CN114545704A

CN114545704A - High-voltage differential beam source gas chamber and method for generating high-energy extreme ultraviolet photons by using same

Info

Publication number: CN114545704A
Application number: CN202210167335.7A
Authority: CN
Inventors: 李铭轩; 罗嗣佐; 丁大军
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2022-02-23
Filing date: 2022-02-23
Publication date: 2022-05-27
Anticipated expiration: 2042-02-23
Also published as: CN114545704B

Abstract

The invention discloses a high-voltage difference beam source gas chamber and a method for generating high-energy extreme ultraviolet photons by using the same. The high-voltage difference beam source gas chamber comprises: an outer gas chamber, an inner gas chamber, and a three-dimensional linear translation stage 14, the inner gas chamber comprising: the air chamber comprises an internal air chamber main body 1, a differential cone 2, a differential cone sealing plate 3, a nickel tube 4 and an air chamber sealing flange 5, wherein the external air chamber comprises an external air chamber main 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 firstly proposes the concept of a differential cone, and realizes space pointing control and phase matching adjustment through the differential cone; the mode through KF interface vacuum bellows directly moves the three-dimensional displacement platform under the atmosphere can realize the three-dimensional accurate removal of air chamber in the vacuum, when guaranteeing moving range and precision, has reduced the high expense of the electronic three-dimensional mobile device of ultrahigh vacuum.

Description

High-voltage differential beam source gas chamber and method for generating high-energy extreme ultraviolet photons by using same

Technical Field

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

Background

The generation of higher harmonics is an important mode for internationally researching the leading edge attosecond physics and generating an ultra-short extreme ultraviolet pulse light source at present, and mainly depends on the action of a femtosecond fundamental frequency light source and inert gas molecules, so that photons of a higher single photon energy waveband which is integral multiple of the fundamental frequency light are generated. Wherein the gas atom action area and the gas pressure distribution thereof have a decisive influence on the phase matching process generated by the higher harmonics.

At present, the commonly used gas target mode is to use a hollow nickel tube or a glass tube for ventilation, then use laser for punching, and adjust the phase matching condition to generate higher harmonic. However, in this mode, the nickel tube is directly arranged in the vacuum cavity, and the pressure difference between the outside of the nickel tube and the inside of the nickel tube is too large, so that a large amount of gas can be leaked, and the small holes which are unstable and pointed by laser are larger and larger after long-time use, so that 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 damage to the ultrahigh vacuum environment detection instrument can be caused due to improper control.

And because the inner diameter of the nickel tube or the glass tube is limited, the process of generating higher harmonics mainly occurs near the length of the tube diameter, and no method is provided for realizing long phase matching distance to optimize the harmonic generation process. The patent number is as follows: the U.S. patent of united states patent No. us 6151155A, background metal AND APPARATUS FOR non-linear FREQUENCY GENERATION, discloses a hollow waveguide technique that can properly optimize the process, but because the inner diameter of a long-distance hollow waveguide is only of the order of hundreds of microns, laser alignment requires separate three-dimensional adjustment of the head AND the tail or five-dimensional adjustment of the whole, the use process is complicated, the structure of the waveguide is complicated, AND the replacement cost after use loss is very large compared with that of a hollow nickel tube.

Disclosure of Invention

In view of the above problems in the prior art, the present invention is intended to solve the problem that the high-voltage beam source inside the chamber has a bad influence on the vacuum degree of the ultra-high vacuum chamber due to the diffusion of gas molecules during the generation of higher harmonics; meanwhile, the phase matching degree is increased by increasing the gas action area and the gas pressure adjusting range, so that higher-energy photon generation is achieved. Therefore, the invention firstly provides the concept of the differential cone, and realizes space pointing control and phase matching through the differential cone; the mode of KF interface vacuum bellows is used for manually moving the three-dimensional displacement table under the atmosphere to realize the three-dimensional precise movement of the air chamber in vacuum, so that the high cost of the ultrahigh vacuum electric three-dimensional moving device is reduced while the moving range and 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 difference beam source gas chamber, which is characterized by comprising: external gas chamber, inside gas chamber and three-dimensional linear translation platform, inside gas chamber includes: an internal air chamber main body, a differential cone sealing plate, a hollow nickel pipe and an air chamber sealing flange, wherein 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 internal air chamber main body is arranged at the front end of the hollow differential pipeline, the hollow differential pipeline is communicated with the internal air chamber main body through a first side wall of the internal air chamber main body, the nickel pipe penetrates through a second side wall of the internal air chamber main body and is 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 conical head, the conical head and the base plate are integrally formed, the through hole penetrates through the base plate and the conical head and extends from one side to the other side, the internal air chamber main body comprises two differential cones, the two differential cones are oppositely arranged at the front end and the rear end of the internal air chamber main body through differential cone sealing plates, and the through holes of the two differential cones are collinear and orthogonal to the nickel pipe.

In a preferred implementation, the cavity sealing flange is connected with the first end sealing flange in a sealing manner through a corrugated pipe, and the hollow pipeline is connected with the air chamber main body in a sealing manner through the second end sealing flange.

In another preferred implementation, the hollow pipe has a differential pump flange interface, which is connected to a mechanical differential pump, and the differential pump is configured to evacuate the hollow pipe.

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

In another preferred implementation mode, the gas supply device further comprises a vacuum end gas clamping sleeve and an atmosphere end gas clamping sleeve, wherein the vacuum end gas clamping sleeve is used for being connected with an air supply pipeline which is used for supplying air to the nickel pipe and is arranged in the air chamber in a sealing connection mode, and the atmosphere end gas clamping sleeve is used for being connected with an air supply pipeline of an external air source.

In another preferred implementation, the differential cones have differential cone seal plates of the same size and differential cone apertures of different sizes.

In another aspect, the present invention provides a method of generating high energy extreme ultraviolet photons, the method comprising:

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

(2) collimating and directing the generated fundamental light into the gas cell as claimed in claim 1 such that the direction of incidence of the fundamental light enters the inner gas cell along the through hole of the differential cone;

(3) and irradiating the 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 and some common molecular gas.

In another preferred implementation, the inert gas is Ar, Ne, He, or N₂And the like.

Technical effects

1, the invention realizes high-pressure input by adding a differential gas chamber pumped separately 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, the invention realizes the three-stage differential effect of the action region-the differential gas chamber-the vacuum cavity by optimizing the aperture length and the cone shape of the differential cone at the two sides of the light transmission of the gas chamber, increases the action region of gas molecules and laser, enhances the phase matching process, and further realizes the generation of extreme ultraviolet photons with higher energy.

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 adjustment of the air chamber in the atmospheric environment is realized, and the cost difficulty of laser alignment is greatly reduced.

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

Due to the increase of the phase matching interval, the gas chamber can realize the generation of high-energy photons (180eV) under the condition of low-pressure (10Torr) 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 of photons under the condition of the similar gas chambers. And because the differential effect is good, the vacuum cavity can be still in a high vacuum range (better than 1 × E-3Torr) under the condition that the nickel tube is input into 500Torr, and good phase matching under the high-pressure condition is realized.

Drawings

Figure 1 is a schematic view of a beam source gas cell according to an embodiment of the present invention.

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

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

Fig. 4 shows the actual detection diagram of experiment one of the present invention, Ne low voltage detection.

Fig. 5 shows He high-pressure detection, which is an actual detection diagram of experiment two of the present invention.

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

FIG. 7 shows the comparative test results of experiment four of the present invention.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings, and the following description is only an example of the technical contents of the present invention and is not a limitation.

Fig. 1 is a schematic structural diagram of an ultra-high vacuum extreme ultraviolet band high-voltage difference beam source gas chamber in an embodiment of the present invention. The high-voltage differential beam source gas cell of the present invention comprises an outer gas cell, an inner gas cell, and a three-dimensional linear translation stage 14. The figure mainly shows an inner air chamber, a flange of an outer air chamber and a three-dimensional linear translation stage. The outside air chamber adopts current vacuum chamber, and inside air chamber contains inside air chamber main part 1, difference cone 2, difference cone closing plate 3, nickel pipe inlet end 4, inside air chamber sealing flange 5, cavity difference pipeline 6.

And a vacuum end gas clamping sleeve 7 and an atmosphere end gas clamping sleeve 8 are arranged at least one opening of the external air chamber. In this embodiment, the vacuum end gas ferrule 7 and the atmosphere end gas ferrule 8 are mounted on a 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 sealing flange 11 is fixed on a three-dimensional linear translation stage 14 through a hollow pipeline fixing clamp 12 and a differential pump flange interface 13. The hollow pipe fixing clip 12 mainly functions to fix 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 atmosphere end gas clamping sleeve 8 from the outer side, the vacuum end gas clamping sleeve 7 and the atmosphere end gas clamping sleeve 8 are respectively fixed at two ends of the flange, a section of sealing pipe penetrating through the flange is arranged between the vacuum end gas clamping sleeve and the atmosphere end gas clamping sleeve, and then the gas supply is realized by penetrating through the flange. One end of an internal air supply pipeline on the inner side of the external cavity is hermetically connected to the vacuum end gas clamping sleeve 7, and the other end of the internal air supply pipeline is connected to the nickel pipe air inlet end 4. Through nickel pipe inlet end 4 at the inside fixed cavity nickel pipe of air chamber main part 1, nickel pipe inlet end 4 passes through the inside air supply line of air chamber and connects vacuum end gas cutting ferrule 7, and then realizes the gas transmission and the pressure control of arriving the regional nickel pipe of action again from atmosphere to vacuum chamber inside. The hollow nickel tube penetrates through one end of the internal air chamber and extends into the internal air chamber main body 1, and is vertical and orthogonal to the extending direction of the through holes of the differential cone (namely, the connecting line of the through holes of the differential cone is vertical and orthogonal to the central axis of the nickel tube).

One end (left end in the figure) of the hollow differential pipeline 6 passes through the cavity sealing flange 9 (and has a gap with the cavity sealing flange 9 so as to allow the hollow differential pipeline to move relative to the cavity sealing flange 9), the corrugated pipe 10 and the corrugated pipe sealing flange 11 in sequence, and is connected with the mechanical pump through a differential pump flange interface 13, and the outer side of the hollow differential pipeline is connected with the corrugated pipe sealing flange 11 in a sealing mode. The other end of the hollow pipeline 6 is hermetically connected with the inner air chamber body 1 through a KF flange interface 5. Well hollow pipeline 6 with through bellows 10 and bellows sealing flange (KF flange) 11 and outside air chamber realization sealing connection, like this, well hollow pipeline 6 carries out the hard joint through well hollow pipeline fixed clamp 12 with three-dimensional translation platform 14, because the existence of bellows, inside air chamber main part 1 in fact with three-dimensional translation platform hard joint and with cavity sealing flange 9 soft joint to realized: the alignment between the small holes of the gas chamber 1 and the differential cone 2 and the laser beam at the vacuum end under ultrahigh vacuum (the vacuum degree is better than 8 × E-9Torr) can be realized only by 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 for independent pumping, so that the leakage of experimental gas to the vacuum cavity is reduced, and the integral differential effect is improved.

Fig. 2 shows a detailed structure of the differential cone 2. As shown in the figure, the differential cone 2 includes a through hole integrally formed with the base plate, a base plate, and a cone head, the through hole passes through the base plate and the cone head, extending from one side to the other side, the inner plenum body 1 includes two differential cones 2, the two differential cones 2 are installed at both ends of the inner plenum body 1 opposite to each other, and the through holes of the two differential cones 2 are collinear and orthogonal to the nickel tube 4. The difference cone reduces the conduction rate of gas to the vacuum cavity through the thin and long collimation small hole and the conical structure, and the hollow pipeline 6 is reused 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, and the direction of the hollow pipeline is approximately coaxial with the direction of the nickel pipe, so that 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 is a description of 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 the light path mainly includes: 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 gas chamber main body 1, a hollow pipeline 6, a three-dimensional translation stage 14, an optical filter 21, a grating cavity 22, an extreme ultraviolet grating 23 and an XUV detector 24.

Experimental examples

Experiment one: the laser 15 outputs 2.35mJ, 800nm fundamental frequency light, which is collimated by the collimator set 16, 17 and irradiated to the next collimating mirror 18. The three-dimensional translation stage is moved, so that the laser after the collimation treatment is focused by the concave reflecting silver mirror 19, the incident direction of the differential gas chamber is aligned with the small hole of the differential cone 2 on the differential gas chamber main body 1, the incident direction is focused to the nickel tube in the internal gas chamber, the focal length of the concave surface reflection silver mirror 19 is 500mm, the hollow nickel tube is perforated in the differential gas chamber (internal gas chamber) to act with the gas in the nickel tube, the experimental inlet pressure is 10Torr, the experimental gas is Ne gas, the filtering action of 800nm is carried out through the 500nm Zr filter membrane 21, the generated XUV photons are dispersed by the extreme ultraviolet grating 23 and finally collected by the detector 24, the photon reaching 180eV is obtained in the experiment (figure 4), the high ionization energy of the Ne gas usually corresponds to the large pressure condition, and the good phase matching can be realized, however, the extension of the region of action according to the invention makes it possible to obtain higher-energy photons at low gas pressures than have been reported to date under the same experimental conditions.

Analysis is carried out because the laser penetrates through the nickel tube through the differential cones 2 fixed on the left side and the right side of the air chamber to act with gas molecules so as to realize generation of higher harmonics, the differential cones reduce gas conduction rate between the air chamber and the vacuum cavity, increase a laser acting area, and obviously enhance phase matching of harmonic generation.

Experiment two: the laser 15 outputs 2.35mJ and 800nm fundamental frequency light, the fundamental frequency light is collimated with the small hole of the differential cone 2 on the differential gas chamber main body 1 after passing through the

collimating lens groups

16, 17 and 18 and is focused to the nickel tube in the internal gas chamber, the focal length of the concave reflecting silver mirror 19 is 500mm, the hollow nickel tube is punched in the differential gas chamber (internal gas chamber) to react with gas in the nickel tube, the experimental inlet air pressure is 150Torr, the experimental gas is He gas, the light is filtered at 800nm through the 500nm Zr filter membrane 21, then the generated XUV photons are split by the extreme ultraviolet grating 23 and are finally collected by the XUV detector, and XUV photons higher than 150eV are obtained by detection (figure 5). The inventors experimented with only 125eV XUV photons produced at the highest compared to the case without an internal gas cell with a single nickel tube, and then the laser conditions were 2.4mJ, 800nm and the gas pressure conditions were 340Torr He (fig. 6). The comparison shows that when the differential gas chamber of the embodiment is used, the gas loss is less, the generation efficiency is higher, and the generated energy value is higher.

Experiment three: in this experimental example, without using an internal differential gas chamber, only using a nickel tube, 2.4mJ and 800nm fundamental frequency light output by a laser 15 passes through

collimating lens groups

16, 17 and 18 and then is vertically aligned with an inner tube in the gas chamber, is focused by a concave reflective silver mirror 19 with a focal length of 500mm, directly penetrates through the hollow nickel tube and acts with gas, the experimental inlet pressure is 340Torr, the experimental gas is He, the experimental gas passes through a 500nm Zr filter membrane 21 to perform 800nm filtering, then generated XUV photons are split by an extreme ultraviolet grating 23 and finally collected by an XUV detector, detected to obtain XUV photons higher than 125eV (fig. 6),

compared with the second experiment and the third experiment, the gas loss is less when the differential gas chamber is used, the generation efficiency is higher, and the generated energy value is higher.

Experiment four: the laser 15 outputs 35fs and 800nm fundamental frequency light, the fundamental frequency light is collimated by the

collimating lens group

16, 17 and 18 and then is collimated with the small hole of the differential cone 2 on the differential gas chamber main body 1, the fundamental frequency light is focused to the nickel tube by the concave reflection silver mirror 19, the focal length is 500mm, the hollow nickel tube is penetrated in the differential gas chamber, the experimental gas is Ne gas, the experimental gas is subjected to 800nm filtering action through a 500nm Al filter membrane 21 (different from Zr membranes used in the first experiment, the second experiment and the third experiment, and the light flux in the interval of 50-70eV is further noted), and then generated XUV photons are split by the extreme ultraviolet grating 23 and finally collected by the XUV detector. As shown in fig. 7, there are a total of three columns and four rows corresponding to 12 sets of experimental conditions, each row being a comparison of harmonic spectral signals at different gas pressure values (75Torr, 150Torr, 225Torr, 300Torr) under the same laser intensity; each action is the comparison of the harmonic spectrum signals of different laser intensities (1.2mJ, 1.4mJ and 1.6mJ) under the same air pressure condition. The optimization of luminous flux under different conditions is obtained by controlling single variable of experimental conditions and comparing (figure 7)

Through experiments, the energy interval with the highest XUV efficiency can be improved by properly enhancing the light intensity, the light flux can be increased by properly increasing the air pressure, but the XUV signal is weakened by increasing the absorption effect by too high the air pressure.

Claims

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

wherein the inner plenum body (1) is mounted at the front end of the hollow differential duct (6), the hollow differential conduit (6) communicates with the inner plenum body (1) via a first side wall of the inner plenum body (1), the nickel pipe (4) penetrates through the second side wall of the inner air chamber main body (1) 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 (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 and extends from one side to the other side, the inner air chamber main 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 main body (1) through differential cone sealing plates (3), and the through holes of the two differential cones (2) are collinear and are orthogonal to the nickel pipe (4).

2. The high pressure difference beam source gas cell according to claim 1, wherein the cavity sealing flange (9) is sealingly connected with a first end sealing flange by a bellows (10), and the hollow pipe (6) is sealingly connected with the gas cell body (1) by a second end sealing flange (5).

3. The high pressure differential beam source plenum according to claim (1), wherein the hollow 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 pipe.

4. The high voltage difference beam source plenum of claim (1), wherein said through holes are 1.5mm in diameter and 15mm in length.

5. The high pressure difference beam source gas chamber according to claim 1, further comprising a vacuum end gas ferrule (7) and an atmosphere end gas ferrule (8), wherein the vacuum end gas ferrule (7) is used for connecting a gas supply pipeline in the gas chamber for supplying gas to the nickel tube in a sealing manner, and the atmosphere end gas ferrule (8) is used for connecting a gas supply pipeline of an external gas source.

6. The high voltage differential beam source gas cell according to claim 1, characterized in that the differential cones (2) have differential cone sealing plates (3) of the same size and differential cone apertures of different sizes.

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

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

8. The method of claim 1, wherein the target gas is an inert gas.

9. The method according to claim 1, wherein the inert gas is Ar, Ne or He or the like or N₂And a molecular gas is equally distributed.