Vacuum ultraviolet light source and use method

Abstract

The invention discloses a vacuum ultraviolet light source and a use method, relates to the technical field of light sources, and aims to solve the problems of short working time and fast intensity attenuation of the conventional vacuum ultraviolet light source. The flow control module, the discharge module and the gas buffer module are connected in sequence; a vacuum gauge of the flow control module is installed on a vacuum flange, the two ends of a flange cavity are fixedly connected with the flow control unit and one end of the discharge module respectively, a vacuum pump is fixedly connected with the other end of the discharge module, and the flow control unit is externally connected with an inert gas source. A discharge tube of the discharge module is mounted in a spiral resonant cavity, two ends of the discharge tube are respectively communicated with a vacuum gauge and a vacuum pump, and the spiral resonant cavity is externally connected with a radio frequency discharge module; one end of a gas buffer area of the gas buffer module is fixedly connected with the discharge tube, the gas buffer area and the discharge tube are coaxially arranged, the window sheet is arranged at the other end of the gas buffer area, and the gas buffer area is communicated with the vacuum pump. The vacuum ultraviolet light source has the advantages of long working time and slow intensity attenuation.

Description

Technical Field

[0001] The present invention relates to the technical field of light sources, and in particular to a vacuum ultraviolet light source and a use method thereof. Background Art

[0002] Metastable krypton atoms are widely used in radioisotope dating, nonlinear spectroscopy, and diode-pumped rare gas lasers. Metastable krypton atoms are usually produced by electron collision excitation, such as radio frequency discharge excitation and microwave discharge excitation, but the excitation efficiency is only 10 –4 ~10 –3 Metastable krypton atoms are generated by photoexcitation, usually using two photons to excite the ground state krypton atoms to 4p 5 (2P° 3 / 2 )5p 2 [3 / 2] J=2 state, and then spontaneously radiates to the metastable state. There are two commonly used excitation methods: one is the non-resonant two-photon excitation scheme, which requires a 215 nm laser. The excitation efficiency depends on the square of the light intensity. There is currently a lack of continuous wave lasers with sufficient power to solve this problem.

[0003] The other is the resonant two-photon excitation scheme, which requires 123.6 nm and 819.2 nm photons. Its excitation efficiency depends mainly on the 123.6 nm light intensity. 123.6 nm vacuum ultraviolet light can be obtained in a mercury pool by four-wave mixing, or it can be generated by a free electron laser. The pulsed light generated by the four-wave mixing method excites metastable krypton atoms in a krypton pool, and the excitation efficiency can reach 23%, but its time-averaged excitation efficiency is still only about 10 –4 Continuous 123.6 nm vacuum ultraviolet light can be generated by an inert gas discharge tube. However, the intensity of the vacuum ultraviolet light output by the inert gas discharge tube will gradually decrease with the working time. This is because the transmittance of the MgF2 window in the vacuum ultraviolet band gradually decreases.

[0004] Therefore, it is necessary to provide a vacuum ultraviolet light source that can work for a long time. Summary of the invention

[0005] The object of the present invention is to provide a vacuum ultraviolet light source and a method of using the same, so as to solve the technical problem that the existing vacuum ultraviolet light source has a short working time. In order to achieve the above object, the present invention provides the following technical solutions: Provided is a vacuum ultraviolet light source, comprising a flow control module, a discharge module and a gas buffer module; The flow control module, the discharge module and the gas buffer module are connected in sequence; The flow control module includes a flow control unit, a vacuum gauge and a vacuum pump, wherein the vacuum gauge is mounted on a vacuum flange, the two ends of the flange cavity are respectively fixedly connected to the flow control unit and one end of the discharge module, the vacuum pump is fixedly connected to the other end of the discharge module through a gas outlet pipeline, and the flow control unit is externally connected to an inert gas source; The discharge module comprises a spiral resonant cavity, a discharge tube and a radio frequency discharge module. The discharge tube is installed in the spiral resonant cavity. Two ends of the discharge tube are respectively connected to the vacuum gauge and the vacuum pump. The spiral resonant cavity is externally connected to the radio frequency discharge module. The gas buffer module includes a gas buffer zone and a window. One end of the gas buffer zone is fixedly connected to the discharge tube. The gas buffer zone is coaxially arranged with the discharge tube. The window is arranged at the other end of the gas buffer zone. The gas buffer zone is connected to the vacuum pump.

[0006] Compared with the prior art, the present invention has the following beneficial effects: The vacuum ultraviolet light source provided by the present application can provide continuous vacuum ultraviolet light generated by inert gas discharge; the inert gas in the discharge tube is continuously replaced by a vacuum pump to reduce the accumulation of pollutants generated by the discharge on the window; the gas buffer zone arranged behind the vacuum pump exhaust port further reduces the accumulation of pollutants on the window. The flowing inert gas forms a pressure gradient in the discharge tube, with a higher pressure inside the discharge tube and a lower pressure behind the discharge tube. The pressure gradient increases the output of vacuum ultraviolet light and weakens the self-absorption effect of ground-state krypton atoms outside the discharge area on vacuum ultraviolet light. The vacuum ultraviolet light source provided by the present application has the advantages of long working time and slow intensity decay.

[0007] The present invention also provides a method for using a vacuum ultraviolet light source, comprising the following steps: S1: Turn on the flow control unit to allow the inert gas to enter the discharge tube and control the gas flow and flow rate; S2: Turn on the radio frequency discharge module to excite the inert gas plasma discharge, generate vacuum ultraviolet light, and use a phototube to measure the intensity of the ultraviolet light source; S3: Turn on the vacuum pump to continuously replace the inert gas in the discharge tube; S4: adjusting the gas pressure in the discharge tube through a flow control unit, and adjusting the input power of the radio frequency discharge module to improve the brightness of the vacuum ultraviolet light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 A schematic diagram of a vacuum ultraviolet light source system provided in one embodiment of the present application; Figure 2 It is a simulation of the pressure distribution of the vacuum ultraviolet light source system in the embodiment of the present application; Figure 3 This is a spectrum diagram of the output of the vacuum ultraviolet light source in the embodiment of the present application; Figure 4 The intensity of the vacuum ultraviolet light source varies with the air pressure in the embodiment of the present application; Figure 5 The intensity of the vacuum ultraviolet light source varies with the radio frequency power in the embodiment of the present application; Figure 6 This is the variation law of the vacuum ultraviolet light source intensity with working time in the embodiment of this application.

[0009] Reference numerals: 101-gas inlet, 102-flow control unit, 103-vacuum gauge, 104-vacuum pump, 105-gas outlet, 201-spiral resonant cavity, 202-discharge tube, 203-RF discharge module, 204-vacuum ultraviolet light, 301-gas buffer zone, 302-window. DETAILED DESCRIPTION

[0010] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0011] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0012] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0013] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0014] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0015] See also Figure 1 , the vacuum ultraviolet light source provided by the embodiment of the present invention comprises a flow control module, a discharge module and a gas buffer module; The flow control module, the discharge module and the gas buffer module are connected in sequence; The flow control module includes a flow control unit 102, a vacuum gauge 103 and a vacuum pump 104. The vacuum gauge 103 is installed on the vacuum flange. The two ends of the flange cavity are fixedly connected to the flow control unit 102 and one end of the discharge module respectively. The vacuum pump 104 is fixedly connected to the other end of the discharge module through a gas outlet pipeline. The flow control unit 102 is externally connected to an inert gas source. The discharge module includes a spiral resonant cavity 201, a discharge tube 202 and a radio frequency discharge module 203. The discharge tube 202 is installed in the spiral resonant cavity 201. Both ends of the discharge tube 202 are connected to the vacuum gauge 103 and the vacuum pump 104 respectively. The spiral resonant cavity 201 is externally connected to the radio frequency discharge module 203. The gas buffer module includes a gas buffer zone 301 and a window 302 . One end of the gas buffer zone 301 is fixedly connected to the discharge tube 202 . The gas buffer zone 301 and the discharge tube 202 are coaxially arranged. The window 302 is arranged at the other end of the gas buffer zone 301 . The gas buffer zone 301 is connected to the vacuum pump 104 .

[0016] When implementing: The gas of the inert gas source passes through the gas inlet 101, through the flow control module 102, and then enters the discharge tube 202 through the cavity where the vacuum gauge 103 is located. The gas will also flow out through the gas outlet 105 under the action of the vacuum pump 104. The flowing inert gas forms a pressure gradient in the discharge tube 202. The pressure inside the discharge tube 202 is higher, and the pressure behind the discharge tube 202 is lower. The pressure gradient increases the output of vacuum ultraviolet light, and at the same time weakens the self-absorption effect of ground state krypton atoms outside the discharge area on vacuum ultraviolet light.

[0017] The 123.6nm vacuum ultraviolet light output by the vacuum ultraviolet light source is measured by a vacuum ultraviolet spectrometer. The vacuum ultraviolet spectrometer uses a 3600I / mm grating and a linear array CCD. The typical sensitivity of the CCD is 80V / lx·s, and the quantum efficiency at 110–400nm is 10–20%. The discharge spectrum is measured under the conditions of a spectrometer slit width of 400μm, an aperture of F3.2, a grating angle of –4deg, an integration time of 15ms, and an average of 5 measurements. The output spectrum is as follows Figure 3 As shown, the radio frequency discharge tube 202 outputs vacuum ultraviolet light of 123.6 nm and 116.5 nm, wherein the light intensity of 123.6 nm accounts for about 95% of the total intensity of the vacuum ultraviolet light.

[0018] The krypton gas discharge is generated by a spiral resonant cavity 201 coaxially placed with the discharge tube 202. The outer diameter of the spiral resonant cavity 201 is 5.4 cm, and it consists of a 13-turn copper coil with a diameter of 3 cm and an electromagnetic shielding layer. The spectrum characteristic curve of the spiral resonant cavity 201 is measured by a spectrum analyzer and a coupler. The fundamental frequency of the spiral resonant cavity 201 is 68.4 MHz, which is consistent with the theoretical calculated value of 68.7 MHz: (1) Where D (cm) is the outer diameter of the electromagnetic shielding layer, and N is the number of turns of the coil. Formula (1) is an empirical formula when d / D is 0.55, where d is the diameter of the copper coil.

[0019] The intensity of the 123.6nm vacuum ultraviolet light output by the vacuum ultraviolet light source is mainly affected by the air pressure in the discharge tube 202 and the radio frequency power of the radio frequency discharge module 203. The flow control module is adjusted to change the pressure in the discharge tube 202, and the brightness of the vacuum ultraviolet light source under different pressures is measured to find the pressure value with the highest vacuum ultraviolet light intensity; the radio frequency discharge module 203 is adjusted to change the radio frequency input power, and the brightness of the vacuum ultraviolet light source under different powers is measured to find the radio frequency input power value with the highest vacuum ultraviolet light intensity. The influence of air pressure on the intensity of vacuum ultraviolet light is as follows: Figure 4 As shown, with the increase of gas pressure, the intensity of vacuum ultraviolet light first increases and then decreases, reaching a maximum value at 22Pa.

[0020] A 100W RF power meter is used to measure the RF power of the discharge tube 202. The influence of RF power on the intensity of 123.6nm vacuum ultraviolet light is as follows: Figure 5 As shown in the figure, with the increase of RF power, the intensity of vacuum ultraviolet light continues to increase, but gradually approaches saturation. The intensity of vacuum ultraviolet light when the RF power is 66W is 50% higher than that when the RF power is 21W.

[0021] The working parameters with the highest vacuum ultraviolet light intensity are gas pressure 22Pa and RF power 66W. Under the optimal working parameters, the long-term working characteristics of the discharge tube 202 are measured. The results are as follows: Figure 6 The operating time when the light intensity drops to half of the initial light intensity is 200 hours. After 550 hours of operation, the vacuum ultraviolet light intensity is still 30% of the initial light intensity.

[0022] The data of the change of the vacuum ultraviolet light intensity I output by the discharge tube 202 with the running time t ( Figure 6 The results ( Figure 6 dotted line) is: (2) Where I0 is the initial light intensity, and the fitting correlation coefficient R 2 =0.9989.

[0023] The decay curve of vacuum ultraviolet light intensity over time is highly consistent with the exponential model, with a time constant of τ=180 (h).

[0024] The vacuum ultraviolet light source provided by the present application can provide continuous vacuum ultraviolet light generated by inert gas discharge; the inert gas in the discharge tube is continuously replaced by a vacuum pump to reduce the accumulation of pollutants generated by the discharge on the window; the gas buffer zone arranged behind the vacuum pump exhaust port further reduces the accumulation of pollutants on the window. The flowing inert gas forms a pressure gradient in the discharge tube, with a higher pressure inside the discharge tube and a lower pressure behind the discharge tube. The pressure gradient increases the output of vacuum ultraviolet light and weakens the self-absorption effect of ground-state krypton atoms outside the discharge area on vacuum ultraviolet light. The vacuum ultraviolet light source has the advantages of long working time and slow intensity decay.

[0025] As an implementation method, the discharge tube is a quartz tube, an aluminum nitride tube, an alumina tube or a corundum tube, and the inner diameter of the discharge tube is 5-15 mm and the length is 80-300 mm.

[0026] The excitation efficiency can be improved better. The vacuum gauge 103 arranged at the front section of the discharge tube 202 realizes the detection of the gas pressure in the discharge tube 202 and provides a numerical adjustment basis for the flow control unit 102. When the discharge tube is a quartz tube, its inner diameter is selected to be 10 mm and its length is selected to be 200 mm.

[0027] As an implementation method, the window 302 is a MgF2 window.

[0028] The selected MgF2 window can better transmit vacuum ultraviolet light.

[0029] As an implementable embodiment, the gas pressure in the discharge tube is 5-100 Pa, and the RF input power of the RF discharge module is 10-100 W.

[0030] The gas pressure in the discharge tube 202 is preferably 22 Pa, and the RF input power of the RF discharge module 203 is preferably 66 W. Furthermore, the RF input can be driven by a signal generator and a power amplifier.

[0031] The selected gas pressure and RF input ensure the highest vacuum ultraviolet light intensity.

[0032] As an implementation method, the discharge tube 202 is coaxially arranged with the spiral resonant cavity 201 .

[0033] The coaxial arrangement of the discharge tube 202 and the spiral resonant cavity 201 effectively ensures the excitation efficiency.

[0034] As an implementable embodiment, the flow control unit 102 is a fine-tuning air release valve, a metering valve or a mass flow meter.

[0035] Various forms of flow control units 102 reduce the requirements of the vacuum ultraviolet light source.

[0036] Based on the vacuum ultraviolet light source, a method for using the vacuum ultraviolet light source is also provided, comprising the following steps: S1: Turn on the flow control unit to allow the inert gas to enter the discharge tube and control the gas flow and flow rate; S2: Turn on the radio frequency discharge module to excite the inert gas plasma discharge, generate vacuum ultraviolet light, and use a phototube to measure the intensity of the ultraviolet light source; S3: Turn on the vacuum pump to continuously replace the inert gas in the discharge tube; S4: adjusting the gas pressure in the discharge tube through a flow control unit, and adjusting the input power of the radio frequency discharge module to improve the brightness of the vacuum ultraviolet light source.

[0037] As an implementable method, the following steps are also included: S5: recording the relative intensity of the vacuum ultraviolet light source every 30 minutes.

[0038] By regularly detecting and recording the vacuum ultraviolet light source, the working time and intensity attenuation of the vacuum ultraviolet light source can be detected.

[0039] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0040] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A vacuum ultraviolet light source, characterized in that: It includes a flow control module, a discharge module and a gas buffer module; The flow control module, the discharge module and the gas buffer module are connected in sequence; The flow control module includes a flow control unit, a vacuum gauge and a vacuum pump, wherein the vacuum gauge is mounted on a vacuum flange, the two ends of the flange cavity are respectively fixedly connected to the flow control unit and one end of the discharge module, the vacuum pump is fixedly connected to the other end of the discharge module through a gas outlet pipeline, and the flow control unit is externally connected to an inert gas source; The discharge module comprises a spiral resonant cavity, a discharge tube and a radio frequency discharge module. The discharge tube is installed in the spiral resonant cavity. Two ends of the discharge tube are respectively connected to the vacuum gauge and the vacuum pump. The spiral resonant cavity is externally connected to the radio frequency discharge module. The gas buffer module includes a gas buffer zone and a window. One end of the gas buffer zone is fixedly connected to the discharge tube. The gas buffer zone is coaxially arranged with the discharge tube. The window is arranged at the other end of the gas buffer zone. The gas buffer zone is connected to the vacuum pump.

2. The vacuum ultraviolet light source according to claim 1, characterized in that: The discharge tube is a quartz tube, an aluminum nitride tube, an aluminum oxide tube or a corundum tube, and the inner diameter of the discharge tube is 5-15 mm and the length is 80-300 mm.

3. The vacuum ultraviolet light source according to claim 1, characterized in that: The window is a MgF2 window.

4. The vacuum ultraviolet light source according to claim 1, characterized in that: The gas pressure in the discharge tube is 5-100 Pa, and the radio frequency input power of the radio frequency discharge module is 10-100 W.

5. The vacuum ultraviolet light source according to claim 1, characterized in that: The discharge tube is coaxially arranged with the spiral resonant cavity.

6. The vacuum ultraviolet light source according to claim 1, characterized in that: The flow control unit is a fine-tuning air release valve, a metering valve or a mass flow meter.

7. A method for using the vacuum ultraviolet light source according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Turn on the flow control unit to allow the inert gas to enter the discharge tube and control the gas flow and flow rate; S2: Turn on the radio frequency discharge module to excite the inert gas plasma discharge, generate vacuum ultraviolet light, and use a phototube to measure the intensity of the ultraviolet light source; S3: Turn on the vacuum pump to continuously replace the inert gas in the discharge tube; S4: adjusting the gas pressure in the discharge tube through a flow control unit, and adjusting the input power of the radio frequency discharge module to improve the brightness of the vacuum ultraviolet light source.

8. The method for using the vacuum ultraviolet light source according to claim 7, characterized in that: The following steps are also included: S5: Record the relative intensity of the vacuum ultraviolet light source every 30 minutes.

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