CN117930501A - Dry nondestructive decontamination and film removal method for tritium-related optical element - Google Patents
Dry nondestructive decontamination and film removal method for tritium-related optical element Download PDFInfo
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- CN117930501A CN117930501A CN202410269186.4A CN202410269186A CN117930501A CN 117930501 A CN117930501 A CN 117930501A CN 202410269186 A CN202410269186 A CN 202410269186A CN 117930501 A CN117930501 A CN 117930501A
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- 230000003287 optical effect Effects 0.000 title claims abstract description 123
- YZCKVEUIGOORGS-NJFSPNSNSA-N Tritium Chemical compound [3H] YZCKVEUIGOORGS-NJFSPNSNSA-N 0.000 title claims abstract description 116
- 229910052722 tritium Inorganic materials 0.000 title claims abstract description 116
- 238000000034 method Methods 0.000 title claims abstract description 66
- 238000005202 decontamination Methods 0.000 title claims abstract description 44
- 230000003588 decontaminative effect Effects 0.000 title claims abstract description 44
- 238000005530 etching Methods 0.000 claims abstract description 77
- 238000010884 ion-beam technique Methods 0.000 claims abstract description 50
- 239000000758 substrate Substances 0.000 claims abstract description 29
- 238000004364 calculation method Methods 0.000 claims abstract description 18
- 238000002310 reflectometry Methods 0.000 claims abstract description 15
- 238000012544 monitoring process Methods 0.000 claims abstract description 8
- 238000004088 simulation Methods 0.000 claims abstract description 5
- 150000002500 ions Chemical class 0.000 claims description 30
- 239000001301 oxygen Substances 0.000 claims description 23
- 229910052760 oxygen Inorganic materials 0.000 claims description 23
- 238000011065 in-situ storage Methods 0.000 claims description 20
- -1 oxygen ions Chemical class 0.000 claims description 17
- 238000005259 measurement Methods 0.000 claims description 15
- 238000002834 transmittance Methods 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 10
- 230000001066 destructive effect Effects 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 8
- 238000011109 contamination Methods 0.000 claims description 6
- 239000005350 fused silica glass Substances 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 5
- 230000010287 polarization Effects 0.000 claims description 4
- 238000005070 sampling Methods 0.000 claims description 4
- 230000001133 acceleration Effects 0.000 claims description 3
- 238000012625 in-situ measurement Methods 0.000 claims description 3
- 239000010408 film Substances 0.000 description 113
- 239000010410 layer Substances 0.000 description 45
- 230000000694 effects Effects 0.000 description 14
- 239000000126 substance Substances 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 239000012528 membrane Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 239000003344 environmental pollutant Substances 0.000 description 5
- 231100000719 pollutant Toxicity 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 125000004430 oxygen atom Chemical group O* 0.000 description 4
- XLYOFNOQVPJJNP-PWCQTSIFSA-N Tritiated water Chemical compound [3H]O[3H] XLYOFNOQVPJJNP-PWCQTSIFSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 230000008439 repair process Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000012788 optical film Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000013589 supplement Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000010534 mechanism of action Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000000941 radioactive substance Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0006—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
- G02B1/12—Optical coatings produced by application to, or surface treatment of, optical elements by surface treatment, e.g. by irradiation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/10—Nuclear fusion reactors
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Drying Of Semiconductors (AREA)
- ing And Chemical Polishing (AREA)
Abstract
The invention belongs to the technical field of optical elements, and particularly relates to a dry nondestructive decontamination film removal method for tritium-related optical elements. According to the optical characteristic parameters such as refractive index of a film layer on the surface of an element and a substrate, a functional relation curve between the transmissivity/reflectivity of the element and the thickness of the film layer is simulated and calculated; then, utilizing a spectrophotometer light path to monitor the transmissivity/reflectivity of the optical element on line, and calculating and monitoring the thickness of the residual film layer in real time according to the relation curve of the transmissivity/reflectivity and the film layer thickness obtained by simulation calculation; decontaminating and removing the film from the optical element by adopting a reactive ion beam etching method, and stopping the reactive ion beam etching when the online monitoring shows that the film layer is completely removed; and finally, measuring and confirming the tritium pollution content on the surface of the element. The method provided by the invention is environment-friendly and tritiated-free, does not damage the element substrate, and can synchronously realize the purposes of decontamination and film removal of the element.
Description
Technical Field
The invention belongs to the technical field of optical elements, and particularly relates to a dry nondestructive decontamination film removal method for tritium-related optical elements.
Background
Operation of high power laser devices can continue to produce significant amounts of tritium contaminating the optical components. Tritium is a radioactive substance with a half-life of 12.3 years, which can lead to serious internal irradiation after being ingested by people, so that tritium pollution needs to be strictly controlled; and the expensive reusable parts need to be reused after strict tritium removal, wherein the tritium removal process of the optical element is most complex. For optical anti-reflection and other requirements, the surface of the optical element is generally coated with an optical film layer with corresponding functions; in the process of service, the film layer with stronger physical and chemical activity is easy to adsorb a large amount of tritium and organic pollutants to form a polluted film layer; the recycling of the high-value components requires the periodic unloading of the components, the removal of the film and the pollutants, and the re-coating of the components after the damage repair. Conventional wet cleaning and film removal techniques produce large amounts of tritiated water when handling tritium-related components. Liquid tritium is the most undesirable form of tritium pollution, the toxic hazard of which is far higher than that of gaseous tritium and solid tritium (the hazard of liquid tritium to human is 5 orders of magnitude higher than that of tritium gas), the current treatment difficulty of tritiated water is extremely high, and the treatment of solid tritium or gaseous tritium pollution is relatively mature.
A dry film removal technique based on inert ion beam etching is disclosed in prior art "Removal of antireflection sol-gel SiO2 coating based on Ar ion beam etching"(Xiaolong Jiang,et al.,Fusion Engineering and Design.156(2020)111578) and chinese patent CN110013999 a. The method is characterized in that the optical film layer is removed in a gas state, a small amount of solid state and other forms in a lossless manner by utilizing the kinetic energy collision effect of ions. But it also has the following disadvantages: firstly, the pure physical bombardment effect of inert ions has weak pertinence to the removal of tritium and organic pollution, and the tritium and organic pollution is difficult to be completely removed; especially when the organic pollution of the element is heavier, tritium can be chemically combined with the organic pollution to generate refractory tritium pollution, and the tritium pollution removal difficulty is further increased. Secondly, the bombardment effect of inert ions naturally presents a preferential sputtering effect, which can lead to an imbalance in the atomic proportions of the substrate material of the component; taking a common fused quartz element as an example, the inert etching can generate oxygen vacancy defects, so that the problems of reduced laser damage performance and the like are caused.
Disclosure of Invention
The invention aims to provide a dry nondestructive decontamination film removal method for tritium-related optical elements, which can not only selectively strip and remove a film layer in a gaseous form and the like to realize nondestructive film removal; the method can strengthen and remove tritium, organic matters and other pollutants adsorbed on the surfaces of the film layer and the element, supplement oxygen atoms which are missing in the substrate material, repair oxygen vacancy defects, and improve the optical properties of the element such as damage threshold and the like; meanwhile, excessive etching of the substrate is avoided, and the treatment efficiency is high.
In order to achieve the above object, the present invention provides the following technical solutions:
The invention provides a dry nondestructive decontamination and film removal method of a tritium-related optical element, which comprises a substrate and a film layer arranged on the surface of the substrate; the method comprises the following steps:
step S1: obtaining a functional relation curve of optical parameters of the tritium-related optical element and the thickness of a film layer according to Fresnel formula theory calculation, wherein the optical parameters comprise transmittance or reflectivity;
Step S2: carrying out surface etching treatment on the tritium-related optical element by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; in the process of the surface etching treatment, in-situ measuring the transmissivity or reflectivity of the tritium-related optical element, and according to the functional relation curve obtained in the step S1, monitoring the thickness of the film layer remained after the surface etching treatment in real time in situ, and stopping the reactive ion beam etching when the film layer is completely removed;
Step S3: measuring the tritium pollution content of the surface of the optical element after the film removal obtained in the step S2, and ending the film removal by decontamination when the tritium pollution content is less than or equal to the required content to obtain the optical element after the film removal by decontamination;
When the tritium pollution content is greater than the required content, carrying out surface etching treatment on the optical element obtained in the step S2 by adopting a reactive ion beam etching method, wherein reactive ions of the reactive ion beam etching are oxygen ions; and (3) finishing decontamination and film removal until the tritium pollution content of the surface of the optical element after film removal is less than or equal to the required content, and obtaining the optical element after the decontamination and film removal.
Preferably, in step S1, the theoretical calculation is a simulation calculation using TFCal software.
Preferably, in step S2, the in-situ measurement is in-situ on-line measurement using a spectrophotometer light path; the incidence angle of the optical path during in-situ on-line measurement of the spectrophotometer optical path is consistent with the incidence angle of the optical path adopted during theoretical calculation in the step S1.
Preferably, in step S2, the reactive ions of the reactive ion beam etching are generated by an ion beam generator, and the ion beam generator is a radio frequency ion source.
Preferably, the operating parameters of the rf ion source include: the screen grid voltage is 100-1200V, the acceleration grid voltage is 50-500V, and the beam current density is 0.20-1.5 mA/cm 2.
Preferably, the included angle between the ion beam current and the normal of the tritium-related optical element surface is-45 degrees to +45 degrees.
Preferably, the measurement in step S3 is a direct measurement using a tritium surface contamination level tester or an indirect measurement using a wiping sample of the surface of the optical element.
Preferably, in step S3, the indirect measurement includes the steps of: wiping and sampling the surface of the optical element after removing the film to obtain a sample to be tested; and then a liquid scintillation counter or a proportional counter is adopted to measure the tritium content of the sample to be measured.
Preferably, the material of the substrate is fused silica.
Preferably, the tritium-related optical element is a transmissive optical element or a reflective optical element.
The invention provides a dry nondestructive decontamination and film removal method of a tritium-related optical element, which comprises a substrate and a film layer arranged on the surface of the substrate; the method comprises the following steps: step S1: obtaining a functional relation curve of optical parameters of the tritium-related optical element and the thickness of a film layer according to Fresnel formula theory calculation, wherein the optical parameters comprise transmittance or reflectivity; step S2: carrying out surface etching treatment on the tritium-related optical element by adopting reactive ion beam etching, wherein reactive ions of the method of the reactive ion beam etching are oxygen ions; in the process of the surface etching treatment, the transmissivity or reflectivity of the tritium-related optical element is measured in situ, the thickness of the residual film layer after the surface etching treatment is monitored in real time in situ according to the functional relation curve of the transmissivity or reflectivity and the film layer thickness obtained in the step S1, and when the film layer is monitored to be completely removed, the reactive ion beam etching is stopped; step S3: measuring the tritium pollution content of the surface of the optical element after the film removal obtained in the step S2, and ending the film removal by decontamination when the tritium pollution content is less than or equal to the required content to obtain the optical element after the film removal by decontamination; when the tritium pollution content is greater than the required content, carrying out surface etching treatment on the optical element after film removal by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; and (3) finishing decontamination and film removal until the tritium pollution content of the surface of the optical element after film removal is less than or equal to the required content, and obtaining the optical element after the decontamination and film removal. Unlike inert etching, the reaction mechanism of the present invention includes physical bombardment and chemical reaction. On one hand, physical bombardment generated by ion kinetic energy has etching effect on the film layer; on the other hand, the chemical activity of the oxygen ions can oxidize and remove tritium, organic matters and other pollutants adsorbed on the surfaces of the film layers and the elements; the two processes are mutually coupled and promoted, the treatment efficiency is high, and the two purposes of removing the membrane layer and tritium and decontamination can be synchronously realized. In addition, oxygen ions are adopted as etching ions, and the slight injection effect of the ions on the shallow surface layer of the element in the microscopic etching process is utilized, so that oxygen atoms missing in the substrate material can be supplemented, oxygen vacancy defects can be repaired, and the optical properties such as the damage threshold value of the element and the like can be improved.
In summary, compared with the prior art, the technical scheme provided by the invention has the following advantages:
The invention adopts reactive ion beam etching, and the etching mechanism comprises two aspects of physical bombardment and chemical oxidation. Wherein, the film layer can be selectively stripped and removed in the form of gas and the like under the physical bombardment effect, so that the nondestructive film removal is realized; the chemical activity of the oxygen ions can strengthen and remove tritium, organic matters and other pollutants adsorbed on the surfaces of the film layer and the element; the two processes are mutually coupled and promoted, the treatment efficiency is high, and the two purposes of removing the membrane layer and tritium and decontamination can be synchronously realized.
The invention adopts oxygen ion etching, can supplement oxygen atoms missing in the substrate material, repair oxygen vacancy defects, improve the optical properties of element damage threshold and the like.
The film removal cut-off point is accurately judged, and excessive etching of the substrate can be avoided. The invention monitors the etching process on line, can monitor the thickness of the residual film in real time, does not need to calibrate the etching rate in advance, and has no special requirements on the consistency of the thickness of the film among different elements and the time stability of the ion beam current.
Drawings
FIG. 1 is a flow chart of a method for dry non-destructive decontamination and film removal of tritium-related optical elements provided by an embodiment of the invention;
FIG. 2 shows the transmittance at 351nm for different film thicknesses calculated in the examples of the present invention;
FIG. 3 is a graph showing the transmittance at 351nm wavelength at different etch times measured on-line in accordance with an embodiment of the present invention;
FIG. 4 is a comparison of microscopic images of the surfaces of the element before and after the film removal in example 1 of the present invention;
FIG. 5 shows the transmittance test results of the element before and after the film removal in example 1 of the present invention.
Detailed Description
The invention provides a dry nondestructive decontamination and film removal method of a tritium-related optical element, which comprises a substrate and a film layer arranged on the surface of the substrate; the method comprises the following steps:
Step S1: obtaining a functional relation curve of the transmittance or the reflectance of the tritium-related optical element and the thickness of the film according to the Fresnel formula theory calculation;
Step S2: carrying out surface etching treatment on the tritium-related optical element by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; in the process of the surface etching treatment, the transmissivity or reflectivity of the tritium-related optical element is measured in situ, the thickness of the residual film layer after the surface etching treatment is monitored in real time in situ according to the functional relation curve of the transmissivity or reflectivity and the film layer thickness obtained in the step S1, and when the film layer is monitored to be completely removed, the reactive ion beam etching is stopped;
Step S3: measuring the tritium pollution content of the surface of the optical element after the film removal obtained in the step S2, and ending the film removal by decontamination when the tritium pollution content is less than or equal to the required content to obtain the optical element after the film removal by decontamination;
When the tritium pollution content is greater than the required content, carrying out surface etching treatment on the optical element after film removal by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; and (3) finishing decontamination and film removal until the tritium pollution content of the surface of the optical element after film removal is less than or equal to the required content, and obtaining the optical element after the decontamination and film removal.
In the present invention, all preparation materials/components are commercially available products well known to those skilled in the art unless specified otherwise.
The flow chart of the dry nondestructive decontamination and film removal method for the tritium-related optical element provided by the invention is shown in fig. 1, and the dry nondestructive decontamination and film removal method for the tritium-related optical element provided by the invention is described in detail below with reference to fig. 1.
The invention provides a dry nondestructive decontamination film removal method for tritium-related optical elements. In the invention, the tritium-related optical element comprises a substrate and a film layer arranged on the surface of the substrate. The tritium-related optical element is preferably a transmissive optical element or a reflective optical element. In the invention, the material of the substrate is fused quartz. When the tritium-related optical element is preferably a transmission-type optical element, the film layer is a sol-gel chemical antireflection film. When the tritium-related optical element is preferably a reflective optical element, the film layer is a dielectric reflective film.
According to the Fresnel formula theory, the functional relation curve of the transmittance or the reflectance of the tritium-related optical element and the thickness of the film is obtained. In the present invention, the theoretical calculation is preferably a simulation calculation using TFCal software. The theoretical calculation required parameters preferably include the refractive index of the refractive index substrate of the film layer and the angle of incidence of the incident light. In a specific embodiment of the present invention, the wavelength of the incident light is 351nm, the polarization state is preferably PE polarization, and the incident angle of the incident light is 0 °.
The method comprises the steps of carrying out surface etching treatment on a tritium-related optical element by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; and in-situ measuring the transmittance or the reflectance of the tritium-related optical element in the surface etching treatment process, and monitoring the thickness of the film layer remained after the surface etching treatment in real time in situ according to the functional relation curve of the transmittance or the reflectance and the film layer thickness obtained in the step S1, and stopping the reactive ion beam etching when the film layer is completely removed.
In the present invention, the in-situ measurement is preferably in-situ on-line measurement using a spectrophotometer optical path. The incidence angle of the optical path of the spectrophotometer in-situ on-line measurement is consistent with the incidence angle adopted in theoretical calculation in the steps. The incident light of the spectrophotometer during the light path in-situ on-line measurement is consistent with the incident light adopted during theoretical calculation in the steps.
In the present invention, the reactive ions of the reactive ion beam etching are preferably generated by an ion beam generator, which is preferably a radio frequency ion source. The operating parameters of the rf ion source preferably include: the screen gate voltage is preferably 100 to 1200V, more preferably 600 to 1000V; the acceleration gate voltage is preferably 50 to 500V, more preferably 300 to 500V; the beam current density is preferably 0.20 to 1.5mA/cm 2, more preferably 0.5 to 0.9mA/cm 2. The ion beam current and the normal line of the tritium-related optical element surface have an included angle of preferably-45 degrees to +45 degrees, more preferably-30 degrees to +30 degrees,
After stopping the reactive ion beam etching, the method measures the tritium pollution content on the surface of the optical element after removing the film, which is obtained by the steps, and when the tritium pollution content is less than or equal to the required content, the optical element after removing the film is obtained; when the tritium pollution content is greater than the required content, carrying out surface etching treatment on the optical element after film removal by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; and (3) until the tritium pollution content of the surface of the optical element after the film removal is less than or equal to the required content, obtaining the optical element after the film removal.
In the present invention, the measurement is preferably performed directly using a tritium surface contamination level tester or indirectly by wiping the surface of the optical element. The indirect measurement preferably comprises the steps of: wiping and sampling the surface of the optical element after removing the film to obtain a sample to be tested; and then a liquid scintillation counter or a proportional counter is adopted to measure the tritium content of the sample to be measured.
In the present invention, the required level of tritium contamination levels is preferably-0.1 Bq/cm 2, the background level of tritium contamination levels.
The dry nondestructive decontamination and film removal method for the tritium-related optical element provided by the invention comprises the following steps: firstly, according to optical characteristic parameters such as refractive index/transmissivity of a film layer on the surface of an element and a substrate, a functional relation curve between the transmissivity/reflectivity of the element and the thickness of the film layer is simulated and calculated; then, utilizing a spectrophotometer light path to monitor the transmissivity/reflectivity of the optical element on line, and calculating and monitoring the thickness of the residual film layer in real time according to the relation curve of the transmissivity/reflectivity and the film layer thickness obtained by simulation calculation; meanwhile, the optical element is decontaminated and subjected to membrane removal treatment by adopting reactive ion beam etching, and when the online monitoring shows that the membrane layer is completely removed, the reactive ion beam etching is stopped; and finally, measuring and confirming the tritium pollution content on the surface of the element. The method provided by the invention is environment-friendly, tritiated water is not generated, the element substrate is not damaged, and the two purposes of decontamination and film removal of the element can be synchronously realized.
The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.
The following example follows the flow chart shown in fig. 1.
Example 1
The embodiment provides a dry nondestructive decontamination film removal method for tritium-related optical elements, wherein the tritium-related optical elements are transmission-type optical elements, a substrate is 430mm multiplied by 430mm caliber fused quartz, and film layers on the front surface and the rear surface are 73nm thick sol-gel chemical antireflection films. At 351nm, the refractive index of fused silica was 1.477 and the refractive index of the chemical film was 1.21.
The dry nondestructive decontamination and film removal method provided by the embodiment comprises the following specific steps:
Step S1: the functional relation curve between the transmittance of the tritium-related optical element at 351nm wavelength and the thickness of the surface film layer is calculated by inputting the substrate refractive index of 1.477, the chemical film refractive index of 1.21, the laser wavelength of 351nm, PE polarization and the incidence angle of 0 degree into TFCal software, and is shown in figure 2.
Step S2: adopting a radio frequency ion source, wherein the screen grid voltage of an ion beam is 800V, the accelerating grid voltage is 500V, the beam current density is 0.8mA/cm 2, the included angle between the beam current and the normal line of the element is 0 DEG, carrying out surface etching treatment on the tritium-related optical element, and the reactive ions of reactive ion beam etching are oxygen ions; in the surface etching treatment process, a spectrophotometer is used for measuring the transmissivity of a tritium-related optical element on line in situ by utilizing 351nm wavelength laser, the incidence angle of a light path in the spectrophotometer light path on line in situ is consistent with the incidence angle adopted in theoretical calculation in the step S1, and the thickness of the residual film layer is reversely pushed according to the relation curve of the transmissivity and the film thickness obtained in the step S1, so that the thickness of the residual film layer is monitored in real time; FIG. 3 is a graph showing the 351nm transmittance at different etching times measured on line in this example. When the in-situ monitoring shows that the film transmittance and the substrate die tend to be identical (equal), it is indicated that the film has been completely removed and the reactive ion beam etching is stopped.
Step S3: and (3) measuring the tritium pollution content of the surface of the optical element after the film removal obtained in the step (S2) by adopting a tritium surface pollution level tester based on a gas-flowing type windowless proportional counter, wherein the tritium pollution activity of the surface is reduced to the background level of-0.1 Bq/cm 2, the requirements are met, and the treatment is finished.
Fig. 4 shows the comparison of microscopic images of the surfaces of the components before and after the removal of the film in this example, and it can be seen that the film and the contaminants are effectively removed. Fig. 5 shows the results of the transmittance test of the device before and after film removal in this example, where the transmittance curves of the device areas after film removal completely overlap with the uncoated die, indicating that the film layer was completely removed. Table 1 shows the results of testing the tritium pollution content on the surfaces of the elements before and after film removal, wherein the tritium pollution content on the front and back surfaces of the elements is uniformly reduced from-1 Bq/cm 2 to-0.1 Bq/cm 2 of the background level of the testing equipment. The ultraviolet laser damage threshold (351 nm@5ns) of the optical element is raised from 9.8J/cm 2 before film removal to 11.1J/cm after film removal 2
TABLE 1 tritium contamination content measurement results on the surfaces of the elements before and after removal of the Membrane
| Component testing surface | Before removing film (Bq/cm 2) | After removing the film (Bq/cm 2) |
| Front face | 1.0 | ≤0.1 |
| Reverse side | 0.9 | ≤0.09 |
The embodiment of the invention provides a dry nondestructive film removal method based on oxygen ion reactive ion beam etching, aiming at the problems of atomic proportion imbalance and the like of an optical element substrate material caused by weak pertinence to tritium pollution removal in the existing inert film removal technology. Unlike inert etching, the mechanism of action of reactive ion beam etching involves both physical bombardment and chemical reactions. On one hand, physical bombardment generated by ion kinetic energy has etching effect on the film layer; on the other hand, the chemical activity of the oxygen ions can oxidize and remove tritium, organic matters and other pollutants adsorbed on the surfaces of the film layers and the elements; the two processes are mutually coupled and promoted, the treatment efficiency is high, and the two purposes of removing the membrane layer and tritium and decontamination can be synchronously realized. In addition, oxygen ions are adopted as etching ions, and the slight injection effect of the ions on the shallow surface layer of the element in the microscopic etching process is utilized, so that oxygen atoms missing in the substrate material can be supplemented, oxygen vacancy defects can be repaired, and the optical properties such as the damage threshold value of the element and the like can be improved.
Although the foregoing embodiments have been described in some, but not all embodiments of the invention, other embodiments may be obtained according to the present embodiments without departing from the scope of the invention.
Claims (10)
1. A tritium-related optical element dry-method nondestructive decontamination film removal method comprises a substrate and a film layer arranged on the surface of the substrate; the method is characterized by comprising the following steps of:
Step S1: obtaining a functional relation curve of optical parameters of the tritium-related optical element and the thickness of a film layer according to Fresnel formula theory calculation, wherein the optical parameters comprise transmittance or reflectivity;
Step S2: carrying out surface etching treatment on the tritium-related optical element by adopting a reactive ion beam etching method, wherein reactive ions in the reactive ion beam etching are oxygen ions; in the process of the surface etching treatment, in-situ measuring the transmissivity or reflectivity of the tritium-related optical element, and according to the functional relation curve obtained in the step S1, monitoring the thickness of the film layer remained after the surface etching treatment in real time in situ, and stopping the reactive ion beam etching when the film layer is completely removed;
step S3: measuring the tritium pollution content of the surface of the optical element after the film removal obtained in the step S2, and ending the decontamination film removal when the tritium pollution content is less than or equal to the required content;
When the tritium pollution content is greater than the required content, carrying out surface etching treatment on the optical element obtained in the step S2 by adopting a reactive ion beam etching method, wherein reactive ions of the reactive ion beam etching are oxygen ions; and (3) finishing decontamination and film removal until the tritium pollution content of the surface of the optical element after film removal is less than or equal to the required content.
2. The method for dry non-destructive decontamination and film removal of tritium-related optical components according to claim 1, wherein in step S1, the theoretical calculation is a simulation calculation using TFCal software.
3. The method for non-destructive decontamination and film removal of tritium-related optical elements by dry method according to claim 1 or 2, wherein in step S2, the in-situ measurement is in-situ on-line measurement by using a spectrophotometer light path; when the spectrophotometer optical path is measured in situ on line, the incidence angle and the polarization state of the optical path are consistent with those of the optical path adopted in theoretical calculation in the step S1.
4. The method for dry non-destructive decontamination and film removal of tritium-related optical components of claim 1, wherein in step S2, the reactive ions of the reactive ion beam etching are generated by an ion beam generator, the ion beam generator being a radio frequency ion source.
5. The method for dry non-destructive decontamination and film removal of tritium-related optical components of claim 4, wherein the operating parameters of the rf ion source include: the screen grid voltage is 100-1200V, the acceleration grid voltage is 50-500V, and the beam current density is 0.20-1.5 mA/cm 2.
6. The method for non-destructive decontamination and film removal by dry method of tritium-related optical element according to claim 5, wherein the included angle between the ion beam current and the normal of the tritium-related optical element surface is-45 degrees to +45 degrees.
7. The method for dry non-destructive decontamination and film removal of tritium-related optical elements according to claim 1, wherein in the step S3, the measurement is performed directly by using a tritium surface contamination level tester or indirectly by wiping and sampling the surface of the optical element.
8. The method for dry non-destructive decontamination of tritium-related optical components of claim 7, wherein in step S3, the indirect measurement comprises the steps of: wiping and sampling the surface of the optical element after removing the film to obtain a sample to be tested; and then a liquid scintillation counter or a proportional counter is adopted to measure the tritium content of the sample to be measured.
9. The tritium-related optical element dry nondestructive decontamination film removal method of claim 1, wherein the substrate material is fused quartz.
10. The method for non-destructive decontamination and film removal of tritium-related optical elements according to claim 1 or 9, wherein the tritium-related optical element is a transmissive optical element or a reflective optical element.
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