JP2017011230A - Photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photodetector capable of joining a container and an incident window so that the interior of the container is hermetically sealed with high airtightness.SOLUTION: The photodetector comprises a container in which a detection part is stored in an internal cavity and an incident port is opened, an incident window disposed in the container covering the incident port, a first bonding material arranged in an annular shape so as to surround the incident port and joining the container and the incident window, and a second bonding material surrounding the periphery of the first bonding material and disposed in the container in an annular shape so that a shielded air gap is formed between the container and the incident window from both the interior of the container and the exterior of the container, the second bonding material sandwiching the gap together with the first bonding material. The gap is hermetically sealed by the first joining material and the second joining material so that gas does not pass through the joining portion between the container and the incident window.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photodetector that is hermetically sealed.

  Photodetectors such as X-ray detectors and infrared detectors have a structure in which a thin film-shaped entrance window through which light to be detected is transmitted is connected to a metal container (housing). In the photodetector, in order to keep the inside of the container in a vacuum state or to enclose a specific gas in the container, the inside of the container is generally hermetically sealed.

  For example, the inside of the container may be kept in a vacuum for temperature adjustment of a detection component that is mounted inside the container of the photodetector and used for light detection (see, for example, Patent Document 1). In addition, X-ray / gamma-ray detectors (proportional counter tubes) etc. fill the interior of the container with a gas such as dry nitrogen in order to suppress leakage currents in the detection components, or perform signal amplification using the ionization action of the gas. In order to carry out, the inside of a container is filled with an inert gas (for example, refer patent document 2).

Japanese Patent No. 4639794 Japanese Patent No. 4139905

  However, measures have not been sufficient for the airtightness of the joint between the container of the photodetector and the entrance window. Due to the low hermeticity of the joint, the inside of the container is insufficiently kept in a vacuum and the ability to cool the detection components deteriorates, and the signal amplification factor due to the gas enclosed in the container gradually decreases. There was a problem.

  In view of the above problems, an object of the present invention is to provide a photodetector that can join a container and an entrance window so that the inside of the container is hermetically sealed.

  According to one aspect of the present invention, (a) a detection component is housed in an internal cavity and an incident port is opened; (b) an incident window disposed on the container so as to cover the incident port; C) A first bonding material that is arranged in a ring shape so as to surround the periphery of the entrance and joins the container and the entrance window; and (d) a gap that is shielded from both inside and outside the container. A second bonding material that is arranged in a ring shape around the first bonding material so as to be configured between the container and the incident window and sandwiches a gap with the first bonding material; There is provided a photodetector in which a gap is hermetically sealed by a first bonding material and a second bonding material so that gas does not pass through a bonding portion with an incident window.

  ADVANTAGE OF THE INVENTION According to this invention, the photodetector which can join a container and an entrance window so that the inside of a container may be sealed with high airtightness can be provided.

It is a schematic diagram which shows the structure of the photodetector which concerns on the 1st Embodiment of this invention. It is a typical top view which shows the example of arrangement | positioning of the 1st joining material and 2nd joining material of the photodetector which concerns on the 1st Embodiment of this invention. It is a table | surface which shows the parameter of gas. It is a graph which shows the result of having examined the permeation leak phenomenon of He gas. It is a graph which shows the other result which examined the permeation | transmission leak phenomenon of He gas. It is a schematic diagram which shows the other structure of the photodetector which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the photodetector which concerns on the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, arrangement, etc. of components. Is not specified as follows. The embodiment of the present invention can be variously modified within the scope of the claims.

(First embodiment)
As shown in FIG. 1, the photodetector 1 according to the first embodiment of the present invention includes a container 10 in which an incident port 11 is opened, and an incident window 20 that covers the incident port 11 and is disposed in the container 10. The first joint member 30 is disposed in a ring shape so as to surround the periphery of the incident port 11, and the container is formed in a ring shape so as to surround the first joint material 30. 10 and a second bonding material 40 disposed in the area 10.

  The second bonding material 40 is formed on the outer side of the first bonding material 30 so that a gap 50 shielded from both the inside of the container 10 and the outside of the container 10 is formed between the container 10 and the incident window 20. Are arranged around the entrance 11. That is, as shown in FIG. 2, the second bonding material 40 sandwiches the gap 50 together with the first bonding material 30 from both sides. In the photodetector 1, the gap 50 is hermetically sealed by the first bonding material 30 and the second bonding material 40.

  The gap 50 is filled with a predetermined gas at a higher pressure than the outside of the container 10. The gas filled in the gap 50 is, for example, air or nitrogen gas. Thereby, the air gap 50 is hermetically sealed by the first bonding material 30 and the second bonding material 40 so that the gas does not pass through the bonding portion between the container 10 and the incident window 20. That is, as will be described in detail later, when the pressure inside the container 10 is lower than the outside, it is possible to prevent gas from entering the inside of the container 10 from the outside through the joint portion between the container 10 and the incident window 20. Is done. In addition, when the gas is sealed inside the container 10, the gas inside the container 10 is prevented from being released to the outside through the joint portion between the container 10 and the incident window 20.

  In the photodetector 1 shown in FIG. 1, the incident window 20 is installed in the container 10 so that the periphery of the incident port 11 of the container 10 and the outer edge of the incident window 20 overlap. The first bonding material 30 and the second bonding material 40 are spaced apart from each other in a facing region where the periphery of the incident port 11 and the outer edge of the incident window 20 face each other. In other words, the second bonding material 40 is arranged in a ring shape in a facing region near the outside of the container 10 outside the first bonding material 30. As described above, since the first bonding material 30 and the second bonding material 40 are doubly arranged around the entrance port 11, the upper and lower sides are sandwiched between the container 10 and the incident window 20, and the left and right sides are the first. A gap 50 is formed between the bonding material 30 and the second bonding material 40. In the example illustrated in FIG. 1, the second bonding material 40 is continuously arranged over the lower surface, the side surface, and the upper surface of the outer edge portion of the incident window 20.

  For the first bonding material 30 and the second bonding material 40, for example, a resin adhesive such as an epoxy resin or a silicone resin can be used. The container 10 and the incident window 20 are bonded by the first bonding material 30 and the second bonding material 40.

  The container 10 has a structure in which a cap 12 is placed on the main surface of a flat stem 13. The opening of the cap 12 is closed by the stem 13 and a cavity is formed in the container 10. Light L to be detected, which is incident from the incident window 20 disposed at the incident port 11 of the cap 12, is irradiated to the detection component 60 stored inside the container 10.

  For the detection component 60, for example, a light detection element that converts the energy of the irradiated light L into an electrical signal is used. Examples of the light detection element include a semiconductor element having a P-I-N junction using a semiconductor substrate, an SDD (Silicon Drift Detector) element, and the like.

  For example, in a photodetecting element having a P-I-N junction, electrons and holes are generated in the photodetecting element by the light L incident on the I layer of the photodetecting element, and are detected as current pulses outside. The semiconductor substrate constituting the light detection element is selected according to the type of light L to be detected, such as X-rays, γ-rays, ultraviolet rays, infrared rays, and visible rays. That is, a substrate made of a material that absorbs the light L and generates carriers is selected. For example, when detecting X-rays, a silicon (Si) substrate is selected. The electrical signal output from the light detection element is converted and amplified to a voltage proportional to the energy of the light L by a first-stage FET circuit (not shown) or the like, propagates through the lead wire 70, and is output as a detection signal.

  For example, when the light L is an X-ray, a beryllium (Be) film having a film thickness of about several μm to 20 μm can be used for the incident window 20. Alternatively, the entrance window 20 may be configured by attaching an organic material film or a silicon nitride film to a frame made of silicon or carbon.

  In addition, when detecting weak light by suppressing thermal noise and dark current, it is preferable to operate the detection component 60 at a low temperature of about −70 ° C. to −20 ° C., for example. For this reason, in the photodetector 1 shown in FIG. 1, the detection component 60 is mounted on the thermo module 80 arranged on the stem 13. As the thermo module 80, for example, a module in which a plurality of Peltier elements are mounted is used.

  When operating the detection component 60 at a low temperature, it is effective to keep the inside of the container 10 in a vacuum and place the detection component 60 in a vacuum environment. Thereby, the influence (heat conduction) of the heat from the outside is suppressed, and the temperature adjustment of the detection component 60 is easy.

  In addition, in an X-ray / gamma ray detector (proportional counter tube) or the like, a core wire to which a voltage is applied is used for the detection component 60, and the inside of the container 10 is dried nitrogen to suppress leakage current in the detection component 60. The container is filled with an inert gas in order to perform signal amplification using the gas ionization action. For example, a gas containing any of neon, argon, krypton, or xenon as a component is sealed in the container 10.

  As described above, the inside of the container 10 of the photodetector 1 is kept in a vacuum or a specific gas is sealed. For this reason, it is necessary to prevent the gas from entering the inside of the container 10 from the outside through the joint portion between the container 10 and the incident window 20 or the gas inside the container 10 being released from the container 10 to the outside. is there.

  As a method of joining the container 10 and the incident window 20 of the photodetector 1, (1) a method in which the container 10 and the incident window 20 are melted at a high temperature by heating means such as a laser, and (2) a method in which a solder material or a brazing material is used. (3) A method of bonding using a resin adhesive or the like is conceivable.

  However, the method (1) has the following problems. That is, the heat resistance of the incident window 20 is low depending on the material of the incident window 20, and the incident window 20 is damaged or deformed by heat generated during welding. Moreover, the thin incident window 20 may be damaged due to the difference in thermal expansion coefficient between the container 10 and the incident window 20. For example, when a metal such as stainless steel (SUS) is used for the container 10 and a Be film is used for the incident window 20, it is difficult to match the thermal expansion coefficients of the container 10 and the incident window 20.

  In the case of the method (2), there is a problem that when a thin Be film is used for the entrance window 20 in order to detect low energy X-rays, the Be film is eroded by the brazing material. Also, the solder material has poor bondability with the Be film.

  In the case of the method (3), there is a problem that an inert gas such as helium (He) gas or neon (Ne) gas permeates through the adhesive portion due to a diffusion phenomenon. For this reason, deterioration of the cooling capacity and signal amplification factor of the detection component 60 occur with the passage of time. Hereinafter, the permeation phenomenon of He gas or Ne gas will be examined.

  He gas which is an inert gas is a gas of monoatomic molecules. He has a small van der Waals radius and permeates through an adhesive such as an epoxy resin by a diffusion phenomenon. Ne also has a small van der Waals radius, which is only about 10% larger than He. Therefore, the diffusion phenomenon in which He gas and Ne gas permeate through the adhesive is larger than that of molecular gas composed of a plurality of atoms such as oxygen and nitrogen and other inert gases. FIG. 3 shows parameters of the inert gas, oxygen gas, and nitrogen gas.

  He gas and Ne gas hardly exist in the atmosphere. However, in order to prevent attenuation of weak energy radiation, the X-ray detector may be used in a He atmosphere. At this time, the surrounding He gas may enter the X-ray detector due to a diffusion phenomenon in the adhesive that joins the container of the X-ray detector and the incident window. When the detection component is constantly cooled and used, the cooling capacity may be insufficient due to the influence of a small amount of He due to the penetration of He gas having a high thermal conductivity into the container.

  In addition, in a proportional counter tube in which an inert gas such as Ne gas is enclosed, the inert gas inside is released to the outside of the container over time due to the diffusion phenomenon in the adhesive, and the signal amplification factor is deteriorated. Defects such as doing may occur.

  By the way, in Oba et al. "Reduction of helium gas permeation leakage by installing multiple O-rings" (Japan Atomic Energy Research Institute, JAERI-Tech 2001-067, October 2001), rubber O-rings are arranged in duplicate at the joints. The permeation leakage phenomenon of He gas at the joint portion due to this has been studied. According to this study, it is described that the permeation leakage phenomenon of He gas at the joint portion can be suppressed by filling pressurized air or nitrogen in the gap (gas trap) between the O-rings as shown in FIG. ing. The horizontal axis in FIG. 4 is the elapsed time, and the vertical axis is the amount of He gas permeation leakage (hereinafter the same). In FIG. 4, a characteristic S11 is a characteristic when the O-ring is single, and a characteristic S12 is a characteristic when the O-ring is doubled. Further, it is described that the permeation leakage phenomenon of He gas is further improved by filling the gap (gas trap) between the O-rings with vacuum grease as shown in FIG. In FIG. 5, characteristic S22 is a characteristic when air is filled between O-rings, and characteristic S23 is a characteristic when vacuum grease is filled between O-rings. The permeation leakage phenomenon can be suppressed in this way by filling a gas pressurized to a pressure higher than the outside between O-rings or filling a solid such as vacuum grease that does not allow the permeation of He gas. This is considered to prevent gas from permeating through the joint.

  In the photodetector 1 shown in FIG. 1, the gap 50 is hermetically sealed by the first bonding material 30 and the second bonding material 40, and the gap 50 is filled with gas at a higher pressure than the outside of the container 10. Yes. For this reason, even if the material of the 1st joining material 30 and the 2nd joining material 40 is a material which permeate | transmits gas, such as He gas which exists in the exterior of the container 10, gas invades the inside of the container 10 from the exterior. Can be suppressed. Moreover, it can also suppress that gas, such as an inert gas inside the container 10, is discharge | released outside.

  In the manufacture of the photodetector 1 shown in FIG. 1, for example, the process of curing the first bonding material 30 and the second bonding material 40 and bonding the container 10 and the incident window 20 is performed in an air atmosphere or a nitrogen atmosphere. To do. As a result, the air 50 is filled with dry air or nitrogen gas.

  Note that, as shown in FIG. 6, the gap 50 may be filled with a solid material 90 such as vacuum grease capable of maintaining an internal vacuum. By filling the gap 50 with the airtight solid material 90, it is possible to further suppress the gas from entering the inside of the container 10 from the outside and the gas inside the container 10 being released to the outside. For example, by filling the gap 50 with vacuum grease, it is possible to further suppress the passage of gas such as He gas through the gap 50.

  As described above, in the photodetector 1 according to the first embodiment of the present invention, the first bonding material 30 and the second bonding material 40 form a gap in the bonding portion between the container 10 and the incident window 20. 50. Then, the gap 50 is filled with gas at a higher pressure than the outside, or filled with a solid material 90 such as vacuum grease. Thereby, it is suppressed that gas, such as He gas, passes through the junction part of the container 10 and the entrance window 20. As a result, it is possible to provide the photodetector 1 in which the container 10 and the entrance window 20 are joined so that the inside of the container 10 is hermetically sealed. The photodetector 1 is suitably used, for example, when the inside of the container 10 is held in a vacuum or when a gas containing an inert gas as a component is sealed inside the container 10.

(Second Embodiment)
As shown in FIG. 7, the photodetector 1 according to the second embodiment of the present invention is an annular support that is disposed so that the opening 101 is positioned at a position overlapping the entrance 11 and the entrance window 20. The body 100 is further provided. The support body 100 is joined to the container 10 by the second joining material 40 outside the entrance window 20. Further, the outer edge portion of the incident window 20 and the periphery of the opening portion 101 of the support body 100 are joined by the third joining material 110. As shown in FIG. 7, the first bonding material 30 and the third bonding material 110 are respectively connected to the opposing main surfaces of the incident window 20.

  In the photodetector 1 shown in FIG. 1, the first bonding material 30 and the second bonding material 40 are both disposed between the container 10 and the incident window 20, and the periphery of the incident port 11 and the incident window 20 are arranged. A gap 50 is formed in a facing area where the outer edge faces. On the other hand, in the photodetector 1 shown in FIG. 7, the second bonding material 40 is disposed outside the incident window 20, and the first bonding material 30, the second bonding material 40, and the third bonding material 110 are used. 1 is different from FIG. 1 in that the gap 50 is surrounded. Other configurations are the same as those of the first embodiment shown in FIG. The gap 50 is filled with a gas such as air or nitrogen gas at a higher pressure than the outside of the container 10.

  For the support 100, a metal material such as SUS is preferably used. However, other materials may be used as long as they are materials that can ensure the airtightness of the air gap 50, even if they are not metal materials. For example, a material such as ceramic that is not permeable to He gas can be used for the support 100. The outer diameter of the support 100 is preferably equal to or smaller than the outer diameter of the container 10. Thereby, the enlargement of the size of the photodetector 1 can be suppressed. Further, the inner diameter of the opening 101 of the support 100 is equal to or smaller than the outer diameter of the incident window 20. Thereby, the outer edge part of the entrance window 20 and the periphery of the opening part 101 of the support body 100 can be joined by the third joining material 110.

  The photodetector 1 shown in FIG. 7 is manufactured as follows, for example. The periphery of the entrance port 11 of the container 10 and the outer edge portion of the entrance window 20 are joined by the first joining material 30. Further, the outer edge portion of the incident window 20 and the periphery of the opening portion 101 of the support body 100 are joined by the third joining material 110. In addition, these two places may be joined simultaneously. After the first bonding material 30 and the third bonding material 110 are cured, the container 10 and the support body 100 are bonded by the second bonding material 40 in a pressurized air atmosphere or a nitrogen atmosphere. The second bonding material 40 is cured to complete the photodetector 1 shown in FIG.

  Others are substantially the same as those in the first embodiment, and redundant description is omitted. For example, in the photodetector 1 shown in FIG. 7, the gap 50 may be filled with a solid material 90 such as vacuum grease.

  As described above, in the photodetector 1 according to the second embodiment of the present invention, the gap 50 is filled with a gas at a higher pressure than the outside or with a solid material 90 such as vacuum grease. Thus, the passage of a gas such as He gas through the joint portion between the container 10 and the incident window 20 is suppressed. Thereby, the photodetector 1 in which the container 10 and the entrance window 20 are joined so that the inside of the container 10 is hermetically sealed can be provided.

  As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 ... Optical detector 10 ... Container 11 ... Incident port 12 ... Cap 13 ... Stem 20 ... Incident window 30 ... 1st joining material 40 ... 2nd joining material 50 ... Air gap 60 ... Detection component 70 ... Lead wire 80 ... Thermo module 90 ... Solid material 100 ... Support body 101 ... Opening 110 ... Third bonding material

Claims (10)

A container in which a detection component is stored in an internal cavity and an entrance is opened; and
An entrance window disposed in the container covering the entrance;
A first bonding material disposed in a ring shape so as to surround the periphery of the incident port, and bonding the container and the incident window;
The container is formed in an annular shape surrounding the first bonding material so that a gap shielded from both the inside of the container and the outside of the container is formed between the container and the incident window. And a second bonding material sandwiching the gap together with the first bonding material, and the first bonding material and the second bonding material so that gas does not pass through a bonding portion between the container and the incident window. And the gap is hermetically sealed with a bonding material.   The first bonding material and the second bonding material are disposed in a double manner, spaced apart from each other in a facing region where the periphery of the incident port of the container and the outer edge of the incident window are opposed to each other. The photodetector according to claim 1, wherein the container and the incident window are bonded by a bonding material and the second bonding material. An annular support that is disposed so that an opening is located at a position overlapping the entrance and the entrance window, and is joined to the container by the second joining material outside the entrance window;
A third bonding material for bonding the outer edge of the incident window and the periphery of the opening of the support, and the gap includes the first bonding material, the second bonding material, and the third bonding material. The photodetector according to claim 1, wherein the photodetector is surrounded by a bonding material.   The photodetector according to any one of claims 1 to 3, wherein the gap is filled with a predetermined gas at a pressure higher than that of the outside of the container.   The photodetector according to any one of claims 1 to 3, wherein the gap is filled with vacuum grease.   The light according to any one of claims 1 to 5, wherein a gas containing an inert gas of any one of neon, argon, krypton, and xenon is enclosed in the inside of the container. Detector.   The photodetector according to claim 1, wherein the inside of the container is a vacuum.   The photodetector according to claim 1, wherein the incident window is a beryllium film.   8. The photodetector according to claim 1, wherein an organic material film or a silicon nitride film is used for a part of the incident window.   The photodetector according to any one of claims 1 to 9, wherein the first bonding material and the second bonding material are resin-based adhesives.

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