arranged in a lower right state so that they are turned on in accordance with a state in which the temperature decreases.
The curve obtained by sequentially connecting the centers of 31d is almost the same as the curve obtained by folding the cooling characteristic curve shown in FIG. 4 on the horizontal axis. Reference numeral 32 denotes a "READY" lamp, which is turned on when the temperature of the X-ray detection element 16 drops and reaches a measurable temperature.

Reference numerals 33 and 34 denote switches for moving the EDS detector 3 forward and backward, respectively. While these switches 33 or 34 are depressed, the linear actuator 24 operates to activate the EDS detector 3. The vehicle moves forward or backward, and the movement state is displayed on the ramp 35 or 36. Therefore, by operating the switch 33 or 34, the detection element unit 15 with respect to the sample stage is
Can be adjusted to be optimal.

In the EDS detector 3 configured as described above, when the power switch (not shown) of the controller 25 is turned on, the power lamp 26 is turned on, and the temperature of the X-ray detecting element 16 is room temperature. Then, the room temperature lamp 30 is turned on. Then, when the refrigerator power switch 27 is kept 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 enter a predetermined operation state. . As a result, the pulse tube refrigerator 5 starts the cooling operation, and the temperature of the X-ray detector 15 provided at the tip end of the cold finger 14 decreases,
The line detecting element 16 is cooled.

The temperature of the X-ray detecting element 16 at this time is detected by a temperature sensor 19 provided near the X-ray detecting element 16, and the detected output is signal-processed by the controller 25. First, the lamp 31a is turned yellow, for example. Thereafter, each time the temperature of the X-ray detection element 16 decreases, the lamps 31b, 31c, and 31d sequentially turn yellow. Then, when the temperature of the X-ray detection element 16 is cooled to a predetermined measurable temperature, the “READY” lamp 32 is also turned on to indicate that the EDS detector 3 has reached a measurable temperature state. . After this state, measurement can be performed arbitrarily.

In this case, the "READY" lamp 32 is
If the lamp is lit in a color different from the lamps 31a to 31d, for example, green, the state in which the temperature of the X-ray detecting element 16 is in the process of lowering and the state in which a predetermined measurable temperature state is reached can be clearly distinguished. It can be displayed separately.

As will be understood from the above description, in the EDS detector 3 having the above configuration, the lamps 31a to 31d and 32 for indicating the temperature of the X-ray detecting element 16 are set to E.
Since the X-ray detection element 16 is disposed in a downward-sloping state on the front panel 25a of the controller 25 that controls the DS detector 3, the temperature of the X-ray detection element 16 is sequentially reduced from the upper left lamp 31a as the time decreases. The lamps 31b to 31d are turned on 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 how the temperature of the X-ray detection element 16 decreases with the passage of time.

The present invention is not limited to the above embodiment, but can be implemented in various modifications. For example, the arrangement of the lamps 31 b to 31 d and 32 provided on the front panel 25 a of the controller 25
It is sufficient that the device is provided so that the state of the temperature change at 6 can be grasped at a glance, and an appropriate form can be adopted.

Then, instead of the pulse tube refrigerator 5, a small gas circulation refrigerator of another system such as the Joule-Thomson system may be used.

Further, the X-ray detecting element 16 is replaced with a conventional Si (L
i) It may be composed of elements. In this case, the performance of the Si (Li) element deteriorates when the degree of vacuum of the cryostat 4 is lowered (deteriorated) at room temperature, so that the Si (Li) element is constantly exhausted by an ion pump or an exhaust pump of the electron microscope 1 (shown in the figure). Need to be evacuated periodically.

[0027]

According to the EDS detector of the present invention, a lamp for displaying the temperature state of the X-ray detecting element is arranged on the front of the controller so as to be turned on in accordance with the temperature change state. Changes in the temperature state of the X-ray detection element after power-on can be grasped at a glance,
The state of the detector can be grasped at a glance from the outside.

[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 illustrating an example of an energy dispersive elemental analyzer incorporating the EDS detector.

FIG. 3 is a 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]

Reference numeral 3 denotes an energy dispersive semiconductor X-ray detector, 5 denotes a small gas circulating refrigerator, 16 denotes an X-ray detection element, 25 denotes a controller, 31a to 31d, and 32 denotes a temperature state display lamp.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shunji Nagao 2 Higashi-cho, Kichijoin-gu, Minami-ku, Kyoto, Kyoto Inside Horiba, Ltd.

Claims (1)

[Claims] 1. An energy dispersive semiconductor X-ray detector in which an X-ray detection element is cooled by a small gas circulation refrigerator controlled by a controller, wherein a temperature state of the X-ray detection element is provided on a front surface of the controller. An energy-dispersive semiconductor X-ray detector, wherein a lamp to be displayed is arranged to be turned on in accordance with a state in which the temperature changes.