CN114545704B - High-pressure differential beam source air chamber and method for generating high-energy extreme ultraviolet photons by utilizing same - Google Patents

Abstract

The invention discloses a high-pressure differential beam source air chamber and a method for generating high-energy extreme ultraviolet photons by using the same. The high-voltage differential beam source gas cell of the present invention comprises: an outer plenum, an inner plenum, and a three-dimensional linear translation stage 14, the inner plenum comprising: the internal gas chamber comprises an internal gas chamber body 1, a differential cone 2, a differential cone sealing plate 3, a nickel pipe 4 and a gas chamber sealing flange 5, wherein the external gas chamber comprises an external gas chamber body, a hollow differential pipeline 6, a cavity sealing flange 9, a vacuum corrugated pipe 10 and a corrugated pipe sealing flange 11. The invention provides the concept of the differential cone for the first time, and the differential cone is used for realizing space pointing control and phase matching adjustment; the three-dimensional precise movement of the air chamber in the vacuum can be realized by directly moving the three-dimensional displacement table under the atmosphere in a mode of KF interface vacuum bellows, so that the high cost of the ultrahigh vacuum electric three-dimensional moving device is reduced while the moving range and the precision are ensured.

Description

High-pressure differential beam source air chamber and method for generating high-energy extreme ultraviolet photons by utilizing same

Technical Field

The invention relates to the technical fields of short wave extreme ultraviolet light sources, high harmonic generation and attosecond optics, in particular to a three-dimensional adjustable ultrahigh vacuum extreme ultraviolet band high-pressure differential beam source air chamber. The invention can be applied to an ultra-high vacuum extreme ultraviolet light source generation system.

Background

The generation of higher harmonics is an important mode for internationally researching the forward attosecond physics and generating an ultra-short extreme ultraviolet pulse light source, and mainly depends on the action of a femtosecond fundamental frequency light source and inert gas molecules, so that photons with higher single photon energy bands, which are integral multiples of fundamental frequency light, are generated. Wherein the gas atomic region and its gas pressure distribution have a decisive influence on the phase matching process of the generation of higher harmonics.

The current common gas target mode is to use a hollow nickel tube or a glass tube for ventilation, then to use laser to punch through, and to adjust the phase matching condition to generate higher harmonic wave. However, the nickel tube is directly arranged in the vacuum cavity, so that a great amount of gas leakage can be caused by overlarge pressure difference between the outside of the nickel tube and the inside of the nickel tube, the small hole is larger and larger due to unstable laser pointing, the vacuum degree in the vacuum cavity is reduced, the generated extreme ultraviolet photons are absorbed by background gas in the vacuum cavity, the detection efficiency is reduced, and the damage to the ultra-high vacuum environment detection instrument can be caused by improper control.

And because the inner diameter of the nickel pipe or the glass pipe is limited, the process of generating higher harmonics mainly occurs near the pipe diameter length, and a long phase matching distance cannot be realized to optimize the process of generating harmonics. Patent number: U.S. Pat. No. GUIDED WAVE METHODS AND APPARATUS FOR NONLINEAR FREQUENCY GENERATION to USOO6151155a discloses a hollow waveguide technology which can properly optimize the process, but since the inner diameter of a long-distance hollow waveguide is only in the order of hundred micrometers, laser alignment requires three-dimensional adjustment of the head and the tail or five-dimensional adjustment of the whole body, the use process is complicated, the waveguide structure is complicated, and the replacement cost after use and loss is very large compared with that of a hollow nickel tube.

Disclosure of Invention

In view of the above-mentioned problems existing in the prior art, the present invention is intended to solve the problem that the high-pressure beam source inside the chamber has an adverse effect on the vacuum degree of the ultra-high vacuum chamber portion due to the diffusion of gas molecules during the generation of the higher harmonics; and meanwhile, the phase matching degree is increased by increasing the gas action area and the gas pressure adjusting range, so that photon generation with higher energy is obtained. Therefore, the invention provides the concept of a differential cone for the first time, and the space orientation control and the phase matching are realized through the differential cone; the three-dimensional precise movement of the air chamber in the vacuum is realized by manually moving the three-dimensional displacement table under the atmosphere in a mode of KF interface vacuum bellows, so that the high cost of the ultrahigh vacuum electric three-dimensional moving device is reduced while the moving range and the precision are ensured. Compared with the hollow waveguide technology, the invention has the advantages of more convenient use and easier replacement, can effectively reduce the experiment cost and difficulty, and can provide ultraviolet photons with higher energy.

The invention provides a high-voltage differential beam source air chamber, which is characterized by comprising: an outer plenum, an inner plenum, and a three-dimensional linear translation stage, the inner plenum comprising: the internal air chamber main body, the differential cone sealing plate, the hollow nickel pipe and the air chamber sealing flange, the external air chamber comprises an external air chamber main body, a hollow differential pipeline, a cavity sealing flange, a vacuum corrugated pipe and a corrugated pipe sealing flange,

the nickel tube penetrates through the second side wall of the inner air chamber body to be communicated with an air source outside the vacuum cavity, the first side wall and the second side wall are opposite to each other, the differential cone comprises a through hole, a base plate and a cone head, the cone head is integrally formed with the base plate, the through hole penetrates through the base plate and the cone head, the through hole extends from one side to the other side, the inner air chamber body comprises two differential cones, the two differential cones are oppositely arranged at the front end and the rear end of the inner air chamber body through differential cone sealing plates, and the through holes of the two differential cones are collinear and orthogonal to the nickel tube.

In a preferred embodiment, the cavity sealing flange is connected to the first end sealing flange by means of a bellows, and the hollow pipe is connected to the air chamber body by means of a second end sealing flange.

In a further preferred embodiment, the hollow pipe has a differential pump flange interface, which is connected to a mechanical differential pump for evacuating the hollow pipe.

In another preferred implementation, the through hole has a diameter of 1.5mm and a length of 15mm.

In another preferred implementation manner, the nickel pipe welding device further comprises a vacuum end gas cutting sleeve and an atmosphere end gas cutting sleeve, wherein the vacuum end gas cutting sleeve is used for being connected with a gas supply pipeline in a gas chamber for supplying gas to the nickel pipe, and the atmosphere end gas cutting sleeve is used for being connected with a gas supply pipeline of an external gas source.

In another preferred implementation, the differential cone has the same size differential cone seal plate and different size differential cone aperture.

In another aspect, the present invention provides a method for generating high energy euv photons, comprising:

(1) Generating fundamental frequency light of 800nm by using a laser;

(2) Collimating and guiding the generated fundamental frequency light into the air chamber in claim 1, so that the incidence direction of the fundamental frequency light enters the internal air chamber along the through hole of the differential cone;

(3) And irradiating target gas in the nickel tube orthogonal to the through hole of the differential cone by using the fundamental frequency light.

In another preferred implementation, the target gas is an inert gas with some common molecular gases.

In another preferred implementation, the inert gas is Ar, ne, he, or N ₂ And (3) waiting for gas.

Technical effects

1, the invention realizes high-pressure input by adding the single pumped differential air chamber in the vacuum cavity, maintains the high vacuum degree of the vacuum cavity, and reduces the loss of gas materials and the pollution of the vacuum cavity.

2, by optimizing the aperture length and the cone shape of the differential cones on the two light passing sides of the air chamber, the invention realizes the three-level differential effect of the action area-differential air chamber-vacuum cavity, increases the action area of gas molecules and laser, and enhances the phase matching process, thereby realizing the generation of extreme ultraviolet photons with higher energy.

And 3, the pumping differential air chamber is rigidly connected with the three-dimensional translation table in the atmospheric environment through the vacuum bellows, so that the air chamber is regulated in the atmospheric environment, and the cost difficulty of laser alignment is greatly reduced.

4, the invention can realize the differential effect of the air pressure interval and different phase matching effects by replacing the differential plates of different types.

Due to the increase of the phase matching interval, the gas chamber can generate high-energy photons (180 eV) under the condition of low-pressure (10 Torr) neon, the obtained gas pressure is obviously lower than that obtained by other similar laboratory gas chambers, and the photon energy is obviously higher than that under the condition of the similar gas chambers. And the difference effect is good, so that the vacuum cavity body can still be in a high vacuum range (better than 1*E-3 Torr) under the condition that the nickel pipe is input with 500Torr, and the phase matching under the good high-pressure condition is realized.

Drawings

FIG. 1 is a schematic view of a beam source plenum according to an embodiment of the present invention.

Fig. 2 is a differential cone engineering drawing in an embodiment of the invention.

Fig. 3 is an experimental light path diagram in an embodiment of the present invention.

Fig. 4 shows a low-pressure detection of Ne, which is an actual detection chart of experiment one of the present invention.

Fig. 5 is a practical detection chart of experiment two of the present invention, he high pressure detection.

FIG. 6 is a comparative plot of the detection of experiment three of the present invention-comparative single nickel tube detection.

FIG. 7 is a comparative test result of experiment four of the present invention.

Detailed Description

The following detailed description of embodiments of the invention, given by way of example and not by way of limitation, is made with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a structure of a high-voltage differential beam source gas chamber in an ultra-high vacuum euv band in an embodiment of the present invention. The high voltage differential beam source plenum of the present invention includes an outer plenum, an inner plenum, and a three-dimensional linear translation stage 14. The figure mainly shows a flange of the inner air chamber, the outer air chamber and the three-dimensional linear translation stage. The external air chamber adopts the existing vacuum chamber, and the internal air chamber comprises an internal air chamber main body 1, a differential cone 2, a differential cone sealing plate 3, a nickel pipe air inlet end 4, an internal air chamber sealing flange 5 and a hollow differential pipeline 6.

At least one opening of the outer air chamber is provided with a vacuum end air clamping sleeve 7 and an atmosphere end air clamping sleeve 8. In the embodiment, the vacuum end gas cutting sleeve 7 and the atmosphere end gas cutting sleeve 8 are arranged on the cavity sealing flange 9 of the external air chamber. The flange is sealed by a vacuum bellows 10 and a bellows seal flange 11. The bellows seal flange 11 is secured to a three-dimensional linear translation stage 14 by a hollow tube securing clip 12 and a differential pump flange interface 13. The hollow pipe fixing clip 12 mainly plays a role in fixing the hollow pipe 6 and the three-dimensional translation stage 14. The differential pump flange interface 13 mainly plays a role in connecting the differential mechanical pump with the hollow pipeline 6

In actual use, the gas bottle is connected with the air end gas cutting sleeve 8 from the outside, the vacuum end gas cutting sleeve 7 and the air end gas cutting sleeve 8 are respectively fixed at two ends of the flange, a section of sealing tube penetrating through the flange is arranged between the vacuum end gas cutting sleeve 7 and the air end gas cutting sleeve 8, and then gas supply is realized through the flange. One end of an internal air supply pipeline inside the external cavity is connected to the vacuum end air clamping sleeve 7 in a sealing way, and the other end of the internal air supply pipeline is connected to the nickel pipe air inlet end 4. The hollow nickel pipe is fixed in the air chamber main body 1 through the nickel pipe air inlet end 4, and the nickel pipe air inlet end 4 is connected with the vacuum end gas cutting sleeve 7 through an air supply pipeline in the air chamber, so that gas delivery and pressure control from the atmosphere to the vacuum cavity and then to the nickel pipe in the action area are realized. The hollow nickel pipe extends into the inner gas chamber body 1 through one end of the inner gas chamber, and is perpendicular to the extending direction of the through hole of the differential cone (i.e., the connecting line of the through hole of the differential cone is perpendicular to the central axis of the nickel pipe).

One end (left end in the figure) of the hollow differential pipe 6 sequentially passes through the cavity sealing flange 9 (and a gap is left between the hollow differential pipe and the cavity sealing flange 9to allow the hollow differential pipe to move relative to the cavity sealing flange 9), the corrugated pipe 10 and the corrugated pipe sealing flange 11, and is connected with a mechanical pump through a differential pump flange interface 13, and the outer side of the hollow differential pipe is in sealing connection with the corrugated pipe sealing flange 11. The other end of the hollow pipeline 6 is in sealing connection with the inner air chamber main body 1 through a KF flange interface 5. The hollow pipe 6 is in sealing connection with the external air chamber through the bellows 10 and the bellows sealing flange (KF flange) 11, so that the hollow pipe 6 is hard-connected with the three-dimensional translation stage 14 through the hollow pipe fixing clip 12, and due to the existence of the bellows, the internal air chamber body 1 is in fact hard-connected with the three-dimensional translation stage and is in soft connection with the cavity sealing flange 9, thereby realizing: the collimation between the small holes of the gas chamber 1 and the differential cone 2 and the laser beam at the vacuum end under ultra-high vacuum (the vacuum degree is better than 8*E-9 Torr) can be realized by only moving the three-dimensional translation stage 14 at the atmosphere end. The hollow pipeline 6 is provided with a differential pump flange interface 13 which can be connected with a mechanical pump to carry out independent pumping, so that leakage of experimental gas into a vacuum cavity is reduced, and the overall differential effect is improved.

Fig. 2 is a detailed structure of the differential cone 2. As shown, the differential cone 2 includes a through hole, a base plate, and a cone head integrally formed with the base plate, the through hole passing through the base plate and the cone head and extending from one side to the other side, the inner gas chamber body 1 includes two differential cones 2, the two differential cones 2 are installed opposite to each other at both ends of the inner gas chamber body 1, and the through holes of the two differential cones 2 are collinear and orthogonal to the nickel pipe 4. The differential cone reduces the conduction rate of gas to the vacuum cavity through the thin and long collimation small holes and the conical structure, and then the hollow pipeline 6 is utilized to guide the gas to the mechanical pump through the inside of the hollow pipeline 6, so that the leakage to the vacuum cavity is reduced, the direction of the hollow pipeline is approximately coaxial with the direction of the nickel pipe, and therefore the gas flow direction from the nickel pipe to the hollow pipeline can be formed, the air is prevented from overflowing into the vacuum cavity, and the vacuum degree is reduced.

The following describes how the gas cell of the present invention can be used to generate high energy ultraviolet photons in conjunction with specific experiments.

The experimental light path is shown in fig. 3, and mainly comprises: the device comprises a titanium sapphire femtosecond laser amplifier 15, collimating reflecting silver mirrors 16, 17 and 18, a 500mm focal length reflecting focusing mirror 19, a harmonic generation cavity 20, an internal air chamber main body 1, a hollow pipeline 6, a three-dimensional translation stage 14, a filter 21, a grating cavity 22, an extreme ultraviolet grating 23 and an XUV detector 24.

Experimental example

Experiment one: the laser 15 outputs fundamental frequency light of 2.35mJ and 800nm, and the fundamental frequency light is collimated by the collimator lens groups 16 and 17 and irradiates the next collimator lens 18. After the laser after collimation treatment is focused by the concave reflecting silver mirror 19, the incidence direction of the laser is collimated with the small hole of the differential cone 2 on the differential air chamber main body 1 and is focused to a nickel tube in the internal air chamber, the focal length of the concave reflecting silver mirror 19 is 500mm, a hollow nickel tube is punched in the differential air chamber (the internal air chamber) and reacts with the gas in the nickel tube, the experimental air inlet pressure is 10Torr, the experimental gas is Ne gas, the 500nm Zr filter membrane 21 is subjected to 800nm filtering action, and then XUV photons generated are finally collected by the detector 24 after being split by the extreme ultraviolet grating 23, so that the photons with the high ionization energy of Ne gas can be well phase matched corresponding to the atmospheric pressure condition, but the photon with the higher energy can be obtained under the condition of low gas pressure compared with the photon with the prior reported condition under the same experimental condition due to the extension of the action area.

According to the analysis, the laser passes through the nickel pipe through the differential cone 2 fixed on the left side and the right side of the air chamber to act with gas molecules to generate higher harmonic waves, and the differential cone increases the laser acting area while reducing the gas conduction rate between the air chamber and the vacuum cavity, so that phase matching of harmonic waves is remarkably enhanced.

Experiment II: the laser 15 outputs fundamental frequency light of 2.35mJ and 800nm, the fundamental frequency light is collimated by the collimating lens groups 16, 17 and 18 and then is focused to a nickel tube in an internal air chamber by a small hole of the differential cone 2 on the differential air chamber main body 1, the focal length of the concave reflecting silver mirror 19 is 500mm, a hollow nickel tube is perforated in the differential air chamber (the internal air chamber), the laser acts with gas in the nickel tube, the experimental air inlet pressure is 150Torr, the experimental gas is He gas, the experimental gas passes through a 500nm Zr filter membrane 21 to perform 800nm filtering, and XUV photons generated after the collimation are finally collected by an XUV detector by an extreme ultraviolet grating 23, and XUV photons higher than 150eV are obtained by detection (figure 5). Compared to the case of no internal gas cell with a single nickel tube, the highest generated XUV photons of only 125eV in the experiments by the inventors were at the time of laser conditions of 2.4mJ, 800nm, and gas pressure conditions of 340Torr He (FIG. 6). As can be seen from comparison, the differential gas chamber of the present embodiment has less gas loss, higher production efficiency and higher energy value.

Experiment III: in the experimental example, under the condition that only a nickel tube is used without using an internal differential air chamber, 2.4mJ and 800nm fundamental frequency light output by a laser 15 are vertically aligned with an inner tube in the air chamber after passing through collimating lens groups 16, 17 and 18, are focused by a concave reflecting silver mirror 19, have a focal length of 500mm, directly penetrate through a hollow nickel tube and gas to act, have experimental air pressure of 340Torr, have experimental air of He gas, pass through a 500nm Zr filter membrane 21 to perform a filtering effect of 800nm, then the generated XUV photons are finally collected by an XUV detector after being split by an extreme ultraviolet grating 23, and the XUV photons higher than 125eV are detected (figure 6),

comparing experiment two and experiment three can show that the gas loss is less when the differential gas chamber is used, the production efficiency is stronger, and the energy value is higher.

Experiment IV: the laser 15 outputs fundamental frequency light of 35fs and 800nm, the fundamental frequency light is collimated by the collimating lens groups 16, 17 and 18 and then is collimated with the small holes of the differential cone 2 on the differential air chamber main body 1, the fundamental frequency light is focused to a nickel tube by the concave reflecting silver mirror 19, the focal length is 500mm, a hollow nickel tube and gas are penetrated inside the differential air chamber to act, the experimental gas is Ne gas, and the experimental gas is subjected to 800nm filtering action by the 500nm Al filter membrane 21 (different from the experimental one, two and three Zr membranes, and more injected with luminous flux in the 50-70eV interval), and XUV photons generated after the collimating effect are finally collected by the XUV detector after being split by the extreme ultraviolet grating 23. As shown in fig. 7, three columns and four rows in the figure correspond to 12 sets of experimental conditions, and each column is a harmonic spectrum signal contrast of different air pressure values (75 Torr, 150Torr, 225Torr, 300 Torr) under the same laser intensity; harmonic spectral signal contrast for different laser intensities (1.2 mJ, 1.4mJ, 1.6 mJ) at the same air pressure was performed for each line. By controlling a single variable of experimental conditions, the luminous flux optimization conditions under different conditions are obtained through comparison (figure 7)

Experiments show that the proper enhancement of the light intensity can improve the energy interval with the highest XUV efficiency, the proper increase of the air pressure can increase the light flux, but the excessive increase can increase the absorption effect to weaken the XUV signal.

Claims (9)

1. A high pressure differential beam source plenum, the plenum comprising: an outer plenum, an inner plenum, and a three-dimensional linear translation stage (14), the inner plenum comprising: an inner air chamber main body (1), a differential cone (2), a differential cone sealing plate (3), a hollow nickel pipe (4) and an air chamber sealing flange (5), wherein the outer air chamber comprises an outer air chamber main body, a hollow differential pipe (6), a cavity sealing flange (9), a vacuum corrugated pipe (10) and a corrugated pipe sealing flange (11),

the nickel tube (4) penetrates through the second side wall of the inner air chamber body (1) to be communicated with an air source outside the outer air chamber, the first side wall and the second side wall are opposite to each other, the differential cone (2) comprises a through hole, a base plate and a conical head, the conical head is integrally formed with the base plate, the through hole penetrates through the base plate and the conical head, the differential cone extends from one side to the other side, the inner air chamber body (1) comprises two differential cones (2), the two differential cones (2) are oppositely installed at the front end and the rear end of the inner air chamber body (1) through differential cone sealing plates (3), and the through holes of the two differential cones (2) are collinear and orthogonal to the nickel tube (4).

2. The high-pressure differential beam source gas chamber according to claim 1, wherein the cavity sealing flange (9) is in sealing connection with the first end sealing flange through a corrugated pipe (10), and the hollow differential pipeline (6) is in sealing connection with the gas chamber main body (1) through the second end sealing flange (5).

3. The high-pressure differential beam source plenum according to claim (1), characterized in that the hollow differential pipe (6) has a differential pump flange interface (13), the differential pump flange interface (13) being connected with a mechanical differential pump for evacuating the hollow differential pipe.

4. The high pressure differential beam source plenum of claim (1), wherein the through holes have a diameter of 1.5mm and a length of 15mm.

5. The high-pressure differential beam source gas chamber according to claim 1, further comprising a vacuum end gas cutting sleeve (7) and an atmosphere end gas cutting sleeve (8), wherein the vacuum end gas cutting sleeve (7) is used for being connected with a gas supply pipeline in the gas chamber for supplying gas to the nickel pipe in a sealing way, and the atmosphere end gas cutting sleeve (8) is used for being connected with a gas supply pipeline of an external gas source.

6. The high-pressure differential beam source plenum according to claim 1, characterized in that the differential cone (2) has differential cone seal plates (3) of the same size and differential cone apertures of different sizes.

7. A method of generating high energy extreme ultraviolet photons, said method comprising:

(1) 800nm fundamental frequency light generated by a laser;

(2) Collimating and guiding the generated fundamental frequency light into the air chamber in claim 1, so that the incidence direction of the fundamental frequency light enters the internal air chamber along the through hole of the differential cone;

(3) And irradiating target gas in the nickel tube orthogonal to the through hole of the differential cone by using the fundamental frequency light.

8. The method of claim 7, wherein the target gas is an inert gas.

9. The method of claim 8, wherein the inert gas is Ar, ne, or He.

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